金属材料的培训

1、HEAT TREATMENT ANDMETALLURGICAL TRAININGSection Title Page No 1 金属学原理金属学原理 3 2 铁碳平衡相图铁碳平衡相图 12 3 钢的分类钢的分类 19 4 热处理原理及过程热处理原理及过程 37 5 表面热处理表面热处理 69 6 硬度测试硬度测试 84 TABLE OF CONTENTS一一. . 金金 属属 学学 基基 础础 知知 识识 材料工程学是以晶体学为基础地一门材料工程学是以晶体学为基础地一门应用科学应用科学. .晶体学主要介绍金属微观结构晶体学主要介绍金属微观结构的知识的知识. . 晶体结构晶体结构 金属分晶体和非

2、晶体: 微观结构上的主要区别:晶体:原子作有序有规则的 排列 非晶体:原子呈无序无规则 排列. 宏观上的差异晶体:固定的熔点 非晶体:熔点不固定。单晶体多晶体晶粒晶界晶 格晶 胞 晶格上的点叫晶格结点。结点代表原子在晶体中的平衡位置原子在平衡位置左右移动。体体 心心 立立 方方 晶晶 格格 -Fe 、Cr、V、Mo等属于此晶格类型。 面面 心心 立立 方方 晶晶 格格 -Fe AlCuAu及Ag等属于此晶格类型。 在实际使用的金属材料中由于有其他种类的外來原子以及金属材料在冶炼后的凝固过程中受到各种因素的影响使得在原子排布过程中出现了不规则的现象这种原子排布不规则的现象称为晶体缺陷。 金金 属

3、属 晶晶 体体 缺缺 陷陷间隙原子空位面 缺 陷线缺陷点缺陷 某些金属在固态下具有两种以上的晶格形式这种现象叫做同素异构转变。其本质是金属随温度的改变由一种晶格转变到另一种晶格。以铁为例液态纯铁在15381538 C C時进行结晶得到某种晶格的FeFe 继续冷却到13941394 C C时发生同素异构转变FeFe转变为另一种结构的FeFe再冷卻到912912 C C时发生同素异构转变转变为FeFe。由于同素异构转变与液态金属的结晶过程有很多相似之处有一定的转变温度转变时过冷(或过热)放出和吸收潜热。同同 素素 异异 构构 转转 变变 IRON CARBON EQUILIBRIUM DIAGRA

4、M 二二. .铁铁 碳碳 平平 衡衡 相相 图图铁铁素素体体 Ferrite 碳溶于Fe中的间隙固溶体，称为铁素体。用符号“F”表示。铁素体的组织与性能与纯铁相似 即具有良好的塑性和韧性,强度与硬度较低。奧氏奧氏体体 Austenite 碳溶于 FeFe中的间隙固溶体，称为奧氏体。用符号“A A”表示。奧氏体是铁碳合金的高温组织，在平衡条件下，它最低存在温度是727。在该温度下奧氏体的成份是一固定值:含碳0.77%。渗渗碳碳体体 Cementite 渗碳体是铁和碳形成的间隙化合物。用符号“Fe3C”表示。它的含碳量为6.69%，是一個固定值。渗碳体具有复杂的晶体结构，很硬、很脆、几乎没有塑性，

5、它是铁碳合金中的强化相。渗碳体的形态、大小、多少及分布对铁碳合金的性能有直接影响。 通过不同的热处理方法改变渗碳体的形态、大小、多少及分布，从而改变材料的性能,正是热处理的重要原理之一 。珠光珠光体体 Pearlite珠光体是铁素体和渗碳体的机械混合物,用符号“P”表示。粒状珠光体片状珠光体 马氏体是碳在Fe中的过饱和固溶体,以符号M表示。过冷奧氏体快速冷卻至Ms点以下则开始发生马氏体转变直至Mf点转变结束.马马氏氏体体 Martensite 马氏体的硬度主要取决于马氏体中的含碳量随着含碳量的增加马氏体的硬度也增加。马氏体的塑性和韧性也和含碳量有关含碳量越高马氏体晶格畸变越大淬火应力也較大会产

6、生许多显微裂纹韧性会降低。所以淬火钢一般不宜直接使用必须进行回火来消除应力稳定尺寸获得良好的综合性能。STEEL CATEGORIZATION三三. 钢的分类钢的分类AISI - stands for American Iron and Steel Institute, who originally developed the current method of steel characterization and identification.（美国钢铁学会）SAE - stands for the Society for Automotive Engineers, who have als

