Maybe it wasn't luck, you just done a good job. I'm thinking it may have been ok without doing any preheat or slow cool.
Just my opinion,
I know everybody gets into that preheat thing with cast. I did too.
But for the life of me I can't understand how it would make a difference unless the part was heated almost to melting point, kept there during welding and controlled cooled in a furnace.
If the molecules / atoms / space lattices or what ever are not able to move how can the preheat help? Glowing red at close to liquid during welding would allow expansion and contraction but just hot wouldn't do that.
Now to contradict myself, at work we measure in microns, just picking up a part, the warmth of your hand expands the size, this is steel. I can not understand.
I've Tig welded cast, no preheat no problem, next time may be different.
Results 11 to 18 of 18
Thread: Cast Iron
10-11-2013, 01:45 AM #11
10-11-2013, 06:04 PM #12Member
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Hardrock40 i hear ya. I haven't welded much cast iron or steel but so far ive been blessed with good results. The vice i welded up with 7018 is still working but i make sure i don't wack on it with a big hammer. I do find that i am learning everyday the more i weld and i must say i do need more skill to make my welding as good as most on this site........HH 210MVP
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10-11-2013, 08:34 PM #13Senior Member
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It's not that it can't be done cold, but for me it's how it can be done best. In welding almost always Preheat is one of your closest friends. Very rarely will it hurt u and almost always it will help you. Like wise with post heat or simply cooling slowly.
If you work with alloy steels 4130 - 4140, heat treated, Preheat and slow cool is a must unless working with thin metal.
Personally I put cast iron in same class and for me I just always use preheat & slow cool. Even when I Tig cast.
Do a search and type in "Weld HAZ" read and understand the heat affected zone and how it applies to almost all weld beads.
Was just talking to a older timer than me :-)
Week or so ago. He told me he always Pre heated any metal 1/2" or thicker.
Well I can't say that cause I'm always in a hurry and I don't preheat as I should but I respect him for his dedication to quality.
10-12-2013, 12:56 AM #14
Yes I like preheated welding also, but like you say I don't always take the time to do it.
I'm just not sure it helps with cast you expect might crack unless you take it to the limit.
HAZ is the most scary thing in my life.
10-12-2013, 06:54 AM #15
Good Ole Cast Iron
You can weld cast iron "hot" or "cold".
Hot means that you preheat as much of the piece as possible as hot as possible without going over 1400 deg. F. After every pass, while the bead is still glowing if possible, peen several times. And then slowwwww cool. The preheat is done to help aleviate carbon migration in the HAZ and causing brittleness and the peening is done to help stress relieve so the brittle HAZ is not overstressed and crack.
Cold means to preheat to a minimum of 400 deg. F and weld just 1/2 to 3/4 inches at a time, peen, reheat, weld. Do this till your done and slowww cool.
It is all about reducing the amount of carbon that will migrate to HAZ after welding.Which we all should know what happens when there is too much carbon in one spot.
And always use a nickel filler. Whether it is a 55% or a 99% nickel filler will depend on the situation.
And those of you that have welded what you think was cast iron with a mild steel filler, was probably cast steel not cast iron. If it was cast iron, consider yourself one of the luckiest people in the world that it hasn't cracked.JIM
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10-13-2013, 02:02 PM #16
I can and have for years with Crown Alloys 44-30 CI Mig wire...BobBob Wright, Grandson of Tee Nee Boat Trailer Founder
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10-14-2013, 12:20 PM #17Senior Member
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As long as a cast part you are trying to repair is not constricted while welding I find the result are usually favorable as the part is able expand while welding and contract while cooling. When trying to weld a constricted part like a crack in the side of a cast engine block, you are very likely to have cracking occur as the expanding cast iron can't go anywhere it thickens instead, then while cooling it try's to contract back to its original position but instead pulls on the rest of the casting enough to crack.Miller syncrowave 200 runner with coolmate 4
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10-21-2013, 09:19 AM #18Junior Member
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