| With the rapid development of China's economy,the demand for oil,natural gas is increasing,so as to decrease oil and gas pipeline construction costs,improve the efficiency of oil and gas transportation,research and development can improve the delivery pressure of high grade pipeline steel as steel and the common focus of petroleum,natural gas industry.For research and development has a higher strength,good anti-crack performance,aging resistant strain ability and good welding performance of pipeline steel products offers great prospects for development.Shagang group based on the research of ultra high strength pipeline steel X100 and X120 measures how development project as the background,through the thermal simulation experiment and hot rolling experiments,research the X100 pipeline steel under different composition and process organization change rule.On this basis,the high Nb alloy system of X100 pipeline steel industrial trial production.Using performance of steel plate for comprehensive evaluation of industrial production,mainly studied the strain aging properties and the performance after the welding thermal simulation.In this paper,the focus of the work and its results are as follows:(1)0.04%Nb steel CCT curve shows that with the increase of cooling speed,change the start and final cooling temperature is gradually reduced,the organization form of low temperature stage,in turn,as the PF,AF,GB and BF.0.07%Nb steel CCT curve shows that with the increase of cooling speed,change the start and final cooling temperature is gradually reduced,the organization form of low temperature stage of AF,GB and LB.CCT curve of boron steel showed that 0.0015%of boron added makes the transition temperature reduced and lead to the transformation of austenite to ferrite delay.In dynamic CCT curve of boron added significantly lower transformation start temperature and expanding the scope of the GB and the transition of the BF to lower cooling rate.In the slow cooling rate to 1?/s,the formation of PF is completely suppressed(2)By studying the influence of Nb,B and V of three microalloy elements on the performance of high-strength pipeline steel structure,the Nb element can be found to promote the formation of cryogenic tissue and improve the strength.The microb element can significantly improve the hardenability of steel and improve the strength obviously,but because of the formation of a large number of granular bainite tissue,the ductility decreases.V elements for state of TMCP steel plate,the strengthening effect is not significant,600?tempering heat preservation after 1 h,strong toughness,good to meet the requirements of the ultra high strength pipeline steel X100.High Nb content of test steel,good toughness,suitable for industrial production.(3)Using B component test steel industrial trial production,adopting TMCP rolling technology,finishing temperature 780?,final cooling temperature 280?,25?/s cooling rate,rolling steel microstructure is mainly composed of granular bainite and a small amount of lath bainite,good comprehensive mechanical properties,and has a certain amount of surplus,meet the standard requirements,its-20? reached 270 J impact resistance,and 40?impact performance reached 250 J.Through the industrial manufacture steel strain aging test,the results showed that the industrial trial production after steel strain aging of stress-strain curve from the arch type to type flow,elongation,yield strength and yield ratio increased significantly,no significant change in impact toughness.The results of welding thermal simulation show that the impact toughness and elongation of the steel plate after welding thermal simulation are reduced,and the strength is not linear change with the change of heat input.When the heat input is 15kJ/cm,the sample tissue is mainly composed of bainite and granular bainite,which is beneficial to the toughness.The comprehensive mechanical properties of industrial test steel,the strain aging performance and welding thermal simulation are good. |
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