Avoiding glass spot defect arising from roller hydrogen embrittlement via regulating protective atmosphere distribution

Abstract

A kind of float glass spot defect, characterized by small size, metallic luster, and difficult to clean, adheres only to the lower surface (contacts with molten tin) of the float glass ribbon. This defect causes serious production loss. Therefore, determining the precise source of this spot defect and the effective prevention of its occurrence is vital in the scientific interest and technological significance. Herein, we report a new idea for preventing glass spot defect resulting from roller hydrogen embrittlement (HE) via regulating protective atmosphere distribution. We also reveal its formation mechanism. The generation mechanism of this spot defect shows that the protective atmosphere in the tin bath diffuses into the annealing lehr. However, the annealing lehr does not effectively discharge it (particularly H₂). Thus, roller HE occurs. Opening the vent decreases the H₂ concentration around the roller. In addition, the vent is moved by ∼1 m in the original position toward the exit of the annealing lehr, which is most conducive to H₂ discharge. This optimization measure reduces or eliminates the spot defect caused by the HE of the roller. Moreover, it has great application potential in the design of float glass annealing lehr.