3820 真空抬包设计抬包结构设计真空度分析
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3820 真空抬包设计抬包结构设计真空度分析,3820,真空抬包设计抬包结构设计,真空度分析,真空,设计,结构设计,分析
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中原工学院毕业设计实习报告 毕业实习报告题目名称： 真空抬包设计 抬包结构设计，真空度分析 院系名称： 机电学院 班 级： 机自071班 学 号：200700314133 学生姓名： 竹怀振 指导教师： 王玮 2011年3月目录一 前言3二、实习概况41、公司简介42、实习过程72.1 铆煅车间72.2大修车间82.3 金工车间82.4 装配车间83、实习小结9三、课题调研9四、实习总结11五参考文献13一 前言毕业实习是一门专业实践课，是机械类各专业学生学习了各门专业课程之后，在完成毕业设计时必不可少的实践教学环节。它对于培养我们的动手能力有很大的意义，而且可以使我们了解传统的机械制造工艺和现代机械制造技术。另一方面，为做好毕业设计，学生也有必要深入工厂，进行课题调研，找出关键问题，理顺设计思路，更好地完成毕业设计。总的来说，毕业实习既是学生学习、研究与实践成果的全面总结，又是学生综合素质和工程实践能力培养效果的检验。毕业实习旨在让我们围绕专业及设计课题进一步了解与之有关的实际情况，进行资料的收集，为解决课题任务提供必要的条件。实习方式主要是实地考察，观察研究与课题相关的技术设备运行情况，向企业的现场操作人员学习请教相关知识，以便形成直观感受，从而提高到理论的高度来研究、分析、找到解决问题的关键所在。毕业设计是我们在大学校园里的最后一个环节了，我们在学校里学的好坏，将会在这里得到检验。毕业实习又是毕业设计的必备环节，正因为如此，此次实习对于学习机械专业的我们来说，就显得尤为重要。在本次实习中，我们主要向使用者学习，了解产品存在的问题及改进的愿望和要求，由此可减少设计的盲目性，提高效率。同时通过实习我们要达到一个目标，以方便完成以后的任务。首先要通过实习来巩固、加深和扩大所学的理论知识，使理论更好的结合实际，通过参观和学习，对机械设计建立全面的系统概念，补充理论教学的不足；其次要通过仔细了解和自己毕业设计有关的产品的生产制造过程，如机床的布局，各零部件的加工工艺过程，零部件组装成成品的装配过程等等，来熟悉工厂的生产加工过程；另外通过对和自己毕业设计有关产品的原理、结构以及各零部件的结构的了解认识，为毕业设计（论文）收集资料，使自己的毕业设计得以顺利完成。同时通过亲身感受工厂的生产环境、生产过程、生产管理等，也为即将走上工作岗位积累感性认识，奠定坚实的基础。二、实习概况1、公司简介 毕业实习，我们来参观的是中国长城铝业公司河南分公司，属国家三级企业，是最大的国有生产铝企业。它以生产氧化铝、氢氧化铝和铝锭为产品的大型基地，其铝锭的规格按国家的标准，也是多种多样。中国铝业股份有限公司河南分公司是亚洲最大的氧化铝生产基地，经济效益和纳税总额均居国家统计局和国家税务总局公布的全国有色金属冶炼和压延加工企业首位，名列国家统计局公布的2006年度中国制造业500强铝工业企业首位，是中央文明委命名的首批全国文明单位，河南省政府表彰的首批工业突出贡献企业，荣获全国五一劳动奖状等荣誉称号。公司的前身是始建于1958年的郑州铝厂，1992年6月组建为中国长城铝业公司，2002年1月，根据中国铝业股份有限公司海外上市的总体部署，原中国长城铝业公司氧化铝和电解铝板块的资产重组，组建中国铝业股份有限公司河南分公司。公司位于中原郑州，区位优势、资源优势明显。 公司集冶炼、发电、运输、建筑、机械制造、科研、设计于一体，主要产品有氧化铝、氢氧化铝、化学品氧化铝、铝锭及铝合金板锭系列产品、碳阳极、金属镓、高纯镓及其深加工产品。“雪山牌”铝锭在伦敦金属交易所注册。产品畅销全国，远销18个国家和地区，享有较高声誉。 2002年以来，公司落实科学发展观，推进内涵挖潜和外延扩大再生产的超常规发展战略，氧化铝产量蝉联亚洲第一，资产总值和销售收入分别达到80亿元和70亿元以上。到2005年底，公司资产总值、销售收入、实现利润和上缴税费分别是2001年公司成立前的2倍、2倍、35倍、5倍，利润总额蝉联河南省企业（集团）首位，已形成年产氧化铝230万吨以上、铝锭5.8万吨、碳素制品12万吨的生产能力，跻身世界氧化铝企业5强。 公司坚持强化自主创新，在国际同行业首创中国独特的拜耳烧结混联法生产氧化铝新工艺，在国内外同行业率先研发成功具有自主知识产权并达到国际领先水平的一水硬铝石管道化溶出、选矿-拜耳法生产氧化铝新工艺、间接加热连续脱硅、高分子絮凝剂沉降分离、烧结法生料浆自动配制、树脂法提取金属镓等新工艺、技术和装备。开发的常压脱硅、高效沉降槽等技术和装备在国内同行业推广应用。采用的降膜蒸发、气态悬浮焙烧等装备和技术达到世界先进水平。首创的电解铝预焙槽改造技术为国内自焙槽的升级换代提供了典范。 公司大力弘扬“励精图治、创新求强”的企业精神，恪守“实勤公高”的核心理念，推进以“缺陷管理标准化管理信息化管理”为核心的管理升级“三步走”战略，首家通过全国4A级（最高级）标准化良好行为企业验收，荣获全国优秀设备管理单位、全国名优产品售后服务先进单位、全国首批专利试点工作合格单位、全国企业安全文化建设先进单位等称号，被评为中国企业文化最具影响力企业。 “十一五”期间，公司将坚定不移地贯彻落实党的十六届五中全会精神，大力发展循环经济和清洁生产，创建资源节约型和环境友好型的世界一流企业，力争资产总值和销售收入突破“双百亿”，成本、质量等达到国际一流水平，在安全生产、环境保护、履行社会责任等方面树立良好的国际形象，成为内有控制力和凝聚力，外有竞争力和影响力的世界氧化铝强企，为“创建世界一流企业、打造中铝百年老店”做出新的贡献。 这次实习我们重点对其公司下属的二级企业，即机械制造公司，对其进行参观和实习。中国铝业是国内最大的氧化铝生产单位，我的课题是氧化铝生产线中一个必不可少的步骤，而且该厂自投入生产以来设备不断维护更新已处于领先地位，机械分公司可以针对客户要求，进行设计改进并且可以对国外引进设备进行安装.调试。由此，我们来到该厂进行参观，收集资料，完成毕业设计。下面我对该厂情况做一下介绍。 该公司是境外上市公司中国铝业股份有限公司河南分公司的二级单位，是从事设备制造和备件生产，并通过IS09000质量体系认证、取得BRl级压力容器制造资质的生产企业，具有年产综合机械产品7000吨、氧气26万瓶及年创设备安装、大修产值1300万元能力的中型设备与备件制造厂。拥有固定资产7000余万元，大型、数控及精密等各类设备逾470台。有表面沉积和激光加工中心，可承制冶金、矿山、建材、有色、化工等行业所需成套、大型、精密设备以及各种毛坯、机械零配件。80年代之前曾长年承担国家军工精密零部件制造的机械制造公司，在市场经济的大潮中，面对入世，对标国际，与时俱进，创新发展，形成了以市场为导向、以质量为中心、以产品开发为龙头的产供销一体化生产经营新格局。公司技术力量雄厚，拥有教授级高工1人，高级工程师15人，工程师22人。98年以来，公司走企业与大专院校、科研院所联合开发高新技术之路，先后研制的贝氏体磨球、高效耐磨固液泵、无螺栓磨机衬板、铝电解阳极提升机等通过省部级鉴定，分别达到国内和国际领先水平。新型无螺栓衬板，是我公司研制开发的高技术产品，获中国有色科技三等奖。该产品具有运转效率高、维护工作量小、不漏料的特点，使用寿命是高锰钢衬板的两倍。此项技术处于国内领先水平，是球磨机高锰钢衬板的更新换代产品。高效耐磨固液泵，获中国有色科技二等奖。该产品具有节能、耐磨、运行平稳、低噪声等优点，产品性能达到90年代初期国际领先水平，为九五国家科技成果重点推广项目。铝电解行业设备主要有铝锭连续铸造机、真空铝水抬包、铝导杆校直机、阳极（母线）提升装置等。我公司生产的不同吨位、多种规格、两点及多点阳极提升机，适用于铝电解生产的各种槽型，是冶金工业预焙电解槽传动系统中的重要设备之一。该装置能承受巨大负荷，操作先进、升降稳定，也可作为机车、大型车辆、船舶的制造、修理升降装置。20kg铝绽连续生产机组用于电解铝铸锭工序的铝锭铸造、堆装，具有连续高效的工作特点。该设备技术先进、结构紧凑、操作方便、动作可靠，同时无污染、噪声小，改善了工作环境。碳素行业设备主要有单工位振动成型机、煅烧炉设备、混捏锅等。新型碳块成型机，获郑州市技术进步一等奖。现己制作12台，分别在兰州、焦作、重庆、山东等地安装使用，受到用户高度赞扬。该公司是郑州市文明单位标兵和市工商局重合同守信用企业，多年来恪守售后服务十项承诺，力行快速反应，马上行动的工作作风，竭诚为用户提供设计、制作、安装、调试、技术指导、维修、货运等全方位的服务。2、实习过程在三月十五日，我们来到了中国长城铝业公司河南分公司，由王教授带领我们对该厂进行参观和实习。接待我们的是施科长，由他带着我们对机械制造分厂进行实际的参观。机械制造分厂的主要产品及技术参数： 铝锭连续铸造机型号LZA-1铸锭重量（kg）20产量（kg/h）9000铸模数量（个）106铸模移动速度（m/min）1.997生产铸锭量（锭/h）460电机功率（KW）5.5设备重量（kg）12000 阳极提升机 螺旋式捞渣机 施科长带领我们集体参观了铆煅车间，大修车间，金工车间及装配车间。