Research On The Distortion Behavior Of H13 Steel By Wire Arc Additive Manufacturing

With the progress of “Made in China 2025” plan,the transformation and upgrading of manufacturing industry has accelerated in China.In recent years,with the rapid development of aerospace,shipbuilding,automotive and other fields,larger,lighter,and more complex metal components are being widely used.As a kind of advanced intelligent manufacturing technologies,wire-arc additive manufacturing(WAAM)has broad application prospects.Compared with the traditional manufacturing process,WAAM technology has the characteristics of high production efficiency,low processing cost and good forming performance.The distortion problem of H13 steel deposited by WAAM technology is studied,and path optimization and synchronous water cooling are proposed to mitigate the thermal distortion.In addition,the inherent strain theory is used to explain the mechanism of distortion generation and mitigation,which provides a theoretical basis for the engineering application of distortion mitigation of large structural parts.The influence of different scanning paths on the temperature field and distortion of components in the WAAM process were studied.Four scanning patterns of sequential pattern,symmetrical pattern,In-Out pattern and Out-In pattern were proposed to deposit bulk components with the same size.The research results show that the temperature history under different scanning patterns are significantly different.There is the highest peak temperature in the center of the substrate when Out-In pattern is used,and the most severe temperature fluctuation occurred in the sequential scan mode.The passes near the center of the substrate have the effect of mitigating distortion when Out-In and In-Out pattern were used;the accumulated distortion of the component gradually increased when depositing in sequential and symmetric patterns.The distortion produced by the Out-In pattern was the smallest20.38 mm,which was 68.6 % lower than the sequential pattern.A synchronous water cooling system was set up based on water cooling fixtures,variable power pumps,and constant temperature water tanks.By changing cooling conditions such as cooling water flow and water temperature,the synchronous water cooling technology was used to study the forming accuracy,deposition rate and longitudinal distortion of thin-walled parts.The research results show that,compared with natural cooling,the use of 25 ? water cooling during the WAAM process can save 83% of the manufacturing time and mitigate 83% of the bending distortion.The relationship between the macro size of the unsupported horizontal thin wall and the deposition process parameters and the welding torch inclination angle were studied.With the increase of heat input,the wall thickness gradually increased;the component force of the arc force in the direction of gravity increased with the welding torch inclination angle,the self-supporting effect of the thin wall is not enough to balance the resultant force in the vertical direction and flow occurs.WAAM technology can be competent for the manufacture of parts with conformal runners.Due to limited by the size of a single weld bead,subsequent milling process should be put into consideration during the design process.