Conclusions...
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Thread: Conclusions...

  1. #1
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    Conclusions...

    I had read this quote in the General Welding Questions Forum this A.M. ...

    Cold rolled steel doesn't bend well at all. It is work hardened material. If you take a piece of 1/4 cold rolled flat bar and even bend it with a one inch inside radius, it will more than likely crack or even break.
    Well you should all know me by now..
    If I read or hear something that I'm not sure of..

    Its time to "check it out"
    So we all can see the results first hand..

    The original question was about 1/4" square stock and if it will bend or not without heat..
    So on with the show!!

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    Well my conclusion is that yes it can be done without breaking and cracking..
    OK so..
    I've done my experiment..
    And I give it a thumbs up!

    I'll try anything once..

    ...zap!


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  2. #2
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    Re: Conclusions...

    I always thought cold worked was the material of choice for cold forming. I've never seen someone take an english wheel or hammer and sand bag to a piece of hot rolled steel. I've never seen hot rolled tubing go through a tubing bender, either.

  3. #3
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    Re: Conclusions...

    I don't konw... I will say that in the past I have seen (with my own eyes) cold rolled develope small tears at each edge of the plate, along the line of the break tool. I have never seen it break like I have AR but there again it could have to do with the grain of the material..... again people have to understand that steel has a grain just like a piece fo wood does. Picture it like this.... If you take a plank, say 1" x 12" x 12" with the grain running the place it over a sharp corner so that the corner runs across the grain. Push on both edges and try to break it. It probably won't break. Now turn the plank so the corner runs with the grain and do the same thing, pushing the same way.... It will probably break and faily clean, right on the grain line.

    This could very well be what I was seeing.
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  4. #4
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    Re: Conclusions...

    Is there a easy way to tell the direction of the grain?
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  5. #5
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    Re: Conclusions...

    The direction of the grain follows the direction of rolling... and is parallel to edges of the sheet or bar.

    To bend across the grain is to bend at right angles to the direction of rolling.

    To bend with the grain is to bend parallel to the direction of rolling.

    In steel, the ductility in the direction of rolling is almost twice that at right angles to the direction of rolling.
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  6. #6
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    Re: Conclusions...

    Quote Originally Posted by lorenzo
    .... again people have to understand that steel has a grain just like a piece fo wood does.
    Not a correct statement

    Quote Originally Posted by lorenzo
    The direction of the grain follows the direction of rolling... and is parallel to edges of the sheet or bar.
    Not a correct statement


    First off....I am not hear to point out mistakes or shoot people down....however I feel compelled to educate whenever I can based on my knowledge and experience in the fields that I have succeeded in.

    soooo....metals have crystal structures but, they can not be described as or compared to wood grains. However, there are certain materials and objects, such as Ni- based superalloy turbine blades, which are directionally solidified in an investment cast process, which leaves their crystal structure directionally solidified. This is so they can withstand force directionally. I know I have not backed my argument or explained my point that well.....but unfortunately I am EXTREMLY busy at the moment....give me until Wednesday of next week and I will clarify why most metals, such as CR stl and HR stl do not have a directional grain. It is not grain direction that would cause the bar zap bent to develop cracks along the radius of curvature.

    Below is an SEM (Scanning Electron Microscope) image of the crystal structure of CR sheet metal. Ponder over that for now....it's interesting stuff.

    Last edited by spiral-cut-bevel; 05-02-2007 at 10:22 PM.
    -Graham-
    Mechanical Engineer
    Autosport Mechanic/Fabricator

  7. #7
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    Re: Conclusions...

    Doesn't hot rolled steel have a lot of inclusions in the surface that would make it more prone to cracking during a bend?

  8. #8
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    Re: Conclusions...

    Zap and Graham.....

    Thank you both.....

    Graham, I anxiously await your next few posts.
    Patrick

  9. #9
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    Re: Conclusions...

    Re reading my post I realize I made a mistake in how I worded my comparison with regard to the grain of both wood and steel.

    What I meant to say was steel has a grian, AS DOES a piece of wood.

