Method for measuring shrinkage of alumina fine powder

Abstract

The present application relates to a kind of methods for measuring the shrinkage of alumina micropowder, specific method includes: 1) the alumina micropowder is pressed into cylindrical blank with diameter L1 and height L2 by 30t±0.5t pressure;2) after the cylindrical alumina micropowder blank is dried at 110℃±5℃, it is fired in electric furnace at 1550℃±5℃, and the temperature is kept for at least 3 hours;3) the alumina micropowder blank after burning is removed, and diameter L3 and height L4 are measured again;4) the shrinkage of alumina micropowder ψ 直径 =[(L3-L1) / L1]*100, ψ 高 =[(L4-L2) / L2]*100.The method for measuring the shrinkage of alumina micropowder can distinguish active alumina micropowder and calcined alumina micropowder, provide experimental reference data by stabilizing the value of shrinkage, and has higher measurement accuracy and reliability, and has very high practical value for the performance research of alumina micropowder.

Description

TECHNICAL FIELD

[0001] The present application relates to a detection method of alumina micropowder in refractory materials for steel smelting, and particularly relates to a method for measuring shrinkage of alumina micropowder. BACKGROUND

[0002] Alumina micropowder has been widely used in the field of refractory due to its high strength, strong corrosion resistance and large hardness. There are two commonly used alumina micropowder, namely active alumina micropowder and calcined alumina micropowder. The active alumina micropowder is made by burning industrial alumina, and is a product after superfine grinding. Its performance mainly comes from its small crystal grains, large specific surface area and high surface activity. It is easy to sinter under high temperature conditions. In the structure, oxygen ions are approximately close-packed in a cubic center. Irregularly distributed in the octahedral and tetrahedral voids surrounded by oxygen ions. The calcined alumina micropowder is made of industrial aluminum hydroxide or industrial alumina as raw material, and is calcined at a proper temperature to form a crystal type stable alpha-alumina product. The calcined alumina micropowder is made of calcined alpha-alumina as raw material and is ball milled. In the structure of calcined alumina, oxygen ions are hexagonally close-packed, and Al 3+ symmetrically distributed in the octahedral coordination center surrounded by oxygen ions, and the crystal lattice energy is very large, and the melting point is very high. 3+

[0003] At present, there is no national standard for the determination of the shrinkage of alumina micropowder, and there is no unified provision. The active alumina micropowder and the calcined alumina micropowder are only distinguished by the specific surface area and the median diameter. The method is single, the sampling amount is small, it is not comprehensive, and it may increase the experimental error. In order to distinguish, the refractory material manufacturers introduce new equipment with high cost.

[0004] Therefore, there is an urgent need for a cost-controllable and reliable method for measuring the shrinkage of alumina micropowder in the current research and development. SUMMARY

[0005] The present application provides a method for measuring the shrinkage of alumina micropowder, which can distinguish between active alumina micropowder and calcined alumina micropowder, provide experimental reference data by stabilizing the shrinkage value, and has high measurement accuracy and reliability, and has high practical value for the performance research of alumina micropowder.

[0006] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0007] A method for measuring the shrinkage of alumina micropowder, the specific method comprising:

[0008] 1) The alumina micropowder is pressed into a cylindrical blank with a diameter of L1 and a height of L2 by a pressure of 30t±0.5t; ​

[0009] 2) After the cylindrical alumina micropowder body is dried at 110℃±5℃, it is fired in an electric furnace at 1550℃±5℃ for at least 3 hours;

[0010] 3) The fired alumina micropowder body is taken out, and the diameter is measured again as L3 and the height as L4;

[0011] 4) The shrinkage rate ψ of the alumina micropowder is obtained 直径 = [(L3-L1) / L1]*100, ψ 高 = [(L4-L2) / L2]*100.

[0012] When the shrinkage rate |ψ|>9, it is active alumina micropowder.

[0013] When the shrinkage rate |ψ|<5.5, it is calcined alumina micropowder.

[0014] In the above step 1), the alumina micropowder is first taken and put into a sealed bag, distilled water is sprayed, and the sealed bag is kneaded by hand until the alumina micropowder is kneaded into a block in the bag, then the sample is poured into an assembled mold and put into a tablet press for molding.

[0015] In the above step 2), the temperature is raised at a rate of 8-10℃ / min from room temperature to 1550℃, and after holding, the temperature is cooled to room temperature at a rate of 3-5℃ / min.

[0016] The present application can conveniently test the diameter L1 and the height L2 of the pressed alumina micropowder body, and after the heat treatment of step 2), the diameter L3 and the height L4 of the alumina micropowder body can also be conveniently measured, so that the shrinkage rate of the alumina micropowder can be calculated, i.e. 直径 = [(L3-L1) / L1]*100, ψ 高 = [(L4-L2) / L2]*100, The shrinkage rate of the alumina micropowder can reflect the type of the alumina micropowder, so that whether it is active alumina micropowder or calcined alumina micropowder can be distinguished by measuring the size of the shrinkage rate of the alumina micropowder, effectively solving the problem that the quality of the alumina micropowder is difficult to determine, the shrinkage rate |ψ|>9 of the active alumina micropowder, and the shrinkage rate |ψ|<5.5 of the calcined alumina micropowder, the measuring method is simple to operate, has high measurement accuracy and reliability, and has high value for the performance research of the alumina micropowder.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] The measuring method of the present application is simple to operate, and can conveniently distinguish active alumina micropowder and calcined alumina micropowder by measuring the shrinkage rate of the alumina micropowder, providing important and accurate reference data for its use. DETAILED DESCRIPTION

[0019] The specific embodiments of the present application are further described below in conjunction with examples:

[0020] The method for measuring the shrinkage of the alumina micropowder of the present application comprises:

[0021] Step one: take the alumina micropowder, put it into a sealed bag, spray distilled water in small amounts multiple times, and knead the sealed bag with hands until the alumina micropowder can be kneaded into a block in the bag and does not break when unfolded.

