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Up Topic Welding Industry / General Welding Discussion / Field Crack Repair in CS using SS
- - By dbid Date 05-27-2003 21:33
Application: Earthmoving and Construction equipment
Subject: The field-repair of cracks which form in carbon and low-alloy steel weldments, using stainless steel weld metal.
Issue: For many years there have been stories of successful crack repair, when other methods have failed, by using stainless steel weld metal instead of carbon or low-alloy steel weld metal. I'd like to hear from others about their successes and failures based upon using this approach. Also, explanations as to why this approach may (or may not) be valid.
Parent - By insp76 (**) Date 05-28-2003 02:42
dbid, sounds like the equipment your dealing with is being subject to what I call cyclic stress, one way to deal with this is to pre heat to stress releive the area and hopefully avoid cracking. Prior to welding pre- heat to 300 deg.F a area 4 inches on each side of the weld,during the weld do not let the innerpass temperature exceed 600 deg.F, when the weld is completed ,rap the area with k-wool so the weld area will cool slowly and avoid embrittlement and cracking. I would also suggest useing e-7018lh filler material. There are other ways of achiveing this but this is the cheapest and quickest way. If the design or configuration of the equipment is wrong there isn`t anything you can do about that unless you attempt to change it. Good luck hope this helps
Parent - By GRoberts (***) Date 05-28-2003 14:34
There are several advantages to using austenitic filler metal when repairing carbon steel. First of all, the austenite can dissolve more hydrogen than ferrite. So the weld does not reject as much hydrogen into the base metal/HAZ during cooling, which reduces that chance of hydrogen cracking (underbead cracking). Second, the austenitic filler metal also is more ductile than the surrounding base metal, and depending on the type of material you are welding, often has a lower yeild strength. This means that the residual stresses that are left after welding are less since the residual stresses are about the same as the yield strength of the weld and/or base metal.

The disadvantages of using austinitic filler metal is that if the wrong kind is used, or wrong dilution achieved, the weld deposit can end up being non-austenitic (it would be martensitic), which would have a tendency to crack on its own. Austinitic fillers even when used properly also form a thin line of martensite next to the base metal due to segregation during solidification. Most of the time the layer is thin enough that it doen't make a big difference, but in cases where it does, nicke based filler metal can be used, such as ENiCrFe-2 (Incoweld A)
Parent - By billvanderhoof (****) Date 05-29-2003 04:55
Being a fellow who believes that crack repair starts with crack removal (I usually use a torch) filling with stainless takes away options if you have to do it over. The torch won't work, and most stainless loads grinders. There are of course still other ways to get it done but you need to carry more stuff.
Bill
Parent - - By DavidP66 (*) Date 05-29-2003 17:24
From what i was always taught in school...when fixing a crack you should locate where the crack starts and stops...drill one tiny hole on each end..about 1 inch farther down from where it starts and stops.....along with a preheat of 300 degrees (as mentioned above), welding with low hydrogen electrode, and a very slow cooling method..wrapping it in fired retardent cloth or alike....all same as mentioned above but with the holes drilled into it...i always heard this can keep the crack from possibly going futher.

David
Parent - By billvanderhoof (****) Date 06-03-2003 03:08
Grooving out the crack gives me a place to put the repair. I have trouble guessing where exactly the end of the crack is so I can drill the hole but it seems easy to follow it with the torch. Just me. Grooving it out also eliminates a possible stress riser from the remains of the crack. Many use the method you describe with good result.
Bill
Parent - By Niekie3 (***) Date 06-02-2003 19:46
Hi dbid

There are specially designed "stainless steel" fillers for welding so called "difficult to weld steels". A favourite is the 312 filler. These fillers are typically so alloyed that you end up with a 50% ferrite and 50% austenite weld deposit. This gives you the best of both worlds in relation to a weld deposit being forgiving to contamination, hydrogen and gives you a little extra ductility. This is a tried and tested method.

Regards
Niekie Jooste
Fabristruct Solutions
Up Topic Welding Industry / General Welding Discussion / Field Crack Repair in CS using SS

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