Difference among ERW, SSAW, LSAW

What is a ERW pipe?

ERW pipe (also called ERW steel pipe) is the abbreviation Electric Resistance Welded Pipes. Electric resistance welding refers to a group of welding process (including spot and seam welding) that produce coalescence of faying surfaces where heat to form the weld is generated by the electrical resistance of material combined with the time and the force used to hold the materials together during welding. ERW steel pipes and tube are available in various qualities, wall thicknesses, and diameters of the finished pipes.

Specification of ERW steel pipe Production Process for ERW steel pipe
What is a SSAW steel pipe Standard and Classfication of SSAW Steel Pipe
Production process of SSAW steel pipe What is a LSAW pipe
SSAW pipe Manufacturing Process Difference among ERW, SSAW, LSAW

Specification of ERW steel pipe:

Pipe Type: ERW Pipe, ERW Steel Pipe, Electric Resistance Welded Pipe
Application: For Low Pressure Fluid Transmission, Machinery Manufacturing
Specification: 

  • OD: 21.3mm ~ 660mm
  • WT: 1mm ~ 17.5mm

LENGTH: 0.5mtr ~ 22mtr (5.8/6/11.8/12 meters, SRL, DRL)
Standard & Grade: ASTM A53, Grade A/B/C, Stainless steel, Alloy steel
End: Square Ends/Plain Ends (straight cut, saw cut, torch cut), Beveled/Threaded Ends

Surface: Bare, Lightly Oiled, Black/Red/Yellow Painting, Zinc/Anti-corrosive Coating

Packing: Bundled/In Bulk, Plastic Caps Plugged, Waterproof Paper Wrapped

Grade A/B/C Chemical Composition


Symbol
Chemical composition
C max Si max  Mn max  P max  S max
Grade A 0.14 0.04 0.90  0.035 0.040 
Grade B 0.17 0.04 0.90  0.035 0.040 
Grade C 0.24 0.04 0.90  0.035 0.040 

Grade A/B/C Mechanical Properties

Symbol Yield point min MPa Tensile strength MPa Elongation in 2 in.(50mm)%
Grade A 165 310-450 30 min
Grade B 185 345-450 28 min
Grade C 205 380-515 25 min
Small Diameter ERW Steel Pipe
Outside Diameter  Wall Thickness  Outside Diameter  Wall Thickness 
外径 (mm) 壁厚 (mm) 外径 (mm) 壁厚 (mm)
33.4
(1″)
2.1-2.4 Φ133        3.0-5.75
2.5-3.25 6.0-7.75
3.5-4.0 8.0-10
42.3
(1.2″)
2.1-2.4 Φ139.7
(5″)    
3.0-4.5
2.5-3.5 4.75-5.75
3.75 6.0-7.75
4.0-5.0 8.0-10
48.3
(1.5″)
2.1-2.4 Φ152  3.0-4.5
2.5-3.25 4.75-5.75
3.5-3.75 6.0-7.75
4.0-4.25 8.0-10.0
4.5-6.0 Φ159    3.25-6.75
Φ60.3 
(2″)           
3.0-4.0 6.8-7.75
4.25-4.75 8.0-10.0
5.0-5.75 10.0-11.75
Ф73 3.0-4.75 Φ165            3.0-6.0
4.8-5.25 6.25-7.0
5.5-7.0 /
Φ76.1
(2.5″)       
3.0-4.0 /
4.25-4.75 Φ168.3 3.5-5.75
5.0-5.25 6.0-8
5.5-7.0 8.25-8.75
Φ88.9
(3″)        
3.0-4.0 9.0-9.75
4.25-4.75 10.0-11.75
5.0-5.25 /
5.5-6.0 Φ177.8 
(Φ180)        
3.75-5.75
8 6.0-7.75
Φ108           3.0-4.5 8.0-8.75
4.75-5.75 9.0-9.75
6.0-6.25 10.0-11.75
6.5-9.0 /
Φ114.3
(4”)
3.0-4.0 Φ193.7
        
4.0-6.75
4.25-4.75 6.8-7.75
5.0-6.0 8.0-9.75
6.25-7.75 10.0-11.75
8.0-10 /
Φ127        3.0-4.75 Φ203               3.0-6.75
5.0-5.75 6.8-8.0
/ 8.25-11.75
/ /
HOT EXPANDED ERW STEEL PIPE
Outside Diameter Wall Thickness  Outside Diameter  Wall Thickness 
外径 (mm) 壁厚 (mm) 外径 (mm) 壁厚 (mm)
245, 273 5.0-9.28 450, 457, 508, 530 6.5-11.98
9.45-9.98 12.0-14.5
10.0-11.78 15.0-17.8
299 5.0-9.28 18.0-20.0
9.45-9.98 560, 610, 630 6.5-11.98
10.0-11.78 12.0-14.5
325 5.5-9.28 15.0-17.8
9.48-10.48 18.0-20.0
10.58-11.78 660 7.5-11.98
351, 355, 377 5.5-11.98 12.0-14.5
12.0-15 15
15.5-16 720, 820 8.5
402, 406, 426 5.5-11.98 12.0-14.5
12.0-14.5 15.0-19.98
15.5-16 18.0-20.0
Hot Rolled ERW Steel Pipe
Outside Diameter  Wall Thickness  Outside Diameter  Wall Thickness 
外径 (mm) 壁厚 (mm) 外径 (mm) 壁厚 (mm)
219245 5.0-11.75 462 5.75-11.75
273 5.0-11.75 12.5-13.75
12.5-13.75 457478 5.75-11.75
299 5.5-11.75 12.5-13.75
12.5-13.75 14.5-17.75
325 5.5-11.75 508 5.75-11.75
12.5-13.75 12.5-13.75
355 5.5-11.75 14.5-17.75
12.5-13.75 529/559/610/630 5.75-11.75
377 5.75-11.75 12.5-13.75
12.5-13.75 14.5-17.75
406 5.75-11.75 660 7.5-11.75
12.5-13.75 12.5-13.75
/ 14.5-17.75

Advantages of ERW pipes:

  1. As only the edges are heated, the tube possesses dean accurate surface.
  2. Electric resistance welding can make tubes in sizes up to 0.4 metre diameter.
  3. Tubes can also be made from steels having around 0.3% carbon.
  4. Major factor is economy and especially in low pressure application.

Applications of ERW pipes:

ERW steel pipes are used in various engineering purposes, fencing, scaffolding, line pipes etc. It is available in lengths from single random to 120 feet depending on mill capability. What’s more, ERW steel pipes are usually used for Oil & gas pipelines, Agricultural purposes, Drinking Water for housings, in collieries for extraction of Water, Thermal Powers, Transports, Hand pumps for deep boring wells, as a strong protection for cables by Telecom Department, Structural Purposes etc. ERW steel pipe is available with square ends or beveled for welding, threaded and coupled and victaulic grooved. Surface finish of it is available in black or bare, or with protective coatings.

  • For low pressure fluid transmission, such as water pipelines, agriculture & irrigation (water mains, sewerage systems,industrial water lines, deep tube-wells & casing);
  • For machinery manufacturing, such as engineering purpose, fencing, scaffolding, line pipes etc.;
  • For Gas pipe lines (pipe lines for natural gas), LPG and other non-toxic gas.

Production Process for ERW steel pipe:

ERW steel pipe is manufactured by rolling metal and then welding it longitudinally across its length. ERW steel pipes are welded longitudinally, manufactured from Strip / Coil and can be manufactured up to 24”OD. ERW pipe cold formed from a ribbon of steel pulled through a series of rollers and formed into a tube which is fused through a electric charge.
Typical ERW tube manufacturing process of Prime Steel Pipe generally involves the following stages in a step by step procedure.

