What is thermally toughened safety glass?
Thermally toughened safety glass is a heat-treated glass which we can produce in either flat or curved form. It has the following important characteristic:
- About 3 times higher resistance to mechanical shocks compared to non-toughened glass
- About 3 times increased thermal resistance characteristics compared to normal glass
- Safety glass, i. e. in case of breakage, it decays into small blunt fragments, then reducing the risk of injuy.
Process of Tempering
During the process of thermal toughening, a readily cut and treated glass sheet is heated up to approx. 650° C and then quickly cooled down by means of cold air. The inner part of the glass cools down more slowly than the external surface. The inner part still contracts when the surfaces of the glass have already solidified. A compressive stress develops at the surface of the glass, in the inner glass there is a tensile stress. Thermally toughened safety glass cannot be treated further after the toughening process.
We use the following glass types as our basis material:
- float glass
- coloured glass
- cast glass
- coated glass
Fields of application
Which aspects have to be considered when using thermally toughened safety glass?
- The linear heat expansion coefficient is 9 x 10-6 K-1. A rule of thumb: An increase of temperature by100°C causes an expansion of approx. 1,0 mm/m
- When installing thermally toughened safety glass direct contact with metal is to be avoided because "heat bridges" can develop. In order to balance the unevenness of the supporting surface and the different heat expansion coefficients please use soft rubber.
- Principally, the following minimum distances are to be respected when planning the positioning of the holes:
a) Glass edge to edge of hole = double glass thickness
b) Edge of hole to edge of hole = double glass thickness
c) Holes at the corner: Should one of the distances between edge of the hole toone glass edge be less than 35 mm, so the difference of the distances to theedges has to be at least 5 mm.
- The diameter of the hole has to be at least the thickness of the glass!
- The glass sheet principally has to be installed in a way that the load / stress is distributed equally. Screws and fixings must not load the glass punctually. The screwing is to be done "crosswise".
- Cuts into the glass need to have a radius equal to or bigger than the thickness of the glass.
- Non-observance of these rules leads to a lesser strength of the glass! We principally examine every single case if the glass with the requested treatment can be thermally toughened.
We mainly produce according to your individual requests.
We produce our thermally toughened safety glass in dimensions between Dia:10 mm and 1000x800 mm in thicknesses of 3, 4, 5, 6, 8, 10, 12, 15, 19 and 25 mm. The maximum weight of each sheet is 200 kg.
We cut our glass on round and form cutting machines as well as on CNC-cutting tables. The minimum cut size is diameter 10 mm.
For the production of thermally toughened safety glass, the minimum requirement of edge finishing is an arrissed edge. In many cases, however, we recommend a ground edge due to stability reasons. The edge finishing is made on round and form grinding machines, double edgers as well as on CNC-working units. Our standard edge finishing is the C-edge (= pencil edge). On request, we can also produce other edge forms such as straight edge with arriss, bevelled edge and facets.On basis of ground edge,we make farther machining to provide polished edge, which is the best finish of edge.In this way, you can see throught from the side of glass.
The holes in the glass are produced with tolerances different from those known of metal working due to the characteristics of the material glass. Glass is first slightly drilled from the bottom and then drilled through the complete glass from the top with a hollow diamond drill. Holes are generally available in diameters of 4 to 240 mm. Bigger hole diameters and inner edge treatment such as polishing are possible on request.
We make decoration of the glass surface by silk screen printing with ceramic colours. The colour is first applied to the glass surface, dried up and finally, during the process of thermal toughening, it melts with the glass so that a decoration which is resistant to scratches is produced. Apart from ceramic colours, organic glass colours may be used.
Corundum is blown on the glass surface with a fan. The sandblasting can be made completely or partially onto the glass surface.
Apart from these standard treatments, please inform us about your requirements. We will be pleased to find a solution for your ideas.
As our standard, we pack in between glasses with white paper. We can deliver you reusable or non-reusable transport packaging which is subject to agreement. Furthermore, individual packing solutions are possible.
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