[0022] Pour the sample into the assembled cylindrical hollow mold, compact it using a cylindrical solid mold, and then put it into a tablet machine.

[0023] Use the tablet machine to press the experimental body under a pressure of 30t, and keep it for 30s, and then take out the body.

[0024] Draw a straight line on the alumina micropowder body, and the two points where the straight line intersects with the circle are marked points, marked with chrome green, and the length between the two points is the diameter L1; for example, in order to facilitate the measurement, mark the two points of the alumina micropowder body, and measure the height L2 at one of the marked points of the alumina micropowder body.

[0025] Step two: put the alumina micropowder body to be measured for shrinkage into a high-temperature electric furnace at 1550℃ and heat for three hours.

[0026] Step three: after taking out the cooled alumina micropowder body from the electric furnace, find the position marked with chrome green, and measure the diameter L3 and the height L4 again.

[0027] Step four: obtain the shrinkage of the alumina micropowder:

[0028] ψ 直径 = [(L3-L1) / L1]*100;

[0029] ψ 高 = [(L4-L2) / L2]*100;

[0030] Wherein, ψ 直径 , ψ 高 The unit of is %.

[0031] Thus, in the determination method, since the worker can conveniently mark two points above the alumina micropowder, the two points where a straight line passing the center of the circle intersects with the circle can be taken as the mark points, the diameter length L1 between the two points on the alumina micropowder blank before heat treatment and the height L2 can be measured, and after heat treatment, the length L3 between the two mark points and the height L4 of the same mark point on the alumina micropowder blank can be conveniently measured, so that the diameter length of the same alumina micropowder blank before and after heat treatment can be obtained, and further, the shrinkage of the alumina micropowder can be calculated, that is, ψ 直径 = [(L3-L1) / L1]*100, and similarly, ψ 高 = [(L4-L2) / L2]*100. The shrinkage of the alumina micropowder blank can reflect the type of the alumina micropowder, so that whether the alumina micropowder is active or calcined can be distinguished by measuring the shrinkage of the alumina micropowder, the shrinkage of the active alumina micropowder |ψ|>9, and the shrinkage of the calcined alumina micropowder |ψ|<5.5 (a value less than 9 and greater than 5.5 is considered to be an unqualified sample, and it is suspected that the two are mixed with each other). The determination method is simple in operation, large in numerical difference, easy to distinguish, can be fired together with the same temperature experimental products in the normal cycle, saves the cost of the factory, has high reliability, and has high value for the performance research of the alumina micropowder.

[0032] Further, in order to more easily measure the length between the two reference lines of the alumina micropowder before and after heat treatment, the diameter of the mold selected in the determination method of the present application is 50 mm, which can well fix the alumina micropowder, so as to more conveniently and accurately measure.

[0033] In addition, in the determination method of the shrinkage of the alumina micropowder of the present application, in step two, the predetermined heat treatment of the alumina micropowder can be realized by the following way, that is, the alumina micropowder is put into a 1550℃ high-temperature electric furnace, and is heat treated according to a predetermined fixed heating curve, so that the alumina micropowder can be uniformly heated, and good shrinkage can be generated, so that more accurate shrinkage data can be obtained.

[0034] Further, the alumina micropowder can be put into a hearth, heated to a set temperature according to a set heating rate, then heat preserved for a set time to uniformly heat the alumina micropowder, and then cooled to room temperature according to a set cooling rate, more specifically, the alumina micropowder can be put into a hearth, heated to 1550℃ from room temperature according to a heating rate of 8-10℃ / min, then heat preserved for 3 hours to uniformly heat the alumina micropowder, and then cooled to room temperature according to a cooling rate of 3-5℃ / min.

[0035] Table 1 is 10 sample cases of the shrinkage of the active alumina micropowder measured by the method of the present application;

[0036] Table 2 is a case of 10 samples of the shrinkage of the calcined alumina fines measured by the method of the present application.

[0037] Table 1

[0038]

[0039]

[0040] Table 2

[0041]

[0042]

[0043]

Claims

1. A method for measuring the shrinkage of an alumina micropowder, characterized by, The specific method comprises: 1) The alumina powder is pressed into a cylindrical body with a diameter of L1 and a height of L2 by a pressure of 30t±0.5t; 2) After the cylindrical alumina powder body is dried at 110℃±5℃, it is calcined in an electric furnace at 1550℃ for at least 3 hours; From room temperature, the temperature is raised to 1550℃ at a rate of 8-10℃ / min, and after holding, the temperature is cooled to room temperature at a rate of 3-5℃ / min; 3) The calcined alumina powder body is taken out, and the diameter is measured again as L3 and the height as L4; 4) Shrinkage ψ of alumina micropowder 直径 = [(L3 - L1) / L1] * 100, ψ 高 = [(L4 - L2) / L2] * 100; When the shrinkage |ψ|>9, it is active alumina powder; When the shrinkage |ψ|<5.5, it is calcined alumina powder; Values less than 9 and greater than 5.5 are considered to be unqualified samples, and are mutually doped.

2. The method for measuring the shrinkage of alumina fine powder according to claim 1, characterized by, In the above step 1), the alumina powder is first put into a sealed bag, distilled water is sprayed, and the sealed bag is kneaded by hand until the alumina powder is kneaded into a block in the bag, then the sample is poured into the assembled mold and placed in a tablet press for molding.

Images