Hi

Did you verify if it is necessary to do pre heat? Because it is a ferritic stainless steel.

do the Post weld heat treatement

Hello,

Many problems can be associated with the welding of Ferritic stainless steels : Cold cracks caused by Hydrogen, intergranular cracking when no stabilizers like Ti or Nb are used, grain growth causing ductility drop and 475°C embrittlement (spinodal decomposition of alpha ferrite in alpha prime). The topic is vast but I think that next article is a good approach : https://app.aws.org/wj/supplement/WJ_1981_08_s135.pdf

The material is T22.

I am looking for a case or research where after welding the cracking has occurred in the base metal and not in Weld Bead or HAZ also called as Type 5 cracking.

Ductility drop, as rightly mentioned by @Jean-Pierre Van Nieuwenhoven , is well documented in 304or 316 SS or SS in particular, but I am interested in T22 and a possibile mechanism and can the same be extrapolated to Ferrtic class.

In the case of a T22 ferritic steel, we are in the domain of creep resisting CrMo steels which are not stainless steel types. In the present case, cracks appearing in the HAZ are more than probably cold cracks. Those cracks are caused by transformation of the original ferritic structure into Martensite inside the HAZ. In the presence of diffusible monoatomic Hydrogen and residual stresses, cracks may appear in this HAZ. As the development of cracks depend essentially to the simultaneous existence of these 3 conditions, it is possible to eliminate 1 of these 3 conditions to avoid the cracking occurence. Most of the time, a redrying of the welding consumables (in case of stick electrodes or submerged arc flux) and the use of a preheat (say 150°-200°C) of components to be welded followed by a slow cooling after weld completion are sufficient precautions to get a joint without crack in the HAZ.

Hope this might be helpful.

They may be just stress cracks from poor fit-up and not allowing cooling strains to be relaxed. Does the weld over, equal or under match the base material and what is the weld configuration - PJP or CJP?

Jean-Pierre Van Nieuwenhoven Thank you for the answer. What we were dealing with was a failure analysis.

The Tube had a fin attachment and there was a HAZ region but some 100-200 microns away in the base metal region there was a large crack, circumferential crack, which grew inwards and led to puncture. The crack appeared to have a thick oxide scale also which we believe was due to service condition.

But somehow, I do not believe that. There is cracking in weld samples wherein after welding base metal cracks (I think it is Type 5 or 6 cracking), possibly due to ductility loss as that in SS, but I had trouble finding research articles and experiences that show the same in Ferritic Steels.

It is intriguing why ductility loss occurs in one class of material and not in another, which is a very bad question to ask. So I am trying to learn more about it.

Thank you everyone for your time and efforts.

Cracking in ferritic stainless steel after welding can occur due to several reasons such as hydrogen cracking, solidification cracking, and reheat cracking. The cracking can be prevented by controlling the heat input during welding, preheating the base metal, and using low-hydrogen welding consumables.

If the ferritic SS weld set-up is a tight fitting before welding then after the weld is made and solidifies it must contract and if there is no ability to yield then base material combined principle stress will reach UTS and fracture with limited plastic deformation.