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PHYSICAL SIMULATION OF INTERFACIAL CONDITIONS IN HOT FORMING OF STEELS

Y. H. Li , M. Krzyzanowski , J. H. Beynon and C. M. Sellars IMMPETUS( Institute for Microstructural and Mechanical Process Engineering: The University of Sheffield , Sheffield SI 3JD , UK)

金属学报(英文版)

In the last few years,substantial experimental simulation and mumerical modelling hare been carried out in IMMPETUS to characterise the interfacial heat transfer and friction conditions during hot forging and rolling of steels. Emphasis has been placed on the influence of the oxide scale which forms on the steel workpiece. In the present paper, the experimental methods used for investigating interfacial heat transfer and friction conditions are described. Theses include hot flat rolling of steel slabs and hot axi- symmetric forging of steel cylinders and rings.Temperature measurements and computations demon- strate that for similar conditions, similar conditions, the effective interfacial heat transfer coefficients (IHTC) derived for hot rolling are significantly higher than those for forging, mainly due to the contribution of scale cracking during rolling. On the basis of experimental observations and numerical analysis,physical models for interfacial heat transfer in forging and rolling have been established. In addition, hot" sandwich" rolling and hot tensile tests with finite element modelling have been carried out to evaluate the hot ductility of the oxide scale.The results indicate that the defomation, cracking and decohesion behaviour of the oxide scale depend on deformation temperature, strain and relative strengths of the scale layer and scale - steel interface.Finaly, friction results from hot ring compression tests and from hot rolling with forward/backward slip measurements are reported.

关键词: interfacial heat transfer , null , null , null , null , null

Effect of Oxide Scale on Interfacial Heat Transfer during Slab Hot Rolling

钢铁研究学报(英文版)

关键词:

铝合金挤压铸造过程界面的传热行为

李俊文 , 赵海东 , 吴朝忠 , 李元元

中国有色金属学报

通过测量挤压铸造过程的温度变化，采用基于非线性估算法的热传导有限元反算模型，求解不同挤压力下的界面传热系数(IHTC)。利用铸件中心模拟温度与测量温度验证模型的准确性；结合铸件表面和中心测温点温度变化讨论重力条件和挤压力条件下界面传热系数的变化规律，发现挤压力有效地增加了界面传热系数的峰值和稳定值。探讨挤压力对界面气隙的影响，对于ZL101A铝合金直接挤压铸造过程，50 MPa挤压力具有较好的挤压效果。

关键词: 铝合金 , 挤压铸造 , 界面传热 , 反算法 , 界面气隙