论文部分内容阅读
采用水平连续铸造工艺制备了矩形截面120 mm×100 mm灰铁型材,对比研究了不同温度奥氏体化对正火组织与性能的影响。结果表明,该灰铁型材表层10 mm处为D型石墨,1/2R为E型石墨,心部为A型石墨,基体中的珠光体分别为5%,15%和15%。880、900和920℃分别保温2 h后出炉空冷的正火组织,表层10 mm处珠光体含量均接近80%;1/2R处的珠光体含量分别为40%、50%和60%;心部的珠光体含量分别为30%、40%和50%。铸态表层硬度为92 HRB,1/2R处和心部硬度低于表层,硬度差为6.4 HRB,正火热处理能够提高灰铁型材心部力学性能,降低不同部位的硬度差和拉伸强度差。正火温度越高,越有利于石墨片附近获得高碳奥氏体,有利于珠光体的形成,有利于灰铁型材断面组织与性能均匀性的提高。920℃×2 h正火,表层的拉伸强度超过350 MPa,断面性能均匀性得到提高,表层和心部的拉伸强度差仅为30 MPa。
The horizontal continuous casting process was used to prepare gray iron profiles with a rectangular cross section of 120 mm × 100 mm. The effects of different austenitizing temperatures on the microstructure and properties were investigated. The results show that the surface of the gray iron profile is D-type graphite at 10 mm surface, ½R is E-type graphite and the heart is A-type graphite. The pearlite in the matrix is 5%, 15% and 15% respectively. After cooling at 880, 900 and 920 ℃ for 2 h, the air-cooled normalized microstructure was obtained. The pearlite content at 10 mm of the surface layer was close to 80%. The pearlite content at 1 / 2R was 40%, 50% and 60%, respectively. Ministry of the pearlite content were 30%, 40% and 50%. The as-cast surface hardness is 92 HRB, the hardness at 1 / 2R and the core is lower than the surface, and the hardness difference is 6.4 HRB. Normalizing heat treatment can improve the core mechanical properties of gray iron profiles and reduce the difference of hardness and tensile strength in different parts . The higher the normalizing temperature, the more conducive to get high-carbon austenite near the graphite sheet is conducive to the formation of pearlite is conducive to gray iron section structure and performance uniformity. 920 ℃ × 2 h normalizing, the tensile strength of the surface layer exceeds 350 MPa, the uniformity of the cross section performance is improved, and the difference of tensile strength between the surface and the core is only 30 MPa.