Glass Lining Enamel Instructions For Reactor
l Enamel slip preparation:
1, Ground coat:
Preparation: Calculate the amount of water added according to the ratio of ground coat powder: deionized water = 100: 40 (weight ratio). Weigh the water first, then add the weighed powder to the water. Stir for 8-16 hours after soaking, and add 0%-5% of water according to the practice. After mixing evenly, sieve it trough 30-40 mesh, then it’s ready for coating.
Before use, you can also add 0.1-0.3% (mass ratio) concentration of 50% sodium nitrite aqueous solution to increase viscosity, increase spray thickness, it according to the actual situation.
2, Cover coat:
Use with alcohol: In order to improve the suspension performance of the enamel slip, and to make the wet enamel sprayed on the surface of the workpiece dry quickly. When preparing the slip, you can add an appropriate amount of industrial alcohol (the total amount of water and alcohol accounts for 40-50% of the cover coat powder, and the ratio of water and alcohol is recommended to be 2:1). Adjust accordingly according to climate temperature or depends on factory experience. Weigh the water and alcohol first, then add the weighed powder to the liquid and soak for about 30 minutes, and stir evenly. Note that the stirring speed should not be too fast to avoid delamination of the enamel slip. After mixing well, sieve it trough 30-40 mesh, then it’s ready for coating.
l Spaying:
Normally, Hot spray(spray cover coat while ground coat is still hot, at 80-90℃) is used in south area. Enamel powder need to be relatively finer, the suspension property of enamel slip better.
Cold spray(spray cover coat while ground coat is cooled) is often used in north area, enamel powder is thicker, the suspension property of enamel slip is not better than hot spray, easily precipitated.
l Firing
1, Ground coat:
Before firing, it should be checked to ensure that the workpiece is dry. The surface of the ground coat layer should be uniform in thickness, without flow stains and cracks. Before entering the furnace, blow the surface of the workpiece with an air gun. Remove any impurities that may be present.
It is recommended that the firing temperature of the ground coat be 920-940 ℃ (the firing temperature of the ground coat in summer is 20℃ lower than that in winter), and the duration of heat preservation and firing time depends on the size of the work piece of the electric furnace power. When the workpiece is released, make sure that the ground coat is well firied, there must be no over burning or Insufficient burning.
The thickness of the ground coat is recommended: 0.20-0.30mm at the flat plane, 0.20-0.25mm at the hook face.
2, Cover coat:
Before firing, it should be checked to ensure that the workpiece is dry. The surface of the ground coat layer should be uniform in thickness, without flow stains and cracks. Before entering the furnace, blow the surface of the workpiece with an air gun. Remove any impurities that may be present.
It is recommended that the firing temperature of the cover coat at the first time is 60-80 ° C lower than the firing temperature of the ground coat, and the temperature on the second time and the third time should be reduced by 20 ° C each time.
|
Firing times |
Firing temperature |
Remarks |
|
Ground coat(one time) |
920℃-940℃ |
|
|
Cover coat (first time) |
870℃ |
Temperature lower 60-80℃ than ground coat |
|
Cover coat (second time) |
860℃ |
|
|
Cover coat (third time) |
840℃ |
|
|
Cover coat (fourth time) |
820℃ |
min 780℃ |
The minimum firing temperature of cover coat is 780℃. The heat preservation time depends on the size of the electric furnace power. The surface of the enamel layer should be bright and shiny when the workpiece is released, as the follow picture showed:
Cover coat thickness recommendation: 0.25-0.3mm at flat plane on each cover coat coated, 0.2-0.25mm at hook face.