本文選題：錫 + 銅��； 參考：《北京科技大學》2015年博士論文

【摘要】：針對西鋼齒輪鋼20CrMnTi中Sn等殘余元素含量高,生產(chǎn)過程中易產(chǎn)生開裂以及表面缺陷、產(chǎn)品組織及淬透性不穩(wěn)定等問題,本文對20CrMnTi鋼中Sn等殘余元素的影響進行了較為系統(tǒng)的研究；首次開展殘余元素Sn對20CrMnTi鋼組織轉變及性能包括力學、沖擊、淬透性及疲勞性能等方面的系統(tǒng)研究；同時對Sn等殘余元素危害20CrMnTi鋼熱塑性的機理、改善熱塑性的方法、高溫氧化行為以及對熱塑性改善后的20CrMnTi鋼組織轉變及淬透性進行了研究。主要結論如下： 本研究中,隨著Sn含量的增加,馬氏體轉變臨界冷速降低,珠光體轉變區(qū)域變寬,0.049%的Sn使得Ac3升高了15℃,馬氏體形成溫度降低13℃。冷速均控制在0.2-1℃/s左右時可獲得均勻的鐵素體+珠光體組織。Sn含量小于0.049%時,隨著Sn含量的增加,抗拉強度和屈服強度有所提高,對面縮率和斷后伸長率的影響不大,拉伸斷口皆為韌窩狀斷裂,沖擊性能降低,沖擊斷口皆為準解理斷裂。對淬透性和疲勞性能無明顯影響。 Sn、Cu惡化20CrMnTi鋼的熱塑性的主要機理是：①Sn的晶界偏聚,降低20CrMnTi鋼的晶界能,弱化晶粒間聚合力,加速晶界微孔的形成和長大以及Sn能阻礙20CrMnTi鋼動態(tài)再結晶的發(fā)生；②硫化銅析出相于晶界析出,促進微孔的形成和裂紋聚合以及Cu能阻礙動態(tài)再結晶的發(fā)生。隨著Sn含量、Cu當量的增加,20CrMnTi鋼的熱塑性明顯降低,熱脆性區(qū)變寬,在熱脆性區(qū)內,熱塑性先降低后升高,且均在750℃出現(xiàn)塑性谷底。先共析鐵素體于奧氏體晶界析出導致塑性谷底的產(chǎn)生,因為鐵素體的屈服強度低于奧氏體的屈服強度,在拉伸過程中產(chǎn)生應力集中,惡化熱塑性。20CrMnTi鋼的臨界Sn含量為0.021%、臨界Cu當量為0.15。 B和稀土Y能夠顯著改善含錫20CrMnTi鋼的熱塑性。隨著B/Y含量的增加,熱脆性區(qū)變小,塑性谷底變淺且均向低溫區(qū)移動,熱塑性逐漸提高,其主要機理是鋼中添加B/Y能夠抑制Sn的晶界偏聚,增加晶間聚合力,阻礙奧氏體-鐵素體轉變,防止鐵素體在奧氏體晶界析出,增加晶界滑移阻力,加快動態(tài)再結晶的發(fā)生以及抑制雜質元素S的晶界偏聚,同時B還能促進鐵素體于晶內形核,軟化奧氏體,提高奧氏體的變形能力,從而改善含錫20CrMnTi鋼熱塑性。本研究中,添加92ppmB/0.05%Y對含錫20CrMnTi鋼熱塑性改善效果最佳。 高溫氧化行為研究發(fā)現(xiàn),含錫20CrMnTi鋼在1150℃及1250℃時于空氣中氧化1h,因為Sn在基體中具有較大的溶解度和擴散系數(shù),在氧化層/基體界面均未發(fā)現(xiàn)富Sn相的存在。當銅錫共存時,1150℃空氣中氧化1h,因Cu的擴散系數(shù)較小且Sn能降低Cu在奧氏體中的溶解度,所以在氧化層/基體界面發(fā)現(xiàn)富Cu相存在；在1250℃氧化時,則因界面處富Cu相的富集量小于消耗量,氧化層/基體界面未發(fā)現(xiàn)富Cu相。氧化層分為三層,最外層為Fe2O3層,中間為Fe3O4層,最內層為FeO層。對不同Si含量的含銅、錫鋼的高溫氧化行為研究發(fā)現(xiàn),Si能降低氧化速率,進而降低氧化層/基體界面處富Cu液相的量,減少晶界滲入；同時,增大內氧化程度,增加氧化層/基體界面粗糙度,促進界面處富Cu液相向氧化層中遷移,進一步減少界面處富Cu液相的量,抑制熱脆的產(chǎn)生。 添加92ppmB的含錫20CrMnTi鋼Ac3溫度為844℃,因此,淬火加熱溫度應選擇溫度范圍為874℃～894℃。冷速控制在0.2～1℃/s左右時可獲得均勻的鐵素體+珠光體組織。當冷速為3℃/s時,組織主要為粒狀貝氏體+馬氏體混合組織,同時有極少量的鐵素體存在；當冷速大于10℃/s時,鋼中全為馬氏體組織。B能夠提高含錫20CrMnTi鋼的淬透性,B含量由15ppm增加到90ppm時,淬透性雖略有變化,但總體差別不大。
[Abstract]:In view of the high content of Sn and other residual elements in the 20CrMnTi steel gear steel, it is easy to produce cracking and surface defects in the process of production and the instability of product and hardenability. The influence of the residual elements such as Sn in 20CrMnTi steel is systematically studied in this paper. The transformation and performance package of the residual element Sn on the microstructure of 20CrMnTi steel for the first time is carried out. The systematic research on mechanics, impact, hardenability and fatigue properties, and the mechanism of Sn and other residual elements to harm the thermal plasticity of 20CrMnTi steel, the method of improving the thermal plasticity, the oxidation behavior at high temperature, and the transformation and hardenability of the 20CrMnTi steel after the improvement of thermoplasticity are studied. The main conclusions are as follows:
In this study, with the increase of Sn content, the critical cooling speed of martensitic transformation is reduced and the pearlite transition region broadens. The 0.049% Sn makes Ac3 rise 15 degrees C, and the martensite formation temperature decreases by 13. When the cold speed is controlled at 0.2-1 C /s, the.Sn content of the homogeneous ferrite + pearlite fabric is less than 0.049%, with the increase of the Sn content. The tensile strength and yield strength are improved, and the effect on the shrinkage and the elongation at the post break is not significant. The tensile fracture is a dimple fracture, the impact property is reduced, and the impact fracture is all quasi cleavage fracture. It has no obvious effect on the hardenability and fatigue properties.
