【作者】 李响；

【导师】 沈明钢；

【作者基本信息】 辽宁科技大学 ， 冶金工程， 2021， 硕士

【摘要】 目前我国用于制造煤炭采运装备的耐磨钢板比较单一,未进行合理的区分,从而导致相同的耐磨钢板在不同的煤炭采运工况出现寿命差异较大的局面,造成巨大的经济损失。高钛耐磨钢的应用前景广阔,但是大量频发的表面质量缺陷严重制约着铸坯的生产,大幅降低了连铸机的生产效率,严重制约着我国在高钛耐磨钢技术领域的拓展。铸坯表面裂纹的普遍性与多发性,可导致漏钢事故发生,影响连铸机的生产顺行。对这种高钛耐磨钢凝固过程中的析出机理研究不多,因此进行了高钛耐磨钢凝固过程的原位观察。通过实验室制备Ti元素含量0.3～0.7%的耐磨钢,首先在较大的化学成分变化和冷却速率范围内,通过理论计算讨论了含钛析出物Ti N和Ti C在液、固相中析出的可能性以及其生长动力学条件,并提出了一些可控制粗大Ti N析出的措施。然后从钢液凝固组织演变出发,采用高温激光共聚焦原位研究高钛耐磨钢的高温组织演变,研究不同冷却速率、不同化学成分和不同浇注温度下的高钛耐磨钢凝固组织演变行为的影响。论文的主要研究结果可概括如下:（1）通过理论计算研究了高钛耐磨钢凝固过程Ti N和Ti C在液固相析出可能性以及析出生长动力学条件。基于实时平衡分配系数的热力学发现,液相中析出Ti N和Ti C,其析出对应的糊状区固相率（f_S）分别为0.53和0.66。增加w₀[Ti]、w₀[N]将显著提高液相中析出Ti N的开始温度;而增加w₀[C]将导致液相中析出Ti N的温度下降,但固相率（f_S）减小。（2）原位观察发现,低冷却速率下δ相的生长主要受温度和溶质元素扩散速率的影响,增大冷却速率会加剧L/δ界面前沿溶质元素的富集,增大L/δ界面前沿与剩余液相间的溶质浓度梯度。高冷却速率下局部偏析的溶质元素浓度迅速升高与液相溶质分布不均匀是造成L/δ界面形态和迁移行为变化的主要原因。钛含量成分调整并未改变高钛耐磨钢的凝固相变产生的机制。在适量含量范围内,钛含量越高,发生L+δ→γ的驱动力和初始速率越小;此外,增加钛含量导致δ相生成量减少,促使L→γ,δ→γ产生的体积收缩量减小。在本文的讨论范围内浇注温度的改变并未改变高钛耐磨钢凝固相变产生的机制,浇注温度对高钛耐磨钢的凝固过程的影响很小。更多还原

【Abstract】 At present,the wear-resistant steel plate used for manufacturing coal mining equipment in China is relatively single and not reasonably differentiated,which leads to the situation that the same wear-resistant steel plate has a large difference in life in different coal mining working conditions,causing huge economic losses.The application of high titanium wear-resistant steel has a broad prospect,but a large number of frequent surface quality defects seriously restrict the production of cast billets,significantly reduce the production efficiency of continuous casting machines,and seriously restrict the expansion of China in the field of high titanium wear-resistant steel technology.The prevalence and multiplicity of surface cracks on cast billets can lead to steel leakage accidents and affect the smooth production of continuous casting machines.Not much research has be en done on the precipitation mechanism during the solidification of this high-titanium wear-resistant steel,so in-situ observation of the solidification process of high-titanium wear-resistant steel was carried out.By preparing the wear-resistant steel with 0.3-0.7%Ti element content in the laboratory,the possibility of precipitation of titanium-containing precipitates Ti N and Ti C in the liquid and solid phases and their growth kinetic conditions were firstly discussed by theoretical calculations in a wide range of chemical composition changes and cooling rates,and some measures that could control the precipitation of coarse Ti N were proposed.Then,the high-temperature laser confocal in-situ study of the high-titanium wear-resistant steels’high-temperature tissue evolution was carried out from the steel solidification tissue evolution,and the in fluence of the solidification tissue evolution behavior of high-titanium wear-resistant steels at different cooling rates,different chemical compositions an d different pouring temperatures was investigated.The main findings of the paper can be summarized as follows:（1）The solidification process of high-Ti wear-resistant steels with Ti N and Ti C in the liquid-solid phase precipitation possibility and the precipitation growth kinetic conditions were investigated by theoretical calc ulations.The thermodynamics based on the real-time equilibrium partition coefficients found that the solid phase rates in the paste zone corresponding to the precipitation of Ti N and Ti C in the liquid phase were 0.53 and 0.66,respectively.Increasing w₀[Ti]and w₀[N]would significantly increase the starting temperature of Ti N precipitation in the liquid phase;while incre asing w₀[C]would lead to a decrease in the temperature of Ti N precipitation in the liquid phase,but a decrease in the solid phase rate f _S.（2）In-situ observation shows that the growth ofδ-phase at low cooling rate is mainly influenced by the temperature and diffusion rate of solute elements,and increasing the cooling rate will intensify the enrichment of solute elements at the L/δinterface front and increase the solute concentration gradient between the L/δinterface front and the remaining liquid phase.The rapid increase in solute element concentration of local deviations at high cooling rates and the inhomogeneous solute distribution in the liquid phase are the main reasons for the changes in morphology and migration behavior at the L/δinterface.The adjustment of the composition of the titanium content did not change the mechanism of the solidification phase transition generation in the high-titanium wear-resistant steel.In the moderate content range,the higher the titanium content the smaller the driving force and initial rate of L+δ→γoccurring;moreover,increasing the titanium content leads to a decrease inδ-phase generation,prompting a decrease in the volume shrinkage produced by L→γ,δ→γ.In the scope of this paper,the change of pouring temperature does not change the mechanism of solidification phase change generation of high titanium wear-resistant steel,and it can be considered that the pouring temperature has basically no effect on the solidification process of high titanium wear resistant steel.更多还原