ImageVerifierCode 换一换
格式:DOC , 页数:16 ,大小:50KB ,
资源ID:57399      下载积分:5 金币
已注册用户请登录:
账号:
密码:
验证码:   换一换
  忘记密码?
三方登录: 微信登录   QQ登录  
下载须知

1: 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。
2: 试题试卷类文档,如果标题没有明确说明有答案则都视为没有答案,请知晓。
3: 文件的所有权益归上传用户所有。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 本站仅提供交流平台,并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。

版权提示 | 免责声明

本文(外文翻译刀具材料.doc)为本站会员(夺命阿水)主动上传,三一文库仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知三一文库(发送邮件至doc331@126.com或直接QQ联系客服),我们立即给予删除!

外文翻译刀具材料.doc

1、译文刀具材料为了在切削过程中有适当的功能,切削刀具必须有一定的机械性能,这些性能包括高的硬度,且在切削过程中产生高温时仍能保持其硬度,同时也要有好的韧性、抗蠕变及抗磨损,能承受大的支承压力。事实上,切削刀具的材料不同其机械性能也不同。因此,切削刀具材料应能适应不同的切削条件,如工件材料、切削速度(生产率)、所使用的冷却剂等等。下面所列的是常用的切削刀具材料。碳素工具钢 碳素工具钢含碳量为0.11.4%,不含合金元素,通过热处理可提高其硬度。碳素钢在温度600F(300C)以上时由于回火作用而丧失其硬度,因此,碳素工具钢只适合于制造手工工具或软金属材料的低速切削用刀具。低合金工具钢 低合金工具钢

2、的含碳量与碳素工具钢相似。然而,顾名思义,它含有一定的合金元素,低合金工具钢刀具也须进行热处理,并仅用于低速切削。切削温度也不能超过600F(300C)以避免退火现象。高速钢 高速钢(HSS)是含有一定比例合金元素的合金钢,如钨(18%),铬(4%)、钼、钒和钴。高速钢通过加热(分两个阶段),在空气中冷却,然后进行回火。由高速钢制成的刀具在温度高达1100F(600C)时仍能保持其硬度,这类刀具用于切削速度相对较高的场合。除了高生产率切削加工用刀具外,单刃刀具、麻花钻及铣刀也通常由高速钢制造。铸造硬合金 铸造硬合金既可能是黑色金属,也可能是有色金属,其含碳量约为3%,它与金属反应形成非常硬的碳

3、化物。这些碳化物即使在温度1650F(900C)时仍保持其硬度。因为这种材料不可进行切削加工,所以,在陶瓷模中铸成刀片,然后通过铜焊或机械方法将其固定在刀杆上。烧结硬质合金刀片 烧结硬质合金是为克服铸造硬合金的缺陷(即脆性)而发展起来的。当初,其成分约82%是非常硬的碳化钨颗粒及18%的作为粘结剂的钴。烧结碳化硬质合金总是由粉末冶金技术(如压制和烧结)模压成型。从强度方面考虑,要将整把刀具由硬质合金来制造是不可能的,而只能制造成硬质合金刀片,然后将刀片用铜焊或机械方法固定在钢制刀杆上,而刀片具有所需的切削角度。烧结硬质合金也称为“Widia”,这个词来自德语“WieDiamant”意为“象金刚

4、石”。这是因为它具有极高的硬度,可达HRC90,且在高达1850F(1000C)的温度下仍能保持这一硬度。最近所研制的硬质合金是将碳化钨,碳化钛和碳化钼混合,而用钴或镍合金作为粘结剂。其结果是摩擦系数小,抗磨损性能好。事实上,不论是切削速度高还是进给量大的切削加工,都推荐采用硬质合金刀片刀具,且常用于大批量生产。近来,硬质合金刀比采用氮化物或氧化物涂层以增加其耐磨性及寿命。陶瓷刀片 陶瓷刀片基本上是由很细的氧化铝粉末(AL2O3),通过压制和烧结而成。陶瓷的硬度几乎与硬质合金相同,但在温度高达2200F(1100C)时仍能保持其硬度,且导热系数很小。这种特性使得切削速度是用硬质合金刀片切削时的

