cut edge hardining of A-709

Date 03-19-2008 03:12

I have seen flame cut edges on A36 get hard, how hard is too hard?
If You have to machine it [as We did] it depends on the operation, and what the cutter material is. With carbide face milling taking a cut deep enough to get under the hardened material usually solves the problem.
To start a bandsaw cut You can grind a notch with an angle grinder to get through to the softer metal.
Drilling on a machine tool [large drill press or boaring mill] was seldom a problem, use low speed and lots of pressure.
The oxide on the surface is half the battle, especially with high speed steel cutters, always cut deep enough to get under that.

By 803056

Date 03-19-2008 03:43

Preheat the material ahead of the torch to minimize the cooling rate and the tendency to harden. Use the same preheat as you would for welding.

Best regards - Al

By dmilesdot (**)

Date 03-19-2008 16:32

Is this a problem associated with A709? I have a fabricator that is having a particular problem with hardness in the 45-60 range. (rockwell C) I know that the edges usually harden but I havent seen it to this extent. We require grinding if it exceeds 30.
Dave

By HgTX

Date 03-19-2008 19:03

Are they preheating?

Hg

By DaveBoyer (*****)

Date 03-20-2008 04:54

That is really hard. 45 RC is going to give serious machining ptoblems with high speed steel cutters, much above 50 won't be a treat with carbide, and 60 sounds extremely high.