金屬材料培訓(xùn)

1、HEAT TREATMENT ANDMETALLURGICAL TRAININGSection Title Page No 1 金屬學(xué)原理金屬學(xué)原理 3 2 鐵碳平衡相圖鐵碳平衡相圖 12 3 鋼的分類鋼的分類 19 4 熱處理原理及過(guò)程熱處理原理及過(guò)程 37 5 表面熱處理表面熱處理 69 6 硬度測(cè)試硬度測(cè)試 84 TABLE OF CONTENTS一一. . 金金 屬屬 學(xué)學(xué) 基基 礎(chǔ)礎(chǔ) 知知 識(shí)識(shí) 材料工程學(xué)是以晶體學(xué)為基礎(chǔ)地一門材料工程學(xué)是以晶體學(xué)為基礎(chǔ)地一門應(yīng)用科學(xué)應(yīng)用科學(xué). .晶體學(xué)主要介紹金屬微觀結(jié)構(gòu)晶體學(xué)主要介紹金屬微觀結(jié)構(gòu)的知識(shí)的知識(shí). . 晶體結(jié)構(gòu)晶體結(jié)構(gòu) 金屬分晶體和非

2、晶體: 微觀結(jié)構(gòu)上的主要區(qū)別:晶體:原子作有序有規(guī)則的 排列 非晶體:原子呈無(wú)序無(wú)規(guī)則 排列. 宏觀上的差異晶體:固定的熔點(diǎn) 非晶體:熔點(diǎn)不固定。單晶體多晶體晶粒晶界晶 格晶 胞 晶格上的點(diǎn)叫晶格結(jié)點(diǎn)。結(jié)點(diǎn)代表原子在晶體中的平衡位置原子在平衡位置左右移動(dòng)。體體 心心 立立 方方 晶晶 格格 -Fe 、Cr、V、Mo等屬于此晶格類型。 面面 心心 立立 方方 晶晶 格格 -Fe AlCuAu及Ag等屬于此晶格類型。 在實(shí)際使用的金屬材料中由于有其他種類的外來(lái)原子以及金屬材料在冶煉后的凝固過(guò)程中受到各種因素的影響使得在原子排布過(guò)程中出現(xiàn)了不規(guī)則的現(xiàn)象這種原子排布不規(guī)則的現(xiàn)象稱為晶體缺陷。 金金 屬

3、屬 晶晶 體體 缺缺 陷陷間隙原子空位面 缺 陷線缺陷點(diǎn)缺陷 某些金屬在固態(tài)下具有兩種以上的晶格形式這種現(xiàn)象叫做同素異構(gòu)轉(zhuǎn)變。其本質(zhì)是金屬隨溫度的改變由一種晶格轉(zhuǎn)變到另一種晶格。以鐵為例液態(tài)純鐵在15381538 C C時(shí)進(jìn)行結(jié)晶得到某種晶格的FeFe 繼續(xù)冷卻到13941394 C C時(shí)發(fā)生同素異構(gòu)轉(zhuǎn)變FeFe轉(zhuǎn)變?yōu)榱硪环N結(jié)構(gòu)的FeFe再冷卻到912912 C C時(shí)發(fā)生同素異構(gòu)轉(zhuǎn)變轉(zhuǎn)變?yōu)镕eFe。由于同素異構(gòu)轉(zhuǎn)變與液態(tài)金屬的結(jié)晶過(guò)程有很多相似之處有一定的轉(zhuǎn)變溫度轉(zhuǎn)變時(shí)過(guò)冷(或過(guò)熱)放出和吸收潛熱。同同 素素 異異 構(gòu)構(gòu) 轉(zhuǎn)轉(zhuǎn) 變變 IRON CARBON EQUILIBRIUM DIAGRA

