工件与刀具材料外文文献翻译、中英文翻译

1、3Work and tool materialsIn Chapter 2, the emphasis is on the mechanical, thermal and friction conditions of chip formation. The different work and tool materials of interest are introduced only as exam- ples. In this chapter, the materials become the main interest. Table 3.1 summarizes some of the m

2、ain applications of machining, by industrial sector and work material group, while Table 3.2 gives an overview of the classes of tool materials that are used. In Section 3.1 data will be presented of typical specific forces, tool stresses and temperatures generated when machining the various work gr

3、oups listed in Table 3.1. In Section 3.2 the properties of the tools that resist those stresses and temperatures will be described.A metals machinability is its ease of achieving a required production of machined components relative to the cost. It has many aspects, such as energy (or power) consump

4、tion, chip form, surface integrity and finish, and tool life. Low energy consumption, short (broken) chips, smooth finish and long tool life are usually aspects of good machinability. Some of these aspects are directly related to the continuum mechanical and thermal conditions of theTable 3.1 Some m

5、achining activities by work material alloy and industrial sectorAlloy systemGeneral engineeringAuto-motiveAerospaceProcess engineeringInformation technologyCarbon andStructuresPower train,Power train,StructuresPrinteralloy steelsfasteners,steering,control andspindles andpower train,suspension,landin

6、gmechanismshydraulicshydraulicsgearfastenersStainlessFor corrosionTurbineFor corrosionsteelsresistancebladesresistanceAluminiumStructuresEngine blockAirframeFor corrosionScanningand pistonsspars, skinsresistancemirrors, discsubstratesCopperFor corrosionresistanceNickelTurbineHeatblades andexchangers

7、,discsand corrosionresistanceTitaniumCompressor/CorrosionairframeresistanceTable 3.2 Recommended tool and work material combinationsSoft non- ferrous (Al, Cu)Carbon/ low alloy steelsHardened tool and die steelsCast ironNickel-based alloysTitanium alloysHigh speed steelO/O/x/x/x/xCarbide (inc. coated

8、)O/O/OOCermet/xxxxCeramicx/OO/OxcBN/xx/OOOPCDxxxx good; O all right in some conditions; possible but not advisable; x to be avoided.Table 3.3 Mechanical, thermal and materials factors affecting machinabilityMain tools for studyProcess variablesMachinability attributeCutting speed and feedChip formTo

9、ol shapeTool forcesApplied mechanicsWork mechanical and thermal propertiesPower consumptionand thermal analysisTool thermal propertiesTool stresses and temperaturesTool failure propertiesTool failureChip/tool friction lawsSurface integrity and finishMaterials engineeringWork/tool wear interactionsTo

10、ol wear and life3.1 Work material characteristics in machiningmachining process. In principle, they may be predicted by mechanical and thermal analy- sis (but at the current time some are beyond prediction). Other aspects, principally tool life, depend not only on the continuum surface stresses and

11、temperatures that are generated but also on microstructural, mechanical and chemical interactions between the chip and the tool. Table 3.3 summarizes these relations and the principal disciplines by which they may be studied (perhaps chip/tool friction laws should come under both the applied mechani

12、cs and materials engineering headings?). This chapter is mainly concerned with the work materials mechanical and thermal properties, and tool thermal and failure properties, which affect machinability. Tool wear and life are so important that a separate chapter, Chapter 4, is devoted to these subjec

13、ts.According to the analysis in Chapter 2, cutting and thrust forces per unit feed and depth of cut, and tool stresses, are expected to increase in proportion to the shear stress on the primary shear plane, other things being equal. This was sometimes written k and some- times kmax.Forces also incre

14、ase the smaller is the shear plane angle and hence the larger is thestrain in the chip. The shear plane angle, however, reduces the larger is the strain harden- ing in the primary shear region, measured by Dk/kmax (equation (2.7). Thus, kmax and Dk/kmax are likely to be indicators of a materials mac

15、hinability, at least as far as tool forces and stresses and power consumption are concerned. Figure 3.1 gathers information on the typical values of these quantities for six different groups of work materials that are impor- tant in machining practice. The data for steels exclude quench hardened mat

