What are Carbon Steel Pipes?
Carbon steel pipes are also called cs pipes. The general carbon steel pipe is made of 10, 20, 30, 35, 45 and other high-quality carbon steel 16Mn, 5MnV and other low-alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steel hot-rolled or Cold rolled. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid conveying pipes. 45, 40Cr and other medium carbon steel seamless pipes are used to make mechanical parts, such as the force parts of automobiles and tractors.
|1 Types||4 Manufacturing Process|
|2 Specification & Standard||5 Usage|
|3 Chemical Composition|
Carbon steel pipes are divided into two types: hot rolled and cold rolled (drawn) steel pipes.
Hot-rolled carbon steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes.
Cold-rolled carbon steel pipe is divided into general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe, other steel pipes, and also includes carbon thin-walled steel pipe, alloy thin-walled steel pipe, Rust thin-walled steel pipe, special-shaped steel pipe. The outer diameter of hot-rolled seamless pipe is generally larger than 32mm, the wall thickness is 2.5-75mm, the outer diameter of cold-rolled seamless steel pipe can be up to 6mm, the wall thickness can be up to 0.25mm, the outer diameter of thin-walled pipe can be 5mm, and the wall thickness is less than 0.25mm. Cold rolling is more accurate than hot rolling.
General carbon steel pipe: It is made of low-alloy structural steel such as 16Mn, 5MnV, such as 10, 20, 30, 35, 45, etc., or alloy steel such as 40Cr, 30CrMnSi, 45Mn2, 40MnB, etc., which is hot rolled or cold rolled. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid conveying pipes. 45, 40Cr and other medium carbon steel seamless pipes are used to make mechanical parts, such as the force parts of automobiles and tractors. Generally, carbon steel pipes are required to ensure strength and flattening tests. The hot rolled steel pipe is delivered in a hot rolled state or a heat treated state; the cold rolling is delivered in a heat treated state.
Specification & Standard of CS pipe
ASTM / ASME
|Product name||Executive standard||Dimension (mm)||Steel code/ Steel grade|
|Black and Hot-dipped Zinc-coated Steel Pipes Seamless||ASTM A53||0.3~1200 x 1.0~150||GR.A, GR.B, GR.C|
|Seamless Carbon Steel for High Temperature Service||ASTM A106||10.3~1200 x 1.0~150||GR.B, GR.C|
|Seamless Cold-drawn Low-Carbon Steel Heat-Exchanger and Condenser Tubes||ASTM A179||10.3~426 x 1.0~36||Low Carbon Steel|
|Seamless Carbon Steel Boiler Tubes for High Pressure||ASTM A192||10.3~426 x 1.0~36||Low Carbon Steel|
|Seamless Cold-drawn Intermediate Alloy Steel Heat-exchanger and Condenser Tubes||ASTM A199||10.3~426 x 1.0~36||T5, T22|
|Seamless Medium-carbon Steel Boiler and Superheater Tubes||ASTM A210||10.3~426 x 1.0~36||A1, C|
|Seamless Ferritic and Austenitic Alloy Steel Boiler, Superheater and Heat-exchanger Tubes||ASTM A213||10.3~426 x 1.0~36||T5, T9, T11, T12, T22, T91|
|Seamless Carbon and Alloy Steel for Mechanical Tubing||ASTM A333||1/4″~42″ x SCH20~XXS||Gr1, Gr3, Gr6|
|Seamless and Welded Carbon Steel Pipes and Alloy Steel Pipes for Low Temperature Use||ASTM A334||1/4″~4″ x SCH20~SCH80||Gr1, Gr6|
|Seamless Cold-drawn Carbon Steel Feedwater Heater Tubes||ASTM A556||10.3~426 x 1.0~36||A2, B2|
|Product name||Executive standard||Dimension (mm)||Steel code/ Steel grade|
|Seamless Steel Tubes for Elevated Temperature||DIN 17175||10~762 x 1.0~120||St35.8,St45.8, 10CrMo910, 15Mo3, 13CrMo44, STPL340, STB410, STB510, WB36|
|Seamless Steel Tubes||DIN 1629||13.5~762 x 1.8~120||St37.0, St44.0, St52.0|
|Seamless Precision Steel Tube||DIN 2391||4.0~60.0 x 0.5~8||St35, St45, St52|
|Seamless Steel Tubes||DIN 2440||13.5~165.1 x 1.8~4.85||St33.2|
API SPEC 5CT / 5L
Specification for Casing and Tubing, Eighth Edition, Petroleum and natural gas industries-Steel pipes for use as casing or tubing for wells.
