High Temperature Iron/Steel

[ChrisTech]

I'm looking for a high tensile strength and hardness material that is difficult to cut with an acetylene torch. Grade 5 ADI is perfect except that it cuts very easy with a torch. Gray Ni-Hard was hard to cut with a torch but it is brittle.

I would like a tensile >100 ksi and hardness >400 Brinell.

Please throw out some ideas? This is for a security item.

 

[Metalguy]

Try cold-worked 301 or 302 SS. Keep in mind that anything short of a $$$$$ superalloy is going to soften quite a bit under the heat of a torch.

 

[GRoberts]

how about a precipitation hardening stainless steel like 17-4 PH?

 

[arunmrao]

The austenitic grades of stainless steel with varying contents of Ni can satisfy the first condition of not being able to be cut by oxyacetylene torch. But the 2nd condition hardness >400BHN is difficult to be met excepting precipitation hardened stainless steel. Alternately you can heat treat 410 or CA40 grades to a higher hardness and use. But these will soften again on being heated. It would have been helpful if you could have elaborated a bit more on the end use application.
Nihard cast iron is always white and never gray.