In this paper,the product designs,mechanical properties and microstructure of ultra-high strength linepipe steel in grade X120 strip with a thickness of 16mm have been shown and analyzed systematically.The tensile tes...In this paper,the product designs,mechanical properties and microstructure of ultra-high strength linepipe steel in grade X120 strip with a thickness of 16mm have been shown and analyzed systematically.The tensile test results with different directions,including transverse,longitudinal and 30° to the rolling direction,showed that the yield strength and ultimate tensile strength reach and exceed 900MPa and 1000MPa respectively,which are far higher than requirements of X120,such as 827MPa and 931MPa.On the other hand,as shown from the test results of Charpy impact tests at different temperatures from 20 ℃ to-60 ℃,the absorbed energies and fracture shear area at-60℃ are about 200J and 100% respectively,which is very exciting and interesting.In order to clarify the strengthening mechanism and effect of X120 strip further,microstructure has been observed through metallography.Analysis of the metallography revealedthat the microstructure was composed of lower bainitewith a size of 1um and fine M/A components.The X120 strip was formed into 1420 mm diameter spiral welded pipe in Huabei pipe mill.Tested results showed that ultra-high strength and high toughness linepipe could be achieved through reasonable alloy composition design and optimized rolling processes.展开更多
文摘In this paper,the product designs,mechanical properties and microstructure of ultra-high strength linepipe steel in grade X120 strip with a thickness of 16mm have been shown and analyzed systematically.The tensile test results with different directions,including transverse,longitudinal and 30° to the rolling direction,showed that the yield strength and ultimate tensile strength reach and exceed 900MPa and 1000MPa respectively,which are far higher than requirements of X120,such as 827MPa and 931MPa.On the other hand,as shown from the test results of Charpy impact tests at different temperatures from 20 ℃ to-60 ℃,the absorbed energies and fracture shear area at-60℃ are about 200J and 100% respectively,which is very exciting and interesting.In order to clarify the strengthening mechanism and effect of X120 strip further,microstructure has been observed through metallography.Analysis of the metallography revealedthat the microstructure was composed of lower bainitewith a size of 1um and fine M/A components.The X120 strip was formed into 1420 mm diameter spiral welded pipe in Huabei pipe mill.Tested results showed that ultra-high strength and high toughness linepipe could be achieved through reasonable alloy composition design and optimized rolling processes.
