过火处理对Q345H型钢组织及力学性能的影响

发布时间：2018-06-04 14:12

  本文选题：H型钢 + Q345　； 参考：《山东大学》2017年硕士论文

【摘要】：热轧H型钢是一种具有高效节约、良好的综合力学性能、截面设计合理的金属材料,在建筑领域用途较为广泛。但其抗火性能较差,当建筑物遭受火灾时,不仅室内存放物品会遭到破坏,而且建筑物本身尤其是建筑物的钢结构也会遭到不同程度的损坏。目前,针对高层建筑钢结构抗火性能研究多集中于钢结构的高温力学性能变化情况,而对于火灾后钢结构存在的隐患研究甚少。本课题针对这一研究现状,对建筑领域中常用的Q345B、精炼Q345B和Q345E三种热轧H型钢材进行模拟火灾实验,探究其遭受不同条件的火灾后微观组织和力学性能的变化情况,找出建筑物遭受火灾后未发生坍塌钢结构存在的安全隐患,为高层建筑火灾后未坍塌钢结构危险评估和新型耐火钢材开发提供理论支持。本课题利用实验室方法模拟火灾现场,设置过火温度为650℃、700℃、750℃、800℃、850℃、900℃、950℃条件下保温1小时和2小时共14组热处理实验,对Q345B、精炼Q345B和Q345E三种试验材料分别进行不同方式的过火处理。通过金相实验,观察过火处理前后材料微观组织的变化;通过硬度实验探究试验材料过火处理前后表面与心部硬度变化情况;通过室温拉伸实验探究实验材料屈服强度和抗拉强度等力学性能变化情况。利用统计方法,分析试验材料在不同过火条件下微观组织中晶粒度、带状组织和魏氏组织等级变化情况;借助MATLAB等工具分析试验材料在过火前后组织组成变化情况。根据试验材料遭受过火前后微观组织和力学性能变化情况,分析试验材料在过火前后力学性能变化与材料微观组织变化之间的关系。分析实验结果可知,三种钢材均在过火温度达到750℃及以上时出现较明显的脱碳现象,并伴有微观组织和力学性能突变,试验材料心部力学性能优于材料外部,高强度的精炼Q345B火灾后力学性能降低最多,灾后潜在危害最大,Q345B次之,Q345E强度硬度降低相对最少。此外,三种材料抗火性能强弱不仅与其抗火结构设计有关,还与材料原始成分和控轧控冷方式等有关,Q345E因含有Nb、Ti、V、B等微合金元素抗火性较好,精炼Q345B因热轧过程中产生部分魏氏组织,材料抗火性最差,Q345B介于两者之间。综上所述,火灾后钢结构力学性能变化是由钢结构微观组织和成分发生了变化,但火灾过程中引起微观组织变化的因素多为钢结构与火源接触面积、过火温度和过火时长等。
[Abstract]:Hot rolled H-section steel is a kind of metal material with high efficiency and saving, good comprehensive mechanical properties and reasonable section design, which is widely used in the field of construction. But its fire resistance is poor, when the building is under fire, not only the indoor storage items will be damaged, but also the building itself, especially the steel structure of the building, will also be damaged to varying degrees. At present, the research on the fire resistance of steel structures in high-rise buildings is mainly focused on the change of high temperature mechanical properties of steel structures, but there is little research on the hidden dangers of steel structures after fire. In view of the present situation of this research, the fire simulation experiments were carried out on three kinds of hot rolled H-section steel, Q345B, refined Q345B and Q345E, which were commonly used in the field of construction, and the changes of microstructure and mechanical properties after the fire were investigated. To find out the hidden danger of the steel structure without collapse after the fire, and to provide theoretical support for the risk assessment of the steel structure without collapse after the fire and the development of new refractory steel. In this paper, the fire site was simulated by laboratory method, and 14 groups of heat treatment experiments were carried out under the conditions of 650 鈩，

本文编号：1977656