【正文】 社， 2020 [11]薛啟翔 .沖壓模具結(jié)構(gòu)圖冊(cè) .北京：化學(xué)工業(yè)出版社， 2020： 154～ 159 [12]張建中 .機(jī)械設(shè)計(jì)基礎(chǔ) .北京：高等教育出版社， 2020： 30～ 46 [13]《模具制造手冊(cè)》編寫組編著 .模具制造手冊(cè) .北京：機(jī)械工業(yè)出版社，2020 [14]楊占堯 .沖壓模具典型 結(jié)構(gòu)圖例 .北京：化工工業(yè)出版社， 2020 [15]王曉江 .模具設(shè)計(jì)與制造專業(yè)英語(yǔ) .北京：機(jī)械工業(yè)出版社， 2020 [16]Sally （第 6 版） .牛津大學(xué)出版社，2020 [17]丁松聚 .冷沖模技術(shù) .北京：機(jī)械工業(yè)出版社， 2020 [18] 韓森和 . 冷沖壓工藝與模具設(shè)計(jì)與制造 . 北 京 ： 高 等 教 育 出版社， 2020 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 36 外文資料翻譯 PLAIN CARBON STEEL Any steelmaking process is capable of producing a product that has % or less carbon. With this small amount of carbon, the properties approach of pure iron with maximum ductility and minimum strength. Maximum ductility is desirable from the standpoint of ease in deformation processing and service use. Minimum strength is desirable for deformation processing. However, higher strengths than that obtainable with this low carbon are desirable from the standpoint of product design. The most practical means of increasing the strength is by the addition or retention of some carbon. However, it should be fully understood that any increase of strength over that pure iron can be obtained only at the expense of some loss of ductility, and the final choice is always a promise of some de gree. Because of the difficulty of position control or the additional operation of increasing carbon content, the cost of higher carbon, higher strength steel is greater than of low carbon. Plain Carbon Steels Most Used. Because of their low cost, the majority of steels used are plain carbon steels. These consist of iron bined with carbon concentrated in there ranges classed as low carbon,medium carbon, and high carbon. With the exception of manganese used to control sulphur, other elements are present only in small enough quantities to be considered as impurities, though in some cases they may have minor effect on properties of the material. Low Carbon. Steel with approximately 6 to 25 points of carbo n (%～ %)are rated as low carbon steels and are rarely hardened by heat treatment because the low carbon content permits so little formation of hard magnesite that the process is relatively ineffective. Enormous tonnages of these low carbon steels are processed in such structural shapes as sheet, 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 37 strip,rod,plate,pipe,and wire. A large portion of the material is cold worked in its final processing to improve its hardness, strength, and surface finish grades containing 20 points or less of carbon are susceptible to considerable plastic flow and are frequently used as deepdrawn products or may be used as a ductile core for casehardened material. The low lain carbon steels are reality brazed, welded, and fed. Medium Carbon. The medium carbon steels (% ～ %)contain sufficient carbon that they may be heat treated for desirable strength, hardness, machinability, or other properties. The hardness of plain carbon steels in this range cannot be increased sufficiently for the material to serve satisfactorily as cutting tools,but the loadcarrying capacity of the steels can be raised considerably, while still retaining sufficient ductility for good toughness. The majority of the steel is furnished in the hotrolled condition and is often machined for final finishing. It can be welded,but is mor e difficult to join by this method than the low carbon steel because of structural changes caused by welding heat in localized areas. High Carbon. High carbon steel contains from 50 to 160 points o f carbon (%～ %). This group of steels is classed as tool and die steel, in which hardness is the principal property desired. Because of the fast reaction time and resulting low hardenability, and its associated danger of distortion or cracking, it is seldom possible to develop fully of heattreathardened plain carbon steel is low pared to that of alloy steels with the same strength, but, even so, carbon steel is frequently used because of its lower cost. ALLOY STEELS Although plain carbon steels work well for many uses and are the cheapest steels and therefore the most used, they cannot pletely fulfill the requirements for some work. Individual or groups of properties can be improved by addition of various elements in the form of alloys. Even plain carbon steels are alloys of at least iron, carbon, and manganese, but the term alloy steel refers to steels containing elements other than these in controlled 洛陽(yáng)理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 38 quantities greater than impurity concentration or, in the case of manganese, greater than %. Alloys Affect Harde nability. Interest in hardenability is indirect. Hardenability is usually thought of most in connection with depthhardening ability in a full hardening operation. However, with the isothermal transformation curves shifted to the right, the properties fing operations, the materially usually air cools. Any alloy generally shifts the transformation curves to the right, which with air cooling results in finer pearlite than would be formed in a plain carbon steel. This finer pearlite has higher hardness and strength, which has an effect on machinability and may lower ductility. Weldability. The generally bad influence of alloys on weldability is a further reflection of the influence on hardenability. With alloys present is a further reflection of the influence on hardenability. With alloys prese nt during the rapid cooling taking place in the welding area, hard, nonductile structures are formed in the steel and frequently lead to cracking and distortion. Grain Size and Toughness. Nickel in particular has a very beneficial effect by retarding grain growth in the austenite range. As with hardenability, it is the secondary effects of grain refinement that are noted in properties. A finer grain structure may actually have less hardenability, but it has its most pronounced effect on toughne