Zero-carbon and sulfur-free magnesia-based patching material promoted by crystal water and its sintering property regulation method

Abstract

The present invention relates to a zero-carbon and sulfur-free magnesia-based patching material based on the flow-promoting effect of crystal water, belonging to the technical field of refractory materials for hot patching of steelmaking converters. The product is made from the following raw materials in parts by weight: magnesite, magnesium chloride hexahydrate, strontium chloride hexahydrate, hydromagnesite and silica fume, which are mixed to form a basic patching material. The present application proposes a zero-carbon and sulfur-free magnesia-based patching material based on the flow-promoting effect of crystal water and its sintering property regulation method. After being heated, the patching material rapidly reacts to release a large amount of crystal water, and quickly forms a sol product with the silica fume particles in the system and the light-burned MgO particles in-situ decomposed from hydromagnesite. This can not only effectively bond the aggregate and matrix in the patching material, play a preliminary binding effect and improve the medium and low temperature strength of the patching material layer, but also accelerate the flow-promoting effect of the slurry on the aggregate. After the water evaporates and the sintering reaction is completed, a firm sintered layer of the patching material can be formed in the area to be patched of the furnace lining, thus achieving the purpose of quickly patching the furnace.

Description

Technical Field

[0001] The present invention relates to a zero-carbon and sulfur-free magnesia-based patching material based on promoting fluidity by crystal water and a method for regulating its sintering performance, belonging to the technical field of refractory materials for hot patching of steelmaking converters. Background Art

[0002] For a long time, magnesia-carbon hot patching materials with asphalt as the binder, also known as "black materials" and "large surface materials", have been widely used in local hot patching during various converter campaigns due to their good fluidity, strong resistance to steel slag penetration, high bonding strength between the patching layer and the original brick layer, and stable structure under thermal shock. However, with the increasing requirements of the steel industry for green environmental protection, high-efficiency steelmaking, and the cleanliness of steel quality, the disadvantages of magnesia-carbon patching materials have been gradually exposed and continuously magnified: (1) Since the asphalt binder is prone to volatilize toxic substances such as anthracene, phenol, formaldehyde, and (3,4) benzopyrene when heated, it seriously pollutes the working environment and cannot meet the environmental protection requirements; (2) Asphalt usually comes from by-products generated by processes such as coking and distillation of coal or petroleum, and inevitably contains a relatively high S element. The use of magnesia-carbon patching materials will have a serious sulfur-increasing pollution effect on molten steel. Especially for high-quality clean steel with strict S control, traditional magnesia-carbon patching materials are strictly prohibited; (3) The sintering time is too long. Since asphalt softens at low temperatures and needs to be hardened at a higher temperature (complete hardening requires up to above 500 °C), it often takes more than 40 minutes from the start of softening to complete hardening, resulting in too long sintering time required for magnesia-carbon patching materials and unable to meet the current requirements of high-efficiency steelmaking.

[0003] To solve the above problems of traditional magnesia-carbon ramming mixes, some scholars have developed a series of environmentally friendly water-based magnesia ramming mixes for converters, also known as water-based large-sized materials, water-mixed materials, etc., by referring to the self-flowing characteristics of castables, using various magnesia sands as the main raw materials, micro / nano SiO₂ as the binder, and adding high-efficiency water reducers. Before hot repair, a certain amount of water is added externally to prepare the water-based magnesia ramming mix into a slurry with a self-flowing effect, and then it is put into the converter using a scrap steel trough. With the tilting operation of the converter, the repair slurry will flow to the pit to be repaired under the tilting action. After sintering and solidification, the repair purpose can be achieved. Obviously, the water-based magnesia ramming mix has indeed well solved the problems of traditional magnesia-carbon ramming mixes such as environmental pollution, long sintering time, and steel water back-sulfur. This is also the reason why it is expected to replace traditional magnesia-carbon ramming mixes in recent years, attracting more and more attention from refractory material scientists and technicians, and a large number of known and publicly disclosed intellectual property technical solutions have emerged, such as CN115385668A, CN116751067A, CN106747505A, etc. Although the water-based magnesia ramming mix has well solved the problems existing in traditional magnesia-carbon materials, it has also brought many new problems: (1) The production cost is high, and its benefit improvement cannot match the cost increase, and it is not competitive under current conditions; (2) Water needs to be added in advance on-site to prepare the slurry, increasing the working intensity in front of the furnace. At the same time, the water addition amount fluctuates greatly due to human factors, and it is difficult to control the repair quality; (3) In the early stage of repair, due to the addition of too much free water, it causes great damage to the original furnace lining. It is precisely because of these objective problems that the large-scale popularization and application of water-based magnesia ramming mixes have been hindered. Summary of the Invention

[0004] In view of the problems existing in the above-mentioned water-based magnesia ramming mix, the present application proposes a zero-carbon and sulfur-free magnesia ramming mix based on the promotion of flow by crystal water and its sintering performance regulation method. After being heated, the ramming mix quickly reacts to release a large amount of crystal water, and rapidly forms a sol product with SiO₂ fine powder particles in the system and light-burned MgO particles in-situ decomposed from hydromagnesite. This sol product can not only effectively bond the aggregate and matrix in the ramming mix, play a preliminary binding effect and improve the medium and low temperature strength of the ramming mix layer, but also accelerate the promotion effect of the slurry on the aggregate. After the water evaporates and the sintering reaction is completed, a firm sintered layer of the ramming mix can be formed in the area to be repaired of the furnace lining, thus achieving the purpose of rapid furnace repair.

[0005] To solve the above problems, the specific technical solution of the present invention is as follows: A zero-carbon and sulfur-free magnesia ramming mix based on the promotion of flow by crystal water, characterized in that it is made of the following raw materials in parts by weight:

[0006]

[0007] The above components total 100%, and are mixed to form a basic ramming mix.

[0008] The magnesite is one or more of sintered magnesite or fused magnesite, and the MgO content of the magnesite raw material is ≥ 80 wt%.

[0009] The purity of the strontium chloride hexahydrate is ≥ 99 wt%.

[0010] The repair material also needs to be added with a high - efficiency water - reducing agent, and its addition ratio is 0.3 wt% - 0.5 wt% of the basic repair material.

[0011] The high - efficiency water - reducing agent is one of polyethylene glycol, sodium tripolyphosphate, lignosulfonate or polycarboxylate.

[0012] The preferred high - efficiency water - reducing agent is polyethylene glycol, and the particle size is ≤ 200 mesh.

[0013] The repair material also needs to be added with metallic aluminum powder, and its addition ratio is 2 wt% - 5 wt% of the basic repair material, and the particle size of the aluminum powder is ≤ 200 mesh.