4、M 二二. .鐵鐵 碳碳 平平 衡衡 相相 圖圖鐵鐵素素體體 Ferrite 碳溶于Fe中的間隙固溶體，稱為鐵素體。用符號(hào)“F”表示。鐵素體的組織與性能與純鐵相似 即具有良好的塑性和韌性,強(qiáng)度與硬度較低。奧氏奧氏體體 Austenite 碳溶于 FeFe中的間隙固溶體，稱為奧氏體。用符號(hào)“A A”表示。奧氏體是鐵碳合金的高溫組織，在平衡條件下，它最低存在溫度是727。在該溫度下奧氏體的成份是一固定值:含碳0.77%。滲滲碳碳體體 Cementite 滲碳體是鐵和碳形成的間隙化合物。用符號(hào)“Fe3C”表示。它的含碳量為6.69%，是一個(gè)固定值。滲碳體具有復(fù)雜的晶體結(jié)構(gòu)，很硬、很脆、幾乎沒(méi)有塑性，

5、它是鐵碳合金中的強(qiáng)化相。滲碳體的形態(tài)、大小、多少及分布對(duì)鐵碳合金的性能有直接影響。 通過(guò)不同的熱處理方法改變滲碳體的形態(tài)、大小、多少及分布，從而改變材料的性能,正是熱處理的重要原理之一 。珠光珠光體體 Pearlite珠光體是鐵素體和滲碳體的機(jī)械混合物,用符號(hào)“P”表示。粒狀珠光體片狀珠光體 馬氏體是碳在Fe中的過(guò)飽和固溶體,以符號(hào)M表示。過(guò)冷奧氏體快速冷卻至Ms點(diǎn)以下則開(kāi)始發(fā)生馬氏體轉(zhuǎn)變直至Mf點(diǎn)轉(zhuǎn)變結(jié)束.馬馬氏氏體體 Martensite 馬氏體的硬度主要取決于馬氏體中的含碳量隨著含碳量的增加馬氏體的硬度也增加。馬氏體的塑性和韌性也和含碳量有關(guān)含碳量越高馬氏體晶格畸變?cè)酱蟠慊饝?yīng)力也較大會(huì)產(chǎn)

6、生許多顯微裂紋韌性會(huì)降低。所以淬火鋼一般不宜直接使用必須進(jìn)行回火來(lái)消除應(yīng)力穩(wěn)定尺寸獲得良好的綜合性能。STEEL CATEGORIZATION三三. 鋼的分類鋼的分類AISI - stands for American Iron and Steel Institute, who originally developed the current method of steel characterization and identification.（美國(guó)鋼鐵學(xué)會(huì)）SAE - stands for the Society for Automotive Engineers, who have als

7、o determined a method of steel characterization and identification.(汽車工程師學(xué)會(huì)ASTM - stands for American Society for Testing and Materials. （美國(guó)材料試驗(yàn)協(xié)會(huì)）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”表示鉛的加入，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. 在符號(hào)的最后標(biāo)“H”，為高淬透性鋼，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優(yōu)質(zhì)碳素結(jié)構(gòu)鋼 采用阿拉伯?dāng)?shù)字表示，阿拉伯?dāng)?shù)字表示平均含碳量的萬(wàn)分之幾。 例如：含碳0.20%的優(yōu)質(zhì)碳素結(jié)構(gòu)鋼表示為20，后面再加A表示高級(jí)優(yōu)質(zhì)。碳素工具鋼 用T加阿拉伯?dāng)?shù)字的

13、辦法表示，T表示碳素工具鋼，數(shù)字表示含碳量的千分之幾。如T9表示含碳0.9%的碳素工具鋼。易切削鋼 用Y加阿拉伯?dāng)?shù)字的辦法表示，Y表示易切削鋼，數(shù)字表示含碳量的萬(wàn)分之幾。如Y40Mn表示含碳0.4%，含錳1.21.55的易切鋼。合金鋼：用化學(xué)元素符號(hào)和阿拉伯?dāng)?shù)字表示 1、含碳量， 一般再牌號(hào)頭部用阿拉伯?dāng)?shù)字表示。低合金鋼、合金結(jié)構(gòu)鋼、合金彈簧鋼等，用兩位數(shù)字表示含碳量（萬(wàn)分之幾）。不銹鋼、耐熱鋼等一般用一位數(shù)字表示平均含碳量（千分之幾）；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。合金工具鋼，高速工具鋼等，一般不標(biāo)出含碳數(shù)字，若含碳量小于1，可用一位數(shù)字表示（千分之

