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Ceramic tile, also known as vitrified brick or homogeneous brick, has the advantages of high strength, good wear resistance, and can be randomly matched color. These aspects are better than similar competitive products on the market, so it has been widely promoted. However, in the production process due to improper production technology, production operation and quality management, color difference will affect the quality of products. Before using color difference meter to detect color difference, we need to understand: What is the cause of tile color difference?

1. Impact of raw materials

Fluctuation of raw material composition produces 1 type color difference.

(1) It is well known that the chemical composition of raw materials is unstable, especially the change in the content of colored ions Fe and Ti, which causes the obvious change in the whiteness of the bad body. Low Fe content, good appearance; On the contrary, the appearance of red to dark, green.

(2) From the raw material particle analysis, clay contains fine grained quartz, feldspar residual sand, etc., can not pass the ten thousand hole screen. Its high content will change the content of Ca, Mg, Na and affect the sintering temperature. To change the color of the brick.

(3) From the point of view of the burning loss of raw materials, the content of carbonate and sulfate in raw materials is high, the burning loss is large, and the color points on the brick surface are easily shaped.

2. Influence of ingredients

The accuracy of the batching system is not high or man-made batching is not accurate, and it is easy to produce two kinds of color difference I and II.

(1) In the early stage of production, the batching system has been adjusted, the batching precision is good, the time is long, the system will produce mechanical fatigue and affect the batching amount, thus affecting the fluctuation of raw material ingredients, so that different batches of bricks have different colors.

(2) Due to improper operation, the fluctuation of mud composition produced by different grinding times also affects the color of brick.

3. Mud performance impact

Mud performance control is not stable, can produce I, II, III color difference.

(1) mud specific gravity is different, its moisture, viscosity will change. The proportion is too large, the corresponding water is less, the viscosity is high, the pipeline resistance is large; On the contrary, the proportion is too small, the water is large, the viscosity is low, the mud is easy to precipitate, so that different batches, the same batch or even the same piece of brick bad powder particles distribution uneven and produce color difference.

(2) screen allowance control on the high side, high firing temperature, low degree of brick porcelain: screen allowance on the low side, lower firing temperature, good degree of brick porcelain, so that the brick color is different.

(3) The discontinuity of iron removal in the slurry discharge and mud transport process will make the iron content of the material fluctuate most. Iron content high color difference. Low iron content is good in color.

4. Spray dry granulation

The unstable properties of powder particles are easy to produce two kinds of color difference: Ⅱ and Ⅲ.

(1) Powder particles, especially color particles, should be controlled well. If the overall particle of the color material is coarse, the color is poor; The whole particle is fine, its color is good. Uneven thickness, color is inconsistent.

(2) The gradation of the color material and the base material is inconsistent, and the fluidity is different, so that the coarse particles are blanked, so that the center of the brick and the surrounding area appear obvious color difference.

(3) The uneven moisture of the powder, so that the dry base contained in the same quality powder is different, and its liquidity is different, leading to the dividing phenomenon, will affect the color of the brick.

(4) powder weighing is not allowed, especially the proportion fluctuation of base material and color material or the uneven mixing of the mixer will make the color difference of the brick is obvious.

5. Influence of pressing and forming

The press forming process mainly produces class Ⅱ color difference and class Ⅲ color difference.

(1) The molding pressure of the press, especially the maximum pressure change, will affect the density fluctuation caused by bad production. High pressure, good density, good finish, uniform color after burning; On the contrary, the maximum pressure is small, resulting in poor density, rough green surface, brick color difference.

(2) The change of green thickness will also cause the color difference of brick. The thickness is too large, it is difficult to burn, and the porcelain degree of brick is reduced. Small thickness, easy to burn, porcelain degree is good, both color is different.

(3) uneven sowing of the feeder will also lead to color difference.

6. Glaze effect

Porcelain bricks are often coated with a thin layer of transparent glaze. The properties of the glaze paste and the amount of glaze applied are different, and the color difference produced is similar to the properties of the blank, sometimes even obvious. However, the mature temperature of glaze should match the firing temperature of billet, otherwise it will produce serious poor glaze color and even matt phenomenon.

7. Furnace firing effect

The kiln firing process will produce I, II, Ⅲ class color difference, it is the most important reason for the color difference in the production process of porcelain brick, should be strictly well burned.

(1) The temperature difference of the kiln, first of all, the maximum firing temperature change, will make the brick appear obvious color difference. Different batches, the same batch is possible; Secondly, the transverse temperature difference will make the five bricks of the same discharge kiln different colors.

(2) The change of firing cycle will make the color of products produced in different batches different. The cycle is too long, there is overburning, the cycle is too short, there is underburning and even raw burning.

(3) The fluctuation of kiln pressure will change the original setting of the firing system, so that the length of the pre-tropical zone, firing zone and cooling zone will change and affect the firing, resulting in color difference.

(4) The change of atmosphere. Porcelain tiles are normally fired in an oxidizing atmosphere. If the air supply volume of the combustion air and the air extraction volume of the kiln fan change, it is possible to cause the reducing atmosphere to burn, which will make the brick surface dark or blue, so that different products of the same batch are different in color.

(5) The opening and killing of the burner are different, which will also cause the change of the kiln firing system and produce color difference.