|Product name||Executive standard||Dimension (mm)||Steel code/ Steel grade|
|Casting||API 5CT||114~219 x 5.2~22.2||J55, K55, N80, L80, P110|
|Tubing||API 5CT||48.3~114.3 x 3.2~16||J55, K55, N80, L80, H40|
|Casting||API 5L||10.3~1200 x1.0~120||A, B, X42, X46, X52, PSL1 / PSL2|
Japanese Industrial Standards (JIS) specifies the standards used for industrial activities in Japan.
|Product name||Executive standard||Dimension (mm)||Steel code/ Steel grade|
|High pressure and high temperature service||JIS G3454/5/6||19.05~114.3 x 2.0~14||JIS G3454(STPG370, STPG410), JIS G3455(STS370, STS410, STS480), JIS G3456(STPT370, STPT410, STPT480)|
|Tubes used for machinery, automobiles, bicycles, furniture, appliances and other machine parts.||JIS G3445||19.05~114.3 x 2.0~14||STKM11A, STKM12(A,B,C), STKM13(A,B,C), STKM14(A,B,C).|
|Carbon steel/Alloy steel boiler and heat exchanger tubes||JIS G3461,2||19.05~114.3 x 2.0~14||
G3461(STB340, STB410, STB510)
|Seamless steel tubes for high pressure gas cylinder||JIS G3429||
19.05~114.3 x 2.0~14
Length: max 16000mm
|STH11, STH12, STH21, STH22|
|Product name||Executive standard||Dimension (mm)||Steel code/ Steel grade|
|Low and medium pressure boiler seamless pipe||GB 3087||19.05~114.3 x 2.0~14||10#, 20#, 20G|
|Low-temperature heat exchanger tubes seamless steel pipe||GB/T18984||19.05~351 x 2.0~14||06Ni3MoDG, 09DG, 09Mn2VDG, 10MnDG, 16MnDG|
|High pressure and above pressure steam boiler tubes with high quality carbon structural.||GB5310||19.05~114.3 x 2.0~14||20G, 20MnG, 25MnG, 15MoG, 20MoG, 12CrMoG, 15CrMoG(T12/P12), 12CrMoG, 12Cr2MoWVTiB.|
|Steel Grade||Standard Number||Type||Chemical composition||Other|
|20g||GB713||Plate||0.2||0.15-0.3||0.035||0.035||0.5-0.9||400-530||245||26||Akv J:27；aku J/cm2：29|
Carbon Steel VS Alloy Steel
Carbon steel: mainly refers to the mechanical properties depend on the carbon content of steel, and generally do not add a lot of alloying elements of steel, sometimes called plain carbon steel or carbon steel. Carbon steel, also known as carbon steel, carbon content WC less than 2% iron carbon alloy. Carbon steel in addition generally contains a small amount of silicon, manganese, sulfur, phosphorus can be divided according to the use of carbon steel carbon structural steel, carbon tool steel and free-cutting structural steel three carbon structural steel is divided into structural steel and machine structural steel, which can be divided into low carbon steel (WC ≤ 0.25%), medium carbon steel (WC 0.25% – 0.6% ) and high carbon steels (WC> 0.6%). According to phosphorus and sulfur content, carbon steels can be divided into ordinary carbon steels (phosphorus and sulfur are higher), high quality carbon steels (phosphorus and sulfur are lower) high-quality steel (phosphorus, sulfur lower) the higher the carbon content of carbon steel, the higher the hardness, the higher the strength, but lower plasticity.
Alloy steel: based on carbon steel, one or more alloying elements are deliberately added to improve the serviceability and process performance of the iron-based alloy is called alloy steel. Alloy steel refers to the steel containing silicon and manganese as alloying elements or deoxidizing elements, other alloying elements such as chromium, nickel, molybdenum, vanadium, titanium, copper, tungsten, aluminum, cobalt, niobium, zirconium and other elements, and some also contain some non-metal elements (such as boron, nitrogen, etc.) steel. According to the amount of alloying elements in steel, but also can be divided into low alloy steel, medium alloy and high alloy steel.
Chemical composition difference
(1) Carbon steel: a. Low carbon steel (C≤0.25%); b. Medium carbon steel (C≤0.25 ~ 0.60%); c. High carbon steel (C≤0.60%).
(2) Alloy steel: a low alloy steel (total content of alloying elements ≤ 5%) b. Alloy steel (total content of alloying elements> 5 ~ 10%) c. High alloy steel (total content of alloying elements> 10%.
