论文部分内容阅读
基于国内某厂二冷区温度波动的实际生产工艺,利用Gleeble-3500热模拟试验机对温度波动下的Nb-Ti微合金钢进行拉伸测试。采用扫描电镜、光学显微镜对试样断口形貌及组织进行观察。结果表明:随温度波动幅度(ΔT)增大,铸坯脆性区右移。ΔT每升高25K,脆性区温度提高50 K左右。低温时,铸坯塑性几乎不随温度波动幅度变化而变化。随拉伸温度降低,试样断口由穿晶断裂开始向沿晶断裂转变。基体及韧窝底部存在夹杂物或第二相粒子,为空穴形核提供条件,成为恶化铸坯塑性的重要因素。随温度下降,铁素体逐渐形成。在相同测试温度下,温度波动越大对铁素体含量的影响更加明显。铁素体体积分数为36%时,该钢的热塑性达到最低值。
Based on the actual production process of the temperature fluctuation in the second cooling zone of a domestic factory, the tensile testing of the Nb-Ti microalloyed steel under the temperature fluctuation was conducted by using the Gleeble-3500 thermal simulation testing machine. Scanning electron microscopy and optical microscopy were used to observe the fracture morphology and microstructure of the specimen. The results show that the brittle zone of cast slab shifts to the right as the temperature fluctuation (ΔT) increases. ΔT increased by 25K, brittle zone temperature increased by about 50K. When the temperature is low, the slab plasticity almost does not change with the temperature fluctuation. With the decrease of the stretching temperature, the fracture of specimen begins to transform from intergranular fracture to transgranular fracture. There are inclusions or second-phase particles in the bottom of the matrix and dimple, which provide conditions for nucleation of the holes and become an important factor for deteriorating the plasticity of the slab. With the temperature drop, ferrite gradually formed. In the same test temperature, the greater the temperature fluctuations on the ferrite content more obvious. When the ferrite volume fraction is 36%, the thermoplasticity of the steel reaches a minimum value.