Strengthening type of steel heat treatment process

The heat treatment process direction is mainly studied, and the following are several strengthening types:

(1) Solid solution strengthening

This kind of solid solution strengthening by adding other elements to the base metal is called solid solution strengthening. The effect can be achieved by adding some alloy elements to the bulk metal. When the atoms of solute melt into the matrix, the lattice will be distorted, and the hardness and strength will increase after increasing the dislocation resistance.

Solid solution strengthening is generally divided into two ways: 1) interstitial solid solution strengthening. Strengthening elements C, N and B can exist in the solid solution gap. 2) For displacement solid solution strengthening, some displacement solid solution elements such as Mn and Si are added to the bulk metal. The solid solution strengthening effect of gap is usually better than that of displacement. During solid solution strengthening, the appropriate solute atom concentration will improve the hardness and strength of the material, and reduce the plastic toughness.

(2) Deformation strengthening

After the metal material is subjected to an external force greater than the yield strength, if the external force is increased, the plastic deformation continues to occur. In the plastic deformation, there are dislocations in the material, and the continuous topographic deformation hinders the movement of dislocations, so that the material is strengthened, the strength is improved, and the plasticity and toughness will become weak.

(3) Precipitation strengthening and dispersion strengthening

By adding alloy elements to the steel, the alloy elements and matrix elements are alloy strengthened, and the second phase hinders the dislocation movement in the matrix. Dispersion strengthening is the strengthening caused by mechanical mixing of hard particles in the matrix. There is chemical interaction between precipitation strengthening elements, but there is no chemical interaction between dispersion strengthening elements. When the compound in the matrix is uniformly dispersed, the plastic toughness can be reduced little on the basis of improving the strength and hardness. The more uniform the dispersion plasmid is, the better the strengthening effect is.

(4) Phase transformation strengthening

In general, there are pearlite structure transformation, martensite structure transformation and bainite structure transformation. Due to different heat treatment processes and different material components, different material structure types can be obtained. Different material structure types make their mechanical properties very different. As shown in the figure, when austenite is transformed into various microstructure by cooling, the martensite structure under re quenching process has good strength because of the high dislocation density in the structure.