轧机机械专业毕业设计外文翻译

1、精选优质文档-倾情为你奉上RollingObjectiveTo perform rolling process on an lead bar in order to observe the change in both the cross-sectional area and the general shape.Theory1. DefinitionFlat rolling or Rolling is defined as the reduction of the cross-sectional area of the metal stock, or the general shaping o

2、f the metal products, through the use of the rotating rolls 1. It allows a high degree of closed-loop automation and very high speeds, and is thus capable of providing high-quality, close tolerance starting material for various secondary sheet metal working processes at a low cost 1.2. Schematic Dra

3、wing of Rolling ProcessFigure 1. Rolling Process 2The rolls rotate as illustrated in Figure 1. to pull and simultaneously squeeze the work between them. The basic process shown in Figure 1 is flat rolling, used to reduce the thickness of a rectangular cross section.Figure 2. Various configurations o

4、f rolling mills: (a) two high, (b) three high, (c) four high, (d) cluster mill, and (e) tandem rolling mill 2.Various rolling mill configurations are available to deal with the variety of applications and technical problems in the rolling process. The basic rolling mill consists of two opposite rota

5、ting rolls and is referred to as a two-high rolling mill (Figure 2a). In the three-high configuration Figure 2(b), there are three rolls in a vertical column, and the direction of rotation of each roll remains unchanged. To achieve a series of reductions, the work can be a passed through from either

6、 side by raising or lowering the strip after each pass. The equipment in a three-high rolling mill becomes more complicated, because an elevator mechanism is needed to raise and lower the work 2.Roll-work contact length is reduced with a lower roll radius, and this lads to lower forces, torque, and

7、power. The four-high rolling mill uses two smaller diameter rolls to contact the work and two backing rolls behind them. Another roll configuration that allows smaller working rolls against the work is the cluster rolling mill.To achieve higher throughput rates in standard products, a tandem rolling

8、 mill is often used. This configuration consists of a series of rolling stands. With each rolling step, work velocity increases, and the problem of synchronizing the roll speeds at each stand is significant 2.3. General Overview of ProcessThe primary objectives of the flat rolling process are to red

9、uce the cross-section of the incoming material while improving its properties and to obtain the desired section at the exit from the rolls. The process can be carried out hot, warm, or cold, depending on the application and the material involved. The rolled products are flat plates and sheets. Rolli

10、ng of blooms, slabs, billets, and plates is usually done at temperatures above the recrystallization temperature (hot rolling). Sheet and strip often are rolled cold in order to maintain close thickness tolerances.Basically flat rolling consists of passing metal between two rolls that revolve in opp

11、osite directions, the space between the rolls being somewhat less than the thickness of the entering metal. Because the rolls rotate with a surface velocity exceeding the speed of the incoming metal, friction along the contact interface acts to propel the metal forward. The metal is squeezed and elo

12、ngated and usually changed in cross section. The amount of deformation that can be achieved in a single pass between a given pair of rolls depend on the friction conditions along the interface. If too much is demanded, the rolls will simply skid over stationery metal. Too little deformation per pass

13、 results in excessive cost. Rolling involves high complexity of metal flow during the process. From this point of view, rolling can be divided into the following categories 3:· Uniform reduction in thickness with no change in width: Here, the deformation is in plane strain, that is, in the dire

14、ctions of rolling and sheet thickness. This type occurs in rolling of strip, sheet, or foil.· Uniform reduction in thickness with an increase in width: Here, the material is elongated in the rolling direction, is spread in the width direction, and is compressed uniformly in the thickness direct

15、ion. This type occurs in the rolling of blooms, slabs, and thick plates.· Moderately non-uniform reduction in cross section: Here, the metal is elongated in the rolling direction, is spread in the width direction, and is reduced non-uniformly in the thickness direction.· Highly non-uniform

16、 reduction in cross section: Here, the reduction in the thickness direction is highly non-uniform. A portion of the rolled section is reduced in thickness while other portions may be extruded or increased in thickness. As a result, in the width direction metal flow may be toward the center 3.Hot Rol

17、lingThe distinctive mark of hot rolling is not a crystallized structure, but the simultaneous occurrence of dislocation propagation and softening processes, with or without recrystallization during rolling. The dominant mechanism depends on temperature and grain size. In general, the recrystallized

18、structure becomes finer with lower deformation temperature and faster cooling rates and material of superior properties are obtained by controlling the finishing temperature 1.Hot rolling offers several advantages 1:1) Flow stresses are low, hence forces and power requirements are relatively low, an

19、d even very large workpieces can be deformed with equipment of reasonable size.2) Ductility is high; hence large deformations can be taken.3) Complex part shapes can be generated.The upper limit for hot rolling is determined by the temperature at which either melting or excessive oxidation occurs. G

