Metal Prep

[Allen]

How does everyone prep their metal before welding?

Say box tubing, plate, round tubing, etc?

What about actual welding to the vehicle or a trailer?

I'm curious as to what you guys are doing that you needn't be, or what you're not doing that you should be.

[Joe Dillard]

I usually clean up the rust, paint, etc and try to clean it to bare metal with a flap wheel, or a wire wheel. Sometimes I use a hand grinder with a grinding disc on the real nasty stuff. If it's not very dirty, sometimes I'll use a wire brush. I have used sand paper and green pads too. I try to clean it up ~1/2" or more past where the weld would be layed at.

I'm almost always too lazy to unhook the battery in the vehicle. I try to clean an area close to where I'm welding to attach the ground clamp then go to town.

Whenever I know I'm going to weld, I sit my solar helmet outside for a while to allow it to charge.

[Matt Pascoe]

New steel - I sometimes hit the weld area with a flap wheel. Especially bar stock, it seems to have coating that I grind off. Tube, nothing unless I put cutting fluid on it, if oily I spray it with "aero prep" degreaser.

Old steel - hit it with a flap wheel till shiny.

I do try to chamfer my edges for better penetration.

(btw, Aero Prep makes for allot of fun if it hasn’t thoroughly evaporated prior to striking an arc )

[Matt Pascoe]

Originally Posted by Joe Dillard

Whenever I know I'm going to weld, I sit my solar helmet outside for a while to allow it to charge.

I've wondered about that... Is there an actual charging circuit? The battery isnt rechargeabe, is it? My guess is the solar panel is just to supplement the battery while welding, dunno...

[mrblaine]

On new hot rolled, I clean the scale back.

On cold rolled, I wipe the oil off with a clean rag

On HRPO, I clean the oil off with a solvent

On tube etc, I clean off rust with a Paint removal wheel, or similar.

I'm very careful with anything that aggressively removes metal like a flap disc so I don't leave gouges and possible stress risers in or near the HAZ.

Anything that's painted or powdercoated I remove it with a mild abrasive wheel to just outside the HAZ to prevent contamination of the weld.

[Allen]

Is it safe to assume that everyone is using a 220v power source?

Joe, you overclean. Stop it. Weld spatter sticks 10x better to bare metal than to the as delivered surface.

Matt, why do you bevel? And when and where?

I have some pictures I'm gonna try to post up tonight/tomorrow and offer some better explanations.

It's been a crazy few days.....

[Allen]

Here's the photos I was talking about.

It is .125" steel, welded corner to corner via GTAW.

First look at the steel as welded. It was a machined edge, with absolutely no surface prep other than de-burred on a belt sander. Look closely and you can even see the pitting in the machined edge.



Filler was plain old ER70S-6 tig wire.

So lets look at fillers for a second.

ER70S-2 is usually a triple deoxidize containing aluminum, titanium, and zirconium. It's a "fast freeze" wire with a lazy puddle that makes it suitable for out of position welding.

ER70S-3 is a general purpose wire, and is suitable for use over light rust. There is usually a premium quality wire available in addition to the standard S-3, with the same AWS class and is also suitable for light rust.

ER70S-4 contains higher levels of deoxidizers and is suitable for many general purpose carbon steel MIG applications. It can be used over light rust or light mill scale.

ER70S-6 contains even higher levels of manganese and silicon than other grades of MIG wire. It provides a highly fluid puddle and excellent tolerance of rust and scale. It's not so good for out of position work. There are also "special" wires available within the AWS ER70S-6 class containing very high levels of manganese and silicone for even greater tolerance of rust and mill scale. These wires produce good wetting action, even on very dirty steel.

ER70S-7 is a newer grade, and features an optimized manganese to silicon ratio. It is suitable for welding over moderate amounts of rust and scale.

Now, look at the cleaning action from the heat, shielding gas, and filler wire additives.



Notice any impurities in the weld? Remember, TIG is very finicky, and usually works best on very clean metal. But the filler, and more specifically, the additives, play a crucial role in weld quality.

My results may not have been so good has I used, say, an ER70S-2 filler or S-3 filler.

Look at the rest of the photos.....I have another of these to make with the same dirty steel.....






Stop over cleaning. You're wasting time and consumables, and even possibly creating extra clean up post weld.

[Joe Dillard]

The overcleaning thing is probably a habit due to military service - I'm a civilian now so I guess it's time to revert to the real world.

Yep, my MM 175 MIG is a 220V welder. I plug it in where my electrical dryer plug use to be in my utility room. I simply swapped in the right recepticle and use a ~20' welders extension cord so it reaches my garage.

[Allen]

Originally Posted by Joe Dillard

The overcleaning thing is probably a habit due to military service - I'm a civilian now so I guess it's time to revert to the real world.

Yep, my MM 175 MIG is a 220V welder. I plug it in where my electrical dryer plug use to be in my utility room. I simply swapped in the right recepticle and use a ~20' welders extension cord so it reaches my garage.

I chuckled when you mentioned scotchbrite and sandpaper.

I'd find a new line of employment were I subjected to that torture.

[Allen]

A thin film or light coat of oil is fine too.

Leave it.

Now if it drips or runs, that's a different story.

[Matt Pascoe]

Originally Posted by Allen

Matt, why do you bevel? And when and where?

Why do I bevel? Primarily because I have a problem with producing thick, fat beads. A deep bevel gives me someplace to hide it. I have a hard time welding "hot" enough. As I turn up the heat I lose the sizzling bacon sound and get "pop, pop, pop" so I turn the heat back down and get a fat weld.

When and where? Almost everywhere except T and corner welds. Hole saw coped tubing bothers me because it leaves no groove for a weld. I almost allways bevel tube joints (chop saw coped tube is easier in this regard imo).

[mrblaine]

Originally Posted by Matt Pascoe

Why do I bevel? Primarily because I have a problem with producing thick, fat beads. A deep bevel gives me someplace to hide it. I have a hard time welding "hot" enough. As I turn up the heat I lose the sizzling bacon sound and get "pop, pop, pop" so I turn the heat back down and get a fat weld.

When and where? Almost everywhere except T and corner welds. Hole saw coped tubing bothers me because it leaves no groove for a weld. I almost allways bevel tube joints (chop saw coped tube is easier in this regard imo).

The reason you are getting the popping sound is because you are staying in the puddle too long. When the heat goes up, you need to move a bit faster.