1.Uncoiling  2. Leveling  3. End cutting  4. End shearing welding  5. Supercoil accumulator  6. Edge cutting  7. Ultrasonic detection  8. Forming  9. Electric induction welding  10. Ultrasonic detection for weld seam  11. Medium frequency heat treatment  12. Air cooling  13. Water cooling  14. Sizing  15. Flying cutting  16. Flush-out  17. Cropping  18. Flattening testing  19. Straightening  20. End facing and bevelling  21. Hydrodynamic testing  22. Ultrasonic detection for weld seam  23. Ultrasonic detection for pipe end  24. Visual and dimensions inspection  25.Weighting and measuring  26. Marking  27. Coating  28. Pipe-end protection  29. Bending  30. Shipping

20170726233775507550 - Difference among ERW, SSAW, LSAW

Coil Feed Ramp

erw process Coil Feed Ramp - Difference among ERW, SSAW, LSAW

The coils are removed from storage and placed on the feed ramp (see Figure 4.1). Each coil is fed into the uncoiling unit.

First Forming Section

erw process First Forming Section - Difference among ERW, SSAW, LSAW

The roll transition section receives the product from the first forming section and continues the “rounding-up” process .

Final Forming Pass Section

erw process Final Forming Pass Section - Difference among ERW, SSAW, LSAW

This section of the forming rolls finishes the rounding process and prepares the edges of the strip for welding .

High-Frequency Welder

erw process High Frequency Welder - Difference among ERW, SSAW, LSAW

An automatic high-frequency welder heats the edges of the strip to approximately 2600 F at the fusion point location. 
Pressure rollers squeeze these heated edges together to form a fusion weld.

In-Process Weld Nondestructive Inspection

erw process In Process Weld Nondestructive Inspection - Difference among ERW, SSAW, LSAW
Nondestructive Inspection Unit

After welding has been completed, it is inspected by independent nondestructive inspection units.

Seam Weld Normalizing

erw process Seam Weld Normalizer - Difference among ERW, SSAW, LSAW

The weld area is then subjected to postweld treatment, as metallur-gically required, to remove residual welding stresses and produce a uniform normalized grain structure.

Sizing Mill

erw process Sizing Mill - Difference among ERW, SSAW, LSAW

The pipe passes through a sizing mill to achieve the correct outside diamete.

Cutting the Pipe

The pipe is then cut to the correct length.

End Facing And Bevelling

This is usually stage, where the pipes ends are faced and bevelled by the end facer. All these processes are continuous with automatic arrangements. These plain ended tubes further go for processing as per the customer requirements such as galvanizing, threading, black varnishing and more.

Surface Treatment for ERW Steel Pipe

ERW steel pipe, which is short for electric resistance welded steel pipe, is widely used for low pressure liquid delivery, such as water, gas and oil field, oil drilling and machinery manufacturing, etc.
Today, we’ll talk about most common seen surface treatment for electric resistance welded steel pipe.
First comes fusion bond epoxy, also known as FBE coating, which is widely used to protect steel pipe used in pipeline construction from corrosion. Working temperature for FBE coated steel pipe can up from 180℃ to 250℃.
Then comes varnish coating. Varnish coating is the most general surface treatment for steel pipe. General varnish coating is just an oil-liked coating on pipe surface and have strong anti-corrosion effect. For industrial steel pipes, varnish steel pipes is needed.
Another surface treatment for ERW steel pipe is PE. Both PE and 3PE is common seen ways. PE coated steel pipe is widely used for liquid transportation usage pipe.
Another surface treatment for ERW steel pipe is black oil coating. Black oil coating is widely used for all kinds of steel pipes. As we know, if there isn’t any surface treatment for steel pipe, it can get rust in few days in wet condition. But if we cover steel surface with black painting, it can keep well for months. And life span will expand accordingly.
There are also many other surface treatment for steel pipes, such as coal tar epoxy, bitumen coating, or other coating per customer’s requirement.

Welding process of ERW pipes

Several electric resistance welding (ERW) processes are available for tube and pipe production. While each process has different characteristics, all ERW processes have one thing in common–all of them produce a forged weld.
A forged weld is created by applying a combination of heat and pressure, or forging force, to the weld zone. A successful forged weld uses the optimum amount of heat, which is normally slightly less than the melting point of the material, and a nearly simultaneous application of circumferential pressure to the section, which forces the heated edges together (see Figure 1).
As the name implies, the heat generated by the weld power is a result of the material’s resistance to the flow of electrical current. The pressure comes from rolls that squeeze the tube into its finished shape.
The two main types of ERW are high-frequency (HF) and rotary contact wheel.

The Basics of HF Welding

electric resistance welding at a glance hf induction welding - Difference among ERW, SSAW, LSAW

The two main aspects of HF welding are processes and power supplies. Each of these can be broken down further into subcategories. Processes. The two HF welding processes are HF contact and HF induction. In both processes, the equipment that provides the electrical current is independent from the equipment that supplies the forge pressure. Also, both HF methods can employ impeders, which are soft magnetic components located inside the tube that help to focus the weld current in the strip edges.

electric resistance welding at a glance hf contact welding description - Difference among ERW, SSAW, LSAW

HF Induction Welding. In the case of HF induction welding, the weld current is transmitted to the material through a work coil in front of the weld point (see Figure 2). The work coil does not contact the tube–the electrical current is induced into the material through magnetic fields that surround the tube. HF induction welding eliminates contact marks and reduces the setup required when changing tube size. It also requires less maintenance than contact welding.
It is estimated that 90 percent of tube mills in North America use HF induction welding.
HF Contact Welding. HF contact welding transfers weld current to the material through contacts that ride on the strip (see Figure 3). The weld power is applied directly to the tube, which makes this process more electrically efficient than HF induction welding. Because it is more efficient, it is well-suited to heavy-wall and large-diameter tube production.
Power Supplies. HF welding machines also are classified by how they generate power. The two types are vacuum tube and solid-state. The vacuum tube type is the traditional power supply. Since their introduction in the early ’90s, however, solid-state units have quickly gained prominence in the industry. It is estimated that between 500 and 600 of each type are operating in North America.

The Basics of Rotary Contact Wheel Welding

In rotary contact wheel welding, the electrical current is transmitted through a contact wheel at the weld point. The contact wheel also applies some of the forge pressure necessary for the welding process.
The three main types of rotary contact wheel welders are AC, DC, and square wave. In all three power supplies, electrical current is transferred by brush assemblies that engage slip rings attached to a rotating shaft that supports the contact wheels. These contact wheels transfer the current to the strip edges.
AC Rotary Contact Wheel Welding. In an AC rotary contact wheel welding machine, the current is transferred through the brushes to the rotating shaft, which has a transformer mounted on it. The transformer reduces the voltage and increases the current, making it suitable for welding. The two legs of the transformer’s output circuit are connected to the two halves of the rotating contact wheel, which are insulated from each other. The strip completes the circuit by acting as a conductor between the two halves of the wheel.
Traditional rotary contact wheel welders used 60-hertz AC, or common line current. A drawback to this system is that the current–and therefore the weld heat–rises and falls, limiting the speed at which the tube can be welded. An AC sine wave reaches its maximum amplitude briefly, producing weld heat that varies just as the sine wave does.

electric resistance welding at a glance direct current weld - Difference among ERW, SSAW, LSAW

To help even out the heat variation, motor generator sets were introduced to create AC at higher frequencies. Some of the frequencies used were 180, 360, 480, and 960 Hz. A few solid-state units also were produced to generate higher-frequency currents. An AC sine wave at 960 Hz reaches its maximum amplitude 1,920 times per second, as opposed to 120 times per second with a 60-Hz signal. The 960-Hz sine wave produces heat with a much more consistent temperature.

