4140 welding

whaqt would be the correct procedure to weld up a crack in hardened

4140 on a rifle receiver? I'm asking for another person, glad its not my problem.

Karl

Reply to
Karl Townsend
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Receiver in 4140? Are you sure?

Where is the crack? Behind or along the locking lugs?

How did the crack happen?

Its pretty important to know. As to the welding...you are probably going to have to anneal the receiver after welding..then reheat treat..if the crack is in a loaded area.

Gouge with a Dremal tool, preheat to 400-500 F, weld with Cronatig

340T or similar

Gunner

Reply to
Gunner Asch

What's the typical hardness of a non-case-hardened bolt rifle's reciever made of some sort of medium carbon steel? :)

Are you sure they're heat treated?

Spark test it. :) Is it -really- 4140? How hard is it now?

Alvin in AZ

Reply to
alvinj

Positve on the 4140. its the trunion on an M2HB. The guy has two cracks. One in the top cover he's already welded and another through the rivet holes along the bottom of the trunion - lot of force here.

You get a pile of parts from a de militarized kit, and then build a weapon. So, no clue on cause of trouble.

Karl

Reply to
Karl Townsend

Use 8018 and preheat, peening etc. If the crack is safety sensitive, I would junk the rifle.

i
Reply to
Ignoramus5200

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RC 35-45

Yes. Common Gun Metals Carbon Steels

1020 and 1520?Common, ?plain? or cold-rolled steel. You?ll find it in trigger guards, floorplates, sights, sling swivels and other steel hardware. 4140?Ordnance steel or chrome-moly steel, it has 0.4 percent carbon and is really strong while still being cost-effective to machine. You?ll find this in barrels, bolts receivers and high-stress items like muzzle brakes. 4150?The same as ?ordnance? steel but with the carbon content upped to 0.5 percent. 4150 holds up better to serious abuse, and it?s found primarily in mil-spec AR-15 barrels. 41V45?A chrome-moly variant, it has a dash of vanadium in it. This is an alloy selected to produce hammer-forged barrels. 8620?This is a full-up alloy of nickel, chromium, molybdenum, with 0.2 percent carbon. Cast receivers are made of this alloy because it fills the mold well, machines cleanly and ends up very tough and strong.

Stainless Steels

316?Also known as ?marine? grade stainless, as it resists corrosion well because of added molybdenum but is not easy to harden. Used in trigger guards and floorplates. 17-4?An alloy with 17 percent chromium and 4 percent nickel. 17-4 (or a close kin) is readily hardened and is used in barrels, bolts and receivers.

Aluminum Alloys

6061?Aircraft aluminum, selected in that application for its light weight and ease of fabrication into complex parts. Floorplates on hunting rifles, scope rings and some handguards and buffer tubes on AR-15 rifles are made of 6061. 7075?Much stronger than 6061, it?s the alloy used in AR-15 upper and lower receivers, some mil-spec brands of buffer tubes and some railed handguards. In mil-spec parlance, it is known as ?7057-T6?; the last part designates the type of heat treatment it receives.

Reply to
Gunner Asch

Then my suggestion should work. Is it cracking in the weld..or is it cracking along side the weld? He didnt anneal then reheat treat afterwards did he?

Should reheat treat afterwards. The HAZ is probably causing him problems and needs to be annealed then the whole piece needs to be reheat treated.

Probably best to have a commercial heat treater do the reheat after the repair. Their quality control is better then a guy with a small oven in his garage. Including the argon flood.

Gunner

Reply to
Gunner Asch

You don't junk an M2HB Iggy, you do everything humanly and inhumanly possible to preserve it.

Reply to
Pete C.

Its obvious he doesent know what it is..or what its worth in real dollars.

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$6500-8500 at very low end of the scale..up to $12k

Not something you toss in the scrap bin

Gunner

Reply to
Gunner Asch

You only WISH it were your problem! I have a couple of people in town that I would trust to do the repair, they have worked miracles for me. I could ask them but I won't tell you the procedure unless you send pix of you shooting it afterwards. Side note: What would it take to fab a new one?

Reply to
Tom Gardner

At one time I converted quite a few short (Argentina?) Mauser actions and did Rockwell them to see what I was working with - 55,000 - 60,000 psi. Based on how easy they were to drill I would reckon that many Springfield and early Winchester M70 receivers are in about the same range.

I also "recovered" a number of M1 Carbines that had been demilitarized by being cut in half with a cutting torch by trimming the ends and welding them back together. they were only 30 cal. carbine but never had one fail.

Many years ago P.O. Ackley investigated the thrust of a brass cartridge case against the bolt face. It turns out that when a cartridge is fired the case walls expand against the chamber walls and actual thrust against the bolt face is much less than expected from only considering chamber pressure.

Reply to
John B.

Welding should be performed very carefully as it can affect the eyes directly.

The welding can be performed to adjust and fit the doors may relate to front

of shop or inside of shop and home.

Reply to
smith46

...

I'm so ugly I've been known to break camera lenses. I'll try to send you a pic of Don's lady, Vicky, manning the 50 cal.

A custom machined trunion runs around $1K, top covers only $200. I tried talking "the kid" into a run of trunions as a profit venture for him, he declined.

Karl

Reply to
Karl Townsend

Can he send it back for a less-cracked version, or did his welding screw up that possibility?

Reply to
Larry Jaques

I watched your ex-Governator's new movie yesterday and had a blast. They were firing an old Vickers gun at the cartel guys who had come to town to kill them. The air was filled with a lovely pink mist.

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The other metal-containing movie was Parker, with Jason Statham. It's another two-thumbs-up movie.

Reply to
Larry Jaques

Er, I'm in Texas.

Reply to
Pete C.

Sorry, I thot I saw Gunner at the helm of that message. Shrub never did movies.

Reply to
Larry Jaques

LOL..send it back where? The US Government?

Reply to
Gunner Asch

Crosspost this baby to a welding group or two Karl! :)

And there's a metallurgy group too... sci.engr.metallurgy

This can't be that hard to do, just need to know how is all. xD

Bet there's guys out there that could make it stronger than new.

Alvin in AZ is a pimple on a real metallurgist ass! :) ...that's one-step-up from "wouldn't make a pimple-on..." see? ;)

Reply to
alvinj

Maybe it's still under warranty! A number of years ago I called GE motor division and asked if a 5hp motor made in 1918 was still under warranty and they wanted the old one as is was somewhat rare and gave me a new one...under warranty!

Reply to
Tom Gardner

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