工程材料學（Chapter 3 Alloying of steels）-1

1、1Chapter 3 Alloying of steelsSchool of Manufacturing Science and Engineeringv0. Introductionv1. Alloying elements in steelv2. Role of alloying elements on steelv3. Strengthening mechanisms of steelv4. Approach to improve the Plasticity and toughnessv5. Effects of alloying elements on phase transform

2、ation of steelv6. Metallurgical quality of steelContentsSchool of Manufacturing Science and Engineering30 IntroductionuAlloying：add the appropriate elements to change the propertiesu Why alloying？ucarbon steel：產量大、價格便宜、加工容易產量大、價格便宜、加工容易淬透性淬透性J、回火穩(wěn)定性差、回火穩(wěn)定性差uCast iron：石墨嚴重破壞鑄鐵基體力學性能石墨嚴重破壞鑄鐵基體力學性能Scho

3、ol of Manufacturing Science and Engineering40 IntroductionuMain elements ：Cr、Ni、Mo、W、V Existed elements：Mn、Si uNote: the alloying elements to affect the phase change process to improve the performancelow alloy steel： 5%medium alloy steel： 510%high alloy steel： 10%School of Manufacturing Science and

4、Engineering51. Alloying elements in steel1.1 Distribution of Alloying elements in steel：B、C、N；：Al、Si：Ti、V、Cr、Mn、Co、Ni、Cu、：Zr、Nb、Mo：W：稀土元素、：稀土元素、TaS、PImpurity elements School of Manufacturing Science and Engineering61. Alloying elements in steel1.1 Distribution of Alloying elements in steelExisting f

5、orm of Alloying elements *： Solution in the F, A, or Msolid solution（固溶體）（固溶體） The formation of the strengthening phase; (carbides or intermetallic compounds) - strengthening phase（強化相）（強化相） The formation of nonmetallic inclusions; (oxides, nitrides, or sulfides, etc.) - the second phase（第二相）（第二相） E

6、xist in the free state. simple substance（單質）（單質）Depending on the types, characteristics, content, smelting and heat treatment processSchool of Manufacturing Science and Engineering71. Alloying elements in steel1.2 Classification of alloying elements (1) Interaction between alloying elements and iron

7、vA（austenite）formed elements：C、N、Mn、Cu、Ni、Co，(Priority distribution on A)Austenitic ability =Ni%+30C%+30N%+0.5Mn%+0.25Cu% vF（ferrite）：）：Cr、V、Si、Al、Ti、Mo、W，(Priority distribution on F)School of Manufacturing Science and Engineering81. Alloying elements in steel1.2 Classification of alloying elements

8、(2) Interaction between alloying elements and carbonvNon-carbide forming elements ：Al、Si、Cu、Ni、P，(Solid solution or impurity)vCarbide forming elements ：Cr、V、Ti、Mo、 Zr、Nb，(Carbide or solid solution)School of Manufacturing Science and Engineering91. Alloying elements in steel1.2 Classification of allo

9、ying elements (3) Austenitic stacking fault energy（奧氏體層（奧氏體層錯能）錯能） 1）Improving：Cu、Ni、C； 2）Weakening： Mn、 Cr、Ru(釕釕)、Ir(銥銥) 。層錯是一種晶體缺陷，它破壞了晶體排列的周期性，引起能量升高。產生單層錯是一種晶體缺陷，它破壞了晶體排列的周期性，引起能量升高。產生單位面積的層錯所需能量為位面積的層錯所需能量為“層錯能層錯能” 。（。（層錯能愈小，出現(xiàn)層錯的幾率層錯能愈小，出現(xiàn)層錯的幾率愈大愈大）面心立方結構層錯能低面心立方結構層錯能低 School of Manufacturing

10、Science and Engineering102. The role of alloying elements on steel2.1 Interaction between alloying elements and iron2.2 Interaction between alloying elements and carbon2.3 Stacking fault energy of austeniteSchool of Manufacturing Science and Engineering112. The role of alloying elements on steel2.1

11、Interaction between alloying elements and ironPurpose：Using the interaction of the elements and iron, controlling the type and content of the alloy elements in the steel to obtain the desired microstructure1394Cg-g-FeFCCa-a-FeBCCd-d-FeB BCC912CSchool of Manufacturing Science and Engineering122. The

12、role of alloying elements on steel2.1 Interaction between alloying elements and iron（1）Expanding area： Mn、Ni、Co、 C、N、 Cu（A4、A3）Fe-M無限互溶無限互溶Fe-M有限互溶有限互溶School of Manufacturing Science and Engineering132. The role of alloying elements on steel2.1 Interaction between alloying elements and iron（2）reduci

