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  1. #1
    Join Date
    Dec 2013
    Posts
    10

    Default Welding forged 4140

    Hey guys! The title says it all. I'm going to be welding a rifle receiver made of 4140. It will only be two beads about 1/16" to 1/8" thick approximately 1-1/2" long. After the weld, it will need to be machined. My questions are: what sort of material should I use for tig welding to a forged receiver? 4140 or some sort of alloy? Since it is going to be such a small amount, should I worry about heat treatment or preheating the receiver?

    thanks in advance!

    Regards, John

  2. #2
    Join Date
    Dec 2008
    Location
    west central Florida
    Posts
    90

    Default

    I would ask your customer if there will be any post weld heat treatment, the answer to that question will tell you what you need to know about what filler to use. Also I presume you are welding material in the annealed condition.

  3. #3
    Join Date
    Jul 2006
    Location
    alaska
    Posts
    181

    Default

    Yup rifle receivers are heat treated and expected to hold about 65,000 psi! When you weld on it you change everything. Why are you welding it anyway?

  4. #4
    Join Date
    Dec 2013
    Posts
    10

    Default

    The receiver rails have been modified slightly and need to bring them back to spec. The area being welded is about 3" away from the chamber which is part of the barrel. I don't imagine the area being welded would see that much stress. Ill give ya a pic!
    Attached Images Attached Images

  5. #5
    Join Date
    Sep 2005
    Location
    Salem ,Ohio
    Posts
    3,913

    Cool

    If it was mine i would build up the area with ER-80S-D2 wire with either mig or tig whatever you are good at. A little preheat to 275 degrees. I would back the area up with copper if possible to save on some grinding. I have a book where a gunsmith cuts a Winchester Mod 70 in half and shortens it a good 1/2" and welds it back together...Bob
    Bob Wright, Grandson of Tee Nee Boat Trailer Founder
    Metal Master Fab Salem, Oh 44460
    Birthplace of the Silver & Deming Drill
    1999 MM185 w/185 Spoolgun,1986 Thunderbolt AC/DC
    Spool Gun conversion. How To Do It. Below.
    http://www.millerwelds.com/resources...php?albumid=48

  6. #6
    Join Date
    Jul 2006
    Location
    alaska
    Posts
    181

    Default

    Interesting,, how were the rail modified? I like guns and used them, fixed, broke, and fought with them. What kind of rifle is that? I cant tell from the pic. I would take the barrel off so I could not to risk screwing the chamber up. I am a little torn about the heat cause I have fired a 50 cal till the barrel actually turned red hot. Did not hurt it but maybe I am just ignorant of the weld part. However, remember welding heat is about 2300 F, shooting doesn't melt it.

  7. #7
    Join Date
    Dec 2013
    Posts
    10

    Default

    Quote Originally Posted by 11b View Post
    Interesting,, how were the rail modified? I like guns and used them, fixed, broke, and fought with them. What kind of rifle is that? I cant tell from the pic. I would take the barrel off so I could not to risk screwing the chamber up. I am a little torn about the heat cause I have fired a 50 cal till the barrel actually turned red hot. Did not hurt it but maybe I am just ignorant of the weld part. However, remember welding heat is about 2300 F, shooting doesn't melt it.
    This is an FAL. The amount that needs to be welded is only about 1/16" in width,1/8" in thickness and 1-1/2" TOTAL length on both sides. The feed rails were opened up to allow better feeding. I can stick weld okay but this is getting tigged by someone who knows what they're doing I presume with 4140. The issues I'm having as far as the repair goes is that the receiver is parkerized. I don't really have a means to stress relieve it after the weld. I wonder how much strength welding and not heat treating would take away?The weld will have to be machined to return OEM spec taper to feed rail, this is no problem at all... I can handle that.

  8. #8
    Join Date
    Jul 2006
    Location
    alaska
    Posts
    181

    Default

    A new receiver is 400.00. New eyes are expensive.

  9. #9
    Join Date
    Dec 2013
    Posts
    10

    Default

    Quote Originally Posted by 11b View Post
    A new receiver is 400.00. New eyes are expensive.
    Your insight has been very helpful. Upon further research, the original FN and Imbel receivers were only induction heat treated in certain spots. The feed rails weren't one of them. This part will be welded and recut. I've been know to suffer from ****-glaucoma.

  10. #10
    Join Date
    Jul 2006
    Location
    alaska
    Posts
    181

    Default

    Let me know how it goes.

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