Two questions...

The first is about welding cast iron. I know that you need a DC Stick welder and that you need to preheat the joint to be welded, not so much as to melt it but enough so that the weld or the surrounding area does not crack when it cools. I also heard of Brazing being used also. Does all that seem correct so far? Are there any other methods and/or preperation I need to know about?

The second is about welding dissimiliar metals. I need to weld a 90 degree joint between stainless and mild steel, How is this done? I have a Hobart Handler 175 MIG welder, would this one work? If so, which wire do I use and any advice on voltage and wire speed would be appreciated.

Just to let everybody know, I am fairly new to welding. Thanks alot in advance.

Reply to
xyz789
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for question #1

not so sure about NEEDING the dc stick; according to the lincoln handbook AC will work their specialty rods; the book seems to indicate there are 2 basic strategies: either keep it as cool as possible ie: short, back stepped stringers w/ manual peening, or get the thing hothot and keep it hot all the way through to let it cool all together slowly

Reply to
dogalone

For dissimilar metals use a stainless filler.

309L is very popular for this. You can buy a small 2 lb. spool of MIG wire . Just remove the normal hub from your handler, and you will find a smaller shaft that the 2 lb. spool will mount on.
Reply to
Ernie Leimkuhler

You can weld cast iron "cold" with 99% nickle, welding only very short sections at a time, peening (hammering with a pointy hammer, such as the pointy end of a slag hammer) the weld bead while it still hot and continuing peening until it cools, then putting another stich in and doing the same thing - DC is not required. The peening helps to stretch the weld bead material so that the cooling weld bead does not crack the cast iron as it shrinks. You cannot wait any significant amount of time after putting the bead in to start peening it - ideally, it will still be red when you start hammering.

Grind the section to be welded open (90 degree V) leaving just enough of the craked surface to line the parts up, drill out the end of a crack if you are welding a crack, rather than a piece that has broken all the way off.

Often much easier than lots of preheat & postheat, and you don't have the opportunity to beak the casting elsewhere with preheating and postheating stresses.

If it's an exhaust manifold, a junkyard replacement is often less of a headache - exhaust manifolds are one of the more miserable parts to weld succesfully.

Reply to
Ecnerwal

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