[0014] Based on the specific sintering performance regulation method of magnesia repair material, it includes the following steps

[0015] Step 1: Understand the basic data of the converter to be repaired: Focus on mastering the remaining temperature T of the furnace chamber during converter repair 余 , the single - time repair material dosage Y and the specific sintering time t given in front of the furnace 给 ;

[0016] Step 2: Use Y and t obtained in Step 1 给 Calculate the ton - material sintering time coefficient ζ according to the following formula;

[0017] ζ = t 给 / Y (Equation 6)

[0018] Step 3: Use ζ calculated in Step 2 and T obtained in Step 1 余 , refer to the following table to select the ratio of the addition amount of metallic aluminum powder to hydromagnesite, that is, the best value of A / H;

[0019] Table 4 Selection table of the best recommended value of A / H determined by furnace temperature and sintering time coefficient

[0020]

[0021] Step 4: According to the best value of A / H selected in Step 3, calculate the minimum addition ratio (Al) wt% of metallic Al powder according to the following formula:

[0022] (Al) wt% = (A / H) × (hydromagnesite) wt% (Equation 7)

[0023] Step 5: Float the (Al)wt% value calculated in Step 4 by 10% as the final addition ratio of metallic aluminum powder and introduce it in an external addition form, then the repair material can be achieved under the residual temperature T of the furnace hearth 余 condition, and adjust the sintering time to t 给 within the purpose, which can well meet the production rhythm of steelmaking in front of the furnace.

[0024] The zero-carbon and sulfur-free magnesia dry repair material based on the promotion of fluidity by crystal water of the present application has the following advantages when adopting the above components:

[0025] 1. Utilize the in-situ release of crystal water by magnesium chloride hexahydrate, strontium chloride hexahydrate, and hydromagnesite to promote fluidity, replacing the traditional method of mixing water-based magnesia repair materials with water into slurry, which can greatly reduce the secondary damage of water to the furnace lining body;

[0026] 2. Since the repair material provided in the present application is dry material fed into the furnace and there is no need to add water on-site to prepare slurry, the total amount of in-situ crystal water release can be accurately controlled by adjusting the addition amounts of hydromagnesite, magnesium chloride hexahydrate, and strontium chloride hexahydrate, so as to achieve the purpose of autonomously regulating the density and sintering performance of the repair material layer;

[0027] 3. At the repair working temperature, the magnesium oxide particles generated by the decomposition reaction of hydromagnesite and magnesium chloride hexahydrate have a large specific surface area and high reaction activity, which is beneficial to promoting solid-phase sintering; and the decomposed CO2 and HCl gases can effectively increase the internal atmosphere pressure of the repair material layer and enhance the driving force for water discharge inside the green body; an appropriate amount of Al powder is added, which reacts rapidly with the released crystal water and is accompanied by a strong heat release effect, starting from compensating for the endothermic cooling problem caused by the decomposition reaction of hydromagnesite, magnesium chloride hexahydrate, and strontium chloride hexahydrate in the repair material system, and providing temperature guarantee for the sintering process. The synergistic effect of the above three aspects makes the repair material provided in the present application have good sintering performance and the required sintering time is shortened.

[0028] 4. The highly active MgO particles generated by the decomposition of hydromagnesite and magnesium chloride hexahydrate in the components can not only accelerate the solid-phase sintering reaction process, but also react in-situ with the SiO2 fine powder particles and the hydrothermal reaction products of metallic Al powder in the components to generate high-melting-point forsterite (melting point about 1890 °C) and magnesium aluminate spinel (melting point about 2135 °C), reducing the liquid phase generation amount in the material system at the working temperature, forming a highly directly bonded microstructural organization, and improving the medium and high temperature strength of the repair material layer; in addition, the above in-situ reactions are all accompanied by a certain volume expansion effect, effectively blocking the pores in the repair material layer caused by the escape of crystal water, hydrated products, CO2 and other components, realizing tissue densification, and effectively enhancing the slag erosion and penetration resistance of the repair material. Therefore, the repair material provided in the present application has a high service life and good durability.

[0029] 5. By cleverly utilizing the characteristics that strontium chloride hexahydrate has a low crystallization water release temperature and a large drainage volume, the present invention uses it in combination with magnesium chloride hexahydrate, which can effectively reduce the crystallization water release temperature of magnesium chloride hexahydrate, improve the water discharge speed, and can greatly enhance the ability of the repair material to quickly form a self-leveling performance. In addition, the boiling point of strontium chloride is 1250 °C, and at the working temperature of the converter, it will gradually volatilize and discharge from the repair material layer, having little impact on the refractoriness and durability of the repair material system.

[0030] 6. This application does not add sulfur-containing raw materials such as asphalt, and the C in hydromagnesite in the components exists in the form of carbonate, which can be completely decomposed into CO2 and discharged during the sintering and standing process of the repair material, without the risk of carbon addition and sulfur return to the molten steel. Therefore, the magnesia repair material provided by this application is a veritable zero-carbon and sulfur-free product, which can fully meet the current requirements of green and clean steelmaking. Specific embodiments

[0031] A zero-carbon and sulfur-free magnesia repair material based on the promotion of fluidity by crystallization water, characterized in that it is made of the following raw materials in parts by weight:

[0032]

[0033] The above components total 100%, and are mixed to form a basic repair material.

[0034] To further improve the high-temperature fluidity of the repair material and obtain excellent sintering performance, on the basis of the above basic repair material formula, the following additives are generally additionally added:

[0035]

[0036] Further, the magnesite is one or more of sintered magnesite and fused magnesite, which acts as the main raw material in the formula system and is the main part of the repair layer. Therefore, to enable the repair material to obtain good high-temperature performance, this scheme requires that the MgO content of the magnesite raw material ≥ 80 wt%.

[0037] Further, the magnesium chloride hexahydrate is an industrial-grade chemical raw material with a white granular appearance, and its main component is MgCl2·6H2O. This application requires its content ≥ 98 wt%. Magnesium chloride hexahydrate is the main carrier for in-situ release of crystallization water in this technical solution, and its theoretical crystallization water content is as high as about 53.1%. However, in the case of not adding other components, its heating change process generally consists of the following several stages:

[0038] Stage 1, when the temperature is 96 - 117 °C:

[0039] MgCl2·6H2O = MgCl2·4H2O + 2H2O (Equation 1)

[0040] Stage 2, when the temperature is 135 - 180 °C:

[0041] MgCl2·4H2O = MgCl2·2H2O + 2H2O (Equation 2)

[0042] Stage 3, when the temperature is 185 - 230 °C:

[0043] MgCl2·2H2O = MgCl2·H2O + 2H2O (Equation 3)

[0044] Stage 4, when the temperature is above 230 °C:

[0045] MgCl2·H2O = Mg(OH)Cl + HCl↑ (Equation 4)

