Cr-Mo-V low alloy steel

[GraySyracuse]

Hi Folks,
I need a little help/recommandation for welding Cr-Mo-V low alloy steel investment casting. Is anybody having some information to share about: what welding rod better to use, pre-heat temps and after weld cooling speeds, post-weld ht, etc.
Thank you
CC

 

[GRoberts]

Gray,

All the info you are asking for depends on the composition of your Cr-Mo-V material. What is the composition, or specification? There are several types of Cr-Mo-V material.

 

[GraySyracuse]

THX for the fast response. The chems is close with ASTM A356 grade 9 C=0.2% max, Mn=0.5-0.9%, Si=0.2-0.6%, Mo=0.9-1.2%, Cr=1.0-1.5%, V=0.2-0.35%, Fe=bal.

 

[GRoberts]

Depending on the customers requirements, for A356 grade 9 we use electrodes such as 9018-B3, 8016-B5, or some proprietary ones like Oerlikon OE-N125, Thyssen "SH Kupfer 3KC", or Devasco CR-Mo-1/4V. I am just listing the SMAW variety electrodes, of course similar ones are available for FCAW, GMAW, or GTAW. Most of our procedures us a 400F preheat and 600F max interpass. You might be able to get away with a lower preheat if you are welding thinner materails, ours are usually pretty thick. We typically either stress relive at 1275F, or normalize(1900F) and temper (1300F)

 

[GRoberts]

Forgot to mention, also look at the ASTM specification. It gives requirements for preheat, and PWHT that if not required by the specification you are working to, can also serve as a good guideline.

 

[GraySyracuse]

Thank you very much for your support.
Based on you experience, do I need to pre-heat the parts before welding (and what it is the recommended temp) and how about cooling after welding (slow cool I assume, but how slow?)