2.1 铆煅车间在铆锻车间，我们逐步参观，看到了ZPS-1250焊接操作机，工作能力：3500毫米，液压刨边机，工作能力：12000*80，数控切割机，工作能力：4500*18000，三辊卷板机，工作能力：30*3000，压力机，工作能力：300T，RT9型台车式电阻炉RJ2756型井式炉，工作温度：950度。在参观的众多机器中，有的不在工作状态，有的正在工作中，比如，数控切割机，工作人员把所编辑的程序指令输入到机器中，我们看到了机械加工的过程。2.2大修车间从铆锻车间走出，我们来到了对面的大修车间，里面的机器较为普遍，大部分是我们所常见到的小型车床，但也看到了一台测平衡的平衡机。2.3 金工车间之后，我们进入了大部分机器都在工作的金工车间，这里可是机械制造的心脏。我们看到的有：落地镗床 T6216 插床 B50100 大车床 5m 单臂刨床 B110 卧式镗床 T68 端面铣床 1100*2300齿 伞齿刨 M20 800 卧式万能镗床 Z620滚齿机 Y3180H 滚齿机 W1Y3J滚齿机 Y31125E 插齿机 Y54小立车 CY5112 平面磨床 M7130 万能铲齿车床 C8955 大型龙门刨床 B220 立式车床 C5235A 落地车床 1H692摇臂钻床 Z37 插床 7M4302.4 装配车间 最后，我们来到了装配车间。这里主要进行对设计的产品进行一个整体的装配与调试。其中，有许多钳工专用的工具，如手工锯，虎钳等。在厂房内，还见到了许多木质垫块，主要用于设备在车上的安放和稳固。3、实习小结 从中国铝业有限公司参观回来之后，我感触很深。以前的我由于接触社会少，所以对相关的认识了解的很少。我尽我所能去联想，该公司生产的铝会用于何处，想起学校里的餐具，以及各式各样的铝合金门窗等，才明白铝业对我国的经济发展作用是如此巨大,。其实每个公司不论是私有还是公有、不论是大公司还是小公司都有它坚持的理念，都有适合它自己的规范，既要有自我的坚持、自己的与众不同，又要有不断的变革、不断的改进，他们就会以最低的成本来生产出最实用的产品，来满足市场需求，为社会创造出最大的价值。三、课题调研 这次实习的主要目的，就是来针对各自的设计课题及设计要求而进行调查、分析，从而通过不断地分析研究，找出解决的方案。这次我们的设计课题是真空抬包设计，真空抬包是电解铝冶炼过程中的一个重要设备，其主要功能是将电解槽中的电解铝液吸出并倒运至混合炉。中国铝业河南分公司电解厂原电解槽为65KA自焙槽，年产铝量为3万吨，采用容重为2吨的真空抬包来吸铝，并配合5吨的敞口包来倒运即可满足生产的需要。随着电解技改扩建项目的完成，电解槽变为85KA预焙槽，电解厂年产铝量为5万吨，为解决铝液抽吸运转效率低下、铝液热量损失大的问题，需要研发容重为4-6 吨无需中转浇包倒运的真空抬包。随着国内一些大型预焙电解槽的研发成功， 电流已陆续提高至160KA、200KA、280KA、320KA，电解槽产铝量大增，小型吸铝真空抬包已不能满足生产的需要。小型吸铝真空抬包在外形上一般为普通倾注式锥桶形真空抬包，在结构上可分为包体、人孔、吊架、吸铝管、减速机及真空管等几部分。其容重一般在2吨以下，体积小，减速机为手动操作。小型抬包主要用于小型电解铝厂，工作时直接采用负压吸铝，需要单独配置一套真空系统，由于吸入空气温度较高，真空泵一般采用水环真空泵，设备配置价高。抬包的清渣、检修及砌包衬均通过人孔进行，极为不便。为提高使用效率，小型抬包使用时往往需要大型敞口浇包配合使用，这样会带来铝液热量的损失。大型吸铝真空抬包主要由包盖、包体、包衬、吊架、人孔、快开盖、喷射器、吸铝管、减速机、电机等部件组成。主要特点表现在以下几方面。（1）外形为圆柱状，方便制作、节省材料，与同体积锥桶形真空抬包相比，散热面积小，有利于保温。虽然锥桶形抬包比圆柱状抬包更有利于清理熔渣及残余铝液，但对于大容积抬包清除残渣已较为方便。（2）采用茶壶式浇包的结构形式，铝液从包底浇出，熔渣被挡在包内，撇渣效果好。（3）抬包带包盖，包盖与包体采用活节螺栓连接，固定方便。包盖与包底封头采用平底封头。抬包大修、清渣、砌包衬均可开盖进行，十分方便。考虑到抬包的少量清渣、日常检修以及解决抬包在使用间歇中自身散热的问题，在包盖上设立了人孔。（4）包嘴盖设计成快开的结构形式，包嘴盖与包口管铰接，并采用偏心自锁机构来控制包嘴盖的开启与关闭，使用安全方便。（5）采用喷射器利用压缩空气抽真空吸铝。考虑到电解槽工作时，打壳下料、母线提升等工序均采用压缩空气工作，因此可与电解槽共用一个气源，减少设备配置。喷射器工作原理为射吸式原理。喷射器由工作喷嘴、负压室、扩压管、接收室、消声器等组成，压缩空气通过收缩的喷嘴后，在负压室内形成一束高速射流，吸卷负压室内的空气一起进入扩压管，在扩压管内减速扩压后进入接收室，最后在接收内消音后排出至大气。（6）减速机是抬包的倾转机构，由于抬包容积的增大，自重及盛铝量均增大，抬包的倾转力矩增大，手动倾转费力、效率低而且不安全，该减速机在结构形式设计为手动与电动均可，正常操作为电动，手动为检修和突发事故时用，手动与电动的切换采用爪式离合器，切换迅速方便，安全可靠。该减速机电动为三级蜗轮蜗杆减速，手动为两级蜗轮蜗杆减速，减速比大。技术难点（1）包盖与包体的密封及防变形措施。对于大型吸铝真空抬包，包体直径较大，包盖与包体法兰采用凸凹止口密封，密封件为石棉盘根。由于包盖与包体受热不均以及包体在起吊时的受力不均，容易导致包盖与包体法兰止口错位，从而引起密封不严。对于这个问题，一方面要加强包体与包盖强度，包体与包盖均需加筋，采用厚法兰。另一方面要采用合理的密封方式，可将包盖法兰嵌入至包体法兰内，形成双重止口密封，一旦小止口密封失效，可启用大止口密封。（2）包衬及吸铝管使用寿命。对于小型吸铝真空抬包，由于其直径小、高度低，采用耐火砖砌包衬，其强度足可满足其使用寿命，对于大型吸铝真空抬包，由于其容积大，包衬必需采用浇注料整体浇注，其强度才可满足使用寿命。吸铝管属耗损件,为提高其使用寿命,可采用耐温900以上的耐热铁铸造，并需进行热处理，耐热铁材质中Si含量不可过高，以防止和电解槽中的氟化盐发生化学反应，影响吸铝管使用寿命。（3）转轴位置的确定及倾转力矩的计算。对于大型吸铝真空抬包，由于采用电动操作，从操作安全的观点出发，转轴位置应高于空包和满包的重心。抬包倾转力矩M 包括空抬包包体所引起的转矩M1，以及在浇注过程中由于铝液不断倾出，余留在抬包内的铝液所引起的转矩M2，此外还有转轴与其轴颈的摩擦力矩M3，三者均为转角的函数。M=M1+M2+M3四、实习总结 从中国铝业有限公司参观回来之后，我感触很深。以前的我由于接触社会少，所以对相关的认识了解的很少。我尽我所能去联想，该公司生产的铝会用于何处，想起学校里的餐具，以及各式各样的铝合金门窗等，才明白铝业对我国的经济发展作用是如此巨大。也许其作用远超出我的想像，可能只有走向社会，才能更了解社会。 这一次通过对机械分厂的参观实习，逐渐地感受到我们这一专业所要面对的社会方向和社会需求。机械制造就是要不断的满足工业发展中的一些具体要求。满足其生产的顺利进行。更加方便地、快捷而又安全地完成生产，并且要保证生产的质量。从另一方面看，一个企业的发展也需要有其他的企业来进行互补，这样才能更好地发展进步。 同时，通过对这一次设计课题的深入了解，也使我真正地明白设计的一些关键问题。设计就是要首先明白存在的问题，设计出的产品是用于干什么的，如何进行生产，是否能够保证产品的质量，生产出来之后是否有市场价值，经济效益会如何，或者说是否能满足客户的要求，并且要进行售后服务，以保持与客户的长期合作。这一次实习的时间虽说短暂，可是从中我们看到了许多在学校里学不到的知识，也间接地学习了许多需经多年工作才能领悟到的一些经验。这些都要感谢我们的指导老师以及厂里的领导和员工。我相信，经过这一次实习我会更好地去面对我们这一专业的工作，在将来的工作中，我会更加努力地去学习和创新，做一个出色的专业人才。 五参考文献1. 濮良贵，纪名刚.机械设计.北京M：高等教育出版社，2001.2. 刘鸿文，材料力学M，北京：人民教育出版社，1985。3. 韩向东，机械工程力学M，北京：机械工业出版社，2002。4. 联合编写组，机械设计手册（上中下）S,北京：机械工业出版社，1988。5. 联合编写组，机械设计手册（1-5卷）。S,北京。机械工业出版社，1998。6. 朱龙根，黄雨华。机械设计系统M。北京：机械工业出版社，1992。7. 徐灏等。新编机械设计师手册M。北京：机械设计出版社，1995。 