[0046] Stage 5, when the temperature is above 527 °C:

[0047] Mg(OH)Cl = MgO + HCl↑ (Equation 5)

[0048] It can be seen that in the absence of interference from other components, the internal crystal water in magnesium chloride hexahydrate is gradually released and discharged mainly in three stages under heating conditions. Moreover, the temperature window width of each stage is about 20 - 50 °C, and the release rate of each window period is about 17.7%. In addition, when the temperature of magnesium chloride hexahydrate is above 527 °C, the final product is the high-temperature phase MgO. Therefore, for this application, magnesium chloride hexahydrate is an ideal crystal water carrier with a large water content, a high water discharge rate, and a good end product. However, the disadvantages of magnesium chloride hexahydrate are also obvious. Mainly due to its relatively high water discharge temperature and large gaps during each water discharge window period, the release of crystal water is discontinuous, and it is impossible to quickly form a large number of continuous water aggregation areas. As a result, the released water is quickly evaporated before it is fully wetted and combined with the silica micropowder in the system, which significantly weakens the technical effect of this application of in-situ generating slurry with a self-flowing effect, that is, it will greatly reduce the fluidity of the zero-carbon sulfur-free magnesia repair material. To overcome this shortcoming, this application will introduce strontium chloride hexahydrate and hydromagnesite as two components as crystal water auxiliary carriers and magnesium chloride hexahydrate crystal water accelerating release agents to maximize the ability of the material system to quickly form a water aggregation area at the repair temperature.

[0049] The strontium chloride hexahydrate is a hydrated strontium salt crystal material with a white granular appearance. The theoretical crystal water content in its crystal structure is about 40.5%, and it is basically released and discharged in three temperature stages: that is, 4 molecules of crystal water are discharged when heated to about 61°C, and when the temperature reaches 100°C and 150°C, 1 molecule of crystal water is lost each. It can be seen that strontium chloride hexahydrate not only has a high crystal water content, but also has a low discharge temperature and a fast release rate, and is a more ideal crystal water carrier. However, due to the low melting point and boiling point of the terminal product (SrCl2) after heating, although SrCl2 will evaporate completely at the use temperature, a large number of evaporative pores generated by adding too much strontium chloride hexahydrate will be unfavorable to the high temperature strength, durability and other performance of the repair material. Therefore, this application can only introduce it in a small amount in the form of an additive. It should be noted that the purpose of adding strontium chloride hexahydrate in this application is mainly two: one is to release a certain amount of crystal water before magnesium chloride hexahydrate, so as to quickly merge with some SiO2 micropowder particles in the system to form a sol mucosa with a large viscosity. Under the uniform wrapping effect of the sol mucosa, the surface of the magnesium chloride hexahydrate particles will become a closed "quasi-vacuum" state. This "quasi-vacuum" effect can effectively reduce the release temperature of the crystal water of magnesium chloride hexahydrate by about 25-50°C, and reduce the drainage window gap by 3-5°C, so that the release process of the crystal water of magnesium chloride hexahydrate tends to be concentrated and continuous to the greatest extent. In addition, the crystal water release stage and window temperature of strontium chloride hexahydrate complement and connect with magnesium chloride hexahydrate, which can further promote the rapid formation of a large number of continuous water aggregation areas in the entire crystal water carrier to achieve a flow-promoting effect; second, strontium chloride has a low melting point of only 874°C, and it is very easy to form a liquid phase that promotes the migration of solid particles during the sintering process of the repair material, thereby achieving the effect of promoting sintering. In order to achieve the above purpose to the greatest extent, this application requires that the purity of strontium chloride hexahydrate is ≥99wt%, and the particle size is preferably 0mm-1mm.

[0050] In order to study the effect of the ratio of the addition amount of the two crystal water carriers, magnesium chloride hexahydrate and strontium chloride hexahydrate, on the high-temperature fluidity of the zero-carbon and sulfur-free magnesium repair material, the inventor controlled the total amount of the two to be added at 20wt% and kept it unchanged, and only adjusted the mass ratio of the two from 1:1 to 5:1 in turn. On the basis of the same other raw material components and the same particle grading scheme, they were fully mixed and prepared into different repair material samples. Weigh 300g of each sample separately, and quickly put it into the bottom of a special resistance furnace with a furnace temperature of 1200℃ with a round material spoon. After closing the furnace door and keeping warm for 10 minutes, the repair material sample is plated into a round cake shape. The high-temperature fluidity of the sample is measured by the size of the round cake area, that is, the larger the round cake area, the better the fluidity of the repair material. However, in order to improve the accuracy, it is required that the test be operated by the same person throughout the whole process, and the action of placing the material into the furnace each time is uniform and the technique is consistent to ensure that the initial state of the round cake is the same. The final test results are shown in Table 1.

[0051] Table 1 Effect of different addition ratios of magnesium chloride hexahydrate and strontium chloride hexahydrate on high temperature fluidity of repair material

[0052]

[0053] As can be seen from Table 1, the blank sample without strontium chloride hexahydrate has the worst fluidity. This is because the dehydration temperature of magnesium chloride hexahydrate is relatively high and discontinuous, and a continuous water aggregation zone cannot be formed in the system. With the addition of strontium chloride hexahydrate, the dehydration of magnesium chloride hexahydrate can be effectively promoted. When the ratio of the addition amount of magnesium chloride hexahydrate to strontium chloride hexahydrate reaches 3:1, the promotion effect is the best and the high-temperature fluidity performance is the optimal. Therefore, in this application, the ratio of the addition amounts of the two crystal water carriers, magnesium chloride hexahydrate and strontium chloride hexahydrate, is fixed at 3:1 (by mass).

[0054] Under the condition that the ratio of the addition amounts of magnesium chloride hexahydrate to strontium chloride hexahydrate remains 3:1, the inventors conducted a large number of studies on the influence of the addition amount of strontium chloride hexahydrate on the fluidity and apparent porosity after firing of the zero-carbon sulfur-free magnesia repair material. The test results are shown in Table 2 for details.

[0055] Table 2 Influence of different addition ratios of strontium chloride hexahydrate on the high-temperature fluidity of the repair material

[0056]

[0057] As can be seen from Table 2, with the increase of the addition amount of strontium chloride hexahydrate, the pores caused by the evaporation of strontium chloride components at high temperature increase continuously, and the apparent porosity in the repair material matrix keeps rising. Especially when the addition amount > 6wt%, this change trend is more obvious. Therefore, from the perspective of ensuring the density of the repair material layer after firing, this application believes that the addition amount of strontium chloride hexahydrate should be ≤ 6wt%. However, too little strontium chloride hexahydrate will affect its promotion effect on the crystal water of magnesium chloride hexahydrate, thus inhibiting the formation of the water aggregation zone effect in the repair material matrix and reducing the fluidity performance, which is corroborated by the size of the sample cake formed after being evenly placed in an electric resistance furnace at 1200°C and kept warm for 10 minutes in Table 2. Therefore, it is not difficult to see from this table that to obtain good fluidity, the addition amount of strontium chloride hexahydrate cannot be lower than 4wt%. To sum up, considering comprehensively the fluidity and matrix density of the zero-carbon sulfur-free magnesia repair material, this application believes that the optimal addition amount of strontium chloride hexahydrate is 4wt% - 6wt%, and the best blending ratio of magnesium chloride hexahydrate is 12wt% - 18wt%.

