7Mn15Cr2Al13V2WMo Magnetic die steel 7Mn15 magnetic die steel is a kind of high strength austenitic type magnetic die steel, in various states can maintain stable austenite, and has very low permeability, high temperature strength and hardness, and high wear resistance, but the steel machinability is poor, need to undergo high temperature annealing, change the carbon Particle size and distribution of compounds. Using gas nitrogen carburizing heat treatment, can further improve the surface hardness, wear resistance, so as to improve the service life of the die.
C | Si | Cr | Mo | Al | P | S | V | W | Mn | ||
0.65~0.75 | ≤0.80 | 2.0~2.5 | 0.5~0.8 | 2.3~3.3 | ≤0.03 | ≤0.03 | 1.5~2.0 | 0.5~0.8 | 14.5~16.5 |
Heat treatment specification and organization
Heat treatment specification: aging specification
Specification for hot working
Ingot: heating temperature 1150~1170°C, heating time ≥8h, starting temperature 1100~1120°C, end temperature ≥950°C, air cooling.
Billet: Heating temperature 1140~1160°C, heating time ≥8h, starting temperature 1080~1100°C, end temperature ≥950°C, air cooling.
The hardness after hot working is 33 ~35HRC.
(5) High temperature annealing specification
Annealing temperature 870 ~890°C, holding 3-6h, furnace cooling to 500°C below the air cooling.
Annealed hardness is 28 ~ 30HRC, microstructure is fine grain austenite + uniform distribution of granular carbide. The machinability of the steel can be improved by high temperature annealing.
(6) Specification for solution treatment
Solution temperature 1150~1180°C, salt bath furnace insulation 15~20min/mm, box furnace insulation 30min/mm, water
Cold, solution hardness 20 ~22HRC. Metallography: austenite + undissolved primary carbide.
(7) Specification of aging treatment
Aging temperature 650 ~700°C, aging 15 ~ 20h, air cooling, hardness; 45HRC
(8) Gas nitrogen carburizing specification
The co-permeation temperature is 560 ~570°C, the co-permeation time is 4 ~6h, the surface hardness is 950~1100HV, the nitriding layer depth is 0. 03~0.04mm.
