How do I deal with corrosion and contaminants?

admin

I am dealing with some very old guns at work, some of which have some very heavy pitting that I am trying to weld. I have tried both Tig and gas oxy/acetylene and I still end up with contaminant pitting in the finished weld. I have tried everything I can think of to remove the contaminants but I fear that the original quality of the steel is to blame. After machining the original steel, inclusions of what looks like welding slag is readily visible in the steel. It's not rust per se but a hard black crust. Is there any type of filler rod and/or welder setup that might help me get a pit free weld?Thanks for any suggestions.
Reply:Assuming this is strictly cosmetic, you can use use stainless steel filler in lieu of carbon with the TIG process.
Reply:Is the area to be welded critical as far as the integrity of the gun? If it is only cosmetic you could use silicon bronze filler to fill in the voids then face it off.Yup
Reply:Both interesting ideas, BUT, if the finish is to be cosmetic, neither bronze, nor stainless will accept bluing.I would use a strongly deoxidizing steel filler, but if you've got inclusions beneath your weld, they will most likely surface.Someone else here could tell you which is the best of rg45, rg60, or er70s2.
Reply:That's the problem.  Typical deoxidizing carbon steel fillers won't do diddly squat for porosity, particularly on poor base metal that has had years of oils and solvents in its path.  You can cheat with stainless filler, but as mentioned, it won't take the bluing.
Reply:Some more details and photographs of the problem might elicit some better suggestions, if methods exist. Are these being restored for collection purposes, or are they intended to be fired too?
Reply:The specific gun I am having the most trouble with is getting both a cosmetic and mechanical restoration and will be shot.  The affected areas are not critical to the function of the gun and thankfully it's a blackpwder cartridge gun so I'm not dealing with high pressures.  I will not be bluing the pitted parts, rather I will be color case hardening them.  I'm not sure how stainless will react to that process.I'll try to post some pics tomorrow.  Thanks for the responses.
Reply:I forgot to mention.  I tried welding the pits both before and after annealing the steel with the same results.  I had hoped that by annealing the parts at 1500 degrees for two hours (in a steel vessel filled with charcoal to prevent scaling) that I would in effect "cook" the oils and solvents out of the metal and improve my welding results.
Reply:Steels react to heat during 'color case hardening' by forming thin layers of oxides. Stainless steels do this much less easily and to a much less degree so won't serve your purpose. Those spots will appear mostly bright 'silvery'.If you have some similar old material to practice on, that would be better than experimenting on the guns for the following thoughts/ideas.The cooking may be 'coking' the oil, leaving carbon in the pores of what might already be a high-carbon surface over a lower carbon steel core. If the pitting is due to the corrosion, it may have iron oxide within the pits which, when heated by the torch, breaks down so that the oxygen can combine with the carbon to form CO which dissolves in the molten metal and then causes pockets as the melt cools.If this is correct, using the TIG torch, you might be able to keep the small molten pool a liquid for long enough to have all the oxygen recombine, then let the pool solidify very slow by very gradually reducing the amperage while the gases 'undissolve'. I would not expect this technique to work well. You might also try using some flux designed for cast iron welding (applied by dipping the heated end of some E70s-6 wire into the can.) That wire has higher amounts of deoxidizers so might help some.Lastly, if you rubbed some powdered Aluminum (the atomized type sold at paint stores) into the pores before welding, that might combine with any oxygen present and float to the surface as a slag, once the whole area is molten.None of these ideas are based on prior use, just on general knowledge. Someone else here may know better, so it might be worth waiting a bit to try them.
Reply:If its an old enough gun, its possible you are dealing with wrought iron, and not steel at all.Wrought iron has silica inclusions in it that make it a bear to tig weld. The traditional technique was forge welding- get it red hot, and hit it with a hammer.
Reply:i sometimes read these threads and am in aawe at the experience ad knowledge available here..
Reply:Originally Posted by MidwayGunsmithI am dealing with some very old guns at work, some of which have some very heavy pitting that I am trying to weld. I have tried both Tig and gas oxy/acetylene and I still end up with contaminant pitting in the finished weld. I have tried everything I can think of to remove the contaminants but I fear that the original quality of the steel is to blame. After machining the original steel, inclusions of what looks like welding slag is readily visible in the steel. It's not rust per se but a hard black crust. Is there any type of filler rod and/or welder setup that might help me get a pit free weld?Thanks for any suggestions.