5、2-3倍。陶瓷刀片也有极好的耐磨性并不致形成月牙洼磨损,且不需用冷却液。但其韧性和抗弯强度小,这影响抗蠕变载荷和振动的敏感性。因此,陶瓷刀片仅用于切削速度极高(达1800ft/min,600m/min)时的精密加工。下面是三种常用的陶瓷刀片。(1).氧化物刀片,主要由氧化铝组成,其颜色为白色且稍带粉红色或浅黄色。(2).金属陶瓷刀片 它含有氧化铝或某些金属如钛或钼。其颜色呈黑灰色。(3).由氧化物及碳化物制成的刀片,呈黑色。 由于与氧的混合作用,陶瓷刀片不可用于加工铝材。 金刚石 金刚石可固连在钢制刀杆上,可用于精密切削加工,推荐用于加工铝、镁、钛、铜、橡胶及聚合物。当加工金属材料时,可达到镜

6、面。2.工件材料切削加工性一词常用于描述工件材料的加工性能,根据其切削过程有几种含义。如果说材料A比材料B可切削性好,这可能意味着切削材料A时刀具磨损率低,或者切削材料A可获得更小的表面粗糙度,或者切削加工材料A时所需的功率较小。很清楚,在精加工过程中,刀具的磨损及表面粗糙度都是最重要的因素,而对于粗加工而言,刀具磨损和功率消耗是重要因素。应该注意,所指的加工性只能是相对于所指的特定环境而言的。例如,在某一特定条件下,材料A可能比材料B可获得更小的表面粗糙度,但在其他条件下,若采用不同的刀具材料,其结果可能相反。对于可加工性的其他衡量指标,如刀具磨损率和功率消耗,情况也与此相似。为了进一步说明

7、情况,将刀具磨损率相同的材料归为一类,但按照表面粗糙度或功率消耗来分的话这些材料又属不同的类型。很清楚,可加工性一词除降低了质量方面的要求外,并没有其他什么意义。虽然可加工性降低了质量方面的要求,人们还是试图获得可加工性的定量的衡量方法可加工性指数或序号。若结果是有用的,则测得这一指数的方法是很有价值的,特别是对钢铁企业而言,它必须经验所生产材料的加工性,因此希望有一种快速而可靠的检测方法。已经提出了许多获取可加工性数据的有创造性的方法,有些至今仍在使用。虽然这些方法还有质疑,但它们可用了衡量相同材料加工性能的变化情况。虽然经验表明这些结果有一定的指导意义,但要证明这些包含了质量信息且具有实用

8、价值的加工性能的测试结果的正确性是最困难的。3.钢的热处理热处理是热处理工作者用以改变金属物理性能的方法。钢热处理,有三种基本方法:即淬火、回火和退火。淬火是将钢加热到临界点以上,然后进行急冷。急冷是指(材料)才一合适的介质如水、盐水、油或其他液体中快速冷却。金属在淬硬后,必须进行回火处理。回火是将淬硬的钢重新加热到低于临界点的温度,从而获得所需的物理性能。临界点或临界温度是指钢的物理性能发生某些变化的温度。这些临界点极为重要,因为要使钢很好地硬化就必须把钢加热到上临界温度以上。我们知道某一钢种的临界点后,就能较容易得控制炉温。煤气炉、油炉和电炉是金属热处理最普遍采用的炉子。退火是将钢均匀地加

9、热到通常的淬火温度以上,然后极缓慢地冷却。若工件过硬,无法机加工,或是要重新机加工已经淬硬的零件,这时可进行退火以使钢材软化。退火还可消除机加工时产生的内应力。低碳钢由于含碳量低,因此在经受这种热处理时材质不可能变硬。若欲在低碳钢制成的零件表面获得硬的表面层,就须进行表面硬化处理。氰化是一种表面硬化方法。氰化时,将工作置入氰化钠的溶池中保温530min,(保温时间取决于工件的尺寸和所需的渗透深度)。工件经过这一处理后,再将其淬入水或油中,于是形成了一层厚度为0.010.015的十分硬的表面层(0.2450.381mm)。这类工艺过程也称为表面淬火。渗氮也是一种表面硬化法,它是将钢在热的氨气中放

