Stress Relieving 304/316 SS
Stress Relieving 304/316 SS
(OP)
After welding, is there any reason why you would stress relieve...
304/316 SS
304L/316L SS
400 series SS
Other Stainless steels???
Aren't the benefits minimal???
304/316 SS
304L/316L SS
400 series SS
Other Stainless steels???
Aren't the benefits minimal???





RE: Stress Relieving 304/316 SS
I think the same applies to the 400 series ferritic SS's.
RE: Stress Relieving 304/316 SS
You can sensitize SS around 800-1100F can't you??? Would you stay below that or quench above it???
What temperature/method would you use???
RE: Stress Relieving 304/316 SS
Good thing: you get rid of residual stress which can cause SCC.
Bad things: 1.you can sensitize if carbon is not low.
Avoid 600 to 900C unless you have an L grade.
2.You can cause delta ferrite to form sigma
and lose corrosion resistance.
Little known fact: If you anneal at high temperature ,say 2200F for one hour,the weld will have the same corrosion resistance as the base metal instead of having a critcal pitting temperature 10C lower.
RE: Stress Relieving 304/316 SS
I have a 316L formed head welded to a 316L body flange. Is there a proper heat treatment process for removing the residual stresses associated with the forming process??? My experience is SCC will originate in the dish and knuckle portion of a formed head first and not the weld area.
RE: Stress Relieving 304/316 SS
Essentially all our plan site is comprised of process vessels constructed of, 304, 304L, 316 S/S. We have tried at various time to stress relieve vessels or piping to prevent SCC , mainly of the Chloride variety. I can say that in all cases stress relief wasn’t worth the time and money spent for what little benefits achieved, most of the time were not measurable. We have chlorides coming both from the inside and outside. As most of you know insulation is one of the biggest culprits, even with low chloride insulation. In a hot 120̊C high HNO3/Organic area we have Nitrosyl Chloride that will attack and crack butter.
In some very specific cases if you had just evaluated the data you would have said that stress-relief made things worst. We saw far superior results with stress relief of C/S (for NH3, Amines) than we ever saw with S/S. As mention in previous posts the actual process of stress relieving S/S is fraught with problems and possibilities of thing going wrong. We had them all. We also tried to use Quench Annealing again not worth the effort as a post fabrication process.
As most of our problems steamed from chlorides our sister plant had problems with thio-chemicals. They also didn’t have the success with stress relieving as would have been expected.
On the head problem which side is the SCC occurring inside or outside? We have had heads QA after forming but not after welding. It was an add on to the cost even though it was that great of an effort.
Metalguy,
The ferritic 400's, especially 430 S/S, have to be annealed if welded on.
RE: Stress Relieving 304/316 SS
For a discussion of this stabilization anneal see "Stress Corrosion Cracking Susceptibility of Stainless Steels and Nickel-Base Alloys in Polythionic Acids and Acid Copper Sulfate Solution" Carl H. Samans, Corrosion, Vol 20, August 1964.
James Kelly
www.rolledalloys.com
RE: Stress Relieving 304/316 SS
RE: Stress Relieving 304/316 SS
Will shotpenning help??? I personnaly don't think so since we're inducing compressive stresses.
What about 321/347SS... is it worth investing it that???
My thoughts are unless we have a known material in this service (which we don't) we better not fool around....Alloy 600.
RE: Stress Relieving 304/316 SS
http://www.metalimprovement.com/
RE: Stress Relieving 304/316 SS
I am also new to the idea of heat treatment.
How would I go about relieving stress using heat and are the methods universal for all SS?
RE: Stress Relieving 304/316 SS
A bit off topic, but thought I'd make the point...
The 'usual' stress releiving temperature of 600 C applies to carbon steels. Other alloy steels are stress relieved at usually higher temperatures - P22 for instance at 700. There is no universal stress relieving temperature.
Dont disagree with the other stuff in your post.
Regards
Andy