Test coupon Mechanical Property after PWHT

[RAJMETALLURGY]

Material: ASTM A352 LCB
Test coupon: 80 mm thickness, Length: 250 mm, width: 125 mm
Heat Treatment: Normalizing 930 Deg C, Quenching 910 Deg C, Tempering 650 Deg C
Mechanical Property: Yield 341.77 MPa, UTS: 506.55 MPa, Impact average 30 Joules at -46 Deg C (required 27 joules).

Simulated PWHT was carried out on test coupon after the above heat treatment NQT at 593 Deg C. Mechanical Property after this

Yield: 298 MPa, UTS: 465 MPa, Impact average 15 Joules at -46 joules

Can u pls tell me the reason for mechanical decrease after PWHT. Please help me.

 

[metengr]

Upon exposure to extended subcritical PWHT, there is continued softening or tempering, which results in lower mechanical strength properties. This is the reason for mechanical testing after simulated PWHT holding time.

 

[RAJMETALLURGY]

Thanks for your reply, Is there any other way to improve the tensile and impact value to meet the requirements. And is it necessary to meet the material specifications after PWHT.

Please advice.

 

[metengr]

No without re-heat treatment. No, for non-impact application.

 

[RAJMETALLURGY]

Reheattreatment means, we have to do Normalizing, quenching , tempering & PWHT.

please clarify.

 

[metengr]

Normalize and temper.

 

[RAJMETALLURGY]

As per ASTM A352 for LCC material the mechanical properties are

UTS: 485 - 655 MPa
Ys: 275 MPa Min
Impact: Average 20J @ -46 Deg C.

Will it be the same after PWHT also. Please clarify.

 

[arunmrao]

RajMetallurgy, how much more clarification do you repeatedly need, despite patient and excellent response from "metengr". Please do your own homework too.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[metengr]

Will it be the same after PWHT also. Please clarify.

Perform the weld procedure qualification, heat treat, tensile and impact test, and evaluate the results. You have to do this regardless.