DC Rotary Contact Wheel Welding. The next step in rotary contact wheel welding was the DC power supply. The power produced has a nearly constant amplitude. Although this solves the problem of varying heat, a major drawback is that higher maintenance costs are associated with this type of welding machine.

Because it is not possible to change the voltage of DC with a transformer, it is necessary to transmit the high-amperage, low-voltage weld current into the shaft through a large number of brushes (92 for DC versus 8 for AC) with a high current density. Transmitting high-amperage, low-voltage current produces excess (waste) heat that causes heavy wear, resulting in the high maintenance costs mentioned previously.

Square Wave Rotary Contact Wheel Welding. The latest step in the evolution of rotary contact wheel welding is the square wave power supply. This method combines the consistent weld heat of DC with the lower maintenance associated with AC units (see Figure 5). While rotary contact weld methods preceded the more commonly used HF welding processes, they still have a vital role in specialty welding applications. Rotary contact welding is useful for applications that cannot accommodate an impeder on the ID of the tube. Examples of this are small-diameter refrigeration-grade tube and tube that is painted on the ID immediately after the welding process.

How Many Roll Units Are Needed?

The types of weld pressure rolls, or squeeze boxes as they sometimes are called, that apply the pressure required for the weld are as varied as the welding units used to supply the heat. Squeeze boxes for rotary contact wheel welding typically have two or three roll units, with the contact wheel serving as one of the rolls.
The number of rolls in the weld squeeze box is proportionate to the size and shape of the product being welded. There are no hard and fast rules; however, common guidelines for round tube or pipe size ranges are as follows:

  • 3/8 to 2 in. uses two-roll units.
  • 1/2 to 3 1/2 in. uses three-roll units.
  • 2 to 10 in. uses four-roll units.
  • Larger than 10 in. uses five or more rolls.

Today, much more so than in the past, many shapes–square, rectangular, hexagonal–are welded in the finished shape rather than being reshaped after being welded round. The weld boxes used for the shapes are custom-designed for each application and usually have no more than five rolls.

Technical Requirements of ERW Steel Pipe

ERW pipes means Electric Resistance Welded Pipes. ERW steel pipes and tubes are used in various engineering purposes, fencing, scaffolding, line pipes etc. ERW steel pipes and tube are available in various qualities, wall thicknesses, and diameters of the finished pipes.

  1. Yield strength of the N80 is higher than the J55 up to 173 ~ 206 MPa.
  2. On the same area of the sample, the elongation of N80 is higher than J55.
  3. Under the same size, the same sample orientation, the same minimum sample size, J55 grade couplings, coupling stock, coupling material, semi-finished and coupling attachment material can absorb lower than N80 steel grade.
  4. The nondestructive testing methods of seamless pipe,coupling stock, welded tube with J55 and N80 is differeent.
  5. J55 and N80 steel grade is not the same color: length greater than or equal 1.8m, J55 painted a bright green, N80 painted a red;
  6. J55 chosen by the manufacturer, or organize according to the order specified length normalized (N), normalizing and tempering (N & T) or quenching and tempering (Q & T). N80 is a whole, full-length heat treatment is mandatory.

Production Technology Improving Process of ERW Pipes

Straight seam welded pipe (ERW straight seam welded steel pipe) is formed on the hot rolled plate of the forming machine, the skin effect and proximity effect of the high frequency current, melting of the pipe edge heating to the extrusion roller pressure welding to achieve production. The application of high-frequency resistance welding method in pipeline production in the 1950s has witnessed more and more mature production technology and continuous improvement of product quality in the past decade or so.
First of all, in the quality of raw materials, the production of ERW steel pipe has been significantly improved, the composition of the steel design of low carbon, low P, S, micro-alloying; smelting process smelting, ladle refining, vacuum degassing, continuous casting and other new technologies In addition to the ERW controlled rolling and cold rolling process, the technology has enabled the appearance size of the hot rolled steel strips of large and medium caliber ERW steel tubes to be greatly improved in appearance quality, physical properties and chemical properties. The steel pipelines produced by Baoshan Iron and Steel Company, the highest level of hot rolled strip steel in my country, have met the American Petroleum Institute API 5L standard and are at the international advanced level.
Followed by the middle and large diameter ERW molding welding and heat treatment process of the production process to achieve the computer automatic control, high frequency and computer automatic compensation system welding process heat input energy is effectively controlled to prevent welding heat input welding cold caused by low welding heat input and Excessive combustion caused by high energy. The heat treatment temperature control allows the heat treatment process to achieve the best results according to the process requirements, effectively ensuring the quality of the steel pipe welding and heat-affected zone.
In addition, the progress of ERW tube straight seam welded pipe inspection technology has achieved full online or offline ultrasonic or eddy current weld risk damage, and the hydraulic pressure test may be under the supervision of a computer, stress testing and regulatory requirements. The promotion and implementation of the standard and specification APIQ1 ISO9000 series ensure the quality assurance in the whole process of production, inspection, sales and service of medium and large caliber ERW straight seam steel pipes.
In recent years, various countries have been actively adopting ERW straight seam welded pipe and spiral welded pipe seamless pipe in place, in industrialized countries, ERW straight seam pipe diameter Ф610mm less, ERW steel pipe has reached about 70% of the proportion. Our production capacity of ERW Longitudinal also occasion enhanced.

ERW pipe issues and defects

ERW pipe issues and defects is related to raw materials, production methods, process conditions, equipment status and personnel. Product defects that appear in the production process by the above factors and constraints. This product defects can be divided into roughly two categories: one for product defects, that defects production of the product itself exist inconsistent sets of product standards; a class of defects generated during the production process defects, it do not form the product requirements of the standard items, but also an issue of product quality, and its trend of development will inevitably lead to product defects. Therefore, this defect is not allowed in the production process.

Process defects 

No burr: burr welds. Outer burr is generally better when the watertight test water pressure. But for Ling, bending, flattening test, weld most cracking. 
Peach tip: weld at no glitches, and recessed within the wall, forming the tip shape of peaches, try water pressure when water-tight. But bending, flattening test, weld multiple cracking. Within the burr unilateral: watertight seam burr for the side extrusion test water pressure. Bending, flattening test, sometimes cracking. 
Burnt: the outer surface of small pits in the weld, welding sparks a lot of splash, the microstructure observed small holes watertight when the test water pressure, bending, flattening test, most will not crack, but the impact on the intensity of use and life expectancy.

Weld defects 

Opening: straight weld plate edge face melting traces or melting traces without welding, crack two tip along the weld direction, expansion, penetrate the inner surface of the test water pressure, leaking. 
Crack: micro-crack crack; the outer surface of the visible appearance of fine lines, the inner surface of intact, no leakage in the test water pressure, but when crushed or cold-formed crack. 
Lap welding: two edge dislocation in the welding, scraping, except burrs can still see the obvious one side higher and exceed the wall thickness of the negative deviation.

