铸态高强度高韧塑性球墨铸铁的工艺研究
发布时间：2019-03-18 18:19
【摘要】：球墨铸铁作为重要的金属结构材料具有优良的机械性能,一定程度上可与钢媲美,且比钢成本低廉,因此在轨道交通制造、船舶重工、风电装备等领域应用较为广泛。由于上述领域的各类设备大部分工作环境恶劣,有些需要在寒冷或者腐蚀严重的条件下经受频繁的外力冲击,这就对球墨铸铁的韧性和强度同时提出了更高的要求。以牌号QT400-18为代表的高强度高韧性球墨铸铁因其在强度和韧性平衡方面的优越性,成为众多船用柴油机的机体和缸盖等关键铸件的材质选择,在实际生产中,大部分企业都依靠Si或者合金元素的固溶强化+高温石墨化退火实现球墨铸铁铸件兼具强度和韧性。本课题是由作者所在单位中车大连机车车辆有限公司铸锻分公司与大连理工大学合作进行的实践型课题。中车大连机车车辆有限公司铸锻分公司生产的某中大型柴油机机体材质为QT400-18A,技术要求为抗拉强度Rm≥390MPa,屈服强度Rp0.2≥250MPa,伸长率A≥15%,布氏硬度140-180HBW,常温下冲击功平均值≥14J,单值≥11J。如果按照一般硅固溶强化+高温退火的工艺方案生产,工艺流程长,退火时高温下形成的氧化皮会使铸件抛丸清理的时间成倍增加,造成人力和能源的浪费。为了缩短生产周期,节约成本,本课题通过重新选择试块位置和控制铁液的化学成分(特别是Si和Cu的含量)得到铸态下铸件及其附铸试块均满足其力学性能和金相组织的所有要求。本课题在P6型柴油机机体的生产过程中实施,采用两台5t中频感应电炉联合熔化,选用本溪高纯生铁和优质碳素结构钢为主要炉料,通过夹层覆盖冲入法球化处理和多次孕育方式结合多次孕育技术,得到了铸态组织为铁素体+少量珠光体+球状石墨+极少量硬化相的QT400-18高强度高韧性球墨铸铁机体。在此基础上分别试验了三种不同位置的附铸试块的力学性能和金相组织,通过对比分析,发现在铸件端面平台处的位置①(铸型的下表面)冷却条件与铸件一致,且内部组织致密,无疏松和夹渣缺陷,各项性能指标稳定。继而采用该试块位置,又分别研究了不同硅含量(Si1.8%,2.0%,2.2%,2.6%)和不同铜含量(Cu0.05%,0.10%,0.16%,0.25%)对附铸试块性能和组织的影响。试验表明,当硅含量为1.8%时其铁素体含量最低,强度和硬度最低,而23。C时冲击值最高；当铜含量为0.25%时其珠光体含量最高,强度和硬度也最高,而23℃时冲击值最低。依据该结果,将1.8%Si+0.2%Cu的方案应用于P6型柴油机机体的批量生产,铸件合格,经济效益显著。位置①的6个试块铸态下珠光体含量在2%-10%,抗拉强度390MPa-410 MPa,屈服强度253MPa-266 MPa,伸长率20%-28%,布氏硬度140-150HBW,常温下冲击功平均值14J-16J,符合技术要求。
[Abstract]:As an important metal structure material, ductile iron has excellent mechanical properties, which is comparable to steel to a certain extent, and its cost is lower than that of steel. Therefore, it is widely used in the fields of rail transit manufacturing, ship heavy industry, wind power equipment and so on. Because most of the equipments in these fields have bad working conditions, some of them need to withstand frequent external force impact under cold or severe corrosion conditions, which requires higher toughness and strength of nodular cast iron at the same time. Because of its superiority in strength and toughness balance, high strength and high toughness ductile iron represented by brand QT400-18 has become the material choice of many key castings such as block and cylinder head of marine diesel engine. Most enterprises rely on solution strengthening and high temperature graphitization annealing of Si or alloy elements to realize ductile iron castings with both strength and toughness. This paper is a practical project carried out by the casting and forging branch of Dalian Locomotive and Rolling Stock Co., Ltd and Dalian University of Technology. The material of a medium-large diesel engine block produced by the casting and forging Branch of Dalian Locomotive and Rolling Stock Co., Ltd is QT400-18A, technical requirement: tensile strength Rmx390 MPa, yield strength Rp0.2 / 250 MPa, elongation A 鈮，
本文编号：2443109
[Abstract]:As an important metal structure material, ductile iron has excellent mechanical properties, which is comparable to steel to a certain extent, and its cost is lower than that of steel. Therefore, it is widely used in the fields of rail transit manufacturing, ship heavy industry, wind power equipment and so on. Because most of the equipments in these fields have bad working conditions, some of them need to withstand frequent external force impact under cold or severe corrosion conditions, which requires higher toughness and strength of nodular cast iron at the same time. Because of its superiority in strength and toughness balance, high strength and high toughness ductile iron represented by brand QT400-18 has become the material choice of many key castings such as block and cylinder head of marine diesel engine. Most enterprises rely on solution strengthening and high temperature graphitization annealing of Si or alloy elements to realize ductile iron castings with both strength and toughness. This paper is a practical project carried out by the casting and forging branch of Dalian Locomotive and Rolling Stock Co., Ltd and Dalian University of Technology. The material of a medium-large diesel engine block produced by the casting and forging Branch of Dalian Locomotive and Rolling Stock Co., Ltd is QT400-18A, technical requirement: tensile strength Rmx390 MPa, yield strength Rp0.2 / 250 MPa, elongation A 鈮，
本文编号：2443109
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