Heat treatment of 4130 chrome moly

[Nunzio1]

I'm building a prototype off road motorcycle and have tig welded a 4130 chrome moly tubular frame. I've think I remember reading that the welds should be brought up to 400 degrees and cooled slowly to eliminate any stresses and cracks. Being that I'm planning on having the frame powder coated, which would involve baking it at 300 or 400 degrees to cure the powder coat - would this also stress relieve the welds at the same time?

[BillC]

Thermal stress relief is around 1100°F. Post weld heat treatment at 400°F will not do anything for you.

Regards,

[dyn88]

thermal stress relief is 1 hour per 1 inch of thickness at 600 degrees for 4130. normalization of 4130 happens at around 1650 degrees. tempering of hardened 4130 begins at 1050 and the closer you go toward 1650 the softer it will get. powder coat will not effect your frame at all. If you used thin walled tube and good welding practice then dont worry about it, it will be fine. if you are still concerned call the local steel mill and ask who nearby has a furnace that size, they are not that uncommon we have two one you could slide that frame in and one you could drive a whole motorcycle into.

[dyn88]

just saw where you are, call up sal steel and get a quote they can do it.

[BillC]

thermal stress relief is 1 hour per 1 inch of thickness at 600 degrees for 4130.<<SNIP>>dyn88,

What is your reference for 600°F? 1100°F is from AWS D1.1 section 5.8

Thanks,

[dyn88]

that is the temperature requirement that pratt and whitney and sikorski place on their tools, that get outsourced. Im sure that either source is adaquet though. Not sure why the huge descrepency in temps though.

[BillC]

Here is a link to a top 10 FAQ on the subject of welding 4130 tube frames:

http://www.lincolnelectric.com/knowledge/articles/content/chrome-moly.asp

Regards,

[Nunzio1]

Thanks for the help guys - It looks like I will not have a problem, but wanted to be on the safe side - nothing like creating a prototype motorcycle to show off your welding skills and have your welds crack....I tigged it using my 2004 Miller Syncowave 250 and ER80S-D2. After cleaning, deburring, degreasing I preheated the joints a little with a propane torch prior to welding - the metal seemed to be happier (welded easier) with the pre-heat. I went a little overboard on the triangular support design, but I want it to be bulletproof. It has 25 inch diameter by 12 inch wide low pressure full knobby tires, twin hydraulic disk brakes in the front, one on the rear, 16 hp Briggs V-Twin motor with electric start, Comet torque converter with jack shaft and right side drive thru a #60 roller chain. Overall length is 8 feet, with a standard motorcycle steering rake angle - basically an adult size "mini-bike". Will post some progress photo's soon...

Miller 250 Syncrowave
Miller 251 Mig w/SpoolGun
Miller 135 Mig
Miller 375 Plazma
Smith Oxy/Act
Ingersoll Rand T30 Compressor
48" x 48" x 3/4' thk steel table blanchard ground flat to .010
all in a 20 foot box truck as a shed...!!
All in a 20 foot box as a shed