Hi Artisan, know what ya mean it would be nice for a single source for all this stuff. Unfortunately until someone takes the time it's mostly by experience and reading bits here and there. There are some books that by and by give up the info but usually not in a fast user friendly way.
In very general terms, alloys usually match rods, ie 308 stainless - 308 rod, 316, etc. Not always a MUST do, unless your are doing cert welds the have a specific written process that must be followed specifiying all things, ..... tungnsten, rod, gaps, bevels etc. You can weld mild steel with stainless rod if you wish. The take home point is that you will usually end up with dissimilar tensile strengths between the base metal and the weld. Usually no biggy for the average joe, but you can end up with cracking issues sometimes.
4130 Chromoly in general everyday welding, ironically is often better to use mild steel rod, but NO COPPER COATING on the rod, which is what most weld supply stores sell. The copper coating will NOT fuse with the base metal and be prone to fissuring and cracks. The problem with using 4130 rod of known quality, is that unless you are very experienced with welding chromoly, which is heat sensitive, you end up with the weld having a higher tensile strength than the boundry zone of the weld, or heat affected zone. This is where the part will fail because it was weakened by the welding process and instead of the whole zone flexing, supporting as one, absorbing whatever stress is placed upon it. The heat affected zone will end up being brittle and crack prone, UNLESS the whole part is heat treated, or normalized. (confused yet
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For mild steel, again most suppliers sell copper coated rod, which does offer some cleaning benifits while welding, and in most garden variety repairs or fabrication will do just fine. But remember copper cannot fuse with steel. Most of it will burn away but some will fill micro porosity in the steel grain and be no bueno.
Incolnel rod types for nickle based alloys, and for welding some dissimilar ferrous alloys together.
And obviously titanium is only gonna work with titanium rod. Lots o different ones in that group too.
Welding copper and brass? use silicon bronze brazing rod. It will weld on DCEN kind of like a blend of TIG welding and brazing, if that makes any sense. Kinda weird but cool. You can still make a bead, but if ya over do the heat it tends to spread out more like a brazed joint!
Cast iron not so good with TIG, small intense area of heat that tig produces causes a sharp boundry between hot iron and cold iron, and because of the slower speed involved causes you to start chasing new cracks! Braze it, Silver solder, Stick or mig, here. Triccky tho, every cast is not alike and may not react as youd like.
Just some basic stuff but will cover most any situation, hope it helps my friend. If not, in the round file it goes,
- Lou
, that helps out alot. I understand a lot more now, maybe everyone should keep adding to this, like lou said there's not a big list out there thats easily found and user friendly. Maybe this site could provide it for us 