ASTM A995 Gr 6A heat treatment

[elmio]

Dear All

We have a new designed 16" valve made in Gr 6A. During the heat treatment it was crecked. Do anyone have a typical chart for Superduplex heat treatment?
I assume we have to hold around 300-400 deg C for first step and haet up to 1100-1200 and holding there for sufficient time than water quechend.
Our chart is goes up 1150 deg C straitaway raffle 80 deg C / hours.
Thank you

Regards

Elmio

 

[metengr]

The heat treatment minimum requirements are specified in ASTM A 995 for Grade 6A, please review Table 1 heat treatment requirements. As far as a specific process procedure, for ramp up rates, hold time, etc., this is developed by the vendor and is based on experience.

 

[elmio]

Thank you metengr!

I have checked it, looks like the foundry was following it. Do you have any idea why is creacked? Ramp rates my be too quick?

Thanks

 

[mrfailure]

Thermally-induced cracking from excessive ramp rates could be included as a possible mechanism. You should perform a metallurgical analysis of the cracked valve to really find out as other possible causes could be just a likely with such a cracked casting.

 

[elmio]

Thank you very much.

Have a lovley day.