Carbon steel advantages:
Carbon steel has high strength, ductility and toughness, low cost, used in heavy machinery for the manufacture of heavy load parts. The total amount of gold is generally less than 5%, has greater impact toughness, and can be obtained by heat treatment better mechanical properties cast low alloy steel has better performance than carbon steel, can reduce the quality of parts and improve service life.
Alloy steel advantages:
In addition to iron in steel elements containing only carbon steel, carbon steel, other silicon, sulfur, phosphorus and other impurities, 45 steel can do general structural steel, steel 65 can do general spring steel, tool steel; In addition to other elements of chromium, manganese, molybdenum, titanium, tungsten, vanadium, niobium, boron, silicon and nickel alloy steel to achieve the desired properties such as high temperature, high elasticity, abrasion resistance, high strength, high toughness and so on. Alloy steel hardness wear resistance, hardenability, corrosion resistance than carbon steel excellent. In the mechanical parts of the wider use of carbon steel.
Carburizing speed comparison
All carbide-forming elements (titanium, chromium, molybdenum, etc.) increase the carbon concentration on the surface of the infiltration layer, and non-carbide forming elements (silicon, aluminum and nickel) reduce the carbon concentration on the surface of the diffusion layer. However, the influence of these alloying elements is not always the same, and the contents of alloying elements and carbon elements in the same grade of carbon steel or alloy steel are not necessarily the same.
Carbon Steel vs Black Steel
Carbon steel is susceptible to corrosion. Blackening is a process to create a tenacious oxide coating that provides some corrosion resistance.
Black steel is made of steel that has not been galvanized. Its name comes from the scaly, dark-colored iron oxide coating on its surface. It’s used in applications that don’t require galvanized steel.
There are different classes of carbon steel. They are categorized by the percentage of carbon that is mixed with the base element, iron.
Classes of carbon steel Carbon content %
|Ultra-high carbon steel||1.00 – 2.00|
|High carbon steel||0.60 – 0.99|
|Medium carbon steel||0.30 – 0.59|
|Low carbon steel||0.16 – 0.29|
|Mild carbon steel||0.05 – 0.15|
Black steel pipe is manufactured as seamless which makes it a better type for gas transportation. It can be used for fire sprinkler system since it can prevent fire better than galvanized pipe. Since it has a dark color surface that is form by iron oxide during the manufacturing process, it is called black steel pipe.
Black steel pipe’s strength makes it ideal for transporting water and gas in rural and urban areas and for conduits that protect electrical wiring and for delivering high pressure steam and air. The oil and petroleum industries use black steel pipe for moving large quantities of oil through remote areas. This is beneficial, since black steel pipe requires very little maintenance. Other uses for black steel pipes include gas distribution inside and outside homes, water wells and sewage systems. Black steel pipes are never used for transporting potable water.
Carbon steel pipe is divided into seamless pipe and welded pipe. We introduce the manufacturing methods of two types of steel pipes:
Seamless steel pipe production process
Cold drawn seamless steel pipe process
round tube → heating → perforation → Heading → annealing → pickling → oiled (copper) → multi-pass cold drawn (cold rolled) → blank tube → heat treatment → straightening →hydrostatic testing (testing) → mark → storage.
The general cold strip mills, volume should go through continuous annealing (CAPL unit) to eliminate cold hardening and rolling stress, or batch annealing reach the mechanical properties of the corresponding standard specifies. Cold rolled steel surface quality, appearance, dimensional accuracy better than hot-rolled plate, and right-rolled thin product thickness is about 0.18mm, so the majority of users favor.
Cold rolled steel coil substrate products deep processing of high value-added products. Such as electro-galvanized, hot dip galvanized, electro-galvanized fingerprint resistant, painted steel roll damping composite steel, PVC laminating steel plates, etc., so that the excellent quality of these products has a beautiful, high resistance to corrosion, has been widely used.
Cold rolled steel coil finishing after annealing, cut the head, tail, trimming, flattening, smooth, heavy volume, or longitudinal clipboard. Cold-rolled products are widely used in automobile manufacturing, household electrical appliances, instruments, switches, buildings, office furniture and other industries. Steel plate strapping package weight of 3 to 5 tons. Flat sub-volume typically 3 to 10 tons / volume. Coil diameter 6m.
Cold drawn steel tube is with hot-rolled steel coil as raw material, and tandem cold rolling pickled to remove oxide scale, its finished rolling hard roll, rolling hard volumes due to the continuous cold deformation caused by cold hardening strength, hardness increased indicators declined tough plastic, stamping performance will deteriorate, which can only be used for simple deformation of the parts.
