Allegro Club International

[David Smith]

Hello,

When trying to make car body repairs on the front Valance it just melts.

I can weld 1mm thick steel together on a bench but when I go near the car it just melts.

I use a Mig welder, any tips or is just experience.

Thanks Dave

[Laurence]

You'll have to say what you're using - wire thickness, type of gas or is it gasless, thickness of plate etc.

If you're using .8mm wire, it's too thick. You need .6mm with .6mm tip.

If you're using gas the tip should be recessed into the shroud 2 or 3mm. You can buy mini tips which are short.

I use CO2 not Agrosheild, reduce the gas flow to give a cooler weld.

Reduce the amps if you keep blowing through.

Reduce/increase the wire feed until the noise of the welding sounds like frying bacon.

Practice on some offcuts of metal, gradually turn up the wire feed, amps, gas flow until you can run a weld with the bacon sound. When the weld has run in right, the weld will glisten like it's wet.

I avoid using a magnet to hold the metal plate in position because I find it affects the molten wire being fed into the weld giving a bad weld.

Tack the plate into place with a few tacks & tap the plate into shape whilst it is still hot & put a few more tacks & so on until the plate is in place then join the tacks with short weld runs using short bursts.

The panel should be freshly ground so there is no corrosion because any rust will cause spitting which will blow the weld everywhere.

The new metal plate edges should be freshly ground & grind 1/2" border around the plate - even when using new metal otherwise you'll get spitting.

Aim the weld at the new metal plate to start, then with a small circular action so the weld includes the panel, do quick/short runs.

If you don't want the panel to buckle with heat, leave the first weld run & start a new run elswhere on the plate or have a cuppa until it cools.

When you blow a hole in the panel, use quick/short bursts around the hole, then fill the centre of the hole with ever decreasing circles in quick/short bursts.

Use a flap disc to smooth off the welds because it gives a better contour & is not so aggressive.

[Laurence]

PS if you have access to the rear of the panel you can attach a copper plate to the rear of the panel which will stop the weld blowing through.

[David Smith]

Hello Laurence,

I use 6mm wire and Co2 only because that's what it came with. It has a recessed tip.

I have 1mm & .7mm plate.

What do you mean by grinding a "1/2 border" on new sections of plate?

Many Thanks Dave

[Laurence]

Hi David,

1/2" is half an inch.

Grind all around the edge of the plate, plus grind 1/2" border around the periphery of the plate.

Do a practice run to test the welder to see if it needs fixing/cleaning.

Check the wire feed wheel is positioned correctly, it can be removed so you can select 0.6mm or 0.8mm groove.

Clean any crud from the groove & set the tensioner wheel so it drives the wire smoothly without slippage.

Is the wire on the reel corroded? If so, buy a new reel of wire. Use a small reel if you have a 'hobby' welder (non-professional).

Cheers,

Laurence.

[Laurence]

I had a problem with my MIG welder, I overheated the gun which caused the plastic bits inside to melt so I bought a new gun assembly at Machine Mart.

It gave a much better weld.