Reply by CaptainKlutz

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Posted on Hand tool repairs (welding cast)

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3844 posts in 2414 days

#1 posted 10-01-2020 08:32 AM

Stick welding works well on cast iron. As I got older, my stick welding skills have degraded and weld seams look like drunk person made them. #IAMAKLUTZ MIG gun gives this old man more control. :-)

Have had decent success using .030 309 stainless steel wire for MIG welding cracked cast iron with a 220v welder. Half or third the cost of Ni55 wire with less finicky setup. Plus can use same 75/25 gas mix used for mild steel.

Use gas torch preheat, tack ends, check preheat again, then bead weld in small sections, reheating if work is going slow. Once welded, immediately place it into bucket/pan with sand in bottom, and cover the piece with sand to cool for 24+ hours. No peaking until below ~150°F!

Tips FWIW:

Sand has to be DRY. DAMHIK
Play sand needs to be baked at low temp for couple hours to remove moisture. Then I store cool sand in 5 gal pail with lid. Suggest BBQ or outdoors in sun due musty smell.

For thicker ARN with only a crack – drill a small hole at end of crack to prevent it getting worse while you weld.

One key for better welds on CI is to be aggressive with the grooving. Usually only leave 35% of base metal in thick repair, ~50% web on thin wall plane. This helps to reduce the post grind, and offers best penetration. Prefer to use rotary carbide burr to make groove, instead of disc grinder. The carbon tends to smear with grinder and creates more voids and pin holes at edges.

If the piece if broken in two and have gap; the gap can be supported on backside with thick (1/8-1/4 inch) piece of copper plate to cover gap. This helps prevent burn through at edges, and tends to provide a flat back surface with minimal grinding. Put a quick base bead down in gap on top of the copper, and then finish the fillet to avoid putting to much temperature into copper.

Can not hide the SS wire weld repair with grinding, like you can with Ni55 wire. SS weld tends to polish up and shine more than ARN due chromium.

Understand this thread is about hand tools, but want to add that thin wall cast iron on plane/scraper is much easier to wire weld than thick section of large ARN tool. Have repaired a couple cast iron cracks on vintage TS trunion/arbor using SS wire. Takes a massive amount of preheat to reach 450-500°F range needed to reduce cracking due larger mass. (Buy and use a non-contact pryometer or some wax temperature pencils).

Last but not least:
Welding ARN doesn’t not always work. Attempted to SS mig weld an Taiwan band saw parts made around 2000, and only made cracks worse. Welding forms suggest the problem was quality/type of CI from overseas? Sounded like bowl of metallic rice krispies as soon I finished welding (due metal cracking as it cools/contracts). Had to resort to brazing that tool.


-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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