Surface defects 

Scratch: the general was the axis of the straight channels and scratches, deeper than the wall thickness of the negative deviation of scrap defects in the weld on both sides of a continuous nail-shaped scratch. Super wall thickness of the negative deviation. Waste big flaw. 
Correction hurt: the leveler spiral crushed obviously feel more than the wall thickness of the negative bias of – waste defect. 
Pockmarked face: the tube surface successful piece punctate small pits with a diameter of about 1mm. 
Warp: the pipe surface warping the separation of the part and the metal substrate into pieces, not continuous, spalling can not afford.
At present, ordinary fluid on the market with the general Longitudinal Welded Pipe is generally used in high-frequency resistance welding production, which is characterized by high production efficiency, weld heat affected zone is small, low quality requirements on the bonding surface, but the molding quality requirements, forming process Any change in the shape of the V-shaped opening may cause welding quality problems.
Rolling groove processing is the use of grooved joints as pipe fittings when the pipe pretreatment process. Its operating principle is the use of roll groove rolling machine driven rotating pipe, pipe radial direction of the follow-up pressure roller radial pressure applied to the use of the structure of the pressure roller welded pipe in a fixed position of cold out a specified groove.
A “roll groove cracking” is the root cause of the weld strength is not enough, coupled with rolling groove processing of the severe deformation, resulting in weld stress concentration and tear. Raw material is the source of product quality, production must master its characteristics. From the welding point of view, the impact of raw materials on the quality of the weld is mainly reflected in the welding of the material and the two aspects of organization. Elements of alloying elements and the morphology of the weld quality also affect. The high content of sulfur and phosphorus in the material will easily cause crystallization segregation; the high carbon content will promote the formation of martensite, the embrittlement of the weld metal; the grain size of the metal structure is too large, the direction of the weld crystal will be strengthened; Easy to promote the segregation of impurities. There are non-metallic materials in the inclusion, stratification, width and thickness fluctuations, all kinds of factors may cause weld cracks and reduce weld strength.

ERW steel pipe main welding process parameters are input power, raw production speed, opening angle, welding pressure, induction coil (induction contact) and the location of the impedance and so on. The unreasonable setting of welding parameters is an important reason for the phenomenon of rolling groove cracking. If the input power is not enough, the speed is too fast, the input heat is insufficient, the edge of the steel strip is not completely melted, the end solid oxide can not be extruded out to form the low-temperature welding defect; conversely, the input heat is too large, , Metal splash and return inclusions and other defects. Secondly, the welding pressure is also important. If the welding pressure is not enough, the fusion line on both sides of the metal microstructure flow line is not obvious, welding strength will not meet the requirements; the other hand, the welding pressure is too large, irregular weld lines, metal flow line rise angle is too large, Reduced only when the welding pressure is appropriate should be, the fusion line without distortion, metal streamline angle of 45 °~ 60 °ideal state, the weld strength is guaranteed.

Cause Analysis of ERW Steel Pipe Surface Scratching

ERW steel pipe manufacturers, in the production of high-frequency welded pipe process, will face the tube surface was scratched the situation, the main reason for this is due to the guide roller and squeeze roller caused. The following specific analysis.

1. Scraping caused by the guide roll generally occurs on both sides of the high-frequency welded pipe, the characteristics of the wound is relatively large, continuous strong. Reasons include:

  • (1) The height of the guide sleeve position is not correct, such as the guide roller bearing damage, the guide roller can not be a good control of high-frequency welded pipe, so that friction with the guide sleeve caused by scratches.
  • (2) When the guide roll deviation from the high-frequency welded pipe production line rolling center line is too large, the guide sleeve and guide roller relative difference is too large, resulting in both sides of high-frequency welded pipe scratches.

2. Scratches caused by high-frequency welding squeeze rollers occur mainly at the bottom of high-frequency welded pipe. Reasons include:

  • (1) The hole does not match, resulting in ERW steel pipe surface scratches, the hole does not match the factors are: squeeze roller bearing damage, squeeze roller axial movement, squeeze roll hole size is not the same, the two extrusion Roller height position is different from the extrusion roller bending and assembly instability.
  • (2) Squeeze roller height does not match. The lower edge of the squeeze roll hole pattern should be consistent with the height of the rolling line, and the height of the guide roll is determined by the wall thickness of the ERW steel pipe. If the guide roller is too low, the edge of the extrusion roller hole rounded corner of the high-frequency welded pipe will cause the bottom of the scratches.
  • (3) Squeeze pressure on the roller is insufficient. Especially the two-roll structure of the squeeze roller device, when the pressure on the lack of ERW steel pipe tension in the role, the roller will appear on the elevation angle, the R edge of the hole prominent, resulting in high-frequency welded pipe Scratch the lower part. When the squeeze roller hole R-round grinding sharp, it will increase the scratches.

What is a SSAW steel pipe?

SSAW steel pipe is also known as the Spiral Submerged- Arc Welded Steel Pipe that is a type of spirally welded steel pipe produced by using the double-sided submerged arc welding method. Spiral welded pipes are formed using narrower plates or hot rolled coils, which lowers their production costs significantly. The spiral welding process permits the production of large-diameter pipes suitable for transporting large volumes of oil and gas. Traditional SSAW pipes were historically limited to low pressure applications; however, modern SSAW pipes have been used extensively in Russia, Canada, and Asian countries in high pressure gas pipelines.

ssaw pipes banner - Difference among ERW, SSAW, LSAW

Standard: API 5L, API 5CT, ASTM A252, ASTM 53, EN10217, EN10219, BS, JIS, ISGenerally used: welded pipes convey fluid, metal structures, pile and so on. Our products are widely used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction, and spiral submerged steel pipe is one of 20 key products of development. For the transport of liquids: water supply, drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe, for bridges; piers, roads, buildings and other structures tube.
The SAWH steel pipe is the spiral submerged arc welding steel pipe for short. It is made adopting sumberged arc welding technique and comes with a welding seam.
Yaang has overwhelming advantages over cometiotors in manufacturing this SAWH steel pipe.We have 10 traditional one-step production lines and 1 two-step production line that enabels to produce finely pre-welded SAWH steel pipe of 360000 tons per year,and we have become the leading enterprise in this industry in virtue of large productivity and advanced technical equipment.

  • Out Diameter: 219.1 mm – 2540mm (8″-100″)
  • Wall Thickness: 3.2mm – 25.4mm
  • Length: 6 – 22 m
  • Steel Grade: API 5L: GR A, GR B, X42,X46, X56, X60,X65,X70
  • ASTM A252 GR 1, GR 2, GR 3
  • ASTM A53: GR A, GR B, GR C, GR D
  • BS 4360: Grade 43, Grade 50
  • EN:S275, S275JR, S355JRH, S355J2H
  • Surface:Fusion bond Epoxy coating, Coal Tar Epoxy, 3PE, Vanish Coating, Bitumen Coating, Black Oil coating as per customer’s requirement
  • Test:Chemical Component Analysis, Mechanical Properties (Ultimate tensile strength, Yield strength, Elongation), Technical Properties (Flattening Test, Bending Test, Blow Test, Impact Test, Exterior Size Inspection, Hydrostatic Test, X-ray Test

SSAW steel pipe (spiral submerged arc welded steel pipe) is formed by spiral bending of hot-rolled strip steel, and spiral seam steel pipe (also called spiral welded pipe, spiral pipe spiral steel pipe) is formed by automatic welding of submerged arc for inner and outer joints. It can be widely used in the production of large diameter steel pipes for the following reasons:

  • 1) As long as the forming angle is changed, it is possible to produce steel pipes of various calibers with strips of the same width;
  • 2) Because the continuous bending is formed, the length of the steel pipe is not limited;
  • 3) The weld spiral is evenly distributed on the circumference of the whole steel pipe, so the steel pipe has high dimensional accuracy and high strength;
  • 4) It is easy to change the size and is suitable for the production of small batch and multi-type steel pipes.

Since the defect is parallel to the weld, the defect of the weld is an oblique defect for the spiral pipe. In the course of use, the principal stress direction of the steel pipe, that is, the equivalent defect length in the axial direction of the steel pipe is smaller than that of the straight seam pipe; secondly, since the pipeline steel is a rolled steel plate, the impact toughness has a large anisotropy.

