【作者】 高亚男；

【导师】 肖宏；

【作者基本信息】 燕山大学 ， 机械设计及理论， 2012， 博士

【摘要】 随着钢筋混凝土建筑结构由于钢筋的腐蚀而破坏越来越受到人们的关注，新型的建筑用钢筋被不断的研究和设计。由于不锈钢/碳钢覆层钢筋在各种防腐措施中效果较好，可以满足人们对钢筋混凝土建筑结构设计寿命提高的要求，近些年学者和工程技术人员对这种钢筋的研究越来越多。随着科技的进步以及生产技术的发展，多种方法被应用于不锈钢/碳钢覆层钢筋的生产上。热轧是不锈钢/碳钢覆层钢筋生产方式中最有前途的一种，人们已经对其进行了研究并取得一定的成果，但该方法仍处于试验阶段，并存在一定的问题。覆层钢筋轧制是多因素耦合作用下的复杂过程，对于孔型的设计，变形过程中的金属流动规律等尚无系统理论或研究成果，国外对该领域的研究刚刚起步，而我国对不锈钢/碳钢覆层钢筋的生产以及理论的研究仍是空白。本文首先建立了正确反映不锈钢/碳钢覆层钢筋轧制过程的有限元模型。在轧制过程中，覆层钢筋两金属的接触复合状态是发生变化的并且常用方法不能解决该问题。因此，对商业有限元软件MSC.MARC进行二次开发，编写子程序，通过程序判断节点与接触面是否粘结，并和其它常用界面处理方法以及实验结果进行比较，证明了使用本文方法可以合理判断轧制过程中两金属的接触复合状态。合理的设计孔型系统，研究了不锈钢/碳钢覆层钢筋轧制过程中金属的变形以及与单一金属轧制的区别，发现两者的变形存在一定的差异，轧制单一金属的孔型系统不能够轧制覆层钢筋。在有限元模拟的基础上，对比研究了平椭-圆孔型系统和菱-菱孔型系统轧制不锈钢/碳钢覆层钢筋过程中，对界面间接触应力、不锈钢壁厚分布规律的影响。之后，对覆层钢筋的轧制工艺进行了考察。以菱-菱孔型系统轧制过程为研究对象，研究了孔型参数、不锈钢壁厚、轧辊与轧件间的摩擦对双金属复合效果和宽展的作用，讨论了中心压实法和张/推力轧制在覆层钢筋热轧过程中的应用效果。通过研究发现，表面温度提高有利于两金属的复合，张力轧制不利于金属间复合但有利于不锈钢壁厚分布均匀，这些为不锈钢覆层钢筋的实际轧制奠定理论基础。为进一步了解不锈钢/碳钢芯覆层钢筋的实际轧制复合效果，进行了热轧实验。对比了平椭-圆孔型系统和菱-菱孔型系统热轧覆层钢筋的优缺点，发现使用菱-菱孔型轧制复合效果较明显，并在菱-菱孔型热轧的基础上，研究了覆层钢筋的机械性能和金属间的元素扩散情况，分析了轧制道次、压下量、轧制温度、微推力等工艺对覆层钢筋变形及复合效果的影响。随轧制道次，压下量，轧制温度的提高以及微推力的使用，金属间复合效果改善。接下来，研究了碳钢屑的热压成型工艺，分析了压制工艺参数，如压制力、温度、金属粘结剂对碳钢屑材料的性能影响，探讨了碳钢屑粘结机理，证明了碳钢屑可以经过一定的工艺制备成具有一定强度的金属材料。进而研究了不锈钢/碳钢屑芯覆层钢筋的热轧成型工艺，热轧制备出不锈钢/碳钢屑芯覆层钢筋。考察轧制道次、轧制温度、石墨添加量、退火工艺对不锈钢/碳钢屑芯覆层钢筋机械性能的影响。研究发现，轧制工艺条件以及石墨添加量对覆层钢筋性能的影响很大，可以通过调整轧制工艺条件来提高不锈钢/碳钢屑芯覆层钢筋的机械性能。更多还原

【Abstract】 With more attention of people paying on reinforced concrete structures’ damagebecause of corrosion of reinforcing steel bar, new reinforced bar for building has beencontinuously research and design. Stainless steel/carbon steel cladding bar is the mostanticorrosive method which can meet the requirement of people on increasing lifeexpectancy of concrete buildings. With the development of technology andmanufacturing technique, lots of methods have been used in this kind production. Hotrolling is the most promising method and some achievements had made. However, it isstill experimental, and there are some problems. It is a complex process under coupledeffects of multi-factors, and there is no system theory or research on pass design andmetal flow law. The researches on this field of overseas just start, but still blank in China.First, a finite element model which can reflect of rolling process of the stainlesssteel/carbon steel cladding bar correctly was established in this article. The bonding stateof the contact surface of the metals is variation and the common software cannot solvethis problem. So a subprogram was compiled based on the secondary development ofMSC.MARC and it used to judge whether the nodes bonding to the contact surface. Then,the result was compared with other three methods commonly used，and it proved that thebonding state of the contact surface in the rolling process can be gotten using the methodin this article.With reasonable pass designing, the metal flow and the difference to homogeneousmetal rolling were studied. It was found that the deformation between two kinds bar isdifferent, so the passes used for homogeneous metal cannot be used for cladding bar.Based on the finite element simulation, the contact stress of interface and wallthickness distribution of stainless steel were comparatively studied in the rolling processof stainless steel/carbon steel cladding bar using flat oval-round pass system anddiamond-diamond pass system. Later, the rolling process of cladding bar wasinvestigated. By using the diamond-diamond pass system，the effect of pass parameters, wall thickness of stainless steel and friction between roller and workpiece on bondingand spread were studied. It emphatically discussed the application effect of surfacetemperature difference method and tensile/thrust on rolling of the cladding bar. Theresults indicated it is advantageous to bonding with rising the surface temperature andtensile rolling is disadvantageous to bonding but advantageous to the thickness ofstainless steel wall. All will lay the theoretical foundation for the actual rolling ofstainless steel/carbon steel bar.In order to find out the bonding effect of the actual rolling, a hot rolling experimentwas carried out. The bonding effect in the rolling process by using flat oval-round passsystem and diamond-diamond pass system were comparatively. The obvious bondingresult using diamond-diamond pass system can be found. On the foundation of using thediamond-diamond pass system, the properties and elements diffusion of cladding barwere studied. Then, the effect of rolling pass, pass reduction, rolling temperature andmicro thrust on deform and bonding of cladding bar were analyzed. The bonding resultsimproved with the increment of passes, reduction, temperature and micro thrust.Next, the hot press process of iron chips and the effect of the process parameters(such as press force, temperature and metallic binder) on properties of chips materialwere studied, which proved that the iron chips can become into a kind of material using aspecial process. The bonding mechanism of the iron chips was discussed and hot rollingprocess of stainless steel/iron chips core cladding bar were carried out, from which theeffect of rolling pass, rolling temperature, graphite content and annealing process onmechanical properties of cladding bar were analyzed. It is found out that great effect ofrolling process and graphite content on the properties of carbon steel chips core claddingbar, so the mechanical property of this bar can be adjusted by changing rolling process.更多还原