Microstructure in HAZ (ASME SA516 Grade 70 MTLTV)

[goodbadgood]

Hi Guyz,

Kindly help in analyzing the microstructure in the HAZ region of the welded plate (ASME SA516 Grade 70

Plates after welding are Post weld heat treated.

Just wanted to confirm if there is any harmful microstructure in the HAZ region which is making the impact values very less.

The plate microstructure is ferrite and pearlite however in the HAZ i am not sure if the phases are ferrite / pearlite or martensite.

 

[weldstan]

Assuming these micros are all the same magnification, there is considerable grain growth from one to another.

 

[metengr]

I would agree with weldstan given the limited information. Have you run microhardness testing to determine the effectiveness of PWHT? The microstructure to me does not look typical of a SA 516 Gr 70 HAZ.

 

[goodbadgood]

@Weldstan

Yes the magnification is same for all the photographs which is 200X. Yes this is my concern about the grain growth. Typically the grain doesn't look like this in the HAZ region.

@metengr

No have not checked yet. Its a good idea to see the hardness value. i will update you about the the hardness values once taken.

 

[weldstan]

Do take a look at the chemistry. While uncommon today, in the 1960's and 1970's, fine grain melting was done with columbium and/or vanadium additions without aluminum additions. When subject to PWHT the HAZ developed secondary carbide / carbo-nitride precipitates which adversely affected impact properties in the HAZ.

Is the photo progression from the top surface to the bottom surface?