"No-PreHeat" Cast Iron Repair Technique

[Sandy]

Nope no problem. I really don't have a meter just taps so i just play it by the job...Bob

Good deal, thanks.

[Portable Welder]

Weld On Welding, I have often thought of trying silicon bronze but never have.

I have been using a good old oxy/ acyt. torch for years with great success, However when its a chunk of cast that is to big for the gas grill ( Engine block )

I have resorted to using a crown product called 55/45 with tig and do it cold, I have also arc welded it cold.

Plain and simple there are more than one way to skin a cat.

Now when I say cold, That doesnt mean no heat, I still warm the area as much as possible without melting wires.

[aaronobrien]

When doing a repair like this (ie: transmission, gear housing, etc.) what do you use to prep/clean the weld area? What if you cannot get to the backside to scrub...???

A year or so ago I had a pump from a crane needing to be welded, but I always got crap in the weld, no matter what I did the the top (area of weld) to claen it, so i assume that the contamination came from the backside.

[aametalmaster]

Thats the hardest part is getting the junk out of the crack. A torch works the best if there is no other way like with solvents...Bob

[MR.57]

Lock-n-stitch put together some good information explaining expansion and contraction and made it freely available. I have made many cast iron weld repairs in my career and no matter what process you choose, understanding how the part expands and contracts is essential if you want the repair to be anywhere near as strong as original.

At first I thought the video was going to be an ad for their product, but they do not make a single mention of Lock-n-stitch pins throught the entire demonstration. It does however, provide an excellent visual illustration of what's going on when you heat a casting unevenly. I'd consider them an authority on cast iron repairs and they do a nicer job than I can of explaining what's the main problem with making repair welds on non-preheated cast iron. Watch to the end, it's boring at first but gets more interesting towards the end.

Here's a link to the page with the video:

http://www.locknstitch.com/CastIronWelding.htm

(Click on "Cast Iron will obey the laws of physics, even if you don't know them" at the bottom)

In my opinion, the only way to get a perfect cast iron repair is to do it the old fashioned way which involves heating the entire part to critical temp and welding with cast iron rod and then slow cooling the entire part. Peening or not, any other method is going to leave a lot of residual stress in the casting which can lead to cracking.

Of course we all know that not every repair needs to be perfect, sometimes "good enough" is just that, good enough.

[aametalmaster]

I have seen their vid and even some repaired work but the lockstitch can't be used in every repair job because of how the parts broke or the cost so we have to do it the new old fashioned way I just did a 20 thousand dollar hyd pump case where the ears were broke off and welding was the only way...Bob