How is the extrusion processing of seamless stainless steel pipes implemented

Through improvements to the vertical hydraulic piercing device, the wall thickness deviation accuracy can reach 5% to 7%. The extrusion die is simple to design, manufacture, and replace, making it suitable for small-batch, multi-specification production of seamless stainless steel pipes. This extrusion unit can also produce various types of steel pipes; a 50MN (5000t) extrusion unit can produce steel pipes with specifications of 25-245mm, making it more suitable for market demand than other rolling mills.

The biggest advantage of using extrusion to produce seamless stainless steel pipes is that it allows for the direct use of continuously cast billets as raw materials, ensuring stable and safe product quality. It also allows for flexible product variety changes, enabling the direct production of hot-extruded finished seamless stainless steel pipes and improving the production of various irregular cross-section seamless stainless steel pipes.

However, extrusion-produced seamless stainless steel pipes also have a significant drawback: low yield. To improve the yield, foreign manufacturers have improved the production process. For certain varieties, a common production technology is pre-drilling, hydraulic piercing machine reaming, and extrusion into pipes. Cold-worked raw material pipes can be produced using different processes depending on the specific circumstances: small-sized steel pipes are directly punched on a vertical hydraulic piercing mill and extruded using solid billets; for medium-sized steel pipes, billets should be pre-drilled with small holes as much as possible, while for large steel pipes, billets should be pre-drilled with large holes, and then the billets for large steel pipes are directly extruded into pipes by an extruder.

Seamless stainless steel pipes produced using the cold drawing and cold rolling processes described above can only be considered semi-finished products. Their precision grades are quite low, often failing to meet the requirements of customers. For example, seamless stainless steel pipes may have uneven wall thickness, dents, scratches, spots, or pits on the internal and external surfaces, requiring continuous grinding.

With the rapid pace of industrialization in my country, there is a higher demand for seamless stainless steel pipes. Only by improving stainless steel processing techniques and comprehensively considering factors such as production scale and capital investment, and selecting a suitable seamless stainless steel pipe production process, can the quality of seamless pipes be guaranteed and the economic benefits of enterprises be improved.