| Over 60%of the world's steel production is used in the atmosphere.Atmospheric corrosion accounts for about half of all metal corrosion losses,resulting in huge economic losses.Scientists in Europe and the United States found that Cu can improve the corrosion resistance of steel in twentieth century and the weathering steels began to be noticed and widely developed.Under the trend of high-speed heavy-load in the railway industry,the strength requirements of weathering steel are getting higher and higher.It is especially important that the weathering steel further improves the strength while improving the corrosion resistance.In this paper,high-strength weathering steel alloy composition design,continuous cooling of the austenite phase transition research,laboratory rolling process,and corrosion resistance under different environments,the main findings are as follows:(1)The design of chemical composition of high-strength weathering steel Q500NH,Q550NQR1 based on low C,low P,S,adding in Cu,Cr,Ni corrosion-resistant elements,combined with Nb,Ti microalloying.The Formastor-F ? dilatometer and DIL805 dilatometer were used to measure the critical transformation point of high-strength weathering steel Q550NQR1 under undeformed and deformed conditions and the static CCT and dynamic CCT curves were drawn.The results show:weathering steel Q550NQR1 in the deformation conditions are more prone to ferrite,pearlite transformation,the deformation causes the whole CCT curve to move to the upper left;Undeformed conditions make it easier to obtain martensite and full bainite.(2)Conducting rolling experiment by ?450 hot rolling mill in the laboratory for high-strength weathering steel Q500NH,Q550NQR1 to determine the reasonable rolling process parameters,the results show:the rolling process controlled in two stages,the second start rolling temperature is 850?880?,water cooling after rolling,the final cooling temperature of Q500NH is 590-650?,and the final cooling temperature of Q550NQR1 is 580?630?.(3)Through the ZQFS-12000Z cycle infiltration corrosion test chamber,the use of NaHSO3 solution simulated weathering steel accelerated corrosion in the industrial atmosphere.The results of corrosion test show that:the relative corrosion rates of high-strength weathering steels Q500NH and Q550NQR1 during accelerated corrosion for 72h were 44.5%and 40.1%,respectively,and they were less than 55%which met the standard requirements.The content of ?-FeOOH in weathering steels was high,and the grains of corrosion products were small and dense.(4)The NaCl solution was used to simulate the accelerated corrosion behavior of weathering steels in the marine atmospheric environment.The corrosion results show that:the relative corrosion rate of weathering steels in the marine atmosphere is slightly higher than that in industrial atmospheres.The corrosion rate curve of the experimental steel is divided into three stages.The first stage is the corrosion acceleration stage,the second stage is the corrosion mitigation stage,and the third stage is the corrosion stabilization stage.The distribution of elements in the rust layer shows the local enrichment of corrosion-resistant elements under a certain corrosion time.The content of ?-FeOOH in weathering steels was high.(5)The industrial trial production of high-strength weathering steel Q500NH and Q550NQR1 was carried out in 1780 hot rolling production line.The tensile test,impact test,180° bending test and periodic infiltration corrosion test on the trial production of weathering steel are carried out.The industrial trial production of weathering steel has good mechanical properties.Q500NH atmospheric corrosion resistance index I was 6.37.Q550NQR1 relative corrosion rate was 39.3%.The corrosion performance meets the standard requirements.And now high-strength weathering steel Q500NH,Q550NQR1 industrial mass production was achieved. |
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