Hot rolled seamless steel pipe deformed process
Hot-rolled seamless steel pipe production base deformation process can be summarized as three stages: perforation, extension and finishing.
round tube → heating → perforation → → three-roll rolling, rolling or extrusion → detached → sizing (or reducing) → cooling → straightening hydraulic test (orflaw) → tag → storage.
Billet is fed into the heating furnace, the temperature is about 1200 degrees Celsius. Fuel for a hydrogen or acetylene. The furnace temperature control is critical to wear air tube round, after the release of pressure puncher. which are generally more common puncher tapered roller punch this punch, high production efficiency, product quality, perforated expanding volume, wearing a variety of steels. After perforation, round tube has been three-roll cross rolling, rolling or extrusion.
After extrusion off pipe sizing. Sizing mill by the high-speed rotation of the cone drill into the Billet punch to form a steel pipe. The steel pipe inner diameter is determined by the length of the outer diameter of the sizing mill drill. After sizing, the steel pipe to enter the cooling tower by the water spray cooling, the steel pipe after cooling, it is necessary to be straightening. Sent by conveyor pipe by straightening the metal detection machine (or hydrostatic test) to conduct an internal flaw. Steel pipe internal issues such as cracks, bubbles will be detected.
Steel pipe quality inspection but also through a rigorous manual selection. Steel pipe of Quality Supervision, Inspection, use spray paint on the number, size, production batch. By a cable car hanging into the warehouse.
Welded Pipes are manufactured from Plate or continues Coil or strips. To manufacture welded pipe, first plate or coil is rolled in the circular section with the help of plate bending machine or by a roller in the case of continues process. Once the circular section is rolled from the plate, the pipe can be welded with or without filler material. Welded pipe can be manufactured in large size without any upper restriction. Welded pipe with filler material can be used in the manufacturing of long radius bends and elbow. Welded pipes are cheaper with compared to the seamless pipe and also Weak due to the weld
There are different welding methods used to weld the pipe.
- ERW- Electric Resistance Welding
- EFW- Electric Fusion Welding
- HFW- High-frequency welding
- SAW- Submerged Arc Welding (Long seam & Spiral Seam)
ERW Steel Pipe Manufacturing Process
In the ERW / EFW / HFW pipe process, first plate is formed in a cylindrical shape and the longitudinal edges of the cylinder formed are welded by flash-welding, low-frequency resistance-welding, high-frequency induction welding, or high-frequency resistance welding.
SAW Pipe Manufacturing Process
In SAW welding process, external filler metal (wire electrodes) are used to join the formed plates. SAW pipes can have a single longitudinal seam of double longitudinal seam depend on the size of the pipe. SAW pipe are also available in the spiral seam, which is continually rolled from the single plate coil. The production rate of spiral SAW pipe is very high as compared to Straight SAW pipe. However, Spiral SAW pipe are only used in low-pressure services such as water, non-critical process services etc.
Straight SAW Pipe Welding
Spiral SAW Pipe Welding
Heat Treatment of Cold Drawn Seamless Steel Pipe
Cold drawn seamless pipe is used for high dimensional accuracy mechanical structure, hydraulic equipment and good surface finish cold drawn or cold rolled precision seamless steel tubes. High-precision drawing denotes the outer diameter size precision (tolerance) strict and external surface finish, roundness, straightness good thickness uniformity.
Heat treatment of cold drawn seamless steel pipe:
- (1) Cold drawn steel annealing: refers to the metal material is heated to the appropriate temperature, to maintain a certain time, and then slowly cooled heat treatment process. Common annealing process are: recrystallization annealing, stress relieving, ball annealing, fully annealed and so on. The purpose of annealing: mainly to reduce the hardness of the metal material, to improve the plasticity, or cutting processing to Liqie pressure processing, reduce the residual stress and improve the uniformity of microstructure and composition, heat treatment, after possible or tissue preparation.
- (2) Cold drawn steel normalizing: refers to the heating of steel or steel to Ac3 or Acm (the critical temperature of steel) over 30 ~ 50 ℃, after an appropriate time to keep cool in still air in the heat treatment process . The purpose of normalizing: mainly to improve the mechanical properties of low carbon steel to improve machinability, grain refinement, elimination of tissue defects, prepare for the heat treatment, after tissue preparation.