[0058] The hydromagnesite is a natural hydrated basic magnesium carbonate ore, commonly known as natural magnesium white. Its main chemical composition is 3MgCO3·Mg(OH)2·3H2O, and the theoretical crystal water content is about 14.8%. Without the influence of other components, the crystal water release temperature is 150°C to 350°C. However, due to the promoting and catalytic effects of strontium chloride hexahydrate in this application, the crystal water release temperature of the hydromagnesite can be significantly reduced by about 50 to 60°C. Therefore, its addition is very beneficial to promoting the accelerated formation of the above-mentioned water aggregation area and improving the fluidity of the repair material at a lower temperature. In addition, the hydromagnesite is a composite ore of natural magnesite and brucite. There are two unique phase relationships and the characteristics of uniformly distributed structural water in its crystal structure. Compared with natural magnesite, it not only has a lower decomposition reaction temperature (starting at about 350°C and ending at 650°C), but also can obtain mesoporous network magnesium oxide particles with a large specific surface area and high reaction activity. During the sintering process of the repair material, these magnesium oxide particles will quickly react with the SiO2 fine powder particles in the repair material system to form a high-temperature phase of forsterite, and this reaction shows a volume expansion effect, which can effectively block the pores in the repair material layer, thereby improving the sintering strength and slag erosion resistance of the repair material layer. Furthermore, the hydromagnesite has a relatively high CaO content, which has a significant effect on increasing the C / S ratio of the repair material layer, improving the refractoriness of the material system, and purifying molten steel. To maximize the above beneficial effects, this application requires that the MgO content in the hydromagnesite is ≥40wt% and the particle size is ≤200 mesh. In addition, this application specifies that the optimal addition amount of the hydromagnesite is 4wt% to 6wt%. Otherwise, as shown in Table 3, the high-temperature strength of the zero-carbon sulfur-free magnesia repair material will be severely reduced. The reason is as follows: when the addition amount is <4wt%, the amount of active magnesium oxide particles generated in the repair material system is relatively small, and the volume expansion effect brought by the in-situ forsterite reaction cannot completely fill the evaporation pores caused by the discharge of crystal water, resulting in poor strength of the repair material layer; when the addition amount is >6wt%, too much hydromagnesite participates in the decomposition and calcination reaction and the reaction is extremely intense. Although the evaporation pores generated by the discharge of crystal water have been completely filled, a large amount of CO2 escape pores generated by its own decomposition still exist in the repair material system. In addition, severe stress damage will occur during the intense reaction process, resulting in a large number of destructive cracks distributed in the repair material matrix. The combined effect of the two greatly reduces the high-temperature strength index of the repair material layer. 2- There are two unique phase relationships and the characteristics of uniformly distributed structural water in its crystal structure. Compared with natural magnesite, it not only has a lower decomposition reaction temperature (starting at about 350°C and ending at 650°C), but also can obtain mesoporous network magnesium oxide particles with a large specific surface area and high reaction activity. During the sintering process of the repair material, these magnesium oxide particles will quickly react with the SiO2 fine powder particles in the repair material system to form a high-temperature phase of forsterite, and this reaction shows a volume expansion effect, which can effectively block the pores in the repair material layer, thereby improving the sintering strength and slag erosion resistance of the repair material layer. Furthermore, the hydromagnesite has a relatively high CaO content, which has a significant effect on increasing the C / S ratio of the repair material layer, improving the refractoriness of the material system, and purifying molten steel. To maximize the above beneficial effects, this application requires that the MgO content in the hydromagnesite is ≥40wt% and the particle size is ≤200 mesh. In addition, this application specifies that the optimal addition amount of the hydromagnesite is 4wt% to 6wt%. Otherwise, as shown in Table 3, the high-temperature strength of the zero-carbon sulfur-free magnesia repair material will be severely reduced. The reason is as follows: when the addition amount is <4wt%, the amount of active magnesium oxide particles generated in the repair material system is relatively small, and the volume expansion effect brought by the in-situ forsterite reaction cannot completely fill the evaporation pores caused by the discharge of crystal water, resulting in poor strength of the repair material layer; when the addition amount is >6wt%, too much hydromagnesite participates in the decomposition and calcination reaction and the reaction is extremely intense. Although the evaporation pores generated by the discharge of crystal water have been completely filled, a large amount of CO2 escape pores generated by its own decomposition still exist in the repair material system. In addition, severe stress damage will occur during the intense reaction process, resulting in a large number of destructive cracks distributed in the repair material matrix. The combined effect of the two greatly reduces the high-temperature strength index of the repair material layer.

[0059] Table 3 High-temperature flexural strength of zero-carbon sulfur-free magnesia repair materials with different proportions of hydromagnesite powder added

[0060]

[0061] The silica fume is a high-purity micron-sized SiO2, with the requirements that its SiO2 content ≥ 99.5wt%, and the average particle size ≤ 10μm. Its functions in this application are mainly as follows: (1) It can quickly fuse with the crystal water released in the system to form a silica sol with a certain viscosity, effectively inhibiting the rapid evaporation of the crystal water, enabling the material system to efficiently form a water aggregation zone at the repair operation temperature, thus ensuring the good fluidity of the zero-carbon sulfur-free magnesia repair material; (2) As a binder for the zero-carbon sulfur-free magnesia repair material, its binding effect is mainly reflected in two aspects: on the one hand, at a relatively low temperature, the silica sol formed by the silica fume has a typical adhesive and flow-promoting effect between the particles and the matrix in the material system; on the other hand, at a high temperature, the micron-sized SiO2 particles will react with the active magnesia particles in the system to produce magnesium olivine. The volume expansion effect generated by this reaction effectively fills various pores in the repair material layer. At the same time, the formation of magnesium olivine reduces the liquid phase content in the sintered body, improves the direct bonding degree under the microstructure, and strengthens the connection between MgO particles and the matrix, that is, finally forms a stable ceramic bonding state. Therefore, according to the addition ratios of the aforementioned magnesium chloride hexahydrate, strontium chloride hexahydrate, and hydromagnesite, and the effective crystal water amount that may be formed at the repair operation temperature, and comprehensively weighing the generation quantity of active magnesia and the reaction quantity of magnesium olivine in the entire system, the inventor obtained through a large number of experiments that the optimal addition ratio of the silica fume described in this application is 3wt% - 5wt%.

