Thermoforming seamless steel pipe manufacturing process
Thermoforming processes include hot-rolled seamless steel pipe and hot extrusion two methods, hot rolling process is mainly used for the production of composite pipe joints, hot extrusion process is suitable for manufacturing seamless composite pipe production.
Rolling is a traditional method of preparing large-diameter seamless steel pipe. Hot Rolling essentially within the pressure welding, if the deformation is large enough, the pressure exerted by the rolls would destroy the metal oxide film on the surface of the surface atoms to achieve contact with the surface so that the two are welded together. Advantages and disadvantages of rolling are:
Advantages: high productivity, good quality, low cost, and can save a lot of wear and tear of metallic materials, and therefore is extremely wide application of composite materials production technology. Rolling bonded composite panels composite panels accounted for 90 percent of total production, and often used in pipe wall thickness of less than 32mm of processing.
Disadvantages: one-time investment, and many combinations of materials can not be realized by rolling complex. Currently the most widely used is the use of technology for rolling carbon steel pipe, stainless steel pipe manufacturing composite pipe joints.
Hot extrusion is typically performed for bi-metal tube, called coextrusion (coextrude). Coextrusion is currently the best method for the production of stainless steel pipe and high nickel alloy seamless composite pipe, Japan Steel Works produced using this method 8in (203.2mm) below the double-metal composite pipes. It is a large-diameter composite consisting of two or more metal billets heated to about 1200 ℃, then squeezed through the annular space formed by the mold and the mandrel. When extrusion billet cross section reduced to 10: 1, the high extrusion pressures and temperatures generated at the interface of "pressure welding" welding effect, promote the rapid and widespread diffusion bonding interface between the interface to achieve metallurgical bonding. Method of manufacturing a composite tube before extrusion in three ways: by the forging billet by hot pressing to obtain perforation and amplification; Direct centrifugal spin casting; corrosion with powder particles. There are both internal and external metal materials by powder, known as "NUVAL" technology enables the development of new alloys, but the preparation of the powder is too costly. Coextrusion disadvantages are:
Advantages: metallurgical bonding interface; extrusion force involved in the process completely stress is therefore particularly suitable for hot workability is not good, low plasticity processing high-alloy metals.
Disadvantages: Due to the combination depends on the extrusion process in a very short time the elements of interface diffusion, usually due to the presence of the oxide film is affected, there is currently limited to the coextrusion carbon steel pipe, stainless steel pipe and between high nickel alloys composite. It should be noted that a small deformation resistance of the hot extrusion, each time allowing large degree of deformation, resulting in higher surface roughness, and therefore also to hot extrusion and then subjected to cold rolling (or cold drawn) a method of manufacturing composite pipe.