The main mechanism of Sn, Cu to deteriorate the thermal plasticity of 20CrMnTi steel is: (1) the grain boundary segregation of Sn, reducing the grain boundary energy of 20CrMnTi steel, weakening the polymerization force between grain, accelerating the formation and growth of the grain boundary micropores, and hindering the occurrence of dynamic recrystallization of the 20CrMnTi steel, and the precipitation of copper sulfide precipitates at grain boundaries to promote the formation of micropores and the polymerization of cracks. And Cu can impede the occurrence of dynamic recrystallization. With the increase of Sn content and Cu equivalent, the thermal plasticity of 20CrMnTi steel decreases obviously, and the thermal brittleness area becomes wider. In the thermal brittleness region, the thermal plasticity decreases first and then increases, and the plastic valley bottom appears at 750 degrees. The strength is lower than the yield strength of austenite, and the stress concentration is produced during the tensile process. The critical Sn content of the thermoplastic.20CrMnTi steel is 0.021%, and the critical Cu equivalent is 0.15.
B and rare-earth Y can significantly improve the thermal plasticity of tin containing 20CrMnTi steel. With the increase of B/Y content, the thermal brittleness area becomes smaller, the plastic bottom of the grain becomes shallow and is moving to the low temperature zone, and the thermal plasticity increases gradually. The main mechanism is that the addition of B/Y in steel can inhibit the grain boundary segregation of Sn, increase the intergranular polymerization force, obstruct the transformation of austenite ferrite and prevent ferrite. The body is precipitated in the austenite grain boundary, increasing the sliding resistance of grain boundary, accelerating the occurrence of dynamic recrystallization and inhibiting the segregation of the grain boundary of the impurity element S. At the same time, B can also promote the nucleation of the ferrite, soften the austenite, improve the deformability of the austenite, and improve the thermal plasticity of the tin containing 20CrMnTi steel. In this study, 92ppmB/0.05%Y is added to the 20Cr containing tin. The thermo plastic improvement effect of MnTi steel is the best.
The study of oxidation behavior at high temperature found that the 20CrMnTi steel containing tin oxide was oxidized at 1150 and 1250 C in the air, because Sn had large solubility and diffusion coefficient in the matrix, and no rich Sn phase was found in the oxidation layer / matrix interface. When copper and tin coexisted, 1H was oxygenated in the air at 1150 C, because the diffusion coefficient of Cu was small and Sn could reduce Cu in the Austria. The solubility of the Cu phase is found in the oxidation layer / matrix interface; at 1250 C, the enrichment of the rich Cu phase at the interface is less than the consumption, and the rich Cu phase is not found in the oxidation layer / matrix interface. The oxidation layer is divided into three layers, the most outer layer is Fe2O3 layer, the middle is Fe3O4 layer, and the most inner layer is FeO layer. The copper and tin with different Si content The study of high temperature oxidation behavior of steel shows that Si can reduce the oxidation rate, then reduce the amount of Cu liquid rich in the oxidation layer / matrix interface, reduce the infiltration of grain boundary, and increase the degree of internal oxidation, increase the roughness of the oxidation layer / matrix interface, promote the migration of the rich Cu liquid to the oxidation layer at the interface, and further reduce the amount of the rich Cu liquid phase at the interface, and restrain the amount of the rich liquid phase at the interface. The production of heat and brittleness.
The temperature of Ac3 containing tin 20CrMnTi steel added with 92ppmB is 844 C. Therefore, the temperature range of quenching should be selected from 874 to 894 C. The uniform ferrite + pearlite structure can be obtained when the cooling rate is about 0.2 ~ 1 C /s. When the cooling rate is 3 /s, the microstructure is mainly granular bainite + martensite and a very small amount of iron. When the cooling speed is more than 10 /s, the martensitic.B can improve the hardenability of the stannous 20CrMnTi steel, while the B content is increased from 15ppm to 90ppm, although the hardenability changes slightly, but the overall difference is not significant.
【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG142.1