    Before I start a landslide of crap.... let me say that I used wood as a general aid that most people can quickly connect with because, most of the people here probably understand grain as it relates to wood. I'm sure that are also plenty of people, such as yourself, who understand it in the true sense as it relates to the crystal structures. I was just assuming that some of the folks who would read this may have at some point broken a small board in the manner I mentioned, which may help them visualize what I'm talking about. I'm strictly relating grain to the bending/ forming of steel.

    As to identifying the grian direction......... from what I have read and have been told. The relation of the direction of the grain is as I've described.

    I'm sure I'm going to get educated at this point so I'm ready.
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  10. #10
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    Re: Conclusions...

    It is not a grain direction but size of the grain and the grain boundary among other things that determines the strength of metals.

    I have to reach back 25 years in my mind for some of this info from my under grad engineering days...I am am electrical engineer now.

    Graham will/can come back with more info that your head will be spinning. My best friend is a mechanical engineer that investigates metal fatigue failures in aircraft...very fascinating.
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  11. #11
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    Re: Conclusions...

    [QUOTE=grahamtheengineer]Not a correct statement

    Graham : If you look up in texts that are contemporary to someone like myself I think you will find the term grain commonly used. This was when a electron microscope was but a dream. I was confused as instructors would babble on about grain and crystals.
    The definition that I found was that a grain is an imperfect crystal.
    Hmmm I looked through my old texts: I guess dendritic, equiaxed and elongated grains don't exist any more. Global warming must have caused it.
    I still see instructions on prints for forming plate and there will be notations with arrows indicating required "grain direction" in the plate.
    Also in shops often there are instructions to note the grain direction on all crop plates before returning to stock.
    I'm just an old guy making some "old " comments.

  12. #12
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    Re: Conclusions...

    Quote Originally Posted by bruceb
    It is not a grain direction but size of the grain and the grain boundary among other things that determines the strength of metals.
    I know I am diggin myself a hole here but grain direction has everything to do with strength particularly when weldiing heavy structures one inch and over in thickness. I have even seen drawings demand a particular grain direction for lifting lugs. I don't ask why, I just do it the way the print wants it.
    Lamellar tearing is common in large plate if the weld is located in the wrong place. Here we go again: Imagine edge gluing two boards together as you would do for a table top or cutting board. When you break it the glue line holds and board breaks along it grain. A similar thing can happen when large welds shrink and tear the grain in the steel. A weld placed ninety degrees to this would not suffer the same fate. I could be confusing ductility differences however.
    Also ask anyone who makes pressure vessels which way they roll their shell plates Hmmmm???
    Last edited by lotechman; 05-03-2007 at 07:06 AM.

  13. #13
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    Re: Conclusions...

    Zapster -- I like your approach -- just try it and see what happens. Nothing more revealing than an experiment. Many if not most of human discovery is driven by experimentation. It worked for Thomas Edison! Great stuff.

    DISCLAIMER: yes, yes, if safety or codes are involved we need solid engineering -- but a lot of times the only way to learn first hand is to experiment, as long as there's no danger of somebody getting hurt if the experiment "fails."

    I like the analogy of metal having a grain as does wood -- easy for me to understand and I also look forward to Graham giving more details of what's really going on.

    I'm seated in class at WeldingWeb college.

  14. #14
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    Re: Conclusions...

    The first piece is 1018 cold rolled steel, 1/4 x 1.0 and the other piece is 1/4 x 3/4 A36 bent on a craft bender against a 3/8 dia. pin.

    Every metal company I have ever bought cold rolled from asked me if I was going to bend the stuff because they don't like people to bring back broken pieces and claim the metal was bad. I would never trust my life to a piece bent cold. However, if you heat the area red hot where the bend is to take place, it is safe to bend even after it cools.
    Attached Images Attached Images   

  15. #15
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    Re: Conclusions...

    Looks like I have more mad scientist experiments to do tomorrow..

    ...zap!


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    Professional Driver on a closed course....
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  16. #16
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    Re: Conclusions...

    Quote Originally Posted by 76GMC1500
    I always thought cold worked was the material of choice for cold forming. I've never seen someone take an english wheel or hammer and sand bag to a piece of hot rolled steel. I've never seen hot rolled tubing go through a tubing bender, either.

