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CA6140车床后托架【831001】的机械加工工艺规程及【铣底平面】工序工艺装备设计【优秀】【夹具类】【带UG三维零件图】【3张CAD图纸全套】【HTJ012】

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CA6140车床后托架【831001】的机械加工工艺规程及【铣底平面】工序工艺装备设计【优秀】【HTJ012】.rar

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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

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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】的机械加工工艺规程及工艺装备设计【铣底平面】【钻三杠孔Φ40、Φ30.2、Φ25.5孔】【钻底孔φ13 、φ20、φ10 孔】【优秀】【夹具类】【带UG三维零件图】【3张CAD图纸全套】【HTJ011】

【带工艺过程、卡片】【带任务书+自检表+开题报告】【40页@正文12700字】【详情如下】【需要咨询购买全套设计请加QQ1459919609 】

任务书.doc

加工三杠孔钻床夹具装配图.dwg

外语文献翻译.doc

外语翻译.doc

夹具装配图及零件图.dwg

工艺卡片.dwg

开题报告.doc

自检表.doc

说明书.doc

钻三杠孔夹具体.dwg

钻孔夹具.dwg

钻底孔夹具体.dwg

铣底面夹具体.dwg

铣底面夹具装配图.dwg

零件图.dwg

任务书

1.毕业设计(论文)题目:CA6140机床后托架加工工艺及夹具设计

2.学生完成全部任务期限: 2006 年 6 月 9 日

3.任务要求：（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。

注意：多人做一题时，设计方案、内容不能相同

4.实验(调验)部分内容要求:

（1）、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；

（2）、完成给定加工面的夹具设计（须有方案分析比较、优选），每套夹具须完成装配图1张，夹具主要零、部件2-3张；

（3）、编写夹具的设计说明书，字数在15000字以上。

5.文献查阅及翻译要求:

（1）、机械加工工艺人员手册；

（2）、机床家具设计手册；

（3）、机床夹具图册；

（4）、翻译有关机械制造方面10000个字符以上的外文资料，字数不得少于三千。

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。

机床夹具设计是工艺装备设计中的一个重要组成部分，在整个机械加工过程中，夹具除了夹紧、固定被加工零件外，还要求保证加工零件的位置精度、提高加工生产率。

本课题在设计的过程当中，深入生产实际，进行调查研究，吸取国内外先进技术，制定出合理的设计方案，在进行具体设计。

关键词产品设计，后托架，加工工艺，夹具

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 .

Engine bed jig design is in a craft equipment design important constituent, in the entire machine-finishing process, the jig except clamps, fixes is processed outside the components, but also requests guarantee processing components position precision, enhancement processing productivity .

This topic in the middle of the design process, penetrates the production reality, conducts the investigation and study, absorbs the domestic and foreign advanced technologies, formulates the reasonable design proposal, is carrying on the concrete design .

Keywords shift the product design，latter bracket ，processing craft，jig

摘要 Ⅰ

ABSTRACTⅡ

1 CA6140车床后托架的加工工艺设计3

1.1 CA6140车床后托架的结构特点和技术要求3

1.2 CA6140车床后托架的材料、毛坯和热处理3

1.2.1 毛坯材料及热处理3

1.2.2 毛坯的结构确定4

1.3 工艺过程设计中应考虑的主要问题4

1.3.1 加工方法选择的原则4

1.3.2 加工阶段的划分4

1.3.3 工序的合理组合5

1.3.4 加工顺序的安排5

1.4 CA6140车床后托架的机械加工工艺过程分析5

1.4.1 CA6140车床后托架零件图分析5

1.4.2 CA6140车床后托架的加工工艺的路线7

1.5 CA6140车床后托架的工序设计12

1.5.1 工序基准的选择12

1.5.2 工序尺寸的确定12

1.5.3 加工余量的确定14

1.5.4 确定各工序的加工设备和工艺装备15

1.5.5 确定切削用量及工时定额16

2 专用夹具设计26

2.1 铣平面夹具设计26

2.1.1 研究原始质料26

2.1.2 定位基准的选择26

2.1.3 切削力及夹紧分析计算26

2.1.4 误差分析与计算27

2.1.5 夹具设计及操作的简要说明28

2.2 钻三杠孔夹具设计28

2.2.1 研究原始质料28

2.2.2 定位基准的选择29

2.2.3 切削力及夹紧力的计算29

2.2.4 误差分析与计算30

2.2.5 夹具设计及操作的简要说明31

2.3 钻底孔夹具设计31

2.3.1 研究原始质料31

2.3.2 定位基准的选择31

2.3.3 切削力及夹紧力的计算31

2.3.4 误差分析与计算32

2.3.5 夹具设计及操作的简要说明33

结论34

参考文献35

致谢36

1 CA6140车床后托架的加工工艺设计

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，是企业进行生产准备，计划调度，加工操作，安全生产，技术检测和健全劳动组织的重要依据，也是企业上品种，上质量，上水平，加速产品更新，提高经济效益的技术保证。

在实际生产中，由于零件的生产类型、材料、结构、形状、尺寸和技术要求等不同，针对某一零件，往往不是单独在一种机床上，用某一种加工方法就能完成的，而是要经过一定的工艺过程才能完成其加工。因此，不仅要根据零件的具体要求，结合现场的具体条件，对零件的各组成表面选择合适的加工方法，还要合理地安排加工顺序，逐步地把零件加工出来。

