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关键词：: ca6140机床后托架机械加工工艺夹具设计工艺装备工装机械加工 831001

资源描述：

CA6140普通车床后托架【831001】零件的机械加工工艺规程及工艺装备设计【镗孔Φ40、Φ30.2、Φ25.5孔】

后托架的机械加工工艺及工艺装备设计

CA6140机床后托架的机械加工工艺及夹具设计

CA6140机床后托架的机械加工工艺及工艺装备设计

基于普通机床的后托架及【831001】的机械加工工艺规程及【镗孔Φ40、Φ30.2、Φ25.5孔】夹具的设计开发

CA6140车床后托架加工工艺及夹具设计

CA6140机床后托架【831001】的机械加工工艺及【镗孔Φ40、Φ30.2、Φ25.5孔】夹具设计

CA6140机床后托架【831001】的机械加工工艺及夹具设计【铣底平面】【镗孔Φ40、Φ30.2、Φ25.5孔】【钻顶面四孔】

CA6140机床后托架的加工工艺编制及夹具设计【铣底平面】【镗孔Φ40、Φ30.2、Φ25.5孔】

后托架【831001】零件的加工工艺及镗三杠孔夹具设计

CA6140车床后托架【831001】的加工工艺规程及工序工艺装备设计【铣底平面】【钻三杠孔Φ40、Φ30.2、Φ25.5孔】【钻顶面四孔φ13 、φ20、φ10 孔】

CA6140车床后托架【831001】的加工工艺及【钻底孔】夹具设计

后托架【831001】的夹具设计【铣底平面】【镗三杠孔Φ40、Φ30.2、Φ25.5孔】【钻顶面四孔φ13 、φ20、φ10 工序】【工艺装备类】【优秀】【带UG三维零件图】【7张CAD图纸全套】【HTJ023】