【參考文獻】

相關期刊論文 前10條

1 賀信萊,褚幼義,柯俊;硼鋼淬透性與硼偏聚[J];北京鋼鐵學院學報;1983年01期

2 朱元凱,董元篪,彭(忄育)強,魏壽昆;CaC_2-CaF_2渣系對鐵水脫砷的研究[J];北京鋼鐵學院學報;1986年02期

3 林勤;葉文;杜垣勝;余宗森;;Behaviour of Rare Earths in Solid Solution in Steel[J];Journal of Materials Science & Technology;1990年06期

4 閻立懿,裴麗苗,李廣田;真空條件下鋼液去銅的試驗[J];東北大學學報;2003年10期

5 劉春明,周燕島,安彥兼次,木村宏;微量硼對高純鐵硫合金沿晶斷裂和硫沿晶偏析的影響[J];東北大學學報;1999年01期

6 董元篪;施志平;張立民;彭(忄育)強;洪彥若;;鐵水脫砷的研究[J];鋼鐵;1984年09期

7 梁英生;;中國含砷鋼研究的進展[J];鋼鐵;1986年01期

8 冼愛平,張盾,王儀康;鋼中殘余元素及其對鋼性能的影響[J];鋼鐵;1999年10期

9 李素芹,李士琦,王雅娜;鋼中殘余有害元素控制對策的分析與探討[J];鋼鐵;2001年12期

10 婁艷芝;柳得櫓;毛新平;柏明卓;;CSP工藝鈦微合金鋼中的碳氮化鈦析出相[J];鋼鐵;2010年02期

，

本文編號：2109072