Tube bending production process
At present, there are basically two kinds of pipe bending production processes in China:
The first type: small-diameter pipeline, the general outer diameter specification is ≤89mm, and cold bending is usually adopted, which is carried out by manual or numerical control pipe bending machine. After bending, annealing heat treatment is needed to eliminate the deformation stress inside the bent pipe.
Type 2: large diameter and high pressure pipelines usually have an outer diameter of ≥114mm and are usually hot bent. Medium-frequency heating is used to heat the pipeline, and mechanical or hydraulic mechanism is used to apply external force to bend the pipeline.
Comparison of two processes:
Cold bending does not change the organizational structure of steel pipe, and keeps the original mechanical properties of steel pipe well, but because of its great deformation resistance, it is not suitable for bending of large diameter and thick wall pipeline; At the same time, cold bending will produce great stress concentration, so it is necessary to anneal the pipeline.
Hot bending needs to heat the pipeline, which has certain influence on the mechanical properties and service life of the pipeline itself. Usually, in order to better ensure the service performance of elbow, the elbow should be heat treated after hot bending if necessary.
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