【带工艺过程、卡片】【带任务书+自检表+开题报告】【47页@正文18700字】【详情如下】【需要咨询购买全套设计请加QQ1459919609 】

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中期检查表_.doc

任务书_.doc

外语文献翻译_.doc

夹具装配图及夹具零件图合计6张.dwg

封面_.doc

工序卡片.doc

工艺卡片_.dwg

开题报告_.doc

成绩评定表_.doc

教师评阅表_.doc

机械加工工艺过程卡片_.doc

材料清单_.doc

目录_.wps

答辩资格审查表_.doc

评阅评语表_.doc

说明书.doc

读书笔记_.doc

钻夹具装配图.dwg

钻孔夹具体.dwg

钻模支架.dwg

铣底面夹具装配图.dwg

铣面夹具体.dwg

镗孔夹具装配图.dwg

零件图_.dwg

课题任务书

课题名称CA6140车床后托架机械工艺规程及夹具设计

内容及任务

1.设计内容：制订年产5000台CA6140机床后托架的加工工艺；

2.设计主视图中的三孔的加工夹具；

3.设计铣底面的夹具；

4.设计俯视图中4孔的加工夹具；

5.提交夹具装配图、零件图、加工工艺卡片、设计说明书及精度分析等相关设计分析结果。

拟达到的要求或技术指标

1.完成不少于3张零号图纸的结构设计图、装配图和零件图，其中应包含一张以上用计算机绘制的具有中等难度的1号图纸，同时至少有折合1号图幅以上的图纸用手工绘制；

2.按要求格式独立撰写不少于12000字的设计说明书，且“摘要”不少于400字；

3.至少翻译一篇本专业外文文献（10000个以上印刷符号），并附译文；

4.查阅到10篇以上与题目相关的文献；

5.查阅相关资料，分析所给题目的零件结构工艺性，编排出该零件的合理的加工工艺过程，选择各加工工序的合理的切削用量，计算各工序的定额，填写零件的加工工艺卡片；

6.完成给定加工面的夹具设计（须有方案分析比较、优选）

7.保证夹具强度前提下、注意外形美观，各部分比例协调；

8.自选一个重要模具成型零件，编制加工工艺过程卡；

9.编制工艺工序卡。

完成毕业设计的选题和开题报告；

进行毕业实习及调研；

进行工艺及结构设计；

绘制零件图和装配图；

对整个设计进行合理性检查；

撰写设计说明书(论文)及毕业答辩的准备；

毕业设计答辩。

主要参考资料[1] 许晓旸，专用机床设备设计[M]，重庆：重庆大学出版社，2003。

[2] 孙已德，机床夹具图册[M]，北京：机械工业出版社，1984：20-23。

[3] 贵州工学院机械制造工艺教研室，机床夹具结构图册[M]，贵阳：贵州任命出版社，1983：42-50。

[4] 东北重型机械学院等，机床夹具设计手册[M]，上海：上海科学技术出版社，1979。

[5] 孟少龙，机械加工工艺手册第1卷[M]，北京：机械工业出版社，1991。

[6] 《金属机械加工工艺人员手册》修订组，金属机械加工工艺人员手册[M]，上海：上海科学技术出版社，1979。

摘要

机械加工工艺是实现产品设计，保证产品质量，节约能源，降低消耗的重要手段。本课题研究CA6140车床后托架加工工艺规程。首先通过对零件图的分析，了解工件的结构形式，明确了具体的技术要求，从而对工件各组成表面选择合适的加工方法。再拟订较为合理的工艺规程，充分体现质量、生产率和经济性的统一。

在生产过程中，使生产对象（原材料，毛坯，零件或总成等）的质和量的状态发生直接变化的过程叫工艺过程，如毛坯制造，机械加工，热处理，装配等都称之为工艺过程。在制定工艺过程中，要确定各工序的安装工位和该工序需要的工步，加工该工序的机车及机床的进给量，切削深度，主轴转速和切削速度，该工序的夹具，刀具及量具，还有走刀次数和走刀长度，最后计算该工序的基本时间，辅助时间和工作地服务时间。

关键词工序；工艺；工步；加工余量；定位方案；夹紧力

ABSTRACT

He machine-finishing craft realizes the product design, guaranteed the product quality, saves the energy, reduces the consumption the important method. After this topic studies the CA6140 lathe the bracket processing technological process. First through to the detail drawing analysis, understood the work piece the structural style, has been clear about the concrete specification, thus to work piece each composition surface choice appropriate processing method. Again drafts the more reasonable technological process, fully manifests the quality, the productivity and the efficient unification .

Enable producing the target in process of production (raw materials, the blank , state of quality and quantity on part become always ) take place direct course of change ask craft course, if the blank is made, machining, heat treatment , assemble etc. and call it the craft course. In the course of making the craft , is it confirm every erector location and worker step that process need this of process to want, the locomotive of processing , this process , and the entering the giving amount of the lathe, cut depth , the rotational speed of the main shaft and speed of cutting, the jig of this process, the cutter and measuring tool, a one hundred sheets of number of times still leaves and a one hundred sheets of length leaves, calculate basic time of this process , auxiliary time and service time of place of working finally.

Keywords The process；worker one；worker's step；the surplus of processing；orient the scheme；clamp strength

