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4130 Chrome Moly Steel Tube Seamless vs Welded Seam ??

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  • 4130 Chrome Moly Steel Tube Seamless vs Welded Seam ??

    I'm looking for some info on a length of 2" OD x 1/4" wall 4140 chrome moly steel tube.
    I've found the stuff in both welded seam and seamless. Both have about the exact same stress rating and yield strength.
    I'm wondering how that can be?? From what I always remember seamless was always considered the superior of the two.
    I know manufacturing processes have improved greatly since I last looked at this stuff... 10 years ago or so, so are they both considered the same now?? I suppose what I need to do next is get the ASTM rating of each and compare them that way.

    JL..................

  • #2
    There is 'as welded' and then DOM which is welded then drawn over mandrel asfaik. I suspect the DOM would compare favorably with seamless. Have a hard time believing 'as welded' would compare as favorably, but this gets above my pay grade pretty quick.

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    • #3
      I would think if you had to part the stuff off and things like that then the seamless might be better to avoid the hardened weld section that can raise holy hell. although if what Softtail just stated is true it might not matter then... ?

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      • #4
        I think all the "tube" is DOM after the seam is welded. Were not talking pipe.

        I did find this ................ http://www.hysteelpipe.com/steel-knowledge/api-5l-astm-a53-seamless-vs-welded-steel-pipe/

        This better explains it............... http://www.stlpipesupply.com/blog/we...seamless-pipe/

        JL..............

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        • #5
          Originally posted by JoeLee View Post
          I think all the "tube" is DOM after the seam is welded. Were not talking pipe.
          The first link reads that there are both... DOM and 'non DOM'. Tried to cut n paste but wouldn't let me.
          I believe the ERW designation means that it is not DOM and of course not seamless.

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          • #6
            This explains it well:

            https://www.metalsupermarkets.com/di...seamless-tube/

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            • #7
              If the material is the same, it makes sense that many of the ratings will be the same. For example, the maximum tensile load would be identical. It is left up to the engineer/design/fabricator to determine the effects of the seam.

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              • #8
                I would have to assume that DOM is superior in strength as it is always the required material for certified roll bars and cages in racing. Other than appearance and finish, it would seem to be unnecessary to run it through the additional process otherwise.

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                • #9
                  Originally posted by BMW Rider View Post
                  I would have to assume that DOM is superior in strength as it is always the required material for certified roll bars and cages in racing. Other than appearance and finish, it would seem to be unnecessary to run it through the additional process otherwise.
                  Improved grain structure/orientation evidently. Also a very dimensionally uniform tube (good for welding).. more so than seamless.

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                  • #10
                    As I recall, mandrel drawing is performed on larger sizes that are welded.

                    The processes I saw were: forming of the flat strip to tube form, high frequency welding, low frequency seam anneal
                    cut to length on flying saw, then sometimes automatic hydraulic test of the lengths.
                    This is an extremely noisy process although it is mostly automated.
                    Then on to the drawing processes, maybe on Pilger mills.

                    A few years ago I attended the Experimental Aircraft Association OA welding class for 4130 tube.
                    OA welded 4130 tube frames have been used for smaller aircraft since before WW2.
                    I checked the course book and there is no mention of orientation of the seam when building frames.

                    I use 4130 tube here for bike frames and it is not possible to see the seam.

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                    • #11
                      Originally posted by wombat2go View Post
                      I checked the course book and there is no mention of orientation of the seam when building frames.

                      I use 4130 tube here for bike frames and it is not possible to see the seam.
                      Both may have been seamless. 4130 comes in DOM, seamless, ERW, etc.

                      There are guidelines for bending 4130, so my guess would be if there is a seam, there probably is a best orientation for it.

                      Related, bicycle tubes are not straight, despite the premium put on a builders alignment being 'so and so'. Take a butted tube and roll it across a surface plate. Best case they are banana shaped.. worst case, more like a corkscrew. The banana shape gets oriented in the vertical plane of the frame to minimize it effects. Akin to crowning dimensional lumber.

                      I love building with seamless 4130 as it is generally very straight/uniform, easy to cut and weld and comparatively cheap.

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