10、置数小时。在这一条件下,由氨气形成的氮渗入到金属的表面,从而性形成了极硬的表面层。另一种表面硬化法是渗碳。将工件装入盛有渗碳剂(含碳很高的材料)的金属箱中,将箱子密封好并放入炉内,在926C温度下在炉中保持若干小时。渗碳层的深度取决于工件在炉中的保温时间。将工件在某种液体中淬火后,其表层硬而心部软。4.渗碳、渗氮和氰化1.渗碳(1)定义:渗碳是将碳原子渗入固态的铁基合金(如低碳钢)中,以便获得的表面的一种方法。渗碳是通过吸收和扩散两个过程来增加钢表面的含碳量。(2)工艺过程:将低碳钢(约0.20%C或更少)加热到870925C后与气体、固体或液体的含碳物质接触若干小时。用上述方法获得的高碳钢表

11、面在A1 以上的温度淬火使之硬化。(3)特点:表面层深度约为1.27mm。热处理后的硬度为HRC65。由渗碳而引起的工件尺寸变化极微小。在热处理过程中有可能产生变形。(4)典型用途:齿轮的表面硬化。凸轮轴的表面硬化。轴承的表面硬化。(5)方法:根据渗碳介质的不同,有三种常用的渗碳法即: 固体渗碳法用固体渗碳剂。气体渗碳法用合适的碳氢化合物气体。液体渗碳法用熔融的渗碳盐浴。1. 渗氮定义:渗氮是将钢加热,并在某一合适温度下保温,使与部分分解的氨或其他合适的介质保持接触,从而将氮原子渗入到某些钢种(如含有Al和Cr)的表面。用这种方法获得的硬化表层不需灾进行淬火或其他任何进一步的热处理。特点:表面

12、深度约为0.38mm。 硬度极高(维氏硬度为1100)。 工件在渗氮过程中尺寸增大0.0250.050mm。 渗氮层的耐腐蚀性得到改善。典型用途:阀座导轨齿轮量规导套滚珠轴承座圈航空发动机零件航空发动机气缸航空发动机曲轴、飞机螺旋桨轴曲柄销和轴颈2. 氰化定义:氰化是将钢加热到合适温度。并使它与熔融的氰化物保持接触,使碳和氮原子同时渗入钢的表面,在形成微薄的表面层后,接着进行淬火硬化。方法特点:表面层硬度约为0.25mm。硬度约为HRC45。氰化引起尺寸变化极微小。热处理过程中可能产生变形。 典型用途:丝杆。螺帽和螺栓。小齿轮。 通常用氰化法硬化的金属:含碳约为0.20%的普通碳素钢或合金钢。

13、 氰化工艺过程:将低碳钢置于熔融的氰化钠盐浴炉中加热到800870C。根据氰化层所需的深度不同,保温时间可从30分钟直到三个小时之久。1.Cutting Tool MaterialsCutting tools must possess certain mechanical properties in order to function adequately during the cutting operations. These properties include high hardness and the ability to retain it even at the elevated

14、temperatures generated during cutting. They also include toughness, creep and abrasion resistance, and the ability to withstand high bearing pressures. In fact, cutting material differ in the degree to which they possess each of those mechanical properties. Therefore, a cutting material is selected

15、to suit the cutting conditions, such as the workpiece material, cutting speed (production rate),coolants used, and so on. Following is a survey of the commonly used cutting tool materials.Plain carbon steel. Plain carbon steel contains from 0.8 to 1.4 percent carbon and has no additives, and it is s

16、ubjected to heat treatment to increase its hardness. Nevertheless, plain carbon steel is suitable only for making hand tools or when soft metals are machined at low cutting speeds, since it cannot retain its hardness at temperatures above 600F(300C)due to tempering action.Alloy steel. The carbon con

