Research On Low Temperature Steel For Bolster And Side Frame

With the continuous growth of economy, the railway transportation andrelated business have got rapid development. In the meantime of meetingdomestic demand, the partial products and related parts have entered theinternational market. In recent years, the exports of railway freight and relatedparts continue increasing. But for the high latitude as Russian, where wintertemperature is low, the requirement of low temperature properties of railwayfreight parts is high, in order to meet the demand of export, based on Grade BSteel, this paper develops a new type of low temperature resistant casting steelapplied to bolsters and side frames for low temperature resistant.On the basis of Grade B Steel, the design is made to improve the lowtemperature toughness which is the main target to develop this new type of lowtemperature resistant casting steel. The optical microscope, scanning electronmicroscopic analysis, tensile test, impact test, hardness test are used to furtherstudy the Ni, C, Si, Mn and impurity elements and heat treatment onmicrostructure and mechanical properties of steel. Experimental results show thatwhen Ni content increases from0%to0.30%, the strength of casting steelincreases slightly, the plastic and low temperature toughness improve obviously,the impact absorption work increases from12J to20J at temperature of-60℃.With C content increasing, the pearlite content increases, the strength of castingsteel significantly increases, the plastic decreases significantly. With Si contentincreasing, the strength of casting steel increases, the plastic and lowtemperature toughness first increase then decrease. When Si content is0.30%,-60℃impact absorption work reaches the peak of20J. When the Mn content isless than1.20%, with Mn content increasing, the strength of casting steelimproves slightly, the plastic changes little and low temperature toughnessincreases, when Mn content is higher than1.20%,with Mn content increasing, the strength of casting steel improves obviously, the plastic and low temperaturetoughness decrease, when Mn content is1.20%,-60℃impact absorption workreached the peak20J. The Impurity element of P and S content increases, thevarious mechanical properties of casting steel reduce, especially the lowtemperature toughness that drops significantly. Secondary normalizing processcan refine the microstructure of steel casting, which improves the lowtemperature toughness.The test finally determines that the composition range of the new lowtemperature resistant casting steel for bolster and side frame is that: the C contentis0.20%~0.24%, the Si content is0.30%~0.50%, the Mn content is1.20%~1.50%, the Ni content is0.15%~0.30%, the P content is0.020%or less, Scontent is0.020%or less. The heat treatment process is normalizing and thetemperature is910℃.