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1、,机电技术专业英语,2,Lesson Four,Text,In drop forging, a piece of metal, roughly or approximately of the desired shape, is placed between die faces having the exact form of the finished piece, and forced to take this form by drawing the dies together1. This method is widely used for the manufacture of parts
2、both of steel and brass. Large ingots are now almost always forged with hydraulic presses instead of with steam hammers, since the work done by a press goes deeper2. Metal in the form of hotrolled or coldrolled sheets or strips may be formed into many shapes by forcing the sheet into the impressions
3、 in metal dies. This process is known as stamping, or pressing of metals, and involves many different operations, such as bending, drawing, punching, etc. These operations are successfully carried out through the proper die design and proper operation of the press in which the dies are placed. Sheet
4、s or strips of steel, brass, copper, aluminium, or other metal are placed between dies, and a slow action of the power press brings the dies together, forcing the metal to assume the required shape.,Forging, Stamping and Rolling,Rolling is the process of shaping metal in a machine called rolling mil
5、l. Ingots of metal are rolled by forcing them between two rollers rotating in opposite directions, thus pressing the metal into the required shape3. If the rollers have no grooves on their surfaces, the metal is rolled into the form of a sheet or plate. If the rollers have grooves of a certain shape
6、, the metal will take the form of these grooves, thus it may be shaped into the form of bars or rods. There are two kinds of rolling: hot rolling and cold rolling. Before cold rolling, the scale covering the surface of the hotrolled object should be removed. Cold rolling produces a higher surface fi
7、nishing sheet and gives it a very exact size. The process has innumerable advantages. Many shapes may be manufactured in quantities at a rapid rate and at a relatively low cost.,Lesson Four,4,New Words and Expressions,Lesson Four,5,Lesson Four,6,Lesson Four,7,Notes,1. In drop forging, a piece of met
8、al, roughly or approximately of the desired shape, is placed between die faces having the exact form of the finished piece, and forced to take this form by drawing the dies together. 模锻是将已经具有与要求的(锻件)形状大致相同的金属柸料放置在上、下模膛之间（模膛具有与完工后锻件相一致的精确形状），然后用力将上、下模紧压在一起，迫使其获得该零件形状的一种工艺。 “a piece of metal”作主语，“is p
9、laced”and “and forced”作谓语，“to take this form by drawing the dies together”是主语补足语。其中，“roughly or approximately of the desired shape”是后置定语，修饰“metal”；“between die faces”为地点状语，修饰“placed”；“having the exact form of the finished piece”是现在分词短语作后置定语，修饰“faces”。,Lesson Four,2. Large ingots are now almost alway
10、s forged with hydraulic presses instead of with steam hammers, since the work done by a press goes deeper. 因为压力机所作的功能够传递得较深，所以现在大铸锭几乎总是由液压机代替蒸汽锤进行锻造。 “instead of”是短语介词，作“代替”或“而不是”解。“since the work done by a press goes deeper”是原因状语从句，表示主句中的某一动作或状态所发生的原因。“done by a press”是过去分词短语作定语，修饰“the work”。 3. In
11、gots of metal are rolled by forcing them between two rollers rotating in opposite directions, thus pressing the metal into the required shape. 铸锭被轧制是靠使其在两个相反方向回转的轧辊之间强制加压，从而将金属轧压成所需的形状。 “by forcing them between two rollers”为方式状语，修饰谓语“are rolled”。“rotating in opposite directions”是现在分词短语作后置定语，修饰“rolle
12、rs”。“thus pressing the metal into the required shape”为结果状语，修饰“are rolled”。,Lesson Four,9,参考译文,模锻是将已经具有与要求的（锻件）形状大致相同的金属坯料放置在上、下模膛之间（模膛具有与完工后锻件相一致的精确形状），接着用力将上、下模紧压在一起，迫使其获得该零件形状的一种工艺。这种方法广泛地应用于制造钢和黄铜零件。因为压力机所做的功传递得较深，所以现在大铸锭几乎总是由液压机代替蒸汽锤进行锻造。热轧或冷扎的金属薄板或带钢靠施加外力迫使其进入金属模的凹膛内，从而形成各种形状的部件，这种方法就是金属冲压。冲压包含
13、许多不同的操作工序，如弯曲、拉伸、冲孔，等等。需借助于恰当的模具设计和正确地操纵装有该模具的压力机才能使这些工序很好地完成。将金属薄板或带钢、黄铜、纯铜、铝或其他金属材料置于上、下冲模之间，然后靠机动压力机的缓慢动作使上、下模接近，迫使金属坯料呈现出所需要的形状。,锻造、冲压和轧制,Lesson Four,轧制是在被称为轧机的机器上进行的一种金属加工成型方法。铸锭被轧制是靠使其在两个相反方向回转的轧辊之间强制加压，从而将金属轧压成所要求的形状。如果轧辊表面没用轧槽，金属将被轧成薄板或板料。如果轧辊具有某种孔形的轧槽，那么金属的形状将和这些轧槽的形状相同，所以金属可以被加工成钢筋或盘条等。 轧制有两类，热轧和冷轧。冷轧前，应将覆盖在热轧坯料表面的氧化皮除净。冷轧可生产出表面较为光洁且尺寸非常精确的薄板。这种加工方法优点很多，能快速且低成本地大批量生产多种型材。,Lesson Four,谢谢观赏,,Thank You !,