16、erials as, untilFig. 3.1 Shear stress levels and work hardening severities of initially unstrained, commonly machined, aluminium, copper, iron (b.c.c. and f.c.c.), nickel and titanium alloysrecently, these were not machinable. The data come from compression testing at room temperature and at low str

17、ain rates of initially unworked metal. The detail is presented in Appendix 4.1. Although machining generates high strain rates and temperatures, these data are useful as a first attempt to relate the severity of machining to work material plastic flow behaviour. A more detailed approach, taking into

18、 account variations of material flow stress with strain rate and temperature, is introduced in Chapter 6.Work heating is also considered in Chapter 2. Temperature rises in the primary shear zone and along the tool rake face both depend on fUworktanf/kwork. Figure 3.2(a) summa-rizes the conclusions f

19、rom equation (2.14) and Figures 2.17(a) and 2.18(b). In the primaryshear zone the dimensionless temperature rise DT(rC)/k depends on fUworktanf/kwork and the shear strain g. Next to the rake face, the additional temperature rise depends on fUworktanf/kwork and the ratio of tool to work thermal condu

20、ctivity, K*. Figure 3.2(b) summarizes the typical thermal properties of the same groups of work materials whose mechanical properties are given in Figure 3.1. The values recorded are from room temper- ature to 800C. Appendix 4.2 gives more details.Figures 3.1 and 3.2 suggest that the six groups of a

21、lloys may be reduced to three as far as the mechanical and thermal severity of machining them is concerned. Copper and aluminium alloys, although showing high work hardening rates, have relatively low shear stresses and high thermal diffusivities. They are likely to create low tool stresses and low

22、temperature rises in machining. At the other extreme, austenitic steels, nickel and titanium alloys have medium to high shear stresses and work hardening rates and low thermal diffu- sivities. They are likely to generate large tool stresses and temperatures. The body centred cubic carbon and alloy s

23、teels form an intermediate group.The behaviours of these three different groups of alloys are considered in Sections 3.1.3 to 3.1.5 of this chapter, after sections in which the machining of unalloyed metals isFig. 3.2 Thermal aspects of machining: (a) a summary of heating theory and (b) thermal prop

24、erty ranges of Al, Cu, Fe, Ni and Ti alloysdescribed. It will be seen that these groups do indeed give rise to three different levels of tool stress and temperature severity. This is demonstrated by presenting representative experimentally measured specific cutting forces (forces per unit feed and d

25、epth of cut) and shear plane angles for these groups as a function of cutting speed. Then, primary shear zone shear stress k, average normal contact stress on the rake face (sn)av and average rake face contact temperature (Trake)av are estimated from the cutting data. A picture is built up of the st

26、ress and temperature conditions that a tool must survive in machining these materials.The primary shear plane shear stress is estimated from(Fc cos f FT sin f)sin fk = (3.1)fdThe average normal contact stress on the tool rake face is estimated from the measured normal component of force on the rake

27、face, the depth of cut and the chip/tool contact length lc:Fc cos a FT sin a(sn)av = (3.2)lcdlc is taken, from the mean value data of Figure 2.9(a), to be cos(f a)lc = 1.75f m + tan(f a) (3.3)sin fFinally, temperatures are estimated after the manner summarized in Figure 3.2.The machining data come m

28、ainly from results in the authors possession. The exception are data on the machining of the aluminium alloy Al2024 (Section 3.1.2), which are from results by Kobayashi and Thomsen (1959). The data on machining elemental metals come from the same experiments on those metals considered by Trent in hi

29、s book (Trent, 1991).3.1.1 Machining elemental metalsAlthough the elemental metals copper, aluminium, iron, nickel and titanium have little commercial importance as far as machining is concerned (with the exception of aluminium used for mirrors and disk substrates in information technology applicati

30、ons), it is interest- ing to describe how they form chips: what specific forces and shear plane angles are observed as a function of cutting speed. The behaviour of alloys of these materials can then be contrasted with these results. Figure 3.3 shows results from machining at a feed of 0.15 mm with

