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Welding Chromoly


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Is anything special needed to weld Chromoly? Will a regular mig welder with a bottle weld it? Is a special wire needed or what? How is welding Chromoly compared to regular seam welded steel? I want to screw around with some just to see what it's like.


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I was talking to my welding teacher about that a couple of weeks back. You can use a mig machine, but you need a certain wire. I foget what number it is, but somebody on this site has gotta know. I haven't tried it yet we dont have any at school and it is quite expensive. Im curios too is it any different than welding mild?



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If your not going to heat treat it I have read that your better off using regular mild steel wire. According to a Lincoln book, the carbon in the chrome-molly mixes into the molten puddle which strengthens the weld. Hope that helps.


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Yeah, if that's true then you've helped me tremendously!! Anyone care to comment on V8Ranger's statement?

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I got this off of lincoln's website. www.lincolnwelding.com</A> They have quite a few informative articles so you might want to check it out. Anyways this is in regards to welding 4130 with a tig. Hope this helps. They specifically address the question of why not to weld with 4130 rod unless your going to heat treat.

TIG WELD 4130!
The Lincoln Electric Company, Welding Services. June 2000

Yes, you can TIG weld 4130 tubing up to .120" wall thickness easily with the techniques and
procedures described in this bulletin. Answered are the top ten most frequently asked questions
about TIG welding 4130 Chrome-Moly. These attached procedures apply to typical sporting
applications such as experimental airplanes, racing car frames, roll cages, go-carts, bicycles, and
motorcycle frames. The suitability of these techniques and procedures must be evaluated for your
specific application.

Q. Can I weld 4130 using the TIG process?
A. Yes, 4130 Chrome-Moly has been TIG welded in the aerospace and aircraft industries for years.
As with all welding, proper procedures and techniques must be followed.

Q. Do I need to pre-heat?
A. Thin wall tubing (< 0.120" wall) applications do not typically require the normal 300ºF to 400ºF
pre-heat to obtain acceptable results. However, tubing should be at room temperature (70ºF) or
above before welding.

Q. What filler material do I use?
A. Although there are several good filler
materials, ER80S-D2, is one you should
consider. This filler material is capable of
producing welds that approximate the strength of
4130. ER-70S-2 is an acceptable alternative to
ER80S-D2, as is ER70S-6, although the weld
strength will be slightly lower.

Q. When I use ER70S-2 filler material, do I
give up strength for elongation?
A. Yes. The filler material, when diluted with the
parent material, will typically undermatch the
4130. However, with the proper joint design (such as cluster or gusset, for example), the
cross-sectional area and linear inches of weld can compensate for the reduced weld deposit

Q. Why is 4130 filler metal not recommended?
A. 4130 filler typically is used for applications where the weld will be heat treated. Due to its higher
hardness and reduced elongation, it is not recommended for sporting applications such as
experimental airplanes, race car frames, roll cages, etc.

Q. Can I weld 4130 using any other filler metals?
A. Some fabricators prefer to use austenitic stainless steel fillers to weld 4130 tubing. This is
acceptable provided 310 or 312 stainless steel fillers are used. Other stainless steel fillers can
cause cracking. Stainless filler material is typically more expensive.

Q. Do I need to heat treat (stress relieve) 4130 after welding?
A. Thin wall tubing normally does not require stress relief. For parts thicker than .120",
stress-relieving is recommended and 1,100ºF is the optimum temperature for tubing applications.
An Oxy/Acetylene torch with neutral flame can be used. It should be oscillated to avoid hot spots.

Q. Do I have to pre-clean 4130 material?
A. Remove surface scale and oils with mild
abrasives and acetone. Wipe to remove all oils
and lubricants. All burrs should be removed
with a hand scraper or de-burring tool. Better
welding results with clean materials.

Q. Do I need to back-purge 4130 material?
A. Backpurging is not normally necessary,
although some fabricators do. It will not hurt
the weld and may improve the root pass of
some welds.

