本文選題：汽車卷簧 + 脫碳　； 參考：《安徽工業(yè)大學》2014年碩士論文

【摘要】：彈簧鋼是一種重要的機械設備基礎零件制造材料,現(xiàn)已廣泛應用于航空航天、汽車、鐵路等諸多領域。由于彈簧鋼的工作條件十分苛刻,對彈簧鋼的性能要求就十分嚴格。其中,抗疲勞和抗彈減性減退是影響彈簧鋼設計應力的主要因素,與其內(nèi)在質(zhì)量(化學成分、純凈度)、表面質(zhì)量(裂紋、凹坑、脫碳)以及微觀組織有密切關系。因此,要求彈簧鋼不僅具有較高的強度、良好的塑韌性,而且還要有一定淬透性、較低的脫碳敏感性和良好的加工性能。本文以常用于生產(chǎn)汽車安全帶卷簧用彈簧鋼Super6和SK5為研究對象,首先研究了兩種實驗鋼的表面脫碳規(guī)律,以避免在熱軋過程中發(fā)生表面脫碳:實驗室模擬兩種彈簧鋼的加熱工藝,分析加熱溫度和保溫時間對其脫碳層深度的影響。實驗結果表明:彈簧鋼Super6的脫碳敏感性要明顯高于彈簧鋼SK5的。對于彈簧鋼Super6可在700℃以上盡量減少加熱時間,950℃到1100℃內(nèi)迅速升溫,1100℃以上應盡量減少保溫時間,且熱卷溫度應在700℃以下;對于彈簧鋼SK5可在950℃以上盡量減少加熱時間,1100℃以上快速升溫,熱卷溫度控制在950℃以下即可。合理制定熱處理工藝,以穩(wěn)定提高兩種實驗鋼的疲勞壽命。利用JMatPro軟件模擬了彈簧鋼Super6和SK5的CCT曲線。根據(jù)JMatPro軟件預測結果,設計正交熱處理實驗方案,并運用極差分析進一步討論不同熱處理工藝對兩種實驗鋼力學性能(屈服強度、抗拉強度和延伸率)的影響規(guī)律,以得出兩種彈簧鋼的最佳熱處理工藝。兩種實驗鋼的最佳熱處理工藝為:彈簧鋼Super6在880℃淬火,保溫30 min后油淬,在430℃回火,保溫60 min空冷;彈簧鋼SK5在850℃淬火,保溫30 min后油淬,在400℃回火,保溫40 min后空冷。對比兩種實驗鋼回火后的微觀組織,分析導致兩種彈簧鋼疲勞壽命存在差異性的原因。通過對比發(fā)現(xiàn):熱處理后,兩種實驗鋼的組織均是回火屈氏體,彈簧鋼SK5較彈簧鋼Super6的回火屈氏體更細小,碳化物分布更彌散,位錯密度也更高;彈簧鋼Super6中存在大尺寸的未溶碳氮化物顆粒;彈簧鋼Super6中的形變織構和再結晶織構密度均大于彈簧鋼SK5中的,特別是{113}110和{331}110織構明顯增強。兩種彈簧鋼微觀組織的不同,最終導致兩者疲勞性能差異很大。結果表明:經(jīng)過優(yōu)化熱處理工藝處理過的兩種彈簧鋼,機械性能均滿足要求,其中彈簧鋼SK5的疲勞壽命大于40萬次,彈簧鋼Super6的疲勞壽命大于10萬次,均達到了高品質(zhì)汽車安全帶卷簧的疲勞壽命標準。
[Abstract]:Spring steel is an important manufacturing material for basic parts of machinery and equipment, which has been widely used in aerospace, automobile, railway and many other fields. Because the working condition of spring steel is very harsh, the performance requirement of spring steel is very strict. Among them, anti-fatigue and anti-elasticity decrease are the main factors that affect the design stress of spring steel, which is closely related to the internal quality (chemical composition, purity, surface quality (crack, pit, decarburization) and microstructure). Therefore, spring steel not only has high strength, good plastic toughness, but also has certain hardenability, low decarburization sensitivity and good processability. In this paper, the surface decarbonization of two kinds of experimental steels, Super6 and SK5, is studied. In order to avoid surface decarbonization during hot rolling, the heating process of two spring steels was simulated in laboratory, and the effects of heating temperature and holding time on the depth of decarburization layer were analyzed. The experimental results show that the decarburization sensitivity of spring steel Super6 is higher than that of spring steel SK5. For spring steel Super6, the heating time should be reduced as much as possible in the range of 700 鈩，

本文編號：1945150