机自071-33 竹怀振 12 题目名称： 真空抬包设计 抬包结构设计，真空度分析 院系名称： 机 电 学 院 班 级： 机 自 学 号： 20070 学生姓名： 竹 指导老师： 王 2011 年 3 月 毕业设计（论文）题目名称： 真空抬包设计 抬包结构设计，真空度分析 院系名称： 机电学院 班 级： 机自071班 学 号： 200700314133 学生姓名： 竹 怀 振 指导教师： 王玮 2011年5月 毕业设计（论文）题目名称： 真空抬包设计 抬包结构设计，真空度分析 院系名称： 机电学院 班 级： 机自071班 学 号： 200700314133 学生姓名： 竹 怀 振 指导教师： 王玮 2011年5月中原工学院毕业设计英文翻译The Development of Continuous CastingContinuous Casting From the Making, Shaping and Treating of Steel by William，McGrawHill Companies, Inc., 2002 The Development of Continuous Casting Continuous casting was developed very rapidly after the Second World War. Steel-producers arc today generally convinced that continuous casting is at least as economical as ingot production and can match the quality of the latter across much of the production spectrum for high-quality steels. Continual development of the technique aimed at improved steel characteristics is leading to increasing adoption of the process in works producing special high-grade steels. The reasons for continuous-casting systems are: (1) lower investment outlay compared with that for a blooming train (mini-steelworks); (2) about 10% more productivity than with conventional ingot-casting; (3) high degree of consistency of steel composition along the whole length of the strand; better core quality, especially with flat strands; high inherent surface quality, leading to savings on an otherwise expensive surfacing process; (4) high degree of automation; (5) friendlier to the environment; (6) better working conditions. Types of Installation The first continuous-casting plants were aligned vertically; however, with larger cross-sections, increasing strand-length, and, above all, with increasing pouring-rates this type of construction leads to unreasonable building-heights. These factors also lead to a considerable increase in the length of the liquid phase which has metallurgical effects. The length of the liquid phase in a continuously-cast strand is determined by the following formula: L=D2/4x2Vc Where D =strand thickness (mm) x = solidification characteristic (mm / min1/2) These values amount to 2633 for the whole cooling length. Vc = casting rate (m /min) Efforts to reduce building-height first led to continuous-casting systems in which molten metal passed into a vertical mould and solidified completely before being bent or where the strand has been in the liquid phase and later to the bow-type installation which has a curved mould and is the system most used today. Vertical systems and those in which the strand is bent when completely solidified have long straight liquid phases and can lead to unacceptably high capital outlay. However, these systems have metallurgical advantages from the point of view of maintenance. A vertical system in which the strand is bent while still in the liquid phase has the advantage that the building need not be as tall as when the strand is bent after solidification; however, the liquid-phase bending system requires higher initial outlay and greater maintenance costs. The bow-type system represents a compromise between the costs of capital outlay and of maintenance and what can be achieved metallurgic ally. Continuous-casting is suitable for the production of almost any cross-section imaginable; square, rectangular, polygonal, round, and oval sections are all available. There are also some instances of preliminary sections for tubes and slabs, blooms, and billets. Sections with a breadth /thickness ratio greater than 1.6 are normally described as slabs. Billet-machines produce square or nearly-square, round, or polygonal cross-sections up to 160mm across. Larger sections and those with a breadth /thickness ratio less than 1.6 are cast in bloom-machines. Billets nowadays normally produced in this way range from 80 x80 to 300 x300 mm, and slabs are 50 - 350mm thick and 300 - 2500 mm wide. Continuous-casting output-rates have risen sharply, especially in the last few years. This is essentially because of increase in the breadth of the strand and in casting rate. The following outputs have been exceeded per section per minute: slabs 5 tones blooms 1 tones billets 350 kg Finally, we should mention horizontal continuous-casting systems which are already used for non-ferrous metals and cast iron and which are being further developed for steel. R. Thieimann and R. Steffen have produced a comprehensive report about the state of development of horizontal continuous-casting systems for