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1、精选优质文档-倾情为你奉上附件1热轧工艺该轧机的主要功能是将半成品钢重新加热到接近其熔点， 然后通过由共计7.7万的大功率连续滚动驱动马力发动机带动的12道连续轧制使钢板变得更薄更长，最后卷曲被拉长的钢板以运输到下一道工序。热轧板卷的重量高达30吨至30”和74”。 将8至9英寸厚、36英尺长的钢板被卷成薄如16英寸和1 / 2英里长的带钢。线圈由两个内径（眼睛）为30”卷取机，外径上限分别为72”和74” 分别与850和1000磅每英寸宽（PIW）相对应的两个卷曲机产生。该厂为每一个CSI提供售后业务，以及负责运输成品给CSI顾客。大部分材料是由一种自动线圈处理系统运出轧机，通过运输线被分批
2、运往轧机的东侧，直到它被冷却到足以载入铁路车辆。 加热炉 对于热轧工艺至关重要的是它的步进梁加热炉，国家的最先进的设备，现在优于三老一辈（推车）式炉。其额定生产速度为每小时270吨，效率和与板温一致的方面得到改善以使生产率能比计划提高25。把这些钢从室温加热到22002400摄氏度需每天消耗约10立方米的天然气。就像板材是按订单分配，日程安排是规定的，材料被热轧厂最西端的板厂的铁路小车和起重机分批运输。在一条轧制线上，每一放一个轧板。因为轧板被放置在南侧加热炉的控制门的前边，所以其规模和重量是确定的。当炉内的空间足够，大型电镀机械推拉臂能够将板材移到炉内。一旦进入内部，板材由大约8英尺长的炉板
3、支撑，它是通过冷却水的耐火涂层管也被称为滑轨。为了降低钢板残留的冰点（滑板标记），滑板间距变化大约为熔炉内部空间的三分之二。两个独立的滑轨装置，一个固定，一个运动，轮流支撑钢板当它在炉内运动时经过一个由一对大型液压缸提供能量的机架。该炉内部的宽是389”，从地面到天花板有15英尺，142长。它分为管制区内的温度：预热，顶面和底，加热，顶部和底，浸泡，顶和底，东和西。预热和加热区燃烧一种天然气的混合物，同时通过在熔炉侧边的大量燃烧器预燃空气，加热钢板的上部和底部到接近其排气温度。大部分钢的预热是通过热废气经过钢板直达控制门的方式达到的。留在废气中热量在这些大规模的热交换器中将引入的空气预热到10
4、00。相反地，在加热区，钢板主要是通过加热炉壁加热。在浸泡区，很多小型燃烧器寻求保持各区域间温度的统一，平衡钢板冷点。耐火分隔有助于身体区分区域，全炉内的热电偶温度传感器与自动燃烧控制系统相互作用，以保持每个区域的目标温度。复杂的计算机模型计算出目标粗轧机出口温度，以获得一个炉排放（排气）的目标温度。在连续的基础上通过炉内的每片钢板的厚度来估计剖面温度，计算机帮助操作者选择产品等级和能最大限度地将钢板加热到尽可能接近目标温度的生产区设定点。轧制过程开始后，当钢板离开粗轧机时它的温度会反馈给熔炉，更新计算机模型并通知加热器达到温度的均匀性。当板坯到达熔炉尽头的卸载门，并且该计算机已经确定该钢板已
5、经被充分加热，门打开了，大量的提取手臂到达钢板的的下方，把它举起使之远离滑轨的支持，并把它拉出熔炉。东部和西部的提取器能够一次独立移除两控钢板，同时提取较长的钢板。具有强热的钢板被放置在滚转机上被带到粗加工工序。除鳞 在退出加热炉之后，钢板经过一个除鳞单元，外壳采用了两对喷雾头，能够用1500的压力冲击具有强热的钢板以消除1/8英尺厚的在富含氧气的加热炉内在钢板表面形成的氧化铁层。除垢后不久，一个（相对）小2-hi轧机称为能减少板坯大约1英寸的厚度,来打破遗钢板上遗留下来的鳞片。在进入下一个工序前，扫除喷雾器将附着在钢板表面的松动的鳞片进行清理。转移条多在粗轧过程中除鳞两次，前夕的第三次或是最
6、后一次轧制操作，以消除其又重新长出的鳞片在超过三分钟的时间里或以便能花费在粗轧过程中。粗加工 粗轧机是有六个独立的粗轧机机架组成，其中最后的四个包含了体积较小的称为修边机的立式轧机。在加热炉内加热直到焕发明亮的橙黄色的钢板被轧制，一次经过一个站来生产所谓的转移条以适应精轧。高压水射流能清理沿途经过的钢板表面的氧化铁层或是鳞片。在转移条从粗轧机最后一站出来的时候，其主要边缘的厚度被估计。同样的，有高温计测量板条从头到脚的剖面温度，并且一种特殊的照相机可以给板条的两端拍照。依据被轧制产品所要达到的长度、宽度和等级，板条在离开最后一道轧制线的平均温度一般会达到19002100。此数据期望在精轧过程中
7、被收集。计算机能立即计算穿过这6个连续轧制钢板的线程的速度和差距。重型粗轧机有135”宽的辊子，以便能卷曲较宽的一面（作为第一次轧制时的称谓）使钢板更宽。一个5000马力的电动机驱动直径为42”的工作辊通过28：1的齿轮来减少钢板的厚度高达”。最后的四个轧制装置每个都包含一个修边装置来控制钢板的宽度，并将其轧制为5到6英尺厚，根据客户所要求的宽度、尺寸和钢种其厚度可在此基础上上下浮动公分。如前所述，第三和第五粗轧机组都有操作压力为1500的高压除鳞装置。这些独立的粗轧机组放置的间距逐渐变大以适应转移条在被轧制的越来越薄时的长度。裁剪 因为一个方头段对于能正确的经过精轧工序是至关重要的，并且一个
8、不平整的尾部会挫伤工作辊表面或是导致今后的生产过程的线程问题。几乎每一个转移条的头部和尾部末端都会通过一对具有大剪刀片的钢鼓被裁剪并增加其长度。在钢板以100的速度在辊子上滑动时，传感器可检测其位置和速度以便测定裁剪的时间来优化裁切的数量；由于转移条的厚度超过一英寸，裁剪长度每增加一英寸将废弃1530磅。精加工 规格的热轧机包含六个能够降低转移条的厚度到根据顾客或是下一道工序的要求所得规定尺寸的精轧机组。轧制速度被设定为能允许在最后一道工序以15001600的精轧温度完成最后的压下量，并达到特定的机械性能。到现在为止，钢板被轧制成长达200英尺的平板。与粗轧相比，精轧是将转移条进行连续压轧，这
9、就意味着每一个板条将一次性通过六个轧制机组。热钢在精轧过程中被拉伸的时候是相当脆弱的，所以必须及时用一个低标准来控制为了避免将钢板被撕裂。在精轧操作之前，转移条的头部和尾部将被剪裁成方形，以帮助确保正确的线程。最后两步的除鳞操作是为了清除在粗轧过程中新生成的鳞片。一旦转移条穿梭在每对连续的辊子上，在电控枢轴上的自由转动的辊子能使吸引钢板的底部来检测各个精轧机组间的张力。按需要作出调整，以确保钢板能够正确通过每个辊子不会通过不正常循环、拉伸和折叠过度或撕裂。每个辊子的位置能反馈到精轧机的先进自动化系统，以及能检测辊子所受力，通过X射线测量带钢厚度的信息，顺利工作以调整滚动速度和差距，保持稳定的带
