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Up Topic Welding Industry / Technical Discussions / PWHT of 410 to 316 Stainless steel
- - By jjhall Date 09-14-2005 22:02
Trying to find information on a Post weld heat treatment cycle for 410 to 316 stainless. It is in an reactor effluent stream. Any information would be great.
John
Parent - - By - Date 09-14-2005 22:17
The carbon content of the 410 goes a long way in determining what the preheat and PWHT temperatures are going to be. The thickness of the material and the weld metal used to weld the 410 to the 316 will also play a role in this determination. If you can give us that information, we can better offer advice on any heat treatment.

Chuck
Parent - - By jjhall Date 09-14-2005 22:35
The filler would be ER410 and the thickness is from .550" to .750" some of the welds will be 410 to 410 and some 410 to 316. thanks for the reply.

John
Parent - - By - Date 09-14-2005 22:57
The function of a PWHT is to temper or anneal the weld metal and HAZ to decrease hardness and improve toughness or strength, and to decrease residual stresses associated with the welding process. The necessity of a PWHTdepends on the steel composition, the filler metal, and the service requirements.
For 410 steels with a carbon content <0.05%, the preheat should be 250F. For carbon contents of 0.05-0.15%, the preheat should be 400F. For carbon contents >0.15%, the preheat should be 600F. If the carbon content is 0.20% or greater, the weldment should be given a subcritical heat treatment immediately upon completion of the welding.
PWHT for 410 of .550"-.750" should be between 1200-1400F for each inch of thickness, with a 1 hour minimum. Air cool from PWHT temperature. The lowest hardness is obtained by heat treating at the top of the range.

Chuck
Parent - - By MBSims (****) Date 09-15-2005 00:08
Chuck,

How would this heat treatment time and temperature normally affect the 316L material as far as sensitization? We would normally weld an Inconel safe-end or buttering to the 410 with Inconel, perform the postweld heat treatment, then weld the safe-end or buttering to the 316L with Inconel electrode. We have observed the 316L can fail the ASTM A262 Practice A and Practice E tests after heat treatment at this temperature range and hold times.
Parent - - By - Date 09-15-2005 02:46
Marty,
I was primarily referring to the 410 to 410 welds. If the 316L material is of a >0.025% C, it should not be a problem at 1200F for one hour followed by a rapid air cooling. The lower the C content, the more time on the clock at temperature is observed. The lower C content of a 316L will generally slow down the rate of carbide precipitation so that sensitization in the HAZ is not a problem. As has been said in numerous threads, a 316L, for example, has a recommended heat treatment of solution anneal (approx. 1900F) followed by a rapid cooling. A butter pass on the 410 is probably the most safe method if there is any doubt.
Parent - By jon20013 (*****) Date 09-15-2005 12:42
John, listen to Chuck, he is one of the very best in the business with regard to stainless steels and I happen to be a very big fan of his, lol!

I have not had the pleasure of engineering a 410/300 series WPS but recent had to qualify one of our existing WPS' for solution annealing 304 stainless. We used 316L filler in that application.

I fully expected to have problems because of the configuration of the fabricated parts; 1/8 fillet welds around two members of fairly significant mass differences, but everything went beautifully!
Parent - By Geese_howard (*) Date 10-24-2005 04:58
I don't think PWHT on martensitic stainless should be given inmediately after welding. I think u should mantain preheat for an hour or so,allow to cool slowly to room temperature and give PWHT after that.
If u PWHT inmediately from preheat temperature, u dont get full quench after welding, so u will have much retained austenite, which will quench after PWHT (no transformation to perlite or bainite will happen because this require to much time on highly alloyed steels), so at the end u will have untempered martensite, that is bad news.

Parent - - By jjhall Date 09-15-2005 19:10
Thanks to everyone for the advise. Just for the record the 316 is not the Extra Low Carbon "L" grade. The recomendations to Anneal ( 1950f to 2050f ) then quech or cool rapidly for the 316 conflicts with the 410 recomendations ( AK Steel Data sheet) of 1500f to 1650 the slow cool in furnace to 1100f. My concern ( one of many) is that I will sensitize the 316 during the slow heating and cooling of 410 or that I will have cracking problems with the 410 if I follow the 316 cycle. I am again greatful for the help, this is a great forum.
Parent - - By - Date 09-15-2005 20:15
If this 316 is above the 0.03% C, chances are pretty sure that you will encounter sensitization during the PWHT. For the 410 to 410 welds, I'm not sure why you are doing a full anneal heat treatment. Full annealing transforms the multiple-phase weld zone to a largely ferritic structure with scattered carbides. It should not be used unless maximum softness is required because of the formation of the coarse carbides in the microstructure that take longer to dissolve at the austenizing temperature. Generally, a subcritical PWHT is done on 410 welds, 1200-1400F, but that is for you and your customer to decide. Other than buttering the 410 and then heat treating it before welding to the 316, as MBSims mentioned in an earlier thread, there is one other technique that has been used successfully. Preheat the 410 to approx. 600F with a 600F interpass temperature and use a slow cooling down rate through the martensitic transformation temperature. This technique can be used when a PWHT is not possible, and it will cool through the sensitization range of the 316 without any detrimental effects. This high preheat and high interpass temperature technique will also help control the cracking usually associated with the 410 welding. Just a thought.... It seems you have some decisions to make. Good luck.

Chuck
Parent - By jjhall Date 09-15-2005 21:09
Thanks again Chuck. I will post here to let you all know how this turned out.

All the best,

John
- By TOPDOWN23 Date 09-30-2019 23:58
I have a question about welding stainless. Lets just call out a 410 with a carbon content of 5% with a thickness of .550"-.750". the PWHT should be 600F -  When i have met all the requirements and let it cool while wrapped in an asbestos blanket and black light the weld, there appears to be a crack as if the weld did not melt the the stainless to the fill rod.  when ground out there never was any indication of a flaw.  What is going on? did we not hea treat it to the right temperature?

Referenced above for numbers.  otherwise everything is true
The function of a PWHT is to temper or anneal the weld metal and HAZ to decrease hardness and improve toughness or strength, and to decrease residual stresses associated with the welding process. The necessity of a PWHTdepends on the steel composition, the filler metal, and the service requirements.
For 410 steels with a carbon content <0.05%, the preheat should be 250F. For carbon contents of 0.05-0.15%, the preheat should be 400F. For carbon contents >0.15%, the preheat should be 600F. If the carbon content is 0.20% or greater, the weldment should be given a subcritical heat treatment immediately upon completion of the welding.
PWHT for 410 of .550"-.750" should be between 1200-1400F for each inch of thickness, with a 1 hour minimum. Air cool from PWHT temperature. The lowest hardness is obtained by heat treating at the top of the range.
Up Topic Welding Industry / Technical Discussions / PWHT of 410 to 316 Stainless steel

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