外文及翻译 Heattreatmentofmetal

1、:院毕业设计（论文）外文翻译Heat treatme nt of metal金属热处理 机械工程系机械设计制造及其自动化2012-05原文Heat treatme nt of metalThe gen erally acce pted defi niti on for heat treat ing metals and metal alloys is“heati ng andcooli ng a solid metal or alloy in a way so as to obta in sp ecific con diti ons or prop erties.Heati ng forthe

2、 sole purpose of hot work ing (as in forging op erati ons) is excluded from this defi niti on.Likewise ,the types of heat treatment that are sometimes used for products such as glass or plastics are alsoexcluded from coverage by this definition .Tran sformati on CurvesThe basis for heat treatment is

3、 the time-temperature-transformation curves or TTT curves where ,in a single diagram all the three parameters are plotted . Because of the shape of the curves, they arealso sometimes called C-curves or S-curves .To plot TTT curves, the particular steel is held at a given temperature and the structur

4、e isexamined at predetermined intervals to record the amount of transformation taken place . It is knownthat the eutectoid steel (T80) under equilibrium conditions contains, all austenite above 723C,whereas below , it is the p earlite. To form p earlite, the carb on atoms should diffuse to formceme

5、ntite . The diffusi on being a rate pro cess, would require sufficie nt time for compi etetransformation of austenite to pearlite . From different samples , it is possible to note the amount of thetransformation taking place at any temperature . These points are then plotted on a graph with time and

6、temperature as the axes. Through these points , transformation curves can be plotted as shown in Fig.1for eutectoid steel . The curve at extreme left represents the time required for the transformation ofaustenite to pearlite to start at any given temperature . Similarly , the curve at extreme right

7、 representsthe time required for compieting the transformation . Between the two curves are the pointsrep rese nti ng p artial tran sformati on. The horiz on tal lines Ms and Mf rep rese nt the start and finish ofmarte nsitic tran sformati on.Classificati on of Heat Treati ng ProcessesIn some instan

8、ces, heat treatment procedures are clear-cut in terms of technique andapplication . whereas in other instances, descriptions or simple explanations are insufficient becausethe same technique frequently may be used to obtain different objectives. For example, stressrelievi ng and tempering are ofte n

9、 acco mp lished with the same equipment and by use of ide ntical timeand temp erature cycles. The objectives , however, are differe nt for the two pro cesses .The follow ing descri pti ons of the principal heat treati ng p rocesses are gen erally arra nged according to their interrelationships .Norm

10、alizing consists of heating a ferrous alloy to a suitable temperature (usually 50 F to 100F or 28 C to 56 C ) above its specific upper transformation temperature . This is followed by cooling in still air to at least some temperature well below its transformation temperature range. For low-carb on s

11、teels, the result ing structure and prop erties are the same as those achieved by full annealing; for most ferrous alloys, normalizing and annealing are not synonymous.Normaliz ing usually is used as a con diti oning treatme nt, no tably for refining the grains of steels that have been subjected to

12、high temperatures for forging or other hot working operations. The no rmaliz ing pro cess usually is succeeded by ano ther heat treat ing op erati on such as auste nitiz ing for harde ning, ann eali ng, or tempering.Ann eali ng is a gen eric term deno ti ng a heat treatme nt that con sists of heati

13、ng to and hold ing at a suitable temperature followed by cooling at a suitable rate. It is used primarily to soften metallic materials, but also to simulta neously p roduce desired cha nges in other prop erties or in microstructure.The purpose of such cha nges may be, but is not confined to, impro v

14、eme nt of mach in ability,mecha ni cal or electricalfacilitati on of cold work (known as in-pro cess ann eali ng), i mp roveme nt of prop erties, or to in crease dime nsional stability. Whe n app lied solely to relive stresses, it com monly is called stress-relief ann eali ng, synonym ous with stres

15、s relievi ng.When the term “ annealing”is applied to ferrous alloys without qualification, full annealing is applied. This is achieved by heating above the alloy s transformation temperature, then applying a cooling cycle which provides maximum softness. This cycle may vary widely, depending on comp

16、 ositi on and characteristics of the sp ecific alloy.Quenching is a rapid cooli ng of a steel or alloy from the auste nitiz ing temp erature by immers ing the work piece in a liquid or gaseous medium. Quenching medium com monly used in clude water, 5% brine, 5% caustic in an aqueous soluti on, oil,

17、poly mer soluti ons, or gas (usually air or n itroge n).Selecti on of a que nching medium depends largely on the harde nability of material and the mass of the material being treati ng (princip ally sect ion thick ness).The cooli ng cap abilities of the above-listed que nching media vary greatly. In

18、 selecti ng a quenching medium, it is best to avoid a solution that has more cooling power than is needed to achieve the results, thus mini miz ing the p ossibility of crack ing and warp of the parts being treated.Modifications of the term quenching include direct quenching, fog quenching, hot quenc

19、hing, in terr up ted que nching, selective que nching, spray que nching, and time que nching.Tempering. In heat treati ng of ferrous alloys, tempering con sists of reheat ing the auste nitized andque nch-harde ned steel or iron to some p reselected temp erature that is below the lower tran sformati

