Over the past twenty years,significant advances have been made in the field of microalloying and associated application,among which one of the most successful application cases is HTP practice for heavy gauge,high strength pipeline steels.Combined the strengthening effects of TMCP and retardation effects of austenite recrystallization with increasing Nb in austenite region,HTP conception with low carbon and high niobium alloy design has been successfully applied to develop X80 coil with a thickness of 18.4mm used for Chinas Second West-East pipeline.During this process,big efforts were made to further develop and enrich the application of microalloying technology,and at the same time the strengthening effects of Nb have been completely unfolded and fully utilized with improved metallurgical quality and quantitative analysis of microstructure.In this paper,the existing status and strengthening effect of Nb during reheating,rolling,cooling and welding have been analyzed and characterized based on mass production samples and laboratory analysis.As confirmed,grain refinement remains the most basic strengthening measure to reduce the microstructure gradient along the thickness,which in turn enlarges the processing window to improve upon low temperature toughness,and finally make it possible to develop heavy gauge,high strength pipeline steels with more challenging fracture toughness requirements.As stated by a good saying that practice makes perfection.Based on application practice and theoretical analysis,HTP has been extended to develop heavy gauge and high strength pipeline steels with increasing requirements,including X80 SSAW pipe with a thickness of 22.0mm and above,X80 LSAW pipe combining heavy gauge and large diameter,heavy gauge X80 LSAW pipe with low temperature requirements,as well as X90 steels.In this paper,alloy design,production processing,as well as mechanical properties and microstructure used for these products would be illustrated.