Nitriding process of HPM75 non-magnetic steel die (surface nitriding process)
(1) Test material: HPM75 non-magnetic steel chemical composition is as follows:
C      Si    Mn  PS    Cr  Mo   V    W
0.69 0.65 15.3 0.02 0.01 2.31 0.75 1.83 0.62
Note: The state of the material is solution + aging, and the hardness is 47HRC.
(2) Test method: 8mm*15mm*30mm samples were used in the test, respectively, in the LD50 ion nitriding furnace and RN35 gas nitriding furnace. The depth of the impregnation layer is measured by a hardness test.
Results and analysis: the surface hardness of ion nitriding and gas nitriding were 1130hv0.3 and 1180hv0.3 respectively, and the layer thickness was 0.21mm and 0.15mm respectively. The hardness of substrate of the two nitriding processes is 490Hv0.3.
The die life of the two nitriding processes is 3.2 times and 2.3 times of that of solution + aging state respectively. HPM75 non-magnetic steel contains more alloying elements, which combine with nitrogen to make the surface of the die have higher hardness and wear resistance, and greatly improve the service life of the die.
5 conclusion
(1) Proper use of HPM75 non-magnetic steel heat treatment process and mold processing process is conducive to mold processing and normal use.
(2) Gas nitrocarburizing significantly improves the surface hardness, wear resistance and service life of HPM75 non-magnetic steel die. The surface of the blank pressed with it is bright and easy to demoulding, which improves the quality and production efficiency of the blank.
(3) Nitriding does not change the non-magnetic properties of HPM75 steel.