Flame Cutting P91 2

[kennwayn]

What is the effects to 9 chrome when it has been flame cut with an Oxy-Acetylene torch?

 

[metengr]

kennwayn;
What material, Grade 91 or Grade 9 ??? What is the application, as well?

In general, for air hardening steels, flame cutting should not be permitted for these materials because of the adverse effects on mechanical properties. If you absolutely need to flame cut, you better allow lots of extra stock to remove (by machining or grinding) heat damaged material.

 

[stanweld]

We prohibit flame cutting because of the extremely poor quality of the cut edge, requiring massive ammounts of mechanical rework. Manual plasma cutting may be done on thinner wall thickness but not for thicker walls for the same reason.

At least 3/16" of material should be removed after thermal cutting.

 

[kennwayn]

Thanks guys!
Metenger, It is ASTM-A335 Grade P91.
8" dia Schedule 160
Design Pressure: 2365 PSIG
Design Temp: 1070 ªF

This is a big No-No I know. We are cutting it out.
Its a header they blew a hole in for a Latrolet and the hole is about 2 " dia. They tried taking a shortcut and not following the proper procedure and I caught them.
I was just curious of the adverse effects of the Mechanical Properties now that they have made this mistake and how much of the base metal was affected. They asked me because I am the Heat Treat Supervisor on this job but I deal with Preheats and Post Weld Heat Treatment, I am by no means a Metallurgist LOL!

 

[metengr]

I was just curious of the adverse effects of the Mechanical Properties now that they have made this mistake and how much of the base metal was affected.

Poor or should I say unpredictable creep strength properties. A very wise decision to replace the material.