Re: [MW:29813] HIGH HARDNESS AFTER PWHT

Surface preparation or missing effectiness on PWHT.

On Jul 10, 2019 3:11 PM, "Karthikeyan Muthuvel" <m.karthick2020@gmail.com> wrote:

Dear Experts,

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

1. Base material : 130 to 150 HB
2. Heat Affected Zone : 140 to 160 HB
3. Weld Metal : 170 to 190 HB

HARDNESS VALUES AFTER PWHT 

1. Base material : 120 to 140 HB
2. Heat Affected Zone : 130 to 150 HB
3. 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:

1. We had performed nearly 30Nos. of Production joints & we had face the problem of Hardness on all the weld joints. 
2. Hardness was tested using Mic 10 tester method ( even cross verified with Equotip method & Tele brinell Method)

Thank you for your support.

Warm Regards,

KARTHIKEYAN  M.

QA/QC Inspector

Saudiarabia

Mobile:+966-501176985,

E-mail: m.karthick2020@gmail.com

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