producing billets from unalloyed and alloy steels. Horizontal continuous-casting systems have three important advantages over conventional continuous-casting system: (1) low height and cost of building; (2) simple means of protecting the melt against reoxidatioin; (3) no strand deformation because the ferrostatic pressure is much lower. Casting Technique Molten steel is poured from a casting ladle via a tundish into an open water-cooled copper mould. At first the bottom of the mould is closed off by a starting-bar, which then leads transport of the hot strand from the mould into the continuous withdrawing rolls. The strand, which starts to solidify in the mould, passes through a cooling system before it finally reaches the withdrawing rolls, whereupon the hot strand takes over transport. The starting-bar is separated from the hot strand before or after it reaches the parting device. The latter, which may either be a flame-cutter or hot shears, moves at the same rate as the hot strand and cuts it into the lengths required. The purpose of the tundish is to feed a defined quantity of molten steel into one or more moulds. This can be done by using nozzles controlled by stoppers, slide-gates, or other means. The tundish may initially be cold, warm, or hot according to the nature of its refractory lining. Where difficult steels are processed the pouring stream is protected against oxidation between the submerged boxes. The mould not only forms the strand section but also extracts a defined quantity of heat, so that the strand shell is strong enough for transport by the time it reaches the mould-outlet. The mould may be made from copper tube or hard enable copper alloy, depending on the shape and size of the strand to be cast. As a rule, tubular moulds tire used for smaller sections. The interior surface of the mould may be coated with chronic or molybdenum to reduce wear and to suit heat-transfer from the alloy being cast. The mould is tapered to match steel-shrinkage and casting-rate and the type of steel concerned. Moulds used today range from 400 to 1200 mm in length overall, but their usual length is between 700 and 800 mm. The problem of steel adhering to the mould-sides is usually countered by oscillating the mould sinusoidally relative to the strand and by adding lubricant (oil or casting flux in an attempt to cut friction between the mould and the steel. The lubricant, particularly casting-flux, has an additional metallurgical function. The choice of lubricant depends on the qualities required and the casting conditions; it is particularly important that casting-flux should be chosen to match the quality-programme precisely. The level of steel in the mould may be controlled manually or by an automatic system. Either method may be used to keep the level constant or to match the incoming molten steel, i. e. to accommodate variations in casting rate. Manual control is affected via the stopper in the tundish or by varying the output rate. An automatic control system may meter radioactivity or infrared radiation or measure temperature via a probe in the mould wall to determine the steel-level and compensate any changes by actuating the stopper-mechanism (for constant pouring rate) or controlling the speed of the withdrawing rolls (varying casting rate). The type of starting-bar used for continuous-casting depends on the type of installation. Rigid starting-bars can be used in vertical systems, while articulated dummy bars or flexible strip have to be used in bowed installations. The starting bar can be connected to the hot strand in different ways, one is by welding the fluid steel using a jointing element (flat slab, screw, or fragment of rail) which is soluble in the starting-bar; another is by casting the connector in a specially shaped head in the dummy bar in a way that enables it to be released by unlatching. The thickness of the solidified strand shell on leaving the mould depends first of all on how long the steel is in contact with the