PWHTing alloy 4130 to P-1 materials

[copperly]

In accordance with ASME B31.3, is a PWHT temperature of 1150 +/- 50, acceptable. you wouldn't want to take the CS to 1300-1375, would you ?

 

[metengr]

copperly;
No. For P-No 1 base material (CS), the minimum PWHT temperature is 1100 deg F. You do not want to exceed the lower transformation temperature for P-No 1 material which is 1300 deg F or higher.

 

[copperly]

metengr, thanks for your reply ! What verbage in B31.3 exempts me from this. I've scrubbed the 331.1.1 table and the associated notes, I seem to have overlooked something ? Thanks for your time !

 

[metengr]

copperly;
If you have B31.1 look at 129.3.2 for published lower critical transformation temepratures. For B31.3 look at table 331.1.1 for heat treatment, which would apply for forming and post weld heat treatment. This is all you need to help you.

 

[copperly]

I am welding 4130 to A106B, over 1/2 " in thickness. 4130 would be considered P-4 as it is > .5% < 2% Cr. Table 331.1.1 calls for a PWHT @1300-1375. I was thinking that I would see some exception to the 1300 due to the carbon steel transformation temperature, but I don't. I know that I don't want to exceed the transformation temperature, but am having a hard time locating print that allows me to deviate from that table.

 

[metengr]

For dissimilar weld joints of the example for carbon steel (CS) and low alloy, the lower alloy grade CS would govern PWHT temperature requirements. It is common practice to avoid subjecting the CS to exceeding the lower critical transformation temperature, As I stated before.

 

[metengr]

For proof, look at 331.2.3 in B31.3. Your answer is there as I stated above.