We are using gas tungsten arc welding to join 320 stainless steel, 0.070 in. thick sheetmetal with 316L filler material. The weld looks grainy, sort of like a casting surface. We are using a tungsten that has a white color code and have not been able to identify and do not know if this could be causing our problem. What are your suggestions for making our gas tungsten arc welds look better?
I expect that the white color code on the tungsten means that it is classified according to the international standard ISO 6848 or the Japanese standard Z3233, and therefore contains nominally 0.8 percent zirconium dioxide. This classification does not exist in AWS A5.12 at the present time, although it is likely to be included in the next revision. The only zirconium dioxide classification in AWS A5.12 is nominally 0.3 percent zirconium dioxide, brown color code. But I doubt that this has anything to do with your weld appearance problem.

If you want to improve color of your weld, you might want to try using argon shielding with an addition of hydrogen 1 percent or 2 percent. Your gas supplier should have this gas. It should brighten the weld surface.

A concern that may have nothing to do with the appearance of your weld is the use of the 316L filler metal which is not a filler metal that would typically be used in this application. There is a large mismatch in terms of corrosion resistance between 320 and 316L. A 320 is normally intended for use in sulfuric acid, and 316L will not survive long in sulfuric acid.

I would like to know if cutting a knife blank out of leaf spring made of 5160 steel with a plasma cutter will affect the hardness of the steel. After cutting I will be grinding the edges to finish the blade as well as heat treating it.
Yes, plasma cutting a knife blade out of piece 5160 steel will affect the hardness of the steel for about 1/8 in. back from the plasma cut edge. This area will be in the 60 to 65 Rockwell C range in this area and will be difficult to grind into shape. You may want to consider putting the cut pieces into a furnace and tempering them to reduce the hardness prior to grinding.

Please advise the best welding alloy to join 5056 aluminum to itself and 5052 to itself? We are a small shop and would like to have one filler metal for both applications.
When you are welding 5056 aluminum, the best filler would be 5356. The 5052 aluminum can be welded using either 5356 or 4043 filler. The simplest solution would be use 5356 for both applications.

One of my customers is welding 6061-T6 aluminum with 4043 filler metal. They are interested in improving the electrical conductivity of their product. What can we gain in electrical conductivity by a change in filler metal, and how much change might we gain with one alloy versus another?
There are 2 commonly available filler alloys for welding 6061-T6: 4043 and 5356. The 4043 has an electrical conductivity of 42 IACS while 5356 has an electrical conductivity of only 29 IACS which means the 4043 is more conductive. To put it in context, 6061 has an electrical conductivity of 43, so you cannot improve the conductivity to something higher than that anyway.

I am joining a 303 stainless steel cone tip to a 304 stainless steel cone which is about 18 in. diameter at the joint. The 304 stainless steel part is 16 gage sheet rolled into the cone shape. The 303 stainless steel tip is machined form solid stock. After tack welding in two spots on opposite sides, then welding is started 90 degrees to the tacks using E308L filler. Immediately the weld begins to crack through the center of the weld even though the tacks did not. Do you have any ideas?
Unfortunately 303 stainless will almost always centerline crack on welding. It is made to be free machining grade of stainless containing sulfur and is not weldable. Your only real solution is to change to another grade of stainless.

This column is sponsored by Penton and the Lincoln Electric Co., Cleveland. Dave Barton is a senior welding engineer in the Application Engineering Group of The Lincoln Electric Co. He oversees welding procedure development for both new technology and existing products, performs failure analyses for customers, and serves as a consultant on welding application problems. Barton has been with Lincoln Electric for 21 years. Send your questions for Mr. Barton in care of WDF by e-mail to: askdav@penton.com