A hot job came in the shop the other day...
and it involved tig welding some pretty thick chunks of 4130 chromoly.
my machinist friend and job shop owner needed a thick piece of 4130 chromoly steel welded in order to meet a customers deadline.
So I thought I would bring you along with me.
It was a simple job, but there are still a few things to talk about...
A quick talk with my friend and I learned that this part would be black oxide coated after welding and stress relief. (I made a video a while back showing the black oxide process)
That meant that I needed to weld it with a rod that would respond to black oxide coating.
I might have chosen an ER309 filler for this job but ER309 filler metal contains too much chromium and will not blacken the same as the 4130 base metal.
I also learned what the part does in service. and that it will be load tested to 900 lb.
900 lb is not that much for 2 - .250" leg fillet welds much so that was not really a concern as far as matching filler metal to match the strength of the base metal.
And, the part was only going to have a furnace stress relief type heat treatment ...not a strengthening heat treatment....so using 4130 filler material was not a requirement.
So I chose er70s-2. and a 400f preheat
er70s-2 wire will blacken, and will provide a ductile weld that is unlikely to crack.
I used 2 passes on each side to meet the .250" fillet weld requirement on the drawing....and I kept the heat above 400f during the whole welding operation.
Then I reheated the entire part and let cool slowly to room temperature before delivering the part.
Base Material Type/Thickness. 4130 chromoly / 1-1/4" thick
Prep Method - machined surface, acetone wipe only
Filler Metal Type/Size - ER70S-2 3/32". (32mm)
Tungsten size and prep 3/32" (2.4mm) 2% lanthanated blunt taper 60 degree
Gas Type and Flow Rate - argon 25cfh
Cup size #12 clear furick cup
Current/Polarity 160-170 amps DCEN
Length of Arc. - 3/32" (2.4mm) or less
Angle of Travel 15-20 degree
Manipulation/Technique - move, pause, dip for first pass, lay wire wave second pass
Speed of Travel -6-7 inches per minute
preheat - 400F min
A few years ago, I welded a part for this same job shop owner made out of 4140 steel.
4140 is very similar to 4130 except that has a bit more carbon content and therefore sometimes requires a higher preheat.
In this video, I used a 500f preheat. First, I warmed the part up on a propane cooker, and then I used a rosebud torch to reach over 500f.
These parts were a tight fit so I heated the part with the hole first, then inserted the round part and heated it all to around 550f so that I could be sure it was at least 500f before welding.
I kept the temp up to 500f until welding was done, then reheated and let cool slowly.
I chose er70 filler rod for these parts also for the same reasons as the 4130 part...black oxide coating, and because the strength was taken care of with smart design.