CN-119191821-B - Non-cement magnesia castable and application method thereof

Abstract

The invention relates to the technical field of refractory materials, in particular to a cement-free magnesia castable and a use method thereof. The castable consists of aggregate, matrix material and water reducer, wherein the aggregate is 60-80 parts of magnesia particles, and the matrix material is magnesia fine powder, active alpha-Al 2 O 3 micro powder, sintered corundum fine powder, silicon micro powder and aluminum-based metal microcapsules. The application method of the cement-free magnesium castable comprises the steps of uniformly mixing a water reducer and a matrix material to obtain a pre-mixed matrix material, uniformly stirring aggregate and the pre-mixed matrix material, adding water, wet-mixing and stirring to obtain slurry, pouring the uniformly mixed slurry into a mold, vibrating, molding and maintaining. The cement-magnesium-free castable has certain initial strength, excellent high-temperature performance, excellent slag erosion resistance and thermal shock resistance, long service life and can be widely applied to tundish, steel ladle and other parts.

Inventors

• GU HUAZHI
• CAI TIAN
• SUN LI
• ZHANG MEIJIE
• HUANG AO
• FU LVPING
• ZOU YONGSHUN
• ZHANG JIXIANG
• LIU XING
• YI BIHUI

Assignees

• 武汉科技大学
• 武汉如星科技有限公司

Dates

Publication Date

20260505

Application Date

20240912

Claims (7)

1. 1. The cement-magnesium-free castable is characterized by comprising aggregate, a matrix material and a water reducer; 60-80 parts of magnesia particles; the matrix material is: 10-20 parts of magnesia fine powder, 2-6 Parts of active alpha-Al 2 O 3 micro powder, 5-10 Parts of sintered corundum fine powder, 0.1 To 0.5 part of silicon micropowder, 2-8 Parts of aluminum-based metal microcapsules; The preparation method of the aluminum-based metal microcapsule comprises the following steps: s1, placing aluminum powder or aluminum-based alloy powder into a metal compound solution for reduction reaction, stirring for a period of time, depositing metal nano particles on the surface of the aluminum powder or aluminum-based alloy powder, continuously adding magnesium salt into the solution, stirring for 30min, and filtering and drying to obtain a microcapsule precursor, wherein the metal compound solution is ferric chloride solution or nickel chloride solution, and the metal nano particles are nano Fe or nano Ni particles; s2, carrying out heat treatment on the microcapsule precursor in air at 150-500 ℃ and then naturally cooling to obtain the aluminum-based metal microcapsule.
2. 2. The cement-free magnesia castable according to claim 1, wherein the particle size of the aluminum powder or the aluminum-based alloy powder is less than or equal to 74 μm, and the aluminum-based alloy powder contains Si and Fe, and the Si content is less than 40wt%.
3. 3. The magnesium-free castable according to claim 1, wherein in the step S1 of the preparation method of the aluminum-based metal microcapsule, the reduction reaction is performed at 40 to 60 ℃ and stirred for 30 to 60 minutes.
4. 4. The cement-free magnesia castable according to claim 1, wherein in the step S1 of the preparation method of the aluminum-based metal microcapsule, the magnesium salt is one of magnesium nitrate, magnesium oxalate and magnesium carbonate.
5. 5. A cement-free magnesia castable as defined in claim 1, wherein said magnesia particles comprise: 18-25 parts of magnesia particles with the particle size of less than 5mm and more than or equal to 3mm, 24-30 Parts of magnesia particles with the particle size of less than 3mm and more than or equal to 1mm, 18-25 Parts of magnesia particles with the particle size smaller than 1mm and larger than 0.1 mm; the MgO content of the magnesia fine powder is more than or equal to 96wt percent, the grain size of the magnesia fine powder is less than or equal to 40 mu m, and the magnesia fine powder is one of fused magnesia and sintered magnesia.
6. 6. The cement-free magnesium castable according to claim 1, wherein the water reducer is 0.1-0.4% of the sum of the aggregate and the matrix material, and the water reducer is one of sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate and sodium silicate.
7. 7. A method for using the cement-magnesium-free castable according to any one of claims 1 to 6, which is characterized by uniformly mixing a water reducing agent and a matrix material, wherein the sum of the aggregate and the matrix material is 0.1-0.4%, so as to obtain a pre-mixed matrix material, uniformly stirring the aggregate and the pre-mixed matrix material, adding water, the sum of the aggregate and the matrix material is 3-4%, stirring for 1-3 min, so as to obtain slurry, pouring the slurry into a mould, vibrating and molding, and curing for 1-3 days.

