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首页> 外文会议>International Conference on Alternative Routes of Iron and Steelmaking ICARISM'99, Sep 15-17, 1997, Perth, WA >Nucleation and Early Growth Pertinent to Near Net Shape Casting
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Nucleation and Early Growth Pertinent to Near Net Shape Casting

机译：与近净形铸造有关的成核和早期生长

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摘要

Twin-roll continuous casting technology is rapidly approaching commercialisation. Fundamentally different than conventional continuous casting, heat transfer and hence solidification during twin-roll casting are governed by the interfacial melt/mould thermal resistance, as opposed to the resistance of the solidifying shell. Under these conditions the interface resistance is predominantly controlled by the melt/substrate wetting behaviour. The very early stages of melt/mould contact are characterised by highly transient heat transfer conditions. The overall melt cooling rates prior to the formation of the first solid are reported to be in the range of 1000 - 50000 K/s with melt undercoolings of up to 300 K. At the points of intimate melt/mould contact the thermal resistance is approaching zero, where cooling rates and undercooling much larger than those reported in the literature are probably occurring. Improved wetting will reduce the energy barrier for nucleation while at the same time increasing the cooling rate of the liquid. Since the overall nucleation rate is controlled both by the rate of cluster formation and the rate of atom transfer to the nucleus, a critical cooling rate will exist above which the nucleation rate is expected to be reduced. Under these conditions, it is possible that the first solid phase to form is a metastable glass which subsequently transforms into a crystalline phase. The implications on nucleation and early growth are also discussed.
机译：双辊连铸技术正在迅速走向商业化。与常规连续铸造的根本不同，在双辊铸造过程中的传热和固化取决于界面熔体/模具的热阻，而不是凝固壳的阻力。在这些条件下，界面电阻主要由熔体/基材的润湿行为控制。熔体/模具接触的最早期阶段的特征是高度瞬态的传热条件。据报道，在形成第一种固体之前，总的熔体冷却速率为1000-50000 K / s，熔体过冷度高达300K。在紧密的熔体/模具接触点，热阻接近零，冷却速度和过冷度可能比文献中报道的大得多。改善的润湿性将减少成核的能垒，同时提高液体的冷却速度。由于总体成核速率受团簇形成速率和原子转移至原子核的速率的控制，因此将存在临界冷却速率，在该速率以上，预期成核速率将降低。在这些条件下，可能形成的第一个固相是亚稳玻璃，其随后转变为结晶相。还讨论了对成核和早期生长的影响。

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