| abstract |
The invention relates to a heavy metal-free and fluoride-free cover enamel composition, which is suitable for the production of enamelled steel and boiler plates and generally geometrical parts. The enamel has a thermal expansion coefficient which is in the temperature range from 20 ° C to 400 ° C in the range from 9.5 x 10 -6 K -1 to 11 x 10 -6 K -1 . The composition range of the enamel is in% by weight 0 to 4 Li 2 O, 0 to 4 K 2 O, 9 to 15 Na 2 O, 0 to 6 CaO, 0 to 3 MgO, 55 to 75 SiO 2 , 0.5 to 3 B 2 O 3 , 0.2 Al 2 O 3 and 8 to 14 ZrO 2 . |