Wasn't getting updates form some reason.
For frame tube material there is not much practical difference between CREW, DOM, or 4130. CREW and DOM are plain low carbon steels. For a given diameter and wall thickness all 3 have the same weight and stiffness which is the primary factor in frame design. The main material difference is that the 4130 has a higher yield strength than the other 2 but no material should be subject to stresses near yield in normal operation. Crashing is a different story but then again if you crash you should expect your frame to get bent. I think it was Kevin Cameron who said that his riders could not crash in a controlled enough manner to stay under the 4130's yield point so it was a wash.
With that said, I still like to use 4130 material in my frames. I find the higher quality material has better straightness and profile accuracy mainly due to the fact that it is a more expensive product. It does require care to be taken not to use too much heat when welding so has some drawbacks but they are not insurmountable.
For a beginning welder I would recommend using CREW or DOM. There are much less welding related strength and brittleness issues when compared to 4130 and we all must learn to walk before we can run. Once you've got some fab experience under your belt try some 4130. you may like the better accuracy or may consider the additional price to be a waste and stick to mild steel.
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