Your choice of filler rod is extremely important as the rod must correctly match the alloy of the material you will be welding.
Tig welding chromoly filler rod.
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The thickness of the material you will be welding also determines the required diameter of the filler rod.
As with all welding proper procedures and techniques must be followed.
For tubing over 0 120 a 300 400 fahrenheit degrees preheat is required.
First the use filler material that closely matches the base metal is not intirely true as there are many factors that dictate what filler material to choose.
Er70s 2 is also an acceptable alternative to er80s d2 as well as 70s 6 although weld strength will be slightly lower.
Stainless steel mild steel copper alloys aluminum alloys nickel alloys titanium alloys.
Yes 4130 chrome moly has been tig welded in the aerospace and aircraft industries for years.
A common filler metal choice for welding chrome moly is er80s d2 this filler metal is capable of producing welds that approximate the strength of the 4130.
Try to weld chromoly slower than normal especially if.
Faa ac43 13 1a section 5 4 74 9 states use welding rod and electrodes that are compatible with the materials to be welded.
Trying to weld 0 035 in.
As for filler rod diameter use a rod diameter that matches the thickness of the base metal.
Tubing with a 1 16th inch filler 0 063 in is a bad idea because the tubing wall will melt before the filler rod is up to temperature.
Tip if you have a roll of bare mig wire like e70s3 or e70s6 it will work great in a pinch just snip some off and straighten or better yet if its too small double it up and chuck it up in a cordless drill and twist it tight so you wont have to feed so much wire.
You don t need to preheat the metal for anything under 0 120 thickness but if you have the time it will not hurt to preheat at 100 fahrenheit degrees just to eliminate the moisture.