棒线材φ450轧机的设计（全套含6张CAD图纸）
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棒线材φ450轧机的设计（全套含6张CAD图纸）,线材,450,轧机,设计,全套,CAD,图纸
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Vibration analysis of stand F2 of Wheeling-Pittsburghs 80-in.hot strip mill In the hot strip mill, the demand for quality hot band is on the rise. Physical and metallurgical properties, and surface appearance are concerns shared by maintenance, production and quality control personnel. A steel company can no longer just produce tons. Quality tons must be produced on schedule and at a competitive price. To accomplish this objective, all equipment must be functioning properly, tuned and maintained at the highest possible levels. Wheeling-Pittsburghs 80-in. hot strip mill began rolling operations in Oct. 1965. The major equipment suppliers were Blaw-Knox for mechanical equipment and Westing-house for the electrical components. Each of the finishing mill stands is powered by two 3000-hp motors.As long as the mill has been operating, a low pitch, loud rumble had been detected when rolling certain types of products, eg, thinner gage, HSLA and hard grade products. The rumble usually occurred at stands F1 or F2. it was reported that the rumble was intermittent in occurrence and intensity over the years.As enhanced quality and cost effectiveness are a major objective of Wheeling-Pittsburgh, tuning the equipment, both electrically and mechanically, has become critical. With in-electrically quality awareness, the rumble condition became increasingly important because of its effect on strip quality as well as the costs associated with frequent roll changes requires to maintain strip quality.Prior to the study by Eichleay, the rumble, caused by mill vibration, had grown in intensity and appeared to occur primarily at stand F2. Once occurring, the surface of the strip exiting stand F2 and F3 deteriorated rapidly. This, in turn, would cause surface problems in subsequent coils and require a premature roll change. This, in turn, would cause surface problems in subsequent coils and require a premature roll change. This change takes approximately 15 to 20 min to complete.When the rumble was detected in the mill, it was also observed that the drive spindles on stand F2 would generate excessive heat in the roll end adapter. Cooling water had to be applied to prevent overheating and cooking-out of the lubricant. In 1986 and early 1987, extensive testing and inspection were conducted on the spindles. Machining problems were considered as well as mill alignment. A better lubricant was also tried with only minor benefits.In may 1987, while working on different problems on the mill, Eichleay was made aware of the intermittent rumble/vibration problems on stand F2. An engineering study was undertaken with the following objectives: Analyze and establish the cause of vibration in stand F2. Establish or design methods to avoid or reduce vibration to acceptable levels.The analysis and solution to the vibration problem together with recommendations and a revised hot strip mill maintenance practice are the subject of this article.VIBRATION ANALYSISTorsional amplification factor (TAF), frequently the cause of vibration in hot mills, was initially considered. However, it was rejected because TAF is a transient phenomena that occurs when a bar first enters of leaves the roll bite. In the Wheeling-Pittsburgh situation, there was no vibration when the bar first entered the stand. The vibration occurred as the mill accelerated, starting softly and quickly building to a maximum. In addition, TAF dose not explain the marking that occurs on the strip. Only fluctuations in the rolling force could produce the observed patterns that extend across the full width of the strip.It was hypothesized that the vibration was due to a source of periodic excitation that was close to the natural frequency of the mill stand. Further, the excitation source had to be extremely powerful to maintain such a strong vibration, particularly when the damping properties of the product