[0062] The high-range water reducer is one of the high-molecular long-chain organic compounds such as polyethylene glycol, sodium tripolyphosphate, lignosulfonate, polycarboxylate, etc., and is usually also called a high-efficiency surfactant. When added to the castable, it can have a good dispersion effect on the fine particles in its matrix, minimizing the agglomeration effect to the greatest extent, thereby reducing the mixing water consumption. In the solution of this application, polyethylene glycol is preferably used as the water reducer to obtain the best dispersion effect on fine particles such as SiO2 silica fume in the zero-carbon sulfur-free magnesia repair material system. At the initial stage of the release of crystal water, a silica sol mucous membrane with moderate viscosity and uniform distribution can be immediately formed, thus triggering the system to quickly form a water aggregation zone and rapidly realizing the self-flow response of the slurry. To maximize the above effects, further, polyethylene glycol with a particle size ≤ 200 mesh is selected, and the optimal addition amount is 0.3wt% - 0.5wt%.

[0063] Al + H2O = Al2O3 + H2↑ (Reaction 1)

[0064] H2 + O2 = H2O (Reaction 2)

[0065] The metallic aluminum powder is a powdery substance of elemental Al and is introduced as a heat supplement and strengthening agent in this application. In the zero-carbon and sulfur-free magnesia repair material system, the metallic aluminum powder will undergo a violent hydrothermal reaction with the high-temperature water vapor discharged by the crystal water carrier (see Reaction 1), generating Al2O3 and H2 and releasing a large amount of heat. Subsequently, the hydrogen will undergo a spontaneous combustion reaction with the oxygen in the air (see Reaction 2), also accompanied by an intense exothermic effect. It can be seen that through these two reactions, the problem of endothermic temperature drop caused by the release and discharge of crystal water, the calcination and decomposition of hydromagnesite, etc. in the repair material system can be effectively solved, so as to maintain a sufficient sintering temperature to ensure the sintering performance of the repair material layer. In addition, the Al2O3 generated by Reaction 1 will further undergo an in-situ reaction with MgO in the repair material system to generate a high-temperature phase of magnesium aluminate spinel (melting point about 2135°C), improving the direct bonding degree of the microstructural organization. At the same time, this in-situ reaction is also accompanied by an about 8% volume expansion. Like the in-situ forsterite reaction, it can also effectively fill various pores in the repair material system, thus playing an important role in improving the high-temperature strength of the repair material layer, enhancing heat resistance, and strengthening slag erosion resistance. The inventor measured the endothermic temperature drop values brought by different addition amounts of the crystal water carrier (hydromagnesite) and designed multiple groups of experiments respectively to summarize the compensation influence law of the addition amount of metallic aluminum powder on the temperature drop. Therefore, it is considered that the addition amount of metallic aluminum powder adopted in this application should not be less than 2wt%, the purity ≥ 98wt%, and the particle size ≤ 200 mesh. However, it was also found in the experiment that when the addition amount of metallic aluminum powder > 5wt%, the above in-situ spinel reaction is excessive, and the accompanying excessive volume expansion will cause a large amount of stress concentration in the matrix of the repair material layer, resulting in structural damage. In addition, when the addition amount of metallic aluminum powder is too large, the concentration of H2 generated by Reaction 1 is too high, posing a risk of deflagration or even explosion, which is not conducive to the on-site safety. Therefore, this application believes that it is appropriate to add 2wt% - 5wt% of metallic aluminum powder externally.

[0066] According to the raw material formula composition described above, batching is carried out, and after sufficient mixing, a zero-carbon and sulfur-free magnesia repair material can be prepared. After packaging, shipping, and transporting it to the front of the converter to be repaired, first determine the amount of repair material according to the position size, pit depth, and front-of-furnace arrangement of the area to be repaired. Subsequently, with the help of a scrap steel tank, the repair material of this amount is put into the furnace. Through reciprocating tilting of the furnace in cooperation, the repair material is quickly concentrated to the area to be repaired. After standing for a period of time and the sintering of the repair material is completed, the tilting furnace is reset and production resumes.

[0067] In addition, this application also provides a specific method for regulating the sintering performance of the zero-carbon and sulfur-free magnesia repair material, that is, on the basis of ensuring the normal preparation ratio principle of the crystal water carrier in this application, by continuously adjusting the addition amount ratio (A / H) between the metallic aluminum powder and hydromagnesite, the temperature in the sintering system of the repair material layer and the reaction rate and generation quantity of the in-situ spinel can be effectively controlled, so as to achieve the purpose of regulating the sintering performance. The specific steps are as follows:

[0068] Step 1: Understand the basic data of the converter to be repaired. Focus on mastering the remaining temperature T of the furnace chamber during converter repair 余 , the single - time repair material dosage Y, and the specific sintering time t given in front of the furnace 给 ;

[0069] Step 2: Use Y and t obtained in Step 1 给 to calculate the ton - material sintering time coefficient ζ according to the following formula.

[0070] ζ = t 给 / Y (Formula 6)

[0071] Step 3: Use ζ calculated in Step 2 and T obtained in Step 1 余 to select the ratio of the addition amount of metallic aluminum powder to hydromagnesite, that is, the best value of A / H, with reference to the following table.

[0072] Table 4 Selection table of the best recommended value of A / H determined by furnace temperature and sintering time coefficient

[0073]

[0074] Step 4: According to the best value of A / H selected in Step 3, calculate the minimum addition ratio of metallic Al powder (Al) wt% according to the following formula:

[0075] (Al) wt% = (A / H) × (hydromagnesite) wt% (Formula 7)

[0076] Step 5: Float the value of (Al) wt% calculated in Step 4 by 10% as the final addition ratio of metallic aluminum powder and introduce it in an external addition form, then the purpose of controlling the sintering time of the repair material within t can be achieved under the condition of the remaining temperature T of the furnace chamber 余 , which can well meet the production rhythm of steelmaking in front of the furnace. 给

[0077] Next, in combination with different application scenarios, different technical solutions of zero - carbon and sulfur - free magnesia repair materials based on the promotion of water of crystallization will be designed through specific embodiments to elaborate on the present invention in detail. It should be noted, however, that these embodiments are only the best implementation solutions for a specific application occasion and do not limit the scope of the present invention.