The CVN value in the rolling direction can be three times higher than the CVN value perpendicular to the rolling direction. The main stress of the straight seam pipe is exactly perpendicular to the direction of the lowest impact resistance of the pipe, while the spiral pipe staggers the direction of the lowest impact resistance of the pipe, which turns the disadvantage of the long weld of the spiral pipe into an advantage.

Spiral submerged arc welded pipe (SSAW steel pipe) is the strip volume control when the forward direction and forming a molding pipe centerline angle (adjustable), side molding edge welding, the weld into a spiral, the advantage of the same specifications of the strip can beproduction of a variety of diameters of pipe, meet a wider range of raw materials, welds can avoid the main stress, the force is better, the disadvantage is poor geometry,the weld seam length compared to the straight pipe length, easy to produce cracks, pores, slag, welding and other welding defects side, welding stress was tensile stress state.General long-distance gas pipeline design specification spiral submerged arc welded pipe can only be used for Class 3, Class 4 area.

Foreign raw materials will be changed to improve this process steel, so that separate forming and welding, the welding and lean pre-, post-weld cold-expanding, then the quality of welding close to the UOE pipe, currently there is no such process,is the spiralFactory directions for improvement. “Natural Gas” is still used by the traditional spiral process of production, but the tube side of the expander.United States, Japan and Germany in general negative SSAW, that trunk should not use SSAW; Canada and Italy, some use SSAW, Russia, a small amount of use SSAW, and have developed a very strict additional conditions, due to historical reasons, most still use the main trunk domestic SSAW. LSAW pipe (LSAW) is a single plate as raw material, steel in the mold or molding machine pressure (volume) into the tube, using double-sided submerged arc welding method and Expanding from the produce.

Standard and Classfication of SSAW Steel Pipe

Classfication

Standard

Main Products

Line Pipe

API 5L PSL1/2

Line pipe

Casing

API 5CT/    ISO 11960 PSL1

Steel pipe for use as casing or tubing for wells of petroleum and natural gas industries

Steel Pipe for Fluid Service ASTM A53 Black and hot-hipped galvanized welded and seamless steel pipe
BS EN10217-2 Welded steel tybes for pressure purposes – delivery technical conditions – part2: Electric welded non- alloy and alloy steel tubes with specified elevated temperature properties
BS EN10217-5 Welded steel tybes for pressure purposes – delivery technical conditions – part5: submerged arc welded non-alloy and alloy steel tubes with specified elevated temperature properties
Steel Pipe for Ordinary Structure ASTM A252 Welded and seamless steel pipe piles
BS EN10219-1 Cold formed welded structural hollow sections of non-alloy and fine grain steels – part1: Technical delivert conditions
BS EN10219-2 Cold formed welded structural hollow sections of non-alloy and fine grain steels – part2: tolerances dimmsions and sectional properties

Usually welded pipes are used for the transportation of normally lower pressure fluids such as water, gas, air, oil and heating steam.
Ordinary carbon steel wire bushings (GB3640-88) are steel pipes used to protect electric wires in electrical installations such as industrial and civil buildings and installation machinery.
Straight seam welded pipe (YB242-63) is a steel pipe whose weld is parallel to the longitudinal direction of the steel pipe. Usually divided into metric electric welded pipe, welded thin-walled pipe, transformer cooling oil pipe and so on.
Spiral submerged arc welded pipe (SY5036-83) for pressurized fluid conveying is a hot-rolled steel strip coil for tube blank, regular temperature spiral forming, welded by double-sided submerged arc welding, spiral seam steel pipe for pressure fluid conveying . The steel pipe has strong pressure bearing capacity and good welding performance. It is safe and reliable after various strict scientific tests and tests. The steel pipe has a large caliber, high conveying efficiency, and can save investment in laying pipelines. It is mainly used to transport oil and natural gas pipelines.

Spiral seam high-frequency welded pipe (SY5038-83) for pressurized fluid conveying is a hot-rolled steel strip coil for tube blank, which is often spiral-formed by high-frequency lap welding, and used for spiral conveying of pressurized fluid. High-frequency welded steel pipe. The steel pipe has strong pressure bearing capacity and good plasticity, which is convenient for welding and processing. After various strict and scientific inspections and tests, the use is safe and reliable, the steel pipe has large caliber, high conveying efficiency, and can save investment in laying pipelines. It is mainly used for laying pipelines for transporting oil and natural gas.

Chemical Analysis and Mechanical Properties of SSAW Steel Pipe

The raw material of the SSAW steel pipe includes steel coil, welding wire, flux. All of raw materials must be through strict physical and chemical maintenance before the investment.

Standard

Grade

Chemical Composition(max)%

Mechanical Properties(min)

C

Si

Mn

P

S

Tensile Strength(Mpa)

Yield Strength(Mpa)

API 5CT

h40

0.030

417

417

J55

0.030

517

517

K55

0.300

655

655

API 5L PSL1

A

0.22

0.90

0.030

0.030

335

335

B

0.26

1.20

0.030

0.030

415

415

X42

0.26

1.30

0.030

0.030

415

415

X46

0.26

1.40

0.030

0.030

435

435

X52

0.26

1.40

0.030

0.030

460

460

X56

0.26

1.40

0.030

0.030

490

490

X60

0.26

1.40

0.030

0.030

520

520

X65

0.26

1.45

0.030

0.030

535

535

X70

0.26

1.65

0.030

0.030

570

570

API 5L PSL2

B

0.22

0.45

1.20

0.025

0.015

415

415

X42

0.22

0.45

1.30

0.025

0.015

415

415

X46

0.22

0.45

1.40

0.025

0.015

435

435

X52

0.22

0.45

1.40

0.025

0.015

460

460

X56

0.22

0.45

1.40

0.025

0.015

490

490

X60

0.12

0.45

1.60

0.025

0.015

520

520

X65

0.12

0.45

1.60

0.025

0.015

535

535

X70

0.12

0.45

1.70

0.025

0.015

570

570

X80

0.12

0.45

1.85

0.025

0.015

625

625

ASTM A53

A

0.25

0.10

0.95

0.050

0.045

330

330

B

0.30

0.10

1.20

0.050

0.045

415

415

ASTM A252

1

0.050

345

345

2

0.050

414

414

3

0.050

455

455

EN10217-1

P195TR1

0.13

0.35

0.70

0.025

0.020

320

320

P195TR2

0.13

0.35

0.70

0.025

0.020

320

320

P235TR1

0.16

0.35

1.20

0.025

0.020

360

360

P235TR2

0.16

0.35

1.20

0.025

0.020

360

360

P265TR1

0.20

0.40

1.40

0.025

0.020

410

410

P265TR2

0.20

0.40

1.40

0.025

0.020

410

410

EN10217-2

P195GH

0.13

0.35

0.70

0.025

0.020

320

320

P235GH

0.16

0.35

1.20

0.025

0.020

360

360

P265GH

0.20

0.40

1.40

0.025

0.020

410

410

EN10217-5

P235GH

0.16

0.35

1.20

0.025

0.020

360

360

P265GH

0.20

0.40

1.40

0.025

0.020

410

410

EN10219-1

S235JRH

0.17

1.40

0.040

0.040

360

360

S275JOH

0.20

1.50

0.035

0.035

410

410

S275J2H

0.20

1.50

0.030

0.030

410

410

S355JOH

0.22

0.55

1.60

0.035

0.035

470

470

S355J2H

0.22

0.55

1.60

0.030

0.030

470

470

S355K2H

0.22

0.55

1.60

0.030

0.030

470

470

Spiral Seam Annealing Systems:

outside diameter control - Difference among ERW, SSAW, LSAW
Outside Diameter Control
x ray testing online - Difference among ERW, SSAW, LSAW
X-Ray Testing Online
hydrostatic testing - Difference among ERW, SSAW, LSAW
Hydrostatic Testing
Thermatool designs and manufactures Spiral Seam Annealing systems for producers of SAW (submerged arc welded) API line pipe.

