Heat tratment 1

[woody123]

I am trying to heat treat 30mm dia 530M40 to achieve
ISI 898 GRADE 8.8 BOLT SPEC and need advice on heat treatment

 

[dbooker630]

What specific advice are you seeking?

The spec calls out a core hardness of 23-34 HRC, minimum tempering temperature of 425C. Surface hardness shall not exceed core by more than 30 Vickers (2 HRC points).

Equipment should be such that the fasteners can be loaded in a single layer. Quench should be oil. Temper as noted.

 

[TVP]

Austenitize at 820-860 C, oil quench, temper between 540-680 C; Tempering at 540 C will produce higher hardness closer to PC 10.9, so I would start closer to 600-640 C for PC 8.8.