According to the applied characteristics of X70 pipeline steel with hydrogen sulfide corrosion resistance

the technical ideas of low carbon

ultra-low sulfur

ultra-low phosphorus and controlled Mn content are used to control the number and shape of MnS inclusions

as well as dendritic segregation and center segregation of casting blank. Through controlled rolling and cooling experiment in laboratory

the effects of various finishing temperatures and final cooling temperatures on the microstructure and performance are analyzed. The experiment results show that

with finishing rolling at 820 ℃ or 840 ℃

the microstructure of quasi-polygonal ferrite + granular bainite can be obtained

with the decrease of finishing temperature

grain size decreases ； with the decrease of coiling temperature

the content of granular bainite increases. Based on the experiment results

the industrial production plan is determined

and the trial production has been completed. The experiment results show that

with finishing rolling at 820 ℃. and coiling at 400℃

the product with microstructure of quasi polygonal ferrite + granular bainite can be obtained

it shows excellent comprehensive performance

the anti-HIC sensitivity is 0

and the anti-SSCC performance is not invalid.