20、enerally, the maximum working temperature is limited to 50°C below the melting temperature. This is to allow the possibility of segregated regions of lower melting material 4.Cold RollingCold rolling, in the everyday sense, means rolling at room temperature, although the work of deformation can

21、 raise temperatures to 100-200°C. Cold rolling usually follows hot rolling. A material subjected to cold rolling strain hardness considerably. Dislocation density increases, and when a tension test is performed on this strain-hardened material, a higher stress will be needed to initiate and mai

22、ntain plastic deformation; thus, the yield stress increases. However, the ductility of the material as expressed by total elongation and reduction of area drops because of the higher initial dislocation density. Similarly, strength coefficient rises and strain-hardening exponent drops. Crystals (gra

23、ins) become elongated in the direction of major deformation 1.Cold rolling has several advantages 1:1) In the absence of cooling and oxidation, tighter tolerances and better surface finish can be obtained.2) Thinner walls are possible.3) The final properties of the workpiece can be closely controlle

24、d and, if desired, the high strength obtained during cold rolling can be retained or, if high ductility is needed, grain size can be controlled before annealing.4) Lubrication is, in general, easier. Rolling Problems and DefectsThe main problem during rolling process is the calibration of rollers. T

25、his calibration faults may occur in case of used bearings and may affect the thickness of parts. A simple classification is as here below:a. Lengthwise Occurring DefectsChange of rollers speedMaterial temperatureRoller temperatureInlet thicknessMaterial propertiesEccentric and conical rollersUsed be

26、aringsb. Transversally Occurring DefectsParallel position of rollersSurface geometry of rollers轧 制目的：为了观察在执行轧制过程中铅条的横截面积和一般形状的变化。理论：1. 定义 扁平孔型轧制或者轧制被下定义为金属原料代表性面积的缩小，或金属制品通过旋转轧辊的一般成形。它允许一个闭合循环自动化的高程度和高速度，而且因此能够为各种以一个低成本工作程序的中级金属片提供高质量, 小公差的原材料.12. 轧制过程的示意图 图1 轧制过程2轧辊旋转如图 1 所示同时地在他们之间进行拉压工作。在 图1 所示的基

27、本过程是扁平孔轧制，通常用来减少矩形断面的厚度。图2.各种结构的轧钢机：(a)二辊式轧机，(b) 三辊式轧机（c）四辊式轧机，（d）多辊式轧机，(e)串联式轧机。各种结构的轧机可处理轧制过程中的各种应用和技术问题。基本轧机是由两个反向旋转的两个轧辊组成,这被称为二辊式轧机(图2a) 在三辊的结构中图2(b),有三个在同一垂直列的且旋转方向保持不变的轧辊。可以通过任意方向升降钢带轧槽来完成一连串的轧制工作。这些设备在三辊式轧机中变得更加复杂,因为升降机构需要升降功2轧辊工作的接触长度因为较小半径轧辊而被缩短，并且这样可以减小力，扭矩功率.这种四辊轧机使用两个更小直径的轧辊轧制材料并且在它们后面有

28、两个支承辊.在多辊式轧机的轧辊的结构允许有更小的工作辊。为完成更高吞吐率的标准产品，经常使用串联轧机。它的结构由一连串的轧钢机架组成。经过每个轧制阶段，轧制速度都会增加，并且轧辊速度在每个机架上的同步问题都是有意义的。3. 关于过程的一般看法扁平孔型轧制主要目的是减小引入原料的横截面积，改变它的道具并在轧辊出口处获得所期望的截面。这个过程可以执行热轧冷轧，依靠应用程序并与原料有关。轧制产品为板材。块钢 、厚平板、坯段和金属板的轧制通常是在再结晶温度以上的温度下进行的（热轧）。薄板和条钢经常进行冷轧为了维持小公差的厚度。基本的扁平孔型轧制由金属通过两个反方向旋转轧辊且两辊间的空隙小于输入金属尺寸

29、构成的，.因为轧辊以超过金属进入速度旋转，沿着接触表面的摩擦力驱动金属前进。金属被压榨拉长并经常改变截面尺寸。变形量单一通过一对依靠沿摩擦力接触面的特定轧辊完成。如果有咬入量过多，轧辊将完全刹车结束文具金属。过小的变形量会导致成本的增加。轧制包含金属在轧制过程中变形的高复杂性。从这个观点来看，轧制可以分为以下种类3：· .厚度统一宽度无变化：这里，这种变形是平面变形，那是，在这个轧制方向上和薄板厚度上。这种类型的轧制发生在条钢、薄板、或金属薄片。· 厚度统一宽度增长：在这里，在轧辊旋转方向上被拉伸，在宽度方向上被伸展并且在厚度方向上被均匀的压扁。这种类型在块钢、坯钢、和厚板的轧制过程。· 适度的不均匀的横截面变形：在