There are more than 60 sets of extrusion units in the world. Except for a few for profile extrusion, 70% of the units are used for the production of steel pipes. The main type is stainless steel pipes. Compared with the rolling (longitudinal and cross-rolling) production methods, the extrusion method is characterized by three-way compressive stress during metal deformation. Under this optimal stress state, for stainless steel tubes with large steel numbers and large deformation resistance, good deformation, internal and external surface quality and metallographic structure can be obtained.
The improvement of the vertical hydraulic perforation process equipment can make the deviation accuracy of the wall thickness of the waste pipe after extrusion reach 5%~7%. The extrusion die is simple, easy to manufacture and replace, and is suitable for the production of small batch and multi-size stainless steel pipes. The extrusion unit can also produce steel pipes with a wide range of specifications. One set of 50MN (5000t) extrusion units can produce steel pipes with a specification of Φ25~245mm, which is far more adaptable to market demand than other rolling mill units.
The biggest advantage of using stainless steel seamless pipe
by extrusion method is that it can directly use continuous casting blank as raw material. The product quality is stable and the variety is flexible. It can directly produce hot extruded finished pipe, and can also produce various shaped stainless steel pipes. However, the disadvantage of producing steel pipes by extrusion is that the finished product rate is low. In order to increase the yield, foreign manufacturers have improved the production process. For the high-demand varieties, the production process of pre-drilling, hydraulic punching machine reaming and extrusion into tubes is generally adopted.
For the general requirements of the cold-worked raw material pipe, different production processes can be used according to the specific conditions: the small-size stainless seamless steel pipe
is perforated and extruded into a pipe directly on the vertical hydraulic punching machine; the blank for the medium-sized steel pipe is pre-drilled as much as possible. The vertical hydraulic punching machine reams and extrudes into a tube; the blank used for the large-size stainless steel seamless pipe is pre-drilled into a large hole, and directly enters the extruder to be extruded into a tube. Obviously, the production of finished pipes by extrusion and the provision of waste pipes for cold processing are a relatively economical and practical production method widely used in foreign hot-processed stainless steel pipes.