【作者】 孙涛；

【导师】 王作成；

【作者基本信息】 山东大学 ， 材料加工工程， 2009， 硕士

【摘要】 热轧H型钢根据不同用途合理分配截面尺寸的高宽比,具有优良的力学性能和优越的使用性能。钢结构因重量轻,强度高,抗震性能好,工业化生产、施工速度快,节能环保等优点,在世界范围内得到广泛应用。我国已经充分具备钢结构的发展条件,钢结构建筑呈现蓬勃发展的大好形势。我国钢结构建筑的快速发展,为热轧H型钢的进步和推广创造了良好的市场条件。本课题研究的开展是鉴于在工艺优化前,企业原生产的成分为Q345E系列的H型钢的低温冲击韧性(-40℃)不良,波动幅度较大。因此本文研究的目的就是通过微合金处理工艺,改善H型钢在低温下的冲击韧性,扩大H型钢的使用范围。本文的研究步骤为:第一步,分析企业原生产的H型钢,分析影响低温冲击韧性的可能因素;第二步,实验室研究阶段,探寻微合金处理的可行性;第三步,在实验室结论指导下进行工业化生产。在各个阶段的研究过程中,首先测定其不同温度下的冲击吸收功,并利用光学显微镜、透射电镜(TEM)、扫描电镜(SEM)对某些试样的金相组织、金属薄片和萃取复型碳膜、冲击断口进行观察研究。在研究过程中重点是硼的微合金处理。在以往的研究中,硼主要用来提高钢的淬透性能。而在本研究中通过添加适量的硼元素,来达到改善低温冲击韧性的目的。通过工业生产发现,在通过实验室指导后所生产的H钢的低温冲击性能获得大幅度的提高,说明微量硼元素的加入对于大幅度改善H型钢的低温冲击韧性作用。其作用机理可能是净化晶界,同时与Nb复合作用起到细化晶粒的作用,推迟奥氏体转变,使得贝氏体含量增加,获得铁素体、珠光体和贝氏体的混合组织,钢的强度和韧性都获得改善。这对于扩展H型钢在低温地区的使用具有重要意义。更多还原

【Abstract】 According to different applications,hot rolled H-beams distribute height to width ratio of its section rationally.It has fine mechanical properties and usability.H-beams are used widely because of its light weight,high strength,good shock resistance, quick commercial process and construction speed,energy conservation and environmental protection.Our country has had the condition to develop steel structure; the constructs of steel structure present a thriving sight.The development of the constructs of steel structure creates good market conditions for the popularization of hot rolled H-beams.The hot rolled H-beams,base on the composition of Q345E,have unstable impact toughness at low temperature,especially in -40℃.The purpose of this research is to improve the impact toughness at low temperature and expand the scope of application by microalloying techniques.The process of this research is divided into three steps:firstly,the previous H-beams were analyzed to find the possible reasons which affect the impact toughness at low temperature;secondly,the laboratory research is to find whether the microalloy treatment is feasible or not;thirdly,commercial process was carried out under laboratory research’s guidance.In each stage,the impact energy was tested at different temperature,and then the metallurgical structure,leaf metal,replica carbon film and impact fracture were detected by using optical microscope,TEM and SEM. Boron treatment is the highlight in this paper.In the past research,boron is mainly used to improve the hardenability.But in the research,the purpose is to increase the impact property at low temperature by adding boron element.The impact toughness at low temperature was improved in the commercial process under laboratory research’s guidance.It confirmed that B element could help to perfect the impact toughness at low temperature considerably.The mechanism of action may be that boron should purify the boundary of the grains.The boron works with niobium.They fine the grain,postpone austenitic transformation and increase the content of bainite.The strength and the toughness were improved by getting mixture structure consisting of ferrite,pearlite and bainite.This would help to expand the range of application of H-beams in the cold environment.更多还原