31、high speed steel (for copper and aluminium) and cemented carbide (for iron, nickel and titanium) tools of 6 rake angle.At the lowest cutting speeds (around 30 m/min), except for titanium, the metals machine with very large specific forces, up to 8 GPa for iron and nickel and around 4 GPa for copper

32、and aluminium. These forces are some ten times larger than the expected shear flow stresses of these metals (Figure 3.1) and arise from the very low shear plane angles, between 5 and 8, that occur. These shear plane angles give shear strains in the primary shear zone of from 7 to 12. As cutting spee

33、d increases to 200 m/min, the shear plane angles increase and the specific forces are roughly halved. Further increases in speed cause much less variation in chip flow and forces. The titanium material is an exception. Over the whole speed range, although decreases of specific force and increases of

34、 shear plane angle with cutting speed do occur, its shear plane angle is larger and its specific forces areFig. 3.3 Cutting speed dependence of specific forces and shear plane angles for some commercially pure metals (f =0.15 mm, = 6)Fig. 3.4 Process stresses, derived from the observations of Figure

35、 3.3Fig. 3.5 Temperatures estimated from the observations of Figure 3.3smaller than for the other, more ductile, metals. A reduction in forces and an increase in shear angle with increasing speed, up to a limit beyond which further changes do not occur, is a common observation that will also be seen

36、 in many of the following sections.Although the forces fall with increasing speed, the process stresses remain almost constant. Figure 3.4 shows aluminium to have the smallest primary shear stress, k, followed by copper, iron, nickel and titanium.The estimated average normal stresses (sn)av lie betw

37、een 0.5k and 1.0k. This would place the maximum normal contact stresses (which are between two and three times theaverage stress) in the range k to 3k. This is in line with the estimates in Chapter 2, Figure2.15.The different thermal diffusivities of the five metals result in different temperature v

38、ari- ations with cutting speed (Figure 3.5). For copper and aluminium, with k taken to be 110 and 90 mm2/s respectively (Appendix 4.2), fUworktanf/kwork hardly rises to 1, even at thecutting speed of 300 m/min. Figure 3.2 suggests that then the primary shear temperaturerise dominates the secondary (

39、rake) heating. The actual increase in temperature shown inFigure 3.5 results from the combined effect of increasing fraction of heat flowing into the chip and reducing shear strain as cutting speed rises.Iron and nickel, with k taken to be 15 and 20 mm2/s respectively, machine withfUworktanf/kwork i

40、n the range 1 to 10 in the conditions considered. In Figure 3.5, the primary shear and average rake face temperatures are distinctly separated. Over much of the speed range, the temperature actually falls with increasing cutting speed. This unusual behaviour results from the reduction of strain in t

41、he chip as speed increases.Finally, titanium, with k taken to be 7.5 mm2/s, machines with fUworktanf/kwork from 7 to 70. The rake face heating is dominant and a temperature in excess of 800C is estimatedat the cutting speed of 150 m/min.工件与刀具材料在第二章中，强调的是有关切削成因中机械、热量和摩擦条件。不同的工件和刀具材料的性能仅仅通过例子来介绍。在本章中，

42、材料成为其主要的特性。表3.1通过工业部门和工件材料部门总结了主要的应用加工，然而表3.2给出了刀具材料类别不同应用的概述。在表3.1节中（材料）数据将表现出独特而且具体的因素，列在表3.1中的是当加工不同工件种类时刀具产生的温度和压力。在表3.2中描述的是不同性能的刀具所能承受工作温度与压力。一种金属材料的可加工性是能够简单实现所需要求的加工工件的相对成本。它包括许多方面，例如能源（或动力）的消耗。磨屑的形成，表面的完整性，和刀具的寿命。低的能量消耗，短的（或断的磨屑），光洁度和具有较长寿命的刀具通常表现出良好的切削性能的方面。这些方面的一部分直接关系到机械的连续运行和加工过程的热学条件。原

