Re: Braze a Block or Weld?

Posted by TAKE A SEAT IN THE FRONT ROW SONNY.... :) Vic S. on December 15, 1999 at 21:53:31 from (206.112.27.36):

In Reply to: Braze a Block or Weld? posted by TMAC on December 14, 1999 at 15:57:16:

Ok, Now your into it bigtime so you need to learn a little before you start damadging those parts.
It is best if you new what type of the many cast irons you have. Ok...you dont. So lets go to step 2. Cast irons dont expant like softer steels and irons. When arc welding the bead is hot and expanded to the max in the grove you are welding. The cast is cold and not expanding. Now you see as this molten bead is shrinking...the cast is trying to get hotter and expand. OPPOSITE directions you see. The bead doesnt bond to the cast and it pops loose. Oil leaks and water leaks love these little escape routes.
You should always preheat the cast to a light dull red with a torch. Use nickel rods for the nickel has a natural attraction to the cast iron. The crack should be grooved open with a cutting tool...not a grinding tool. Hand chisel is best if no power cutting tools. Grinders leave impurities in cast face that causes poor bond of weld bead. If you must weld without preheat (only on large masses of iron) weld only smal beads at a time no longer than 3/4". When bead is cool to touch you can continue. Meanwhile move to opposite end of crack and run another bead so you dont waste time waiting. Like tightening head bolts. Weld one here...as it cools weld over there...then inbetween...then back here again...you get it? Like spot welding. Object is the fact that if you cant preheat you dont want to heat from weld to cause cracking. SO SPOT STITCH. Also if you cant preheat you can peen weld bead with hammer lightly as it cools. This relieves stress cracks. Dont hammer it...peen it as if your tapping for testing its hardness.
If you go to farm stores you will find several types of rods. Forney makes some called Supercast and Nomacast. Also called Supercast 99.
The Supercast 99 have high percent of Nickel and are for castings that get hot. The bead is not cast so it will expand under heat. You need NICKEL rod to allow it to stay bonded to metal when the cast metal does not expand and the bead is getting hot and pushing then pulling as it cools.
Think of it as the rubber goo used in sidewalk expansion joints. This goo is the weld bead made of nickel. In order for it to work it must stick to the concrete. Our bead MUST stick to the casting. The nickel rods are machineable and drillable. Other rods by Forney called Nomacast are ok for COOL items that dont need machineing such as bulk buildup for strength.
If you dont have much experience welding already...you had better practice on an old project. I can assure you you will not be pleased for the first 10 attempts. I suggest getting some scrap and experience otherwise you will end up with only the SCRAP.

Good Luck and enjoy the welding!

PS...AC is used as it helps to aggitate out the impurities in the weld zone. Vic S.

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• Re: Re: Braze a Block or Weld? Russ 22:48:21 12/15/99 (0)

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