Originally Posted by kalescustom
Just to clear things up, 4130 is NOT T45. 4130 is not accepted by may sancioning bodies due to how brittle it gets in the HAZ.. The only way to solve that problem is to normalize the material. Since there is really no way to prove the joints have been normalized. You cannot use it.
T45 is Carbon Manganese Steel. You cant even buy it in the US and the only place that I have seen it being used is in FIA Homoligated roll cages. AKA Custom Cages UK. Its got around the same tensile strength as 4130 but its properties dont change with heat.. meaning you can even MIG weld it..
Save some money and make your subframes out of DOM 1020. Use 1" x .080". Design it well.
Looking at the differences between 4130 and 1020 (price and strength) I may change my mind from my previous statement. Properly designed with appropriate safety factors, the part made with 1020 will only be about 10% heavier. A properly designed subframe will weigh around 15 lbs, that's only a difference of 1.5 lbs. Not a big deal in my book for the cost and hassle.
I'll probably still go with 4130 for my stuff, but will more seriously consider 1020 as a good option.