軋機(jī)機(jī)械專業(yè)畢業(yè)設(shè)計(jì)外文翻譯

1、精選優(yōu)質(zhì)文檔-傾情為你奉上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軋 制目的：為了觀察在執(zhí)行軋制過(guò)程中鉛條的橫截面積和一般形狀的變化。理論：1. 定義 扁平孔型軋制或者軋制被下定義為金屬原料代表性面積的縮小，或金屬制品通過(guò)旋轉(zhuǎn)軋輥的一般成形。它允許一個(gè)閉合循環(huán)自動(dòng)化的高程度和高速度，而且因此能夠?yàn)楦鞣N以一個(gè)低成本工作程序的中級(jí)金屬片提供高質(zhì)量, 小公差的原材料.12. 軋制過(guò)程的示意圖 圖1 軋制過(guò)程2軋輥旋轉(zhuǎn)如圖 1 所示同時(shí)地在他們之間進(jìn)行拉壓工作。在 圖1 所示的基

27、本過(guò)程是扁平孔軋制，通常用來(lái)減少矩形斷面的厚度。圖2.各種結(jié)構(gòu)的軋鋼機(jī)：(a)二輥式軋機(jī)，(b) 三輥式軋機(jī)（c）四輥式軋機(jī)，（d）多輥式軋機(jī)，(e)串聯(lián)式軋機(jī)。各種結(jié)構(gòu)的軋機(jī)可處理軋制過(guò)程中的各種應(yīng)用和技術(shù)問(wèn)題。基本軋機(jī)是由兩個(gè)反向旋轉(zhuǎn)的兩個(gè)軋輥組成,這被稱為二輥式軋機(jī)(圖2a) 在三輥的結(jié)構(gòu)中圖2(b),有三個(gè)在同一垂直列的且旋轉(zhuǎn)方向保持不變的軋輥?？梢酝ㄟ^(guò)任意方向升降鋼帶軋槽來(lái)完成一連串的軋制工作。這些設(shè)備在三輥式軋機(jī)中變得更加復(fù)雜,因?yàn)樯禉C(jī)構(gòu)需要升降功2軋輥工作的接觸長(zhǎng)度因?yàn)檩^小半徑軋輥而被縮短，并且這樣可以減小力，扭矩功率.這種四輥軋機(jī)使用兩個(gè)更小直徑的軋輥軋制材料并且在它們后面有

28、兩個(gè)支承輥.在多輥式軋機(jī)的軋輥的結(jié)構(gòu)允許有更小的工作輥。為完成更高吞吐率的標(biāo)準(zhǔn)產(chǎn)品，經(jīng)常使用串聯(lián)軋機(jī)。它的結(jié)構(gòu)由一連串的軋鋼機(jī)架組成。經(jīng)過(guò)每個(gè)軋制階段，軋制速度都會(huì)增加，并且軋輥速度在每個(gè)機(jī)架上的同步問(wèn)題都是有意義的。3. 關(guān)于過(guò)程的一般看法扁平孔型軋制主要目的是減小引入原料的橫截面積，改變它的道具并在軋輥出口處獲得所期望的截面。這個(gè)過(guò)程可以執(zhí)行熱軋冷軋，依靠應(yīng)用程序并與原料有關(guān)。軋制產(chǎn)品為板材。塊鋼 、厚平板、坯段和金屬板的軋制通常是在再結(jié)晶溫度以上的溫度下進(jìn)行的（熱軋）。薄板和條鋼經(jīng)常進(jìn)行冷軋為了維持小公差的厚度?；镜谋馄娇仔蛙堉朴山饘偻ㄟ^(guò)兩個(gè)反方向旋轉(zhuǎn)軋輥且兩輥間的空隙小于輸入金屬尺寸

29、構(gòu)成的，.因?yàn)檐堓佉猿^(guò)金屬進(jìn)入速度旋轉(zhuǎn)，沿著接觸表面的摩擦力驅(qū)動(dòng)金屬前進(jìn)。金屬被壓榨拉長(zhǎng)并經(jīng)常改變截面尺寸。變形量單一通過(guò)一對(duì)依靠沿摩擦力接觸面的特定軋輥完成。如果有咬入量過(guò)多，軋輥將完全剎車結(jié)束文具金屬。過(guò)小的變形量會(huì)導(dǎo)致成本的增加。軋制包含金屬在軋制過(guò)程中變形的高復(fù)雜性。從這個(gè)觀點(diǎn)來(lái)看，軋制可以分為以下種類3：· .厚度統(tǒng)一寬度無(wú)變化：這里，這種變形是平面變形，那是，在這個(gè)軋制方向上和薄板厚度上。這種類型的軋制發(fā)生在條鋼、薄板、或金屬薄片。· 厚度統(tǒng)一寬度增長(zhǎng)：在這里，在軋輥旋轉(zhuǎn)方向上被拉伸，在寬度方向上被伸展并且在厚度方向上被均勻的壓扁。這種類型在塊鋼、坯鋼、和厚板的軋制過(guò)程。· 適度的不均勻的橫截面變形：在