What are Stamping Elbows
The stamping elbow is formed by punching a half-shaped elbow with a stamping die of the same material as the pipe, and then welding the two half-ring elbows in pairs. Due to the different welding standards of various types of pipes, it is usually fixed by semi-finished products by group-to-spot welding. The on-site construction is welded according to the grade of pipe welds. Therefore, it is also called two-half welding elbows.
Because the stamping elbow has good comprehensive performance, it is widely used in chemical engineering, construction, water supply, drainage, petroleum, light and heavy industry, refrigeration, sanitation, plumbing, fire protection, electric power, aerospace, shipbuilding and other basic projects.
The material of the stamping elbow is made of carbon steel, stainless steel or alloy steel. The carbon steel stamping elbow is cheap and large in use. The elbow of alloy steel is used in a special position.
The difference between the stainless steel elbow and the carbon steel elbow is mainly due to the difference in material. The chemical composition of the stainless steel stamping elbow will keep the surface of the elbow from rusting for a long time and is not easily corroded.
Stainless steel is characterized by stainless steel and corrosion resistance, and has a chromium content of at least 10.5% and a carbon content of at most 1.2%.
The austenitic stainless steel base is mainly composed of austenite structure (γ phase) of a face-centered cubic structure, and is non-magnetic, and is mainly strengthened by cold working (and may cause certain magnetic properties) of stainless steel.
Austenitic-ferritic (duplex) stainless steel
The matrix has both austenitic and ferritic two-phase structure (in which the content of less phase is generally greater than 15%), and it is magnetic and can be strengthened by cold working.
The ferritic stainless steel matrix is mainly composed of a ferrite structure (α phase) of a body-centered cubic crystal structure, is magnetic, and generally cannot be hardened by heat treatment, but cold working can make it slightly strengthened stainless steel.
The martensitic stainless steel matrix is a martensitic structure and has a magnetic property, and the mechanical properties of the stainless steel can be adjusted by heat treatment.
Precipitation hardening stainless steel
The matrix is austenitic or martensitic, and can be hardened (strongly) stainless steel by precipitation hardening (also known as age hardening).
- Carbon steel: ASTM/ASME A234 WPB, WPC
- Alloy: ASTM/ASME A234 WP 1-WP 12-WP 11-WP 22-WP 5-WP 91-WP911, 15Mo3 15CrMoV, 35CrMoV
- Stainless steel: ASTM/ASME A403 WP 304-304L-304H-304LN-304N
- ASTM/ASME A403 WP 316-316L-316H-316LN-316N-316Ti
- ASTM/ASME A403 WP 321-321H ASTM/ASME A403 WP 347-347H
- Low temperature steel: ASTM/ASME A402 WPL3-WPL 6
- High Performance Steel: ASTM/ASME A860 WPHY 42-46-52-60-65-70
- Cast steel, alloy steel, stainless steel, copper, aluminum alloy, plastic, argon leaching, PVC, PPR, RFPP (reinforced polypropylene).
The internationally accepted standard is the US national standards ANSI B16.9 and 16.28. The standard outer diameter range is 1/2 〃 ~ 80 〃, 26 〃 to 80 〃 are stamped with steel and then welded. The wall thickness can be up to 60mm and the minimum is 1.24mm. The most used steel grades are carbon steel (20#), alloy steel and stainless steel, with a total of 24 steel grades. The CrMo steel used in the boiler is like 15Cr, which is relatively large. The three-way, the outer diameter ranges from 2.5〃-60〃, from 26〃-60〃 to the welded tee. The wall thickness is 28-60mm. Size specifications range, conventionally said first big head specifications, then small head specifications, big head minimum 0.75 〃, small head minimum 0.5 〃, big head maximum 60 〃, small head maximum 48 〃, 20-60 〃 for welding, wall thickness 2.8 -45mm.
Chinese national standard:
Petrochemical standards for elbows:
- SH 3408-1996
- SH 3409-1996
Chemical standard for elbows: HG/T 21635-1987
Elbow power standard: DL/ T695
Elbow oil standard: SY/T 0510
German standard for elbows: DIN2605
Japanese standard for elbows: JIS
Marine standard for elbows: GB/T10752-1995
Chemical standard for elbows: HG21631-1990
Stamping elbow thickness standard
In the process of the stamping elbow after the arrival of the goods, the thickness of the stamping elbow is increased at the same time. The thickness of the general stamping elbow is severely exceeded, and it needs to be calculated according to the actual measurement.
