Mig Welding gas pressure

[Dbarnes72]

I'm filling in some rust pinholes and of course it's blowing thru. Will lowering the shielding gas pressure help reduce this or is it all in speed and technique.

 

[RIbronco]

The blow through is from the amount of heat, not the flow of shielding gas. If you can, try to turn the amperage down or reduce duration.
Turning the gas flow up may actually help. It will provide some additional cooling.

 

[Broncmeister]

the gas is a shield to allow for a better weld, decreasing it would actually be worse. In fact, pinholes are essentially a but weld as there is no surface that extends vertically from the hole you are trying to fill, therefore lowering the pressure would actually be worse because there is no vertical piece to help keep the gas at the weld. Can you decrease your voltage and line speed?

 

[Dbarnes72]

I can reduce line speed but voltage is all the way down. I'll give that a try first and then monkey with the gas

 

[70_Steve]

Don't try to fill in all at one shot. Use a series of small tack welds, and let each weld cool (not red)before the next.

Can you back up the pin holes with a piece of copper?

 

[jim3326]

Use a copper backing bar and as low a setting that will maintain a steady arc for the wire. Also if the metal is still rusty, the arc causes the rust to vaporize any good metal, it's an oxidizer.

Jim W.

 

[Crawdad]

X2 on the copper or aluminum backing. Harbor freight sells a good copper spatula for like $7. Get a couple bc they tend to get hot.

 

[red hot71]

I was going to say the same thing I have a brass hammer that I back up areas I want to fix, if you can get something to back it up.

 

[xcntrk]

Don't hit it straight on and heat is what blows through. Lay your mig tip at an heavy angle (45 degree) and just do tiny spot welds until the pinhole is filled.

Abrasive flapper wheels are good to sand small welds like that smooth without grinding them away...

 

[AZ73]

Don't hit it straight on and heat is what blows through. Lay your mig tip at an heavy angle (45 degree) and just do tiny spot welds until the pinhole is filled.

Abrasive flapper wheels are good to sand small welds like that smooth without grinding them away...

x2, and just tap.

 

[nrramse]

Don't try to fill in all at one shot. Use a series of small tack welds, and let each weld cool (not red)before the next.

Can you back up the pin holes with a piece of copper?

I have welded small holes this way, but using aluminum instead of copper. After a little grinding, it looks great.

 

[sp71eb]

Not sure how many pinholes you have but for longevity I have found it is better to just cut the spots out until you get to some good metal and weld in a patch. I was going to weld up some pinholes on my grill and found that by the time you get the out of the thin spots and finally get the hole filled you have welded more than if you had done a patch. Its still up to you though. If you only have a few spots to do then fill away. I usually run C25 at 18psi for your gas question.

 

[asinor]

You can also try a smaller wire diameter.

 

[rastiss]

All good suggestions...

Does it do it right off or after welding a while? What is the duty cycle of your welder? Most DIY guys overlook duty cycle. If its an economy cheap welder they have a low duty cycle and when you go beyond it, the welds start having issues...

 

[Dbarnes72]

Not sure how many pinholes you have but for longevity I have found it is better to just cut the spots out until you get to some good metal and weld in a patch. I was going to weld up some pinholes on my grill and found that by the time you get the out of the thin spots and finally get the hole filled you have welded more than if you had done a patch. Its still up to you though. If you only have a few spots to do then fill away. I usually run C25 at 18psi for your gas question.

It's a lower door post so the shape is a killer for cutout. I toyed with the idea of splicing in part of a new one but opted for the zero cost option. I do have a small brass strip and will use that in combination with all of the advice above. Put a new passenger side floor pan in tonight just with screws so I can still pull it back out and get to the back side of the post. I think an overlay of some of that metal filler after welding and it'll be good to go. Thanks all.

 

[Mike.thespike]

just draw a longer arc instead of being close hold the gun back run about 1inch wire stick out from the tip a couple quick spots to regain thickness and build off that works good done it lots when I run into thin spots

 

[jon_eds]

i have used this trick on several pin holes and other holes up to 5/8 in. take a screw (drywall type, no zinc or galvanized) for the pinholes, screw them in and spot weld around it, them cut it off with a cutting wheel and grind smoth. on larger holes i used a 90 degree magnet to hold the bolt up right in the hole, as close as flush to the bottom (to minimize grinding on underside) spot weld around it and cut it off flush. cleaning off rust is a must before welding and a little gap around the bolt is nice, gives weld somewhere to flow. i've had good luck doing this. and if u direct the weld at the bolt just above hole u can turn up the welder a bit to help weld burn into bolt. i've done this and dressed them up and taken a body hammer to them to make sure its good and solid weld. just a something different to try.

 

[AZ69EB]

You can also go to a smaller MIG wire diameter. As most people use 0.030" to 0.035" for everything.

See if you can go down to 0.023". You will also need to change your tip to match wire diameter. You shouldn't need to change the liner.

Good luck.