1 CA6140机床后托架加工工艺1

1.1 CA6140机床后托架的工艺分析1

1.2 CA6140机床后托架的工艺要求及工艺分析1

1.2.1 CA6140机床后托架的技术要求2

1.3 加工工艺过程2

1.4 确定各表面加工方案3

1.4.1 在选择各表面及孔的加工方法时，要综合考虑以下因素3

1.4.2 平面的加工3

1.4.3孔的加工方案3

1.5 确定定位基准4

1.5.1 粗基准的选择4

1.5.2 精基准选择的原则5

1.6 工艺路线的拟订5

1.6.1工序的合理组合5

1.6.2 工序的集中与分散6

1.6.3 加工阶段的划分7

1.6.4 加工工艺路线方案的比较7

1.7 CA6140机床后托架的偏差，加工余量，工序尺寸及毛坯尺寸的确定10

1.7.1 毛坯的结构工艺要求10

1.7.2 CA6140机床后托架的偏差计算10

1.8 确定切削用量及基本工时（机动时间）13

1.8.1 工序1：粗、精铣底面13

1.8.2 工序2 粗、半精、精镗CA6140侧面三杠孔14

1.8.3 工序3：钻顶面四孔21

1.8.4 工序4：钻侧面两孔24

1.9 时间定额计算及生产安排26

1.9.1 粗、精铣底面27

1.9.2 镗侧面三杠孔27

1.9.3 钻顶面四孔28

2专用夹具设计30

2.1 铣平面夹具设计30

2.1.1 研究原始质料30

2.1.2 定位基准的选择30

2.1.3 切削力及夹紧分析计算30

2.1.4 误差分析与计算32

2.1.5 夹具设计及操作的简要说明32

2.2 镗孔夹具设计32

2.2.1 研究原始质料32

2.2.2 定位基准的选择33

2.2.3 切削力及夹紧力的计算33

2.2.4 误差分析与计算35

2.3钻顶面四孔夹具设计36

2.3.1 研究原始质料36

2.3.2 定位基准的选择36

2.3.3 切削力及夹紧力的计算36

2.3.4 误差分析与计算37

2.3.5 夹具设计及操作的简要说明38

结束语39

参考文献40

致谢41

附录42

1 CA6140机床后托架加工工艺

1.1 CA6140机床后托架的工艺分析

CA6140机床后托架的是CA6140机床的一个重要零件，因为其零件尺寸较小，结构形状也不是很复杂，但侧面三杠孔和底面的精度要求较高，此外还有顶面的四孔要求加工，但是对精度要求不是很高。后托架上的底面和侧面三杠孔的粗糙度要求都是，所以都要求精加工。其三杠孔的中心线和底平面有平面度的公差要求等。因为其尺寸精度、几何形状精度和相互位置精度，以及各表面的表面质量均影响机器或部件的装配质量，进而影响其性能与工作寿命，因此它的加工是非常关键和重要的。

1.2 CA6140机床后托架的工艺要求及工艺分析

图1.1 CA6140机床后托架零件图

一个好的结构不但要应该达到设计要求，而且要有好的机械加工工艺性，也就是要有加工的可能性，要便于加工，要能够保证加工质量，同时使加工的劳动量最小。而设计和工艺是密切相关的，又是相辅相成的。设计者要考虑加工工艺问题。工艺师要考虑如何从工艺上保证设计的要求。

1.2.1 CA6140机床后托架的技术要求

其加工有三组加工。底面、侧面三孔、顶面的四个孔、以及左视图上的两个孔。

(1) 以底面为主要加工的表面，有底面的铣加工，其底面的粗糙度要求是，平面度公差要求是0.03。

(2) 另一组加工是侧面的三孔，分别为，，，其表面粗糙度要求要求的精度等级分别是，，。

(3) 以顶面为主加工面的四个孔，分别是以和为一组的阶梯空，这组孔的表面粗糙度要求是，，以及以和的阶梯孔，其中是装配铰孔，其中孔的表面粗糙度要求是，，是装配铰孔的表面粗糙度的要求是。

(4) CA6140机床后托架毛坯的选择为金属行浇铸，因为生产率很高，所以可以免去每次造型。

单边余量一般在，结构细密，能承受较大的压力，占用生产的面积较小。因为CA6140机床后托架的重量只有3.05kg,而年产量是5000件，由[7]《机械加工工艺手册》表2.1-3可知是中批量生产。

