Compared with blast furnace slag, the former has high iron oxide content, and the original Al2O3-SiC-C type iron groove refractory material is seriously eroded in the slag line. Therefore, the material is changed in the slag line, the size of the molten iron groove is expanded in the desiliconizing agent, and the forced air-cooling tube is buried in the side wall of the iron groove. The desiliconized slag of the high iron oxide is eroded due to oxidation of SiC and C. It can be replaced by Al2O3-MgO refractory material, and the corrosion resistance mainly depends on the amount of liquid phase formed by the slagging reaction. The experiment confirmed that when MgO/Al2O3>1, the formation of the liquid phase was inhibited because the reaction of FeO with Al2O3-MgO in the desiliconized slag produced high-melting minerals.
What are the disadvantages of sintered refractory oxide products?
It is generally believed that the thermomechanical damage of the sintered refractory oxide product is mainly caused by microcracks, and the generation and growth of the microcracks depend on physical strengths such as strength, elastic modulus, thermal conductivity, and linear expansion coefficient of the product. For sintered products, the higher the high temperature strength, the smaller the factors that inhibit crack generation, the existing microcracks tend to grow, the fracture toughness is poor, and the cracks are easily broken at high temperatures. High-temperature fired refractory products such as burnt magnesia bricks, the key weakness of the burnt magnesia chrome bricks is that the thermal shock resistance is poor, and the defects of the slag are easily absorbed.
How is the aggregate size of the electric furnace spray feed determined?
Under the premise of determining the material and the binder, it is essential to produce a high-quality spray material, and the particle size ratio of the aggregate is essential. The critical particle size is large, and the corrosion resistance is good, but the fluidity is poor and the rebound rate is high in the spray filling operation.
The critical particle of the semi-dry spray is usually 3 mm.
The particle size of the flame spray is usually smaller than the semi-dry method, preferably 0.5 to 0.05 mm. Particle grading has evolved from early second and third grade ingredients to multi-stage ingredients. Japan Nippon Steel recently studied the alkaline flame spray material and considered that the aggregate particles are spherical. It has smaller specific surface area, stronger hydration resistance and good fluidity during spraying. In order to improve the fluidity of the spray material, reduce the dust, improve the working environment, and improve the adhesion rate, foreign countries have developed from the original crushed aggregate particles to the particles plus additives and binders (organic or inorganic), premixed, sprayed Dry secondary granulation. The granular binder is replaced by granular polyphosphate or superphosphate to improve the problem of moisture absorption and agglomeration during storage. In order to solve the problem of hydration and oxidation of carbon-containing alkaline spray materials, alkaline aggregate granules and graphite water immersion treatment technology have developed rapidly.
What refractory materials are used for pre-desiliconization of hot metal?
Compared with blast furnace slag, the former has high iron oxide content, and the original Al2O3-SiC-C type iron groove refractory material is seriously eroded in the slag line. Therefore, the material is changed in the slag line, the size of the molten iron groove is expanded in the desiliconizing agent, and the forced air-cooling tube is buried in the side wall of the iron groove. The desiliconized slag of the high iron oxide is eroded due to oxidation of SiC and C. It can be replaced by Al2O3-MgO refractory material, and the corrosion resistance mainly depends on the amount of liquid phase formed by the slagging reaction. The experiment confirmed that when MgO/Al2O3>1, the formation of the liquid phase was inhibited because the reaction of FeO with Al2O3-MgO in the desiliconized slag produced high-melting minerals.
What are the disadvantages of sintered refractory oxide products?
It is generally believed that the thermomechanical damage of the sintered refractory oxide product is mainly caused by microcracks, and the generation and growth of the microcracks depend on physical strengths such as strength, elastic modulus, thermal conductivity, and linear expansion coefficient of the product. For sintered products, the higher the high temperature strength, the smaller the factors that inhibit crack generation, the existing microcracks tend to grow, the fracture toughness is poor, and the cracks are easily broken at high temperatures. High-temperature fired refractory products such as burnt magnesia bricks, the key weakness of the burnt magnesia chrome bricks is that the thermal shock resistance is poor, and the defects of the slag are easily absorbed.
