Tig welding info and ?????

By Big Al Date 11-05-2002 01:42

Hello,I'm new to tig welding,well basically I can do a little stick and a little mig welding,and thats about it.I bought a Lincoln 175 pro about a month ago and have been trying to learn to use it.The reason I bought it is that my son BMX races and we have decided to try our hand at building bike frames.The tubing we will be usig to start will be a chrome moly,the thickness will vary from .022-.049-.125for differant areas of the frame.My questions are what should I set the welder on to weld this,what shape and size tungsen to use,how do Imake the welds look good,what distance should the tungsen be out of cup,and from the weld material,do I melt a puddle on the material or how do I go about this with butt joints?......I theses are a lot of dumb questions but I want to learn alittle now as it will be early next year before I can take any training courses......Thanks in advance......Al

By Goose

Date 11-05-2002 02:44

The general rule of thumb is 1 amp of welding amperage per each .001' of material thickness. This would be approx. 120 amps for a piece of steel .120" thick. Different joint configurations will require you to tweak this setting which can be done on the machine or the foot pedal.

I would highly suggest building a few frames out of mild steel to get practice before doing chromoly. The reason is that you want to have a minimum of heat input to keep from having a cracking problem on the chromoly tube in the heat affected zone (HAZ for short).

For chromoly, I would suggest a 1/16" diameter ER70S-2 filler wire. Use either the 3/32" or a 1/16" 2% thoriated tungsten sharpened to a point. Keep your arc length (distance from the tungsten tip to the molten puddle) as short as possible without letting the tip touch the molten puddle. I usually set the tungsten tip about 1/4" past the edge of the gas nozzle...again, this can be adjusted for different joint configurations.

With TIG, try to keep your part fit-ups as tight as possible (I strive for 1/16' or less).

I have the same exact machine as you and find it's great for projects like yours. I use mine mainly for my drag car fabrication in my small home shop.

The most important thing is to practice, practice, practice...I need a bunch more myself:)

Have fun
Todd G
http://www.malibumotorsports.cjb.net

By Big Al Date 11-05-2002 04:23

I have been told to use a fillet weld.Can someone explain this to me in detail?I've been practicing with about everything I can get my hands on...Thanks...Al

By Don Hansen Date 12-01-2002 18:50

I've seen several references to TIG welding 4130 aircraft tubing with either ER70S-2 or ER70S-6. What are the differences in these two filler rods and is one preferable over the other?

By chall

Date 12-03-2002 12:20

Al, with respect to Goose and Don, I disagree with the filler metal selection.

Without more detail on the grade of chrome-moly, it is tough to be absolute. However, I would recommend using a filler with some chrome content (ER80S-B2) or some moly content (ER80S-D2). You will also need to preheat the base metal to at least 250F before welding.

For the application you described, you may be able to use ER70S-2. From a metallurgical standpoint there are better choices. No offense intended to Mssrs. Goose and Don.

Charles Hall