woodstove repair problem/question.

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I have a woodstove that's at least 20 yrs old and has been used for 18 that I know of.my grandfather took two woodstoves (a Fisher and a Roanoker) and had the local welding genius put them together.  The only real signs of wear are the internal firebrick rack and some of the FACTORY welds have popped loose due to poor penetration. I've already removed and replaced the angle iron tabs with a homemade replaceable rack that will be easier to fix and easier to do the yearly check/replacement for the firebricks ( tonight actually).  When you get a fire going the stove ticks and clicks due to thermal expansion. Replacement is not an option at this time.All that's needed is some welding on the outside and some added reinforcement for peace of mind.  This is all well within the capabliltiesof my equipment and my skill level.My questions are: Should I weld it when its HOT or when it's room temperature?  Do I need a particular rod or will just general purpose rods do?
Reply:Depends on whether or not the areas you want to weld are cast iron or steel.  You can try a spark test with a grinder in an inconspicuous place to attempt to figure it out.If the stoves are steel, then you can pretty much weld it any way you want to.  If it looks like the stoves are cast iron, then you have a more challenging repair to make.  Pre-heating the area of the repair and slow cooling will be 100% necessary with cast iron.  You'll want to use a filler metal that contains a lot of nickel.  Most places sell cast iron repair rods that contain either ~60% nickel or 99% nickel.  One rod produces a weld deposit that is machineable, the other doesn't.  Which one you choose depends on the cosmetic requirements for the repair and your welding skills.  In either case both rods are expensive, so make sure you're certain you're working with cast iron and that the repaired stove is worth the cost in materials.I don't recommend welding in the living areas of your home because of the sparks/smoke/fire hazards.  But, you might consider moving the stove outside, and pre-heating it with a torch.  Or, you might consider(depending on the nature of the repair) building a good fire in the stove, allowing the whole stove to heat up to at least 300 degrees, and then allow in the stove to slow cool after the repair is complete.  This would be ideal with regards to minimizing the chances of a cast iron stove cracking after welding.I'd recommend brazing, except that being this is a wood stove, I think it's conceivable that it could get hot enough to compromise a braze repair(depending on the location of the repair and how hot you fire the stove)...It's impossible to give better advice without pictures and more info on the nature of the repair work.  Good luck.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Originally Posted by A_DAB_will_doDepends on whether or not the areas you want to weld are cast iron or steel.  You can try a spark test with a grinder in an inconspicuous place to attempt to figure it out..I'd recommend brazing, except that being this is a wood stove, I think it's conceivable that it could get hot enough to compromise a braze repair(depending on the location of the repair and how hot you fire the stove)...It's impossible to give better advice without pictures and more info on the nature of the repair work.  Good luck.
Reply:Just being extra conservative here, because I really don't know where the repairs are located, and just how hot his stove can get.  The woodstove in my living room is small, and I can stoke it up to the point that the thermometer I sit on its top will read 400 degrees F.  Who knows just how hot some of the internal areas get, when the outside is 350-400 degrees F.  Also keep in mind that a braze, just like most other materials, is going to lose strength as the temperature rises.  This could be an issue as the stove expands and contracts during normal use.  I don't know how a braze repair will respond to that cyclic thermal stress....I'm not saying it won't work, I'm just saying I don't know... Originally Posted by weldbeadi dont think a woodstove gets above 500 degrees does it? isnt braze ok at that temperature?and as has been said,for welding  if the stove is hot its ok for steel and mandatory for cast...
Reply:Both of the original stoves were steel with cast iron doors;  the parts I'd be welding on I KNOW are steel. The stove is freestanding in my basement and I can get it to the doors if necessary.  Like I said, the repairs and reinforcements are well within my capabilities.  I was just worried about the thermal cycles stressing them.  Talked to some guys at my church who each know more than me. they both figured that the poor penetration factory welds that popped loose were done by someone with a wire welder in a hurry.  One said go ahead, no problem.  The other thought I might want to do it hot if penetration was going to be a problem.  I assured him that it wouldn't be.  I'll be using a stick welder on material that's 3/16ths to 1/4" thick.  The rods I'll be using work just fine on either.   Since I haven't gotten any "Danger! Danger!" messages messages regarding the thermal cycling I'll go ahead and weld it without a fire in it.  It'll be easier and much safer for meThanks for the replies.  I'll let you know how it goes.
Reply:LOL - If the welding is inside the firebox DON'T use a grinder.  Ask me how I know You wouldn't believe the ash that can fly from the turbulence around a grinder.Was a real hero with my wife after that one.Gordie -- "I believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant."
Reply:Just my two bits...I know for sure that my wood stove has been over 500 deg. F  many times.Me thinky brazing not good.
Reply:Originally Posted by daddyJust my two bits...I know for sure that my wood stove has been over 500 deg. F  many times.Me thinky brazing not good.
Reply:we had a stove that needed welding at the deer camp.  we grooved the joint we needed to repair and then built a hot fire in it.  we welded the joint while hot and then never looked back.  the long burn and slow cool is what the doctor ordered for that cast beast.  we welded it up with 7018.