Description

Non-cement magnesia castable and application method thereof Technical Field The invention relates to the technical field of refractory materials, in particular to a cement-free magnesia castable and a use method thereof. Background The magnesia castable taking magnesia as the main raw material has the advantages of high refractoriness, high load softening temperature, good alkaline slag corrosion resistance, good compatibility with molten steel, low pollution to molten steel oxygenation, and the like, and meets the requirements of clean steel smelting. In modern industrial production, the quality and performance requirements on magnesia castable are higher and higher. The quality, microstructure and high-temperature performance of the magnesia castable are determined to a certain extent by the binding agent for the magnesia castable. Currently, binding systems are evolving towards "purification" which refers to the fact that the binding agent does not introduce impurities as much as possible, since impurities are generally detrimental to the high temperature performance, and "stabilization" which refers to the fact that the volatilization or decomposition of the binding agent is minimized to the detriment of the material structure. The magnesia refractory castable initially uses a calcium aluminate cement binder, and the cement binder castable can obtain high enough early strength and excellent workability when the environmental temperature is low. Cement middlings are mainly calcium monoaluminate (CA) and calcium dialuminate (CA 2), and generally also contain very small amounts of dodecacalcium heptaluminate (C 12A7). After the castable is stirred by adding water, calcium aluminate minerals CA, CA 2、C12A7 in cement react with the water, and the staggered growth of hydration products causes the castable to be gradually coagulated and hardened. Although the early strength of cement is high and the workability is excellent, the use of cement also brings about some adverse effects, on one hand, the castable is removed by combining water when the temperature is raised to destroy the structure so that the material is peeled off or even burst, and on the other hand, caO introduced by the cement is easy to react with the castable or SiO 2、MgO、Al2O3 and the like in the use environment to generate low-melting matters, thereby reducing the high-temperature mechanical property and slag resistance. This results in a limited service temperature and life of the cement bonded castable. Magnesium oxychloride cement is used as a magnesia castable binder. The magnesium oxychloride cement is a gel material formed by MgO-MgCl 2-H2 O ternary components, and has the advantages of quick setting, high strength, good elasticity, convenient molding and the like. The high-temperature decomposition product of magnesium oxychloride cement is active MgO, and the magnesium oxychloride cement is used as a binding agent of a magnesia refractory castable, and has the advantages of no introduction of harmful substances, high load softening temperature of the material, good slag resistance, low cost and the like. But has the defect that after 1100 ℃ heat treatment, the flexural strength of the castable is obviously reduced, mainly because the magnesium oxychloride cement gel is dehydrated and decomposed to be converted into MgO in the heating process, and the gelation structure is destroyed, so that the performance of the castable is greatly reduced. Polymeric phosphates (principally sodium polyphosphate) are used as binders for unshaped refractories, with sodium tripolyphosphate and sodium hexametaphosphate being common magnesia castable binders. Sodium tripolyphosphate is dissolved in water to form sodium monohydrogen phosphate and sodium dihydrogen phosphate, and the two compounds react with MgO to generate sodium magnesium phosphate to generate a combination effect. When the magnesium-based castable is used as a binding agent of magnesium castable, the castable has higher hardening speed, higher strength and good thermal shock stability. The sodium tripolyphosphate can generate polymerization which is helpful for improving the strength of the material when being heated, and does not generate the phenomenon of loose blank structure caused by phase change, so that the combined material has higher strength from normal temperature to medium temperature. However, after the liquid phase appears at high temperature, the castable hot strength is reduced. When sodium hexametaphosphate is used as a binder, sodium dihydrogen phosphate (NaH 2PO4).NaH2PO4 and alkaline earth metal oxides such as magnesia and the like are prepared into castable materials, mg (H 2PO4)2.Mg(H2PO4)2 can be quickly formed into MgHPO 4 after being dried at normal temperature) can be formed by reaction, and the castable materials can be quickly hardened, mg (H 2PO4)2 and MgHPO 4 are respectively condensed into magnesium polyphosphate (Mg (PO 3)2]n and Mg 2(P2O7)]n) at about 50