14、幾）。 2、合金元素，平均合金含量小于1.5時(shí)，鋼號(hào)中僅標(biāo)明元素而不標(biāo)含量；合金含量為1.502.49時(shí)標(biāo)2，2.503.49時(shí)標(biāo)3，依此類推。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 （錳）- 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（鉻） - increases resistance to corrosion, increases hardenability.Nickel（鎳） - lowers the critical cooling rate, increases to

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

17、ncreases hardenability, higher tempering temperatures, high temperature propertiesTungsten（鎢） - 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. 熱處理工藝熱處理工藝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 處處 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.淬火冷卻速度對(duì)組織的影響8407淬火快冷淬火快冷HRC 46沖擊強(qiáng)度 290 J

24、oule8407淬火慢冷淬火慢冷HRC 46沖擊強(qiáng)度沖擊強(qiáng)度60 Joule淬火冷卻速度對(duì)H13沖擊強(qiáng)度的影響 試驗(yàn)溫度試驗(yàn)溫度Produce a defined microstructure (Spheroidizing)得到理想的顯微組織（如球化）Produce a homogeneous microstructure 組織均勻化Refine the crystal structure 細(xì)化晶粒Produce a soft condition 使材料變軟Manipulate the electrical, magnetic or mechanical properties 改變電、磁或機(jī)械

25、性能Stress relieving 去應(yīng)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. 正火將使由于軋制、鍛造、冷拉等工序產(chǎn)生的晶粒變形得到恢復(fù)。The difference between full annealing and normalizin

26、g is that the cooling rate of normalizing is faster than that of the annealing process. 正火和完全退火的區(qū)別在于正火的冷卻速度要快。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. 通常會(huì)由于不同的冷速而得到不同的顯微組織Normalizing

27、is also used as a refining process on castings that have non uniform cross sections or non-homogenous structures. 正火也常用于使鑄態(tài)組織均勻化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. 去應(yīng)力退火是制造過(guò)程中間的熱處理工藝，目的使為了消除機(jī)械加工所產(chǎn)生的殘余應(yīng)力。Generally it is carried out at a temperature of 800F up to 1200F. 通常在華氏800到1200度之間進(jìn)行。Stress Relieving is carried out below the Lower Critical Line, therefore there are no phase changes to be considered. 沒(méi)有相變發(fā)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. 升到特定溫度并保持一定時(shí)間，使材料性能發(fā)生轉(zhuǎn)變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. 鋼加熱到高溫后就轉(zhuǎn)變成奧氏體組織，保溫階段是使組織的再定位和成分的擴(kuò)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”. 完成均勻化后就快速冷卻得到馬氏體組織This is the hardest structure that can be obtained when steel is cooled rapidly from the appropriate temperature. The cooling is called “quenching”. 馬氏體是所有組織中硬度最高的，冷卻過(guò)程叫淬火Sufficient carbon in the steel 有足夠的含碳量A suitable austenitizing temperature (dependent on carbon content

32、of steel). 1500-1600F for through hardening, 1600-1800F for carburizing. 適當(dāng)?shù)膴W氏體化溫度（取決于鋼的含碳量）Sufficient time at the temperature to ensure temperature uniformity throughout the steel. 足夠的保溫時(shí)間使工件內(nèi)部溫度均勻化Rapid cool down at an appropriate rate (quenching).適當(dāng)?shù)目焖倮鋮s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. 如果所有的工藝參數(shù)滿足要求，所得到的馬氏體將很硬、很脆You can test the steel by a simple hardness check using a Rockwell tester. 可以用簡(jiǎn)單的洛氏硬度計(jì)來(lái)測(cè)鋼的硬度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. 馬氏體氏鋼的最不穩(wěn)定的組織，表現(xiàn)為高脆性、低的沖擊韌性和高抗拉強(qiáng)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、使馬氏體穩(wěn)定：使條狀馬氏體消除應(yīng)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. 對(duì)已經(jīng)淬火的零件在較低溫度下保溫。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、消除應(yīng)力、提高韌性和塑性。Tempering is a critical step in the heat treat process and parts will not function properly if tempered incorrectly. 回火溫度很重要，不適當(dāng)?shù)幕鼗鹂赡苁沽慵Аhe hardness of the part drops during the first hour, then stabilizes over the next several hours. 回火開(kāi)始階段硬度先降低，隨后使各種性能穩(wěn)定下來(lái)

