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采用有限元法编制了计算不锈钢板坯在连铸时凝固过程温度场及坯壳的生长随时间的变化。将计算结果与实测结果进行了比较。得出影响铸坯温度场和凝固末端位置的主要因素是拉速和二冷配水,而过热度影响较小。 相似文献
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连铸二冷区凝固传热及冷却控制 总被引:8,自引:0,他引:8
本文系统论述了连铸二冷区凝固传热方式,冷却制度,制定原则和控制准则。建立了铸坯凝固传热数字模型。采用自行开发的二冷配水计算软件,已在多家生产厂获得成功应用。 相似文献
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提出了基于非调质钢凝固特性的二次冷却控制方法。在凝固特性研究方面,运用高温共聚焦显微镜、场发射扫描电镜研究了冷速对第二相粒子析出规律的影响,并阐释了先共析铁素体的相变机制。结果表明,第二相粒子在1086 ℃开始析出,并在912 ℃达到峰值。当冷速在0.1~5 ℃·s?1时,随着冷速增大,第二相粒子尺寸和数量均减小,且第二相粒子由晶界处的链状分布向晶体内的弥散分布过渡,提高冷速有助于削弱第二相粒子的钉扎作用,强化铸坯表层微观组织;在二冷配水优化方面,建立了考虑铸坯横向水量分布的凝固传热数学模型,提出了基于非调质钢凝固特性的二冷配水优化方案,即对出结晶器后的铸坯实施强冷,以满足控制第二相粒子析出的合理冷速和温度区间的要求。工业试验证实了技术方案的可行性。此外,研究表明,降低喷淋距离有助于改善连铸坯横向冷却不均匀性。本研究统筹考虑二冷水量与喷淋距离对非调质钢裂纹敏感性的影响,通过开展“纵?横”凝固冷却控制研究对连铸二次冷却进行系统优化,提出的二冷优化方案有助于改善连铸坯的表面及皮下裂纹。 相似文献
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Weld solidification structure of three different types of stainless steel,i.e., 310 austenitic, 309 and 304 semiaustenitic, and 430 ferritic, was investigated. Welds of each material were made without
any quenching, with water quenching, and with liquid-tin quenching during welding. The weld micro-structure obtained was explained
with the help of the pseudobinary phase diagrams for Fe-Cr-Ni and Fe-Cr-C systems. It was found that, due to the postsolidification
5 → γ phase transformation in 309 and 304 stainless steels and the rapid homogenization of microsegregation in 430 stainless
steel, their weld solidification structure could not be observed unless quenched from the solidification range with liquid
tin. Moreover, the formation of acicular austenite, and hence, martensite, at the grain boundaries of 430 stainless steel
welds was eliminated completely when quenched with liquid tin. The weld solidification structure of 310 stainless steel, on
the other hand, was essentially unaffected by quenching. Based upon the observations made, the weld microstructure of these
stainless steels was summarized. The effect of cooling rate on the formation of primary austenite in 309 stainless steel welds
was discussed. Finally, a simple method for determining the relationship between the secondary dendrite arm spacing and the
solidification time, based on welding speeds and weld pool configurations, was suggested. 相似文献
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根据武钢第一炼钢厂重轨钢连铸生产条件,建立380 mm ×280 mm方坯凝固传热数学模型,并采用射钉法验证及修正。模拟结果表明,U71Mn和U75V钢的凝固末端各自位于距结晶器液面16.96~21.68 m和16.50~21.17 m;减弱二冷强度或增大拉速,U71Mn和U75V钢凝固终点均会明显后移。根据计算结果,二冷制度由弱冷(0.346 L/kg)改为超弱冷(0.218 L/kg),拉速采用0.7 m/min,应用1~4~#机架轻压下,压下量为5~7 mm,U71Mn和U75V钢凝固终点延长至21 m以上。连铸工艺优化后,重轨钢大方坯中心疏松Ⅰ级内平均合格率由89.64%提高到99.50%。 相似文献
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304不锈钢2mm连铸薄带中的裂纹分布和形成分析 总被引:3,自引:0,他引:3
用扫描电镜(SEM)观察和分析了双辊连铸法生产的304不锈钢1 200 mm×2 mm铸带表面和内部裂纹的形貌和形成。由于采用导热性好的铜制结晶辊,薄带表面和内部产生了长140 mm、深0.33 mm的裂纹,薄带断面有分层现象。试验结果表明,铜制结晶辊使钢液的冷却速度达到(1~4)×103K/s,薄带接触辊面温度低,凝固区的温度梯度高达105K/m,温差产生的内应力和应力集中导致裂纹产生;MnS、MnO、Cr2O3等夹杂物是裂纹源。 相似文献
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In Situ Observation of Solidification Process of AISI 304 Austenitic Stainless Steel 总被引:1,自引:1,他引:0
HUANG Fuxiang WANG Xinhua ZHANG Jiongming JI Chenxi FANG Yuan YU Yan 《钢铁研究学报(英文版)》2008,15(6):78-0
The solidification process of AISI 304 stainless steel during cooling at a rate of 0.05 K/s has been observed in situ using a confocal scanning laser microscope (CSLM). The results show that the 8 phase appeared first in liquid steel, as the temperature decreased, the γ phase precipitated prior at δ-grain boundary at 1452. 2 ℃, the liquid steel disappeared at 1 431.3 ℃, and then the γ phase precipitated on the δ ferrite. Based on the Scheil-Gulliver solidification model, the solidification processes of AISI 304 stainless steel are simulated using the Scheil model in Thermo Calc, and the simulation results agree well with the results observed in the experiment. 相似文献
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根据奥氏体不锈钢的热物理参数和二冷区各区出口目标温度,建立了不锈钢220mm×220 mm铸坯动态二冷综合控制模型和末端拉速电磁搅拌-拉速优化模型。304奥氏体不锈钢连铸生产应用结果表明,在该钢正常工作拉速0.8~1.1 m/min,根据目标温度(足辊1080℃,一区1 070℃,二区1060℃,三区1045℃,进拉矫机980℃)制定相应比水量(0.30~0.33 L/kg),模型实时计算表面温度与目标温度对比,进行在线控制,铸坯温度均匀、稳定,冶金质量良好。 相似文献
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结晶器钢液凝固现象的研究 总被引:2,自引:0,他引:2
本文研究了连铸机在正常工作状态下,钢水含碳量、拉坯速度、结晶器冷却水流速等因素对铸坯凝固的影响,并对凝固壳厚度进行了实测,掌握了厚度计算值与实测值的偏差规律,为制订连铸工艺提供了依据。 相似文献
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通过感应炉熔化的304钢(/%:0.053C、0.55Si、1.50Mn、0.030P、0.002S、17.02Cr、8.01 Ni、0.50Cu、0.08Mo)直接浇铸在水冷铜模上得到厚7 mm直径25 mm的圆形试样,研究了Cr、当量/Ni当量和1.5~1 000℃/s的冷却速率对奥氏体不锈钢铸态凝固组织形态和分布的影响。结果表明,随冷却速率增加至75~90℃/s,该钢的凝固模式由FA(铁素体-奥氏体)模式向AF(奥氏体-铁素体)模式转变,初生相由枝晶铁素体转变成枝晶奥氏体,但冷却为~1 000℃/s时,观察到块状铁素体组织,并且枝晶状奥氏体转变成胞状奥氏体。 相似文献