Heat Treatment Process

Heat treatment is one of the most important process of mechanical parts and tooling manufacturing process. Broadly speaking, it can ensure and improve various properties of the workpiece, such as wear and corrosion resistance. It can also improve the organization and the stress state of the blank, in order to facilitate a variety of cold and hot processing. Such as malleable iron can be obtained after the annealing process of white cast iron for a long time, from which the plasticity gets improved; with the correct , the service life of gear can be several times or for dozens of times increased compared to the no heat treatment gear; in addition, inexpensive carbon steel by infiltration some certain alloy elements can achieve alloy steel properties of expensive price, which can take place of some heat resistant steel and stainless steel; tool mold almost all need the heat treatment before put into use. Chemical heat treatment is a kind of metal achieved by changing the workpiece surface chemical composition, microstructure and properties. The differences between the chemical treatment and surface heat treatment is that the latter has changed the chemical composition of the workpiece surface. Chemical treatment is heating the workpiece on the media containing carbon, nitrogen, or other alloying elements (gas, liquid, solid), insulation for a long time, which helps to the infiltration of carbon, nitrogen, boron and chromium and other elements for the workpiece surface. After incorporating the elements, sometimes some other thermal processes, such as quenching and tempering, are also needed. The main method of chemical heat treatment are carburizing, nitriding, surface alloying. Surface heat treatment is a kind of metal only heating the workpiece surface to change its surface mechanical properties. In order to heat only the surface of the workpiece without causing excessive heat getting into the interior of the workpiece, the heat source used must have a high energy density, namely giving a considerate large thermal energy for per unit area of the workpiece, to promote the surface or local parts of the workpiece to reach high temperatures in short time or instantaneously. The main method of the surface heat treatment contains the quenching and the induction heating treatment, the heat source used is oxyacetylene flame or oxygen propane, induced current, laser and electron beam. Besides above mentioned , there is also an essential one-overall heat treatment. Which is widely used in the manufacture of seamless steel pipe,,HFW steel pipe,etc.