rolled are taken into consideration.To isolate the source, the following program was established:l A modal vibration analysis of the mill stand using finite element analysis.l Field observations and measurements on the mill to establish vibration frequency and magnitude.l A drive train analysis to determine if any rotating components could produce periodic driving forces capable of starting and maintaining the vibration.l Data analysis to determine any correlation between various factors.Finite element analysisTo establish the natural frequencies and mode shapes of stand, the mill stand F2 and roll system was analyzed using the finite element computer program A finite element model of the mill stand was constructed. Due to symmetry, only one half of the stand had to be modeled. Two types of elements were used: 2-dimensional plain stress elements to construct the housing; and 3-dimensionl beam elements to simulate the rolls, roll contact interface, chocks, nut, screw and hot strip.The model was analyzed for the lowest eight natural frequencies and mode shapes. A summary of the natural frequencies are shown in Table I. Revelant frequency and mode shapes are illustrated.Only two modes, mode 2 and 7 respectively, are likely to produce the marks observed on the strip. In both cases, the housing is ringing up and down, thus, resulting in a fluctuation in rolling force.Mode 1 is unlikely to cause strip and bottom work roll marking because the housing window and rolls remain fixed in a vertical direction and, thus, there is no fluctuation in rolling force. In addition, a frequency of 17.5 Hz is below the audible range and a rumble could not be heated under this condition. In mode 6 the housing window and rolls also remain fixed in a vertical direction. However, this mode could explain an unusual wear pattern observes on the housing liner.Modes 2, 3, 4 and 5 are so closely grouped that they are likely to act as single mode of vibration if excited. Similarly, modes 6 and 7 are assumed to act as a single mode.Thus, the results of the finite element analysis predict that vibration would occur at two natural frequencies under 100 Hz: the 60 and 80 Hz ranges. Mode 8 at 136 Hz may occur but is unlikely to produce the strip marks that were observed.An approximate rumble frequency was calculated based on roll markings observed by Wheeling-Pittsburgh personnel. In performing this calculation, it was assumed that stand F2 operates at 600 fpm and vibrates at a rate .Thus, the frequency is 120/3 = 40 Hz.Field observations and measurementsBeginning in Nov.1987, field measurements were taken on the mill to verify the frequency and magnitude of the vibrations. Typical test results with and without vibration are shown out. Even when there was no apparent vibration, the wave pattern indicated that there was actually a low level of vibration. The wave form when vibration was present was consistent and showed frequencies in the range of 40 to 50 Hz. A frequency range of 40 to 50 Hz is in the audible range and was probably the vibration that caused the audible rumble in the mill. The maximum amplitude showed peak to peak values as high as 15 mm which represents 0.0075v on a load cell where 1.0v represents 200 tons. These values indicate that there is a fluctuation in the rolling load of 8000 lb per load cell or 8 ton for the stand. The wave form indicates that there were other frequencies superimposed on the signal. On known frequency was a 60 Hz electrical noise that was present even when the mill was not operating.In Feb.1988, in addition to the strip recorder, a spectrum analyzer (Wave tech model 5820 A) was attached to the load cells. This device analyzed and reduced the signal from the load cell to fundamental frequencies. The following information was obtained from those signals.l There is a speed dependent frequency in the 47 to 55 Hz range, ie, when the mill was running at 550 fpm, the vibration was at 47 Hz. Vibration then increases in frequency as the mill accelerates reaching 55 Hz at 630 fpm.l A 60-Hz