- (3) Cold drawn steel hardening: refers to the heated steel Ac3 or Ac1 (lower critical temperature of steel) above a certain temperature for a certain time, then the appropriate cooling rate to obtain martensite (or shellfish Heat Treatment’s body) tissue. Common salt bath quenching process has hardened, martensitic quenching, Austempering, surface hardening and partial quenching. Quenching purpose: to make the steel needed to obtain martensite improve workpiece hardness, strength and wear resistance, heat treatment, after prepare for the organization and preparation.
- (4) Cold drawn steel tempered: that after hardened steel, and then heated to a temperature below Ac1, holding a certain time, and then cooled to room temperature, the heat treatment process. Common tempering process are: tempering, tempering, tempering and multiple tempering. The purpose of tempering: mainly steel eliminate stress produced during quenching, the steel having high hardness and wear resistance, but also has the required plasticity and toughness.
- (5) Cold drawn steel quenched: refers to the quenching and tempering of steel or composite steel heat treatment process. Used in quenching said steel quenched and tempered steel. It generally refers to the carbon structure of carbon steel and alloy steel.
- (6) Cold drawn steel chemical treatment: refers to the metal or alloy workpieces placed in a constant temperature of the active medium heat, so that one or several elements into its surface to change its chemical composition, microstructure and properties of the heat treatment process. Common chemical heat treatment process are: carburizing, nitriding, carbonitriding, aluminized boron penetration. The purpose of chemical treatment: The main is to improve the steel surface hardness, wear resistance, corrosion resistance, fatigue strength and oxidation resistance.
- (7) Cold drawn steel solution treatment: that the alloy is heated to a high temperature single-phase region to maintain a constant temperature, so that the excess phase fully dissolved into the solid solution after rapid cooling, in order to get over the supersaturated solid solution heat treatment process. The purpose of solution treatment: mainly to improve the ductility and toughness of steel and alloys, to prepare for the precipitation hardening treatment and so on.
Precautions for Installation of Carbon Seamless Steel Pipe
(1) Carbon seamless steel pipe should be carefully installed before the following carefully checked to ensure the quality of pipe and pipe.
A. Check the factory and pipe fittings factory certificate, quality certificate or test records, test records and other technical information, and should comply with existing national standards.
B. Check the quality marks of the pipe and fittings, expansion joint to meet the technical document and the current national standard. If there is any problem, replace or take the measures.
C. Check the quality of the outer surface of the pipe and pipe fittings, wall thickness should be consistent with national standards. The ellipticity is not allowed to exceed the specified range. No cracks, no shrinkage, no slag, no folding, no heavy skin, no trachoma, no pinhole, no more than the thickness of the local pit tolerance, no bumps and other quality problems, and the tube Internal and external surface without serious corrosion when the pipe and pipe fittings qualified.
(2) When the pipe surface rust less number of pipes can not be used when the number of hand-rust, the general hand-rust is a wire brush, wire cloth, emery cloth and other friction, remove the rust on the pipe surface, and then dry cotton yarn Wipe or clean, so that the pipe surface exposed metallic luster.
(3) When the pipe surface rust more, and the larger number of pipes and generally use mechanical rust or sand blasting rust or pickling rust. Pickling rust rust when the general use of sulfuric acid or hydrochloric acid.
(4) Brush the surface of the pipe type of anti-rust paint should be selected according to design requirements, commonly used red lead rust paint, epoxy paint, etc., the surface finish is generally blending paint.
Before painting, clean the surface of the pipe clean dust, dirt, burr, oil and water. Brush should be uniform coating, do not leak coating, brush the paint after the eligibility criteria for attachment firmly, no flaking, no wrinkles, no bubbles, no leakage coating, no damage and other defects.
Pickling Technics for Carbon steel pipe
Carbon steel pipe pickling method currently are used in the construction and management of two trough pickling pickling inner loop.
(1) trough pickling. The installed piping removed after decomposition into pickling bath soak treatment after passing their secondary installation. This method is suitable for larger diameter tube short, straight, easy to disassemble, piping and a small amount of on-site piping system hydraulics hydraulic piping construction of small amounts of occasions, such as pumping stations, valve stations inside, can be used trough pickling method.
(2) pipe loop pickling. In the installed hydraulic components in the hydraulic lines disconnected or removed with a hose, receivership, rinse cover joints, constitute rinse loop. Acid pump acid into the circulating loop pickling. The pickling method is more advanced construction technology in recent years, with the pickling speed, good effect, the process is simple, easy to operate, reducing pollution on the human body and the environment, reduce labor intensity and shorten the pipeline installation period, resolve long lines and complex piping pickling difficult problem, and to avoid secondary pollution problems trough pickling easy assembly occurs, has been widely used in the construction of large hydraulic system piping.
