What about Welding Stainless to Carbon Steel?
Last weeks video on welding nickel alloys mentioned that one of the main uses for nickel alloys is for welding rods or filler metal.
Tons and Tons of inconel 625 filler metal are used every year as filler metal to clad boiler tubes and pipe that is made from steel. The cladding extends the life of the boiler tubes because inconel 625 is very heat and corrosion resistant and can withstand numerous heating and cooling cycles.
Another nickel filler metal is Hastelloy W.
Hastelloy W is a nickel alloy tig welding filler metal that works on all kinds of dissimilar metal combinations. The AWS identifier for it is ERNiMo-3 and its also called alloy W.
The nominal chemical composition of hastelloy W is 5% chromium, 24.5% Molybdenum, and 5.5 Iron and about 63% nickel with some other trace elements thrown in.
With the high nickel and molybdenum content it is very forgiving when used on crack sensitive or hardenable steels.
Hastelloy W is widely used in the aviation and aerospace industries for weld repairs on different combinations of heat and corrosion resistant alloys like 17-4ph stainless, 321 and 347 stainless , A286, and many other alloys.
Hastelloy W is also even sometimes used for welding low alloy steel weld repairs.
Its got a pretty good track record.
The problem is its really expensive stuff. I have seen it as high as 147 dollars per pound. (that was the arc-zone.com price on the day I wrote this)
I just happen to have quite a bit of hast W tig rod that I bought about 20 years ago from a scrap yard.
If it weren’t for that, I would have used 312 or 309 stainless rod for this job. 312 and 309 are both good rods for welding stainless to carbon and only cost about 10-20 bucks per pound.
In today's video I am using Hastelloy W tig rod for a thread repair where a threaded stainless steel sleeve is pressed onto a carbon steel spindle and welded.
309 is usually the filler metal chosen for welding stainless to carbon steel when the composition of both are known. Nickel alloys are sometimes used for welding stainless to carbon because nickel alloys wont become hard and brittle no matter the carbon content of the steel. The base metal can become hard but the weld metal wont.
I don’t know how the threads got mucked up or exactly what piece of equipment the spindle came from...or even exactly what it was made of.
I suspect the spindle was made from something akin to AISI 1045 steel.
The options for this weld repair were to either machine off the damaged threads and build the threaded area back up with weld metal and re cut the threads ...or
Cut the threads on a separate piece , make sure the threads were right, then press the piece on and weld it. Not knowing how hard the threads would be after welding, or how all that welding would affect the temper of the spindle, the machinist chose the second option. His call. I was just the dumb welder that day.
With a nice chamfer on the end, the the threaded sleeve was pressed onto the spindle and welded on both sides.
Then the keyway slot was re cut and de burred and thats about it...and the part was done.
I chose to use pulse current for this weld job because I didnt want to melt the lip of the threads.
Here are the parameters:
I set the overall amps to 140 because the overall output is less when you pulse.
I used a foot pedal to control the puddle.
30 pps pulses per second
50% pulse on time also called pulse width
50% background current.
I probably could have messed around and found some more optimum settings but it just wasn't necessary. 30 pps is high enough not to be annoying and prevented excessive heat build up and wandering of the puddle.
I was able to control the puddle pretty well.
So thats it for today. Not sure if it was the best repair job ever done but its still holding.