【正文】 本科畢業(yè)設計（論文） 外文譯文 院 （系）： 機電工程學院 專 業(yè)： 機械設計制造及其自動化 姓 名： 學 號： 指導教師評語： 簽名： 年 月 日 外語文獻翻譯 摘自 : 《制造工程與技術（機加工）》（英文版） 《 Manufacturing Engineering and Technology— Machining》 機械工業(yè)出版社 2021 年 3 月第 1 版 頁— 564560P 美 s. 卡爾帕基安 (Serope kalpakjian) 施密德 (Steven ) 著 原文 ： MACHINABILITY The machinability of a material usually defined in terms of four factors: Surface finish and integrity of the machined part。 Tool life obtained。 Force and power requirements。 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 being entangled in the cutting zone. Because of the plex 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 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 socalled freemachining steels. Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (secondphase 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 builtup 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 nonresulfurized 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 ) and is smeared over the toolchip interface during cutting. This behavior has been verified by the presence of high concentrations of lead on the toolside face of chips when machining leaded steels. When the temperature is sufficiently highfor instance, at high cutting speeds and feeds (Secti