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

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.