20、ontemperature (generally below 1300C or 705 C ). Tempering offers a means of obtaining variouscomb in ati ons of mecha ni cal prop erties. Tempering temp eratures used for harde ned steels are ofte n nohigher tha n 300 C (150 C). The term “ tempering ” should not be con fused with either pro cessann

21、 eali ng or stress relievi ng. Even though time and temp erature cycles for the three pro cesses may bethe same, the con diti ons of the materials being pro cessed and the objectives may be differe nt.Stress relievi ng. Like tempering, stress relievi ng is always done by heat ing to some temp eratur

22、ebelow the lower tran sformatio n temp erature for steels and irons. For non ferrous metals, thetemp erature may vary from slightly above room temp erature to several hun dred degrees, dependingon the alloy and the amount of stress relief that is desired.The primary purpose of stress relieving is to

23、 relieve stresses that have been imparted to thework piece from such p rocesses as forming, roll ing, mach ining or weldi ng. The usual p rocedure is toheat work piece to the p re-established temp erature long eno ugh to reduce the residual stresses (this is atime-and temperature-dependent operation

24、) to an acceptable level; this is followed by cooling at arelatively slow rate to avoid creati on of new stresses.The gen erally acce pted defi niti on for heat treat ing metals and metal alloys is“heati ng andcooli ng a solid metal or alloy in a way so as to obta in sp ecific con diti ons or prop e

25、rties. ”Heati ng forthe sole purpose of hot work ing (as in forging op erati ons) is excluded from this defi niti on.Likewise ,the types of heat treatment that are sometimes used for products such as glass or plastics are alsoexcluded from coverage by this definition .Tran sformatio n CurvesThe basi

26、s for heat treatment is the time-temperature-transformation curves or TTT curves where ,in a single diagram all the three parameters are plotted . Because of the shape of the curves, they arealso sometimes called C-curves or S-curves .To plot TTT curves, the particular steel is held at a given tempe

27、rature and the structure isexamined at predetermined intervals to record the amount of transformation taken place . It is knownthat the eutectoid steel (T80) under equilibrium conditions contains, all austenite above 723C,whereas below, it is p earlite .To form p earlite ,the carb on atoms should di

28、ffuse to form ceme ntite . Thediffusi on being a rate pro cess , would require sufficie nt time for compi ete tran sformati on of auste niteto pearlite . From different samples , it is possible to note the amount of the transformation taking placeat any temperature. These points are then plotted on

29、a graph with time and temperature as theaxes. Through these points, transformation curves can be plotted as shown in Fig.1 for eutectoid steel. The curve at extreme left represents the time required for the transformation of austenite to pearlite to start at any given temperature . Similarly , the c

30、urve at extreme right represents the time required for comp let ing the tran sformatio n . Betwee n the two curves are the points rep rese nti ng p artial transformation. The horizontal lines Ms and Mf represent the start and finish of martensitic tran sformatio n.Classificati on of Heat Treati ng P

31、rocessesIn some instances, heat treatment procedures are clear-cut in terms of technique and application . whereas in other instances, descriptions or simple explanations are insufficient because the same technique frequently may be used to obtain different objectives . For example, stress relievi n

32、g and tempering are ofte n acco mp lished with the same equipment and by use of ide ntical time and temp erature cycles. The objectives , however, are differe nt for the two pro cesses .The follow ing descri pti ons of the principal heat treati ng p rocesses are gen erally arra nged according to the

33、ir interrelationships .Normalizing consists of heating a ferrous alloy to a suitable temperature (usually 50 F to 100F or 28 C to 56 C ) above its specific upper transformation temperature . This is followed by cooling in still air to at least some temperature well below its transformation temperatu

34、re range. For low-carb on steels, the result ing structure and prop erties are the same as those achieved by full annealing; for most ferrous alloys, normalizing and annealing are not synonymous.Normaliz ing usually is used as a con diti oning treatme nt, no tably for refining the grains of steels t

35、hat have been subjected to high temperatures for forging or other hot working operations. The no rmaliz ing pro cess usually is succeeded by ano ther heat treat ing op erati on such as auste nitiz ing for harde ning, ann eali ng, or tempering.Ann eali ng is a gen eric term deno ti ng a heat treatme

36、nt that con sists of heati ng to and hold ing at a suitable temperature followed by cooling at a suitable rate. It is used primarily to soften metallic materials, but also to simulta neously p roduce desired cha nges in other prop erties or in microstructure.The purpose of such cha nges may be, but

37、is not confined to, impro veme nt of mach in ability,mecha ni cal or electricalfacilitati on of cold work (known as in-pro cess ann eali ng), i mp roveme nt of prop erties, or to in crease dime nsional stability. Whe n app lied solely to relive stresses, it com monly is called stress-relief ann eali

38、 ng, synonym ous with stress relievi ng.When the term “ annealing”is applied to ferrous alloys without qualification, full annealing is applied. This is achieved by heating above the alloy s transformation temperature, then applying acooling cycle which provides maximum softness. This cycle may vary

