Hardness of 2.25Cr-1Mo Autogenous welds

By BGM dharan Date 08-15-2003 08:35

What is the hardness of autogenous 2.25Cr-1Mo welds (with 0.1 wt %C) after a PWHT at 690 degree centigrade for 1 hr? The thickness of the referred welds is 5 mm. The weld has also very low sulphur (0.002 wt%).

The required hardness in the welds after appropriate PWHT is maximum of 240 HV (30Kg) in the welds. Is PWHT at 690 degree centigrade for 1 hr sufficient?

Request your answer if you have one.

By G.S.Crisi (****)

Date 08-15-2003 22:30

First of all, let me ask you a question: according to which Code (or Standard) are you making that weld?
One hour soak seems to be too long a time for 5 mm thickness. I'm accostumed to shorter times for 5 mm thicknesses.
This means that the conditions you mention SHOULD be OK. I've deliberately underlined SHOULD because, as a matter of fact, unless someone has the crystal ball, nobody knows what exactly the hardness will be after the PWHT. It depends, among other parameters, on what was the hardness BEFORE the treatment.
You shouldn't bother, though. When the first PWHT doesn't result in the required hardness, as sometimes happens to everybody, it is repeated again.
Giovanni S. Crisi
Sao Paulo - Brazil