Re: [MW:29821] HIGH HARDNESS AFTER PWHT (ER70S-2)

Please remember that without PWHT, you do not see any changes in the hardness. 

When you see an increase after heat treatment, most of the time these elements are responsible.

Ramin  Kondori

Sr. QA/QC & Welding Engineer

-----------------------------------------------------------

PG-Dip. in Welding Engineering (IWE  AT  0070)

BSc. in Civil Engineering (IUT)

BGAS Painting Inspector

ASNT Level I&II

                        

On Fri, Jul 12, 2019 at 8:49 AM Ramin Kondori <raminkondori@gmail.com> wrote:

It should be available online.

But to fully understand it I recommend the following:

First, if you should check the filler metal certificate or specification, you can easily spot these elements in chemical analysis requirement and report.

Then you can search for the articles about the effects of these elements on mechanical properties (especially hardness) of the steel, especially after heat treatment. These elements have some kind of secondary hardening effect on steel which is only appreciable after tempering. On the other side, PWHT is usually in the same temperature range as the tempering heat treatment operates. Therefore, you should expect the same effects & results which include an increase in hardness. 

To have a better idea on this subject, just look for the heat treatment methods for increasing strength and hardness. Many of them include adding these elements to the alloy and then subjecting the steel to a QT or NT heat treatment. You will see the connection.

Regards

Ramin  Kondori

Sr. QA/QC & Welding Engineer

-----------------------------------------------------------

PG-Dip. in Welding Engineering (IWE  AT  0070)

BSc. in Civil Engineering (IUT)

BGAS Painting Inspector

ASNT Level I&II

                        

On Fri, Jul 12, 2019 at 7:52 AM Raghuram Bathula <raghurambathula@gmail.com> wrote:

Intersting Mr Kondori

Do you have any refernace or research paper on this subject?

Thanks

On Thu, 11 Jul 2019 at 09:23, Ramin Kondori <raminkondori@gmail.com> wrote:

Hello,

ER 70S-2 is a triple deoxidized steel welding wire. 

It has Ti, Zr, and Al additions (please check your filler metal certificate).

After PWHT, these elements can increase the hardness of weld metal (but not HAZ or base metal). Many do not consider this when choosing filler metal.

 

I recommend you to conduct a chemical analysis examination on both the filler metal (rod or electrode) and production weld metal and revert back to us. 

Regards

Ramin  Kondori

Sr. QA/QC & Welding Engineer

-----------------------------------------------------------

PG-Dip. in Welding Engineering (IWE  AT  0070)

BSc. in Civil Engineering (IUT)

BGAS Painting Inspector

ASNT Level I&II

                        

On Wed, Jul 10, 2019 at 2:11 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.

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