The graduation design topic is internal-combustion engine rear oil seal seat. The main contents include the analysis of the components, technical process design and special fixture design, the three main parts.

This thesis of parts are analyzed in detail,On the basis of the parts processing requirements analysis,Ultimately determine the blank material, choose the locating datum, and stay out of the appropriate machining allowance. Comprehensive analysis and formulates the components processing technological route. Get process, need to process in the specific parameters are calculated, calculate the machining allowance, cutting parameters, and according to the calculation results the select tool, also calculated during the processing of the auxiliary time.

Special jig design main steps have design the preparing work before, overall scheme of the sure (positioning error analysis and calculation and clamping force and the determination of calculation), rendering the assembly drawing fixture and fixture drawing. The focal point of design process regulation is mainly develop process route and process calculation. Process route worked fully consider the actual situation, as far as possible to save the production cost, improve the productivity. Process calculation mainly includes process calculation, machine tool selection and mobile time and auxiliary time calculation.

Keywords: Process planning; Special jig design;Machining allowance;Process calculation

摘要III

AbstractIV

1 绪论1

1.1本课题研究的内容及意义1

1.2国内外的发展概况1

1.3本课题应达到的要求1

2 零件的分析2

2.1 内燃机后油封盖的作用2

2.2 零件的工艺分析2

3 内燃机后油封盖工艺规程设计5

3.1 确定零件生产类型及毛坯的制造形式5

3.2 零件材料的选择5

3.3 基准的选择6

3.2.1 粗基准的选择6

3.2.2 精基准的选择7

3.4 拟定工艺路线7

3.4.1零件各表面加工顺序的确定7

3.4.2 工序的组合8

3.4.3 零件工艺路线方案的对比8

3.4.4 零件工艺路线方案的分析与选择10

3.4.5 零件机械加工余量确定10

3.5 各工序所需机床及工艺装备的选择10

3.5.1机床的选择10

3.5.2工艺装备的选择10

3.6 工艺计算11

3.6.1 后表面12

3.6.2 前表面13

3.6.3 底平面20

4 夹具设计23

4.1 机床夹具的概述23

4.1.1 夹具的组成23

4.1.2 机床夹具的功能23

4.1.3 机床夹具需要满足的要求24

4.2 内燃机后油封盖系列夹具设计24

4.2.1 内燃机后油封盖系列夹具的技术要求24

4.2.2 设计夹具的选择26

4.2.3 钻孔专用夹具26

4.2.4 车内外圆专用夹具28

4.2.5 铣底平面专用夹具30

4.3 专用夹具的配合公差32

4.4 定位误差的分析与计算32

4.4.1 定位误差的分析32

4.4.2 定位误差的计算34

4.5夹紧力的的分析与计算36

5 结论与展望38

5.1 结论38

5.2 不足之处及未来展望38

致谢39

参考文献40

附录41

1 绪论

1.1本课题研究的内容及意义

本课题研究的内容是：内燃机后油封盖机械加工工艺规程设计及系列夹具设计。在机械行业，机床夹具是不可缺少的重要工具，能确保机床加工质量、提升生产率、降低生产成本、使劳动强度降低、能够使生产过程实现自动化，专用夹具的采用还能增加机床的作用及使机床的使用价值扩大，因此，系列夹具在机械行业的价值无可估量，专用夹具的采用成为大批量机械加工生产不可或缺的条件之一。

近些年来，随着数控机床、加工中心、柔性制造单元、柔性制造系统等现代或加工设备的广泛应用，使传统的机械加工的指导方法发生了重大变革，夹具的功能已经从过去的装夹、定位、引导刀具，转变为装夹、定位。而数字化的设备加工功能的广大化。给今后夹具的快速定位、快速装夹提出了更高的要求。夹具是机械加工不可缺少的部件，在机床技术向高速、高效、精密、复合、智能、环保方向发展的带动下，夹具技术正朝着高精、高效、模块、组合、通用、经济方向发展。

