CN1262257A - Process for preparing 'Meialong' magnesium ceramics with natural minerals as raw materials - Google Patents

Abstract

A process for preparing "Meialong" as high-grade refractory features use of cheaper natural mineral(alumyte) as raw material. The alumina contained in the alumyte is directly reduced in industrial furnace and immediately nitrided and solutionized to form "Meialong". Its advantages are lower cost and high productivity.

Description

Preparation of MgAION from natural mineral raw material

The present invention belongs to the preparation technology of high-temperature refractory materials.

At present, carbon-containing refractory materials commonly used in the metallurgical industry at home and abroad are difficult to meet the requirements of pure super steel which is provided for steel products and has no pollution insmelting due to the problems of carburization and oxygen permeation in the using process. Chromium-containing refractories, although excellent in corrosion resistance, are prohibited sooner or later due to the 6-valent toxic side effect. A newly developed solid solution of aluminum oxynitride containing magnesium oxide, having the chemical formula Al₂₃O₂₇N₅X MgO (X ═ 2.5 to 40), expressed as MgAlon, and generally called mazaron, is an excellent magnesium aluminum oxynitride ceramic composite refractory material which is excellent in resistance to slag erosion and steel bath erosion, and which is stable and does not contain carbon, and does not cause carburization or oxygen permeation, and thus can be fully impregnated with the refractory materialMeets the requirement of smelting high-quality super steel and can avoid pollution caused by the use process. However, the high-tech ceramics are made of pure AlN and Al₂O₃And MgO is synthesized in a neutral atmosphere at high temperature, the production cost is high, the production efficiency is low, and the MgO is difficult to be used in the production of the metallurgical industry.

The invention aims to find a raw material and a method for synthesizing MgAlON, which have low production cost and high production efficiency.

The inventor can realize the purpose of the invention by utilizing cheap natural mineral raw materials and industrial kilns to prepare the MgAION.

The synthesis principle of the invention is to adopt a carbon reduction nitridation synthesis process, namely, alumina is used for direct reduction nitridation, and the direct reduction nitridation is immediately combined and dissolved into magnesium Allone so as to replace expensive AlN synthesis used in the prior art. The reaction formula of the invention is as follows: wherein (g) represents a gas,(s) represents a solid, Al₂O₃Is natural bauxite, Al₂₃O₂₇N₅3.12MgO is MgAlON which is a solid solution of magnesium oxide dissolved in aluminum oxynitride. The raw materials and components of the reaction formula are as follows: (1) bauxite. Natural bauxite ore. Chemical components (mass%, the same applies below): alumina is more than or equal to 90 percent; silicon dioxide is less than or equal to 5 percent; titanium dioxide is less than or equal to 5 percent; the main lithofacies are corundum phases. (2) And (4) magnesia. Wherein the magnesium oxide is more than or equal to 97 percent. (3) The purity of the metal aluminum powder Al is more than or equal to 97 percent, and the raw material mixture ratio is as follows: 80-89% of bauxite, 3-10% of metal aluminum powder and 5-15% of magnesia. The preparation of the MgAION by using the industrial kiln can be completed by the following process; fine grinding of raw materials → proportioning according to requirements → mixing → adding of binding agent mixing → mechanical compression molding → drying → sintering and synthesis under the atmosphere of reduction and nitridation → cooling → discharging.

All raw materials are finely ground until the granularity is less than or equal to 0.08 mm; the binding agent is syrup; when the sintering atmosphere is contained, burying the sintering atmosphere in a mixture of 20-40% of coke powder, 20-40% of graphite powder and 30-50% of special-grade bauxite powder under nitrogen; the sintering temperature is 1550-1650 ℃; the sintering time is 72-110 hours. The content rate is 95.07 percentPlus or minus 3 percent and residual corundum phase 4.93 percent plus or minus 3 percent (calculated by the total amount of aluminum oxide and magnesium oxide); in addition, impurities in the raw materials form iron, silicon and titanium glassy phasesand carbonitrides. The composite phase is mainly MgAlON spinel phase (90-96%), and contains a small amount (4-10%) of corundum phase and glass phase. The content of (N) is 1.5 to 5.8%, and the content of MgO is 1.1 to 2.5% (2.5mol to 40 mol%). [ N]and MgO content can be adjusted according to application requirements. The synthetic density is 3.10-3.20 g/cm³The porosity is less than or equal to 10 percent, and the water absorption is less than or equal to 3 percent.

Example (b): see table:

furnace with a heat exchanger Number (C)	Raw material ratio (mass%)			Reducing atmosphere material (quality) ％)			Sintering Temperature (. degree.C.)	Sintering Time of day h	Synthesis of A ratio of ( ％)	Magnesium donkey Root of Longjian province Rock stone Phase (C) (％ )	Density of g/cm3
												Aluminium Alum (alum) Soil for soil	Gold (Au) Belong to Aluminium Powder	Magnesium alloy Sand	Coke (coke) Carbon (C) Powder	Stone (stone) Ink(s) Powder	Specially for treating diabetes Stage Alum (alum) Soil for soil Powder	Oxygen hole Rate of change (％
	1	80	10	10	20	30					30								1550	75	92.1	95.0	3.11
8
							2	86	3	11		25	35	40	1558	80	94.5	93.4					3.10
5
	3	84	5	11	30	20					50								1570	72	93.0	95.5	3.15
5
							4	80	5	15		40	30	30	1600	100	96.7	90.0					3.18
9
	5	89	6	5	25	40					35								1590	93	95.3	96.0	3.20
4
							6	83	9	8		35	20	45	1630	105	98.0	94 7					3.19
10
	7	82	5	13	22	40					38								1650	110	97.0	91.1	3.14
6

Claims (1)

1. An aluminum oxynitride solid solution synthesized from magnesium oxide and aluminum oxide and having a chemical formula of Al₂₃O₂₇N₅The preparation method of the MgAlON of (2.5-40 MgO) comprises the following steps of raw material fine grinding → burdening according to requirements → mixing → adding a bonding agent for mixing → machine press molding → drying → sintering synthesis under a reducing oxygen atmosphere → cooling → discharging, and is characterized in that:

a. the alumina in the raw material is selected from natural bauxite, the chemical components of the alumina are more than or equal to 90 percent by mass, the silicon dioxide is less than or equal to 5 percent by mass, the titanium dioxide is less than or equal to 5 percent by mass, and the main rock phase is corundum phase; the magnesium oxide in the magnesia is more than or equal to 97 percent by mass; the purity of the metal aluminum powder is more than or equal to 98 mass percent;

b. the raw materials are proportioned as follows: 80-89% by mass of bauxite, 3-10% by mass of metal aluminumpowder and 5-15% by mass of magnesia;

c. the reduction is carried out by adopting carbon reduction and nitrogen nitridation, namely, raw materials which are prepared according to requirements are buried in 20-40 mass percent of coke powder, 20-40 mass percent of graphite powder and 30-50 mass percent of special-grade bauxite powder and nitrogen is introduced;

d. the sintering synthesis is carried out in an industrial kiln, the sintering temperature is 1550-1650 ℃, and the sintering time is 72-110 hours;

e. the fine grinding is to grind the mixture until the granularity is less than or equal to 0.08 mm.