17、tent of alloy steel is similar to that of plain carbon steel. Nevertheless, it contains alloying elements(in limited amounts),as the name suggests. Tools made of alloy steel must also be heat-treated and used only when machining is carried out at low cutting speeds. Again, the temperature generated

18、as a result of cutting, should not exceed 600F(300C)to avoid any tempering action.High-speed steel. High-speed steel(HSS) is a kind of alloy steel that contains a reasonable percentage of alloying elements such as tungsten (18 percent),chromium(4 percent),molybdenum, vanadium, and cobalt. High speed

19、 steel is heat-treated by heating (at two stages),cooling by employing a stream of air, and then tempering it. Tools made of HSS can retain their hardness at elevated temperatures up to 1100 F(600C). These tools are used when relatively high cutting speeds are required. Single point tools, twist dri

20、lls, and milling cutters are generally made of HSS, except when those tools are required for high-productionMachining. Cast hard alloys. Cast hard alloys can be either ferrous or nonferrous and contain about 3 percent carbon, which in turn reacts with the metals to form very hard carbides. Those car

21、bides retain their hardness even at a temperature of about 1650F(900C).Since such a material cannot be worked or machined, it is cast in ceramic molds to take the form of tips, which are mounted onto the holder either by brazing or mechanically. Sintered cemented-carbide tips. Sintered cemented carb

22、ide was developed to eliminate the main disadvantage of the cast alloys, i.e., brittleness. Originally, the composition of that material involved about 82 percent very hard tungsten carbide particles and 18 percent cobalt as a binder. Sintered cemented carbides are always molded to shape by the powd

23、er metallurgy technique, i.e., pressing and sintering. Since it is impossible to manufacture the whole tool of cemented carbide because of the strength consideration, only tips are made of that material; these tips are brazed or mechanically fastened to steel shank, which have the required cutting a

24、ngles. Cemented carbides used to as Widia, taken from the German expression “wie Diamant”, meaning “diamondlike”. This is because they possess extremely high hardness, reaching about 90Rc,and they retain such a hardness even at temperatures of up to 1850F (1000C). Recent developments involve employi

25、ng combinations of tungsten, titanium, and tantalum carbides with cobalt or nickel alloy as binders. The result is characterized by its low coefficient of friction and high abrasion resistance. In fact, cemented-carbide-tip tools are recommended whenever the cutting speeds required or the feed rates

26、 are high and are therefore commonly used in mass production. Recently carbide tips have been coated with nitrates or oxides to increase their wear resistance and service life.Ceramic tips. Ceramic tips consist basically of very fine alumina powder(Al2O3 ),which is molded by pressing and sintering.

27、Ceramics have almost the same hardness as cemented carbides, but they can retain that hardness up to a temperature of 2200F(1100C)and have a very low coefficient of thermal conductivity. Such properties enable cutting to be performed at speeds that range from two to three times the cutting speed whe

28、n carbide tips are employed. Ceramic tips are also characterized by their superior resistance to wear and to the formation of crater cavities, and they require no coolants. Nevertheless, their toughness and bending strength are low, which must be added to their sensitivity to creep loading and vibra

29、tion. Therefore, ceramic tips are recommended only for finishing operation(small depth of cut)at extremely high cutting speed of up to 1800ft/min.(600m/min).Following are the three common types of ceramic tips:1. Oxide tips, consisting mainly of aluminum oxide. They have a white color with some pink

30、 or yellow tint.2. Cermet tips, including alumina and some metal such as titanium or molybdenum. They are dark gray in color.3. Tips that consist of both oxides as well as carbides and they are black in color.Ceramic tips should not be used for machining aluminum because of their affinity to oxygen.

