(1. 大连理工大学 工业装备结构分析国家重点实验室,大连 116024; 2. 大连理工大学 汽车工程学院,大连 116024)
摘 要: 基于自主设计的圆台模具淬火实验平台,研究高强度7075-T6铝合金在HFQ温成形过程中的瞬态传热规律。通过Beck非线性估算法(Beck反算法)获得界面换热系数(IHTC)在不同因素下(包括合模压强与表面粗糙度)随温度变化的瞬态换热规律,并分析各因素对IHTC的影响机理。结果表明:Beck反算法在计算瞬态换热系数时具有较高的计算精度。7075-T6铝合金与模具界面的瞬态换热系数随压强增大而增大,当压强增大到80 MPa时,瞬态平均换热系数IHTC趋近于3375 W/(m2?K)。进一步,表面粗糙度也会影响7075-T6铝合金温成形过程的IHTC,当粗糙度大于0.57 μm并小于0.836 μm时,IHTC随粗糙度的增大而明显减小,当粗糙度小于0.57 μm或大于0.836 μm时,IHTC值均随粗糙度的增大而缓慢减小。
关键字: 7075-T6铝合金;HFQ温成形;界面换热系数;Beck反算法;工艺因素
(1. State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, China; 2. School of Automotive Engineering, Dalian University of Technology, Dalian 116024, China)
Abstract:Based on self-developed cylindrical-die experimental model, transient heat transfer law of high-strength 7075-T6 aluminum alloy in HFQ warm forming was investigated in this paper. Beck’s non-linear estimation method (Beck’s method) was used to calculate IHTC under different processing factors, including different closure pressure and surface roughness. The results showed that Beck’s method has a high accuracy in calculating IHTC; The transient IHTC of 7075-T6 aluminum increases with the increases of closure pressure, and when pressure is above 80 MPa, IHTC approaches to 3375 W/(m2?K). Furthermore, surface roughness can also affect IHTC, when surface roughness is between 0.57 μm and 0.836 μm, IHTC decreases obviously with the increase of surface roughness, and when surface roughness is larger than 0.836 μm or less than 0.57 μm, IHTC decreases slowly with the increase of roughness.
Key words: 7075-T6 alloy; HFQ warm forming; IHTC; Beck’s method; process factor