Offering all the basic features and benefits of Thermatool seam annealing systems designed for operation on longitudinally welded API pipe, Thermatool Spiral Seam Annealing systems, however, require the installation of specially “shaped” inductors.

These are custom designed on CAD systems in order to precisely follow the helix angle for a specific pipe diameter.

Production process of SSAW steel pipe

Spiral steel pipe is a spiral seam steel pipe which is made of steel coiled coil as raw material, which is often heated and extruded and welded by automatic double wire double-sided submerged arc welding process.

ssaw pipe process - Difference among ERW, SSAW, LSAW

  • (1) Raw materials are strip coils, welding wire, flux. Strict physical and chemical testing is required before input.
  • (2) The steel head and tail are butt jointed, and the single wire or double wire submerged arc welding is used, and the automatic submerged arc welding is used after the steel pipe is rolled.
  • (3) Before forming, the strip is leveled, trimmed, planed, surface cleaned and pre-bent.
  • (4) The electric contact pressure gauge is used to control the pressure of the cylinder on both sides of the conveyor to ensure the smooth conveying of the strip.
  • (5) Adopt external control or internal control roll molding.
  • (6) The weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, the amount of misalignment and the weld gap are strictly controlled.
  • (7) Both internal welding and external welding are performed by single-wire or double-wire submerged arc welding by American Lincoln welding machine to obtain stable welding specifications.
  • (8) The welded seams are all inspected by online continuous ultrasonic automatic injury inspection to ensure the non-destructive testing coverage of 100% spiral welds. If there is a defect, the alarm is automatically alarmed and sprayed, and the production worker adjusts the process parameters at any time to eliminate defects in time.
  • (9) The steel pipe is cut into individual pieces by an air plasma cutting machine.
  • (10) After cutting into a single steel pipe, each batch of steel pipe shall be subjected to a strict first inspection system to check the mechanical properties, chemical composition, bonding condition, surface quality of the steel pipe and non-destructive testing to ensure the pipe making process. After that, it can be officially put into production.
  • (11) The part of the weld with continuous acoustic flaw detection mark, after manual ultrasonic and X-ray review, if it is defective, after repair, it will pass the non-destructive test again until it is confirmed that the defect has been eliminated.
  • (12) The tube of the butt weld of the strip and the joint of the butt joint intersecting the spiral weld are all inspected by X-ray television or film.
  • (13) Each steel pipe is subjected to hydrostatic pressure test and the pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. The test parameters are automatically printed and recorded.
  • (14) Pipe end machining, so that the verticality of the end face, the groove angle and the blunt edge are accurately controlled.

Production Notes of SSAW Steel Pipe

SSAW steel pipe in the production process, we need to pay attention to a series of matters. Except for the following test items, according to the API standard and other relevant standards and the special requirements of some users, but also the need for steel, steel pipe and other tests Destructive tests, including physical and chemical properties of the raw materials into the plant sampling, visual inspection of 100% steel .

  • A. Oiled marking: steel after passing were oiled to prevent corrosion, and according to user requirements for marking.
  • B. Leveling Milling: The flat steel anvil machine so that the original curl, and then through the edge milling machine for two-sided steel milling, so as to meet the requirements of the plate width, plate edge parallelism and groove shape.
  • C. Shear molding: the steel plate production line along the outer edge of the spiral curl into a tube.
  • D. Butt cut: double-sided submerged arc welding using advanced technology to pre-welding, internal welding, outside welding. The welded steel pipe using a plasma-foot cut to specification length.

How to Increase the Stability of the SSAW Steel Pipe?

After the production of SSAW steel pipe, it should be stored.If we don’t do some measures to keep its stability, it will rust and be corroded. So we will talk about how to increase the stability of the spiral welded pipe today. Generally speaking, we have followed methods:

  1. Small and medium-sized steel, wire rod, rebar, steel pipe with medium diameter, wire and wire rope, etc., can be stored in well-ventilated shed, but must put covering in the upper part of the goods and underlay at the bottom of the goods.
  2. Some small steel shape, sheet steel, steel strip, silicon steel sheet, small diameter or thin-walled steel pipe, all kinds of cold-rolled or cold-drawn steel and the metal products with high prices and easy-to-corrode can be stored in warehouse.
  3. The ground or warehouse to store spiral steel pipe should choose the place where is orderly and clean, and it is easy to fluently drain away water. It should stay away from the factories and mines that products harmful gases or dust. We also need to remove the weeds and all debris to keep the steel clean on the ground.
  4. Large-scale structural steel, steel rail, large diameter steel pipe, forgings, etc. can be opened stack.
  5. In the warehouse, SSAW steel pipe should not be stacked with the acid, alkali, salt, cement and other materials that have corrodibility on steel together. Different varieties of steel should be stacked separately, to prevent confusion and prevent contact corrosion.

Advantages of SSAW steel pipe:

  1. High production efficiency. On the one hand, the wire length is shortened, the current and current density are improved, therefore, the penetration depth of the arc and the deposition efficiency of the welding wire are greatly improved. Generally, single-sided melting depth of can be up to 20mm if do not open the groove. On the other hand, due to thermal insulation of flux and slag, the arc basically has no loss of heat radiation, welding spatter is also few. Although the heat loss for melting the flux is increased, the overall thermal efficiency is still greatly increased.
  2. High quality of weld seam. The protective effect of the slag from the air is good, the welding parameters can be stabilized by automatic adjustment, the requirement of the welder’s technical level of is not high, the composition of weld seam is stable and the mechanical performance is better.
  3. Good working conditions. In addition to reducing the labor intensity of manual welding operations, it does not have arc radiation, which is the unique advantage of submerged arc welding.

Disadvantages of SSAW steel pipe:

The flexibility of submerged arc welding is not as good as manual welding, it is generally only suitable for the weld seam that in horizontal position or small gradient. Workpiece edge preparation and assembly quality requirements are higher, which is cost more working time. Due to using submerged arc welding, we can not see the bath and weld formation process, so the welding specification must be strictly controlled. 

How to Identify The Quality of SSAW Steel Pipe?

