Gas welding is for steel only.  The skill is somewhat like brazing.  In brazing you bring the metal to red hot, in gas welding you bring the steel to yellow hot or slightly above,  When the steel begins to melt apply the gas filler rod (RG 45).

RG 45 is a standard gas welding rod that you can find at your local welding supply. 

I prefer to work with clean metal, but steel for gas welding does not need to be as clean as for brazing.  In the brazing chapter and the chapter on steel I discuss the "mill scale" on hot rolled steel that needs to be ground off before brazing. 

For gas welding hot rolled steel this is not necessary. The steel at yellow or white hot burns off the mill scale.

Gas welding is stronger than brazing, although in my metal sculpture a tremendous amount of strength is not necessary.

If you are welding up a piece of shop equipment that will be under a lot of stress you will want to make sure that you get a good gas weld.

Today very few people gas weld.  The Mig welder is cleaner and more convenient.  But, if you only has an oxygen acetylene torch outfit you'll find gas welding has it place in your shop.

Personally, I like to gas weld.  I have a Mig welder but will often opt for gas welding because I like the process.

Gas welding takes a trifle more skill than brazing, but with a little practice you'll get the hang of it.

Video of gas welding 

Generally when I'm gas welding it is welding 1/8th" steel and above. 

Because of the broad flame of the oxygen acetylene flame, gas welding thin material such as sheet metal will most always result in warping the thin steel. 

Gas welding usually indicates the use of a gas filler rod.  But there is also Fusion welding.  What this means is when the steel begins to melt allow the melted edges of both pieces to melt together.

In the photo below the gas weld where my finger is pointing is where filler rod was applied. thus the build up of weld.

The weld on the left is a fusion weld.  Since there was no filler metal added there is no build up.

Fusions welding is not as strong as when using the gas filler rod.  I sometimes use fusion welding to "tack" two pieces together.

Tack welding or even tack brazing is a technique I use to lightly weld or braze two or more pieces together for alignment.  Once I'm satisfied that the pieces are properly aligned, I can go ahead and do a complete weld or braze.

This photo below shows a number of tack welds.  If I didn't tack weld this a number of times the heat from the torch when gas welding would have warped the metal.  The tack welds hold the two pieces in place.

The finished weld.

The video below is an example of using the filler rod and fusion welding.

Notice the sparks in this video.  These are tiny bits of molten metal.  Occasionally one of these bits of molten metal will lodge in your tip.  When this happens, turn off your torch and clean the tip out with a tips cleaner.

Gas Welding with Filler Rod & Fusion   

When fusion welding or using the gas filler rod the torch flame is moved in small circles.  The size of the circle is dependent on the thickness of the metal to be welded. 

Moving the torch in this way works the molten metals of both sides of steel together.

Moving the torch tip in small circles.    

Back to table of contents