mould, but it also depends on the specific thermal conductivity of the mould and on the amount of superheat that steel has when it enters the mould. It can be determined with fair accuracy using the following parabolic formula: C=x. T where C is the thickness of the strand shell (mm) x is the solidification characteristic (mm/min1/2) t is the solidification time (min) The solidification characteristic in and near the mould lies between 20 and 26, depending on the operating conditions; for the secondary cooling-area the figure is 29 -33. The thickness of the solidified strand shell on leaving the mould is about 8 10% of the strand-thickness, depending on casting rate. A secondary cooling-area under the mould speeds up completion of the solidification process. The coolant usually is water but a water / air mixture or compressed air is also sometimes used. The secondary cooling area is divided into several zones to suit coolant flow rates. The necessary quantity of water is sprayed over the entire strand by spray-bars. The ferrostatic pressure may be so high in relation to the strand cross-section and the casting rate that the strand has to be supported to prevent buckling. The equipment for this is expensive in plants producing blooms and especially slabs. Process Control For productivity and quality reasons there is a trend in modern steelmaking to transfer time-consuming operations, such as temperature adjustment, deoxidation and alloying, from the furnace to the ladle treatment stations. These treatments are particularly important where the continuous casting process is involved because temperature and composition must closely be controlled. The temperature control of molten steel as it enters the mould needs to be more accurate in the continuous casting process than in conventional casting. Too high a superheat can cause breakouts or a dendritic structure, which is often associated with poor internal quality. On the other hand, too low a temperature may cause casting difficulties due to nozzle clogging and result in dirty steel. The steel temperature in the tundish normally lies between 5 and 20 above the liquids for slab casting and between 5 and 50 for billet or bloom casting. This differential depends on steel grade and, for example, is about 45t for stainless steel slab casting from small furnaces. In order to keep the steel temperature within the prescribed limits during the whole cast, temperature uniformity in the ladle is of paramount importance. Stirring is required before casting in order to destroy any temperature variations in the ladle, and rinsing is sometimes used. The heat is flushed with either nitrogen or argon, injected by means of a porous plug at the bottom of the ladle or through a hollow stopper rod at a separate rinsing station. Control of chemical composition can be performed during vacuum or rinsing treatments. On the basis of the analysis of a sample or of an electromotive force oxygen activity measurement made after homogeneity of the metal is attained, trimming additions can be calculated to ensure correct deoxidation. The best way to introduce trim deoxidants is at a high velocity (powder injection with inert gas, wire feeding or bullet shooting) while stirring the bath. Decreasing the need for alloys by careful exclusion of furnace slag from the ladle simplifies trimming. Vacuum treatment is versatile and useful to achieve for good ladle metallurgy. Low-pressure treatment, however, is the only way to remove hydrogen before casting or to decarburize to extremely low levels. Mould-level control The most vital part of the control of a continuous casting machine is to ensure that the withdrawal of the cast and the partially-cooled billet is such as to keep the liquid level in the mould constant (within a few centimeters). This is done in two ways. (1) The tundish is weighed and the rate of feed to the tundish from the ladle varied automatically to keep the total tundish weight constant. In this way the rate of feed