制造工程与技术（机加工）》（英文版外语文献翻译
攀枝花学院本科毕业设计（论文）
外文译文
院 （系）： 机电工程学院
专 业： 机械设计制造及其自动化
姓 名： 王 中 蔚
学 号： ZJD02043
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 Technology—Machining》
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 MACHINABILITY
The 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 Steels
Because 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,
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攀枝花学院本科毕业设计（论文）外文译文院（系）：机电工程学院专业：机械设计制造及其自动化姓名：王中蔚学号：ZJD02043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）《ManufacturingEngineeringandTechnology—Machining》机械工业出版社2004年3月第1版美s.卡尔帕基安(Seropekalpakjian)s.r施密德(StevenR.Schmid)著原文：20.9MACHINABILITYThemachinabilityofamaterialusuallydefinedintermsoffourfactors:1...
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作者：闻远设计
分类：课程设计课件资料
价格：15光币
属性：10 页
大小：69KB
格式：DOC
时间：2023-09-29