In the process of calculation, in the process of general accounting wall thickness, in the process of general pipeline equipment, whether the interface thrust and thrust are generally qualified, of course, whether the pipeline docking is set properly. In the calculation of the pipe, the stress enhancement factor and the flexibility factor should be calculated. Of course, when recalculating the check, calculate the wall thickness of the pipe with the stress enhancement factor at the punch elbow, where the wall thickness is converted by the weight of the elbow. The straight pipe which is to be unfolded along the center line of the punching elbow ensures that the weight of the unfolded straight pipe is the same as the weight of the punching elbow, and the converted wall thickness of the punching elbow is the weight of the punching elbow.
Use of stamping elbow
A connecting pipe commonly used in pipe installation, connecting two pipes with the same or different nominal diameters to make the pipe turn at a certain angle.
- (1) The production efficiency of stamping processing is high, and the operation is convenient, and it is easy to realize mechanization and automation. This is because stamping relies on die and stamping equipment to complete the processing. The number of strokes of ordinary presses can reach dozens of times per minute, and high-speed pressure is required. It can reach hundreds or even thousands of times per minute, and it is possible to get one stamping part per stamping stroke.
- (2) Stamping generally has no chip waste, less material consumption, and no need for other heating equipment, so it is a material-saving, energy-saving processing method, and the cost of stamping parts is low.
- (3) Stamping can process parts with large size range and complicated shape, such as stopwatches as small as watches, as large as car longitudinal beams, covering parts, etc., plus the cold deformation hardening effect of materials during stamping, the strength and rigidity of stamping Higher.
- (4) Since the die ensures the size and shape accuracy of the stamping part during stamping, and generally does not damage the surface quality of the stamping part, and the life of the die is generally long, the quality of the stamping is stable, the interchangeability is good, and the characteristics are “ exactly the same”. .
The forming process of the stamping elbow is complicated, and it needs to be welded according to different materials and uses, and gradually formed under a certain pressure. The forming of the stamping elbow needs to be carried out according to a certain process, and the corresponding process is strictly followed, otherwise the quality of the stamping elbow produced will be produced. A circular ring shell can be cut into 4 90 ° elbows or 6 60 ° elbows or other sizes of elbows as needed. This process is suitable for
Any large-scale push elbow that produces a bend with a median diameter of elbow and an inner diameter of the elbow greater than 1.5D is an ideal way to make large push elbows.
This process molding method is used in the production of different elbows and exhibits good use value in different fields, so that the process has a good value in different elbow production.
The advantages of the forming process of large stamping elbows are mainly reflected in the following aspects:
- (1) It is not necessary to use the tube blank as a raw material, which can save the cost of the pipe making equipment and the mold, and can obtain a push elbow of any large diameter and relatively thin wall thickness. The material of the stamping elbow is special, and it is not necessary to add the raw material of the tube blank, and it is easy to control during processing.
- (2) The blank for processing the punching elbow is a flat plate or a developable curved surface, so the material is simple to cut, the precision is easy to ensure, the assembly and welding are convenient, the raw materials are easily controlled during processing, the operation is relatively simple, there is no complicated process, and the welding and assembly are convenient.
- (3) Due to the above two reasons, the manufacturing cycle can be shortened and the production cost is greatly reduced. Because it does not require any special equipment, it is especially suitable for processing large punching elbows on site.
How is the stamping elbow stamped?
Stamping forming elbow is the earliest forming process for mass production of seamless elbows. It has been replaced by hot pushing or other forming processes in the production of elbows of common specifications, but in some specifications of elbows due to the number of production Less, the wall thickness is too thick or too thin.
The product is still in use when it has special requirements. The stamping of the elbow is performed by using a tube blank equal to the outer diameter of the elbow, and is directly press-formed in the mold using a press.
Before the stamping, the tube blank is placed on the lower mold, the inner core and the end mold are loaded into the tube blank, the upper mold is moved downward to start pressing, and the elbow is formed by the constraint of the outer mold and the support of the inner mold.