from the tundish is constant. (2) The rate of withdrawal of the partially cooled billet is controlled so as to keep the level of liquid steel in the mould roughly constant. In the early days of continuous casting the level of the top of the liquid steel in the caster was maintained constant by an operator viewing it and adjusting the tundish stopper accordingly. It is now normal to have a means of finding the level using a measuring instrument and automatically adjusting the level. The table below lists several ways in which the level is detected. Two of them, the gamma-ray (radioactive) and the infrared methods will be described in detail. The operation is self-evident from this diagram. The infrared device was developed in order to avoid the use of powerful radioactive isotopes. The detector views the junction of the metal level with the back wall of the mould. As the metal level rises within the field of view more radiation is received by the single photocell and an increased output is obtained. Special provisions are made to compensate for interruption of the view of the metal. The photocell unit receives the infrared radiation and provides an electrical signal to the control unit, which is in turn connected to the operators unit and the casting-machine drives. The operator can select automatic or manual control and he receives indication of the operating rod from signal lamps. The radiation emitted from the liquid steel is collimated through a slotted mask and then focused on to a photo detector by a cylindrical lens. The light is filtered to eliminate radiation below a wavelength of 1 mm, so reducing interference from ambient light and oil flames. The entire system is duplicated within the had with two detectors and two fit beams normally arranged to view either side of the steel stream. It is possible to adjust the spacing between the two areas seen by the photocells by changing the slot spacing in the mask. There are three photo detectors fitted for each channel: the first measures the metal level using the beam described above; the second receives no light and enables temperature drift compensation; and the third looks through the slot at a small region above the normal metal level and between the main beam and the metal stream. Its purpose is to detect the metal stream if it wanders from a central position and is in danger of interfering with the main beam. The balance between the two main beams and the threshold level of the stream detectors can be adjusted with small potentiometers mounted in the back of the unit. The level signal detected by each channel is fed, after temperature compensation, to a simple circuit which selects the largest signal. Thus the unit always controls on the higher of the two level signals. If the stream-sensing photocell sees that the teeming stream is moving towards the detection beam it blocks the signal and the unit switches to control on the other channel. There is an additional feature that if both channels are blocked together, for example by a fan-shaped metal stream, the unit switches to a memory, equivalent to the fast detected metal level, and prevents a sudden loss of control. As the memory decays the metal level gradually drops allowing the operator ample time to intervene. The unit gives a smooth transition from manual to automatic control by preventing automatic operation if there would be a large jump in withdrawal speed at changeover. It does not provide bumpless transfer when changing from automatic to manual. There is also protection against changing to automatic when there is a cable fault. The control system receives the chosen level signal and, following proportional and integral action, outputs a voltage signal directly to the withdrawal drive unit. The drive creates a withdrawal speed proportional to this voltage signal. Benefits of Continuous Casting Sequence of Operations-prior to the development of continuous casting, ingots provided the only starting material in wrought-steel