Cause of Band Structure in Typical Carbon Steel High Pressure Boiler Tube and its Influence on Endurance Strength

The formation mechanism of band structure in carbon steel is introduced and the influence of different steelmaking processes on band structure in hot-rolled SA210Gr.C and 20G carbon steel high pressure boiler tubes are analyzed.The changing status of the band structure during the rolling process and the influence of the band structure on the creep rupture strength of the tubes are studied.The analysis shows that by adopting the small size billets and the mold casting and forging process，and lowering the content of Mn，the band structure in the rolled tubes may be alleviated to a certain degree.It is found that even when the finishing temperature is above 1 000℃，the band structure is still obvious.The band structure has slight influence on endurance strength，but even for tubes with severe band structure，their endurance strength can still meet the relevant standard requirements with big margin.