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Steel vs. Chrome Moly

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlazerGuy, Jun 17, 2000.

  1. BlazerGuy

    BlazerGuy 3/4 ton status

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    What's the difference between these two? Which one is stronger? Which one costs more? Thanks for your advice.

    http://www.blazer.coloradok5.com is now under construction[​IMG]
    YEEEE HAWWWW[​IMG]
     
  2. Bigd

    Bigd 1/2 ton status

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    Not 100% sure but i do believe that crome moly is stronger and lighter.But alot more expensive.Can't remember if there is welding issues or not?Anybody else?
     
  3. nyyef

    nyyef 1/2 ton status

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    i think crome-moly is a little more brittle.
    dont quote me. but it is lighter, i know that for sure.

    Knife.
     
  4. bablazer73

    bablazer73 1/2 ton status

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    chrome moly is stonger and lighter than steel. welding issues? don't know of any. I used a tig when we put the cage in my racecar. it is more expensive, but the weight savings is quite nice. lighter means faster! going to put a full cage in my blazer after the body swap gets done.

    your right. I don't understand the jeep thing!
     
  5. stephan van leir

    stephan van leir 1/2 ton status

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    Iron and carbon mixed in the smelting yeilds steel. Now on to steels proporties. The SAE. has set standards for steel "groups" in 4 diget numbers.The first are the group, the second refers to the amount of carbon in 10ths%. For instance, 1030 grade steel has .30% carbon. 10xx,11xx,12xx,and15xx are all mild steel. 15xx being the stongest. 15xx is what your k5`s frame is made from, and 1040 is what your axel shafts are cast from. These groups can have upto 1.65% manganess content. These groups are vevy ductile yet they can fail easily. Now on to alloys. Anything over 1.65% mang.or any other element is considered an alloy. Now 41xx is the chrom moly group. they contain .50 .80 or .90% chromium, and either .12 .20 .25 or .30% molybdenum. This is a Very hard steel alloy that is reasonably ductile. The chromium incresses hardness and elastisity. The moly is more of a stabilizer in the smelting process, or actually a bonder. 43xx, 47xx,and 86xx are all nickel chrom/moly alloys. they contain .50% chromium,.25% moly., and 1.82% nickel. The 86xx group has a slightly different mix. As you can plainly see the alloy groups have a magor advantage over the mild steel. Most all raceing rules require 4130 chrommoly tube be used for ALL roll and crash stuctures on a race car or truck. The main idea is that 4130 can compress drasticly upon impact, than return the stored energy into actually flexing back into its original(or close to) shape. In general terms the 4130 is about twice the strenght of 1040. It also cost about that twice the amount more for the steel companies to make. Did I mention that Molybdenum is a trace element that is mined from crushed ore. It takes 20 ton of Colorado mountains to get 3lbs of that poisonous powder.
     
  6. BlazerGuy

    BlazerGuy 3/4 ton status

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    I wanted to get a rollcage/rollbar, and I think I want to go with the chrome moly one.

    http://www.blazer.coloradok5.com is now under construction[​IMG]
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  7. James90

    James90 1/2 ton status

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    how much would it cost to get one made of chrome/moly I want to get one too

    [​IMG]Go prepared
    </font color=red>90 k5 soon to be big, bad, and mean
     
  8. Donovan

    Donovan 1/2 ton status

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    Chrome Moly and regular steel weigh the same. There is no difference in the weight of the material. You get the weight savings with Chrome Moly by being able to use thinner wall tubing than regular steel. If you say your tubing is 2" with .120 wall you could go down to say .080 wall and be just as strong as regular steel. This is very helpful if you are racing and need to save weight but I don't think that it would benifit you to spend the extra money to put Moly in your roll cage. One benifit I would see with using Moly cage is you could have a better center of gravity than some one who used regular steel in it. I don't think that you would notice that much.

    Donovan
     
  9. Blazer79

    Blazer79 1/2 ton status

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  10. stephan van leir

    stephan van leir 1/2 ton status

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    Sorry but mild steel is NOT as strong as chromoly. You did not take into account the ductility ( the ability to flex with out deforming)of chromoly. Maybe you don`t need the moly tube but don`t think that all steel tube is going to work the same, regardless of wall thickness! Roll a mild steel cage and it will crush to it`s point of failure. Roll a moly cage and the thing will spring back(consuming energy) untill the energy cycles cause deformation. If you want to find out for real,ie no bull, than contact the SCCA racing sanctions or any other for that matter. They will tell you how it truely is.
     
  11. Donovan

    Donovan 1/2 ton status

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    I don't believe I said that Mild steel is as strong as Chrome Moly. I am not that stupid. I did say is the reason for the use is you can use thinner tubing because the Moly is stronger than Mild steel. So don't get all bent out of shape. I do understand that all steel is not the same. Just look at the Yield strength of 1020 steel and it is 60000psi and the 4130 is 75000psi which is close but if you go and look at the Tensile strength which is the breaking point of the steel and the 1020 is only 70000psi which is whose than Moly's yield. This is where the moly is better and it is 95000psi. This is where you get the added (spring back value).

    Donovan
     
  12. Michael

    Michael 1/2 ton status

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  13. nyyef

    nyyef 1/2 ton status

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    chrome-moly has a very high tensile strength, but roll cages see little of that tension. toughness is what cage material has to have. toughness is the ability to absorb impact. very important in cages, frames...etc. rather than breaking a tough material will absorb the impact.

    here is what Ron Fournier said in his book Metal Fabricators' Handbook (very good book):
    "comment about using chrome moly - DONT. There are few applications that warrant the use of chrome moly unless you're building an airplane, formula one car, or an indy car. Unfortunately, chrome moly steel has become 'trick'. It literally falls in the category of a little bit of knowledge can be dangerous. yes, it is stronger than mild steel. IT IS ALSO LESS TOUGH. under impact, as in a crash, a chrome moly-steel part is much more likely to break rather than bend, as would a mild steel part. not only does a part -such as roll bar or cage- absorb energy as it bends, it remains intact and protects. so choose toughness when life depends on it".
    he also mentions that chrome moly must stress-relieved.
    he also adds (just for everyones info)"professional builders very frequently use cold-drawn seamless steel tubing or seamless mild steel......he recommends 1-3/4"OD 0.125 wall thickness, cold drawn seamless steel.....ABSOLUTE MINIMUM 1-1/2"0.083 thickness.

    sorry for the long post....just sharing info....its a good book if you are in to custom made stuff.


    Knife.
     
  14. Scoobydoo

    Scoobydoo 1/2 ton status

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    Stephan, certainly had the definitive answer didn't he!!![​IMG]
    But now my brain hurts [​IMG]
     

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