products. The typical sequence of operations from the steelmaking furnace to the rolling mills was: (1) Tapping liquid steel into ingot molds. (2) Transferring ladle to pouring platform and teeming liquid steel into ingot molds. (3) Transferring filled molds to stripping area for ingot removal. (4) Transferring and charging ingots into soaking pits and heating to rolling temperature. (5) Removal of heated ingots from soaking pits and transfer to primary mill for rolling into semi-finished shapes. (6) Transferring semi-finished shapes to subsequent rolling mills. Using continuous casting, the following much shorter sequence of operations is required: (1) Tapping liquid steel from a steelmaking furnace into a ladle. (2) Transferring the ladle to a casting platform and continuously casting liquid steel into semifinished shapes. (3) Transferring the semi-finished shapes to rolling mills. The benefits derived from the shorter sequence of operations provided the main impetus for the adoption of continuously casting; increased yield; improved product quality; energy savings; less pollution; and reduced costs. Yield Increased yield from liquid steel in the ladle to the semi-finished rolled shape results from a reduction in scrap generation in three areas: the primary rolling mill; the pouring operation; and ingot heating. The major contribution to the improved yield is the absence of crop losses corresponding to the ingot top and bottom location when an ingot is rolled in the primary mill. Reduction in yield losses associated with the pouring operation includes short ingots, ingot butts and general pit scrap. Scaling losses associated with ingot heating in the soaking pit are also avoided. Quality Metallurgical quality improvements include less variability in chemical composition and solidification characteristics. In addition to improved segregation characteristics of carbon, sulfur and alloying elements across the section of a continuously cast shape, there is also less variability along the length of the cast shape. (In casting a heat into ingots there are a multitude of individual ingots each with their associated vertical segregation and structural variability, whereas a continuous cast strand is not only as one ingot but also an ingot which has less variability in a vertical direction.) In modern continuous casting, the surface quality of the cast shape is superior to that of a semi-finished rolled shape with respect to surface defects such as seams and scabs, and, consequently, conditioning requirements and yield losses are minimized. A majority of continuously cast steels can be further processed without any conditioning. Thus, an improved, more uniform finished product can be obtained with fewer internal and surface defects. Energy Energy savings are achieved with continuous casting because of the elimination of the energy-consuming steps in the ingot process. These include fuel consumption in soaking pits and the electric power requirements for operating the primary rolling mills. Energy is also indirectly saved through the increased yield which requires the production of less raw steel for a comparable quantity of semi-finished product. !n addition to these savings, a practice in which hot continuously cast shapes are charged directly into a heating furnace in the finishing mills is receiving attention. Thus the sensible heat of the cast product is conserved. Pollution Continuous casting reduces pollution through the elimination of ingot-processing facilities such as soaking pits. Costs Both capital and operating costs are reduced with the installation of continuous casting in comparison with ingot processing. Capital assets savings are attributable to the elimination of the additional equipment required for ingot processing. Operating cost savings are primarily the result of lower manpower requirements and higher yields. Steelmaking Steelmaking practices for continuously cast steels are, with certain exceptions, similar to those employed for ingot