Forging, heat treatment and surface strengthening technology of die casting die

1. Forging

The optimized forging process, namely three-way forging, is adopted for the die blank, which is formed after repeated forging and mouth length. The microstructure of the die blank is strictly controlled. Carbide segregation and banded structure elements shall be ≤ 2.

2. Quenching and tempering treatment

Because the mold cavity is complex and the thickness is very different, in order to reduce the distortion of the final quenching of the mold and facilitate the cutting, the rough machined mold blank is quenched and tempered, and the hardening and tempering hardness is controlled at 250-280.

3. Micro deformation quenching and tempering of dies

After several times of preheating and tempering processes, the die casting die has a hardness of HRC44-48. Through testing, the distortion variables are: flatness ≤ 0.015mm, cavity shrinkage 0.015-0.035mm, all in line with the dimensional accuracy requirements of the drawing.

4. S-N-C penetration of modules

In order to improve the wear resistance, anti seizure, anti adhesion and fatigue performance of the die casting die, and prevent thermal fatigue cracks from appearing prematurely, after fine polishing, the non-toxic S-N-C co parametric process was used to replace the traditional toxic salt bath nitriding, and the surface of the die casting die was strengthened.

S-N-C process: the salt bath of process infiltration contains 35% - 7% CNO-S -=(2~10) x10 ˉ 6； The penetration temperature is (565 ± 5) ℃, the time is 3.5-4.0h, and the air cooling is applied.

After S-N-C penetration, the surface of the mold shows an extremely beautiful black bright color, the penetration layer and the matrix are well bonded, and the surface hardness is up to 1046HV5.

In addition, in order to eliminate the stress generated during cooling after the die penetration, the die casting die shall be tempered before being put into use. Tempering process: (220-2540) ℃ x5h, air cooling.

In order to better improve the service life of the die casting die, the die shall be stress relieved once in the argon ion nitriding furnace after every 10000 die uses. The process is: slowly raise the temperature of the mold to 530-550 ℃, keep it warm for 5-6h, and then cool the mold to 180-200 ℃ by air cooling.