10、钢轧制必要的厚度尽管每一个转移条所呈现的温度不同。层流冷却 对于冶金学上的热轧钢材性能至关重要的是卷曲温度，线圈会从这个温度冷却到室温，而这个过程的完成需要三天的时间。这基本上相当于一个热处理退火， 在从9英寸厚减少到规定尺寸的过程中所施加在钢板上的压力使线圈得以冷却来缓解自己。虽然钢是在重结晶过程中不断热轧，削减厚度有时超过99，并采取相当于钢的不到10分钟的压力;卷取温度由产品的冶金性能来指定以利用操纵这些应力学性能获得最佳的机械性能。 由客户进行激光切割的售出的经过热轧工序、热轧浸泡和热轧涂油的产品是在相对较高的温度下进行连续松弛以便使从线圈上切割下来的部分能够平坦放置，即使是在残余应力
11、已经自行消退的情况下。相反的，在相对凉爽的温度下卷曲钢板能使钢种的物理性能保持一个较高的内应力水平，限制了由自身和相互晶体之间形成的晶体和碳化物的尺寸；这些因素有助于使钢板在热轧的精轧阶段获得较高的应力。400的冷钢在以2700的速度经过该系统的时候需要大量的水，所以总共有152个由自动化系统控制的喷雾头以层流的形式来喷洒在钢板的顶部和底部。计算机以板带行进的素的和所要达到的目标轧制温度为基础来估计需要多少水来冷却钢板，并且估计的准确性是由在后卷曲前面的高温计来确定的。为了调整所需要的喷雾器的数量，计算机可以控制喷雾器的开和闭来调整线程的长度来满足目标温度。由于要加快完成轧制过程，一旦后卷曲使
12、钢板继续维持最终温度，当钢板被轧制时为了弥补它在运行出平台所减少的时间越来越多的喷雾器被激活。整个连轧机泵每分钟输送高达75000加仑的水来冷却冷轧带钢、加热炉滑轨、卷取单元和除鳞装置。所有的水是在除鳞系统和污泥收集系统中循环的，通过层流冷却系统，然后回到两个专门的冷却塔中的其中之一。卷取 CSI的热连轧机目前的配置依赖于两个卷取机。两个卷取机之间存在细小的差异，但是两个可操作卷取机都是以一对能抓住钢板头部和尾部并在行进和返回轧机的过程中施加张力的夹送辊开始。它的头部在出入口到与卷取机相连的30”心轴处有一个倾斜，并引导与输送带相连的驱动辊芯轴周围的气动。一旦钢板的头部一直缠绕在心轴上，板卷开
13、始在心轴上建立并迫使远离包装卷。一旦钢板的头部被抓住或者是摩擦力和防止打滑的张力组织钢卷相对于心轴滑动，驱动轴会使日益增长的钢卷松开。在钢板的尾部完成最终轧制后，夹送辊继续保持后张力以防止钢卷松开；在钢板的尾部被拉出夹送辊前，驱动辊一直在运作。具有液压线圈的小车运动到板卷的下方，然后上升到支持线圈的体积，将板卷从心轴上拿走并把它放置在能运输到标记和自动打捆机程序的位置。板卷处理 板圈被具有液压线圈的小车从卷取机上取下放置在洞内的平台上，在这两个能来回运动的步进梁中的其中之一会将板卷放置在能被鉴定和捆扎的位置。因为产品仍然很热以至于适用于使用能在整个工厂辨别板卷的纸质标签，一对镀锡薄铁皮采用激光
14、刻录鉴别信息在不锈钢上，被亲切的称为牌照。在板带被应用前这些都是准确焊接在钢卷外部的。钢板以前是以供应商的连铸机的压力和剪切系数来区分，现在被一具有六位字母数字代码的特殊辊子条码来区分。第二辆具有液压线圈的小车将板卷从打捆机中取出送往轧机外的旋转体中，这个旋转体能够缓慢旋转板卷90，另一辆小车能够将板卷送往自动升降机。两个以上（高速）的线圈车和另一辆升降机能够携带板卷完成它的行程，要么送往能把它送往热轧最终工序的输送带，要么送往冷却池。总之，自动化系统采用10个独特的电动液压装置，每一个依赖于多个传感器来运输90的热轧带钢产品到下一场地，在那里下一个操作将被执行。附件2The Hot Roll
15、ing ProcessThe primary function of the Hot Strip Mill is to reheat semi-finished steel slabs of steel nearly to their melting point, then roll them thinner and longer through 12 successive rolling mill stands driven by motors totaling 77,000 hp, and finally coiling up the lengthened steel sheet for
16、transport to the next process. The Hot Mill rolls slabs weighing up to 30 tons between 30” and 74”. Steel slab 8 to 9 inches thick and up to 36。feet long is rolled into strip as thin as 1/16 inches and up to a half-mile in length. Coils are produced with a 30” inside diameter (eye) on one of two coi
17、lers, with outside diameter limitations of 72” and 74”, corresponding to850 and 1000 pounds-per-inch-width (PIW), respectively. The mill supplies coil for each of CSIs remaining operations, as well as a finished product for shipment directly to CSIs customers. Most material is transported out of the
