【作者】 冯煌；

【导师】 樊建成；

【作者基本信息】 上海交通大学 ， 机械制造及其自动化， 2011， 硕士

【摘要】 宝钢5000mm厚板轧机是世界上第一架采用十字轴式万向接轴作为主传动轴的厚板轧机,也是迄今为止国内最先进的轧机。宝钢厚板轧机主传动系统由电机、减速箱、分配箱、联接轴、联轴器等组成,其具有传递扭矩大、应力大、冲击大、尺寸受空间严格限制等特点。自投产以来,宝钢厚板轧机的主传动系统多次发生断裂的特大设备事故。主要失效形式有,法兰过渡圆角部位断裂、激光修复后万向节叉头断裂,严重影响了厚板轧机的正常生产,大大增加了设备检修和备品备件的成本。为解决厚板主传动轴异常断裂的问题和提高其修复技术,有必要对主传动系统进行相关分析。本文将有限元分析技术和实验研究相结合,探讨主传动轴异常断裂的原因,分析断裂叉头的失效机理。探明失效原因后,有必要开展激光修复工艺的研究工作,取得了下列研究成果:第一,建立了厚板轧机主传动系统的数学模型。通过MATLAB对数学模型进行仿真分析,得到了主传动系统的固有频率和扭矩放大系数(TAF);根据轧机设计原则,结果表明:厚板轧机设计是合理的;对厚板轧机的现场扭矩进行了测试,测试结果的频谱分析和仿真计算结果基本吻合,验证了数学模型的正确性,进一步证明了轧机主传动系统设计的合理性。第二,对经常发生断裂的主传动系统法兰圆角和叉头处进行了有限元和工程力学方法分析。计算结果得出,在稳态轧制力矩为4000 kN·m时,60mm和80mm的法兰圆角半径其最大等效应力值分别为111MPa和101MPa;圆角弧度为2mm、60mm、80mm其安全系数分别为1.4,、3.131、3.269,由此可见,法兰过渡圆角过小是造成主传动轴法兰断裂的根本原因,提出加大过渡圆角的改进建议,应用到现场后,杜绝了主传动轴法兰断裂的设备事故;还得出叉头的最大等效应力为361.196Mpa,远低于材料的屈服应力,叉头应属于疲劳失效断裂,计算出叉头疲劳安全系数仅为0.303,远低于其设计要求,在现有载荷条件下疲劳寿命严重不足是叉头多次断裂失效的原因,提出了降低轧机载荷的改进措施,避免了新品万向节叉头断裂的设备事故。第三,对断裂的叉头进行失效机理分析。通过对万向节叉头进行宏微观断口形貌分析、化学成分分析、机械性能测试、金相组织分析,得出叉头的断裂形式为疲劳断裂,其疲劳断裂的主要原因除了叉头设计寿命不足外,叉头轴承孔工作面及次表层的激光熔覆、局部补焊缺陷产生了裂纹源,在周期应力的作用下,疲劳裂纹加速扩展,最终导致叉头的断裂。失效机理分析结果表明:不恰当的激光熔覆工艺是造成激光熔覆叉头在短期内即发生断裂失效的根本原因。第四,在失效分析的基础上,对万向节的修复工艺进行研究。根据万向节叉头的材料性能、使用工况以及应力状态等,选择两个不同部位(叉头和叉头法兰处)和两种不同Ni选择了进行激光熔覆工艺研究,对表面硬度、残余应力和金相组织检测结果进行分析,得出Ni基粉末DL2在低残余应力部位熔覆效果更好,从而得出了适合叉头的激光熔覆工艺。通过上机考核试验,新工艺熔覆的叉头,到目前其使用寿命已经超过了3个月,远远高于原先熔覆工艺3周的使用寿命。厚板轧机主传动轴为大扭矩(最大实测扭矩为7000KNm)、高应力并承受强烈冲击的机械零件。激光熔覆作为一门新兴技术,其具有不同与常规堆焊、电镀、喷涂等工艺的一些特点和优势,正在日益广泛地应用于工业上。对激光熔覆技术在大扭矩、高应力机械零件的修复方面应用的研究,有助于拓展激光熔覆技术的工业应用,也有助于提高大型机械传动零件修复和再制造的技术水平。更多还原

【Abstract】 Baosteel Company is the first used of the 5000mm width heavy plated mill in domestic, it is also one of the most advanced heavy plated mill in the world. The main drive system of rolling mill in Baosteel company is composed of motor, reducer, distribution box, connecting shaft and couplings etc, it has the characteristics that transmission torque is large, stress is great, impact is big, dimension is strictly limited etc. Since its operation, the main transmission system of Baosteel thick heavy rolling mill repeatedly happens super-large equipment fracture accidents, mainly including: flange transition rounded part fracture, laser repaired joint head fracture, which seriously affected the thick heavy rolling mill normal production and greatly increased equipment repairing and spare parts cost. This paper focuses on main shaft accident in the Baosteel company, carrying out the related research.To solve the thick heavy plated mill’s main shaft abnormal fracture problem and improve its repair technology, it is necessary to analyze its main transmission system. This paper combines finite element analysis method with experimental research, discussing unusual cracking reasons of the main shaft , analyzing the failure mechanism of fracture fork head. After finding the failure reason, it is necessary to study laser repair technology and achieved the following research results:First, establishing the mathematical model of the main transmission system. Simulating the mathematical model through MATLAB, calculating the spindle of natural frequencies and torque amplitude factor for the inspection of the design, through the field test data analysis verify the correctness of the mathematical model, it is concluded that the spindle design is reasonable.Second, applying finite element analysis and engineering mechanics method to often fractured flange and fork head. It obtained the calculation results,for the steady rolling torque of 4000 kN?m, 60mm 80mm flange fillet radius have the maximum equivalent stress value 111MPa and 101MPa respectively, Rounded radian of 2mm 80mm 60mm,its safety coefficient is respectively 3.131, 1.4 3.269, thus it can be seen, flange failure due to too small fillet caused by the local stress concentration, and advances improving opinions, after implementing the correct action, the flange fracture has not occurred, fork head analysis get the feedback fork head of the maximum equivalent stress is 361.196Mpa, far from reaching its ultimate strength, fork head fracture should belong to fatigue damage failure, according to fatigue failure theory fork head safety coefficient is 0.303, far from meeting the design requirements, which leads to the fork head failure, proposed reducing mill load improvement measures, to avoid the new joint head rupture.Third, failure mechanism analysis of fractured fork head. Though the disassembly analysis of the fractured fork head, looking for fork head of failure mechanism, Through performing macro and micro morphology analysis, chemical composition analysis, mechanical property testing, microstructure analysis, obtains that the fracture mode for fork head is fatigue fracture, The main reasons of the fatigue fracture besides the fork head design life expectancy is insufficient, the fork head bearing hole working face, the laser cladding of inner surface and local repair caused the defects, these defects caused crack expanding further under periodic stress, The failure mechanism analysis results showed that inappropriate laser caused the ford head fracture, if we can raise fork head hole repairing process, it can greatly improve expected life of the fork head.Fourth, on the foundation of the failure analysis, studying the repair technology of universal joint. According to the joint head materials properties, operating conditions and stress state etc, choose two different parts (fork head and fork head flange) and two different Ni based powder for laser cladding process research, analyze the surface hardness results, residual stress and microstructure detection results, it got the conclusion that DL2 Ni based powder in low residual stress position cladding effect is better, and also got the suitable fork head laser cladding process, through computer tests, the new laser cladding repaired fork head, its service life already amounted to 3 months at present, far longer than previously cladding process 3 weeks using life.Thick heavy rolling mill shaft has the maximum torque (the measured lord is 7000KNm), high stress and under strong impact. Laser cladding as a new technology is different from conventional surfacing, electroplating, spraying process, it has some features and advantages, which are increasingly widely used in industry. By means of application research about laser cladding on big torque and high stress of mechanical parts repairing , it helps to develop laser cladding industrial application, also helps to improve the large mechanical transmission parts repair and remanufacturing technology level.更多还原