7、o determined a method of steel characterization and identification.(汽车工程师学会ASTM - stands for American Society for Testing and Materials. （美国材料试验协会）ISO, EN, DIN, JIS are international, European, German & Japanese standards.AISI and SAE steels dont always have a 4 digit numerical system of identif

8、ication.The letter “L” between the second and third numerals means that Lead has been added (usually .15 - .35%) for improved machinability. “L”表示铅的加入，以提高切削性能。The letter “B” shown between the second and third numerals means that the steel contains 0.0005 to 0.003% Boron, indicating high hardenabilit

9、y. “B” 表示加入0.00050.003的硼，指高的淬透性。The letter “H” at the end mean that standard grades meet certain hardenability limits. 在符号的最后标“H”，为高淬透性钢，指材料具有特定的淬透性。Both are generally designated by a 4-digit number (e.g., 1020). First two digits represent alloy type.Last two digits represent percent of carbon (e.g.

10、, 20 = .20% not 20%)First two digits are always 10 for plain carbon steels (e.g. 1045) and anything but 10 for alloy steels (e.g. 4140, 8620).Plain Carbon and Low Alloy Steels are named by the use of a 4 Digit numbering system called the AISI or SAE Steel Designation.First 2 numbers identify the typ

11、e of alloy steelLast 2 numbers identify the carbon content of the steel1020, 8617, 8620, 4320 - low carbon steel10L50, 1045, 4340 - medium carbon steel1074, 1095, 52100 - high carbon steelThe 1st letter is descriptive of type of tool steel or its applicationA - air hardening steelsD - high carbon, h

12、igh chromium steelsH - hot work steelsM - molybdenum high-speed steelsO - oil hardening cold work steelsP - low carbon mold steelsS - shock resistant steelsT - tungsten high-speed steelsW - water hardening steels优质碳素结构钢 采用阿拉伯数字表示，阿拉伯数字表示平均含碳量的万分之几。 例如：含碳0.20%的优质碳素结构钢表示为20，后面再加A表示高级优质。碳素工具钢 用T加阿拉伯数字的

13、办法表示，T表示碳素工具钢，数字表示含碳量的千分之几。如T9表示含碳0.9%的碳素工具钢。易切削钢 用Y加阿拉伯数字的办法表示，Y表示易切削钢，数字表示含碳量的万分之几。如Y40Mn表示含碳0.4%，含锰1.21.55的易切钢。合金钢：用化学元素符号和阿拉伯数字表示 1、含碳量， 一般再牌号头部用阿拉伯数字表示。低合金钢、合金结构钢、合金弹簧钢等，用两位数字表示含碳量（万分之几）。不锈钢、耐热钢等一般用一位数字表示平均含碳量（千分之几）；含碳量小于0.1%者，用0表示；含碳量不大于 0.03%者，用00表示。合金工具钢，高速工具钢等，一般不标出含碳数字，若含碳量小于1，可用一位数字表示（千分之

14、几）。 2、合金元素，平均合金含量小于1.5时，钢号中仅标明元素而不标含量；合金含量为1.502.49时标2，2.503.49时标3，依此类推。ALLOYING ELEMENTS合合 金金 元元 素素Carbon（碳） - most important alloying element. It is THE element that determines the mechanical properties of steel in various heat-treat conditions. Manganese （锰）- present in all commercial steels. add

15、ed to form manganese sulfide stringers. Mn affects the hardness and hardenability to a lesser extent than C.Silicon（硅） - Mainly used as a deoxidizer for steel processingChromium（铬） - increases resistance to corrosion, increases hardenability.Nickel（镍） - lowers the critical cooling rate, increases to

16、ughness and fatigue resistance.Vanadium （钒）- strong carbide former, increases hardenability.Lead（铅） - improves machining characteristics, at elevated temperatures can cause liquid metal embrittlement.Cobalt（钴） - wear resistance and hardness, especially at high operating temperaturesMolybdenum（钼） - i

17、ncreases hardenability, higher tempering temperatures, high temperature propertiesTungsten（钨） - increases hardness, decreases grain size, excellent for resisting heat. Can form tungsten carbide, used in high-speed tool steelsBoron（硼） - improves hardenabilityNitrogen（氮） - increases strength and hardn

18、ess, decreases ductility and toughness. HEAT TREAT PROCESSES四四. 热处理工艺热处理工艺Heat treatment is a method of preparing a metal (by changing its phase crystal orientation) to make the material harder or softer.Heat treatment is also done to relieve metal of induced stresses at certain stages of the parts

