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3 reasons why refractory bricks can be fire resistant

2020-03-03

 Refractory brick is an inorganic non-metallic material with a fire resistance of not less than 1580 ° C. It is a basic material serving high-temperature technology. It is a structural material for masonry furnaces and other thermal equipment. Functional Materials. The successful use of refractory bricks under high temperature must have good structure, thermal properties, mechanical properties and use properties, that is, high fire resistance, load softening temperature, thermal shock resistance, and chemical corrosion resistance. Withstand various physical and chemical changes to meet the requirements of the use of thermal equipment and components.

 

Then there is a question, why can refractory bricks withstand high temperatures? Why can't other materials withstand high temperatures? What material is it made from? Our company Zhengzhou Tianyang Refractories will explain three reasons why refractory bricks are resistant to high temperatures:

 

 

First from raw material analysis

 

The raw materials used in the production of refractory bricks are generally natural ores, such as bauxite, silica, magnesite and other raw materials, which are manufactured by processing different types of refractory bricks.

When using bauxite as the raw material, the main component of alumina-silica refractory bricks is alumina, which is a hydrated alumina containing impurities. It is a clay mineral, insoluble in water, soluble in sulfuric acid and sodium hydroxide. Solution. It is mainly used for smelting aluminum and making refractory materials, because high bauxite clinker has a fire resistance of up to 1780 ° C, strong chemical stability and good physical properties. Purifying bauxite at high temperature to produce a main crystal phase of corundum with alumina content greater than 90% can produce ultra-high temperature refractory bricks, fused zirconium corundum bricks.

 

 

2 belongs to inorganic non-metal materials

 

Inorganic non-metallic materials are combined with organic polymer materials and metallic materials as three major materials. The characteristics of ordinary inorganic metal-dividing materials are: high compressive strength, high hardness, high temperature resistance, corrosion resistance. In addition, ceramics are resistant to corrosion and refractory materials. Both thermal and thermal insulation properties have their excellent characteristics. These are incomparable to metal materials and polymer materials. But compared with metal materials, it has a low breaking strength and lacks ductility. Compared with high-molecular materials, the manufacturing process is greater.

 

Three: forming and sintering

 

The production process of refractory bricks is through the process of mineral crushing-raw material mixing-mechanism molding-high temperature firing. Finally, a high temperature resistant product is produced. The sintering temperature of the green body in the high temperature tunnel kiln will be higher than the load of the product The softening temperature is generally above 1500 ° C. Fire resistance is above 1770 ° C. Good high temperature resistance. Refractory bricks are mainly used for lining of furnaces such as steelmaking electric furnaces, glass melting furnaces, and cement rotary furnaces.

 

In summary, the three reasons why refractory bricks can withstand high temperatures are mainly based on: The refractory bricks use high raw material minerals. As an inorganic non-metal material, the level of its use is determined from the level of the raw material. The finished body passes through a high temperature of 1500 in a high-temperature tunnel kiln, so the refractory brick can withstand high temperatures and is suitable for high-temperature kiln linings. Website 2

 

Analysis of common glass mold materials

 

Glass mold is an indispensable equipment in glass molding. The quality and output of glass production are directly related to the mold.

 

Common glass mold materials:

 

1. Ordinary low alloy cast iron

 

Cast iron has been widely used as a mold material since the 19th century. Cast iron has excellent casting properties, good processability, low cost, heat and non-stick properties, and is suitable for small and medium-sized foundries. Currently, cast iron is widely used at home and abroad. Glass mold material, alloy cast iron will remain the main glass mold material in the foreseeable future.

 

2. Ductile and vermicular graphite cast iron

 

Ductile iron has higher strength and toughness, and has good oxidation resistance. Its thermal fatigue resistance is better than other cast irons. However, because of its graphite shape, it is isolated and spherical, and its thermal conductivity is poor. It cannot meet the requirements of mechanized production. Because of its use in glass molds, most factories only use it to make small bottle molds.

 

Compacted graphite cast iron has similar mechanical properties to nodular cast iron, has high thermal conductivity, oxidation resistance and growth resistance, and has good casting properties and machining properties like gray cast iron. It makes compacted graphite cast iron have good comprehensive properties for use. For manufacturing glass mold materials.

 

3.D type graphite cast iron

 

D-type graphite is a kind of flake graphite. It is grown between austenite dendrites. The continuity of austenite cuts the continuity of graphite flakes, and the gap between D-type graphite and matrix is ​​more The gap between the substrates is small. The shape of D-type graphite is small, curled, and the end is blunt, which determines that it has a small cutting effect on the substrate and is not easy to cause large stress concentration. Therefore, D-type graphite cast iron has higher strength.

 

At present, D-graphite cast iron has become a hotspot as a glass mold material, and there have been many studies at home and abroad. Analysis of molds imported from abroad shows that most of them use D-graphite cast iron. It is usually obtained by adding elemental titanium and adopting a metal type to obtain D-type graphite.

 

4.Alloy steel

 

In recent years, alloy steel molds have begun to be used, and in most cases alloy steel can better meet the requirements for glass molds than cast iron. The thermal conductivity of steel is inferior to that of cast iron, which is prone to overheating and adhesion when used. Therefore, methods such as forced cooling, proper mold structure design, and silicone grease lubrication must be used.

 

Stainless steel is a material that is resistant to corrosion, high strength, oxidation resistance and toughness. It has poor thermal conductivity, low thermal expansion, and a variety of components. Britain has long been used to make punches and linings. The United States uses AISI430 (12-14Cr) and AISI310 (25Cr, 20Ni) stainless steel for making certain mold parts.

 

5. Nickel-based alloy

 

This type of alloy has better heat resistance than cast iron, so the molds made with it have fewer surface cracks, long life, high productivity, and can improve the smoothness of glass products, but these materials are expensive. In order to improve the surface finish of glass products or extend the replacement cycle of mold parts, such materials are still commonly used for mold making.

 

6. Copper-based alloy

 

This type of alloy has good thermal conductivity and can still guarantee the quality of glass products during high-speed forming, so it has attracted much attention. There are mainly two types: one contains Cu, Al, Zn, and Ni. This type of alloy is most effective in improving the surface finish. This alloy has good oxidation resistance, thermal conductivity, thermal stability, and thermoplasticity, which significantly improves the molding machine. Operating conditions. The other type contains Cu, Al, Ni, and Co, and does not contain Zn. Compared with cast iron, it can increase the machine speed by 15-25, can extend the life of the mold working surface by about three times, the mold is easy to repair, and the product quality is good.

 

7. Mold coating

At present, thermal spray coating is often used on the corners of the glass mold and the part where the punch is in contact with the glass, and a layer of nickel-chromium alloy powder is spray-welded to improve the high-temperature wear resistance, high temperature resistance, and oxidation resistance of the contact surface. Glass molds made of gray cast iron and thermal spraying of nickel-based self-fluxing alloys can increase the mold life by more than 5 times. The main problems are the need for re-processing and higher mold costs. 

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