参考文献

[1] 许晓旸.专用机床设备设计[M].重庆：重庆大学出版社，2003

[2] 孙已德.机床夹具图册[M].北京：机械工业出版社，1984.20~23

[3] 贵州工学院机械制造工艺教研室.机床夹具结构图册[M].贵阳：贵州任命出版社，1983.42~50

[4] 东北重型机械学院等，机床夹具设计手册[M].上海：上海科学技术出版社，1979

[5] 孟少龙.机械加工工艺手册第1卷[M].北京：机械工业出版社，1991

[6] 《金属机械加工工艺人员手册》修订组.金属机械加工工艺人员手册[M].上海：上海科学技术出版社，1979

[7] 李洪.机械加工工艺手册[M].北京：机械工业出版社，1990

[8] 马贤智.机械加工余量与公差手册[M].北京：中国标准出版社，1994

[9] 上海金属切削技术协会.金属切削手册[M].上海：上海科学技术出版社，1984

[10] 周永强.高等学校毕业设计指导[M].北京：中国建材工业出版社，2002

[11] 刘文剑，曹天河，赵维.夹具工程师手册[M].哈尔滨：黑龙江科学技术出版社，1987

[12] 余光国，马俊，张兴发.机床夹具设计[M].重庆：重庆大学出版社，1995

[13] 东北重型机械学院，洛阳农业机械学院，长春汽车厂工人大学.机床夹具设计手册[M]，上海：上海科学技术出版社，1980

[14] 李庆寿.机械制造工艺装备设计适用手册[M].银州：宁夏人民出版社，1991

[15] 廖念钊，莫雨松，李硕根.互换性与技术测量[M].中国计量出版社，2000.9~19

[16] 王光斗，王春福.机床夹具设计手册[M].上海：上海科学技术出版社，2000

[17] 乐兑谦.金属切削刀具.机械工业出版社，2005.4~17

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内容简介：: 湖南工学院毕业设计(论文)工作中期检查表题目CA6140车床后托架加工工艺及夹具设计学生姓名王勋班级学号机本0807班08201420734专业机械设计制造及其自动化指导教师填写学生开题情况已开题学生调研及查阅文献情况已调研、查阅毕业设计（论文）原计划有无调整无学生是否按计划执行工作进度是学生是否能独立完成工作任务是学生的英文翻译情况已翻译学生每周接受指导的次数及时间三次，一次一个小时毕业设计（论文）过程检查记录情况已记录学生的工作态度在相应选项划“”认真一般较差尚存在的问题及采取的措施：尚存的问题：1、调研不是很深入，文献资料查阅不够充分； 2、设计有些延后，未完全跟上计划执行工作进度； 3、英文翻译不完善。采取的措施：1、深入调研，加紧查阅相关文献资料； 2、加快设计步伐，赶上计划执行工作进度； 3、查阅相关外文书籍，完善英文翻译。指导教师签字：年月日系部意见：负责人签字：年月日2012 届毕业设计（论文）课题任务书系：机械工程学院专业：机械设计制造及自动化指导教师任芝兰崔晓东学生姓名王勋课题名称CA6140车床后托架机械工艺规程及夹具设计内容及任务1.设计内容：制订年产5000台CA6140机床后托架的加工工艺；2.设计主视图中的三孔的加工夹具；3.设计铣底面的夹具；4.设计俯视图中4孔的加工夹具；5.提交夹具装配图、零件图、加工工艺卡片、设计说明书及精度分析等相关设计分析结果。拟达到的要求或技术指标1.完成不少于3张零号图纸的结构设计图、装配图和零件图，其中应包含一张以上用计算机绘制的具有中等难度的1号图纸，同时至少有折合1号图幅以上的图纸用手工绘制；2.按要求格式独立撰写不少于12000字的设计说明书，且“摘要”不少于400字；3.至少翻译一篇本专业外文文献（10000个以上印刷符号），并附译文；4.查阅到10篇以上与题目相关的文献；5.查阅相关资料，分析所给题目的零件结构工艺性，编排出该零件的合理的加工工艺过程，选择各加工工序的合理的切削用量，计算各工序的定额，填写零件的加工工艺卡片；6.完成给定加工面的夹具设计（须有方案分析比较、优选）7.保证夹具强度前提下、注意外形美观，各部分比例协调；8.自选一个重要模具成型零件，编制加工工艺过程卡；9.编制工艺工序卡。进度安排起止日期工作内容备注3.053.153.163.263.274.124.134.204.215.105.115.275.286.02完成毕业设计的选题和开题报告；进行毕业实习及调研；进行工艺及结构设计；绘制零件图和装配图；对整个设计进行合理性检查；撰写设计说明书(论文)及毕业答辩的准备；毕业设计答辩。主要参考资料1 许晓旸，专用机床设备设计M，重庆：重庆大学出版社，2003。2 孙已德，机床夹具图册M，北京：机械工业出版社，1984：20-23。3 贵州工学院机械制造工艺教研室，机床夹具结构图册M，贵阳：贵州任命出版社，1983：42-50。4 东北重型机械学院等，机床夹具设计手册M，上海：上海科学技术出版社，1979。5 孟少龙，机械加工工艺手册第1卷M，北京：机械工业出版社，1991。6 金属机械加工工艺人员手册修订组，金属机械加工工艺人员手册M，上海：上海科学技术出版社，1979。教研室意见年月日系主管领导意见年月日湖南工学院本科毕业设计（论文）外文译文院（系）：机械工程学院专业：机械设计制造及其自动化姓名：王勋学号： 08201420734 指导教师评语：签名：年月日外语文献翻译摘自: 制造工程与技术（机加工）（英文版） Manufacturing Engineering and TechnologyMachining 机械工业出版社 2004年3月第1版美 s. 卡尔帕基安(Serope kalpakjian) s.r 施密德(Steven R.Schmid) 著原文：20.9 MACHINABILITYThe machinability of a material usually defined in terms of four factors:1、 Surface finish and integrity of the machined part;2、 Tool life obtained;3、 Force and power requirements;4、 Chip control. Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone.Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below.20.9.1 Machinability Of SteelsBecause steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-called free-machining steels.Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in resulfurized steels.Phosphorus in steels has two major effects. It strengthens the ferrite, causing increased hardness. Harder steels result in better chip formation and surface finish. Note that soft steels can be difficult to machine, with built-up edge formation and poor surface finish. The second effect is that increased hardness causes the formation of short chips instead of continuous stringy ones, thereby improving machinability.Leaded Steels. A high percentage of lead in steels solidifies at the tip of manganese sulfide inclusions. In non-resulfurized grades of steel, lead takes the form of dispersed fine particles. Lead is insoluble in iron, copper, and aluminum and their alloys. Because of its low shear strength, therefore, lead acts as a solid lubricant (Section 32.11) and is smeared over the tool-chip interface during cutting. This behavior has been verified by the presence of high concentrations of lead on the tool-side face of chips when machining leaded steels.When the temperature is sufficiently high-for instance, at high cutting speeds and feeds (Section 20.6)the lead melts directly in front of the tool, acting as a liquid lubricant. In addition to this effect, lead lowers the shear stress in the primary shear zone, reducing cutting forces and power consumption. Lead can be used in every grade of steel, such as 10xx, 11xx, 12xx, 41xx, etc. Leaded steels are identified by the letter L between the second and third numerals (for example, 10L45). (Note that in stainless steels, similar use of the letter L means “low carbon,” a condition that improves their corrosion resistance.)However, because lead is a well-known toxin and a pollutant, there are serious environmental concerns about its use in steels (estimated at 4500 tons of lead consumption every year in the production of steels). Consequently, there is a continuing trend toward eliminating the use of lead in steels (lead-free steels). Bismuth and tin are now being investigated as possible substitutes for lead in steels.Calcium-Deoxidized Steels. An important development is calcium-deoxidized steels, in which oxide flakes of calcium silicates (CaSo) are formed. These flakes, in turn, reduce the strength of the secondary shear zone, decreasing tool-chip interface and wear. Temperature is correspondingly reduced. Consequently, these steels produce less crater wear, especially at high cutting speeds.Stainless Steels. Austenitic (300 series) steels are generally difficult to machine. Chatter can be s problem, necessitating machine tools with high stiffness. However, ferritic stainless steels (also 300 series) have good machinability. Martensitic (400 series) steels are abrasive, tend to form a built-up edge, and require tool materials with high hot hardness and crater-wear resistance. Precipitation-hardening stainless steels are strong and abrasive, requiring hard and abrasion-resistant tool materials.The Effects of Other Elements in Steels on Machinability. The presence of aluminum and silicon in steels is always harmful because these elements combine with oxygen to form aluminum oxide and silicates, which are