预硬型718塑料模具钢大模块的组织性能

Microstructure and mechanical properties of large-sized pre-hardened plastic die steel 718

采用洛氏硬度计、拉伸、冲击以及OM、SEM和TEM等方法,对截面尺寸为695 mm×1360 mm的预硬型大截面718塑料模具钢的组织和力学性能进行研究。结果表明:模块边部组织是回火索氏体组织,1/4处是回火贝氏体和少量上贝氏体的混合组织,在心部发现有细片层状珠光体;试验钢截面硬度比较均匀,头部最大截面硬度差为2.9 HRC,尾部最大截面硬度差为2.3HRC;边部的冲击韧性最高,1/4处由于组织偏析致使冲击韧性值出现较大波动,心部的珠光体组织使冲击韧性急剧恶化。讨论了大模块预硬化塑料模具钢不同组织类型的形成原因及其对力学性能的影响。

The microstructure and mechanical properties of pre-hardened 718 plastic die steel with a cross-section size of 695 mm × 1360 mm were studied by rockwell hardness test,tensile test,impact test,OM,SEM and TEM. The results show that the microstructure of the 718 bloom is tempered sorbite at the edge,mixed microstructure of tempered bainite and upper bainite at 1/4 position,fine lamellar pearlite at the core. The hardness of the experimental steel is uniform relatively,the maximum hardness difference of the head cross-section is 2. 9 HRC,the tail is 2. 3 HRC. The edge has the highest impact toughness,the larger deviation of impact toughness is resulted by microstructure segregation at 1/4 position,and the pearlite microstructure makes the impact properties decrease seriously at the core. The reason for the formation of different microstructure and the influence for mechanical properties of different microstructure are disscussed.