[JohnD]

Originally Posted by phoenix

A lot of welders don't stress relive 4130 as they should:

http://weldingweb.com/attachment.php...1&d=1332256871

A process not required with UK spec CDS, as welding CDS does not cause brittleness

Thnaks for posting that link, phoenix!
But I was puzzled; it's called 'stress-relief' and that explanation relies on brittleness due to air and material quenching. So I looked for more information and found this:

http://www.thefabricator.com/article...ess-in-welding

Still says the same thing, pre- and post-weld heating, but in terms of weld distortion due to the weld metal expanding and contracting with temperature; much more likely, IMHO. It also appears to me authoritative and includes much more detail on techniques and methods, some beyond the amatuer, but anyway.
You have stimulated me to learn - thank you!
John