[0078] Example 1 Zero - carbon and sulfur - free magnesia repair material based on the promotion of water of crystallization and its sintering performance control method

[0079] This embodiment is for the daily maintenance of a 260-ton converter in a large domestic steel plant. The main products of this converter are SAPH400 series hot-rolled sheets and 40CrH series alloy bars. Usually, the end-point carbon tapping is carried out at a carbon content far lower than the product standard ([C] ≤ 0.10%), and high-intensity and large-flow bottom-blowing gas stirring is adopted throughout the furnace campaign. The end-point temperature is high (the tapping temperature ≥ 1700°C accounts for about 50%, and ≥ 1720°C accounts for about 10%), the oxidation of slag and steel is strong, the kinetic energy of the molten pool tumbling and eddy scouring on the furnace lining is large, and it is difficult to create the furnace lining slag layer, which severely restricts the improvement of the service life of the furnace lining and its repair materials. The average single repair material consumption in front of the furnace is 2.4t, and the average remaining temperature in the furnace chamber during each repair is 1350°C. The steel plant requires the sintering time for a single repair to be controlled within 22 minutes.

[0080] (1) Preparation of zero-carbon and sulfur-free magnesia-based repair material based on the flow-promoting effect of crystal water

[0081] According to the above smelting conditions, this embodiment will adopt the following weight ratio formulation to prepare a zero-carbon and sulfur-free magnesia-based repair material based on the flow-promoting effect of crystal water:

[0082]

[0083] The above components total 100%, and are mixed to form the basic repair material.

[0084] In addition, to further improve the high-temperature fluidity of the repair material and obtain excellent sintering performance, on the basis of the above basic repair material formula, the following additives need to be additionally added:

[0085]

[0086] Furthermore, to cope with the harsh smelting conditions of this converter, in this embodiment, the main raw material information is as follows: The magnesia is 97-grade fused magnesia, and its MgO content is 96.8wt%; The main component of the magnesium chloride hexahydrate is MgCl2·6H2O, and the purity of this embodiment is as high as 99.2wt%; To maximize the effect of promoting the discharge of crystal water, the purity of strontium chloride hexahydrate in this embodiment is selected as 99.2wt%; The hydromagnesite is from the Bangor Lake ore belt in Tibet, and its MgO content is 40.8wt%; The SiO2 content in the silica fume is as high as 99.6wt%, its particle size is not greater than 10μm, and D50 is about 5μm; The high-efficiency water reducer used in this embodiment is industrial pure polyethylene glycol; The purity of the aluminum powder is 98.2wt%.

[0087] According to the above specific raw material requirements and formula composition, batching is carried out and fully mixed evenly, then a zero-carbon and sulfur-free magnesia-based repair material can be prepared. After packaging, shipping and transporting it to the front of the converter to be repaired, the amount of repair material used is determined to be 2.4 tons according to the position and size of the area to be repaired, the depth of the pit, and the furnace front plan arrangement. Finally, with the help of a scrap steel tank, the repair material of this amount is put into the furnace. Through the cooperation of reciprocating tilting of the furnace, the repair material is quickly converged to the area to be repaired. After standing for a period of time and the sintering of the repair material is completed, the tilting of the furnace is reset and production is resumed.

[0088] (2) Sintering performance regulation method

[0089] Based on the above formula in this embodiment, by continuously adjusting the addition ratio (A / H) between metallic aluminum powder and hydromagnesite, the temperature in the sintering system of the repair material layer, the in-situ spinel reaction rate and the generated quantity can be effectively controlled, so as to achieve the purpose of regulating the sintering performance. The specific steps are as follows:

[0090] Step 1: Understand the basic data of the converter to be repaired. From the data mastered in this embodiment, the average remaining temperature T of the furnace chamber during each repair of this converter 余 = 1350 °C, the single-time repair material consumption Y = 2.4 tons, and the specific sintering time t given in front of the furnace 给 = 22 min;

[0091] Step 2: Use Y and t obtained in Step 1 给 Calculate the sintering time coefficient ζ per ton of material according to (Equation 6).

[0092] ζ = t 给 / Y = 22 min / 2.4 = 9.17 min

[0093] Step 3: Use ζ = 9.17 mim calculated in Step 2 and T obtained in Step 1 余 = 1350 °C. According to the data in Table 4, it can be determined that the addition ratio of metallic aluminum powder to hydromagnesite, that is, A / H should be ≥ 0.45.

[0094] Step 4: According to A / H ≥ 0.45 selected in Step 3, and from the formula composition of this embodiment, it is known that w(hydromagnesite)% = 4 wt%, then the minimum addition ratio (Al) wt% of metallic Al powder can be calculated according to (Equation 7):

[0095] (Al) wt% = 0.45 × (hydromagnesite) wt% = 0.45 × 4 wt% = 1.8 wt%

[0096] Step 5: The (Al)wt% value calculated in Step 4 is increased by 10% to obtain 1.98wt%. Then, according to the requirement in the previous text that the minimum addition of metallic Al powder is 2 wt% to achieve better effects, in this example, 2wt% is used as the final addition ratio of metallic aluminum powder and introduced in an external addition form. Thus, the purpose that the sintering time can be well controlled within 22 minutes under the condition that the average remaining temperature in the furnace hearth is 1350°C can be achieved, meeting the requirements of fast-paced steelmaking in front of the furnace.

[0097] Example 2: Zero-carbon and sulfur-free magnesia-based patch material based on crystallization water promoting fluidity and its sintering performance regulation method

[0098] This example is for the daily maintenance of a 150-ton converter in a domestic steel company. The main steel grades produced by this converter are mainly high-quality carbon structural steels such as SAE1006, Q195, and 3SP series, belonging to the low-carbon steel category. The product forms are mainly ribbed steel bars and high-speed wire rods that are relatively common in the market. Its main smelting characteristics are: high bottom-blowing intensity, strong scouring effect of high-temperature molten steel on the furnace lining and the patch material layer; relatively high [O] at the end of molten steel, strong oxidizability of the final slag, poor slag splashing effect on the furnace lining, and strong penetration and erosion ability on the furnace lining bricks and the patch material layer; high tapping temperature, mainly concentrated in the range of 1650 -

[0099] 1680°C. According to the follow-up investigation, the average single-time patching material consumption in front of the furnace is 2t, and the average remaining temperature in the furnace hearth is about 1200°C during each patching. The company expects the single-time patching sintering time to be controlled within 15 minutes.

[0100] (I) Preparation of zero-carbon and sulfur-free magnesia-based patch material based on crystallization water promoting fluidity

[0101] According to the above smelting conditions, this example will adopt the following weight ratio formulation to prepare a zero-carbon and sulfur-free magnesia-based patch material based on crystallization water promoting fluidity:

[0102]

[0103]

[0104] The above components total 100%, and are mixed to form the basic patch material.