hard and abrasive. These compounds increase tool wear and reduce machinability. It is essential to produce and use clean steels.Carbon and manganese have various effects on the machinability of steels, depending on their composition. Plain low-carbon steels (less than 0.15% C) can produce poor surface finish by forming a built-up edge. Cast steels are more abrasive, although their machinability is similar to that of wrought steels. Tool and die steels are very difficult to machine and usually require annealing prior to machining. Machinability of most steels is improved by cold working, which hardens the material and reduces the tendency for built-up edge formation.Other alloying elements, such as nickel, chromium, molybdenum, and vanadium, which improve the properties of steels, generally reduce machinability. The effect of boron is negligible. Gaseous elements such as hydrogen and nitrogen can have particularly detrimental effects on the properties of steel. Oxygen has been shown to have a strong effect on the aspect ratio of the manganese sulfide inclusions; the higher the oxygen content, the lower the aspect ratio and the higher the machinability.In selecting various elements to improve machinability, we should consider the possible detrimental effects of these elements on the properties and strength of the machined part in service. At elevated temperatures, for example, lead causes embrittlement of steels (liquid-metal embrittlement, hot shortness; see Section 1.4.3), although at room temperature it has no effect on mechanical properties.Sulfur can severely reduce the hot workability of steels, because of the formation of iron sulfide, unless sufficient manganese is present to prevent such formation. At room temperature, the mechanical properties of resulfurized steels depend on the orientation of the deformed manganese sulfide inclusions (anisotropy). Rephosphorized steels are significantly less ductile, and are produced solely to improve machinability.20.9.2 Machinability of Various Other Metals Aluminum is generally very easy to machine, although the softer grades tend to form a built-up edge, resulting in poor surface finish. High cutting speeds, high rake angles, and high relief angles are recommended. Wrought aluminum alloys with high silicon content and cast aluminum alloys may be abrasive; they require harder tool materials. Dimensional tolerance control may be a problem in machining aluminum, since it has a high thermal coefficient of expansion and a relatively low elastic modulus.Beryllium is similar to cast irons. Because it is more abrasive and toxic, though, it requires machining in a controlled environment.Cast gray irons are generally machinable but are. Free carbides in castings reduce their machinability and cause tool chipping or fracture, necessitating tools with high toughness. Nodular and malleable irons are machinable with hard tool materials.Cobalt-based alloys are abrasive and highly work-hardening. They require sharp, abrasion-resistant tool materials