Thermal forming manufacturing process, including large-diameter seamless hot-rolled and hot extrusion of the two methods, the former is mainly used in the production of composite pipe joints, which applies seamless composite pipe production.

Rolling is a traditional method of preparing large-diameter seamless steel pipes. Hot rolling in substance the welding pressure, if the deformation is large enough, the pressure exerted by the roll of metal would damage the surface of the oxide film, the atomic surface in contact, so that the two surfaces are welded together. Rolling disadvantages are:

Advantages of large-diameter seamless pipe rolling

High productivity, good quality, low cost, and can save a lot of wear and tear of metallic materials, and therefore is an extremely wide application of composite material production technology. Rolling composite sheet combining 90% of the total composite plate, and is often applied to the pipe wall thickness of less than 32mm of the processing.

Disadvantages of large-diameter seamless pipe rolling

One-time investment, but also a lot of material combinations can not be achieved by rolling complex. Is currently the most widely used technology for the use of rolling steel, stainless steel composite pipe joints manufacturing.

Hot extrusion is generally carried out for the bi-metal tube, called a composite extrusion (coextrude). Coextrusion is currently the best method for producing stainless steel and high nickel alloy seamless composite tube, Japan Steel is produced by this method 8in (203.2mm) below the bimetallic composite pipe. It is a large-diameter composite consisting of two or more metal blanks that are heated to about 1200 ℃ and then extruded through an annular space formed by the mold and the mandrel. When the extrusion billet cross-section is reduced to 10:1, high extrusion pressure and temperature at the interface produced a “pressure welding” welding effect, promoting the rapid and widespread diffusion of the interface between the combination to achieve a metallurgical bonding interface. Before the extrusion composite tube manufacturing method, there are three: the forging billet piercing and enlarged by hot extrusion obtained; direct centrifugal spin casting; corrosion-resistant powder particles. There are two metal raw materials are used inside and outside the powder, called “NUVAL” technology, which can develop new alloys, but the cost is too high for preparing powder. Coextrusion disadvantages are:

Advantages of large-diameter seamless pipe hot extrusion

The interface is metallurgically bonded; forces involved in the extrusion process are completely stressed, it is particularly well suited to the hot workability, high alloy processing low plasticity of metals.

Disadvantages of large-diameter seamless pipe hot extrusion

As determined by the extrusion process combined with a very short diffusion interface elements, usually due to the presence of oxide films have been affected, so far limited to the composite extrusion composite carbon steel, stainless steel, and high nickel alloys between. It is noted that a small deformation resistance of the hot extrusion, allowing a large degree of deformation of each, results in higher surface roughness, and therefore also be further cold rolling the hot extrusion (or drawing) of the method of manufacturing a composite pipe.