Can straight seamless steel tubes be bent to create elbows?
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There is a liquefied gas pipeline that requires a elbow; no pre-made elbows were available, so the maintenance workers used gas welding to heat the straight pipe and created an elbow on the spot. But surely this isn’t a proper solution? What do you all think? And when welding, is it still necessary to grind bevels on the steel pipes?
First, it is necessary to specify the material of the pipe; here we will assume carbon steel as the material in question. 1. The heating temperature during the production of elbows must be 750° or higher. 2. Regarding the groove formation on elbows, this depends on the pipe diameter and wall thickness: for carbon steel pipes with a wall thickness of less than 5 mm, a flat groove is sufficient, while for those with a wall thickness greater than 5 mm, a groove is required. For stainless steel pipes, the wall thickness limit is 3 mm. If the processing temperature is below 750°, heat treatment is necessary, and the hardness must not exceed 156. Considering practicality, the requirements for other pipe fittings can be ignored; however, the points mentioned above need to be taken into account
Tolerances such as size and diameter can be ignored since you can use them anyway; they have an extremely minor impact in actual use
Use a hydraulic bending machine for cold bending; the steel pipe will not deform, the error is small, and there is no risk of annealing, but the resulting curvature is quite large
Cold-formed parts must undergo heat treatment; they are not allowed to be used in pressure pipelines without it
It’s professional; no doubt about it! ! !
Elbows can be made, but their corrosion resistance will decrease
I don’t know much about this area; I’ll refer to the answers from above and learn from them