43、则上，这些方面可通过机械的力学性能和热分析进行预测(但目前有些是超出预测的)。还有其他方面，主要是刀具的寿命，不仅取决于表面的应力和连续变化的温度，而且也取决于切削和刀具之间的微观结构、机械和化学性能。表3.1主要总结了它们之间关系的一些科学（也许是切削或刀具在应用力学和材料工程下的研究规则）。这一章主要涉及的是影响切削性能的工件材料力学性能和热稳定性以及刀具的热学和破坏性能。另外刀具的磨损和寿命是非常重要的。在第四章中有一独立的一章来研究这一学科。表3.1是通过工件材料合金和工业部门表现出来加工活动碳素合金钢液压结构系统紧固件传动系统控制的液压紧固件动力装置控制的起落架结构装置打印机主轴和工

44、作机制合金体系 普通工程 汽车动力 航天 加工工程 信息技术不锈钢铝合金防腐蚀处理结构柴油机机体和活塞机身涡轮叶片防腐蚀处理扫描阀瓣机制铜防腐蚀结构镍涡轮叶片和阀瓣热交换和防腐蚀是结构钛压缩机/机体耐腐蚀表3.2是涉及的刀具和工件材料的组合软有色金属（铜、铝）低碳合金钢硬质刀具和模具钢铸铁镍基合金钢钛合金钢高速钢0/0/x/x/x/x硬质合金钢0/0/00金属陶瓷/xxxx陶瓷x/00/0x立方氮化硼/xx/000金刚石xxxx表示好0在某些条件下非常好很可能不可取x应该避免的表3.3是机械、热学性能和材料的加工性能的影响因素刀具的主要研究过程变量切削性能加工属性应力热学材料工程切削速度和吃刀

45、深度工作的力学性能和热稳定性刀具热性能刀具失效性能切削刀具摩擦规则工件刀具相互磨损作用切削形式刀具应力功耗刀具压力和温度刀具失效表面完整性刀具的磨损和寿命3.1加工过程中工件的材料特性根据在第二章中的分析结果，每次切削和驱动力的深度和刀具的应力，将增加主要剪切面上的剪切应力，其他情况都是相同的。优势这样的情况被写成K和Kmax。压力也会增加剪切面应力的减少，因此在切削中应增大相应的角度。剪切面上角度的变化，然而降低在最初选择的剪切区域更大的应力，通过测量Kmax。因此，Kmax和DK/Kmax很可能被用来表示一种材料的的切削性能，至少刀具的应力和能量的消耗是有关的。图3.1收集了关于这六个典型

46、的物理量工件材料，这些特性在实际加工中是非常重要的。到目前为止，数据中排除了淬火硬质钢，并且这些都是不可加工的。数据来自于在较低温度下的房间和最初没应用过的应变率较低的压力测试，在附录4.1中提出了关于这些内容的一些细节。虽然在加工过程中会产生变形，高温，但是这些数据对于通过相关材料塑性流动性加工行为是非常有用的。一种更详细的方法是同时考虑物料流量变化压力与应变速率和温度将在第6章中介绍。图3.1铝合金、铜、铁、镍、钛合金剪切应力和加工硬化工件的加热也在第2章中被提到。温度的升高根据fUworktanf/kwork在最初的剪切面和沿着刀具的前刀面图3.2（a）总结了从方程是2.14和2.18刀

47、2.17（a）和（b）。在最初选择的剪切带中没有量纲和温度DT（rc）/凯西取决于fUworktanf/kwork的剪切应变，和相邻的前面，和额外的温度增加取决于fUworktanf/kwork。图3.2（b）总结了典型的热性能物质结构在图3.1中给出的工件的力学特性。这重要的温度从室温到800摄氏度。而在附录4.2中给出了更多的详细情况。数字表格3.1和3.2表示只要材料的力学性能和热学性能在加工中相关则六组合金有可能减少到三组合金。铜和铝合金虽然表现出高的加工硬化率，并且有较低的压力和较好的热性能。它们很可能创造出较低的刀具应力和较低的温度上升。在另一个极端方面，奥氏体钢、镍、钛等合金中剪切应力和加工硬化率和低热率。它们很可能会产生较大的刀具应力和温度。中心立方碳合金钢则会形成一个中心集合。图3.2加工的热学方面（a）加工热理论的总结（b）