18、 mill area by an automated coil handling system, though some skelp for the Pipe Mill is staged toward the east end of the mill bay until it is cool enough to load onto rail cars. Reheating Critical to the Hot Strip Mill is its walking-beam reheat furnace, state-of-the art equipment that replaced and
19、 now outperforms three older- (pusher-) style furnaces. Nominally rated to produce 270 tons-per-hour, improvements in efficiency and some sacrifice in slab temperature uniformity enable extended production。rates 25% above design. Heating this much steel from room temperature to 2200-2400 degrees Fah
20、renheit consumes around 10 million cubic feet of natural gas each day. As slabs are assigned to orders, schedules are written and material is staged with rail-cars and overhead cranes in the slab yard at the west end of the Hot Strip Mill. Slabs are placed, one at a time, on a roll line. The slabs d
21、imensions and weight are confirmed as it is positioned in front of the charge door on the south side of the furnace. When space is available in the furnace, large electro-mechanical pusher armsengage to move the slabs into the furnace. Once inside, the slabs are supported about eight feet off of the
22、 furnace floor by water-cooled, refractory-coated pipes called skids. To minimize the cold spots (skid marks) left in the slab, the skid spacing changes approximately two-thirds of the way through the furnace Two independent sets of skids, one fixed, one walking, take turns supporting the slab as it
23、 is walked through the furnace by a massive sub-frame energized by a pair of large hydraulic cylinders. The interior of the furnace is 389” wide, fifteen feet from floor to ceiling, and 142 long. 8 It is divided into eight zones for temperature control: preheat, top-and-bottom; heating, top-and-bott
24、om; and soak, top-and-bottom, east-and-west. The preheat and heating zones combust a mixture of natural gas and preheated combustion air with massive burners on the side walls of the furnace, both above and below the skids, to heat the slab nearly to its discharge temperature. Much of the preheating
25、 of the steel is achieved by the hot exhaust gases rushing past the slabs on the way to the recuperators above the charge door. Whatever heat is left in the exhaust gases preheats the incoming combustion air to over 1000 F in these massive heat-exchangers. Conversely, in the heating zone the steel i
26、s primarily heated by the glowing-hot furnace walls. In the soak zone, numerous smaller burners seek to maintain a uniform temperature within the zones to equilibrate any cold spots in the slabs. Refractory dividers help to physically distinguish the zones, and thermocouple temperature sensors throu