[0105] In addition, to further improve the high-temperature fluidity of the patch material and obtain excellent sintering performance, on the basis of the above basic patch material formula, the following additives also need to be externally added:

[0106]

[0107] Further, to cope with the harsh smelting conditions of the converter, in this embodiment, the specific raw material information is as follows: the magnesite is 97-grade sintered magnesite with an MgO content of 97.1 wt%; the main component of the magnesium chloride hexahydrate is MgCl₂·6H₂O, and the purity in this embodiment is as high as 98.8 wt%; to maximize the effect of promoting the discharge of crystal water, the purity of strontium chloride hexahydrate is selected as 99.4 wt% in this embodiment; the hydromagnesite is sourced from the Bangong Lake ore belt in Tibet, with an MgO content of 41.5 wt%; the SiO₂ content in the silica powder is as high as 99.7 wt%, its particle size is not greater than 10 μm, and D50 is about 4 μm; the high-range water reducer selected in this embodiment is industrial pure polyethylene glycol; the purity of the aluminum powder is 98.5 wt%.

[0108] According to the above specific raw material requirements and formula composition, batching is carried out and fully mixed evenly, and then a zero-carbon and sulfur-free magnesia repair material can be prepared. After packaging, shipping, and transporting it to the front of the converter to be repaired, the amount of the repair material used is determined to be 2 tons according to the position and size of the area to be repaired, the depth of the pit, and in combination with the furnace front plan arrangement, etc. Finally, with the help of a scrap steel tank, the repair material of this amount is put into the furnace. Through reciprocating tilting of the furnace in cooperation, the repair material is quickly converged to the area to be repaired. After standing for a period of time and the sintering of the repair material is completed, the tilting of the furnace is reset and production is resumed.

[0109] (II) Sintering property regulation method

[0110] Based on the above formula in this embodiment, by continuously adjusting the addition ratio (A / H) between the aluminum powder and the hydromagnesite, the temperature, the in-situ spinel reaction rate, and the generated quantity in the sintering system of the repair material layer can be effectively controlled, so as to achieve the purpose of regulating the sintering property. The specific steps are as follows:

[0111] Step 1: Understand the basic data of the converter to be repaired. From the data mastered in this embodiment, the average remaining temperature T of the furnace chamber during each repair of this converter 余 = 1200 °C, the single-time repair material usage Y = 2 tons, and the specific sintering time t given in front of the furnace 给 = 15 min;

[0112] Step 2: Use Y and t obtained in Step 1 给 to calculate the tonnage sintering time coefficient ζ according to (Equation 6).

[0113] ζ = t 给 / Y = 15 min / 2 = 7.5 min

[0114] Step 3: Using ζ = 7.5 mim calculated in Step 2 and T obtained in Step 1 余 = 1200 °C, according to the data in Table 4, it can be determined that the addition ratio of the aluminum powder to the hydromagnesite, that is, A / H, should be ≥ 0.65.

[0115] Step 4: Based on the selected A / H ≥ 0.65 in Step 3, and from the formulation composition of this embodiment, w(magnesite hydrate) % = 5 wt%, then the minimum addition ratio of metallic Al powder (Al) wt% can be calculated according to (Equation 7):

[0116] (Al) wt% = 0.65 × (magnesite hydrate) wt% = 0.65 × 5 wt% = 3.25 wt%

[0117] Step 5: Floating the value of (Al) wt% calculated in Step 4 by 10% gives 3.6 wt%. Then, in this embodiment, 3.6 wt% is used as the final addition ratio of metallic aluminum powder and introduced in an external addition form, so that the sintering time of the repair material can be well controlled within 15 min under the condition that the average remaining temperature in the furnace hearth is 1200 °C, which better meets the requirements of fast-paced steelmaking in front of the furnace.

[0118] Example 3 Zero-carbon and sulfur-free magnesia-based repair material based on water of crystallization promoting fluidity and its sintering performance regulation method

[0119] This embodiment is carried out for the actual daily maintenance of a 120-ton converter in a domestic steel plant. This converter mainly produces medium and high carbon steels such as Q235B, Q255B, 45#, and HRB300, and mainly produces and sells high-speed wire rods and construction steel bars. The smelting characteristics of this converter are as follows: the tapping temperature is relatively low, usually 1620 °C - 1640 °C; the final slag basicity is high, 3.5 - 4.2; the final slag FeO (wt) is less than 10%, the slag viscosity is moderate, and the slag splashing for furnace protection effect is better; the main reason for the damage of the repair material layer is poor sintering performance and insufficient strength. According to the feedback in front of the furnace, the average single repair material consumption of this converter is 1.6 t. Due to the large tapping temperature drop, the average remaining temperature in the furnace hearth is only about 1000 °C during each repair. To maximize the production efficiency of the workshop, the company's planning and scheduling department requires that the single repair sintering time should preferably not exceed 10 min, and accidents such as material overturning and caving are not allowed.

[0120] (1) Preparation of zero-carbon and sulfur-free magnesia-based repair material based on water of crystallization promoting fluidity

[0121] According to the above smelting conditions, this embodiment will adopt the following weight ratio formulation to prepare a zero-carbon and sulfur-free magnesia-based repair material based on water of crystallization promoting fluidity:

[0122]

[0123] The above components total 100%, and are mixed to form a basic repair material.

[0124] In addition, to further improve the high-temperature fluidity of the repair material and obtain excellent sintering performance, on the basis of the above basic repair material formulation, the following additives need to be externally added:

[0125]

[0126] Furthermore, to cope with the harsh smelting conditions of the converter, in this embodiment, the specific raw material information selected is as follows: The magnesite is 92-grade dead-burned magnesite with an MgO content of 92.5 wt%; the main component of the magnesium chloride hexahydrate is MgCl₂·6H₂O, and the purity in this embodiment is as high as 98.5 wt%; to maximize the effect of promoting the discharge of crystal water, the purity of strontium chloride hexahydrate in this embodiment is selected as 99.6 wt%; the hydromagnesite is sourced from the salt lake area of the Qinghai-Tibet Plateau with an MgO content of 41.8 wt%; the silicon dioxide fine powder has an SiO₂ content as high as 99.8 wt%, its particle size is not greater than 10 μm, and D50 is about 3 μm; the high-range water reducer used in this embodiment is still industrial pure polyethylene glycol; the purity of the aluminum powder is 98.8 wt%.

[0127] According to the above specific raw material requirements and formula composition for batching, and fully mixing them evenly, a zero-carbon and sulfur-free magnesia repair material can be prepared. After packaging, shipping, and transporting it to the front of the converter to be repaired, the amount of the repair material used is determined to be 1.6 tons according to the position and size of the area to be repaired, the depth of the pit, and in combination with the furnace front plan arrangement, etc. Finally, with the help of a scrap steel trough, the repair material of this amount is put into the furnace. Through the cooperation of reciprocating tilting of the furnace, the repair material is quickly converged to the area to be repaired. After standing for a period of time and the sintering of the repair material is completed, the tilting of the furnace is reset and production resumes.