Pickling formula and process piping will cause unreasonable tube wall can not be completely ex oxide, wall over corrosion, corrosion of the pipe wall and the tube again residual chemical reactions sediment and other phenomena.
Density of CS Pipe
Density is one of the numerous properties of steel. It is calculated by dividing the mass by the volume. Steel comes in many different forms. Density is calculated by dividing the mass by the volume. The density of carbon steel is approximately 7.85 g/cm3 (0.284 lb/in3).
There are many uses for steel. Stainless steel, for example, is used for surgical tools and kitchen utensils. It is a type of steel that contains low carbon levels and at least 10.5% of chromium. This results in corrosion resistance. Another kind of steel, tool steel, is used for metal cutting tools an drill bits because it is hard, but brittle. The amount of carbon in carbon steel determines the hardness of the steel. The more carbon it contains, the harder the steel. Carbon steel is often used for automobile parts.
Steel and its various forms have multiple uses around the world. The nature of the steel depends on its content, which results in varying densities. In most cases, the denser the steel, the harder it is.
The varying amounts of carbon, amongst other elements in each of the types of steel create a variety in densities or specific gravities. (Specific gravity or relative density is the ratio of a material’s density to that of water.)
There are five major classifications of steels: carbon steel, alloy steel, high-strength low-alloy steel, stainless steel and tool steel. Carbon steels are the most common, containing various amounts of carbon, produce everything from machines to bedsprings to bobby pins. Alloy steels have definite amounts of vanadium, molybdenum, manganese, silicon and cooper. Alloy steels produce gears, carving knives and even roller skates. Stainless steels have chromium, nickel amongst other alloy elements which sustains their color and reaction to rust. Stainless steel products include pipes, space capsules, surgical equipment to kitchen equipment. Last but not least, tool steels have tungsten, molybdenum amongst other alloy elements. These elements create the strength and ability of the tool steel products, which include parts for manufacturing operations as well as machinery.
Rolling mill of seamless carbon steel hot finished pipe:
The hot strip mill consists of a roughing mill and a finishing mill. Roughing mill components are semi-continuous, 3/4 continuous and all continuous types: 1. Semi-continuous type has a broken scale (remove oxide scale) frame and a reversible frame with vertical roller; 2.3/4 continuous type has two serially arranged racks in series; 3. The fully continuous type consists of 6-7 racks. The finishing rolling mills consist of 5-7 continuously arranged stands and coilers. The strip hot-rolling mill is named according to the length of the roll roll body, and the length of the roll body is 914 mm or more as a wide-band steel rolling mill. The work roll roll length of the finishing mill is 1700mm and it becomes a 1700mm strip hot rolling mill. This rolling mill can produce coils with a width of 1550mm. There are four methods for hot-rolling strips according to product width and production process: hot strip rolling of wide-band steel, reversible hot-rolling of wide-band steel, hot strip rolling of narrow-band steel, and hot-rolled strip steel using planetary rolling mill.
Magnetic of Carbon Steel Pipe
Residual magnetism causes and impact on quality of welding
When the gas pipeline construction and repair welding operations, sometimes magnetic blow phenomena affect the welding process. Forming a magnetic blow is the result of the presence of residual magnetism in the pipe metal. Typically, the magnetic induction and magnetic remanence divided into two processes. Magnetic induction in plants often produce tube links, such as: metal smelting, using electromagnetic crane for loading and unloading, pipe parked or garaged in a strong magnetic field, the magnetization is completed nondestructive inspection method, the pipe is placed close to power lines and so strong. Processes often produce magnetic welding operations during the assembly and the use of a magnetic holder, fixture and took DC welding pipes, such as: prolonged contact is connected to a DC power supply electric wire, bare wire segment or short-circuit pipe welding clamp and so on.
When welding with magnetic steel, often difficult to see the arc ignition, combustion undermine the stability of the arc, the arc of the deviation, the liquid metal and slag melt the spill from the weld pool in a magnetic field. In order to stabilize the welding process and improve the quality of the welded joint, the steel is magnetized to demagnetized before welding. It should be noted, to be welded steel pipe is difficult to achieve full demagnetization. Therefore, when the remanence is insufficient to affect the quality of welding, it allows welding.
Carbon steel pipe rusting
It is with a high corrosion resistance and adhesion,which does not contain harmful substances such as formaldehyde, benzene, heavy metals, environmental protection and the operator’s physical and mental health. it become into a transparent light filmcan be used as the ultimate anti-corrosion coating can also be used as anti-rust primer after drying. Closed film with excellent light, smooth, anti-discoloration resistance, corrosion resistance and high adhesion.