Q. Should I quench the metal after I finish welding?
A. ABSOLUTELY NOT! Rapid quenching of the metal will create problems such as cracking
and lamellar tearing. Always allow the weld to slow cool.

More Information on TIG Welding Chrome-Moly 4130

Find out more about Lincoln Electric's professional line of TIG welders here
Or, check out Lincoln cut length TIG welding filler metals here

WELDING SPECIFICATION: Aircraft and Motorsports


Remove all oxides and burrs within 3" of weld area.
Acetone wipe to remove all cutting oils.
Assemble and tack weld in joint in a minimum of four (4) places with TIG.
Tubing should be at minimum temperature of 70ºF (room temperature.
TIG weld per parameters specified using Lincoln Square Wave TIG 175, 275 or 355.


Condition (N)
.035" Wall Thickness
ER80S-D2 .035" Diameter
90º Tube to Tube.
Abrasive Clean/Acetone Wipe
20 - 40 amps
9-12 Volts
D.C.E.N. ( DC Electrode Negative )
Gas Lens 7/16" Orifice
2% Thoriated
1/16" Diameter
15-25 C.F.H.
5-10 C.F.H.
4-Places (min.)


Option #1
Option #2
Option #3

FOOTNOTE: Welding properties change from operator to operator. Techniques such as travel
speed, filler type, filler deposition rates, amperage, gas shielding, and arc voltage (distance
between tungsten and weld puddle) all have an effect towards heat input, weld strength, and


Well-Known Member
A little background. 4130 was originally formulated for gas (Oxyfuel) welding during the early part of WWII. It was designed to build tubular structures like aircraft parts out of. The nature of a gas weld normalizes the HAZ because of it's non concentrated heat application.
Carroll Smith's filler rod recommendation for welding 4130 is Linde Ox-Weld 32 or an equivalent.
With thin sections the filler metal will pick up enough of the alloying elements from the base metal to assume a near equal strength. I normalize regardless of section thickness.


"Teach you all I know and you're still stupid"
-- Howdy Lee


Well-Known Member
Its getting a little off the original question. I dont think Khris has a tig(right?), most of us own a mig. It would be nice to have both plus a plasma! Maybe in a couple years. So we know that you can tig chromoly and it was originally gas welded. But lets say you want to mig it and you usually use a 75 argon/ 25 carbon dioxide mix with er70s-6 wire. Do you need to change the shielding gas? I think you can use the same ,but may be wrong. What wire is needed? I am pretty sure that you need a different wire. I looked in the owners manual and it was no help. I also looked in my textbook for school, but did not see much about chromoly. I will ask my teacher this weekend and write it down this time, but any welding supply employee should know. Anybody that has migged chromoly is it different from mild steel? Does the puddle run faster/slower?



Well-Known Member
Khris-No you don't need any special wire for 4130 mig welding. They do make 4130 wire but it is very expensive. I use reg mild steel wire on my chassis. You will get best results from .035 wire but .030 will also work. A gas mixture of 75% argon 25% CO2 will get the best results. Straight C02 works but you get lots of spatter. Also make sure whatever your welding is clean and free of oil. Hope this helps.


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Yeah, my wants are pretty simple. The whole reason I ask is cause I'm interested in buying Donahoe's radius arms that mount to a Chromoly cross member that replaces your stock one. The catch is the cross member is for a Ranger and probably won't bolt to my Explorer so I'm looking to maybe take his and modify it to work or hack his up and use the tabs then make the rest.

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You might want to talk to the guys over over at Cameron welding in Stanton , they know their stuff there . I asked then the same question a while back and they sold me a roll of wire that worked awesome on chromo . I don't know their number , but I'm sure one of you guys got it out there , it a popular place .


Well-Known Member
I gonna pick up a book at a welding supply place its free and esob make it it gives a description of all their wire and tells the tensile strength and the application its used for. Low carbon wire can be used on chromoly, but you need to check the tensile strength it should be around 84,000. Also some 70 wire have a 85,000 tensile when tested so you dont need a wire thats rated 84+. They also make a wire that is for mild steel and chromoly and fabricating. check the book out its a good reference.