熱作模具鋼中納米級析出物及鋼的綜合強化機理研究
發(fā)布時間：2018-12-08 17:26
【摘要】：4Cr5MoSiV1鋼,即美國鋼號H13(AISI)是一種空冷硬化型熱作模具鋼,H13鋼具有較高的熱強度和硬度,在中溫條件下具有很好的韌性、熱疲勞性能和一定的耐磨性。在較低的奧氏體化溫度下空淬,熱處理變形小,空淬時產(chǎn)生氧化皮傾向小,可以抵抗熔融鋁的沖蝕作用。該鋼廣泛用于制造熱擠壓模具,芯棒、模鍛錘的錘模,鍛造壓力機模具,精鍛機用模具以及鋁、銅及其合金的壓鑄模。 本文根據(jù)國家自然科學(xué)基金項目“熱作模具鋼中納米析出物與鋼的綜合強化機理研究”(No.51274031)所要求的內(nèi)容,研究了不同熱處理狀態(tài)下析出物的情況,特別是納米級析出物的種類和分布規(guī)律以及它們對鋼力學(xué)性能的影響,得出如下主要結(jié)論： 1)電渣錠態(tài)H13主要析出V8C7和M23C6,形態(tài)為方形和球形,尺寸在200nm左右。通過計算發(fā)現(xiàn)：電渣凝固過程中析出物種類及析出相對量為V8C7:VC:V2C:Cr7C3:Cr23C6:MoC:Mo2C=1.19:1.22:0.28:4.33:5.36:1.65:1.56。 2)利用熱力學(xué)計算+電解化學(xué)相分析+碳復(fù)型+透射電鏡的方法,研究了H13電渣錠退火態(tài)下析出物的分布規(guī)律及其對屈服強度的影響。發(fā)現(xiàn),從H13鋼錠的橫向看,由中心到表面析出物尺寸有減小的趨勢,體積分?jǐn)?shù)增大；從H13鋼錠的縱向看,由上部到下部,析出數(shù)量不斷增多,尺寸不斷減小,由中部到下部析出物尺寸略有增大。退火態(tài)析出物主要以VC、M6C和M7C3為主,總平均尺寸為243.5nm,單位面積析出量為1.44個。研究發(fā)現(xiàn),納米級析出物對屈服強度的貢獻為311.32MPa。 3)利用相同方法分析了H13淬火及回火態(tài)析出物的情況。淬火態(tài)析出物種類主要是VC、M6C及少量的M23C6,總平均尺寸為150.5nm,單位面積析出量0.67個。析出強化量對屈服強度的貢獻為19%。通過研究2小時和20小時的回火態(tài)析出物情況發(fā)現(xiàn),析出物的種類主要是：VC、M6C、M3C以及M23C6；回火2小時的總平均尺寸減小為82.6nm,但單位面積析出量增加到5.37個。析出強化量對屈服強度的貢獻也相應(yīng)增加到28%。回火20小時后析出物總平均尺寸有少量增加,為88.3nm,單位面積析出量也相應(yīng)增加為6.5個,但析出強化量對屈服強度的貢獻卻增加到39%。 4)從納米級析出物對H13的強化角度出發(fā),對不同的淬火、回火溫度以及保溫時間研究析出物對鋼性能的影響。研究表明：H13的淬回火的最佳工藝路線為：1373K淬火30min,油冷至室溫：在863K下回火4小時,空冷。在這樣的工藝條件下,H13中的析出物細(xì)小,數(shù)量適中。力學(xué)性能最好。 5)研究了兩種不同回火時間下細(xì)晶強化、析出強化、固溶強化和位錯強化對H13的綜合強化機理。結(jié)果表明,回火態(tài)下,H13各強化機制對屈服強度的貢獻強弱依次為：細(xì)晶強化、析出強化、固溶強化和位錯強化。
[Abstract]:4Cr5MoSiV1 steel, American steel H13 (AISI), is a kind of air-cooled hardening hot work die steel. H13 steel has high thermal strength and hardness, and has good toughness, thermal fatigue property and certain wear resistance at medium temperature. When austenitizing temperature is low, the deformation of heat treatment is small, and the tendency of oxidation is small, which can resist the erosion of molten aluminum. The steel is widely used in manufacturing hot extrusion die, mandrel, hammer die of die forging hammer, die of forging press, die of precision forging machine and die casting die of aluminum, copper and its alloy. According to the requirement of the National Natural Science Foundation of China, "Comprehensive strengthening Mechanism of Nano-precipitates and Steel in Hot work Die Steel" (No.51274031), the situation of precipitates in different heat treatment states has been studied in this paper. The main conclusions are as follows: 1) the electroslag ingot H13 precipitates V8C7 and M23C6, the shape is square and spherical, and the size is about 200nm. It is found by calculation that the type and relative amount of precipitates during electroslag solidification is V8C7: VC7: V2C7C3: Cr23C6: Mo2C1.191.22: 0.284.33: 5.36: 1.56: 1.56. 2) the distribution of precipitates in H13 electroslag ingot annealed and its influence on yield strength were studied by means of thermodynamics calculation of electrolysis chemical phase analysis of carbon complex transmission electron microscope (TEM). It is found that the size of the precipitates from the center to the surface decreases and the volume fraction increases from the transverse side of the H13 ingot. From the longitudinal point of view of H13 ingot, the amount of precipitate increases and the size decreases from the upper part to the lower part, and the size of the precipitate increases slightly from the middle to the lower part. The main precipitates in annealed state are VC,M6C and M7C3, the total average size is 243.5 nm and the amount of precipitation per unit area is 1.44. It is found that the contribution of nanometer precipitates to yield strength is 311.32 MPa. 3) the precipitation of H 13 quenching and tempering was analyzed by the same method. The main precipitates in quenched state are VC,M6C and a small amount of M23C6, the total average size is 150.5 nm, and the precipitation amount per unit area is 0.67. The contribution of precipitation strengthening amount to yield strength is 19. By studying the tempering state precipitates for 2 hours and 20 hours, it is found that the types of precipitates are mainly VC,M6C,M3C and M23C6, and the total average size of tempering for 2 hours decreases to 82.6 nm, but the amount of precipitation per unit area increases to 5.37. The contribution of precipitation strengthening amount to yield strength is also increased to 28%. After tempering for 20 hours, the total average size of precipitates increased slightly to 88.3 nm, and the amount of precipitation per unit area increased to 6.5, but the contribution of precipitation strengthening to yield strength increased to 39. 4) from the point of view of strengthening H13 by nanometer precipitates, the effect of precipitates on the properties of steel was studied at different quenching, tempering temperature and holding time. The results showed that the optimum quenching and tempering process of H13 was 1373K for 30 min, oil cooled to room temperature, tempering at 863K for 4 hours and air cooling. Under such technological conditions, the precipitates in H 13 are fine and moderate in quantity. The mechanical properties are the best. 5) the mechanism of strengthening H13 by fine grain strengthening, precipitation strengthening, solution strengthening and dislocation strengthening at two different tempering times was studied. The results show that the contribution of H13 strengthening mechanism to yield strength is as follows: fine grain strengthening, precipitation strengthening, solid solution strengthening and dislocation strengthening.
