Abstract

Flaking of galvannealed steel due to interfacial bond failure during press-forming results in a deterioration in product quality and reduced productivity. To solve this problem, an understanding of bonding at the interface must be gained in terms of the microstructure. In this research, the relationship between coating adhesion strength and the evolution of interface microstructure was investigated using an interstitial free steel sheet. Hat channel drawing with a bead machine and stud pin tests were used to measure the flaking resistance and adhesive bond strength, respectively. A strong relationship was found between flaking resistance and interfacial bond strength. High bond strength samples exhibited two distinctive microstructures, Zn-penetrated grain boundary, and rough, island-like knoll, with the knoll always surrounded by the grain boundaries. The rough knoll, with etch pits on the top, formed underneath a crater, and a deep pit was observed at the grain boundary. After stud pin testing, coating residues remained mostly on the Zn penetrated and rough knoll substrates, indicating strong coating adhesion reinforced by a mechanical interlocking effect that originated from the two distinctive microstructures.

Graphic Abstract

中文翻译：

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界面显微结构特征与镀锌无间隙钢粘结强度的相关性

摘要

由于压制成型过程中界面结合失效导致镀锌钢剥落导致产品质量下降和生产率下降。为了解决这个问题，必须从微观结构方面了解界面处的键合。在这项研究中，使用无间隙钢板研究了涂层附着强度与界面微观结构演变之间的关系。分别使用珠机拉制帽槽和螺栓销测试来测量抗剥落性和粘合强度。在抗剥落性和界面结合强度之间发现了很强的关系。高结合强度样品表现出两种独特的微观结构，锌穿透晶界和粗糙的岛状小丘，小丘总是被晶界包围。粗糙的小丘，顶部有蚀刻坑，形成在陨石坑下方，在晶界处观察到一个深坑。在螺柱销测试后，涂层残留物主要保留在 Zn 渗透和粗糙的凸起基底上，表明由于两种不同的微观结构产生的机械互锁效应增强了强大的涂层附着力。

图形摘要