At present, steel extrusion units in the world, in addition to a small number of extrusion processing profiles, most of the extrusion units are used to produce steel pipe, of which the main variety is stainless steel seamless pipe. Compared with the production methods such as rolling (longitudinal rolling and cross rolling), the extrusion process is characterized by the three direction compressive stress in the process of metal deformation. Under the optimum stress state, the stainless steel seamless pipe with large variety and large deformation resistance can get better deformation, internal and external surface quality and metallographic structure.
With the improvement of vertical hydraulic piercing equipment, the wall thickness deviation of the extruded seamless stainless steel pipe can reach 5%~7%. In addition, extrusion mould is simple, manufacture and easy replacement, suitable for small batch and various specifications of stainless steel seamless pipe production. The extrusion unit can also pipe production specifications wide, 1 sets of 50MN (5000t) of the extruder unit can produce specifications is 25~245mm diameter stainless steel seamless pipe, needs to adapt to the market and meet is much higher than the other mill.
With the biggest advantage of extrusion production of stainless steel seamless pipe is able to direct the use of continuous casting as raw materials, so as to ensure the stability of product quality, variety replacement and flexible, can be directly produced by hot extrusion pipe, also can produce a variety of special-shaped stainless steel seamless pipe.
However, the stainless steel seamless pipe produced by extrusion process has an obvious drawback, that is, low yield. In order to improve the yield, foreign manufacturers have improved the production process. For the high demand varieties, the production process of pre drilling, hydraulic punch reaming and extrusion pipe forming is usually adopted.
For the cold processing of raw materials for common requirements for pipe according to use different production processes specific circumstances, such as small size stainless steel seamless pipe billet directly in the vertical hydraulic punch punch and extruded pipe; medium size stainless steel seamless pipe with blank as far as possible pre drilled holes, vertical hydraulic reaming and extrusion punch into large size stainless steel pipe; the seamless pipe blank pre drilling larger holes, directly into the extrusion pipe.
It can be clearly seen that the production of finished pipes by extrusion and the provision of steel pipes for cold processing are a more economical and practical production process for stainless steel seamless pipes which are now widely used in foreign countries.
Source: China Stainless Steel Pipes Manufacturer - Yaang Pipe Industry Co., Limited (www.yaang.com)