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The temperature field and cooling rate especially for surface center and corner, which located at 0-5mm under the slab surface were calculated along the casting direction based on the two- dimensional heat transfer and solidification model of slab continuous casting, combined with the actual casting process conditions. The results show that the temperature of slab drops rapidly from liquidus temperature to 1200-900?? in the mold, and then drops slowly in the secondary cooling zone with the corner 200?? about lower than the surface center. As to the cooling rate, for 0-5mm layer under surface, it is up to 40??/s in the mold with the average cooling rate about 10??/s. For the secondary cooling zone, it is about 3-6??/s in the foot zone, and then drops to a steady value about 0. 1-0. 5??/s. The results can be used to optimize the continuous casting process and provide the basis for the control of the surface and corner transverse cracking of continuous casting slabs based on the solidification and phase transformation principles. 相似文献
83.
Dual phase steel has become an important engineering material to be used in structural and automotive applications due to its good combination of strength, ductility, and formability. In this study, hardenability of a low carbon and microalloyed steel was investigated by using the standard Jominy End Quench Test at four different quenching temperatures. Three steel specimens were quenched from the intercritical region at 737°C, 754°C, and 779°C separately, whereas one of them was tested at 900°C, in the fully austenitic region. After finishing the Jominy test, metallographic examination of the samples was carried out to see the variation in the microstructure through the length of the steel. And also, hardness measurements were made through the length of the samples. Results brought out that there was a strong decrease in the hardness of the tested samples after a depth of 5 mm from the quenched end. 相似文献
84.
85.
一种Nb-Ti微合金钢微合金碳氮化物析出行为的研究 总被引:8,自引:1,他引:7
利用热模拟和TEM技术研究了Nb—Ti微合金钢中微合金碳氮化物的析出行为,研究结果表明,高温奥氏体区析出的微合金碳氮化物数量随变形量的增大而增加,尺寸随着变形温度的升高稍有增大。铁素体区析出的微合金碳氮化物尺寸比在形变奥氏体中析出的更为细小,数量随着保温时间的增加而增多,但尺寸变化不大;当温度较低的时候,微合金碳氮化物主要在位错线等晶内缺陷处析出。 相似文献
86.
87.
借助MMS-300热模拟试验机研究了控轧温度区间、终冷温度、贝氏体区等温处理以及冷却路径对微合金化热轧TRIP钢组织演变规律的影响。结果表明,随着控轧温度区间“下调”,组织中的铁素体晶粒越来越细小,铁素体量逐渐增加,残余奥氏体量则先增加后减少。终冷温度升高时,组织中的残余奥氏体量也呈现出先增加后减少的变化趋势,而贝氏体温度范围等温时间的延长使残余奥氏体量增加。相对于“缓冷+快冷”,轧后采用“快冷+缓冷+超快冷”冷却路径更有助于铁素体晶粒的细化和奥氏体的残留。在“快冷+缓冷+超快冷”冷却路径下,当控轧温度区间为900~840℃,缓冷温度范围为710~680℃,贝氏体等温处理制度为450℃×5min时,组织中的残余奥氏体量达到最高值113%。 相似文献
88.
89.
This article describes a thermo‐mechanical‐microstructural model for deformation of niobium microalloyed steel in the two‐phase range of temperatures. Results of physical and numerical modeling are presented. The physical simulation experiments include plastometric and dilatometric tests, as well as industrial rolling trial. Plastometric tests were performed to describe the flow stress for the wide range of temperatures, including ferritic, two‐phase, and austenitic states. Two‐stage deformation tests were performed to identify the microstructure evolution model. Dilatometric tests were used to identify the model of phase transformation. A model of the kinetics of the precipitation was adapted from the literature. The coefficients in all the models were identified using inverse analysis. Developed models were implemented in the finite element code. In order to improve the accuracy of the flow stress predictions in the two‐phase phase temperature range, internal variable dislocation density model was included, as well. The proposed combination of models correctly predicted microstructure changes and mechanical properties in the two‐phase range, during the transformations of the thermo‐mechanical treatment. Industrial trials were performed for the final validation of the models. 相似文献
90.