37、。If tempering is done soon after hardening for the proper time and at proper temperature, parts will havelUniform tempered hardness. 均勻的回火硬度lNo cracks (visible or microscopic) in the high carbon surface layer. 避免開(kāi)裂（無(wú)論宏觀或微觀）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. 尺寸變化：膨脹或收縮Shape distortion is seen in twisting or flatness or bending. 形狀變化：扭曲、彎曲等Distortion occurs at heat-treatment because of two reasons:Heat is applied to the part. 加熱因素The part is cooled down rapidly (quenching).快速冷

39、卻的因素DISTORTION變變 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. 在加熱過(guò)程中，前道工序所積攢的應(yīng)力將得到釋放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.淬火過(guò)程中如果沒(méi)有夾具將其保持，淬火應(yīng)力將使工件變形No. However steps can be taken to minimize the risk of distortion, such as: 不能避免變形但能減小變形程度 Correct normalizing temperature selection選擇合適的正火溫度，為淬火作組織準(zhǔn)備 Stress relieving 去應(yīng)力退火 Stabili

41、zing 穩(wěn)定化處理 Tempering 回火lFixturing/clamping 專用夾具Steel composition 鋼的成分Residual stresses 殘余應(yīng)力Heating rate 加熱速度Austenitizing temperature 奧氏體化溫度Time at austenitizing temperature 保溫時(shí)間Cooling rates in quenching and tempering 回火和淬火時(shí)的冷卻速度Hardness Testing五五. 硬硬 度度 測(cè)測(cè) 試試Hardness of steel is relative to the he

42、at treatment that has been applied to it. 鋼鐵的硬度和熱處理有關(guān)Hardness can be stated as “resistance to permanent deformation”. 硬度的定義：材料抵抗永久變形的能力洛 氏 硬 度洛氏硬度試驗(yàn)應(yīng)用的最為廣泛它是測(cè)量壓痕的深度以深度的大小來(lái)表示材料的硬度值。為了能用同一硬度計(jì)測(cè)量從極軟到極硬材料的硬度采用不同的壓頭和載荷組成了15種不同的硬度標(biāo)尺。常用的有HRA 硬質(zhì)合金表面淬火鋼等HRB 銅合金退火鋼鋁合金等HRC 淬火鋼鈦合金等. 采用鋼球壓頭加載后壓入拭樣表面用單位壓痕表面積所受的載荷大

43、小來(lái)確定布氏硬度值。 HB=P/F P-壓痕的面積 F-載荷 布氏硬度硬度通常用于測(cè)定鑄鐵,結(jié)構(gòu)鋼調(diào)質(zhì)件的硬度。布布 氏氏 硬硬 度度( (HB)HB) 維氏硬度的測(cè)試原理與布氏硬度相同單位壓痕表面積上所承受的載荷。但所采用的壓頭不同維氏硬度采用的是錐面夾角為136度的金剛石四方角錐體。 特點(diǎn):載荷可任意選取材質(zhì)不論軟硬 數(shù)據(jù)穩(wěn)定精度高。 常用于檢驗(yàn)表面淬火硬化層深度化學(xué)熱處理件表面硬度及薄件硬度等。維維 氏氏 硬硬 度度 (HV)VickerslInduction hardening 感應(yīng)淬火感應(yīng)淬火lFlame heating Flame heating 火焰加熱熱處理火焰加熱熱處理lLaser hardening 激光加熱熱處理激光加熱熱處理lChemical heat trea