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内容简介：: 无锡太湖学院机械加工工序卡片产品型号YC41100零（部）件图号HYFG-LJ-01共 8 页产品类型内燃机零（部）件名称内燃机后油封盖第1页车间工序号工序名称材料牌号加工车间40车后端面ZL108毛坯种类毛坯外形尺寸每坯件数每台件数压铸187829.7190.2.11设备名称设备型号设备编号同时加工件数数控车床CJK6136D1夹具编号夹具名称冷却液车后端面专用夹具工序工时准终单件工序号工步内容工艺内容主轴转速（转/分）切削速度（米/分）走刀量（毫米/分）吃刀深度（毫米）走刀次数工时定额机动辅助40车削高度20mm车后端面35019.780.41.010.0790.014编制（日期）审核（日期）会签（日期）标记处数更改文件号签字日期标记处数更改文件号签字日期无锡太湖学院机械加工工序卡片产品型号YC41100零（部）件图号HYFG-LJ-01共 8 页产品类型内燃机零（部）件名称内燃机后油封盖第2页车间工序号工序名称材料牌号加工车间50钻孔ZL108毛坯种类毛坯外形尺寸每坯件数每台件数压铸187829.7190.211设备名称设备型号设备编号同时加工件数加工中心1夹具编号夹具名称冷却液HYFG-01-01钻孔专用夹具工序工时准终单件工序号工步内容工艺内容主轴转速（转/分）切削速度（米/分）走刀量（毫米/分）吃刀深度（毫米）走刀次数工时定额机动辅助50钻7-9mm 钻孔31521.760.421110.160.0350钻8.5mm钻孔63015.830.42410.080.014编制（日期）审核（日期）会签（日期）标记处数更改文件号签字日期标记处数更改文件号签字日期无锡太湖学院机械加工工序卡片产品型号YC41100零（部）件图号HYFG-LJ-01共 8 页产品类型内燃机零（部）件名称内燃机后油封盖第3页车间工序号工序名称材料牌号加工车间60铣小台阶ZL108毛坯种类毛坯外形尺寸每坯件数每台件数压铸187829.7190.211设备名称设备型号设备编号同时加工件数铣床XA61321夹具编号夹具名称冷却液铣小台阶专用夹具工序工时准终单件工序号工步内容工艺内容主轴转速（转/分）切削速度（米/分）走刀量（毫米/分）吃刀深度（毫米）走刀次数工时定额机动辅助60铣1.9mm 平面度0.1铣小台阶37547.100.2310.170.03编制（日期）审核（日期）会签（日期）标记处数更改文件号签字日期标记处数更改文件号签字日期无锡太湖学院机械加工工序卡片产品型号YC41100零（部）件图号HYFG-LJ-01共 8 页产品类型内燃机零（部）件名称内燃机后油封盖第4页车间工序号工序名称材料牌号加工车间70车内圆ZL108毛坯种类毛坯外形尺寸每坯件数每台件数压铸187829.7190.211设备名称设备型号设备编号同时加工件数数控车床CJK6136D1夹具编号夹具名称冷却液HYFG-02-03车内圆专用夹具工序工时准终单件工序号工步内容工艺内容主轴转速（转/分）切削速度（米/分）走刀量（毫米/分）吃刀深度（毫米）走刀次数工时定额机动辅助70车削内径至125mm车内圆50028.260.350.8311.0090.18270车削内径至135.64mm车内圆50028.260.350.8311.0090.182编制（日期）审核（日期）会签（日期）标记处数更改文件号签字日期标记处数更改文件号签字日期无锡太湖学院机械加工工序卡片产品型号YC41100零（部）件图号HYFG-LJ-01共 8 页产品类型内燃机零（部）件名称内燃机后油封盖第5页车间工序号工序名称材料牌号加工车间80车外圆ZL108毛坯种类毛坯外形尺寸每坯件数每台件数压铸187829.7190.211设备名称设备型号设备编号同时加工件数数控车床CJK6136D1夹具编号夹具名称冷却液HYFG-03-03车外圆专用夹具工序工时准终单件工序号工步内容工艺内容主轴转速（转/分）切削速度米/分）走刀量（毫米/分）吃刀深度（毫米）走刀次数工时定额机动辅助80车削外径至141mm 深11.6mm车外圆50028.260.350.8311.0090.182编制（日期）审核（日期）会签（日期）标记处数更改文件号签字日期标记处数更改文件号签字日期无锡太湖学院机械加工工序卡片产品型号YC41100零（部）件图号HYFG-LJ-01共 8 页产品类型内燃机零（部）件名称内燃机后油封盖第6页车间工序号工序名称材料牌号加工车间90铣底平面ZL108毛坯种类毛坯外形尺寸每坯件数每台件数压铸187829.7190.211设备名称设备型号设备编号同时加工件数XA6132铣床XA61321夹具编号夹具名称冷却液HYFG-03-03铣底平面专用夹具工序工时准终单件工序号工步内容工艺内容主轴转速（转/分）切削速度（米/分）走刀量（毫米/分）吃刀深度（毫米）走刀次数工时定额机动辅助90铣95.25mm0.05 平面度0.15铣底平面37547.100.2310.890.16编制（日期）审核（日期）会签（日期）标记处数更改文件号签字日期标记处数更改文件号签字日期无锡太湖学院机械加工工序卡片产品型号YC41100零（部）件图号HYFG-LJ-01共 