27、ghout the furnace interact with the automatic burner control systems to maintain the target temperatures in each zone. Complex computer models calculate the targeted roughing mill exit temperature to obtain a furnace discharge (drop-out) aim temperature. Estimating the temperature profile through th
28、e thickness of each slab in the furnace on an ongoing basis, the computer aids the operator in selecting the production rate and zone set-points that will maximize production of steel slabs uniformly heated to as close to the target temperature as possible. After the rolling process begins, as the s
29、teel exits the roughing mill, its temperature is fed back to the furnace, updating the computer models and informing the Heater as to the temperature uniformity. When the slab reaches the discharge door at the exit end of the furnace, and the computer has determined that the slab has been sufficient
30、ly heated, the door opens and massive extractor arms reach beneath the slab, lift it off of the skid supports, and draw it out of the furnace. The east and west extractors can act independently of one another to remove double-charged slabs one-at-a-time, or in conjunction to extract longer slabs. Th
31、e intensely hot slab is placed on a roller table which carries it into the roughing mill. Descaling After exiting the reheat furnace, the slab passes through a descaling unit, an enclosure employing two pairs of spray headers that blast the intensely hot slab with 1,500 psi pressurized water to remo
32、ve the 1/8-inch thick layer of oxidized iron that forms at the surface of the slab in the oxygen-rich atmosphere of the reheat furnace. Shortly after descaling, a (relatively) small 2-hi rolling mill called a scalebreaker reduces the slabs thickness by about one inch to break up any scale that remai
33、ns. Just before the next reduction pass is taken, sweep sprays clean away any loosened scale that remains on the slab surfaces. The transfer bar will be descaled twice more during roughing, immediately prior to the third and to the last rolling operation, to remove the scale that has grown back over
34、 the three minutes or so that it spends in the roughing mill. Roughing The roughing mill is made up of six independent rolling mill stands, the last four of which incorporate small vertical rolling mills called edgers. Slabs heated in the furnace until they glow bright orange-yellow are rolled throu
35、gh one stand at a time to produce so-called transfer bars suitable for finish rolling. High-pressure water-jet nozzles clean the oxidized iron, or scale, from the surface along the way. As the transfer bar exits the last roughing mill stand, the thickness of the leading edge of the bar is estimated.
