Holding time normalising of P/T 22 after welding

[JB2001]

We have been asked to perform mechanical tests of welded joints in P/T22 (2.25Cr 1Mo) which shall be normalised and tempered after welding. The normalising treatment shall be done at 920-940 degree Centigrade according to requirement from our client, but how long holding time shall I choose for weld samples of 20 and 25 mm thickness respectively? I do not want to risk any grain growth.

 

[123rajkumar]

30mts - 35mts at the temp. is good enough for 20 and 25mm thk. weld material.

 

[andyenergy]

Let us know what the results from the testing were. I was always under the impression that normalising of 2.25Cr1Mo was bad idea - the as deposited structure is bainitic and a stress relief would produce an ideal reduced stress state. Normalising would (I think) produce a mixed microstructure with less strength.

Anyone else out there with experience of normlaising and tempering 2.25Cr1Mo welds?

 

[GRoberts]

I have only done welding qualification with N&T PWHT for 1 1/4Cr-1/2Mo, and 1/2Mo. Tensile strength is hard to meet because the carbon in the weld metal is so low. If you had a welding consumable that was designed for N&T (i.e. matched the base metal chemistry) I don't think it would be a problem to meet the mechanical properties.

 

[metengr]

Our hot reheat seam welded piping that was supplied under an SA 155 material specification 40 years ago contained normalized and tempered seam welds. The main benefit derived from normalizing and tempering was to eliminate the heat affected zone. From a creep viewpoint, this is desirable. Having sub-critical PWHT welds can result in Type IV cracking along the fine grained HAZ in repair welds or in orginal fabrication welds.

 

[JB2001]

Thanks everyone for your answers!