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Xiao Ping Li Joong Kil Park Joo Choi Chang Hee Yim 《Metals and Materials International》1999,5(1):25-32
The hot ductilities of Nb-bearing and Nb-free medium carbon steel have been investigated by the hot tensile tests. A high
carbon steel (0.4%) was also tested as a reference to determine the relationship between transformation temperature and hot
ductility. C and Nb are very effective in delaying the ferrite transformation so that the ductility trough extended to a lower
temperature compared to Nb-free medium carbon steel. Decreasing the strain rate promotes the formation of grain boundary ferrite
films at higher temperatures and, on the low temperature side, the intergranular failure could still occur even when the amount
of ferrite reached 40% or more. The short time temperature oscillation accelerated the precipitation of grain boundary films
at higher temperatures, extending the ductility trough to higher temperatures. The samples tested on different machines (direct
heating and induction heating) exhibited different hot ductility behavior. 相似文献
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V. I. Krutyakova V. A. Ostapenko A. Ya. Maloletnev 《Metal Science and Heat Treatment》1988,30(3):194-198
1. | Ultrasonic strain-hardening of high-strength steel 35KhN2MFA increases its low cycle impact fatigue resistance at the stages of fatigue crack nucleation and propagation. |
2. | The lower the level of cyclic stresses is, the greater is the degree to which the increase of endurance of steel after USSH in impact bending is determined by the decrease of the fatigue crack growth rate. |
3. | Plastic surface deformation of high-strength steel increases considerably the length of the period of slow fatigue crack growth and has practically no effect on the length of the period of accelerated fatigue crack growth. |
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利用Gleeble-2000热模拟试验机研究了不同Ce含量的00Cr17高纯铁素体不锈钢的热变形行为,并利用光学显微镜、扫描电镜和透射电镜对实验钢在不同温度下的显微组织进行了观察和分析.结果表明:在00Cr17高纯铁素体不锈钢中添加稀土Ce完全抑制了900~1050℃的中温脆性区的产生,改善了1350℃以上的高温脆性区内的热塑性.Ce抑制中温脆性区产生的主要原因是Ce抑制了Cr23C6在晶界上的析出,而改善高温脆性区的热塑性是因为Ce减少了硫、磷等低熔点杂质在晶界的富集,抑制了高温时部分晶界优先熔化而造成的开裂. 相似文献
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采用自约束热疲劳试验法,结合SEM、EDS以及Jmat-pro热力学计算软件等研究了碳含量(0.35%和0.71%)变化对4Cr5Mo2V型热作模具钢冷热疲劳性能的影响。结果表明:提高含碳量后,钢中析出大量细小弥散的MC型碳化物,从而使0.71%C钢的抗回火软化性能和热稳定性能均强于0.35%C钢;冷热疲劳循环1000次后,提高碳含量推迟了疲劳裂纹的萌生,当循环次数增加到2000次后,虽然0.71%C钢表面和基体的软化程度均弱于0.35%C钢,但该钢存在较多尺寸较大且呈聚集状态分布的未溶碳化物,这些碳化物在应力的作用下与基体脱离,脱离处成为裂纹扩展的通道,从而促进了疲劳裂纹萌生和扩展。 相似文献
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通过合理取样方法和设计的高温变型实验方案,对A105钢连铸坯热变形过程中发生的变形及最终断裂全过程进行模拟实验,找出该钢种连铸坯在热变形过程中的3个脆性温度转变点,揭示该钢种连铸坯在3个脆性转变区域的热塑性规律以及发生断口后的形貌,对于合理确定连铸工艺冷却制度、拉矫温度等参数,降低裂纹缺陷发生概率有很好的指导意义。 相似文献
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A. A. Gol'denberg A. N. Chekhovoi L. N. Antipova 《Metal Science and Heat Treatment》1989,31(2):129-133
1. | One of the causes of failure during low-cycle fatigue of type 0Kh4V2S2MFNYuT die steel is the formation of defective spaces around the carbide inclusions. This type of damage is evidently associated with the development of stresses at the boundary of the matrix and the inclusion during external cyclic loading. |
2. | The effective radius of the carbide inclusions linearly increases with increase of the logarithm of their sizes. |
3. | During cyclic loading at a frequency of f=1 Hz and c = +2400 to –300 N/mm2 the defective spaces are observed in steel 8Kh4V2S2MFNYuT around particles of size greater than 0.3 m. |
4. | During metallurgical production, one should avoid the accumulation of large carbides in the structure of die steels to be used for cold working. |
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The room-temperature dry sliding wear behavior of AI SI 1045 steel has been investigated with the aim of clarifying the effect
of ductility on wear Sliding wear tests were carried out in the air using a pin-on-disk wear tester with loads ranging from
4 to 12 N The specimen with higher ductility showed a lower wear rate than the specimen with lower ductility though their
hardness values are similar SEM observations of worn surfaces revealed that the wear begins with a microploughmg process,
which was followed by steady surface-platelet formation and its detachment Microscopic observations of the wearing surfaces
as a function of sliding distance clearly proved that higher ductility leads to delayed formation of the wear sheets together
with their delayed detachment, which resulted in lower wear rates. It was found microscopically that ductility, rather than
hardness, is a major controlling factor in determining wear rate when the wear proceeds through surface-platelet formation
and its detachment. 相似文献
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