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在现代技术中,广泛地采用热处理状态的变形铝合金大型半成品。对这些半成品提出的基本要求之一就是良好的淬透性。采用完全性透的细棒的临界直径(d_(kp))作为评价淬透性的基本依据,这时,其中心部位强度的降低不应超过标准值的5％。因此,对合金AK4-1来说,d_(kp)=250毫米。按与多温冷却“C”型曲线相切的倾角鉴定直径为d_(kp)的细棒中心图表上的临界冷却速度,并用V_(kp·T)表示,该“C”型曲线能保证获得95％σ_B(在图1中用虚线示出的)。
In modern technology, widely used deformed large-scale aluminum alloy semifinished products in a heat-treated state. One of the basic requirements for these semi-finished products is good hardenability. The critical diameter (d_ (kp)) of a perfectly through thin rod is used as the basis for the evaluation of hardenability. In this case, the reduction of the central part strength should not exceed 5% of the standard value. Therefore, for the alloy AK4-1, d_ (kp) = 250 mm. The critical cooling rate on a thin bar center chart of diameter d_ (kp) is identified as the angle of inclination tangent to the “C” curve of the multistage cooling and is expressed in V_ (kp · T), which guarantees that 95% σ_B (shown in phantom in FIG. 1).