impact test low temperature- alloy steel

[alanisphoenix]

Hello,
i´m reading some specification for P22 and P11 (ASTM A335) where the client is asking for impact test at -29ºC (for P22)and -36ºC (for P11).

We have carried out some test and it seems to me that these grades are in their limit of the trasnsition curve. I have obtain values less than 27julious.

Pipes are Normalized and Tempered. Doing odble time at the tempering we have obtain better values (higher than 100j) at -20, but at those Tª the julios decrease so much.

Any suggestion to obteain better values? Could i modify maybe something ta the chemical composiction.. range of temperature for the heat treatment.. or do you think the steel is in its limit?

thank you

 

[weldstan]

Do you have chemistry controls on P, S, As, and Sn? You can try double normalizing and tempering as well.

 

[EdStainless]

Check you normalize temps and make sure that you are not too hot (or cold).
There are tools to help you calculate transition temperatures based on actual chemistries.
For most applications it isn't a big deal, but trying to push DBTT you will need everything that you can get.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed