推钢机

1天津冶金职业技术学院毕业设计推钢机技术系别电气工程系专业生产过程自动化班级过控08-1班学生姓名岳南指导教师李炜2011年4月20日2目录摘要······························································Ⅲ前言······························································Ⅳ第一章推钢机的简介················································11.1推钢机的种类················································11.2推钢机结构特点及工作原理····································11.3设计中应注意的几点事项······································21.3.1推力的计算·············································21.3.2齿轮的选择·············································21.3.3推杆的结构·············································31.3.4推钢速度···············································31.3.5推钢机行程·············································31.4推钢机未来发展趋势··········································3第二章电机电气控制、启动方式和线路保护····························42.1电气控制图··················································42.2异步电动机降压启动线路·····································112.2.1定子电路串电阻降压启动···································122.2.2串自耦变压器降压启动控制线路··························122.2.3自耦变压器降压起动控制电路·······························132.3停车····················································142.4线路保护环节···············································142.4.1短路保护··············································142.4.2过载保护··············································142.4.3欠压和失压保护········································15第三章液压系统·····································163.1什么是液压系统··········································163.2液压系统的结构··········································163.3液压系统对液压油的基本要求······························163.4液压系统的保养··········································16第四章PLC及现场总线··············································1834.1PLC基本概念···············································184.2PLC的定义··················································184.3PLC的分类··················································184.3.1小型PLC···············································184.3.2中型PLC··············································184.3.3大型PLC··············································184.4PLC硬件组成················································184.4.1CPU运算和控制中心起“心脏“作用·························184.4.2存储器················································184.4.3输入/输出接口·········································184.4.4编程器················································184.5PLC的基本工作原理·········································184.6PLC的特点·················································194.6.1PLC的主要特点········································194.6.2PLC的功能·············································194.7PROFIBUS···················································204.8推钢机的自动控制···········································20参考文献·························································22致谢·····························································234摘要推钢机是冶金轧钢生产线上将钢坯推进加热炉内进行加热的专用设备，它充分使用了液压油缸和液压系统的出力大，体积小操作方便的优点。充分使用了液压油缸和液压系统的出力大，体积小操作方便的优点。使推料工序得到减化，同时也降低了设备成本。推钢机以先进的自动化控制设备和计算机技术的应用，冷轧不锈钢带、硅钢带、精密合金钢带、稀有合金带、高精度极薄冷轧碳素钢带等各种高精度高品质产品的出产，大大地促进了轧钢生产企业的经济效益和竞争能力，有力地提升了我国轧钢生产企业的形象。推钢机解决了在高温、高粉尘下工作油缸的密封、主机导向部位的密封及磨损问题，从根本上解决了液压系统维护难、寿命短的问题。完全替代了以前的人工作业，实现了多个推爪同步机械自动化操作，提高了生产的小时作业率.推钢机是轧钢车间上料区主要设备之一，其作用是将加热炉前辊道上的钢坯或炉前上料台架上的钢坯推入加热炉进行二次加热过程。本设计选用了机械式推钢机，在推钢机结构设计上主要采用了齿轮齿条的结构形式。该机构具有结构简单，整体尺寸适中，传动效率高，维修方便，造价较低的优点。在本设计中主要对推钢机进行了结构设计和理论计算，并着重对传动机构做了详细的分析设计。关键词：PLC；PLC通信；总线；电机的星角启动5前言我国钢铁工业近年来发展很快，钢产量己连续多年突破亿吨大关，钢铁产品质量也得到了很大的提高，特别是在轧钢生产方面。各种高精度轧钢机械设备的引进和投产，先进的自动化控制设备和计算机技术的应用，冷轧不锈钢带、硅钢带、精密合金钢带、稀有合金带、高精度极薄冷轧碳素钢带等各种高精度高品质产品的出产，大大地促进了轧钢生产企业的经济效益和竞争能力，有力地提升了我国轧钢生产企业的形象。但是由于科学技术的飞速发展，新的设备和新的技术以惊人的速度不停地改进和更新，产品的技术含量越来越高，对产品生产机械设备和操作技术的要求也越来越高。因而及时掌握新型轧钢机械设备的性能，熟练掌握新的操作技术，全面应用先进的自动化控制技术和计算机轧制技术，是当前轧钢生产企业进一步提高产品质量、降低轧钢生产成本、增强轧钢生产企业的市场竞争能力的关键所在。本设计包括了自动化控制系统及推钢机的设计，并重点针对程序设计。具体包括：自动化控制简介，推钢机的分类、结构和工作原理，电动机的选用和启动控制方式。电动机的选定标准是满足推钢机总的功率要求，转速适中，并且应具有频繁快速启动和反转能力以带动推钢机推杆做往复运动。控制总线选择了PROFIBUS，其应用了IEC标准的物理层，从而可以在爆炸危险的区域内连接本质安全型通过总线馈电的现场仪表。编程工具我们选择了西门子的S7—200，它结构紧凑、扩展性能良好、指令功能强大、价格低廉成为当代各种小型控制工程的理想控制器。电机的启动方式选择了星—角降压启动，因为这种方式能降低启动时的电压，限制启动电流，所以特别适用容量较大的电动机。电机控制电路选择的是时间继电器自动控制星—角降压启动控制路线，时间继电器KT做控制电动机Y形降压启动时间和完成星—角自动切换。第一章推钢机的简介1.1推钢机的种类推钢机主要用于炉前坯料，通过推钢机输出动力，逐步向炉内推移，进行加热处6理。推钢机的种类很多，常见的有齿轮齿条式、丝杠螺母式、曲柄连杆式、液压式等，还有的推钢机把齿轮齿条传动和液压传动相结合，形成了液压齿条式。它们各自有自身的特点，在不同的加热炉上发挥着各自的作用。齿轮齿条式推钢机通过齿轮齿条的啮合传动把电机的旋转运动转变为齿条的直线运动，带动推杆进行推钢工作。其工作可靠，传动效率高，推力和行程大，但设备自身重量大。目前齿轮齿条式推钢机应用比较广泛。丝杠螺母式和曲柄连杆式工作效率低，行程和推力较小，一般用于小型加热炉，新上加热炉一般很少采用。液压式推钢机由液压缸直接推动推杆工作，结构简单，推力大，自重轻，速度、行程易控制，但行程不宜太大，且液压系统制作、维护较困难。根据钢车间使用的经验，推力在0.2MN以上时，一般采用齿条式推钢机较适宜。因为齿条式推钢机传动效率高，使用可靠，这是螺旋式推钢机无法比拟的。1.2推钢机结构特点及工作原理推钢机的结构特点：机械型推钢机由电机、减速机及机械传动部分、壳体等组成，其主要特点是推行平稳，推力大，可推进双排坯料。液压型推钢机由液压油缸、液压泵站、平衡推杆及底座等组成。液压推钢机的特点是：结构简单、推力大、造价低，也可推进双排坯料。机械式（齿轮齿条）推钢机制作成本及复杂程度远远高于液压推钢机，并且体积庞大笨重，噪音大，随机控制性能差；机械推钢机维护要比液压推钢机麻烦，一但出现故障必须停机待修；维护工作量及维护成本远远高于液压推钢机。液压推钢机在推力上远远高于机械式推钢机：同样功率的情况下两者的推钢能力要差好多倍，如果同样推动250吨钢坯，液压推钢机只需要55千瓦的驱动功率即可满足要求，但机械推钢机要达到200千瓦以上的驱动功率才能正常工作。71.3设计中应注意的几点事项1.3.1推力的计算推力、推速、行程是推钢机的主要技术参数，尤其是最大推力。推力计算的正确与否关系着推钢机的经济性和使用寿命。推力计算公式为：1;FGgfK（1-1）式中：G为钢坯质量，单位是kg；g为重力加速度，一般来说29.81/gms；1K为考虑到加热炉轨道不平，受热变形等因素的影响系数，1K=1.1～1.3。f为滑动摩擦系数，f=