Do you know what processes are available for metal heat treatment? Today Bolt Factory-Zhejiang Weigao will explain the three major processes of metal heat treatment.
Metal heat treatment processes can be roughly divided into three categories: overall heat treatment, surface heat treatment and chemical heat treatment. According to the different heating medium, heating temperature and cooling method, each category can be divided into several different heat treatment processes. The same metal uses different heat treatment processes to obtain different structures and thus have different properties. Steel is the most widely used metal in industry, and the microstructure of steel is also the most complicated, so there are many types of steel heat treatment processes.

Overall heat treatment
It is a metal heat treatment process that heats the workpiece as a whole and then cools it at an appropriate speed to change its overall mechanical properties. The overall heat treatment of steel has four basic processes: annealing, normalizing, quenching and tempering. Annealing, normalizing, quenching, and tempering are the "four fires" in the overall heat treatment. Quenching and tempering are closely related, and they are often used in conjunction with one another.
Annealing is to heat the workpiece to an appropriate temperature, use different holding times according to the material and workpiece size, and then slowly cool it, the purpose is to make the internal structure of the metal reach or close to the equilibrium state, obtain good process performance and use performance, or for further quenching Prepare for organization.
Normalizing is to heat the workpiece to a suitable temperature and then cool it in the air. The effect of normalizing is similar to annealing, except that the resulting structure is finer. It is often used to improve the cutting performance of low-carbon materials, and sometimes it is used for some low-carbon materials As the final heat treatment.
Quenching is the rapid cooling of the workpiece in quenching medium such as water, oil or other inorganic salts, organic aqueous solutions after heating and holding the workpiece. After quenching, the steel becomes hard, but at the same time it becomes brittle.
Tempering: In order to reduce the brittleness of steel parts, the quenched steel parts are kept for a long time at an appropriate temperature higher than room temperature but lower than 650℃, and then cooled.
The "Four Fires" have evolved different heat treatment processes with different heating temperatures and cooling methods. In order to obtain a certain strength and toughness, the process of combining quenching and high temperature tempering is called quenching and tempering. After some alloys are quenched to form a supersaturated solid solution, they are kept at room temperature or a slightly higher temperature for a longer period of time to improve the hardness, strength, or electrical magnetic properties of the alloy. Such a heat treatment process is called aging treatment.
The method of effectively and closely combining pressure processing deformation and heat treatment to obtain a good strength and toughness of the workpiece is called thermomechanical treatment; heat treatment performed in a negative pressure atmosphere or in a vacuum is called vacuum heat treatment, which can not only make The workpiece is not oxidized or decarburized. It keeps the surface of the workpiece smooth and clean after treatment, improves the performance of the workpiece, and can also pass through the infiltration agent for chemical heat treatment.
Surface heat treatment
A metal heat treatment process that only heats the surface of the workpiece to change the mechanical properties of the surface. In order to heat only the surface of the workpiece without causing excessive heat to be transferred into the interior of the workpiece, the heat source used must have a high energy density, that is, to give a larger heat energy to the workpiece per unit area, so that the surface or part of the workpiece can be short-term or instantaneous Reach high temperatures. The main methods of surface heat treatment include flame quenching and induction heating heat treatment. Commonly used heat sources include flames such as oxygen acetylene or oxypropane, induction current, laser, and electron beam.
Chemical heat treatment
Metal heat treatment process by changing the chemical composition, organization and performance of the workpiece surface. The difference between chemical heat treatment and surface heat treatment is that the latter changes the chemical composition of the surface of the workpiece. Chemical heat treatment is to heat the workpiece in a medium (gas, liquid, solid) containing carbon, nitrogen or other alloying elements for a long time, so that the surface of the workpiece is infiltrated with elements such as carbon, nitrogen, boron and chromium. After infiltration of elements, other heat treatment processes such as quenching and tempering are sometimes required. The main methods of chemical heat treatment are carburizing, nitriding and metalizing.
Conclusion
Heat treatment is one of the important processes in the manufacturing process of China Nut and molds. It can control various properties of the workpiece, such as wear resistance, corrosion resistance, and magnetic properties. 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 obtain malleable cast iron after long time annealing treatment, which can improve plasticity; gears adopt correct heat treatment process, and the service life can be doubled or dozens of times longer than gears without heat treatment; in addition, cheap carbon steel can be penetrated Certain alloying elements have certain properties of expensive alloy steels, which can replace certain heat-resistant steels and stainless steels; almost all tools and molds require heat treatment before they can be used.