Specific steps are as follows: 1) the steel material to be included in the resistance furnace, 850-870 ℃, 60-90 - s/per mm steel;

2) 1090-1110 ℃, 70-90 - s/per mm steel, oil cooling or air cooling to room temperature

3) then steel material again in the resistance furnace, 700-720 ℃, 90 min, air cooling to room temperature.

4) steel material to be included in the salt bath furnace, heating up to 940-960 ℃, 60-90 - s/per mm steel;

5) remove steel material quickly into the temperature is 730-750 ℃ in the salt bath furnace, 60-90 - s/per mm steel, and steel is expected to take out rushed into the 940-960 ℃ in the salt bath furnace, 60-90 - s/per mm steel;

6) repeat step 5) after 3-5 times, air cooling to room temperature;

7) steel material to be included in the tempering furnace, 600 ℃ heat 90 min, air cooling to room temperature.

8) steel is expected to once again to be included in the tempering furnace, 580 ℃, 90 min, air cooling to room temperature or get the finished product, the advantage is obvious grain size, uniform microstructure, large size carbide decreases, banded structure.

The heating medium of salt bath furnace is 100%NaCl.

4 cr5mosiv1 steel has excellent hardenability, hardenability and good at room and high temperature performance, are widely used in thermal fatigue tensile strength, good toughness and high temperature < 700 ℃ under the working conditions of the mold.

At present, the traditional 4 cr5mosiv1 steel heat treatment process for: along with the furnace heating up to 850-870 ℃ annealing, heat preservation for a period of time after the oven to 500 ℃, cold air cooling;

Again heated to 550-600 ℃ heat preservation for a period of time, continue to heated to 800-850 ℃ heat preservation for a period of time, continue to heated to 1030-1050 ℃ heat preservation for a period of time, oil or air cooling, cold 600 ℃ tempering process, and then 580 ℃ tempering treatment, if there are special needs for the third time even tempering treatment, 4 cr5mosiv1 treated by the heat treatment process, its basic performance meets the demand of the use of common mould, but for large, sophisticated, complex, long steel are serving under the condition of high temperature, the heat treatment process already cannot satisfy the use requirement, the carbide and severe banded structure segregation, reduce the 4 cr5mosiv1 steel are strong toughness.

(1) in the traditional 1090-1110 ℃ high temperature processing after the annealing process, then 700-720 ℃ heat preservation processing, makes the homogenization, carbide dissolution of alloy element in steel and carbide dispersion precipitates in the matrix, reduce the occurrence of large size carbides, the ease of banded structure;

(2) near phase transition point take salt bath furnace heat preservation processing cycles, the previous processing grain in nucleation site in the process of nucleation, has been further refine grain of nucleation, uniform microstructure;

(3) in the case of equivalent strength, the plasticity is greatly improved, and all kinds of performance indicators (such as, as well as the parameters such as the case, the function, the delta, the K, KIC, etc.) have been improved to varying degrees.

The mechanical properties of traditional heat treatment and toughening process.