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1、英文原文：On the discussion of the machinabilityAbstract: The paper is about the concept of mamufacturing engineering and the ways of processing it.It explains the foundamental concept of manufacturing engineeing from the way of example and also offer us some konds of materials can be used in manifacturi
2、ng engineering.Keywords: manufacturing engineering、mterial、concept译文：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 machi
3、nability 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 c
4、utting 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
5、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
6、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 m
7、achinability. 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
8、. 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 sh
9、ort 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, cop
10、per, 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 w
11、hen 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
12、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,
13、” 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 continui
14、ng 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.Mental pipe cutting machine is the one mainly be used in the production of cars,industry and some work of putting materials.The work need to
15、 be finished is the design of body of the machine and the roll of it.It includes the design and calculate of the slowing speed box,.The choose of the electromotor,the design of the gearing,the rev,the measure design of the main deliver parts.Than do the emandation work.After all ,get the data and dr
16、awing the engineering picture.It includes one final assembling picture,two assembling pictures of each parts,some small pictures of the important accessary.The design work we do this time is to the purpose of be used at the place of fanning pipe and draining pipe.This product also can be used at the situation of enhancing the efficiency of production.Make the working effection upon and low down the labor force.Calcium-Deoxidized Steels. An i
