20 ceramic water cup production process knowledge

1. What are the stages of porcelain firing? What is the scope of each phase? How should the firing process be controlled?

Answer: It is mainly divided into preheating stage (normal temperature ~ 300. C), oxidative decomposition stage (300 ~ 950. C), high temperature stage (950. C ~ maximum firing temperature), high fire holding stage, and cooling stage. Since there are many factors affecting the firing of ceramics, different firing systems should be determined according to specific conditions during operation, and the gas pressure in each part of the kiln should be controlled to a certain distribution through the equipment of the kiln to ensure the temperature system and atmosphere system. .

2. The function and conditions of low temperature and fast burning?

Answer:

(1) The role of low-temperature fast firing: saving energy and cost, making full use of raw material resources, improving the service life of kilns and kiln furniture, shortening the production cycle, and improving production efficiency.

(2) Conditions for fast firing at low temperature: The drying shrinkage and firing shrinkage of the blank glaze are small, the thermal expansion coefficient of the blank is small, and the change with temperature is close to a linear relationship. It is hoped that the thermal conductivity of the billet is good, and it is hoped that the billet contains a small amount of crystal transformation components. The fast-fired glaze requires strong chemical activity; reduce the water content of the billet entering the kiln, and increase the temperature of the billet entering the kiln; control the thickness, shape and size of the billet. ; Choose a kiln with small temperature difference and good heat preservation; choose kiln furniture with good thermal shock resistance.

3. A factory quickly fires ceramic plate-shaped products. It is known that the firing temperature is 1150°C and the kiln exit temperature is 180°C. The water absorption rate is allowed to be between 3-10%. During production, the appearance quality and water absorption rate of the kiln products are good, and they are stacked in the warehouse for the next day’s inspection. However, 20-30% of the products are broken after inspection. Try to analyze What caused the product to break? and come up with a solution?

Answer: The reason for the cracking of the finished product may be the poor thermal stability of the ceramic plate and the expansion of moisture absorption. Since the water absorption rate of ceramic plate products is allowed to be between 3 and 10%, its water absorption rate is within the range of water absorption rate of stoneware, plus firing The temperature is low, and the temperature out of the kiln is relatively high, which easily makes the thermal stability of ceramic products poor and cracks.

4. The basis for formulating the firing system?

Answer:

The property change of the blank components during heating,

The size and shape of the product.

(3) Glaze firing method, including the mutual influence of the base glaze reaction during firing, and enter the cooling stage after the high-fire heat preservation is completed.

Kiln.

5. In order to shorten the firing cycle of ordinary daily-use porcelain, it is planned to adopt rapid cooling at 600-400°C in the later stage of firing. Is it feasible? Why?

Answer: No, because at 573ºC, the quartz crystal form undergoes rapid conversion to a low-temperature type, and there is no liquid phase buffer, which is highly destructive and prone to deformation. If it is cooled rapidly at this stage, the product will break.

6. What are the requirements for the quality of blanks for rapid firing?

Answer:

(1) Drying shrinkage and firing shrinkage are both small.

(2) The thermal expansion coefficient of the billet should be small, and the relationship with the change of temperature is close to linear, and it will not crack during the firing process.

(3) The thermal conductivity of the billet should be good, so that the physical and chemical reactions can proceed rapidly during firing, and the thermal shock resistance of the billet can be improved.

(4) It is hoped that the blank contains less crystal transformation components, so as to avoid damage to the blank due to volume changes.

7. What technological measures can be taken to achieve rapid firing?

Answer: The blank glaze can adapt to fast firing; reduce the water content of the blank entering the kiln, increase the temperature of the blank entering the kiln; control the thickness, shape and size of the blank; choose a kiln with small temperature difference and good thermal insulation performance; choose a kiln with good heat resistance kiln furniture.

8. Briefly describe the relationship between blank formula, process factors, microstructure of porcelain body and properties of porcelain.

Answer: The chemical composition and process conditions of the billet will form different microstructures, and changes in the microstructure will affect the performance of the material.

9. How does the process affect the physical and chemical properties of the product?

Answer: The process has a great influence on the physical and chemical properties of the product, because the process will affect the microstructure of the product, and finally affect the performance of the product, so the process of ceramic production is very important to the performance of the product.

10. Briefly describe the reasons that affect the sintering of ceramic products.

Answer: There are many reasons that affect the sintering of ceramic products, mainly in the formula, the mineral composition of the raw material, the moisture content of the green body before entering the kiln, the firing atmosphere, and the firing temperature. The mineral composition of the raw material contains more volatile matter and During high-temperature reaction, more gas is generated, which affects sintering. The firing atmosphere and firing temperature directly affect the sintering of the product. If the temperature is too low or too high, it will have a greater impact on the sintering temperature. If it is not reduced in time when it is reduced to flame, the reduction effect will not be achieved. If it is reduced in advance, the oxidation will be incomplete. The formulation affects the temperature and other conditions required for sintering to a certain extent.

