This article describes the use and function of refractory bricks in the steel industry.
Keywords: refractory bricks;steel
Another name for refractory brick is refractory brick. It is a refractory material made of refractory clay or other refractory raw materials. It is light yellow or brownish. It is mainly used for building smelting furnaces and can withstand high temperatures of 1580°C-1770°C. According to the preparation process It can be divided into burnt bricks, unburned bricks, electric fused bricks (fused cast bricks), refractory insulation bricks; according to shape and size, it can be divided into standard bricks, ordinary bricks, special bricks, etc.
Refractory bricks are refractory materials, a class of inorganic non-metallic materials with a refractoriness of not less than 1580°C. Refractoriness refers to the Celsius temperature at which a refractory conical sample can resist high temperature without softening and melting under the condition of no load. Refractory The material is widely used in metallurgy, chemical industry, petroleum, machinery manufacturing, silicate, power and other industrial fields. It is used in the largest amount in the metallurgical industry, accounting for 50% to 60% of the total output.
The largest user of refractory bricks is the iron and steel industry, and it is also one of the indispensable and important basic materials for the iron and steel industry. It has a great impact on steel production. Under certain conditions, it can even become the key to hinder the development of a new smelting technology. Refractory The relationship between brick and steel production is manifested in two aspects: one is to ensure the stability and economy of the steel industry process; the other is to meet the demand for steel quality and variety. In the case of low requirements for steel variety and quality Next, in order to ensure the stability of the production process and reduce costs, the long life and low cost of refractory bricks are the goals pursued by users. In the past few decades, due to the advancement of science and technology in the production and use of refractory bricks, the use of refractory bricks The service life has been greatly improved. As a result, the service life of refractory bricks is getting longer and longer, and the output is getting less and less.
Refractory brick workers are facing great confusion. Continuing to pursue long life as the only goal can no longer meet the requirements of refractory bricks themselves and all aspects of use. Refractory bricks need new development areas. In addition to pursuing the goal of longevity, refractory bricks The function of refractory bricks is also relatively single, and it is only used as a lining or component material for high-temperature containers to resist high temperature and slag erosion. The single goal and function limit the development of refractory bricks. Develop new functions to allow materials to be used under the conditions of use. Playing a multi-faceted role is the direction that should be paid attention to.
In recent years, due to the higher and higher requirements for steel quality and the production of high-quality steel such as clean steel, the reaction between refractory bricks and molten steel and the impact on steel quality have been paid attention to.
First of all, refractory bricks are required not to pollute molten steel; secondly, the research and development of refractory bricks may play a role in purifying molten steel. The development of new functions will provide new opportunities for the development of refractory bricks. The interaction between refractory bricks and molten steel generally includes The following aspects:
(1) The structure of refractory bricks is slackened after being eroded, and they are involved in molten steel under the erosion of molten steel to form non-metallic inclusions. The size of such inclusions is large and belongs to foreign inclusions.
(2) The components of refractory bricks are directly dissolved into the molten steel to increase the content of oxygen and other non-ferrous elements in the molten steel. Under certain conditions, the non-ferrous elements present in the molten steel may react with each other to form inclusions. This type of inclusion is generated inside the molten steel and belongs to self-generated inclusion. The size of this type of inclusion is generally very small.
(3) Refractory bricks are used at high temperatures. At high temperatures, more or less liquid phases are generated inside the refractory bricks. The generated liquid phase surrounds the refractory brick particles. At the same time, this liquid phase will be formed with molten steel The oxide (such as iron oxide) reacts to form a liquid phase isolation layer between the refractory brick and the molten steel, which isolates the molten metal from the refractory brick and prevents the direct dissolution of the refractory brick to the molten metal. The refractory brick and the pores in it The reaction between the gas phase and the molten metal must be carried out through this reaction layer. The structure of the molten metal is different from that of the liquid phase layer. The former is a metal structure, and the latter is an ionic structure. It is impossible for them to dissolve each other. The reaction must be accompanied by changes in the electricity price of ions. The liquid phase layer between the molten metal and the refractory brick is usually a silicate melt, and their composition and structure are very similar to slag.
The role and function of slag, this liquid layer should also have. These functions include the following aspects:
(1) The slag has oxidation and reduction properties, and the liquid phase layer between the refractory brick and the molten metal should also have oxidation and reduction properties, thereby affecting the oxygen content in the molten metal and the formation of oxide inclusions.
(2) The slag has the functions of dephosphorization and desulfurization, and the liquid phase layer should also have the functions of dephosphorization and desulfurization.
(3) Slag can absorb inclusions in molten metal, and this liquid phase should also have the effect of absorbing inclusions. In the mid-1970s, Lindskog proposed that most of the inclusions in molten steel were absorbed by refractory bricks. But many later Scholars have focused their attention on the adsorption of slag to inclusions, ignoring the role of refractory bricks. According to metallurgical principles, slag absorption of inclusions should meet two conditions: one is that inclusions must be in contact with slag. In molten steel, inclusions The density is smaller than that of steel, and they can float up to the slag-steel interface and contact with slag; the second is that the adhesion work of inclusions to molten steel is greater than that of inclusions to molten steel.
The liquid phase layer between refractory bricks and molten steel should also meet the above two conditions.
First of all, during the refining process, the molten metal is often violently stirred, and the upward movement of the inclusions due to their own buoyancy has become unimportant. Its trajectory becomes very complicated, and the probability of it hitting the refractory brick is high. Moreover, in The contact area between molten steel and refractory bricks in containers such as ladles is larger than that between molten steel and slag. Therefore, the probability of inclusions touching the liquid phase of refractory bricks should be higher than that of slag.
Secondly, because the composition of the liquid phase is similar to that of slag and belongs to the ionic structure, their chemical composition is close to that of inclusions. Therefore, like slag, the adhesion work of inclusions to the liquid phase layer should be smaller than that of molten steel. It is entirely possible Adsorbs inclusions in molten steel.