Heat treatment classification of surface

Surface heat treatment technology can be roughly divided into three categories: overall surface heat treatment, exterior surface heat treatment and chemical surface heat treatment. The same kind of metal chooses the different surface heat treatment technology, may obtain the different arrangement, then has the different function. Let's make a specific analysis on specific problems to see what are the three methods of surface heat treatment:

I. overall surface heat treatment

1, annealing is the workpiece heated to proper temperature, according to the information and artifacts scale and the use of different heat preservation time, and then slowly cooling, intention is to make the metal internal arrangements reached or approached balance, outstanding technical function and use function, may arrange preparation for further hardening.

2, normalizing is to heat the workpiece to the appropriate temperature after cooling in the air, the role of normalizing is similar to annealing, only to get a finer arrangement, often used to improve the cutting function of the data, but also sometimes used for some parts with low demand as the end of the surface heat treatment.

3, quenching is to heat the workpiece after heat preservation, in water, oil or other inorganic salts, organic water solution and other quenched cooling medium. After quenching the steel pieces harden but become brittle together.

4. In order to reduce the brittleness of steel parts, the steel parts after quenching are kept warm for a long time at an appropriate temperature higher than room temperature and lower than 650℃, and then cooled. This technique is called tempering

Surface heat treatment is a metal surface heat treatment technique that only heats the surface of the workpiece to change the mechanical function of the surface. In order to only heat the surface of the workpiece without too much heat into the workpiece, the heat source used must have a high energy density, that is, in the unit area of the workpiece to give greater heat, so that the surface or part of the workpiece can be short or instantaneous high temperature. The primary method of exterior surface heat treatment is flame quenching and induction heating surface heat treatment, commonly used heat source such as aerobic acetylene or oxypropane flame, induction current, laser and electron beam.

5. Chemical surface heat treatment

Chemical surface heat treatment is a metal surface heat treatment technology by changing the surface chemical composition, arrangement and function of the workpiece. The difference between chemical surface heat treatment and surface heat treatment is that the latter changes the surface chemical composition of the workpiece. Chemical surface heat treatment is to heat the workpiece in the medium containing carbon, nitrogen or other alloy elements (gas, liquid, solid), insulation for a long time, and then the surface of the workpiece into the carbon, nitrogen, boron and chromium elements. After entering the element, other surface heat treatment techniques such as quenching and tempering are sometimes used. The primary method of chemical surface heat treatment is carburizing, nitriding, metal.

The development of science and technology forces the rapid development of all walks of life, the application of surface heat treatment in the iron and steel industry is more and more, different surface heat treatment methods, the production of the workpiece is also different, only to understand what kind of treatment, can be more conducive to their own work.