【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TG142.1
本文編號：2368718
[Abstract]:4Cr5MoSiV1 steel, American steel H13 (AISI), is a kind of air-cooled hardening hot work die steel. H13 steel has high thermal strength and hardness, and has good toughness, thermal fatigue property and certain wear resistance at medium temperature. When austenitizing temperature is low, the deformation of heat treatment is small, and the tendency of oxidation is small, which can resist the erosion of molten aluminum. The steel is widely used in manufacturing hot extrusion die, mandrel, hammer die of die forging hammer, die of forging press, die of precision forging machine and die casting die of aluminum, copper and its alloy. According to the requirement of the National Natural Science Foundation of China, "Comprehensive strengthening Mechanism of Nano-precipitates and Steel in Hot work Die Steel" (No.51274031), the situation of precipitates in different heat treatment states has been studied in this paper. The main conclusions are as follows: 1) the electroslag ingot H13 precipitates V8C7 and M23C6, the shape is square and spherical, and the size is about 200nm. It is found by calculation that the type and relative amount of precipitates during electroslag solidification is V8C7: VC7: V2C7C3: Cr23C6: Mo2C1.191.22: 0.284.33: 5.36: 1.56: 1.56. 2) the distribution of precipitates in H13 electroslag ingot annealed and its influence on yield strength were studied by means of thermodynamics calculation of electrolysis chemical phase analysis of carbon complex transmission electron microscope (TEM). It is found that the size of the precipitates from the center to the surface decreases and the volume fraction increases from the transverse side of the H13 ingot. From the longitudinal point of view of H13 ingot, the amount of precipitate increases and the size decreases from the upper part to the lower part, and the size of the precipitate increases slightly from the middle to the lower part. The main precipitates in annealed state are VC,M6C and M7C3, the total average size is 243.5 nm and the amount of precipitation per unit area is 1.44. It is found that the contribution of nanometer precipitates to yield strength is 311.32 MPa. 3) the precipitation of H 13 quenching and tempering was analyzed by the same method. The main precipitates in quenched state are VC,M6C and a small amount of M23C6, the total average size is 150.5 nm, and the precipitation amount per unit area is 0.67. The contribution of precipitation strengthening amount to yield strength is 19. By studying the tempering state precipitates for 2 hours and 20 hours, it is found that the types of precipitates are mainly VC,M6C,M3C and M23C6, and the total average size of tempering for 2 hours decreases to 82.6 nm, but the amount of precipitation per unit area increases to 5.37. The contribution of precipitation strengthening amount to yield strength is also increased to 28%. After tempering for 20 hours, the total average size of precipitates increased slightly to 88.3 nm, and the amount of precipitation per unit area increased to 6.5, but the contribution of precipitation strengthening to yield strength increased to 39. 4) from the point of view of strengthening H13 by nanometer precipitates, the effect of precipitates on the properties of steel was studied at different quenching, tempering temperature and holding time. The results showed that the optimum quenching and tempering process of H13 was 1373K for 30 min, oil cooled to room temperature, tempering at 863K for 4 hours and air cooling. Under such technological conditions, the precipitates in H 13 are fine and moderate in quantity. The mechanical properties are the best. 5) the mechanism of strengthening H13 by fine grain strengthening, precipitation strengthening, solution strengthening and dislocation strengthening at two different tempering times was studied. The results show that the contribution of H13 strengthening mechanism to yield strength is as follows: fine grain strengthening, precipitation strengthening, solid solution strengthening and dislocation strengthening.
【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TG142.1
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