31、Diamond. Diamond pieces are fixed to steel shanks and are used in precision cutting operations. They are recommended for machining aluminum, magnesium, titanium, bronze, rubber, and polymer. When machining metallic materials, a mirror finish can be obtained. 2.The work materialThe term machinability

32、 is often applied to work materials to describe theirmachining properties; it can have several meanings depending on the cutting process under consideration. When it is stated that material A is more machinable than material B, this can mean that a lower tool-wear rate is obtained with material A, o

33、r a better surfrace finish can be achieved with material A, or that less power is required to machine material A. Clerly, with finishing processes, tool wear and surface finish are the most important considerations; with roughing operations, tool wear and power consumption are important. It should b

34、e noted that any statement regarding machinability may only apply under the particular set of circumstances existing when the observation was made. For example, under a given set of conditions a better surface finish may be obtained with material A than material B; however, under another set of cond

35、itions, say with a different tool material, the situation may be reversed. Similar behavior can occur with the other criteria of machinability, tool-wear rate, and power consumption. To complicate the situation further, a certain group of material may be placed in one order of machinability on a too

36、l-wear basis, but in a different order if surface-finish or power-consumption criteria are applied. Clearly, the term machinability can have little meaning except in a loose qualitative sense.Even though the term is meaningful only in a loose qualitative sense, many attempts have been made to obtain

37、 a quantitative measure of machinability-a machinability index or number. A method for producing such an index, if the results were meaningful, would be most helpful, particularly to steel manufacturers who must check the machining properties of their work material and therefore would welcome a quic

38、k and reliable checking method. Many ingenious methods are of doubtful meaning, they can be used to measure the variation in some machining property of material having the same specification. It would be most difficult to prove that the results of these tests yield quantitative information on machin

39、ing properties of practical interest, although experience has shown that these results to give some guide.3.heat treatment of steelHeat treatment is a method by which the heat treater can change the physical properties of a metal. There are three main operation consists of heating the steel above it

40、s critical range and then quenching it, that is rapidly cooling in a suitable medium such as water, brine, oil, or some other liquid. Having been hardened, the metal must be given a tempering treatment which consists of reheating the hardened steel to a temperature below the critical range, thus pro

41、ducing the required physical properties.The critical points or critical temperatures are the temperatures at which a certain change takes place in the physical condition of the steel. These points are very important because in order to properly harden a piece of steel, it must be heated to a tempera

42、ture above the upper critical point. Having known the critical points for a certain steel, we can easily control the heat in the furface. Gas, oil and electric furnaces are the most commonly used for heat treating metals.Annealing is the uniform heating of a metal above usual hardening temperatures,

43、 followed by very slow cooling. Annealing may be carried out either to soften a piece that is too hard to machine or to remachine a piece that has already been hardened. Annealing also relieves internal stresses produced by machining.Low carbon steels do not become hard when subjected to such a heat

44、 treatment because of the small amount of carbon contained. If it is necessary to obtain a hard surface on a part made of such steel, surface hardening operation must be carried out. One of the methods of surface hardening is cyaniding, which is done by keeping operation must be carried out. One of

45、the methods of surface on a part made of such steel, surface hardening operation must be carried out. One of the methods of surface hardening is cyaniding, which is done by keeping the work in a molten bath of sodium cyanide from 5 to 30 minutes, depending on the size of the work and the depth of pe

46、netration required. Having been subjected to such a treatment, the work is then quenched in water or oil, and a very hard case 0.01 to 0.05 inch thick is formed. This process is also called case hardening.Nitriding is also one of the case hardening methods. This process consists of keeping the steel

47、 in hot ammonia gas for some hours. Nitrogen, formed in this condition from ammonia, penetrates into the surface of the metal, thus forming a very hard case.Another method of case hardening is carburization. The work is placed into a metal box containing carburizing material(that is, material with h

48、igh carbon content);the box is closed and placed into a furnace for some hours at the temperature of 926 degrees centigrade. The depth to which the carbon penetrates depend upon the length of time the piece is kept in the furnace. Having been quenched in some liquid queching medium, the work has a hand case and a soft core. 4.carburizing, nitriding and cyaniding1.Carburizing(1)definition Carburizing is a method of introducing carbon into solid iron base alloys such as low carbon steel in order to produce a hard case(surface).Carburizing increases the c

宁ICP备18001539号-1