electrical noise was confirmed when there was no product in the mill.l A speed dependent frequency is present in the 87 to 110 Hz range that is approximately double the lower 47 to 55 Hz range.A typical recording from the spectrum analyzer, illustrates the 47 to 55 Hz and 87 to 110 Hz vibration ranges. The two ranges of vibration frequencies detected by field measurements are, therefore, approximately the same as the lumped results predicted by finite element analysis, ie, 61.9and 83.9 Hz.Drive train analysisFor a mill to maintain a major vibration with the amount of damping that is available from the rolled product, there must be a forcing function having considerable energy operating in the 40 to 60 Hz range. The only source of excitation that would have this potential energy is the mill drive train.Excitation frequencies of the mill drive train were calculated based on 28-in. dia work rolls and a strip speed of 600 fpm. Items in the mill drive train that were checked and their corresponding frequency are summarized in Table.Mill testIt was theorized that if the spindles were the source of vibration, their tooth orientation with respect to each other could affect the intensity level of the vibration.This phase change resulted in a significant reduction in mill vibration. It was accompanied by a marked decrease in roll changes related to mill rumble.SummaryThrough the use of finite element analysis, field measurements and a mill test, vibration problems associated with stand F2 of a hot strop mill have been found to be caused by a mode of vibration where the roll stack and housing ring up and down hence resulting in a fluctuation in the rolling load.Finite element analysis predicted two damaging modes of vibration at 62 and 84 Hz. The existence of corresponding modes of vibration were confirmed by mill tests that indicated the existence of one mode in the 47 to 55 Hz range and another in the 87 to 110 Hz range.Drive train analysis indicated that the cause of the excitation was a function of spindle speed and the number of gear teeth.A low cost spindle setup procedure was adopted in which the spindle teeth are placed out of phase to avoid an additive bottoming out effect of the gear teeth in the upper and lower drive trains.Mill rumble has been reduced to the point where other factors are dictating roll change and strip surface quality. Rumble is no longer a factor in strip quality.旋转匹兹堡80热板带轧机 F机架的振动分析在热板带轧机中，对热板带质量的要求日趋提高。物理和金属特性、表面状态与维护、生产和质量控制人员有关。一家钢铁公司不再仅仅重视生产数量，在时间安排上和具有竞争的价格方面上，必须确保质量。为了完成这一目标，所有的设备都必须正常工作，保持在最高的可能水平上。旋转匹兹堡80热板带轧机开始轧制运转于1965年10月。主要设备提供商是blax-know提供机械设备，westing-house提供电气元件。每个精轧机架上装有2个 3000hp的电机。只要轧机开始运转，当轧制某种类型产品时，如：薄厚度产品，HSLA和硬度级产品时，就出现了低硬度，大噪音等现象。噪声常常发生在机架或机架上。报告中说，在以前这种大噪声和硬度低的问题也出现过。因为提高质量和发展的合理性是旋转匹兹堡的重要问题。热交换设备电气化和机械化变得相当重要。随着质量意识的提高，噪声环境逐渐变得重要，因为它对带钢质量的影响和经常更换轧辊同样需要保持板带质量。在eichleay研究之前，由轧机震动导致的噪声在硬度方面增强了，看起来主要出现在机架上。一旦发生，从架出来的板带表面出现一系列直线标记，平行于工作辊，穿过整个板带的宽度。当板带通过机架时，这些直线被轧没了。在轧制好的卷带中看不见。当主要完成的卷带表面质量未被影响，在和机架中轧辊的表面迅速老化，反过来将导致在接下来的板卷中表面问题，需要较早地更换轧辊。这需要大概1520分钟来完成。当噪声在轧机中被发现的时候，在机架中的驱动转轴在轧辊末端装置中产生过多的热量，也被观察到了。应用冷却水和冷却油液来阻止过热。在1986和1987年早期，广泛的测试和检验在旋转轴上进行。轧制问题与轧机矫正问题同样被考虑到。较好的润滑剂的应用也起到了较小的利益效果。在1987年5月，在轧机上从事不同问题的时候，Eichleay认识到在机架上间歇性的噪声和振动问题。下面两个目的的工程研究被重视了。 在机架上分析和建立振动原因。 完善设计方法，避免或者减小震动到可允许的水平。分析震动问题的解决方案，修正热板带轧机的维护操作是这篇文章的主题。振动分析在热板带轧机中，经常性的振动原因扭转的增幅率(TAF)是考虑的主要问题。然而，被排除了，因为TAF是个短暂的现象，当一个钢坯第一次进入或离开轧辊口的时候它才发生。在旋转匹兹堡环境下，当钢坯第一次进入机架时，没有振动。当轧机加速运转时，振动随之发生。从开始迅速地达到最大。另外，TAF没有解释发生在板带上的标记现象。只有轧制力的波动能产生观察到的图形。其扩展到带钢的整个宽度。它被假设为振动是由于周期激励源与轧机机架的固有频率相接近。进而，激励源十分有能力维持这样的振动。特别是扎制产品的阻尼特性被考虑的时候。为了隔离振源，下列的程序被建立起来： 使用有限元方法分析轧机机架的模态振动。 在轧机上观察和测量来建立振动频率和大小。 驱动系统分析检测是否任何一个旋转的组件都能产生并维持振动的周期性驱动力。 数据分析决定不同因素间的相互关系。有限元分析建立机架的固有频率和模型形状，轧机机架和轧辊系统用有限元计算分析。轧机机架的有限元模型的构造由于对称，只有一半的机架作模型。两种单元类型被使用，二维应力单元构建机罩，三维柱状单元模拟轧辊、轧辊面、垫块、螺母、螺钉和热板带。模型被分析的是最低的八个固有频率，固有频率的摘录在表中，相关频率和模型形状在2B和2E中描述。只有两个模型，模型2和模型7很可能产生观测中板带的标记，在两个事例中，机罩正在上下振动，这样导致了轧制力的被动。模型1（17.5HZ）不能造成板带和底部轧辊标记。因为机罩窗和轧辊保持固定在垂直方向上，这样在轧制力中不存在波动。另外，17.5HZ的频率低于可听见范围。在这种条件下，噪声不能被听到。模型6（79.2HZ）说明在观察的机
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