准220mm大直径高强度灰铁型材组织与性能研究

Microstructure and Properties of High Strength HCC Gray Iron Bars with Large Diameter of 220 mm

采用水平连续铸造工艺并加入Ti与Sb微合金化，制备了Ф220mm大直径高强度灰铁型材，分析了该型材不同部位的组织与性能。结果表明，该灰铁型材以D型石墨为主，心部有少量A型或E型石墨，基体为铁素体和珠光体混合型，表层珠光体含量接近40％、1／2R处珠光体含量接近80％、心部珠光体85％-95％。水平连铸过程高的冷却速度、微合金化、良好的补缩是获得无缺陷、高强度、高共晶团数量灰铁型材的基础。拉伸性能指标高于HT/LZ350牌号水平，断面均匀性好，硬度差小于10HRB。耐压气密性与其强度指标密切相关。耐压气密性试样爆破前均未发现点渗和周渗现象。爆破强度均在50MPa以上。

The high strength gray iron bars with the large diameter of 220 mm were prepared by horizontal continuous casting （HCC） process and adding the microalloying elements of Ti and Sb, and the microstructures and properties of HCC gray iron bars in different parts of cross section were investigated. The results show that the HCC gray iron bars are mainly with D-type graphite, little content A-type and E-type graphite in the center. It is ferrite and pearlite mixture matrix, the pearlite content is nearly 40% close to the surface of bars, and almost 80% in the half of radius, and 85%~95% in the center of bars. In HCC processing, high cooling speed, microalloying and good feeding are the base to obtain high strength gray iron bars with high number of eutectic cells and without defects. The tensile properties are higher than the standard brand level of HT/LZ350, there are good cross section uniformity microstructures, and the hardness difference is less than 10 HRB. The hydraulic pressure tightness is closely related to the strength of HCC gray iron bars, and the point seepage and circuit seenane has not been found before bursting, and all the bursting strength of the samples is over 50 MPa.