Common 4130 TIG welding questions and answers

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 preheat ?
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 strength.

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.
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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.

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Skunk Works

Some of the things we work on here at Metalworks I can't tell you about. We have confidentiality agreements with several of out clients. I can show you some pictures but I cannot tell you what they are or the materials used. Enjoy!

TIG Welding

Gas Tungsten Arc Welding (GTAW) is more commonly known as Tungsten Inert Gas (TIG) welding. Although technically incorrect. Old timers still call in Heliarc due to Helium being used as the shielding gas. Helium is an inert gas and was originally used when TIG was developed during the 1940's. Helium is still used in specialty applications. Today Argon is the gas of choice, mainly due to cost.

TIG is the most versatile kind of welding there is. You can weld 4130 chromoly, mild steel, stainless steel, tool steel, copper, nickel alloys like inconel and hastelloy, aluminum, magnesium, and titanium. TIG welding, is an arc welding process that uses a nonconsumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by a shielding gas, and a filler metal is normally used. A constant-current welding power supply produces energy which is conducted across the arc through a column of highly ionized gas and metal vapors known as a plasma. AC current is used for welding Aluminum and Magnesium. DC current is is for most other metals.


The above is an example of a TIG weld on Aluminum. A TIG weld has a very neat appearance and if done correctly should end up shiny. The weld nearly looks as if it were a row of coins.

An example of a copper TIG weld.


This is a complex joint in steel and the result is why I use TIG welding extensively on projects that we do. TIG welding is like playing the guitar, anyone can pick it up and make it work but to be proficient at it you must practice, practice, practice! Got questions? Feel free. I'll be happy to help.