4 indicators that determine the high temperature performance of refractory materials

 During use, refractory materials are subject to physical, chemical, and mechanical effects at high temperatures (usually 1000~1800C), which are easy to melt and soften, or are corroded, abraded, or cracked and damaged, causing the operation to be interrupted and stained contaminated materials.

The following are 4 indicators that determine the high temperature performance of refractory materials:

(1)Refractoriness .

Refractoriness refers to the temperature at which a material reaches a certain degree of softening under the action of high temperature, which characterizes the performance of the material against high temperature. Refractoriness is the basis for judging whether a material can be used as a refractory material. The International Organization for Standardization stipulates that inorganic non-metallic materials with a refractoriness above 1500°C are refractory materials. It is different from the melting point of the material, and it is a comprehensive performance of a mixture of multiphase solids composed of various minerals.

(2) Deformation temperature under high temperature load.

It also known as the refractory softening point under load or the refractory deformation temperature under load, it means the resistance of the refractory to the combined action of high temperature and load under a constant load or the temperature range in which the refractory exhibits significant plastic deformation. The maximum use temperature of the refractory material can be inferred from its softening temperature under load.?

(3) High temperature volume stability of refractories.

Refractory materials produce volume expansion under the action of high temperature for a long time, which is called residual expansion. The size of the residual expansion (deformation) of refractory materials reflects the quality of high-temperature volume stability. The smaller the residual deformation, the better the volume stability; on the contrary, the worse the volume stability, the easier it is to cause deformation or damage to the masonry.

(4) Thermal shock stability.

The ability of refractory materials to resist sudden changes in temperature without being damaged is called thermal shock stability. This performance is also called thermal shock resistance or temperature sudden change resistance. Generally speaking, the greater the linear expansion rate of the material, the worse the thermal shock stability; The higher the thermal conductivity of the material, the better the thermal shock stability. In addition, the structure of the refractory material, the particle composition and the shape of the material all have an impact on the thermal shock stability.

Article Source：4 indicators that determine the high temperature performance of refractory materials
Company name: Henan Changxing Refractory Materials Co.,Ltd
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The importance of porosity to refractory castables

 The ratio of the volume of pores in a material to the total volume of the material can be divided into true porosity, closed porosity and apparent porosity. It is usually called apparent porosity in the refractory industry in my country. The pores in refractory materials can be roughly divided into three categories: closed pores, open pores, and through pores. Generally, the above three types of pores are combined into two types, namely, open pores (including through pores) and closed pores. The apparent porosity refers to the volume density of all open pores in the material, which is the ratio of the dry mass of the refractory material to its total volume (the sum of the volume of solid, open pores and closed pores), that is, the mass per unit volume of the material use g/cm3 or kg/m3 said.

The bulk density of dense shaped refractory products should be determined according to the national standard GB/T2997-2000. The bulk density of shaped heat-insulating refractory products shall be determined according to the national standard GB/T2998-2001. The bulk density of dense refractory castables should be measured according to YB/T5200-1993.

Porosity is the basic technical index of most refractory materials. It almost affects all properties of refractory products, especially strength, thermal conductivity, corrosion resistance, and thermal shock resistance. Generally speaking, the porosity increases, the strength decreases, the thermal conductivity decreases, and the corrosion resistance decreases. Refractory castable is an unshaped refractory made of granular and powdered refractory materials according to a certain composition, plus a certain amount of binder and water, and formed by stirring and vibration casting. It is widely used in metallurgy, glass, cement, petrochemical, High-temperature industries such as energy.

Refractory castables will inevitably produce pores in the dehydration and sintering stages of the molding and heat treatment process. According to statistics, in the dense refractory castable, the matrix accounts for 25% of the total volume of the castable, and the pores account for about 10% of the total volume of the matrix. It can be seen that the pores are an important part of the matrix microstructure. The pore structure parameters include a very rich content, such as porosity, pore shape and distribution, pore size and pore size distribution, pore volume, etc. They all determine the mechanical and thermal properties of refractory castables to a large extent.

Article Source：The importance of porosity to refractory castables
Company name: Henan Changxing Refractory Materials Co.,Ltd
More refractory products: https://www.cxrefractories.com/en-product-solution
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Processing of steel scrap

The processing of steel scrap differs from different kind of refractory material quality and shapes. Breakable and irregular shape lumps can be broken by the hammering of heavy punch, Extra thick and extra long scraps should be cut into proper sizes by flame cutter. The scraps with even larger sizes can be broken with blasting method. Thick waste steel plate and merchant steel should be cut with shearing machine. Light scraps with small volume weight like offcut of light sheets, steel wire, waste car shell, should be compressed to blocks with packer and then bundled. The steel cuttings produced by cutting should be compressed to blocks by briquetting machine after deoiling. Scraps mixed with other kind of metals ashould be broken, then get steel scrap with magnetic separation. A new technique of breaking under -50～-100℃ low temperature with the help of liquid nitrogen has been developed in recent years, but the problem of separating steel scrap and nonferrous metal and other impurities was not completed solved. The use of mixed scraps should be kept within a certain portion to avoid affecting the quality of steel.

Magnetic separation
Magnetic separation is to use the magnetism difference between the different material in solid waste to separate with inhomogeneous magneto, it is the most effective method in separating ferrous metals. After solid waste is put into magnetic separator, magnetic particles will be magnetized under the effect of inhomogeneous magneto, and then sucked into the cylinder by the force of magnetic field, then discharged. Non-magnetic particles stay in. The magnetic sources adopted in magnetic separation are usually electromagnet and permanent magnet.

Cleaning
It is to use different kind of chemical solvents or hot surface active agent to clean up the greasy dirt, rust and sidiment on the surface of scrap. Usually used for generators, bearings, gears that are polluted by grease, lubricant, oil, etc.

Preheating
Scraps are usually polluted by oil, lubricating grease, etc., the oil and lubricating grease which are unable to evaporate immediately could pollute the molten metal. For open storage scaps, after affected by moisture, as it contains moisture and other easily vaporized material like lubricating grease, it could expand under high temperature in furnaces. Therefore, it should be preheated with flames to remove the moisture and grease, then put into furnaces.

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Article Source:Processing of steel scrap
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