Current situation and development of seamless pipe technology and equipment
Since the 1980s, the implementation of the national reform and opening up policy has promoted the rapid economic development and promoted the progress of the seamless steel pipe industry. Seamless Stainless Steel Tube Mills production has also been rapid growth, the introduction of advanced technology and equipment, such as the first to introduce a 3500t extrusion machine, not only long legislation industrial stainless steel seamless pipe production technology and equipment into the world Advanced ranks, and as a squeeze production process Pathfinder to promote China's stainless steel seamless pipe process changes, was listed as the year China's stainless steel industry, one of 10 major events. For some important use of Stainless Steel Tube Mills, such as nuclear power plant (special specifications), the user more use of extrusion production for the main production, high-end Stainless Steel Tube Mills production gradually normalized; cold-rolled, cold-drawn tube production equipment introduction or Localization is too numerous to mention, the introduction of these seamless pipe production, so that China's seamless Stainless Steel Tube Mills technology and equipment level to the contemporary international level.
At present, China's Stainless Steel Tube Mills applications, "cold-rolled, cold-rolled hot-rolled" products, hot-rolled pipe production of Stainless Steel Tube Mills is mainly for cold processing to provide tube blank.
In the process technology, China's advanced equipment seamless steel pipe production line, most of which was built after 1990. Production process computer control, conical punching machine, roll full hydraulic pressure reduction technology, concentrated roll design, roll single drive, limit mandrel bar rolling, step core rod rolling and other advanced technology has been widely used. With the continuous improvement of the technology and equipment level of our country's seamless steel pipe industry, the production mode of Stainless Steel Tube Mills (including large diameter and thick wall) has also been diversified. There are mainly extruding unit, rolling mill unit, pipe jacking unit Rolling (perforation + cold rolling, cold drawing), hot rolling + cold rolling, cold drawing method and other production methods. In addition, there are a small number of other ways to produce, such as forging boring and other production methods.
Hot extrusion technology is one of the hot-working seamless Stainless Steel Tube Mills production process. Compared with the rolling production method, the extrusion method is characterized by the metal in the deformation process by the three-way compressive stress, in this best condition, for the deformation resistance, poor thermoplastic high-end Stainless Steel Tube Mills can get better inside and outside Surface quality and microstructure, suitable for the production of small quantities, multi-standard stainless steel tube, especially suitable for the production of inclined rolling machine difficult to process high-alloy pipe.
Although China's Stainless Steel Tube Mills production using "perforation + cold drawing, cold rolling" process more, but the use of extrusion production of stainless steel tube advantage is that you can directly use the continuous casting as raw materials, product quality is relatively stable, flexible varieties can be replaced Direct production of hot extrusion finished product tube, can also produce all kinds of profiled stainless steel tube. Production of large diameter (thick-walled) Stainless Steel Tube Mills in addition to a small amount of "perforation + Pielberg rolling" process (including the top pipe unit), basically using hot extrusion process.
With the development of high-speed, automated, large-tonnage extruder, high-strength, high-toughness hot molds and other related technologies, the use of extrusion production of Stainless Steel Tube Mills or cold processing to provide a pipe, is the current hot-working Stainless Steel Tube Mills A better and economical way. In particular, the production of difficult to deformation of the Stainless Steel Tube Mills, high-alloy steel pipe, thick-walled tube has been rapid development.
In the domestic, stainless steel tube with inclined rolling more perforation, not only commonly used austenitic stainless steel, and difficult to deform the duplex stainless steel can also be produced in the skew rolling machine, through a variety of rolling mill (longitudinal or inclined) Can be rolled thinner wall, cold rolling for the cold rolling to provide raw materials, reduce the cold drawn (rolling) pass, can improve productivity and finished product rate, cost reduction benefits.
The more common devices include Ф50, Ф90, Ф250 series hot rolling piercing units. Another TZC200 tapered roller punching unit, using modular rack, tapered roller perforation, full hydraulic fast roll and digital CNC feed angle adjustment technology, at the leading level, to the contemporary international level, in some large domestic stainless steel Factories have applications.
In the process of forming the pipe, cold drawing and cold rolling in the actual production of the same effect, produced by the seamless tube have their own advantages.
More than 65% of Stainless Steel Tube Mills is made by cold working, cold processing technology basically has three kinds: cold drawing process, cold rolling process, cold rolling + cold drawing process. Cold-processing Stainless Steel Tube Mills mostly use cold-rolled + cold-drawn production process, and cold-based, cold drawn for the auxiliary.
At present, the world cold rolling and cold drawing technology and equipment level has been greatly developed. Cold rolling mill, cold drawing machine is high-speed, high precision, long stroke, multi-line direction, can achieve large diameter reduction and large reduction in the amount of rolling deformation of about 80% in cold rolling mill to complete. Using cold-rolled fixed wall, supplemented by cold-drawn to change the specifications and control the outer diameter, to meet the requirements of different varieties and specifications. The process characteristics of this mill are:
1) the use of inertial force and inertia torque vertical balance mechanism, rolling mill to improve the number of round trip;
2) the use of ring-type, length than the short stroke mill length of 70%, rolling uniformity of the increase in the amount of delivery increased;
3) the use of long tube billet, increase the length of the pipe, can produce long steel pipe, improve mill productivity, improve the effective utilization of rolling coefficient;