normalization after hot forming 1

[johnytringuyen]

Dear Sirs,
I am doing review specification for high pressure vesels ((thicknes above 150mm), in the spec mention that the subsubsequce normalised is requiered after hot forming event the base plate already done normalised. I dont agree with that due to double normalised, it to be exspensive and may be impact mechanical properties.
I did comment require only stress relieve after hot forming instead of normalization.
pls help to advice is it correction or not??and advice which is best solution for thi.s?
pls help to advice.
John.

 

[metengr]

John;
Sorry but your post is confusing. What construction code are you using for the review?

 

[johnytringuyen]

Dear Mr.Metengr
the presure vessel is designed as per ASME XIII Div 2, I have checked code but this is not required normalised after hot forming (matterial for construction: 516 grade 70 N.
regrads,
John

 

[metengr]

John;
If the material was subjected to hot working, where the material is in the austenitizing temperature range, and after working is cooled in air or other means (for rapid cooling) from the austenitizing temperature range, a re-normalization treatment is not required.

However, if the hot working was performed and the temperature fell below the austenitizing temperature range prior to air cooling, re-normalization is required.

 

[johnytringuyen]

Dear mr.Metengr,
Thanks so much for your advice.pls help to provide code requirement as your mention for further information.
Do we need stress relieve for hot forming?is it better than without any heat treatment after hot forming.
Regards,
Johny

 

[metengr]

You should not need to stress relieve after only hot forming. Re-heat treatment would be necessary based on the previous post.

 

[johnytringuyen]

Mr.Metengr,
Pls advice how control and monitoring 'the temperature fell below the austenitizing temperatur range' during hot forming to make sure no need normalizing and what's mechanical testing to confirm no changing mechanical properties for hot forming? Isn't it tensile and impact testing.
Regards,
Johny