When carbon steel pipe rusting, and some contain a small amount of grease, it is recommended that after processing preparations, pre-treatment before the use of environmentally friendly degreasing rust one surface rust treatment products, or accessories are using coated anti-rust oil is isolated material contact with the air, but it is not the surface into the passivation film and isolated immediately after the expiration of the reservoir surface and the substrate will be a lot of rust layer, the role of microorganisms to provide a source of nutrition, use water-based dry ultrafine particles in the film’s blunt, dense material combination of anti-rust agents, anti-rust excellent performance, easy maintenance, environmental health, improve the quality of the workshop environment.
The details of steel pipe derusting methods:
- Component: surfactant, corrosion and preservatives.
- Features: iron, steel and other workpiece surface oil, corrosion and other one-time removal of the cleaning.
- Use: apply to the processes of iron and steel castings and alloy products, such as surface cleaning processing.
- Environmental Security: The solution for the water-soluble degreasing rust liquid; does not produce volatile toxic substances.
Magnetic elimination of carbon steel pipe process
- To determine the size and direction of the pipe left field;
- Select the degaussing method, system diagrams and technical means;
- Butt welded steel pipe or at the degaussing degaussing with the selected method;
- After checking the amount of residual magnetism after degaussing, to see if it meets the requirements.
- Machinery industry pipe. Such as aviation structural tube (round tube, oval tube, flat oval tube), automotive axle tube, axle tube, automobile tractor tube, tractor oil cooler tube, agricultural square tube and rectangular tube, transformer tube and bearing tube and so on.
- Petroleum geological drilling pipe. Such as: oil drilling pipe, oil drill pipe (square drill pipe and hexagonal drill pipe), petroleum tubing, casing and various oil pipe fittings, geological drilling pipe (core pipe, casing, active drill pipe, by hoop and pin connector, etc.).
- Chemical industry pipe. Such as: oil cracking pipe, chemical equipment, heat exchangers and pipelines, stainless acid-resistant tubes, high pressure pipelines for chemical fertilizers and pipelines for transporting chemical mediums.
- Pipeline. Such as: water, gas pipes, steam pipes with seamless pipe, oil pipelines, oil and gas trunk pipe. Agricultural irrigation faucet with pipe and sprinkler pipe and so on.
- Thermal equipment pipe. Such as the general boiler with boiling water pipes, superheated steam pipe, locomotive boiler with overheating pipe, smoke pipe, small pipe, arch pipe and high temperature and high pressure boiler tubes.
- Other departments with the pipe. Such as: container tube (high pressure gas cylinder tube and general container tube), instrument instrument tube, watch shell tube, injection needle and its medical equipment tubes.
Low Temperature Carbon Steel Pipe
Low temperature carbon steel pipe is medium carbon structural steel, cold steel plus low energy are good with good mechanical properties, and low prices, wide sources, so widely used. Its biggest weakness is the low hardenability, cross-sectional dimensions Japan is relatively high workpiece should not be used. Cold steel for low temperature operation, can withstand a certain low temperature impact. The commonly used standard is ASTM A333.
Low temperature quench pipe A3 + (30 ~ 50) ℃, in practice, is usually set to the upper limit. High quenching temperature to low temperature pipe heating speed, reduce surface oxidation, and can improve efficiency. The workpiece is uniform austenite, will require sufficient holding time. If the actual installed furnace capacity, would be appropriate to extend the holding time. Otherwise, there may be insufficient due to uneven heating caused by the hardness of the phenomenon. However, the holding time is too long, will also appear coarse grains, oxidation and decarbonization serious ills affecting quenching quality. We believe that such equipment is greater than the specified process documents furnace, the heating need to extend the holding time of 1/5.
Because the low temperature steel hardenability is low, it should be large cooling rate of 10% salt solution. After the workpiece into the water, it should hardenability, but not chilled, if in cold salt water penetration, it is possible cracking of the workpiece, it is because when the workpiece is cooled to about 180 ℃, the rapid transformation of austenite horse s body tissue caused by excessive stress due. Therefore, when hardened steel rapid cooling to the low temperature region, it should take slow cooling method. As the water temperature is difficult to grasp, accountable experience to operate, when to stop dithering artifacts in the water, the water can be air-cooled (eg oil cooler can be better). In addition, the work should move into the water should not be static, should be in accordance with the geometry of the workpiece, as the rules of sport. Stationary cooling medium plus stationary workpiece, resulting in uneven hardness, stress uneven leaving large deformation of the workpiece, and even cracking.
