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
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.
.
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
GENERAL INFORMATION
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.
EXAMPLE WELD SCHEDULE INFORMATION
PARENT MATERIAL:
4130
MATERIAL CONDITION:
Condition (N)
MATERIAL THICKNESS:
.035" Wall Thickness
FILLER MATERIAL:
ER80S-D2 .035" Diameter
JOINT TYPE:
90º Tube to Tube.
JOINT PREP:
Abrasive Clean/Acetone Wipe
JOINT GAP:
.000-.010
CURRENT TYPE:
D.C.E.N.
AMPERAGE:
20 - 40 amps
VOLTAGE:
9-12 Volts
TORCH TYPE:
D.C.E.N. ( DC Electrode Negative )
CUP SIZE:
Gas Lens 7/16" Orifice
CUP TYPE:
Ceramic
TUNGSTEN TYPE:
2% Thoriated
TUNGSTEN SIZE:
1/16" Diameter
TUNGSTEN SHAPE:
Pointed
TORCH GAS:
Argon
FLOW RATE:
15-25 C.F.H.
BACK-UP GAS:
Argon
FLOW RATE:
5-10 C.F.H.
TACKING SEQUENCE:
4-Places (min.)
FILLER MATERIAL OPTIONS:
Option #1
ER80S-D2
Option #2
ER70S-2
Option #3
ER70S-6
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
elongation.