Poor quality SSAW steel pipe is easy to produce burrs, because some inferior manufacturers have tinpot equipment. Prime Steel Pipe is positioned as an excellent steel pipe manufacturer and exporter for carbon steel pipe, we have over 20 years to manufacture SSAW steel pipe. So the SSAW steel pipe produced by Prime Steel Pipe all have the best quality, you can trustingly choose our spiral welded pipe. Generally, burrs will scratch the appearance of SSAW steel pipe and is easy to fold, the tendons are thin and low. and often appear full of dissatisfaction with the phenomenon. The reason is that the manufacturers to achieve a large negative tolerance, waste a few Road before the reduction of the amount of large, iron type is small, well filled dissatisfaction. Prone to crack. The reason is that the blank is the adobe, the adobe pores and more, adobe in the cooling process due to the role of thermal stress, cracks, after rolling there are cracks.
SSAW steel pipe regularly appear quality problems in the production and use. So we need to identify the quality of SSAW steel pipe, in accordance with a certain way and performance testing, can be used in the actual use of an important role. Then how to identify fake spiral steel pipe method: there often are pimple phenomenon in appearance. In general, the overall effect of weighing will be better, mainly taking into account the cumulative error and probability theory of this problem. Pitted surface is due to the serious wear and tear caused by the uneven appearance of spiral steel pipe irregular irregular flaws. As the shoddy SSAW steel pipe manufacturers to pursue profits, often rolling the most rolling standard. Appearance easy to produce scar.
The end of top crops is smooth and tidy, composition of high-quality SSAW steel pipe is evenly. The pseudo-poor material due to poor quality, cutting the end of the face often have the phenomenon of meat, that is uneven, and no metallic luster. And because the false product manufacturers cut off the small head, head and tail will appear big ears. The size of the inner diameter fluctuates greatly. The reason is that l steel temperature is unstable yin and yang face. The composition of the steel is not uniform. Folding is the appearance of spiral steel pipe formed a variety of polylines, this defect often runs through the entire product longitudinal. The reason for the folding is due to the pursuit of high efficiency of the manufacturers, the amount of depression is too large, the occurrence of ear, the next rolling when the folding, folding products will crack after bending, thick-walled spiral steel strength decreased.
The temperature of the pseudo-material rolling is not standard, no metallic luster. A pale red or similar pig iron color. Cross section is oval. The reason is that manufacturers in order to save information, waste roll two before the pressure is too large, the strength of this rebar greatly reduced, and does not meet the specifications of the size of rebar. There are two reasons:. Fake spiral steel pipe material is not uniform, more impurities. Pseudo-poor material manufacturers guide equipment is simple, easy to stick steel, these impurities bite into the roll after the easy to produce scar.

How to Test the Stress Resistance of SSAW Steel Pipe?

The large-diameter ssaw steel pipe factory needs to test the product after the production is completed, especially its compressive capacity, because we usually use it in the ground when it is used, so it is required to have good pressure resistance, then how to test it.
Firstly, both ends of the tested steel pipe are sealed by the end seal device and low pressure water is injected. During the water injection process, the air in the pipe is exhausted through the exhaust valve. After the low pressure water is filled, the high pressure water is injected into the pipe through the pressurizing device to pressurize the gas. The specified test pressure is reached. After the specified test pressure is reached, the pressure is maintained for a predetermined period of time. If there is no leakage or deformation, the pressure is released.

Products that have been tested for resistance to stress can be used to ensure the effectiveness of the spiral tube. Of course, it is necessary to carry out relevant anti-corrosion measures according to its use environment to ensure its use effect and longevity.

What is a LSAW pipe?

LSAW Pipe (Longitudinal Submerged Arc-Welding Pipe), is taking the steel plate as raw material, mold it by the molding machine, then do double-sided submerged arc welding. Through this process the LSAW steel pipe will get excellent ductility, weld toughness, uniformity, plasticity and great sealing.

Diameters range and performances of LSAW pipe

Pipe O.D: Ф406.4~Ф1422.4mm(16-56in)
Pipe Length: Max.12.2m(40ft)
Wall Thickness: When the steel grade is X70, the wall thickness ranges from 6.4 to 26.4mm(0.252–1.04in);
When the steel grade is lower, the wall thickness will be increased accordingly
Product Standard: ISO3183-3; API Spec 5L, GB9711
Capacity: The annual output is 0.2million tons

Legnth:8-12.15m Material: API 5L Gr.B-X80, Standard: API spec. 5L; GB9711.1-97

lsaw range oil gas - Difference among ERW, SSAW, LSAW 

Range of LSAW pipes applied in construction

Range of roller pipes: Outer diameter: Ф1200-3800mm  |  Wall thickness: 12-120mm  |  Unit length (max) 3.2m.

lsaw range construction - Difference among ERW, SSAW, LSAW

Note: The specification in the table is available to Q345. Remarks: non-standard dimensions pipes can be produced to customer specifications.

Range of Roller Pipes

Range of roller pipes: Outer diameter: Ф1200-3800mm  |  Wall thickness: 12-120mm  |  Unit length (max) 3.2m.
Number Technical parameter

Unit

HQW11s-120X3200

1 Material yield limited

Mpa

245 345 345
2 Wall thickness

mm

120 100 110
3 Maximum pre-bending thickness mm 110 90 100
4 Maximum width of steel plate mm 3200 3200 3200
5 Minimum diameter of fully loaded rolling steel plate mm 2500 1600 1600

(Uing and Oing forming) UOE Pipes

UOE mill adopts Uing and Oing forming, the formed pipes are welded inside by five internal welding stations with three wires for each weld,and welded outside by four external welding stations with three wires for each weld.

SSAW pipe Manufacturing Process

SSAW Pipe (Spiral Submerged Arc-Welding Pipe), also called HSAW pipe, welding line shape like a helix. It is using the same welding technology of Submerged Arc-Welding with LSAW pipe. Differently SSAW pipe is spiral welded where the LSAW is longitudinally welded. Manufacturing process is rolling the steel strip, to make the rolling direction have an angle with the direction of the pipe center, forming and welding, so the welding seam is in a spiral line.

LSAW pipes manufacturing process - Difference among ERW, SSAW, LSAW

Roller Pipes Process Flow

Range of roller pipes: Outer diameter: Ф1200-3800mm  |  Wall thickness: 12-120mm  |  Unit length (max) 3.2m.

lsaw roller flow - Difference among ERW, SSAW, LSAW

The purpose of cold expansion for lsaw steel pipe

SAW Steel Pipe - Difference among ERW, SSAW, LSAW

After cold expansion for lsaw steel pipe, steel tube and pipe end diameter will increase by about one percent difference in diameter of the diameter, roundness, and the pipe ends are greatly improved, also have greatly improved the straightness of the steel pipe, steel pipe length of about 0.5% reduction in wall thickness decreases by about 0.8%.

Fully develop LSAW process should consider these changes, to determine the pipe plate width, length and thickness, and the pipe diameter in front of the enlarged diameter, in order to avoid the enlarged diameter steel pipe geometry reach the final requirements caused by substandard. 

The purpose of cold expansion for lsaw steel pipe has the followings:

(1) Improve pipe end geometric dimensional accuracy of LSAW steel pipe, so that the diameter of the steel tube and pipe end, roundness, and the diameter of the pipe ends Poor meet the standard requirements, facilitate field welding construction. 
(2) Reduce inhomogeneous deformation of LSAW steel pipe forming and welding process and decrease the residual stress of forming and welding of tube, and improve its distribution, improve the overall mechanical properties of the steel pipe. 
(3) Inspect the steel pipe overall performance comprehensively and effectively. 
(4) Improve the straight degree of lsaw steel pipe, especially for the smaller diameter LSAW pipe straight is more obvious.

Longitudinally Submerged Arc Welded Steel pipes list:

lsaw x70 1 - Difference among ERW, SSAW, LSAW lsaw x52 - Difference among ERW, SSAW, LSAW

Range of LSAW pipes applied in construction: Outer diameter: Ф350-1600mm, Wall thickness: 6-60mm, Unit length: 6-12m.

LSAW equipment

lsaw equipment flaw detector - Difference among ERW, SSAW, LSAWlsaw edge - Difference among ERW, SSAW, LSAWlsaw welding laboratory3 - Difference among ERW, SSAW, LSAW

The coherence of cutter head and plate clamping system guarantees the invariable parameters during the entire milling process; accordingly it ensures the milling quality and lays a good foundation for the success of subsequent welding.