8 页产品类型内燃机零（部）件名称内燃机后油封盖第7页车间工序号工序名称材料牌号加工车间100钻底孔ZL108毛坯种类毛坯外形尺寸每坯件数每台件数压铸187829.7190.211设备名称设备型号设备编号同时加工件数摇臂钻床1夹具编号夹具名称冷却液钻底孔专用夹具工序工时准终单件工序号工步内容工艺内容主轴转速（转/分）切削速度（米/分）走刀量（毫米/分）吃刀深度（毫米）走刀次数工时定额机动辅助100钻10底孔钻底孔50015.70.42510.10.018编制（日期）审核（日期）会签（日期）标记处数更改文件号签字日期标记处数更改文件号签字日期无锡太湖学院机械加工工序卡片产品型号YC41100零（部）件图号HYFG-LJ-01共 8 页产品类型内燃机零（部）件名称内燃机后油封盖第8页车间工序号工序名称材料牌号加工车间110攻牙ZL108毛坯种类毛坯外形尺寸每坯件数每台件数压铸187829.7190.211设备名称设备型号设备编号同时加工件数攻丝机1夹具编号夹具名称冷却液攻牙专用夹具工序工时准终单件工序号工步内容工艺内容主轴转速（转/分）切削速度（转/分）走刀量（毫米/分）吃刀深度（毫米）走刀次数工时定额机动辅助110攻M10螺纹攻牙1905.971.25511.430.2编制（日期）审核（日期）会签（日期）标记处数更改文件号签字日期标记处数更改文件号签字日期编号无锡太湖学院毕业设计（论文）相关资料题目：内燃机后油封盖机械加工工艺规程设计及系列夹具设计信机系机械工程及自动化专业学号： 0923169 学生姓名：何巍巍指导教师：张大骏（职称：高级工程师）（职称：）2013年5月25日目录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表无锡太湖学院毕业设计（论文）开题报告题目：内燃机后油封盖机械加工工艺规程设计及系列夹具设计信机系机械工程及自动化专业学号： 0923169 学生姓名：何巍巍指导教师：张大骏（职称：高级工程师）（职称：）2012年11月25日课题来源本课题是广西玉林柴油机厂提供图纸委托无锡市宏业机电配件厂加工的柴油机零件，无锡市宏业机电配件厂提供相关资料,此种柴油机在载重汽车及客车上广泛使用。科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）1、工艺是机械产品设计制造过程中十分重要的一个环节，其水平与质量直接影响到产品的最终制造质量及成本运行。2、加工技术正向高度信息化、自动化、智能化的方向发展，各种现代的加工方法也不断地创造和完善，如快速成型技术、激光加工、电加工和射流加工等已相当广泛的应用到加工中去，而这些使工艺设计也带来巨大的进步。3、作为机械专业的本科毕业生采用此类课题可以培养学生认识机械加工生产准备工作是怎样一个过程，可以受到理论与实践相结合的锻炼。研究内容1、机械加工工艺规程的编制，结合具体工厂的条件和发展前景进行考虑。2、同样结合具体工厂的现有生产条件和发展前景设计专用（不少于三副）拟采取的研究方法、技术路线、实验方案及可行性分析采用组织分析零件的具体结构，加工精度要求，表面粗糙度要求，制定出初步的加工方案，然后组织学生下工厂参观、实习、实地了解工厂出现的生产条件，发展展望及具体的生产水平。然后在此基础上编制工艺规程，填写工艺文件，设计专用夹具，待初步完成后，再回工厂征集意见，加以改进，定稿。研究计划及预期成果研究计划：2012年11月12日-2012年12月2日：按照任务书要求查阅论文相关参考资料，填写毕业设计开题报告书。2012年12月3日-2013年3月1日：参加实训及填写毕业实习报告。2013年3月4日-2013年3月8日：学习并翻译一篇与毕业设计相关的英文材料。2013年3月11日-2013年3月22日：工艺路线及夹具方案的确定。2013年3月25日-2013年4月12日：夹具图及Solidworks模组图的绘制。2013年4月15日-2013年4月19日：工艺规程设计和工艺过程卡、工序卡设计。2013年4月22日-2013年5月10日：工艺计算和夹具设计。2013年5月13日-2013年5月25日：毕业论文撰写和修改工作。预期成果：工艺规程、工艺卡片、工序卡片夹具总图及主要的零件图、Solidworks模组图设计说明书、相关资料特色或创新之处工艺规程可以适用于一般中小型工厂的普通通用机床，也能改进后用于专用机床，或加工中心，适用于范围较广。已具备的条件和尚需解决的问题现有广西玉柴机器集团有限公司生产内燃机后油封盖的零件图样，委托加工工厂的现有生产条件及技术状况，特别是已有的生产经验。目前缺少设计手册、资料等，对检测条件也不够清楚其它资料也缺乏。指导教师意见该生已查阅大量国内外参考资料,已对课题有了一定了解,计划详细可行,同意开题。指导教师签名：2012年 11月 25日教研室（学科组、研究所）意见教研室主任签名：年月日系意见主管领导签名：年月日无锡太湖学院毕业设计（论文）外文资料翻译信机系机械工程及自动化专业院（系）：信机系专业：机械工程及自动化班级：机械94班姓名：何巍巍学号： 0923169 外文出处： Manufacturing Engineering and TechnologyMachining 附件： 1.