Good day.
We had used the consumables (ER70S-2) / OK TIG ROD 12.62, Size : 2.4mm Dia. for our Production weld joints (Pipe materials : Carbon Steel ASTM A 106 Gr. B; Size : 3" X Sch 40). further to inform you that we had checked the Hardness of Base material , HAZ & on weld Metal before & after PWHT (below hardness readings were observed).
HARDNESS VALUES BEFORE PWHT
- Base material : 130 to 150 HB
- Heat Affected Zone : 140 to 160 HB
- Weld Metal : 170 to 190 HB
- Base material : 120 to 140 HB
- Heat Affected Zone : 130 to 150 HB
- Weld Metal : 210 to 250 HB
After performing PWHT the hardness value of Base material & Heat Affected Zone has been reduced. whereas the Hardness value of Weld Deposition has been increased (which is beyond the acceptable limit).
So, I would like to know from you that what might be the technical reason/root cause for increase in hardness only on the weld joint after PWHT.
Below are the PWHT parameters fyi.
Soaking Temp. : 620 Deg C
Soaking Time : 1 hr.
Rate of Heating : 100 Deg C per Hour (from 100 Deg C)
Rate of Cooling : 100 Deg C per Hour (Upto 100 Deg C)
Note:
- We had performed nearly 30Nos. of Production joints & we had face the problem of Hardness on all the weld joints.
- Hardness was tested using Mic 10 tester method ( even cross verified with Equotip method & Tele brinell Method)
Thank you for your support.
KARTHIKEYAN M.
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
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