Preheating Metals for welding?
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  1. #1
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    Preheating Metals for welding?

    Hello All,

    I was wondering, if there was a general rule of thumb for pre-heating metals prior welding?

    I have a flux core welder (cheap) and due to the limitations of only having 120v available, a bigger welder is not an option.

    With my limitations, I understand it's possible to weld thicker material using a weaker welder (with limitations), if you can pre-heat first.

    Everything will be mild steel for the most part. There is a project where I wanted to weld a 1.5'' thick plate, on top of a 5'' square tube with .120 wall. Would this be too much to ask of a 120v flux core welder, even if pre-heating beyond non-magnetic is possible?

    The idea behind this project, is making a post, that can hold my hardy tools for blacksmithing. The plate already has a square hole in it for tools.


    Thank you,
    Mud

  2. #2
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    Re: Preheating Metals for welding?

    honestly for what your doing with it, you should be fine, alot of people will say "but you wont get pen!" but its a tool holder, pre heat it a few hundred degrees if it makes you feel better and just put a heap of runs on it, something will stick.

  3. #3
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    Re: Preheating Metals for welding?

    One and one half inched thick ?
    NO.
    Drill two holes in each of 4 pieces of 1/8" x 1.25 or 1.50 angle iron and weld around the perimeter of that tube.
    Sit the plate on, mark the holes and drill and tap that plate for some....oh..... 3/8" x 3/4" bolts and bolt the thing up.

  4. #4
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    Re: Preheating Metals for welding?

    Quote Originally Posted by ttoks View Post
    honestly for what your doing with it, you should be fine, alot of people will say "but you wont get pen!" but its a tool holder, pre heat it a few hundred degrees if it makes you feel better and just put a heap of runs on it, something will stick.
    I will try it, and when it fails, I'll do what Bonzoo recommended. I'm limited by the available power, so just doing what I can with what I have. This won't be holding anything more than a few hardy tools. If it works just long enough for me to find a friend to weld it up proper, I'll be happy.
    Quote Originally Posted by Bonzoo View Post
    One and one half inched thick ?
    NO.
    Drill two holes in each of 4 pieces of 1/8" x 1.25 or 1.50 angle iron and weld around the perimeter of that tube.
    Sit the plate on, mark the holes and drill and tap that plate for some....oh..... 3/8" x 3/4" bolts and bolt the thing up.
    Thanks, I will try that.

  5. #5
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    Re: Preheating Metals for welding?

    A quick test for the need to preheat is to set up the two materials in a Tee joint and run a short fillet weld. Then take a hammer and bend the assembly so that the stress is at the root of the weld and break it apart. Inspect the broken weld. If the weld tears out in parent metal then you need preheat. If the fracture occurs in the weld metal then no preheat required. If the weld fracture occurs exactly at the surface of either material then you are not fusing into the material because of incorrect manipulation or heat settings on the machine. ( cold lap)

  6. #6
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    Re: Preheating Metals for welding?

    If u only got a 110 volt welder then for thicker stuff preheat where u are going to first make your weld would be a good idea. That way it won't have a cold start

  7. #7
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    Re: Preheating Metals for welding?

    Just making a post to hold tools and you won't be pounding on it? Can't see anything wrong with it personally.

    Not ideal, but preheating will help. Bolting like mentioned will work really well though.
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

  8. #8
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    Re: Preheating Metals for welding?

    I was taught, and it has worked for me all these years, that you can soot over the metal with just the acetylene flame on the torch. The back off a ways from the metal and heat until the soot burns away. It should do this at about 400 degrees or slightly more. Start welding.

    Or you could just get heat sticks.

  9. #9
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    Re: Preheating Metals for welding?

    Quote Originally Posted by lotechman View Post
    A quick test for the need to preheat is to set up the two materials in a Tee joint and run a short fillet weld. Then take a hammer and bend the assembly so that the stress is at the root of the weld and break it apart. Inspect the broken weld. If the weld tears out in parent metal then you need preheat. If the fracture occurs in the weld metal then no preheat required. If the weld fracture occurs exactly at the surface of either material then you are not fusing into the material because of incorrect manipulation or heat settings on the machine. ( cold lap)
    Thank you
    Quote Originally Posted by motolife313 View Post
    If u only got a 110 volt welder then for thicker stuff preheat where u are going to first make your weld would be a good idea. That way it won't have a cold start
    Thank you, I understand there's limits. So I wasn't going in with high expectations.
    Quote Originally Posted by MinnesotaDave View Post
    Just making a post to hold tools and you won't be pounding on it? Can't see anything wrong with it personally.

    Not ideal, but preheating will help. Bolting like mentioned will work really well though.
    We'll it'll be used under tools that get hammered. But I'm not expecting it to hold for long. For bolting, while the best option from what it sounds- The plate I made, unfortunately is a hair smaller then the tube. But i'm sure I can just use flat plate also.
    Quote Originally Posted by Bob View Post
    I was taught, and it has worked for me all these years, that you can soot over the metal with just the acetylene flame on the torch. The back off a ways from the metal and heat until the soot burns away. It should do this at about 400 degrees or slightly more. Start welding.

    Or you could just get heat sticks.
    I haven't heard of this before, although I'm a new to it as well.

    Does stick welding off more options even at 120v? I was considering an Esab MiniArc in the future.

  10. #10
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    Re: Preheating Metals for welding?

    Tha is for the help fellas. This is where I ended up. Will go with the bolting method when this fails.




    Last edited by Mudman; 06-12-2018 at 11:01 PM.

  11. #11
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    Re: Preheating Metals for welding?

    That isn't going anywhere. You should explain yourself better from the git-go

  12. #12
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    Re: Preheating Metals for welding?

    Quote Originally Posted by Bonzoo View Post
    That isn't going anywhere. You should explain yourself better from the git-go
    I'm definitely terrible at it. What should I have done to explain better? I'll try to do better next time. Sorry

  13. #13
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    Re: Preheating Metals for welding?

    Quote Originally Posted by Mudman View Post
    I'm definitely terrible at it. What should I have done to explain better? I'll try to do better next time. Sorry
    If verbal explanation isn't a strong suit, use pictures to your advantage
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

  14. #14
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    Re: Preheating Metals for welding?

    I understood what he is saying but only because I am familiar with Blacksmithing

  15. #15
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    Re: Preheating Metals for welding?

    just get a good bevel ... it's gonna take a few passes with the 120 ... make sure you have at least a 14ga power cord ..12 or 10 ga rxtension cord will really help you ..and at least a 4 ga ground cable... Those two things will make a small welders world of diffetence ... youll be ablr to turn up the wire and it wont kick back

    Sent from my LGLS992 using Tapatalk

  16. #16
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    Re: Preheating Metals for welding?

    Quote Originally Posted by MinnesotaDave View Post
    If verbal explanation isn't a strong suit, use pictures to your advantage
    Thank you, I'll post up pictures next time.
    Quote Originally Posted by drujinin View Post
    I understood what he is saying but only because I am familiar with Blacksmithing
    It's ugly to look at, but so far so good.
    Quote Originally Posted by jd_830 View Post
    just get a good bevel ... it's gonna take a few passes with the 120 ... make sure you have at least a 14ga power cord ..12 or 10 ga rxtension cord will really help you ..and at least a 4 ga ground cable... Those two things will make a small welders world of diffetence ... youll be ablr to turn up the wire and it wont kick back

    Sent from my LGLS992 using Tapatalk
    Thanks, I use a 10g extension cord from a dedicated 20amp circuit. Will upgrade the ground cable next.

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