Compared with the hot push process, the appearance quality of stamping is not as good as the former; when the punch elbow is in the stretched state when forming, there is no excess metal in other parts to compensate, so the wall thickness at the outer arc is about 10% thinner. . However, due to the characteristics of single-piece production and low cost, the stamping elbow process is mostly used for the manufacture of small batches and thick-walled elbows.
Stamping elbows are divided into cold stamping and hot stamping. Cold stamping or hot stamping is usually selected according to material properties and equipment capabilities.
The forming process of the cold extrusion elbow is to use a special elbow forming machine to put the tube blank into the outer mold. After the upper and lower molds are closed, the blank is reserved along the inner and outer molds under the push of the push rod. The gap moves to complete the forming process.
The elbow manufactured by the inner and outer mold cold extrusion process has beautiful appearance, uniform wall thickness and small dimensional deviation, so the stainless steel elbow, especially the thin-walled stainless steel elbow forming, is mostly manufactured by this process. The precision of the inner and outer molds used in this process is high; the wall thickness deviation of the tube blank is also demanding.
The stamping elbow is the earliest elbow production process. At present, this process is only for the production of elbows with large thickness, high pressure, hard material and push-and-limit. Here I will introduce you to the technical essentials and precautions for the production of stamping elbows.
The production of stamping elbow can be produced by the combination of several machines such as press, base mold, upper pressing mold and filling mold. The choice of press must be that the pressure is absolutely greater than the deformation of the elbow. The design of the pressing die and the base die, because the original process is very late, the die is also very inaccurate, the length of the die must be greater than the length of the elbow to ensure the machining allowance of the punching elbow, and the design of the filling die is more important. Now it is the mold made by CNC lathe. One thickness, one model, one mold, guarantees the appearance of the elbow in the caliber and the appearance of the elbow. But the original problem is not solved. The original stamping elbow is a caliber with a mold, regardless of thickness. The caliber of the elbow made in this way is very difficult to guarantee. The production of the punching elbow is only for the thick wall and the alloy, and the carbon steel is not the main one.
The heating temperature is also an important factor in the production of stamping elbows. The original production is almost directly burned out by the naked eye, but the human eye is sometimes very difficult to grasp the temperature, especially when the temperature is high. The head will not only drop a lot of oxide scales in the furnace but also reduce the thickness, which will lead to the sale of the elbows. The higher the temperature, the softer the elbows. When the processing is slightly stressed, the shape of the elbows is deformed. Also not good control. A little bit lower in temperature is a matter of increasing stress.
Post-shaping: After the stamping elbow is pressed, the approximate appearance has come out, and the need for the mouth of the mouth, the grinding of the mouth and the like is a delicate work. The appearance of the punching elbow depends on this.
At present, the production of stamping elbows is mainly alloy or thick-walled. The push elbow has long replaced the stamping elbow, but many high-pressure alloy elbows continue the stamping process. The stamping elbows are made of materials. The special hardness and the special requirements of the alloy must be heat treated.
The treatment of stamping elbow is: using the method of solid metal phase transformation, using heating, heat preservation and cooling methods to improve and control the required microstructure and physical properties (physical, chemical and mechanical properties).
The heat treatment of the stamping elbow is nothing more than the technical requirements such as the required hardness or tensile strength or yield resistance.
Normalizing is the treatment of heating. The current normalizing treatment includes electric heating furnace, coal heating or fuel heating. This is also the most common heat treatment method. It is required that the strict stamping elbow needs to go through this procedure. Even if the stamping elbow is thermoformed, the temperature and time required for normalizing are generally not very long. It is required to achieve the plasticity of the customer’s pressing, but in order to fully meet the original hardness of the raw material, it must be re-run. Heat treatment.
Tempering, the process of heating the stamping elbow to a certain temperature and holding it in the air for a period of time to slowly cool it, the process is to make the internal binding of the tissue more compact.
Quenching, the process of heating the stamping elbow to a specified temperature and then putting it into oil, or water, or rapidly cooling it in a specific medium, is referred to as quenching.
Source: China Steel Elbows 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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Please notice that you might be interested in the other technical articles we’ve published:
- Difference Between A Pipe Elbow And A Pipe Bend
- What is a pipe elbow
- How to get high quality pipe elbow
- Use and maintenance of stainless steel elbows
- Seamless Steel Elbow VS Welded Steel Elbow
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- An Simple Introduction to Stamping Elbows (Part One)
- An Simple Introduction to Stamping Elbows (Part Two)