19、manufacturing.Heat treatment means to apply heat at temperatures above or below that of room temperature.深深 冷冷 处处 理理When a solid metal is heated up, a number of things begin to happen to it.Any induced stress will begin to manifest itself. In other words, depending on how the metal has been cut and/

20、or shaped, the stresses will begin to show in the form of movement. This is known as shape distortion.lPhase changelGrowth due to phase changelGrain growth (grain size is dependent on time & temperature)lSolutionizing of alloying elements into a solid solution.lPrecipitation of alloying elements

21、.lOxidation in some cases.lDecarburization in some cases.lDimensional instability after heat-treatment if mixed phases occur.When the metal is made, there are slight variations in the analysis. No two melts (composition) of metal are exactly alike.When metal is rolled or forged (ferrous and non ferr

22、ous) there is a grain deformation.Metals are dimensionally stable until they are heated to elevated temperatures and either phase changes occur or the stresses are relieved. When metal is cold worked, there are induced stresses.The Ms point (martensite start temperature) is a point on a cooling curv

23、e where the martensite begins to form down to temperatures well below the freezing point of water.What does the term “Cooling Rate” mean?The term cooling rate means the rate of heat transfer from the part being quenched to the medium it is being quenched into.淬火冷却速度对组织的影响8407淬火快冷淬火快冷HRC 46冲击强度 290 J

24、oule8407淬火慢冷淬火慢冷HRC 46冲击强度冲击强度60 Joule淬火冷却速度对H13冲击强度的影响 试验温度试验温度Produce a defined microstructure (Spheroidizing)得到理想的显微组织（如球化）Produce a homogeneous microstructure 组织均匀化Refine the crystal structure 细化晶粒Produce a soft condition 使材料变软Manipulate the electrical, magnetic or mechanical properties 改变电、磁或机械

25、性能Stress relieving 去应力ANNEALING PROCESSESNormalizing is a process that will restore grain deformation from distortion caused by rolling, forging, extrusion or drawing and reduce any stress created from those processes. 正火将使由于轧制、锻造、冷拉等工序产生的晶粒变形得到恢复。The difference between full annealing and normalizin

26、g is that the cooling rate of normalizing is faster than that of the annealing process. 正火和完全退火的区别在于正火的冷却速度要快。The resulting microstructure usually varies from Ferrite/Pearlite to Pearlite to Pearlite and Bainite, depending on how slow or how fast the steel is cooled. 通常会由于不同的冷速而得到不同的显微组织Normalizing

27、is also used as a refining process on castings that have non uniform cross sections or non-homogenous structures. 正火也常用于使铸态组织均匀化Stress Relieving is an intermediate heat-treatment procedure that is introduced during the manufacturing process to reduce and hopefully eliminate residual machining stress

28、es due to excessive machining practices. 去应力退火是制造过程中间的热处理工艺，目的使为了消除机械加工所产生的残余应力。Generally it is carried out at a temperature of 800F up to 1200F. 通常在华氏800到1200度之间进行。Stress Relieving is carried out below the Lower Critical Line, therefore there are no phase changes to be considered. 没有相变发生。Suggested

29、production flow path to include stress relieving for H.13 hot work die steelHARDENING硬化硬化Raising material to a particular temperature and holding it there for a specific time to change its properties. 升到特定温度并保持一定时间，使材料性能发生转变We austenitize (heat) steel to a high temperature (1500F) to change its stru

30、cture to austenite and allow the steel to soak at temperature to allow diffusion and reorientation of the structure. 钢加热到高温后就转变成奥氏体组织，保温阶段是使组织的再定位和成分的扩散Once we are satisfied that equalization is complete, the steel is then cooled rapidly to change the microstructure to a new structure called “Marten

31、site”. 完成均匀化后就快速冷却得到马氏体组织This is the hardest structure that can be obtained when steel is cooled rapidly from the appropriate temperature. The cooling is called “quenching”. 马氏体是所有组织中硬度最高的，冷却过程叫淬火Sufficient carbon in the steel 有足够的含碳量A suitable austenitizing temperature (dependent on carbon content

32、of steel). 1500-1600F for through hardening, 1600-1800F for carburizing. 适当的奥氏体化温度（取决于钢的含碳量）Sufficient time at the temperature to ensure temperature uniformity throughout the steel. 足够的保温时间使工件内部温度均匀化Rapid cool down at an appropriate rate (quenching).适当的快速冷却速度If all of the process parameters have bee

