Dongli SONG
,
Jianfeng GU
,
Jiansheng PAN
,
Xin YAO
材料科学技术（英文）
For large-sized AISI P20 steel block used as plastic die with a thickness of more than 200~mm, appropriate quenching processes are the key to obtain much thick hardened layer. In this paper, different quenching processes of AISI P20 steel block such as oil quenching, direct water quenching, water quenching with pre-cooling and water quenching with pre-cooling and self-tempering were numerically investigated by computer simulation based on the detailed discussion on the mathematical models of quenching processes including partial differential equations of heat transfer, thermal physical properties, latent heat, heat transfer coefficient and calculation of phase transformation, The results show that the water quenching with pre-cooling and self-tempering process can not only effectively avoid quenching cracks, but also obtain deeper harden depth than oil quenching.
关键词:
Computer simulation
,
null
,
null
,
null
Yunbo XU
,
Yongmei YU
,
Xianghua LIU
,
Guodong WANG
材料科学技术（英文）
On the basis of transformation kinetics and thermodynamics, the austenite-ferrite transformation start temperature during deformation was predicted for several grades of low-carbon steels under different processing conditions. Results indicate that Ar3d temperature mostly depended on alloying composition and processing parameters. Ar3d increased as strain rate or strain increased for the same steel grade. In view of enhancement of deformation on transformation, the basic kinetics model was established to simulate deformation induced transformation behavior, using which the influence of the deformation stored energy and effective deformation ledge on the nucleation and growth can be considered. The simulated results are in good agreement with experiment results.
关键词:
Computer simulation
,
null
,
null
,
null
Tie GANG
,
Weizhi ZHANG
,
Liwei GUO
材料科学技术（英文）
The convenient and useful raying mode was selected to develop the analysis module of ultrasonic parameters, and the simulation of ultrasonic propagation in typical plane structure was carried out. Using this model, the ultrasonic propagation in the water immersion testing was analyzed. For the complex plate structure, the intelligent analysis and simulation module was developed.
关键词:
Ultrasonic testing
,
null
,
null
Mufu YAN
,
Qingchang MENG
,
Jihong YAN
材料科学技术（英文）
Two materials, pure Fe and pure Al, were nitrided in a pulse plasma nitriding facility. The nitrogen profiles in surface layers and the surface phase structures of specimens nitrided at 500℃ for 8 h for Fe and for 6 h for Al were measured using the glow discharge spectrometry and an X-ray diffractometer, respectively. XRD results indicate that the compound layer with hcp crystal structure (AlN) was formed on the top of Al substrate. During nitriding of Fe, the compound layer growth conforms to parabolic law and the surface nitrogen concentration change little with increasing the nitriding time. The surface nitrogen content of nitrided Al specimens is less than theoretical value 34.17 wt pct of AlN. The mathematical models of nitrogen concentration profiles in the surface layer of nitrided Al specimen have been established based on the research of the kinetics of pulse plasma nitriding of Fe and the nitrogen concentration profiles were also simulated. Results show that the predicted curves agree basically with the experimental data.
关键词:
Pulse plasma nitriding
,
null
,
null