[0128] (II) Sintering performance regulation method

[0129] Based on the above formula in this embodiment, by continuously adjusting the addition ratio (A / H) between the aluminum powder and the hydromagnesite, the temperature, the in-situ spinel reaction rate, and the generated quantity in the sintering system of the repair material layer can be effectively controlled, so as to achieve the purpose of regulating the sintering performance. The specific steps are as follows:

[0130] Step 1: Understand the basic data of the converter to be repaired. From the data mastered in this embodiment, the average remaining temperature T of the furnace chamber during each repair of this converter 余 = 1000 °C, the single-time repair material consumption Y = 1.6 tons, and the specific sintering time t given in front of the furnace 给 = 10 min;

[0131] Step 2: Use Y and t obtained in Step 1 给 to calculate the sintering time coefficient ζ per ton of material according to (Equation 6).

[0132] ζ = t 给 / Y = 10 min / 1.6 = 6.25 min

[0133] Step 3: Use ζ = 6.25 mim calculated in Step 2 and T obtained in Step 1 余= 1000 °C. According to the data in Table 4, the ratio of the addition amount of metallic aluminum powder to that of hydromagnesite, i.e., A / H, should be ≥ 0.85.

[0134] Step 4: Based on A / H ≥ 0.85 selected in Step 3, and knowing from the formulation of this embodiment that w(hydromagnesite)% = 6 wt%, the minimum addition ratio of metallic Al powder, (Al) wt%, can be calculated according to (Equation 7):

[0135] (Al) wt% = 0.85 × (hydromagnesite) wt% = 0.85 × 6 wt% = 5.1 wt%

[0136] Step 5: Floating the value of (Al) wt% calculated in Step 4 by 10% gives 5.6 wt%. Then, according to the requirement that the optimal addition ratio of metallic Al powder should not be more than 5 wt% as mentioned above, therefore, in this embodiment, 5 wt% is taken as the final addition ratio of metallic aluminum powder and introduced in an external addition form. Thus, under the condition that the average residual temperature in the furnace is only 1000 °C, the sintering time of the repair material can be controlled within 10 min to the greatest extent, which can better meet the requirements of high-efficiency steelmaking in steel plants.

[0137] The actual usage effects achieved in the above Examples 1 - 3 were summarized in Table 2 and compared with the traditional pitch-bonded magnesia-carbon repair materials used in each converter.

[0138] Table 5 Actual application effects obtained in each example

[0139]

[0140] As can be seen from Table 5, the technical solution of this application has the ability to quickly form a water aggregation area. The crystal water has an effective flow-promoting effect at high temperatures, and the high-temperature fluidity is good. Compared with the traditional magnesia-carbon repair materials, the sintering time required for this application is significantly shortened (decreased by 45% - 67%), while the service life is significantly improved (increased by 40% - 70%). Each example can better meet the basic requirements of high-efficiency and fast-paced steelmaking in each steel plant, and good application effects have been achieved.

Claims

1. A zero-carbon and sulfur-free magnesia-based repair material based on the flow-promoting effect of crystal water, characterized in that, It is made from the following raw materials by weight: Raw material Particle size Addition ratio (by weight) Magnesite 0mm - 5mm 65wt% - 77wt% Magnesium chloride hexahydrate 0mm - 1mm 12 wt% - 18 wt% Strontium chloride hexahydrate 0mm - 1mm 4 wt% - 6 wt% Hydromagnesite ≤200 mesh 4 wt% - 6 wt% Silica fume ≤10μm 3 wt% - 5 wt% The above components total 100%, and are mixed to form a basic repair material.

2. The zero-carbon and sulfur-free magnesia repairing material based on promoting flow by crystal water according to claim 1, characterized in that, The magnesite is one or more of sintered magnesite or fused magnesite, and the MgO content of the magnesite raw material is ≥80wt%.

3. The zero-carbon and sulfur-free magnesia-based patching material based on promoting flow by crystal water according to claim 1, wherein The purity of the strontium chloride hexahydrate is ≥99wt%.

4. The zero-carbon sulfur-free magnesia-based patching material based on promoting flow by crystal water according to claim 1, wherein The repair material also needs to be added with a high - efficiency water - reducing agent, and its addition ratio is 0.3wt% - 0.5wt% of the basic repair material.

5. The zero-carbon and sulfur-free magnesia-based patching material based on promoting flow by crystal water according to claim 4, characterized in that The high - efficiency water - reducing agent is one of polyethylene glycol, sodium tripolyphosphate, lignosulfonate or polycarboxylate.

6. The zero-carbon and sulfur-free magnesia-based patching material based on promoting flow by crystal water according to claim 5, characterized in that The high - efficiency water - reducing agent is polyethylene glycol, and the particle size is ≤200 mesh.

7. The zero-carbon and sulfur-free magnesia-based patching material based on promoting flow by crystal water according to claim 1, characterized in that, The repair material also needs to be added with metallic aluminum powder, and its addition ratio is 2wt% - 5wt% of the basic repair material, and the particle size of the aluminum powder is ≤200 mesh.

8. The specific sintering property regulation method of the magnesia-based patching material according to claim 7, characterized in that It includes the following steps. Step 1: Understand the basic data of the converter to be repaired: Focus on mastering the remaining temperature in the furnace during converter repair T 余 , the amount of single repair material Y and the specific sintering time given in front of the furnace t 给 ; Step 2: Using what is obtained in Step 1 Y and t 给 calculate the sintering time coefficient ζ per ton of material according to the following formula; ζ = t 给 / Y (Equation 6) Step 3: Using ζ calculated in Step 2 and T 余 , select the ratio of the addition amount of metallic aluminum powder to hydromagnesite with reference to the following table, that is, the best value of A / H; Table for selecting the best recommended value of A / H determined by furnace temperature and sintering time coefficient ； Step 4: According to the best value of A / H selected in Step 3, calculate the minimum addition ratio (Al)wt% of the metallic Al powder according to the following formula: (Al) wt% = (A / H) × (Hydromagnesite) wt% (Formula 7) Step 5: Float the (Al) wt% value calculated in Step 4 by 10% as the final addition ratio of metallic aluminum powder. If the calculated (Al) wt% value is less than 2 wt%, use 2 wt% as the final addition ratio of metallic aluminum powder; if the calculated (Al) wt% value is greater than 5 wt%, use 5 wt% as the final addition ratio of metallic aluminum powder; and introduce it in an external addition form, then the purpose of the patch material at the remaining temperature in the furnace T 余 condition can be achieved by adjusting the sintering time to t 给 within, which can well meet the production rhythm of steelmaking in front of the furnace.

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