and low feeds and speeds.Wrought copper can be difficult to machine because of built-up edge formation, although cast copper alloys are easy to machine. Brasses are easy to machine, especially with the addition pf lead (leaded free-machining brass). Bronzes are more difficult to machine than brass.Magnesium is very easy to machine, with good surface finish and prolonged tool life. However care should be exercised because of its high rate of oxidation and the danger of fire (the element is pyrophoric).Molybdenum is ductile and work-hardening, so it can produce poor surface finish. Sharp tools are necessary.Nickel-based alloys are work-hardening, abrasive, and strong at high temperatures. Their machinability is similar to that of stainless steels.Tantalum is very work-hardening, ductile, and soft. It produces a poor surface finish; tool wear is high.Titanium and its alloys have poor thermal conductivity (indeed, the lowest of all metals), causing significant temperature rise and built-up edge; they can be difficult to machine.Tungsten is brittle, strong, and very abrasive, so its machinability is low, although it greatly improves at elevated temperatures.Zirconium has good machinability. It requires a coolant-type cutting fluid, however, because of the explosion and fire.20.9.3 Machinability of Various MaterialsGraphite is abrasive; it requires hard, abrasion-resistant, sharp tools.Thermoplastics generally have low thermal conductivity, low elastic modulus, and low softening temperature. Consequently, machining them requires tools with positive rake angles (to reduce cutting forces), large relief angles, small depths of cut and feed, relatively high speeds, and proper support of the workpiece. Tools should be sharp.External cooling of the cutting zone may be necessary to keep the chips from becoming “gummy” and sticking to the tools. Cooling can usually be achieved with a jet of air, vapor mist, or water-soluble oils. Residual stresses may develop during machining. To relieve these stresses, machined parts can be annealed for a period of time at temperatures ranging from to (to), and then cooled slowly and uniformly to room temperature.Thermosetting plastics are brittle and sensitive to thermal gradients during cutting. Their machinability is generally similar to that of thermoplastics.Because of the fibers present, reinforced plastics are very abrasive and are difficult to machine. Fiber tearing, pulling, and edge delamination are significant problems; they can lead to severe reduction in the load-carrying capacity of the component. Furthermore, machining of these materials requires careful removal of machining debris to avoid contact with and inhaling of the fibers.The machinability of ceramics has improved steadily with the development of nanoceramics (Section 8.2.5) and with the selection of appropriate processing parameters, such as ductile-regime cutting (Section 22.4.2).Metal-matrix and ceramic-matrix composites can be difficult to machine, depending on the properties of the