13、ng area： Cr、V、Si、 Al、Ti、Mo、W（A3、A4）v 與與F無限互溶元素無限互溶元素:使奧氏體區(qū)被封閉；使奧氏體區(qū)被封閉； （ Cr、V、Si、Al、Ti、Mo、W）v 與與F有限互溶元素有限互溶元素:使使A區(qū)縮小。區(qū)縮小。 （ B、Nb、Ta、Zr）School of Manufacturing Science and Engineering142. The role of alloying elements on steel2.1 Interaction between alloying elements and ironInfluencing factors ： La

14、ttice type, the size and structure of the atoms, and electrochemical factors.合金元素與鐵還可能形成金屬間化合物合金元素與鐵還可能形成金屬間化合物 。 （如（如Fe-Cr、Fe-V、Fe-Mo等合金）等合金）總結：運用合金元素和鐵的相互作用規(guī)律，控制合總結：運用合金元素和鐵的相互作用規(guī)律，控制合金元素種類和含量，得到所需要的組織。金元素種類和含量，得到所需要的組織。School of Manufacturing Science and Engineering152. The role of alloying eleme

15、nts on steel2.1 Interaction between alloying elements and ironEngineering meanings： Using the interaction between alloy elements and iron， to require the needed structure. 特例：特例：OCr18Ni9TiSchool of Manufacturing Science and Engineering162. The role of alloying elements on steel2.2 Interaction betwee

16、n alloying elements and carbon表現(xiàn)在是否形成碳化物或形成碳化物傾向性的大小。表現(xiàn)在是否形成碳化物或形成碳化物傾向性的大小。（strengthening phase）Research purpose：l Types, character and distribution of carbide in the steel.l The influence on the phase transformation.School of Manufacturing Science and Engineering172. The role of alloying elements

17、on steel2.2 Interaction between alloying elements and carbon(1)non-carbide forming element(非碳化物形成元非碳化物形成元素素)：不與不與C形成化合物，但可固溶于形成化合物，但可固溶于a a-Fe或或g g-Fe中，中，或形成氮化物等化合物?；蛐纬傻锏然衔铩?elements：Ni、Cu、Si、Co、Al、N、P等等School of Manufacturing Science and Engineering182. The role of alloying elements on steel2.2

18、Interaction between alloying elements and carbon (2)Carbide forming element(碳化物形成元素碳化物形成元素)： （Fe、Mn、Cr、W、Mo、V、Nb、Zr、Ti）a) 周期表中周期表中Fe的的“左左” ，但有例外！，但有例外！Ni, Co can form into cabon, but its stability is lower than Fe3C.Mn is easy to solid-soluted into Fe3C，forming alloy cementite.b) d電子層未滿電子層未滿：碳化物具有金屬

19、鍵結合的性質：碳化物具有金屬鍵結合的性質c) Stability of carbide：主要由：主要由d電子層電子層的未填滿程度決定。的未填滿程度決定。 由強到弱由強到弱：Ti, Zr, Nb, V, Mo, W, Cr, Mn, FeSchool of Manufacturing Science and Engineering192. The role of alloying elements on steel2.2 Interaction between alloying elements and carbonDifferent type of the carbide:(1) rc / r

20、me 0.59 : complex lattice carbide Cr23C6, Cr7C3, Fe3C (2) rc / rme 150）：）：slowing M decomposition is due to the strong carbide formation elements hindering C precipiting from M.5. Effects of alloying elements on phase transformationSchool of Manufacturing Science and Engineering815.4 Effect of alloy

21、 elements on tempering（1）Effect on M decomposition :（effect of carbon elements on it）In carbon steel, carbon precipitation temperaure is 250-350 ；In alloy steel, is 400-500 .carbon elements:V、Nb、Cr、Mo、W. non-carbide has little effect on this process, Si can slow M decomposition 。5. Effects of alloyi

22、ng elements on phase transformationSchool of Manufacturing Science and Engineering825.4 Effect of alloy elements on tempering（2）Effect on retained austenite tansformaionLittle retained austenite exist in the low carbon and low alloy steel after hardening, tempering temperature is 200-300，decompose i

23、t into M or B下下.The decomposition temperature of retained A rises when adding alloy elements, Cr、Mn、Si have the most remarkable effect.5. Effects of alloying elements on phase transformationSchool of Manufacturing Science and Engineering835.4 Effect of alloy elements on tempering（2）Effect on retaine

24、d A transformation In the high alloying elements containing a lot W、Mo、V、Cr，retained A preipitates carbon in the tempering process, Ms rising，exceeding room temperature, forming M after cooling.Hardness of hardening steel increases after tepering.5. Effects of alloying elements on phase transformati

25、on The phenomenon that retained A transform into M in tempering coolig in high alloying steel, hardness inceasing is called the secondary hardening（A-M）.School of Manufacturing Science and Engineering845.4 Effect of alloy elements on tempering（3）Effect on carbide formation, gathering together, growi