对于某个具体零件，可采用几种不同的工艺方案进行加工。虽然这些方案都可以加工出来合格的零件，但从生产效率和经济效益来看，可能其中有种方案比较合理且切实可行。因此，必须根据零件的具体要求和可能的加工条件等，拟订较为合理的工艺过程。

1.1 CA6140车床后托架的结构特点和技术要求

由零件图1-1可得：CA6140车床后托架是铸造件，从整体形状来看类似长方体。根据要求主要是加工孔和底平面。具体特点和技术要求如下：

① 精加工孔, , 要求达到的精度等级为。粗糙度为，且以底平面为基准，要求平行度公差为，主要满足加工孔的位置精度。

② 其他各个孔的加工都要以底平面为定位基准。所以，底平面的形位公差要达到设计要求。

③ 、粗糙度为；为锥孔，且粗糙度为。

④ 其余未注要求的加工表面为不去除材料加工。

1.2 CA6140车床后托架的材料、毛坯和热处理

1.2.1 毛坯材料及热处理

灰铸体一般的工作条件：

① 承受中等载荷的零件。

② 磨檫面间的单位面积压力不大于490KPa。

毛坯的热处理

灰铸铁（HT150）中的碳全部或大部分以片状石墨方式存在铸铁中，由于片状石墨对基体的割裂作用大，引起应力集中也大；因此，使石墨片得到细化，并改善石墨片的分布，可提高铸铁的性能。可采用石墨化退火，来消除铸铁表层和壁厚较薄的部位可能出现的白口组织（有大量的渗碳体出现），以便于切削加工。

1.2.2 毛坯的结构确定

毛坯的结构工艺要求

CA6140车床后托架为铸造件，对毛坯的结构工艺有一定要求：

① 铸件的壁厚应和合适，均匀，不得有突然变化。

② 铸造圆角要适当，不得有尖角。

③ 铸件结构要尽量简化，并要有和合理的起模斜度，以减少分型面、芯子、并便于起模。

④ 加强肋的厚度和分布要合理，以免冷却时铸件变形或产生裂纹。

⑤ 铸件的选材要合理，应有较好的可铸性。

毛坯形状、尺寸确定的要求

设计毛坯形状、尺寸还应考虑到：

① 各加工面的几何形状应尽量简单。

② 工艺基准以设计基准相一致。

③ 便于装夹、加工和检查。

④ 结构要素统一，尽量使用普通设备和标准刀具进行加工。

在确定毛坯时，要考虑经济性。虽然毛坯的形状尺寸与零件接近，可以减少加工余量，提高材料的利用率，降低加工成本，但这样可能导致毛坯制造困难，需要采用昂贵的毛坯制造设备，增加毛坯的制造成本。因此，毛坯的种类形状及尺寸的确定一定要考虑零件成本的问题但要保证零件的使用性能。在毛坯的种类

形状及尺寸确定后，必要时可据此绘出毛坯图。

1.3 工艺过程设计中应考虑的主要问题

1.3.1 加工方法选择的原则

① 所选加工方法应考虑每种加工方法的经济、精度要求相适应。

② 所选加工方法能确保加工面的几何形状精度，表面相互位置精度要求。

③ 所选加工方法要与零件材料的可加工性相适应。

④ 加工方法要与生产类型相适应。

⑤ 所选加工方法企业现有设备条件和工人技术水平相适应。

参考文献

[1] 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

[2] 李洪．机械加工工艺手册[M]．北京：机械工业出版社，1990

[3]《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，1997

[4] 于骏一．典型零件制造工艺[M]．北京：机械工业出版社，1989

[5] 王季琨、沈中伟、刘锡珍．机械制造工艺学[M]．天津：天津大学出版社，2004

[6] 莫雨松、李硕根等．互换性与技术测量[M]．中国计量出版社，1988

[7] 方昆凡．公差与配合技术手册[M]．北京：北京出版社，1984

[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] 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

[11] 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

[12] 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。

[13] 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

[14] 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：贵州人民出版社，1983

[15] 孙已德．机床夹具图册[M]．北京：机械工业出版社，1984

[16] 成大先．机械设计手册单行本连接与紧固[M]．北京，化学工业出版社，2004

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内容简介：: 毕业设计(论文)任务书机制专业 2002 年级2006 年3 月28 日批准专业负责人: 乔水明发给学生: 王中蔚贺兵 1.毕业设计(论文)题目:CA6140机床后托架加工工艺及夹具设计 2.学生完成全部任务期限: 2006 年 6 月 9 日3.任务要求：（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。注意：多人做一题时，设计方案、内容不能相同 4.实验(调验)部分内容要求:（1）、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；（2）、完成给定加工面的夹具设计（须有方案分析比较、优选），每套夹具须完成装配图1张，夹具主要零、部件2-3张；（3）、编写夹具的设计说明书，字数在15000字以上。 5.文献查阅及翻译要求:（1）、机械加工工艺人员手册；（2）、机床家具设计手册；（3）、机床夹具图册；（4）、翻译有关机械制造方面10000个字符以上的外文资料，字数不得少于三千。 6.发出日期: 2006 年 2 月 18 日指导教师: 卢宗彪 (签名)完成任务日期: 2006 年 6 月 9 日学生:贺兵(签名)攀枝花学院本科毕业设计（论文）外文译文院（系）：专业：姓名：学号：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，见1.4.3节），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

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