【正文】 eets ,rounds and sections are obtained in a number of passes starting from billets or slabs .For rolling the flat products ,plain cylindrical rolls are used but for sections ,grooved rolls are used .The type of grooving done is decided by the final section desired. The rollpass sequence can be broadly categorised into three types.Break down passes These are used for reducing the crosssectional area nearer to what is desired .These would be the first to be present in the sequence.Roughing passes In these passes also ,the crosssection gets reduced ,but along with it,the shape of the rolled material es nearer to the final shape.Finishing passes These are the final passes,which give the required shape of the rolled ,the finishing pass follows a leader pass. 軋制孔型最終軋制產(chǎn)品如板條，薄片，板料，圓形和管形是從坯料或者厚板通過(guò)許多孔型得到的。在進(jìn)入點(diǎn)與出口點(diǎn)中任何一個(gè)區(qū)域i上，作用在輥上的壓力通過(guò)進(jìn)入邊直接標(biāo)出的力加上出口邊指出的力得到。建議讀者參考本書(shū)中的詳細(xì)分析。硬度在600800BHN的超硬輥用于冷軋。硬度在150到250BHN之間的軟輥被用在大型鋼材軋制機(jī)的粗軋機(jī)架和鋼坯軋機(jī)上。The ingot obtained by casting would normally have defects such as shrinkage cavities,blow holhes and slag the ingot is rolled,the shrinkage cavity(called pipe) is towards the end ,which is then cropped after a few initial passes to reduce the defects in the defects in the finished product.通過(guò)鑄造獲得的初軋方坯一般帶有縮孔、氣眼、夾渣等缺陷。The steel ing out of a blast furnace or a remelting shop is in the form of an ingot which has a cross section of the order of 600*600 ingots are further processed in rolling mills tl produce the inter mediate shapes such as blooms,slabs and are generally square cross sections varying from 150*150mm to 400* are rectangular cross sections with widths varying from 500to 1800mmand thicknesses varying from 50 to300 are rectangular cross sections with sizes varying from 40*40 mm to 150*150 mm.從鼓風(fēng)爐或者熔煉車間出來(lái)的鋼都是橫截面是600600mm的鑄錠。對(duì)于需要大量縮減量的軋制機(jī)布置來(lái)說(shuō)，大量的自由旋轉(zhuǎn)輪代替了單獨(dú)的小軋輥，這些旋轉(zhuǎn)輪被安在行星軋制機(jī)中的大支撐軋輥上。為此，需要一個(gè)傾斜板布置將金屬帶到輥軋機(jī)的水平位置。因?yàn)樾枰崔D(zhuǎn)驅(qū)動(dòng)，所以這種鋼架比不倒轉(zhuǎn)的鋼架更貴。在這種布置中，軋輥只會(huì)朝著一個(gè)方向運(yùn)動(dòng)。 Rolling Stand ArrangementThe arrangement of rolls in a rolling mill, also called rolling stand,varies depending on the various possible configurations are presented in names of the rolling stand arrangements are generally given by the number of rolls first one in ,the 2high non reversing rolling stand arrangement,is the most mon on this ,the rolls always move in only one direction .The arrangement shown in is a 2high reversing rolling stand,where the direction of roll rotation can be type of stand is particularly useful in reducing the handling of the hot metal in between the rolling all the metal has reached the right side of the ,the direction of the rolls is reversed and the metal is allowed to enter into the next stands are more expensive pared to the non reversible type because of the reversible drive needed. 軋鋼架布置輥軋機(jī)軋輥的布置也叫軋鋼機(jī)架因應(yīng)用的不同而不同。反過(guò)來(lái)說(shuō)，也可以通過(guò)減小輥的直徑來(lái)獲得，因?yàn)?，減少相同的量，較小的輥比較大的輥擁有減小的接觸長(zhǎng)度。在接觸長(zhǎng)度上，金屬和旋轉(zhuǎn)輥的速度保持一致，這個(gè)地方被設(shè)計(jì)為中性平面。金屬進(jìn)入輥軋機(jī)和離開(kāi)輥軋機(jī)的體積應(yīng)該保持不變，除了最初通過(guò)輥軋機(jī)填充鑄錠中的空位和型腔時(shí)會(huì)使體積減少。輥軋通過(guò)摩擦力和之后的壓力將金屬放入旋轉(zhuǎn)輥中來(lái)獲得最終的形狀。輥軋可以生產(chǎn)在沿長(zhǎng)度方向上擁有恒定截零件。2. 因?yàn)榧庸び不脑?，最大變形量也?huì)受到限制，任何后續(xù)的變形都需經(jīng)過(guò)退火。