11. What are the main reasons for the delamination and peeling of the glaze layer? What kind of glaze layer can maximize the mechanical strength in porcelain?

Answer: It is caused by the large difference in expansion coefficient between the blank and the glaze. When glaze blank, cracking occurs, and when glaze blank, peeling occurs. In order to maximize the mechanical strength of the glaze layer, the expansion coefficients of the blank and the glaze are similar, the middle layer is well developed, and the glaze has high elasticity, high tensile strength and other properties.

12. What is the reason for the deformation of porcelain?

Answer:

The formula is a latent factor, after high temperature firing, the stress will be released.

Irrationality of device shape structure design

The molding operation is incorrect and the drying is uneven.

The operation and control of the firing process are not appropriate.

13. What are the defects of glaze and how to overcome them?

Answer: Mainly include: glaze corrugation, glaze matt, glaze shrinkage, glaze bubbles and pinholes, etc. The main ways to overcome it are: when the glaze surface is corrugated, the specific gravity of the glaze slurry can be reduced, the high-temperature viscosity of the glaze can be reduced, the temperature difference in the kiln can be reduced, and the reduction flame can be used for firing. When the glaze surface is dull, the glaze formula should be adjusted reasonably, the firing temperature of the frit should be set reasonably, the impurities brought in during ball milling can be reduced, and the reduction flame can be used for firing to shorten the high-temperature cooling time. When shrinking the glaze, the drying shrinkage of the glaze layer is reduced, and the preheating stage is slow. When glaze bubbles and pinholes, reduce the large amount of pyrolysis products contained in the raw materials, reduce the specific gravity of the glaze slurry, and avoid over-firing.

14. Causes of glaze shrinkage and methods to overcome it.

Answer: Reasons for glaze shrinkage:

(1) Glaze has poor wettability to the blank, high viscosity at high temperature, and high surface tension.

Drying shrinkage of the glaze layer

Poor adhesion of the glaze layer to the body

Long storage time of the body glaze

Overcoming methods:

(1) Reduce the content of clay, zinc oxide, and aluminum oxide.

Increase the particle size of glaze slurry and reduce the specific gravity of glaze slurry.

Increase the firing preheating period.

15. How will you adjust the expansion coefficient of the glaze when the bonding performance of the glaze deteriorates because the expansion coefficient of the glaze is too large?

Answer: The amount of sodium oxide and potassium oxide can be reduced, and can be replaced by lithium oxide. At the same time, increase the glaze firing temperature and prolong the high-temperature holding time to promote the melting of quartz. It can also be rapidly cooled to form compressive stress on the glaze surface to avoid cracking.

16. The reason for the hygroscopic expansion of ceramic wall and floor tiles.

Answer:

(1) The hygroscopic expansion of the amorphous phase is large.

(2) The firing temperature is too low, the green body is not dense enough, the structure is loose, the porosity is high, and the adaptability of the green body glaze is poor.

(3) Used in harsh environments.

(4) After the bricks are laid, the cement mortar shrinks when it sets, and the bricks absorb moisture and expand

17. What are the main factors affecting the opacification effect of opacified glaze?

Answer: Factors affecting the effect of opacified glaze:

(1) The difference in refractive index between the base glaze and the opaque phase.

(2) The size and quantity of the emulsified phase.

(3) The uniformity of the emulsion phase distribution.

(4) The thickness of the glaze layer, the thicker the glaze layer, the better the opacification effect.

18. How to improve the transmittance of transparent glaze?

Answer: The measures include:

(1) Carefully select raw materials to prevent crystallization of the glaze during firing and prevent liquid phase separation of the glaze liquid.

(2) Do not use raw materials that generate a large amount of gas at high temperatures.

(3) The initial melting point of the glaze should not be too low.

(4) Firing in a reducing atmosphere.

(5) The glaze particles are finely processed.

(6) When introducing certain components, an appropriate carrier should be selected.

19. What are the measures to improve whiteness?

Answer: The blank glaze can adapt to fast firing; reduce the water content of the blank entering the kiln, increase the temperature of the blank entering the kiln; control the thickness, shape and size of the blank; select a kiln with small temperature difference and good thermal insulation performance; select thermal shock resistance Good kiln furniture.

20. What is the adaptability of blank glaze?

Answer: Blank glaze adaptability refers to the glaze melt with good melting property, which will combine with the blank body to form a perfect whole after cooling, and the glaze surface will not crack or peel off. Factors affecting the adaptability of the glaze include: the difference in expansion coefficient of the glaze, the middle layer, the elasticity and tensile strength of the glaze, and the thickness of the glaze layer.

 
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Post time: Dec-07-2022

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