I have welded with tig a fixture and when cleaning up the part it broke apart. It was alloy steel and I never understood how gunsmiths weld actions and barrels. I had a Weatherby 378 mag and there was a second lug welded on the barrel right under the chamber. It must be safe or Weatherby would have done it another way. So how do you weld on alloy steels and do it safely. Also what solder is used on the double rifles. I hope someone knows.

What's the alloy of the lug and the receiver and what wire are you using ??
Higher carbon and or alloying material requires pre-heat and post-heat usually.
4140 is commonly welded .

What he said; depends on the amount of carbon in it; if you tried to weld steel with more than about .4 percent C, it will do what you experienced. 4140 is not a problem to weld or solder. Actions are easy too; still depends on the carbon content. Old deep case hardened actions are very difficult to weld unless you preheat to drive the C out. Wrought iron; possible but you get bubbles and pits from the slag. Old malleable iron frames; forget it.

I was using ground unhardened O1. I did not know about the carbon content and after it broke I thought all heat treatable steels would crack. As you say I know allot of gun builders weld 4140. All the TC barrel people weld their lugs and JD Jones is the only one that said he sent his out for heat treatment. I know a company making missile housings were having 4140 parts welded with EB process. Any words of caution by experienced pro's.?

Okay, now we know about the carbon facet of the job, let me ask Other questions as a genuine attempt to bolster my own knowledge and maybe someone elses'....

What are the important consideration in the wire used? Should it be of an alloy similar to that of the work being welded? (Seems it might be important the parts melted and flowing together in the welding process should be very compatible xo that they thoroughly mix well and have common grain structure as they cool.)

How about the temp of the welding heat...does it need to be hotter when welding alloys, to assure adequate flow and intermixing?

What about the flux?

No wonder ! O-1 is a tool steel with 1.0 % C at least .That does present a big problem .Preheat at 400 F and post heat at 400F at least ! Why do you use O-1 ? Modern receivers and barrels are 4140 .Make the lug of the same with suitable wire and you've got it !!

4140 to 4140

ER80S-B2 Series Tig Wire. 3/32 diameter.

Heat inputs (Volts-amps) would be similar to welding A-36, maybe slightly hotter

Preheat to 400º F Minimum. Do not guess, use a temp stick or temp probe. Measure the temperature approximately 1/2" to 3/4" from the weld to make certain the area is totally soaked.

Keep your inter pass temperature under 600 F.

Extremely important: Allow to cool very slowly after welding. Wrap weld in K-Wool or similar blanket. Cooling rate should be no more than 100-120º F per hour.

In my world we would Post Weld Heat Treat (PWHT) otherwise known as stress relieve a 4140 weld. Lower transformation temperature of 4140 is probably around 900º F and tempering temp around 1400º F (Those are just educated estimates). For PWHT to be effective it would need to exceed the lower transformation temperature and remain under the tempering temperature. We PWHT 4130 at 1175º F for 1 hour per inch of thickness.

It would not be practical to PWHT a barrel in that manner as the machined surfaces would likely be ruined in the process unless it was under an argon purge.

I would assume some of these parts are hardened also. If you are welding on a hardened part such as a bolt it would be extremely wise to re-harden the weld area.

Also this advice is for informational purpose only. Talk to your consumable supplier they should have good advice. Remember that welding companies spend thousands if not 10s of thousands of dollars to prove a welding procedure is correct using hardness surveys, yield strength test, tensile strength test, side bends, root bends, face bends, charpy V-notch tests, CTOD testing etc.

Always use "like" filler rod

4140 to 4140

So on and so on

You can't weld tool steel; at least the home hobbyist can't. I have welded plain cold rolled steel to 4140 (barrel lugs) plenty of times. With plain wire.

dpcd, as a metallurgist one of my interesting projects was to weld hardened tool steel and end up with hardness of steel and weld very close to the original hardness. Yup I did it !

I know you did it but I don't recommend it to most of us; we aren't metallurgists. I tried it once and it broke like the OP's did.

quote:

Originally posted by dpcd:
You can't weld tool steel; at least the home hobbyist can't. I have welded plain cold rolled steel to 4140 (barrel lugs) plenty of times. With plain wire.

I'm sorry....I forgot I TiG weld tool steel for a living

As for dis similar use 680T or Brutis tig filler rod

Plain wire?

MIG wire that Farm and Fleet sells. Argon gas shield.

Gotcha

You will have to explain that. I don't weld tool steel and have no need to do so.

4140 is an oil quenching tool steel.....so you already have welded with "tool steel"


Explane how I weld tool steel?

I meant why you said gotcha; I now think that might mean "understand". Sorry. My brain is getting old.

A tip for those in need of parent metal filler rod but you don't want to buy any....

from an old school toolmaker....to you

Grind a lathe tool bit to curl a chip but not break it.

Chuck up said steel of choice and turn a 4 or 5" section down...saving your long tight curly strands of "chips"

Whalla!!!!

Filler rod !!!

Only believe 10% of the BS that you read on the internet,unless you've been there & done that..preferably for a living!!!