alloy 20 (ASTM B 729)

By rmejiass Date 10-08-2015 04:11

Hi, I'm qualifying a WPS by ASME IX
Material: p45-p45 (ASTM B 729)
Thickness: SCH 80
Diameter: 6 "
position 6G
Filler metal: ER320LR
wITHOUT BACKing
GTAW welding process
Gas: Argon 100%
No PWHT
Mechanical tests are being rejected breaking over the 76 ksi on weldment. The specific base material 80 ksi tensile strength.
Rx was applied which evidence no health or lack of fusion welding.
1. Why do you think you could be happening?
2. It is recommended for this alloy some PWHT?
3. Do they have any recommendations for avoiding this is rejected for this reason?
Thank you
Reynaldo Mejias

By 803056

Date 10-10-2015 03:28 Edited 10-10-2015 03:47

P45 include nickel based alloys, ER320 is an austenitic stainless if I remember correctly.
ER320 filler metal: 20% Cr, 36% Fe, 34% Ni
ASTM B729: 32-38% Ni, 19-21% Cr, balance Fe and at touch of this and a dash of that.
Looks like a good metallurgical match.

I found this site on-line. Here's the link: http://content.rolledalloys.com/technical-resources/fabrication-information/ALLOY-20_FI_US_EN.pdf

It may be a matter of technique.

Al