    I worked many years in precision sheet metal, mostly in aluminum and cold rolled steel. Mostly in the range from 16 gauge to 10 gauge. It does form nicely if bent on the proper radius. The thinner the material, the less likely it will crack. If you put a hem in 16 gauge cold rolled, it will almost always crack. I don't believe the sheet is work hardened as much as flat bar because even 1/8 cold rolled flat will almost always break in a press brake when bent on a 1/8th radius while the 1/8 sheet bends nicely. I never have used an english wheel, but I think metal on a car body is around .039 thick.

  17. #17
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    Re: Conclusions...

    This is exactly everyone here learns something new everyday..
    I love this place!!

    ...zap!


    I am not completely insane..
    Some parts are missing

    Professional Driver on a closed course....
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  18. #18
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    Re: Conclusions...

    Quote Originally Posted by lotechman
    I could be confusing ductility differences however.
    I believe you are absolutely correct. There will be a difference in ductility between bending parallel or prepindicular to the direction that the metal is rolled.

    The main reason you get a tear at a weld is that you have a phase change in the crystal alignment at the weld because of cooling effects. This causes a grain boundary.
    Last edited by bruceb; 05-04-2007 at 12:00 PM.
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  19. #19
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    Re: Conclusions...

    look at the topic "minimum bend radius"

    http://www.ottawaproducts.com/produc...0BEND%20RADIUS

  20. #20
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    Re: Conclusions...

    "GRAIN"
    "A solid polyhedral (or many sided crystal) consisting of groups of atoms bound together in a regular geometric pattern. In mill practice grains are usually studied only as they appear in one plane. (1) Direction of: Refers to grain fiber following the direction of rolling and parallel to edges of strip or sheets. (2) To bend across the grain is to bend at right angles to the direction of rolling. (3) To bend with the grain is to bend parallel to the direction of rolling. In steel, the ductility in the direction of rolling is almost twice that at right angles to the direction of rolling."

    http://www.metal-mart.com/Dictionary/dictletg.htm#I7

  21. #21
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    Re: Conclusions...

    Lets add some Acetone to the fire!!!

    Reading over this thread..

    I love this place!!

    Ok now here are some pics from this afternoon..
    1/4"X2" Cold Rolled flat stock..
    Dirty yes but thats not the point here..

    Subject..

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    The only way to bend this was with a really big adjustable wrench and me hanging off the ground...
    I tried the hammer deal ..No way..
    My hands could not take the shock of the hit..
    So don't do it..

    But anyways..
    Its bending...

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    Now thats pretty bent..

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    I see no signs of fatigue..
    So I dunno..

    This what it is and thats what I have come up with..

    I'll try more if needed..thats no problem..

    But check this out..
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    I don't know how I did it but thats pretty cool..

    ...zap!
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    Some parts are missing

    Professional Driver on a closed course....
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  22. #22
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    Re: Conclusions...

    Is that my shirt hanging from he machine?
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  23. #23
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    Re: Conclusions...



    YUP



    ...zap!


    I am not completely insane..
    Some parts are missing

    Professional Driver on a closed course....
    Do not attempt.

  24. #24
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    Re: Conclusions...

    Hey Zap is it possilbe that your bends aren't with the grain ? And if you were to try to bend it the other way which would possibly be with the grain it would crack and break. Because I have seen metal develop a tear when bent to far or the wrong way Im guessing.
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  25. #25
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    Re: Conclusions...

    When making a bend in any material, a small radius will be more stressfull than a larger one. If you form a 90 degree bend with a 3/8 bend radius in a piece of 1/4 x 1.0 cold rolled steel flat as it comes from the steel distributor, the amount of material from where the bend starts to where it stops is about .75 inch. What you are doing is concentrating all your force in that small area. Commercial cold rolled flat I am talking about has a tensile strength of about 85000 lb. per square inch. Cold rolled steel starts out as hot rolled steel and goes through pickle process and then is run through rollers cold. The more it is cold worked, the stronger it gets. What you gain in strength is lost in bendability. So if you want to do an accurate experiment, bend your metal in some sort of bender, (press brake, hossfeld, shop outfitters, harbor freight.)

    I believe most commercial 1/4 cold rolled flat is full work hardened material.

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