36、 Similarly, a pyrometer measures the temperature profile of the bar from head to tail and a special camera photographs both ends. Depending on the gauge, width, and grade of the product to be rolled, the average temperature of the bar as it exits the last roughing mill normally ranges from 1900 to 2
37、100 Fahrenheit. This data is collected in anticipation of finish rolling. Computers immediately begin calculating the speeds and gaps for threading the six finishing mills, which will roll the steel in tandem with one another. The workhorse roughing mill has 135” wide rolls for rolling broadside (as
38、 the first roughing mill is commonly called) to make a slab wider. A 5,000 hp motor drives 42”-diameter work-rolls through 28:1 gears to reduce the slabs thickness by as much as 2-”. The last four roughing mills each incorporate edgers for width control and roll the bar from five to six inches thick
39、 incrementally down to around an inch and a quarter, depending on the customers ordered width, gauge, and steel grade. As mentioned previously, the third and fifth roughing mills each have high-pressure descaling headers operating at 1,500 psi. The individual roughing mills are spaced increasingly f
40、urther apart to accommodate the lengthening of the transfer bars as they are rolled thinner and thinner. Cropping Because a square head-end is critical to properly threading the finish mills and the downcoilers, and because an uneven tail can bruise work-roll surfaces or cause threading problems for
41、 the next production process, the head- and tail-ends of nearly every transfer bar are cropped by a pair of large steel drums each with a shear- blade extending along its length. With the bar crawling along the roller table at around 100 fpm, sensors detect its position and speed in order to time th
42、e crop shear drums to optimize the amount cropped; since transfer bars are over an inch thick, each extra inch of crop-length scraps another 15-30 lbs. Finishing CSIs Hot Strip Mill includes six finishing mills, which reduce the thickness of the transfer bar down to the gauge required by the custome
43、r or the next process. The rolling speed is set to allow the last stand to perform the final reduction at the finishing temperature, between 1500 to 1650F, specified to reach certain mechanical properties. By now, the steel has been rolled into a flat bar as long as 200 feet. In contrast to the roug
44、hing mills, the finishing mills roll the transfer bar in tandem, meaning each bar will be rolled through all six stands at once. The hot steel is quite fragile as it is rolled and tension between the finishing mill stands must be closely controlled at very low levels in order to avoid stretching or
45、tearing the strip. Prior to the finish rolling operation, the head- and tail-ends of the transfer bar will be sheared to square them up, helping to ensure proper threading and tail-out. A final two-stage descaling operation is performed to clean off the scale that has grown on the bar during roughin
46、g. Once the bar is threaded between each successive pair of mills, a free-turning roll on an electro-mechanical pivot called a looper roll engages the bottom of the strip to monitor the tension between the stands. Adjustments are made as necessary to ensure the strip threads properly through each of
47、 the mills without looping up and folding over or stretching and tearing apart. The position of each roll is fed back to the finishing mills sophisticated automation system which, along with information from the load cells that monitor rolling force and from the X-ray gauge measuring final strip thi
48、ckness, work to smoothly adjust the roll gaps and speeds to maintain stable rolling of strip to the necessary thickness in spite of the temperature variations present in every bar. Laminar Cooling Metallurgically critical to the properties of hot-rolled steel is the coiling temperature, as the coil
49、will cool from this temperature to ambient over the course of three days. Essentially a heat treatment comparable to annealing, the stresses imparted to the steel during reduction from nine inches thick down to ordered gauge are given the opportunity as the coil cools to relieve themselves. Though the steel is continually recrystallizin