How to Eliminate the Residual Stress of hot expanded Steel Pipe Effectively

what is residual stress?

The stress that remains inside the metal after the external force is removed is called residual stress or internal stress. Residual stress is due to non-uniform deformation and non-uniform volume change of the metal.

What are the hazards of residual stress?

Residual stress has an extremely important influence on the shape, size and performance of the workpiece. When it exceeds the yield strength of the material, it will cause deformation of the workpiece. When it exceeds the strength limit of the material, it will cause cracking and partial size or shape change of the workpiece. , greatly reducing the service life of the workpiece.

The steel pipe adopts Hot expanded technology to improve the mechanical properties of the steel pipe and effectively eliminate the residual stress (internal stress)

The diameter expansion process is equipped with intermediate frequency heating equipment to heat only the deformed part of the raw material, and the heating is fast, uniform and controllable, saving energy. The tapered inner mold mandrel can also be replaced quickly to realize flexible production and changeable finished product specifications.

In addition, it can destroy the forging structure of the steel pipe, advance the deformation at a uniform speed and control the temperature, refine the grains of the heat-expanded steel pipe, and eliminate the defects of the microstructure, so that the structure of the heat-expanded steel pipe is dense and the mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the thermal expansion steel pipe is no longer isotropic to a certain extent; the bubbles, cracks and looseness formed during pouring can also be welded under the action of high temperature and parallel pressure .

After the steel pipe is thermally expanded, the hardness of the steel pipe can also be reduced and the plasticity can be improved to facilitate subsequent cutting or cold deformation processing. Finally, the internal stress of the steel pipe is greatly eliminated to prevent deformation or cracking!

The two-step push-type pipe expanding machine used in thermal expansion steel pipe integrates cone die diameter expanding technology, digital intermediate frequency induction heating technology, and hydraulic technology in one machine. With its reasonable technology, low energy consumption, low construction investment, good Excellent product quality, wide range of raw materials and product specification applicability, flexible and low-input production batch adaptability, replaced the traditional pull-type diameter expansion technology in the steel pipe industry, and is now widely used.