Seamless steel pipe refers to the use of seamless tube or steel manufacturing without weld pipe fittings. In recent years, due to the improvement of welded pipe manufacturing, some in the engineering design of welded pipe manufacturing pipe fittings is often used, especially the thin wall stainless steel weld pipe manufacturing pipe proportion increase quickly. For stamping process adopted by the welded tubes and seamless pipe is roughly same, the seamless pipe forming process of reason described here can also be applied to welded pipe manufacturing the pipe.
(1) the seamless elbow
A pipe bend is used in the pipe bend. In the pipeline system used by all the pieces, took the largest share, of about 80%. Usually, on different materials or wall thickness of the elbow to select different forming technology. Commonly used at present, the factory of the seamless bend forming process with heat, stamping, extrusion, etc.
A. hot pushing forming
Hot push bend forming technology is to use special elbow push system core machine, mold and heating device, to set on the mould of billet in pushing forward movement, under the impetus of the machine in motion is heated and hole enlargement and forming process. Hot push bend forming diagram as shown in figure.
1 – mold 2 -, 3-4 – heating device is taking shape of elbow
Hot bend forming schematic diagram
Hot push bend deformation characteristics are based on volume before and after plastic deformation rule of metal materials determine the pipe diameter, pipe diameter bend diameter, through the core module and control the deformation of the process, make the inner arc compressed metal flow, the compensation to other parts of the thinned by hole diameter, wall thickness uniform Angle is obtained.
Hot push bend forming technology has a good appearance, uniform wall thickness and continuous operation, suitable for the characteristics of mass production, thus become the main forming methods of carbon steel, alloy steel elbow, and also the application in some of the specifications of the stainless steel elbow forming.
Forming process of the heating mode with intermediate frequency or high frequency induction heating (heating can be multiple times or lap), flame heating and reverberatory furnace heating, adopt what kind of heating mode according to the condition of forming product requirements and energy.
Stamping elbow is first applied to the forming process of the mass production of seamless elbow, at present, the commonly used in the production of the specifications of the elbow has been replaced by a hot method or other forming process, but in some of the specifications of the elbow because of production volume, wall thickness is too thick or less
When the products have special requirements are still in use. Elbow stamping elbow is used to outer diameter of the same tube billet, use press press forming directly in the mould. Stamping elbow forming diagram as shown in figure
1-2 – end of upper die mold 3-4 – bend 5 – lower die inner core
Stamping elbow forming schematic diagram
As shown, in front of the press, the tube billet is put on a mold, the mold filling and end into the pipe, the upper die downward movement began to suppress, through external constraints and internal model of the supporting role of bend forming.
Compared with the hot pushing process, the appearance of the stamping forming quality is better than the former; Stamping elbow outer arc in the tensile state during forming, compensate, and no other parts excess metal so the outer arc of wall thickness thinning is about 10% or so. But due to apply to the individual production and the characteristics of low cost, so the stamping elbow process used in small batch, more thick wall elbow manufacture.
Cold stamping and hot stamping stamping elbow points two kinds, usually according to the nature of materials and equipment capacity selection of cold or hot stamping.
C. cold extrusion forming
Cold extrusion of bend forming process is the use of dedicated elbow forming machine, pipe to be included in the external formwork, upper and lower mould clamping, under the impetus of the push rod, tube billet model along the internal model and reserved clearance sports and forming process.
Cold extrusion of bend forming
Using die cold extrusion process inside and outside the elbow and good appearance, uniform wall thickness, size deviation is small, so for the stainless steel elbow especially thin wall stainless steel elbow forming more made by this technology. This new process used by internal and external mold precision demand is high; For pipe wall thickness deviation is more demanding.
D. other forming methods
Except the forming process of the above three kinds of commonly used seamless pipe bend forming and using the tube billet after extrusion to outside, and inside the tube billet passed ball plastic forming technology. But this process is relatively complex, the operation of trouble, not equal to the process, and the forming quality is less used.
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)