How much do you know about the basic knowledge of metal surface heat treatment process?

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Surface heat treatment is a metal heat treatment process that only heats the surface of the workpiece to change its mechanical properties.

  Surface heat treatment is a metal heat treatment process that only heats the surface of the workpiece to change its mechanical properties. In order to heat only the surface of the workpiece without transferring too much heat into the workpiece, the heat source used must have a high energy density, that is, give the workpiece a large amount of heat energy per unit area, so that the surface or part of the workpiece can be heated in a short time. internal or instantaneous high temperature.
  The main methods of surface heat treatment are flame quenching and induction heating heat treatment. Commonly used heat sources are flames such as oxyacetylene or oxypropane, induced current, lasers, and electron beams. Chemical heat treatment is a metal heat treatment process that changes the chemical composition, microstructure and properties of the workpiece surface. The difference between chemical heat treatment and surface heat treatment is that the latter changes the chemical composition of the workpiece surface.
  Chemical heat treatment is to heat the workpiece in a medium (gas, liquid or solid) containing carbon, nitrogen or other alloying elements, and maintain the temperature for a long time, so that the surface of the workpiece is infiltrated with carbon, nitrogen, boron, chromium and other elements. After the elements are infiltrated, other heat treatment processes such as quenching and tempering are sometimes required. The main methods of chemical heat treatment are carburizing, nitriding and metallizing.
  It is one of the important processes in the process of heat treating mechanical parts and tool manufacturing. Generally speaking, it can guarantee and improve various properties of the workpiece, such as wear resistance and corrosion resistance. It can also improve the structure and stress state of the blank to facilitate various cold and hot processing. For example, white cast iron can be annealed for a long time to obtain malleable cast iron and improve plasticity; with the correct heat treatment process, the service life of the gear can be doubled or even dozens of times that of the gear without heat treatment. In addition, cheap carbon steel has some expensive alloy steel properties by infiltrating some alloying elements, and can replace some heat-resistant steel and stainless steel; almost all molds require heat treatment before they can be used.
  Steel is classified as an alloy consisting primarily of iron and carbon, with a carbon content generally less than 2.11%. Steel is an extremely important metal material in economic construction. According to the chemical composition, steel can be divided into carbon steel (referred to as carbon steel) and alloy steel. Carbon steel is an alloy obtained by smelting pig iron. In addition to iron and carbon, its main components also contain a small amount of manganese, silicon, sulfur, phosphorus and other impurities. Carbon steel has certain mechanical properties, good process performance and low price. Therefore, carbon steel has been widely used. However, with the rapid development of modern industry and science and technology, the performance of carbon steel can no longer fully meet the needs, so people have developed various alloy steels. Alloy steel is a multi-element alloy obtained by purposely adding certain elements (called alloying elements) on the basis of carbon steel.