Estimation on Glass Shaping Mold in Reducing Atmosphere

Molds were estimated by using 4 kinds of molds and 4 kinds of pure metals for soda-lime-silica glasses (colorless and amber container glasses) below 900°C in reducing atmosphere. The estimation was based on sessile drop measurement and observation of metal surfaces. The sessile drop measurement showed wettability by measuring the contact angle and interfacial diameter between glass and metal. Copper and copper alloy showed poor wettability, and their surface roughness increased. Iron showed good wettability and roughening of its surface. In metals except copper, grain boundary development and surface film formation were observed after heating. The contact angle on nickel was determined as a function of roughness, and the following empirical formula was obtained. θr=26.4r2+18.6r+77.1 θr: contact angle (degree) r: surface roughness (μm) These results suggested that the wettability and the surface roughness, owing to the reacted materials, crystal growth and kind of metals, are the essential factors for glass shaping molds.