Technological process and forming principle of elbow

Seamless elbow: elbow is used for pipe bend of a pipe. In all the pipe fittings used in the pipe system, the largest proportion, about 80%. In general, different forming processes are selected for different materials or wall thicknesses. At present, the common seamless elbow factory has hot stamping forming process, extrusion, etc..

A. hot forming

Hot bend forming process is the special Elbow push processing machine, a core mold and a heating device, which makes in the mold blank in pushing mechanism driven by forward motion and in the movement is heating, expanding diameter and bending forming process. The deformation characteristics of the hot pushing elbow is based on the metal plastic deformation before and after constant volume law to determine the tube diameter, the tube diameter less than the diameter of the elbow, the through mandrel control the blank deformation process, the arc by the compression of the metal flow, compensation for expanding and other parts of the thin, in order to get uniform wall thickness of elbow.

The hot pushing elbow forming process has the advantages of beautiful appearance, uniform thickness and continuous operation, suitable for mass production. Therefore, it becomes the main processing method of carbon steel, alloy steel elbow, and is also used in some specifications of stainless steel elbow forming.

The heating mode of the forming process has an intermediate frequency or high frequency induction heating (heating ring can be a multi ring or a ring), the flame heating and the reflective furnace heating, the heating mode of the product requirements and energy situation decision.

B. stamping forming

Stamping elbow is the earliest application in mass production, the forming process of seamless elbow, at present, in the production of the elbow of the commonly used specifications has been hot pushingpipe method or other forming techniques of alternative, but in some specifications of elbow due to less number of production, wall thickness too thick or too thin. Products are still in use when special requirements. The bending of the elbow is equal to the diameter of the elbow, which is directly pressed and shaped by the press. A sketch of the forming of the stamping elbow is shown in Fig.

Before stamping, the tube is placed in the lower mold, the inner core and the end of the tube into the tube blank, the upper mold is pressed down, and the elbow is formed by the external and internal model. Compared with the hot pushing process, stamping the appearance quality is inferior to the former; stamping elbow in the forming of arc in tension and other parts of excess metal is not the compensation, outside the arc of the wall thickness reduction thin about 10%. However, due to the characteristics of single piece production and low cost, it is suitable for the manufacture of small batch and thick wall elbow.

Stamping elbow is divided into two kinds of cold stamping and hot stamping, usually according to the material properties and the ability to choose cold stamping or hot stamping.

The forming process of cold extrusion elbow is the use of special elbow forming machine, the tube blank is placed in the outer mold, the upper and lower die, the push of the push rod, the tube billet along the inner mold and the outer mold to reserve the gap between the completion of the forming process. Figure 15-8 a picture of a stainless steel elbow in a manufacturing plant before and after extrusion.

The shape of elbow is beautiful, the wall thickness is uniform and the size deviation is small, so the process is made by using this technology for the stainless steel elbow, especially the thin wall. This process is used in internal and external mold accuracy requirements; the wall thickness deviation of the tube is also relatively harsh.

C. other forming methods

In addition to the outside of the three common forming process, seamless elbow forming as well as the use of tube billet is extruded to the outside of the die, again through the tube blank pigging plastic forming process. However, this process is relatively complex, operational trouble, and the forming quality is not as good as the preceding process, so it is seldom used.

America American Standard standard fittings

American Standard

B16.9 ASME/ANSI factory made of forged steel welded pipe

B16.11 ASME/ANSI socket welding and threaded Forged Fittings

ASME/ANSI B16.28 steel butt welding of small radius elbow and back bending

B16.5 ASME pipe flanges and flange fittings

SP-43 MSS stainless steel welded tube parts

SP-83 MSS socket welded and threaded joint

MSS SP-97 the whole socket welding and butt welding ends, threaded reinforcing type socket

B16.3-1998 ASME malleable cast iron threaded pipe

4 China pipe fittings standard

GB/T12459-2005 seamless steel butt welding fittings

GB/T13401-2005 steel tube parts

SH 3408 seamless steel butt welding fittings

SH 3409 steel plate for welded pipe

SH 3410 forged steel socket welding fittings

GB/T10751-1995 ship steel tube for welding head

Pipe standard

1 the safety management and supervision of the [1996]140, the original labor department

2 national quality inspection pot [2002]235 pressure vessel pressure vessel design unit qualification licensing and management rules

3 the Quality Supervision Bureau pan [1999]143 paper notice on strengthening liquefied petroleum gas station safety supervision and management

4 quality and technical supervision pot word [1999]59, on the implementation of the "on the strengthening of the liquefied petroleum gas station safety supervision and management of the notice" views of the relevant issues

5 the safety technical supervision of the former Ministry of labor [1996]276

6 [1997]74 No. 1, the Ministry of labor and water boiler safety technology supervision code *

7 the safety technology of [1993]356, the former Ministry of labor, and organic heat carrier furnace

8 the Quality Supervision Bureau issued the document No. [1999]154 boiler pressure vessel safety technology *

9 GB4962-1985 hydrogen use safety technical specification

10 GB6222-1986 industrial gas safety regulations

11 GB11984-1989 chlorine safety regulations

12 GB13348-1992 liquid petroleum products

13 SY6186-1996 oil and gas pipeline safety regulations

14 SY5737-1995 oil pipeline transportation safety requirements

15 DL/T561-95 thermal power plant water vapor chemical supervision guide

16 DL/T709-1999 pressure steel pipe safety testing technology