In a broad sense, the self-explosion of tempered glass is generally defined as the phenomenon that tempered glass automatically explodes without direct external force. In fact, automatic bursting during the tempering process and self-explosion during storage, transportation, and use are two completely different concepts, and the two cannot be confused.
1. Self-explosion during the production of tempered glass
The spontaneous explosion of tempered glass in the production process is generally caused by the inclusions such as sand particles and bubbles in the glass, as well as process defects such as notches, scratches, edge bursts, and unreasonable tempering caused by cold working. For glass bursting during processing, the following measures should be taken:
1) Choose high-quality original glass sheets: Original glass sheets are crucial for the quality of the tempered glass finished glass to burst in the furnace. If the glass contains bubbles, stones, cold cracks and excessive surface scratches, it will cause stress concentration during the heat treatment process, which will easily break. However, the above-mentioned defects may also occur when the float glass production line is unstable, and the quality inspection of each piece of original glass should be done carefully.
2) Pay attention to the pretreatment method: When cutting the glass, you should choose the right angle cutter wheel and apply pressure to make the upper crack band of the glass section very narrow, and the lower mirror surface is wider, so as to obtain a good cut and reduce edge cracks. There will be micro-cracks on the edge of the glass after cutting. Use polished or fine-grinded edges as much as possible before tempering to reduce the existence of glass micro-cracks and the impact on later use. Use rounded corners as much as possible for the corners to reduce stress concentration during the tempering process. Generally, glass with a thickness of ≥8mm requires fine edging, and glass with a thickness of ≤6mm can be edged with a wet abrasive belt edging machine.
3) Reasonable setting of furnace temperature: From the analysis of glass heating and internal stress changes, the dramatic change in temperature is the main external factor that causes the glass furnace to burst. The higher the temperature, the greater the temperature gradient in the thickness direction of the glass, the greater the internal stress, and the higher the probability of glass bursting. 12mm, 15mm, and 19mm thick glass is more dangerous. Therefore, it is not advisable to use too high a temperature within the tempering temperature range.
4) Set the conveying speed reasonably: When the glass is fed into the tempering furnace from the loading table, the front end of the glass enters the furnace first and is heated and expanded, while the rear end of the glass outside the furnace is colder. The temperature difference generated in the plane direction at the junction of cold and hot causes tensile stress at the cold end and compressive stress at the hot end. The faster the conveying speed, the smaller this temperature difference. However, if the conveying speed is increased, the glass will be in a high temperature quickly, and the thermal shock will increase, that is, the temperature gradient in the thickness direction will increase relatively, and the probability of bursting in the glass furnace will increase accordingly. Therefore, it is necessary to weigh the pros and cons in actual production and then choose a reasonable conveying speed. Use a slower speed for thicker glass.
2. Self-explosion during the use of tempered glass
During the handling, storage, installation, and use of tempered glass after production, a small number of products will suddenly break. Self-detonation can occur in the factory warehouse and within a few years after leaving the factory. From time to time, I have seen reports about the self-explosion of tempered glass products such as glass countertops, shower rooms, industrial and mining lamps glass, oven door glass, and glass curtain walls.