Technology Center

lsaw chemical laboratory1 - Difference among ERW, SSAW, LSAW lsaw chemical laboratory2 - Difference among ERW, SSAW, LSAW lsaw chemical laboratory3 - Difference among ERW, SSAW, LSAW

A superior technology center has been establish ed including the domestic first-class chenical laboratory,mechanics laboratory,the metallographic test laboratory and welding laboratory with advanced equipments for inspection and test Accordingly,

The developing trend of LSAW steel pipe

The developing trend of LSAW steel pipe in the future:

  • in terms of the onshore gas,with the large diameter LSAW steel pipe, its single-tube gas transmission capacity could reach the level of 50 billion cubic meters / year, pipe diameter can reach ф1422mm, steel grade achieve X80, and gas transmission pressure can reach 12MPa;
  • in terms of the ocean steel pipe, the gas pipeline develops towards the direction of deep-sea pipeline (> 1500 meters), marine structural tube towards the direction of high-intensity, large wall thickness, for example ф610mm×31.8mm, X65 grade;
  • in terms of business management, plate and pipe integration (steelmaking – Continuous Casting – rolled plate – pipe manufacturing) is the future development trend, for example in Japan and India plate and strip production line is always equipped with a welded steel pipe unit;
  • entering the market of high-grade structural tubes, this is an important question to be considered by the LSAW steel pipe production line manufacturer when deploying the device, so it is necessary to set the preheating device before pre-welding, or set the heat treatment process and so on;
  • in marketing, in addition to oil and gas pipelines, there is slurry pipelines;
  • anti HIC tube and anti deformed tube are with a considerable market prospect, can be used to transport acid gases and improve the ability against external environmental damage in harsh geological conditions (landslides, mudslides, earthquakes).

Advantages of LSAW steel pipe

In the long-distance pipeline construction, pipe-line account for a large proportion, generally 35% to 40% of line pipe accounts for investment projects total investment.

How to choose a reasonable price, excellent performance pipe is particularly important to a reasonable choice of pipe to save construction investment, easy construction and safe operation of the pipeline system has a very important influence. Gas Pipelines straight seam steel high-frequency electric resistance welded steel pipe, spiral submerged arc welded pipe, LSAW steel pipe.

Limited frequency straight seam electric resistance welded steel pipe diameter range is generally limited to domestic steel Φ406.4 mm or less, the largest in Japan has reached a diameter Φ508mm. For large diameter pipe in the form of a spiral SAW, LSAW two kinds. Spiral welded steel pipe because the pipe forming process and characteristics of many shortcomings, the proportion is gradually declining in the long-distance pipeline.

In other countries, especially in many European countries, it has banned the use of spiral submerged arc welded pipe used as the main line pipe. The advantage of its unique LSAW are widely used in long-distance oil and gas pipelines, and its advantages are as follows:

(1) without the unwind process, the base material indentation, scratch less.
(2) the wrong side, slotted, and other easy-to-diameter perimeter control, excellent welding quality.
(3) the elimination of flaring basically does not exist residual stress after stress. 
(4) because it is a straight line weld, the weld is short, little risk of defects. 
(5) after expanding, pipe geometry accuracy is improved greatly facilitate the on-site welding. 
(6) for a straight seam, less impact on the quality of anti-corrosion coating materials.

Applications of SSAW pipe

For oil and gas pipeline systems, but in petroleum design specification, the SSAW pipe / HSAW pipe could only be applied in class 3 and class 4 areas. Construction structure, water transport and sewage treatment, thermal industry, buildings etc.

Difference among ERW, SSAW, LSAW

Steel pipe for pipe technology, can be divided into (SML), mainly as the Oilfield internal transportation pipeline and small-diameter high-pressure natural gas pipeline, used for a small number of long-distance gas pipeline, the vast majority of long-distance pipeline with Direct seam high frequency (ERW), spiral submerged arc (SSAW), LSAW three (LSAW).

Here are comparisons of technological features and performance of these pipes:

general welded steel pipe - Difference among ERW, SSAW, LSAW

ERW pipes means Electric Resistance Welded Pipes.

High frequency straight seam welding (ERW) method is divided into two forms of induction welding and contact welding, hot-rolled wide volume as raw material, pre-curved, continuous molding, welding, heat treatment, sizing, straightening, cutting, etc. process, compared with the spiral weld short, high dimensional accuracy, uniform thickness, surface quality, pressure advantages, but the drawback is that only the production of small and medium-caliber thin-walled tube, weld easy to produce gray leaf spot, not fusion ditch-like corrosion defects. Wider application areas of city gas, crude oil transportation.

ssaw pipes banner - Difference among ERW, SSAW, LSAW

Spiral submerged arc welding (SSAW)

SSAW pipe is its forward direction and forming tube centerline hose reel molding angle (adjustable), side molding edge welding and weld them into a spiral.

Spiral submerged arc pipe (SSAW pipeis its forward direction and forming tube centerline hose reel molding angle (adjustable), side molding edge welding and weld them into a spiral, the advantage of the same specification to produce a variety of diameter sizes steel pipe, raw materials to adapt to a wider range, the weld can avoid the main stress force better, the disadvantage is the poor geometry of the weld length compared to the long straight seam pipe, prone to cracking, porosity, slag, welding partial welding defects such as welding stress was tensile stress state. General Oil and Gas Pipeline design specification spiral submerged arc can only be used for Class 3, Class 4 regional. Raw materials instead will this process improvement abroad steel plate forming and welding separate pre-weld and lean and, after welding cold flaring near UOE pipe welding quality, currently no such process of plant improvement direction. “West-East” still is a traditional craft production, just expanded diameter of the pipe end. United States, Japan and Germany, the overall negative SSAW, think the mainline unfit for use SSAW; Canada and Italy part SSAW Russian small amount of SSAW, and have developed a very strict supplementary conditions, due to historical reasons, the majority of the domestic main trunk or use SSAW.

lsaw pipes banner - Difference among ERW, SSAW, LSAW

Longitudinally Submerged Arc Welded Steel pipes

LSAW (LSAW) in leaflets plate as raw material, the steel plate in the mold or molding machine pressure (volume) into using double-sided submerged arc welding and flaring from production. A wide range of the finished product specifications, weld toughness, ductility, uniformity and dense, with a large diameter, wall thickness, high pressure resistance, low-temperature corrosion resistance, etc.. Required steel pipe in the construction of high-strength, high toughness, high-quality long-distance oil and gas pipelines, mostly large diameter thick wall LSAW.

API standard provisions, in the large-scale oil and gas pipelines, when 1, Class 2 areas through the alpine zone, the bottom of the sea, the city densely populated area, LSAW only applied specifically casts. Molding can be divided into:

uoe pipe banner - Difference among ERW, SSAW, LSAW

UOE: leaflets steel plate after the edge preflex, after U molding, O forming within welding, the outer welding, mechanical cold expanded diameter process;

jcoe pipes banner - Difference among ERW, SSAW, LSAW

JCOE: Press “JCOE” pre-welding, forming, welding after cold expanded diameter process.

Source: China Welded Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

Please notice that you might be interested in the other technical articles we’ve published:

  • How to get high quality stainless steel pipes

  • What is the difference between a steel pipe and a steel tube

  • Engineering Specification for Pressure Test of Piping System

  • How To Distinguish Inferior Steel Pipe

  • How to get high quality steel pipes

  • Manufacturing process of cold rolled steel pipe

  • How to get high quality boiler tubes

  • What Is A LSAW Pipe

  • How to get high quality alloy steel pipes

  • What is a SSAW steel pipe

  • What Is A LSAW Pipe

  • The difference between steel tubes and steel pipes

  • THE DIFFERENCE BETWEEN STEEL TUBES AND STEEL PIPES

  • Difference between welded steel pipe and seamless steel pipe

  • Characteristics of seamless steel pipes

  • What is a seamless steel pipe

Reference:

  • https://www.yaang.com

Related News

العربيةБългарски简体中文繁體中文DanskNederlandsEnglishFrançaisDeutschBahasa IndonesiaItaliano日本語한국어LatinPortuguêsРусскийEspañolதமிழ்ไทยTürkçe