I will be welding aluminum 5052 to 6061-T6 and 6061-T6 to 6061-T6, using 5356 and 4043 filler metals. I am a designer and am concerned with the mechanical properties of the finished weld. Can you give me guidance for estimating the mechanical properties of the final welded connections?

The mechanical properties of a weld between 6061-T6 and 5052, or of a weld that joins 6061-T6 materials, will be determined by the strength of the heat-affected zone in the 6061-T6. Generally, the strength in the heat-affected zone will be reduced to “O” temper strength with 5000 series alloys. With the heat treatable alloys there is not a good general rule, but you can expect a 30 to 40 percent drop in strength. In both scenarios you have listed, the tensile strength will be 24-36 ksi regardless of whether 4043 or 5356 filler is used.

I need to make repairs to an injection mold made of 7075 T7351 aluminum. The problem is that this an injection mold application, and the mold will need to be textured after machining. What filler metal can I use to do the repair and how will it respond to the texturing versus the original, parent material?

In any structural application, 7075 aluminum is considered to be unweldable. However, it often is used to make injection molding blocks and is frequently welded for such a non-structural application as mold build up. The filler usually used is 4043, but if the mold is to be textured as is the case in your application, 5356 will match the 7075 hardness better and would be recommended. In NO case should you weld 7075 for a structural application. For instance, do not weld lifting lugs to a 7075 mold block.

I am working on a project that requires welding of pure nickel to a 300 series stainless steel. What is the best electrode to use if using SMAW and GMAW?

The best filler alloy to weld nickel to 300 series stainless, regardless of process, is a NiCrMo-3.

We have welded Astralloy eb-450 to itself with an E309lt0-1 flux cored wire. When we ground off the reinforcement, we noticed a large contrast in weld metal versus the base metal. The weld metal looks as if it was bead polished. Why do we see this contrast between the parent metal and the weld?

The composition of the EB-450 is nominally 1.75% Cr, 1% Mn, 0.7% Ni and 0.3% Mo. The Er309L is 20% Cr, 13% Ni. The dramatically different chemistries are the reason for the color difference. We normally wouldn't recommend this filler metal for this application — a better choice would be 80S-B2L filler metal.

I need to find the best wire to weld cracks in 319 cast aluminum. We are welding car bumpers that are 6 mm to 10mm thick, and are subjected to 120 degrees to 140 degrees C. (248 degrees to 284 degrees F.) for 35 min. to 40 min.

The correct filler wire to weld your 319 cast aluminum parts is 4043, with 4047 as an acceptable alternate.

A customer of mine brought me a 15-5 ph stainless part to be welded. The part is in the annealed state before welding and then needs to be solution heat treated. I have been using an E308L filler metal without any troubles after heat treat. My question is this: If the 300 series stainless filler metals are not heat treatable, would a better choice for the filler metal be a 630 filler metal?

The answer to your question is dependent on the final strength requirements of the weld. If you want high strength in the weld metal, you should use ER630 (17-4PH) or 15-5 filler metal. An ER308L or ER308LSi filler metal is fine if lower strength is sufficient.