Effects of Rare Earth elements on microstructure evolution and mechanical properties of 718H pre-hardened mold steel
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2020年第15期
论文作者：Hanghang Liu Paixian Fu Hongwei Liu Yanfei Cao Chen Sun Ningyu Du Dianzhong Li
文章页码：245 - 256
摘 要：718 H Pre-ha rdened mold steels with diffe rent Rare Earth（RE） contents were prepared to investigate the influence of RE on microstructure evolution and mechanical properties through a series of experiments and theoretical analysis.The results indicated that the toal oxygen（T.O） content decreased from 15 ppm to 6 ppm with 0.022 wt% RE addition,which is attributed to the active chemical properties of RE elements.For test steels,RE additions of 0.012 wt% and 0.022 wt% were significantly effective for refining inclusions by eliminating 11.5% large-sized inclusions with diameter exceeding 10 μm compared with that of ORE steel.RE addition contributed to modify irregular MnS and Al2 O3 inclusions into ellipsoidal RE-inclusions（RE2 O,RES,RE2 O2 S and REAlO3）.The purification of molten steel and the modification of inclusions by RE treatment have significant effects on improvement of the fatigue crack growth tests（FCG） inhibition ability and impact energy as well as the isotropy.However,excessive addition of RE elements（0.07 wt%）seriously reduced the impact energy,ultimate tensile strength and FCG inhibition ability due to rapidly increase of the volume fraction of large-sized inclusions.In addition to the inclusions formed by RE treatment,trace solid solution RE atoms improve the stability of undercooled austenite,resulting in the transformation region of bainite and perlite of 0.07 RE steel shifting to the bottom right and prolonging the incubation period compared with that of ORE steel.
Hanghang Liu1,2，Paixian Fu1,2，Hongwei Liu1,2，Yanfei Cao1,2，Chen Sun1,3,2，Ningyu Du1,3,2，Dianzhong Li1,2
1. Shenyang National Laboratory for Materials Science2. Institute of Metal Research, Chinese Academy of Sciences3. School of Materials Science and Engineering, University of Science and Technology of China
摘 要：718 H Pre-ha rdened mold steels with diffe rent Rare Earth（RE） contents were prepared to investigate the influence of RE on microstructure evolution and mechanical properties through a series of experiments and theoretical analysis.The results indicated that the toal oxygen（T.O） content decreased from 15 ppm to 6 ppm with 0.022 wt% RE addition,which is attributed to the active chemical properties of RE elements.For test steels,RE additions of 0.012 wt% and 0.022 wt% were significantly effective for refining inclusions by eliminating 11.5% large-sized inclusions with diameter exceeding 10 μm compared with that of ORE steel.RE addition contributed to modify irregular MnS and Al2 O3 inclusions into ellipsoidal RE-inclusions（RE2 O,RES,RE2 O2 S and REAlO3）.The purification of molten steel and the modification of inclusions by RE treatment have significant effects on improvement of the fatigue crack growth tests（FCG） inhibition ability and impact energy as well as the isotropy.However,excessive addition of RE elements（0.07 wt%）seriously reduced the impact energy,ultimate tensile strength and FCG inhibition ability due to rapidly increase of the volume fraction of large-sized inclusions.In addition to the inclusions formed by RE treatment,trace solid solution RE atoms improve the stability of undercooled austenite,resulting in the transformation region of bainite and perlite of 0.07 RE steel shifting to the bottom right and prolonging the incubation period compared with that of ORE steel.
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