Cold steel pieces quenched hardness after quenching should reach HRC56 ~ 59, lower section of the possibility of some large, but not less than HRC48, otherwise, it shows the work has not been fully hardened tissues may occur even ferrite sorbitic Organizations, such organizations tempered, still retained in the matrix, which was not quenched purposes. Cryogenic tempering steel after quenching, the heating temperature is usually 560 ~ 600 ℃, hardness is HRC22 ~ 34. Because the goal is to get quenched mechanical properties, so the relatively wide range of hardness. But drawing hardness requirements, it is necessary to adjust by drawing tempering temperature to ensure hardness. For example, some cold steel shafts require high strength, hardness is high; while some gear, shaft parts with keyway, because after quenching but also for milling, insert processing, hardness requirements will be lower. About Tempering time, depending on the hardness and size of the piece, we think, depends on the hardness after tempering tempering temperature, tempering time with little to do, but must return through the general overall at the workpiece Tempering Time more than one hour.
ERW carbon steel pipe vs spiral pipe
First, the difference between the production process
ERW carbon steel pipe is the hot rolled coil through the continuous roll forming, the use of high-frequency current skin effect and proximity effects, so that the edge of the coil heat fusion, pressure in the squeeze roller under pressure welding to achieve production. Therefore, erw carbon steel pipe residual stress is small, through the weld heat treatment, sizing, straightening, water pressure and other processes, the residual stress to further release and reduce. Practice has proved that erw carbon steel pipe in the storage and use of residual stress on the steel pipe does not affect. Without any welding wire, the weld in the physical properties and chemical composition with the plate exactly the same. The quality of the erw carbon steel pipe depends on the quality of the sheet.
Spiral steel pipe through the unit spiral rotary welding wire welding together, the steel plate through the spiral rotation, so that the geometric stress is more complex, and some even reached the yield limit of the steel plate, the spiral tube after the formation of a larger residual stress, the residual stress is tensile stress. And the steel pipe by the internal pressure, the wall also produce ring tensile stress, the two superimposed, so that the ability to weaken the steel pipe. The use of the process more insecure. The steel plate is welded together by a wire containing chemical composition, and bubbles and weld bead cracks are likely to occur during the welding process. So that the weld and the base metal in the physical properties and chemical composition is clearly different. It is easy to produce great concentration stress in the joint with the base metal. In the welding process, the heat effect is large, and the hardness is high.
Second, the difference between raw materials
ERW carbon steel pipe used in the raw materials are produced by the regular hot-rolled coil, chemical composition and physical properties are more stable.
Most of the spiral pipe plant used for low-grade hot-rolled strip, chemical composition and physical properties and instability, internal defects and impurities more. Only in the oil and petrochemical system within the large spiral pipe manufacturers using regular hot rolled coil to manufacture steel pipe in order to ensure quality and safety.
Third, the procurement costs and procurement difficulties
Oil and petrochemical system of large steel pipe production of spiral steel pipe, its advantages are mainly concentrated in large diameter steel pipe manufacturing, manufacturing costs are relatively low. However, for small and medium diameter (Φ114mm ~ Φ355.6mm) of the steel pipe, the manufacturing cost is higher, the average higher than the ERW steel pipe 8% to 15%.
Large spiral steel pipe plant often do not produce small diameter spiral steel pipe, procurement more difficult. Small and medium diameter erw carbon steel pipe, due to the large number of manufacturers, very easy to purchase.
Fourth, the steel pipe geometric size
- ERW carbon steel pipe geometric size of the higher accuracy; and spiral welded pipe geometry accuracy is low, resulting in on-site construction of the weld weld docking difficulties.
- ERW carbon steel pipe weld coefficient is 100%; spiral welded pipe weld coefficient of 130% -200%. The length of the spiral pipe is much longer than that of the ERW steel pipe, and the defect rate is also increased.
- ERW carbon steel pipe within the weld is relatively close to zero, the naked eye is not visible; spiral steel pipe inside and outside the surface must be left about 0.3 mm high (which is determined by the production process). The weld is so high that there is a gap between the coating (3PE) and the pipe, which makes the corrosion resistance of the steel pipe greatly reduced.
- Due to the existence of spiral steel pipe gap, the transmission of high-speed fluid there will be a large disturbance, increase the flow resistance, reduce the transport efficiency of the pipeline. ERW carbon steel pipe wall is smooth, there is no such problem.
Source: China Carbon Steel Pipes 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.)
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