33、n met, then martensite will exhibit itself as being extremely hard and very brittle. 如果所有的工艺参数满足要求，所得到的马氏体将很硬、很脆You can test the steel by a simple hardness check using a Rockwell tester. 可以用简单的洛氏硬度计来测钢的硬度No, martensite is perhaps the most unstable condition that the steel can be in. The instability

34、exhibits itself in terms of mechanical properties - extremely brittle, low impact value, high tensile strength. 马氏体氏钢的最不稳定的组织，表现为高脆性、低的冲击韧性和高抗拉强度Martensite can be stabilized by reheating (tempering) the steel to a suitable temperature to relieve the inherent stress on the needles of martensite. 回火可以

35、使马氏体稳定：使条状马氏体消除应力 TEMPERING回回 火火Treating previously hardened (e.g., carburized, carbo-nitrided or through hardened) material at a lower temperature; generally in the range of 300F to 1200F. 对已经淬火的零件在较低温度下保温。Tempering is done to lower the surface hardness to relieve stress and increase the toughness

36、and ductility.回火目的使降低表面硬度、消除应力、提高韧性和塑性。Tempering is a critical step in the heat treat process and parts will not function properly if tempered incorrectly. 回火温度很重要，不适当的回火可能使零件失效。The hardness of the part drops during the first hour, then stabilizes over the next several hours. 回火开始阶段硬度先降低，随后使各种性能稳定下来

37、。If tempering is done soon after hardening for the proper time and at proper temperature, parts will havelUniform tempered hardness. 均匀的回火硬度lNo cracks (visible or microscopic) in the high carbon surface layer. 避免开裂（无论宏观或微观）The subject of distortion can be divided into two categories which are:Size d

38、istortion is seen in a variation in part size. This means growth or shrinkage. 尺寸变化：膨胀或收缩Shape distortion is seen in twisting or flatness or bending. 形状变化：扭曲、弯曲等Distortion occurs at heat-treatment because of two reasons:Heat is applied to the part. 加热因素The part is cooled down rapidly (quenching).快速冷

39、却的因素DISTORTION变变 形形Any pre-induced stresses, such as those from forging, machining or omission of stress relieving operations, will manifest themselves on heating up to carburizing temperature. 在加热过程中，前道工序所积攒的应力将得到释放When steel is cooled rapidly, such as in quenching, quench stresses may be induced i

40、f the part is not fixtured in the appropriate way to withstand the distortion from quenching.淬火过程中如果没有夹具将其保持，淬火应力将使工件变形No. However steps can be taken to minimize the risk of distortion, such as: 不能避免变形但能减小变形程度 Correct normalizing temperature selection选择合适的正火温度，为淬火作组织准备 Stress relieving 去应力退火 Stabili

41、zing 稳定化处理 Tempering 回火lFixturing/clamping 专用夹具Steel composition 钢的成分Residual stresses 残余应力Heating rate 加热速度Austenitizing temperature 奥氏体化温度Time at austenitizing temperature 保温时间Cooling rates in quenching and tempering 回火和淬火时的冷却速度Hardness Testing五五. 硬硬 度度 测测 试试Hardness of steel is relative to the he

42、at treatment that has been applied to it. 钢铁的硬度和热处理有关Hardness can be stated as “resistance to permanent deformation”. 硬度的定义：材料抵抗永久变形的能力洛 氏 硬 度洛氏硬度试验应用的最为广泛它是测量压痕的深度以深度的大小來表示材料的硬度值。为了能用同一硬度计测量从极软到极硬材料的硬度采用不同的压头和载荷组成了15种不同的硬度标尺。常用的有HRA 硬质合金表面淬火钢等HRB 铜合金退火钢铝合金等HRC 淬火钢钛合金等. 采用钢球压头加载后压入拭样表面用单位压痕表面积所受的载荷大

43、小来确定布氏硬度值。 HB=P/F P-压痕的面积 F-载荷 布氏硬度硬度通常用于测定铸铁,结构钢调质件的硬度。布布 氏氏 硬硬 度度( (HB)HB) 维氏硬度的测试原理與布氏硬度相同单位压痕表面积上所承受的载荷。但所采用的压头不同维氏硬度采用的是锥面夹角為136度的金刚石四方角锥体。 特点:载荷可任意选取材质不论软硬 数据稳定精度高。 常用于检验表面淬火硬化层深度化学热处理件表面硬度及薄件硬度等。维维 氏氏 硬硬 度度 (HV)VickerslInduction hardening 感应淬火感应淬火lFlame heating Flame heating 火焰加热热处理火焰加热热处理lLaser hardening 激光加热热处理激光加热热处理lChemical heat trea