39、 widely, depending oncomp ositi on and characteristics of the sp ecific alloy.Quenching is a rapid cooli ng of a steel or alloy from the auste nitiz ing temp erature by immersi ngthe work piece in a liquid or gaseous medium. Quenching medium com mon ly used in clude water, 5%brine, 5% caustic in an

40、aqueous soluti on, oil, poly mer soluti ons, or gas (usually air or n itroge n).Selecti on of a que nching medium depends largely on the harde nability of material and the massof the material being treati ng (princip ally sect ion thick ness).The cooli ng cap abilities of the above-listed que nching

41、 media vary greatly. In select ing aquenching medium, it is best to avoid a solution that has more cooling power than is needed toachieve the results, thus mini miz ing the p ossibility of crack ing and warp of the parts being treated.Modifications of the term quenching include direct quenching, fog

42、 quenching, hot quenching,in terr up ted que nching, selective que nching, spray que nching, and time que nching.Tempering. In heat treati ng of ferrous alloys, tempering con sists of reheat ing the auste nitized andque nch-harde ned steel or iron to some p reselected temp erature that is below the

43、lower tran sformati ontemperature (generally below 1300 C or 705 C ). Tempering offers a means of obtaining variouscomb in ati ons of mecha ni cal prop erties. Tempering temp eratures used for harde ned steels are ofte n nohigher tha n 300 C (150 C). The term “ tempering ” should not be con fused wi

44、th either pro cessann eali ng or stress relievi ng. Even though time and temp erature cycles for the three pro cesses may bethe same, the con diti ons of the materials being pro cessed and the objectives may be differe nt.Stress relievi ng. Like tempering, stress relievi ng is always done by heat in

45、g to some temp eraturebelow the lower tran sformati on temp erature for steels and irons. For non ferrous metals, thetemp erature may vary from slightly above room temp erature to several hun dred degrees, dependingon the alloy and the amount of stress relief that is desired.The primary purpose of s

46、tress relieving is to relieve stresses that have been imparted to thework piece from such p rocesses as forming, roll ing, mach ining or weldi ng. The usual p rocedure is toheat work piece to the p re-established temp erature long eno ugh to reduce the residual stresses (this is atime-and temperatur

47、e-dependent operation) to an acceptable level; this is followed by cooling at arelatively slow rate to avoid creati on of new stresses.The gen erally acce pted defi niti on for heat treat ing metals and metal alloys is“heati ng andcooli ng a solid metal or alloy in a way so as to obta in sp ecific c

48、on diti ons or prop erties. ”Heati ng forthe sole purpose of hot work ing (as in forging op erati ons) is excluded from this defi niti on.Likewise ,the types of heat treatment that are sometimes used for products such as glass or plastics are also excluded from coverage by this definition .Tran sfor

49、matio n CurvesThe basis for heat treatment is the time-temperature-transformation curves or TTT curves where ,in a single diagram all the three parameters are plotted . Because of the shape of the curves, they are also sometimes called C-curves or S-curves .To plot TTT curves, the particular steel i

50、s held at a given temperature and the structure is examined at predetermined intervals to record the amount of transformation taken place . It is known that the eutectoid steel (T80) under equilibrium conditions contains, all austenite above 723C, whereas below, it is p earlite .To form p earlite ,t

51、he carb on atoms should diffuse to form ceme ntite . The diffusi on being a rate pro cess , would require sufficie nt time for compi ete tran sformati on of auste nite to pearlite . From different samples , it is possible to note the amount of the transformation taking place at any temperature. Thes

52、e points are then plotted on a graph with time and temperature as the axes. Through these points, transformation curves can be plotted as shown in Fig.1 for eutectoid steel. The curve at extreme left represents the time required for the transformation of austenite to pearlite to start at any given t

53、emperature . Similarly , the curve at extreme right represents the time required for completing the transformation . Between the two curves are the points representing partial transformation. The horizontal lines Ms and Mf represent the start and finish of martensitic tran sformatio n.Classificati o

54、n of Heat Treati ng ProcessesIn some instances, heat treatment procedures are clear-cut in terms of technique and application . whereas in other instances, descriptions or simple explanations are insufficient because the same technique frequently may be used to obtain different objectives . For exam

55、ple, stress relievi ng and tempering are ofte n acco mp lished with the same equipment and by use of ide ntical time and temp erature cycles. The objectives , however, are differe nt for the two pro cesses .The follow ing descri pti ons of the principal heat treati ng p rocesses are gen erally arra

56、nged according to their interrelationships .Normalizing consists of heating a ferrous alloy to a suitable temperature (usually 50 F to 100F or 28 C to 56 C ) above its specific upper transformation temperature . This is followed by cooling in still air to at least some temperature well below its tra

57、nsformation temperature range. For low-carb on steels, the result ing structure and prop erties are the same as those achieved by full annealing; for most ferrous alloys, normalizing and annealing are not synonymous.Normaliz ing usually is used as a con diti oning treatme nt, no tably for refining the grains of steels that have been subjected to high temperatures for forging or other hot working operations. The no rmaliz ing pro cess usually is succeeded by ano ther heat treat ing op erati on such as auste nitiz ing for harde ning, ann eali ng, or tempering.Ann eali ng is a gen eric term