steels whether produced in the electric furnace or basic oxygen converters. There are two major exceptions: (1) temperature control; (2) deoxidation practice. Temperature Control Temperature control is more critical than in ingot production. The tapping temperature is generally higher to compensate for heat losses associated with the increased transfer time to a caster and must be maintained within closer limits to avoid mold breakouts, if the temperature is too high or premature freezing in the tundish nozzles, if the temperature is too low. Casting temperature can also affect the crystallization structure of the cast product. Optimum structures are developed with low superheats which should be uniform throughout the entire cast. To meet this objective, temperature homogenization practices are employed. One practice widely employed is to stir the metal in the ladle by the injection of a small quantity of argon through porous plugs located in the bottom the ladle, or a lance which is lowered into the ladle. Dcoxidation Continuously cast steel must be fully deoxidized (killed) to prevent the formation of blowholes or pinholes at or close to the surface of the cast product which cause seams in subsequent rolling operations. Depending on the grade of steel and product applications, either of two practices is employed: (1) silicon deoxidation with a small addition of aluminum for coarse grain steels; (2) aluminum deoxidation for fine grained steel. Silicon-killed steels are easier to cast than aluminum killed steels because deposits of alumina in the tundish nozzle, which cause nozzle blockage, are avoided. For high-quality products, it is becoming a common practice to employ a ladle refining practice prior to casting. The principle and process of continuous casting连铸连铸的发展 二战之后，连铸发展非常迅速今天钢铁生产者普遍相信连铸至少和模铸一样在经济上是合理的，并且能与大部分高质量钢的生产系列相匹配。这项技术不断开发的目的在于改善钢的性能，这促使生产特殊高级钢时企业对其生产工艺过程不断进行调整。使用连铸系统的理由有： (l）和初轧机组（小型车间）相比，降低投资费用； (2）和传统的铸锭相比，提高10%的生产能力； (3）在整个铸坯长度上钢的成分较均匀；中心质量比较好，尤其是板坯；高的内表面质量，比其他需要昂贵的清理表而的工序节省； (4)高度的自动化； (5)益于保护环境； (6)较好的工作条件设备类型 首台连铸机是立式连铸机，可是，由于横断面的增大，注流长度的增加，而且主要是随着浇注速度的增加，这种设备迫使厂房建筑高度增加。这些因素也导致了具有冶金影响的液相长度的大大增加。连铸坯的液相长度由下式决定： L=D2/4x2Vc 这里，D=铸坏厚度(mm） x=凝固特征系数(mm/min1/2） 对于全部的冷却长度这些值达到26-33。 Vc=拉坯速度( m分） 为了减少厂房高度，首先研制出将钢水倒人立式结晶器中，并且在弯曲之前让钢水完全凝固的连铸系统，或弯曲时铸坯仍处在液相，这种系统随后发展为弧形结晶器，这是目前最常用的方法。立式连铸机和那些铸坯在完全凝固时被弯曲的连铸机都有一个长直的液相，这大大增加了成本。 然而从维修的角度看，这些系统有冶金学优点。铸坯内部仍为液相就进行弯曲的连铸机比完全凝固后再弯曲的立式连铸机更好，它不需要修建与立式连铸机一样高的厂房。然而，液相弯曲系统要求更高的初期投资和更大的维护费用。弧形连铸机是考虑了投资费用和维护费用的折衷产物，而且可以在冶金上实现。 连铸适合于生产任何横断而的产品：正方形的、长方形的、多边形的、圆形的、椭圆形断面都可以。也有些基本断面的例子，如管坯、板坯、大型坯、方坯。断面宽厚比大于1.6的铸坏通常称为板坯。方坯铸机生产正方形或近于方形、圆形或多边形断面，断面尺寸达到160mm的产品。较大断面或那些宽厚比小于1.6的产品用大型坯铸机生产。现在80 x 80到300 x 300mm的方坯以及50-350mm厚300-2,500mm宽的板坯都用这种方式生产。 连铸比已经迅速增长，尤其在最近几年。这本质上是铸坯宽度和拉坯速度的增加。每个注流每分钟生产出的产品已超出了如下数据：板坯 5吨 大型坯 1吨 方坯 350kg 最后，我们应该提到水平连铸机，它已经应用于有色金属和铸铁的生产，而且可以进一步开发用于钢的生产。R. Thielmann和R. Steffen针对用水平连铸机生产非合金钢和合金钢方坯的发展状况提出了一份综合报告。水平连铸机比传统连铸机有如下三个显著优势： (1)低的建筑高度和建设费用： (2)防止钢水二次氧化的方法简单； (3)由于钢水静压力非常低，没有铸坏变形。 浇铸技术 钢水由浇注大包注入中间包后流人敞口的水冷铜结晶器。首先结晶器底部用一个引锭杆塞住，然后由它将热的铸坯从结晶器拉出进人连续拉辊。铸坯从结晶器开始凝固,然后经过冷却系统，到达拉环辊，在拉辊中继续传送。引锭杆在进入切割装置之前或之后与铸环分离。切割装置可能是火焰切割机或热切割机，其行进速度与热铸坯相同，它将热铸坯切割成所需长度。 使用中间包的目的是将确定的钢水量分流到一个或多个结晶器。这可以通过使用塞棒、滑动水口或其他力法控制的水口来实现。中间包的初始状态根据其耐火衬材料的不同可以是冷的、温的或热的。对于要求严格的钢使用浸入盒保护钢液注流以防止其氧化。结晶器不仅形成铸坯断面而且吸收一定的热量，使铸坯到达结晶器出口时坯壳有足够的运送强度。依据所铸铸坯的尺寸和形状，结晶器可以用铜管或硬质铜合金制成。按惯例，管状结晶器用于较小断面。结晶器的内表面可以使用铬或钼镀层以减少磨损并且适合于浇铸过程中从合金传热。结晶器的锥度是为了与钢的收缩、拉速和钢种匹配。现在使用的结晶器长度约为400 - 1,200mm,但通常在700 - 800mm之间。结晶器壁粘钢问题通常通过按正弦规律振动结晶器和加入润滑剂（油或连铸保护渣）以消除结晶器与钢水之间的摩擦加以解决。润滑剂，尤其是连铸保护渣，有一个附加的冶金功能。润滑剂的选择取决于所要求的质量和连铸条件；尤为重要的是所选择的连铸保护渣必须严格与质量工艺匹配。 结晶器内钢液面可以人工控制或进行自动控制，两者中任何一种都可用于保持液面稳定或满足输人的钢水量，如与拉坯速度的变化相适应。人工控制通过调整中间包塞棒或流出速率实现。自动控制系统则可以通过放射测位仪或红外线放射仪或用安装在结晶器壁的测温探针测温来确定钢液面，并且通过操作水口塞棒机构（对于稳定流速）或控制拉辊速度（变化拉速）来补偿任何钢液面的变化。 连铸中使用的引锭杆类型取决于连铸机的类型。立式连铸机可以使用刚性引锭杆，而组合式的或灵活式的引锭杆必须用于弧形连铸机。引锭杆与铸坯可以采用不同方式连接，一种是用连接部件（平板、螺钉、碎条钢）将钢液与引锭杆焊接在一起；另一种是在引锭杆头部铸造一个特殊连接头，它能使引锭杆像打开扣环那样进行脱锭。 铸坯离开结晶器时的坯壳厚度首先取决于钢液与结品器的接触长度，它也依赖于结晶器的具体导热系数
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