weld hole in 3mm sheet without distorting

Hi everyone

I need to repair a flat sheet fabrication in 3mm steel without distortion. It's had two slots 6mm wide x 70mm long the semi-circles of a 13mm hole at the mid-point put in it. Slots are lengthways-on near each end.

Sheet is 660mm wide and 1700mm long, with angle-iron reinforcement around the edges.

Want it to be smooth so easy to scrape clean - used in dewaxing autoclave of lost wax foundry.

I thought:

Cut out a piece of metal which as closely as possible fits each slot - same 3mm thickness.

Cut some say 12mm plate about 120mm long and 50mm wide and attach with a series of shot tacks to the underside. Big enough to hold the sheet flat but small enough that tightly restrain the weld area.

Pack height from workbench so can hammer in that area

Weld the "filler" in place fast, highish current, small bead - then hammer the weld immediately afterwards to counteract shrinkage

Grind flat.

Cut off thick restraining plate with angle-grinder.

Turn over - seal weld that side too in same way.

So that's my idea - how should I really do it?

Thanks in advance

Rich S

Reply to
Richard Smith
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All good ideas. You might want to warm the whole plate a little to reduce localized thermal distortion.

Reply to
Ernie Leimkuhler

Can you leave the backing plate on it?

Does it have to be a full weld?

What about tacking a plate on the back side, then floating a metal or epoxy into the gaps. Using a lead or brass filler to keep the heat input down...

Depending how hot the autoclave gets, there might be a metal bearing epoxy that would survive.


Reply to
Stuart Wheaton

Thanks everyone. Looking at it in the light of day I decided a metal blanking plate screwed on would be just fine. Completely flush can be had by tapping 3mm holes in the 3mm plate and screwing on back plate with "filling" metal shape brazed / tacked on - linishing front surface to get smoothness across screws and "plug". And none of this may be necessary - find out tomorrow if get spitting of wax-and-water through holes in baffle. Much appreciated -- Rich S

Reply to
Richard Smith

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