而且，冷加工不會(huì)有表面脫碳的可能性。3. 由于金屬內(nèi)熱擴(kuò)散的原因，控制工件的溫度是很困難的，所以在熱加工中很難獲得精確的尺寸。4. 熱加工中，晶粒的繼續(xù)改良是有可能的，如果溫度和加工率得到適當(dāng)?shù)目刂疲瑢?huì)獲得優(yōu)良的晶粒尺寸和良好的機(jī)械性能。HOT Working Advantages1. As the material is above the recrystallization temperature,any amount of workingcan be imparted since there is no strainhardening taking place.2. At a high temperature,the material would have higher amount of ductility andtherefore there is no limit on the amount of hot working that can be done on a brittle material can be hot worked.3. Since the shear stress gets reduced at higher temperatures,hot working requiresmuch less force to achieve the necessary deformation.熱加工益處1. 當(dāng)材料溫度在再結(jié)晶溫度以上時(shí)，加工量的多少都是可以的，因?yàn)檫@時(shí)候沒(méi)有加工硬化的產(chǎn)生。但是，熱加工的最后溫度比再結(jié)晶溫度高太多的話，如C,晶粒的尺寸就開(kāi)始增大并且最后會(huì)得到粗大的晶粒尺寸。如A中的一個(gè)簡(jiǎn)單加熱過(guò)程，當(dāng)溫度超過(guò)再結(jié)晶溫度后，晶粒就開(kāi)始長(zhǎng)大。In hot working, the process may be carried above the recrystallization temperature with or without actual example,for lead and tin,the recrystallization temperature is below the room temperature and hence working of these metals at room temperature is always hot for steels,the recrystallization temperature is of the order of 1000℃,and therefore working below that temperature is still cold working only.在熱加工中，在加熱或者不加熱的實(shí)際條件下再結(jié)晶可能在再結(jié)晶溫度以上發(fā)生。再結(jié)晶溫度是由美國(guó)金屬學(xué)會(huì)這樣定義的“在一定的時(shí)間段內(nèi)，冷加工金屬完成再結(jié)晶時(shí)的最小溫度”。Those processes , working above the recrystallization temperature, are termed hotworking processes whereas those below are termed coldworking processes在這些加工工藝中，加熱溫度在再結(jié)晶溫度以上的叫做熱加工，在再結(jié)晶溫度以下的叫做冷加工。The wastage of material in metalworking processes is either negligible or very small, and the production rate is in general very high .these two factors give rise to the economy in production材料的浪費(fèi)在金屬加工過(guò)程中是很少的，甚至可以忽略不計(jì)，并且其生產(chǎn)率一般來(lái)說(shuō)是非常高的。Since the grains are elongated in the direction of flow, whey would be able to offer more resistance to stresses acting across them . As a result, the mechanically worked metals called wrought products would be able to achieve better mechanical strength in specific orientation ,that of the flow direction .since it is possible sible to control these flow lines in any specific direction by careful manipulation of the applied forces as shown in Fig. , it is possible to achieve optimum mechanical properties. The metal, of course, would be weak along the flow lines.因?yàn)榫ЯＴ诹鲃?dòng)方向上被拉長(zhǎng)了，這樣他們就更能夠抵抗作用于其上的應(yīng)力。在微觀范圍內(nèi)，當(dāng)塑性變形產(chǎn)生的時(shí)候，在固體內(nèi)部金屬的流動(dòng)傾向于特定的方向，這個(gè)方向取決于加工類型和應(yīng)力方向。金屬所需要的變形可以只通過(guò)施加大量的機(jī)械力或者通過(guò)加熱金屬并且施加少量的應(yīng)力來(lái)獲得。通常，金屬采用塑性變形加工是因?yàn)榭梢酝ㄟ^(guò)其獲得良好的機(jī)械性能。微觀的變形方式可以從冶金學(xué)課本中找到。這些可見(jiàn)的線條叫做纖維流線。當(dāng)然，金屬在沿著纖維線的方向也會(huì)變得疲軟。這種區(qū)分是基于機(jī)械應(yīng)力施加前金屬的受熱程度。事實(shí)上，新的晶粒是在嚴(yán)重變形的時(shí)候開(kāi)始形核的。冷加工量越高，再結(jié)晶溫度越低。In hot working.,the temperature at which the working is pleted is important since any extra heat left after working will aid in the grain growth,thus giving poor mechanical effect of temperature of pletion of hot working is shown schematically in simple heating is shown in A,where the grains start growing after the metal size would be larger than when started in heating,when the metal is worked,becau