Description of standard number SH3406 petrochemical steel pipe flange SH3408 steel butt welded seamless pipe fitting SH3409 forged steel socket welded pipe fitting SH34 10 steel plate butt welded pipe fitting
Pipe fittings shall be subject to national standards.
Description of standardNo. GB 12459 Steel butt-welded seamless pipe fittings GB/T 1340 1 steel plate butt-welded pipe fittings GB/T 14383 Forged steel socket-welded pipe fittings GB 912-9/KLOC- Gasket fittings of flange cover and flange shall comply with the petroleum standard in the standard: the standard number describes SY/T05 10- 1998 steel butt welded pipe fittings SY/T5257-2004 steel elbow.
process flow
Seamless elbow: elbow is a kind of pipe fitting used for pipe turning. Among all the pipe fittings used in the pipeline system, the proportion is the largest, about 80%. Usually, for elbows with different materials or wall thicknesses, different forming processes are selected. At present, the common forming processes of seamless elbow are hot pushing, stamping and extrusion.
A. hot push molding
Hot-push elbow forming process is a process that uses special elbow thruster, mandrel and heating device to make the blank sheathed on the die move forward under the push of the thruster and expand and bend under heat during the movement. The deformation characteristic of hot push elbow is to determine the diameter of tube blank according to the law of constant volume of metal material before and after plastic deformation, and the diameter of tube blank used is smaller than the diameter of elbow. The deformation process of the blank is controlled by the mandrel, so that the compressed metal at the inner arc flows and is compensated to other parts with enlarged diameter and thinner thickness, thus obtaining an elbow with uniform wall thickness. Hot-push elbow forming process has the characteristics of beautiful appearance, uniform wall thickness and continuous operation, which is suitable for mass production. Therefore, it has become the main forming method of carbon steel and alloy steel elbows, and is also applied to the forming of stainless steel elbows with certain specifications. The heating methods in the molding process include medium-frequency or high-frequency induction heating (the heating ring can be multi-turn or single-turn), flame heating and reverberatory furnace heating, and which heating method is adopted depends on the requirements of molded products and energy situation.
B. Stamping forming
Stamping elbow is the earliest forming process used in batch production of seamless elbow. At present, it has been replaced by hot pushing or other forming processes in the production of elbows with ordinary specifications, but in some specifications, the production capacity is small, and the wall thickness is too thick or too thin. The product is still in use when it has special requirements. The tube blank with the same outer diameter as the elbow is used for elbow stamping, and it is directly pressed into the mold by a press. The schematic diagram of stamping elbow is as shown in the figure. Before punching, the tube blank is placed on the lower die, the inner core and the end die are put into the tube blank, the upper die moves down to start pressing, and the elbow is formed through the constraint of the outer die and the support of the inner die. Compared with hot pushing process, the appearance quality of stamping is not as good as the former; The outer arc of the punching elbow is in tension during forming, and there is no extra metal to compensate other parts, so the wall thickness of the outer arc is reduced by about 10%. However, because stamping elbow technology is suitable for single-piece production and has low cost, it is mostly used for the manufacture of small batch 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 capacity. The forming process of cold extrusion elbow is to put the tube blank into the outer die with a special elbow forming machine. After the upper and lower dies are closed, the tube blank moves along the gap left between the inner die and the outer die under the push of the push rod to complete the forming process. Figure 15-8 is a picture of a stainless steel elbow before and after extrusion. The elbow made by cold extrusion process of internal and external dies has beautiful appearance, uniform wall thickness and small dimensional deviation, so this process is often used to make stainless steel elbows, especially thin-walled stainless steel elbows. The inner and outer dies used in this process require high precision; The wall thickness deviation of tube blank is also high. Provided by Konglv.com HVAC experts.
C. Other molding methods
In addition to the above three common forming processes, seamless elbow is also formed by extruding the tube blank onto the outer die and then forming it through the balls in the tube blank. However, this process is relatively complicated and troublesome to operate, and the molding quality is not as good as the previous process, so it is rarely used.