How is the aggregate size of the electric furnace spray feed determined?
Under the premise of determining the material and the binder, it is essential to produce a high-quality spray material, and the particle size ratio of the aggregate is essential. The critical particle size is large, and the corrosion resistance is good, but the fluidity is poor and the rebound rate is high in the spray filling operation.
The critical particle of the semi-dry spray is usually 3 mm.
The particle size of the flame spray is usually smaller than the semi-dry method, preferably 0.5 to 0.05 mm. Particle grading has evolved from early second and third grade ingredients to multi-stage ingredients. Japan Nippon Steel recently studied the alkaline flame spray material and considered that the aggregate particles are spherical. It has smaller specific surface area, stronger hydration resistance and good fluidity during spraying. In order to improve the fluidity of the spray material, reduce the dust, improve the working environment, and improve the adhesion rate, foreign countries have developed from the original crushed aggregate particles to the particles plus additives and binders (organic or inorganic), premixed, sprayed Dry secondary granulation. The granular binder is replaced by granular polyphosphate or superphosphate to improve the problem of moisture absorption and agglomeration during storage. In order to solve the problem of hydration and oxidation of carbon-containing alkaline spray materials, alkaline aggregate granules and graphite water immersion treatment technology have developed rapidly.
What are the refractory materials for the blown air supply components at the bottom of the electric furnace?
The requirements for refractory materials for electric bottom blowing air supply components are as follows.
1 Ultra-high power electric furnace ventilation bricks should have good air permeability during use. After steel forming, the ventilation function must be restored within 1~2 times after re-use.
2 The gas supply element is in contact with the molten steel at a high temperature above 1630 ° C, and is washed by the high-speed stirring molten steel, and the material is required to have sufficient strength and high temperature mechanical properties.
3 The electric furnace is intermittent operation. The temperature difference caused by repeated heating and cooling changes greatly. The thermal stress inside the material causes spalling. The material is required to have good thermal shock resistance and peeling resistance.
The contact type (direct agitation) device is made of a refractory material, which is composed of a nozzle (stainless steel tube) and a magnesium carbonaceous material (magnesium carbon brick), and is ventilated in the center of the furnace bottom. The composition of the bottom-blown refractory material is filled between the nozzle and the pipe brick, and between the pipe brick and the magnesia block, with magnesia castable, and the bottom of the furnace is made of amorphous magnesium dry meal.
The non-contact (indirect agitation) device uses a refractory material and is ventilated to beat the hearth. The refractory material of the furnace bottom must have the following properties: the gas permeability of the beating layer should be maintained for a long time, even if it is at a high temperature, the sintered layer must be thin and maintain good gas permeability, and the purity of the raw material is high; the gas permeable layer should have good Stability, if small cracks are generated, will affect the uniformity of gas permeability; the gas permeable layer must also have high thermal shock resistance.
What refractory materials are used to adapt to the development of new continuous casting technology?
(1) Refractory for horizontal continuous casting
The development of horizontal continuous casting determines the performance of the separation ring between the tundish and the crystallizer, which directly affects the production capacity of the horizontal continuous casting machine. At home and abroad, a large number of studies have been carried out on the material of the separation ring for horizontal continuous casting, and fused silica, high alumina, Zr〇2, Si3N4, BN, Si3N4-BN and Sialon separation rings have been developed.
(2) Refractory for thin slab continuous casting
Thin slab continuous casting has special requirements for the immersion nozzle because of the small space of the crystallizer, so a special shape thin wall immersion nozzle has been developed. The immersion nozzle is made of high alumina carbon refractory containing boron nitride (BN) and zirconia (Zr02).