译文；2.原文；3.评分表 2013年5月25日英文原文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.Machinability Of SteelsBecause steels are among the most important engineering materials, 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), 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.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.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 and with the selection of appropriate processing parameters, such as ductile-regime cutting.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.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.中文译文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。钢的可机加工性因为钢是最重要的工程材料之一，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），尽管其在室温下对力学性能没有影响。因为硫化铁的构成，硫能严重的减少钢的热加工性，除非有足够的锰来防止这种结构的形成。在室温下，二次磷化钢的机械性能依赖于变形的硫化锰夹杂物的定位（各向异性）。二次磷化钢具有更小的延展性，被单独生成来提高机加工性。其它不同金属的机加工性尽管越软的品种易于生成积屑瘤，但铝通常很容易被机加工，导致了很差的表面光洁性。高的切削速度，高的前角和高的后角都被推荐了。有高含量的矽的锻铝合金铸铝合金也许具有磨蚀性，它们要求更硬的刀具材料。尺寸公差控制也许在机加工铝时会成为一个问题，因为它有膨胀的高导热系数和相对低的弹性模数。铝的重量轻和耐腐蚀，是其性能的两大突出特点。纯铝的密度约为2.7g/cm3,仅为铁、铜密度的三分之一。无论是固体铝或熔融铝，其密度均随着纯度的提高而降低；同等纯度的熔融铝的密度，则随温度的提高而降低。铝对自然界的水（含海水）、大气中的各种元素，以及油料与各种化学物品，都良好的耐蚀性。这是由于铝的化学性质及其活泼，其最特殊的性能是具有同氧（特别是空气中的氧）强烈结合的倾向，铝在空气中被其表面生成一层厚度约为2x10-4mm的致密氧化膜（三氧化二铝）所覆盖，防止了铝的继续氧化，从而使铝具有良好的耐蚀性。铝合金能承受压力加工。可加工成各种形态、规格的铝合金材。主要用于制造航空器材、建筑用门窗等。形变铝合金又分为不可热处理强化型铝合金和可热处理强化型铝合金。不可热处理强化型不能通过热处理来提高机械性能，只能通过冷加工变形来实现强化，它主要包括高纯铝、工业高纯铝、工业纯铝以及防锈铝等。可热处理强化型铝合金可以通过淬火和时效等热处理手段来提高机械性能，它可分为硬铝、锻铝、超硬铝和特殊铝合金等。纯铝的力学性能不高，不适宜制作承受较大载荷的结构零件。为了提高铝的力学性能在纯铝中加入某些合金元素制成合金，常加入的合金元素有铜、镁、铬、锌、硅、锰、镍、钴、钛及锶等，稀土元素在某些合金中加入。这些合金元素加入后通过以下几个方面对铝进行强化。铝合金热处理后可以得到过饱和的铝基固溶体。这种过饱和铝基固溶体在室温或加热到某一温度时，其强度和硬度随时间和延长而增高，但塑性降低。这个过程就称时效。时效过程中使合金的强度、硬度增高的现象称为时效强化或时效硬化。当铝中加入的合金元素含水量超过其极限溶解度时，淬火加热时便有一部分不能溶入固溶体的第二相出现称之为过剩相。在铝合金中过剩相多为硬而脆的金属间化合物。它们在合金中起阻碍滑移和位错运动的作用，使强度、硬度提高，而塑性、韧性降低。合金中过剩相的数量愈多，其强化效果愈好，但过剩相多时，由于合金变脆而导致强度、塑性降低。在铝合中添加微量元素细化组织是提高铝合金力学性能的另一种重要手段。变形铝合金中添加微量钛、锆、铍、锶以及稀土元素，它们能形成难熔化合物，在合金结晶时作为非自发晶核，起细化晶粒作用，提高合金的强度和塑性。铸造铝合金中常加入微量元素作变质处理来细化合金组织，提高强度和塑性。变质处理对不能热处理强化或强化效果不大的铸造铝合金和变形铝合金具有特别重要的意义。比如在铝硅铸造铝合金中加入微量钠或钠盐或锑作变质剂进行变质处理，细化组织可以显著提高塑性和强度。同样在铸造铝合金中加入少量锰、铬、钴等元素能使杂质铁形成的板块状或

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