针对构件热加工过程变形控制的世界性难题，创建了差异壁厚/差异结构构件加热或冷却过程零畸变的等Biot数模型，首次以Biot数替代综合换热系数h，并将Biot数引入温度场方程，由此建立了随Biot数变化的动态温度场和应力场耦合模型。利用ABAQUS软件对ZL205A铝合金差异壁厚构件淬火过程的温度场和应力场进行了预报。模拟结果表明，ZL205A铝合金构件淬火变形源于差异壁厚导致的二者温度差；对于薄厚比为1：4制件，540℃固溶淬火0.37 s时，薄厚壁特征位置最大温差为276℃，厚壁中最大热应力84 MPa，超过相应温度下该合金屈服强度，导致制件淬火变形，且变形以径向变形为主。通过对厚壁或薄壁处以高导热或低导热系数覆层材料修饰，获得了差异壁厚的等Biot，并对修饰后的构件进行540℃固溶淬火变形进行预报。结果表明，与无修饰构件相比变形降低82.6%，实现了差异壁厚的准同步淬火。
闫牧夫
,
卢琛
,
张程菘
. 基于等Biot数的ZL205A铝合金大型薄壁件准同步淬火微变形研究[J]. 机械工程学报, 2018
, 54(9)
: 69
-76
.
DOI: 10.3901/JME.2018.09.069
The equal-Biot number model, on differential wall thickness and/or differential wall structure workpieces heating or quenching zero distortion, proposed by the researchers for the worldwide problem on the distortion control of workpieces during hot processing. Overall heat transfer coefficient h is replaced by Biot number for the first time. Biot number is introduced into the temperature field equation, and the coupled model of dynamic temperature field and stress field which changes with Biot number is built. The temperature field and stress field in ZL205A aluminum alloy differential wall thickness workpiece is predicted by ABAQUS software. The simulation results indicate that the quenching distortion in ZL205A aluminum alloy workpiece stem from the difference in temperature between thick-wall parts and thin-wall parts. The ratio of thin-wall thickness to thick-wall thickness of this workpiece is one to four, the maximum difference in temperature is 276℃ between thin-wall keypoints and thick-wall keypoints, the maximum thermal stress is 84 MPa in thick-wall parts more than the yield strength of this alloy on the corresponding temperature, and then the radial distortion occurred, on the 0.37 s quenching time after solution 540℃. The equal-Biot number of the differential wall thickness is achieved by coating high heat conduction layers to thick-wall parts or low heat conduction layers to thin-wall parts. The distortion after 540℃ solution and quenching is predicted. The results indicate that the quenching distortion reducing 82.6 percent compared with the workpiece without coating layer. The quasi-synchronous quenching of differential wall thickness workpiece is achieved.
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