26、ng upv There is no influence of alloy elements on -carbon(Fe2.4C) forming.(got at low temperature tempering)v T回火回火， carbon transforms into cementite at 260 ; Si、Al、Cr will delay this transformation.（ Si、Al lead to the temperature rising to 350)v T回火回火，the diffusion of alloy elements：carbon forming

27、elements enrich in cementite, replacing Fe，formng alloying cementite and agglomeration. Si、V、W、Mo、Cr hinder it growing up.5. Effects of alloying elements on phase transformationSchool of Manufacturing Science and Engineering855.4 Effect of alloy elements on tempering（3）Effect on carbide formation, g

28、athering together, growing up在含在含W、Mo、V較多的鋼中。較多的鋼中。reasons：precipitating highly dispersed carbides from M in the tempering. stable at high temperature, not easy to gather and grow up.（Make it excellent high temperature strength）The secondary hardening5. Effects of alloying elements on phase transfor

29、mationSchool of Manufacturing Science and Engineering865.4 5.4 Effect of alloy elements on tempering（4 4）Effect on ferrite recrystallization回復（回復（reversion）：Structure has no obvious change, keep fibrous Structure has no obvious change, keep fibrous grain(grain(纖維狀纖維狀)；、H 、 、 change little；Residual s

30、tress significantly reduced.再結晶（再結晶（Recrystallization） ：The process of microstructure The process of microstructure reorganization.Grain shape changes, strength/hardness reorganization.Grain shape changes, strength/hardness significantly lower , plasticity/tenacity increased significantly lower , pl

31、asticity/tenacity increased significantly.significantly.5. Effects of alloying elements on phase transformationSchool of Manufacturing Science and Engineering875.4 Effect of alloy elements on tempering（4）Effect on ferrite recrystallizationMost alloy elements delay ferrite recrystallizationCo、Mo、W、V、

32、Cr improve recrystallization temperature，Ni influence little.eg.：In carbon steel，phase starts reversion process exceeding 400, recrystallization at 500；when adding 2%Co, recrystallization temperature can rise to630.5. Effects of alloying elements on phase transformationSchool of Manufacturing Scienc

33、e and Engineering885.4 Effect of alloy elements on tempering（5） The effect on temper brittleness Means the hardened steel after tempering happened to toughness decline phenomenon.v The first class temper brittleness ：low temperature temper brittleness, dont eliminate. generating temperature 450650。v

34、 reasons：retained austenite transformation；Carbide precipitation;Impurities partial polyv 加入加入Mo、W、V、Al can weaken little；Mn、Cr can promote；Si、Cr make it moving to higher temperatures.。5. Effects of alloying elements on phase transformationSchool of Manufacturing Science and Engineering895.4 Effect

35、of alloy elements on tempering（5） The effect on temper brittleness second class temper brittleness ： high temperature temper brittleness。generating temperature 450650。Mo、W can weaken；Mn、Cr、Ni can promote；v 防止：防止：rapid cooling after tempering（Avoid elements tsegregation at grain boundaries and precip

36、itatio.）Adding Mo、W inhibitting the second tempering brittlenessImprove the metallurgical quality, reduce the impurity elements in steel5. Effects of alloying elements on phase transformationSchool of Manufacturing Science and Engineering906. Metallurgical quality of steel鋼材在生產過程中經過冶煉、鑄造、軋制或鍛造等工序，最后

37、成材。鋼材在生產過程中經過冶煉、鑄造、軋制或鍛造等工序，最后成材。由這些過程所控制的質量，稱為冶金質量。由這些過程所控制的質量，稱為冶金質量。6.1 The macroscopic defects of steel： shrinkage porosity疏松疏松, shrinkage cavities縮孔縮孔, segregation偏析偏析,bubble氣泡氣泡,crack裂紋裂紋,flakes白點白點shrinkage porosity：組織不致密。措施：控制冶煉和鑄錠質量，組織不致密。措施：控制冶煉和鑄錠質量，減減少鋼中氣體和雜質。少鋼中氣體和雜質。segregation：化學成分不均勻

38、?；瘜W成分不均勻。采用高溫擴散退火。采用高溫擴散退火。shrinkage cavities：凝固過程，體積收縮，在冒口一端出現(xiàn)。采取凝固過程，體積收縮，在冒口一端出現(xiàn)。采取正確澆注工藝、合理定型設計，并適當切除冒口。正確澆注工藝、合理定型設計，并適當切除冒口。School of Manufacturing Science and Engineering916. Metallurgical quality of steel6.2 high magnification defect of steel： Banded structure帶狀組織帶狀組織, non-metallic inclusions 非金屬夾雜非金屬夾雜,carbide liquid chromatography碳化物液碳化物液析析, widmanstatten structure魏氏組織魏氏組織, net carbide網狀碳化物網狀碳化物6.3斷口分析：斷口分析：（自學）（自學）School of Manufacturing Science and Engineerin