Mig welder- bleed the gas or not

[flyerdan]

When switching tanks before putting the regulator on, point it in a safe direction and open the valve for a second to give a quick cleaning blast for any debris that might be in the valve pocket. Also, when the regulator / flowmeter isn't hooked to a tank, be careful not to ding the rounded end that goes in the valve, it's a precise machined fit and it doesn't take much to cause a slow leak.
I've ran feeders that have a wirefeed / purge function; basically it's a spring loaded center off toggle switch that will activate the gas solenoid by itself when pushed one way and the drive rollers by themselves the other way. That allows bleeding down the gas pressure without running wire, or making it hot. Also runs wire without gas when changing wire spools. Should be a simple retrofit for someone with a basic electrical knowledge.

 

[Willl]

It might be wrong but I've done nothing but just close the tank valve.

 

[Shield Arc]

It might be wrong but I've done nothing but just close the tank valve.

That's what I do.
I have all flow meters, no regulators other than oxygen & acetylene.

 

[bikerdib]

DAN H, opening the valve all the way is standard procedure for me because I've always done that on my O/A torch.

Welding with both hands and all positions is also pretty much SOP for me after all the years burning rods. Although, I've already seen that it will take some practice getting used to puddle control on vertical up. And I haven't even attempted overhead...

I know that clean metal is pretty much a MUST with gas shield welding. However, is it necessary to remove all the blue oxide scale from hot rolled steel if I use 70-6 wire? I understand that the cleaner the better but do I need shiny steel?

Shield Arc, thanks for the link to the welding calculator. I know that it will be a new learning experience getting the arc temp where I want it to be using solid wire. It took me years to learn rod size and amp settings and I'm still learning something new every time I strike an arc.

Flyer Dan, again due to more years than I care to think of using O/A torch, purging and cleaning is SOP. That toggle solenoid setup sounds like the cat's whiskers. I've been thinking about installing a brass tee in the supply hose with a small brass valve that I could slowly open to bleed but I'm not sure if that would relieve the pressure at the gun and hose or would that be necessary?

Thanks again guys. I appreciate any input you can give me to help speed my learning curve.

 

[CNC Dan]

I know that clean metal is pretty much a MUST with gas shield welding. However, is it necessary to remove all the blue oxide scale from hot rolled steel if I use 70-6 wire? I understand that the cleaner the better but do I need shiny steel?

some steel has a thicker oxide layer than others, so you will have to judge for yourself. I'm guessing you are going to be running lots of practice beads, so try some with and some without. I would say you can get away with some. More than you could get away with if using TIG.

You might want to try a roll of self shielded flux core wire. It's like mini stick welding with a rod that never burns down.

 

[Shield Arc]

I've already seen that it will take some practice getting used to puddle control on vertical up.

I've tried Jody's vertical up technique, it is quite easy to do. :thumbsup:

This vertical mig welding technique will penetrate...Thats what She said!

 

[Stimw]

It might be wrong but I've done nothing but just close the tank valve.

Me Too, I've had my Miller 210 for 12 years and I just shut off the tank valve.
I have a flow meter but I don't like it. It seems to use more gas. ???
It is possible to weld dirty metal, the trick is to hold back with the arc, let the puddle flow forward so it burns off contamination/paint. Clean is always best but some situations you can get by.
Been MIG welding for 42 years, Stick, O/A 50 years.

 

[bikerdib]

I've tried Jody's vertical up technique, it is quite easy to do. :thumbsup:

This vertical mig welding technique will penetrate...Thats what She said!

Thanks. That is pretty similar to what I do vertical uphill with 7018 stick and I tried it with the mig too. I think my main problem was too slow movement with the gun. I guess it's like they say; practice, practice and more practice.

 

[Shield Arc]

In my career I've run a significant amount more gas less flux core than Mig. Majority of that flux core wire was 5/64-inch. When running vertical up with 5/64-inch wire it is about the same as running vertical up with 5/32-inch 7018. I'm sure you will agree that is a lot of metal to push up hill. Lincoln has a technique for vertical up where you build a shelf at the bottom. You can either point the gun straight in, (90-degrees) or point it up just a little. Once the shelf is built, you pick the gun up and point it down just a touch. You lay the puddle on this shelf, once the desired puddle size is established you start traveling up hill continuing to hold that gun angle. But you have to be really careful if you are carrying a lot of iron that you work the back side of the puddle, or you will get lack of fusion at the heel of the weld! That is one thing I really like about the technique in that video, it really cuts in on the backside of the puddle. But still leaves a flat face to the weld. When running the root pass on a V-butt plate test the last thing you want is wagon tracks. Once the root, and hot pass are in generally you got it made, because you then have room to work, and you can carry a lot of iron by using Lincoln's technique.

 

[bikerdib]

Thanks Shield Arc, that brings up some good points to pay attention to. I may have to drag out the machine and grab some scrap pieces today. Unfortunately, yard work may get in the way. The grass is starting to grow here in Texas and it looks like time to use the John Deere.