Simulation Heat treatment of Mechanical test coupons of Raw materials. 3

[DK44]

1. What is the background of specifying Simulation Heat Treatment of Mechanical test Coupons in ASME Sec VIII div 1.
2. Does all classes of materials (CS& LAS, HAS, NF) require it. If not what is the exemption basis.

 

[david339933]

Check out UG-85, UCS-85, UHT-5(e), UHT-81

 

[DK44]

Dear David,
Thank you for your advice. While I am aware of the code requirements, what I desired to know is:
a) about the basis of asking for SIM HT of Mechanical test coupons for CS and LAS and whether such requirement is necessary for Stainless steels from metallurgical point of view or other considerations.
b) Is such HT required for pressure bearing Plates only or any other pressure bearing product forms like Forgings, Pipes etc.

Others also may please give their views.

 

[metengr]

The basis for requesting simulated heat treatment is to ensure mechanical properties during or after stages of fabrication have resulted in bulk mechanical properties that are still above minimum requirements per the material specification.

The above only applies to metals that can be hardened by heat treatment. Austenitic stainless steels not hardenable by heat treatment would not require simulated heat treatment.

 

[david339933]

All pressure parts regardless of product form are applicable unless exempted. UCS-85(e)(f)(g)give exemptions.

 

[DK44]

1. Thanks metengr and David for your views and feed back on the subject.

2. However, Heat Treatment of welded or formed parts (especially in case of CS & LAS)is generally meant for relieving the internal stress and hence hardening phenomenon in HT does not appear to be relevant.

3. Is it then the criteria of hardening during Rolling / Forming / Forging / Bending / Pressing / Welding operations which affect the mechanical properties of the material, that call for such sim HT.

I am not clear on this.

 

[metengr]

2. However, Heat Treatment of welded or formed parts (especially in case of CS & LAS)is generally meant for relieving the internal stress and hence hardening phenomenon in HT does not appear to be relevant.

The issue is normalizing (N) or normalizing and tempering (N&T) heat treatment versus subcritical PWHT. Normalizing heat treatment can be done in lieu of subcritical PWHT, and as such, this must be simulated to ensure proper mechanical properties are achieved after N or N&T.

3.Is it then the criteria of hardening during Rolling / Forming / Forging / Bending / Pressing / Welding operations which affect the mechanical properties of the material, that call for such sim HT.

The question is what affect did the above activities have, if any, on bulk mechanical properties to ensure the material has the specified minimum tensile properties. Again, you are only looking at heat treatment, if performed, after receiving the plate from the mill with original specified properties.

 

[DK44]

From the foregoing, I understand that ASME with certain valid exemptions, considers that the mechanical properties of the materials can affect as a result of Heat treatment after various fabrication methods including welding, and accordingly it specified SIM HT of such materials to ensure that the the strength of materials used did not decrease below the limits of the basis of allowable stress criteria used in the design.
Am I right in such assumption?

 

[metengr]

Yes.

 

[212197]

metengr (Materials)
We specify requirement of simulated heat treatment of test coupon in raw material purchase specification of plate.

This plate will be used for forming a dished head. This dished head will have to undergo heat treatment after forming.

so we are carrying out simulated heat treatment on test coupon.

but we are not carrying out forming operation on test coupon. Test coupon is only straight plate.

Is it right to carry out heat treatment on straight (i.e. not formed) test coupon or it should also be formed & then simulated heat treatment should be carried out?

 

[metengr]

212197;
Yes. The simulated heat treatment need only be performed on the actual heat of material. Forming only introduces cold work that is removed upon heat treatment so the concern is the heat treatment only.

 

[212197]

metengr (Materials)

Thanks a lot.

 

[Don56]

The heat treatment should be performed on each heat and slab/batch as the mechanical properties of materials governed by A/SA-20 are based on slab not just heats of material.