Reply:Originally Posted by MidwayGunsmithThe specific gun I am having the most trouble with is getting both a cosmetic and mechanical restoration and will be shot.  The affected areas are not critical to the function of the gun and thankfully it's a blackpwder cartridge gun so I'm not dealing with high pressures.  I will not be bluing the pitted parts, rather I will be color case hardening them.  I'm not sure how stainless will react to that process.I'll try to post some pics tomorrow.  Thanks for the responses.
Reply:Thanks for all the advice.  I'll let you know how it comes out in the end.
Reply:Hmmm, color case-hardened and blackpowder?The part(s) in question would be the lock sideplates (if a long gun) or maybe the frame (if a pistol)?  Just guesses on my part.  Where are the pictures?  If the problem is contaminants, wash well with strong solvents.  Repeatedly.  Dry well (solvent + heat/arc = ).  Then TIG with an ER70S-6 filler.  Repeatedly, to try and 'float out' any crud.  If crud comes out, grind it out and repeat the weld until the weld comes out clean.The idea of 'baking' the item(s) at 1500F is sort of good, except that you might have introduced extra carbon into the steel by holding it in the carbon-rich furnace/crucible/whatever at elevated temperatures.  Pretty much case-hardening the outside of the steel at least.And as already mentioned (by several folks), the original metal in question may be the culprit itself.  Actual original "wrought iron" is pretty much IRON with various slag forged/wrought into the physical structure (not the molecular structure) and it is NOT "steel".  Arc or gas welding wrought iron would pretty much be 'difficult'.  The "hard black crust" welding slag 'crud' is in the part -after- welding and machining, or after cleaning/machining but before welding?  Is it in the 'original' steel, or the weld bead/filler, or the junction between the two?  Any way, you have to get the pitting cleaned out as much as you can back to clean sound steel before you weld and then you may still have to weld and float some contaminants out and grind that out and redo it several times until the combination of the welding heat and the arc and the filler metal chemistry all can combine to get the crud out of what you are trying to weld.  IIRC, someone hear was welding something (aluminum?  engine parts?) and it took them at least a half dozen times of clean-weld-crud-grind-clean-weld-crud-grind-etc before they could get the weld to actually be acceptable and free of crud.  The best laid schemes ... Gang oft agley ...
Reply:Originally Posted by MoonRiseHmmm, color case-hardened and blackpowder?The part(s) in question would be the lock sideplates (if a long gun) or maybe the frame (if a pistol)?  Just guesses on my part.  Where are the pictures?  If the problem is contaminants, wash well with strong solvents.  Repeatedly.  Dry well (solvent + heat/arc = ).  Then TIG with an ER70S-6 filler.  Repeatedly, to try and 'float out' any crud.  If crud comes out, grind it out and repeat the weld until the weld comes out clean.The idea of 'baking' the item(s) at 1500F is sort of good, except that you might have introduced extra carbon into the steel by holding it in the carbon-rich furnace/crucible/whatever at elevated temperatures.  Pretty much case-hardening the outside of the steel at least.And as already mentioned (by several folks), the original metal in question may be the culprit itself.  Actual original "wrought iron" is pretty much IRON with various slag forged/wrought into the physical structure (not the molecular structure) and it is NOT "steel".  Arc or gas welding wrought iron would pretty much be 'difficult'.  The "hard black crust" welding slag 'crud' is in the part -after- welding and machining, or after cleaning/machining but before welding?  Is it in the 'original' steel, or the weld bead/filler, or the junction between the two?  Any way, you have to get the pitting cleaned out as much as you can back to clean sound steel before you weld and then you may still have to weld and float some contaminants out and grind that out and redo it several times until the combination of the welding heat and the arc and the filler metal chemistry all can combine to get the crud out of what you are trying to weld.  IIRC, someone hear was welding something (aluminum?  engine parts?) and it took them at least a half dozen times of clean-weld-crud-grind-clean-weld-crud-grind-etc before they could get the weld to actually be acceptable and free of crud.