individual components, i.e., reinforcing or whiskers, as well as the matrix material.20.9.4 Thermally Assisted MachiningMetals and alloys that are difficult to machine at room temperature can be machined more easily at elevated temperatures. In thermally assisted machining (hot machining), the source of heata torch, induction coil, high-energy beam (such as laser or electron beam), or plasma arcis forces, (b) increased tool life, (c) use of inexpensive cutting-tool materials, (d) higher material-removal rates, and (e) reduced tendency for vibration and chatter.It may be difficult to heat and maintain a uniform temperature distribution within the workpiece. Also, the original microstructure of the workpiece may be adversely affected by elevated temperatures. Most applications of hot machining are in the turning of high-strength metals and alloys, although experiments are in progress to machine ceramics such as silicon nitride. SUMMARYMachinability is usually defined in terms of surface finish, tool life, force and power requirements, and chip control. Machinability of materials depends not only on their intrinsic properties and microstructure, but also on proper selection and control of process variables.译文：20.9 可机加工性一种材料的可机加工性通常以四种因素的方式定义：1、分的表面光洁性和表面完整性。2、刀具的寿命。3、切削力和功率的需求。4、切屑控制。以这种方式，好的可机加工性指的是好的表面光洁性和完整性，长的刀具寿命，低的切削力和功率需求。关于切屑控制，细长的卷曲切屑，如果没有被切割成小片，以在切屑区变的混乱，缠在一起的方式能够严重的介入剪切工序。因为剪切工序的复杂属性，所以很难建立定量地释义材料的可机加工性的关系。在制造厂里，刀具寿命和表面粗糙度通常被认为是可机加工性中最重要的因素。尽管已不再大量的被使用，近乎准确的机加工率在以下的例子中能够被看到。20.9.1 钢的可机加工性因为钢是最重要的工程材料之一（正如第5章所示），所以他们的可机加工性已经被广泛地研究过。通过宗教铅和硫磺，钢的可机加工性已经大大地提高了。从而得到了所谓的易切削钢。二次硫化钢和二次磷化钢硫在钢中形成硫化锰夹杂物（第二相粒子），这些夹杂物在第一剪切区引起应力。其结果是使切屑容易断开而变小，从而改善了可加工性。这些夹杂物的大小、形状、分布和集中程度显著的影响可加工性。化学元素如碲和硒，其化学性质与硫类似，在二次硫化钢中起夹杂物改性作用。钢中的磷有两个主要的影响。它加强铁素体，增加硬度。越硬的钢，形成更好的切屑形成和表面光洁性。需要注意的是软钢不适合用于有积屑瘤形成和很差的表面光洁性的机器。第二个影响是增加的硬度引起短切屑而不是不断的细长的切屑的形成，因此提高可加工性。含铅的钢钢中高含量的铅在硫化锰夹杂物尖端析出。在非二次硫化钢中，铅呈细小而分散的颗粒。铅在铁、铜、铝和它们的合金中是不能溶解的。因为它的低抗剪强度。因此，铅充当固体润滑剂并且在切削时，被涂在刀具和切屑的接口处。这一特性已经被在机加工铅钢时，在切屑的刀具面表面有高浓度的铅的存在所证实。当温度足够高时例如，在高的切削速度和进刀速度下铅在刀具前直接熔化，并且充当液体润滑剂。除了这个作用，铅降低第一剪切区中的剪应力，减小切削力和功率消耗。铅能用于各种钢号，例如10XX，11XX，12XX，41XX等等。铅钢被第二和第三数码中的字母L所识别（例如，10L45）。（需要注意的是在不锈钢中，字母L的相同用法指的是低碳，提高它们的耐蚀性的条件）。然而，因为铅是有名的毒素和污染物，因此在钢的使用中存在着严重的环境隐患（在钢产品中每年大约有4500吨的铅消耗）。结果，对于估算钢中含铅量的使用存在一个持续的趋势。铋和锡现正作为钢中的铅最可能的替代物而被人们所研究。脱氧钙钢一个重要的发展是脱氧钙钢，在脱氧钙钢中矽酸钙盐中的氧化物片的形成。这些片状，依次减小第二剪切区中的力量，降低刀具和切屑接口处的摩擦和磨损。温度也相应地降低。结果，这些钢产生更小的月牙洼磨损，特别是在高切削速度时更是如此。不锈钢奥氏体钢通常很难机加工。振动能成为一个问题，需要有高硬度的机床。然而，铁素体不锈钢有很好的可机加工性。马氏体钢易磨蚀，易于形成积屑瘤，并且要求刀具材料有高的热硬度和耐月牙洼磨损性。经沉淀硬化的不锈钢强度高、磨蚀性强，因此要求刀具材料硬而耐磨。钢中其它元素在可机加工性方面的影响钢中铝和矽的存在总是有害的，因为这些元素结合氧会生成氧化铝和矽酸盐，而氧化铝和矽酸盐硬且具有磨蚀性。这些化合物增加刀具磨损，降低可机加工性。因此生产和使用净化钢非常必要。根据它们的构成，碳和锰钢在钢的可机加工性方面有不同的影响。低碳素钢（少于0.15%的碳）通过形成一个积屑瘤能生成很差的表面光洁性。尽管铸钢的可机加工性和锻钢的大致相同，但铸钢具有更大的磨蚀性。刀具和模具钢很难用于机加工，他们通常再煅烧后再机加工。大多数钢的可机加工性在冷加工后都有所提高，冷加工能使材料变硬并且减少积屑瘤的形成。其它合金元素，例如镍、铬、钳和钒，能提高钢的特性，减小可机加工性。硼的影响可以忽视。气态元素比如氢和氮在钢的特性方面能有特别的有害影响。氧已经被证明了在硫化锰夹杂物的纵横比方面有很强的影响。越高的含氧量，就产生越低的纵横比和越高的可机加工性。选择各种元素以改善可加工性，我们应该考虑到这些元素对已加工零件在使用中的性能和强度的不利影响。例如，当温度升高时，铝会使钢变脆（液体金属脆化，热脆化

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