Study On Low Temperature Performance Of New Type Of Low Temperature B Grade Steel For Bolster And Side Frame

In high latitude and cold countries and regions, railway wagon and parts requirements are higher, Bolster and side frame is one of the components of railway locomotive bogie. It not only relates to the performance of the bogie, but also has important influence on the safety of railway locomotive. So the low temperature performance of the bolster and the side frame is particularly important. the research group has developed a new type of low temperature B grade steel for the manufacture of the bolster and side frame, but its applicability is not know. In this paper, by ductile brittle transform temperature test, low temperature toughness fracture test, microscopic fracture surface observation, etc, study the effects of low temperature on the new low-temperature grade B steel and the existing railway wagon bolster and side frame with steel(grade B+ steel and 20??? steel), determination of the applicability of low temperature B grade steel.Via ductile brittle transform temperature examination tested low temperature impact load of three kinds of steel. Through the experiment, we can find low grade B steel ductile brittle transform temperature is-37 ?; grade B+ steel ductile brittle transform temperature is-32 ?, 20??? steel's ductile brittle transform temperature is-23 ?. When the temperature dropped to-60 ?, the impact absorption energy of low temperature grade B steel is 20 J, the impact absorbed energy of grade B+ steel and 20 steel are only 13 J ? 4 J. The experiments show that in low-temperature impact performance, low grade B steel is best; the low temperature grade B steel is better fulfill the requirement of the railway wagon than others in low temperature condition. Through low temperature toughness test, analysis of test data and fracture surface, we can know that with the decrease of temperature, the plane strain fracture toughness of the three kinds of steel are decreased. The decline trend of low grade B steel and grade B+ steel is consistent, 20??? steel decreased faster. The fracture morphology of the three kinds of steels were observed, first, appear the ductile fracture morphology; second, appear ductile brittle mixed fracture morphology; last, appear completely brittle fracture morphology. The fracture morphology changes of low grade B steel is the slowest, the change rate of grade B+ steel is second one, 20??? steel is faster. The ratio of the ductile fracture morphology and the brittle fracture surface has reached 1:1 of-23 ?, while the low temperature grade B steel and B+ grade steel reach this ratio of-40 ?. When the temperature drop to-60 ?, low temperature grade B steel?grade B+ steel, 20??? steel's plane strain fracture toughness were 27 MPa/m1/2, 28 MPa/m1/2, 24 MPa/m1/2.In a word, the low temperature performance of the new low temperature B grade steel is better, it is suitable to be used as the steel of the bolster and the side in high latitude and cold countries.