KR950007175B1 - Al2o3-tic powder process of self-propagating high temperature synthesis - Google Patents

Abstract

The manufacturing method for Al2O3-TiC composite powders saves energy cost and produces the product with high purity by using self-propagating high temperature synthesis. The method comprises (A) mixing the powders of TiO2, Al and C with a fixed mole fraction in a ball mill; (B) making pellets by forming pressure of 4 to 14 ton per cm2; (C) igniting the powders in the reactor under argon gas atmosphere.

Description

Method for preparing Al2O3-TiC composite powder by auto combustion

1 is a schematic diagram of a manufacturing process according to the present invention.

2 is a schematic diagram of an SHS reactor.

3 shows the effect of fixing the molar ratio of TiO ₂ : C to 3.3: 3.0 and the Al molar ratio on the X-ray diffractogram of the reaction product.

4 shows the effect of fixing the molar ratio of TiO ₂ : Al to 3.0: 4.0 and the C molar ratio on the X-ray diffractogram of the reaction product.

5 shows the effect of the molding pressure on the X-ray diffractogram of the reaction product by fixing the molar ratio of TiO ₂ : Al: C to 3.0: 4.0: 3.0.

* Explanation of symbols for main parts of the drawings

1: vacuum pump 2: pressure gauge

3: turnsten filament 4: cooling device

5: sample 6: power

7: heat-resistant glass 8: infrared thermometer

The present invention relates to a method for producing Al ₂ O ₃ -TiC cemented carbide material from TiO ₂ by a self-propagating high temperature synthesis (SHS) method.

More specifically, the present invention using TiO ₂ , Al and C in a constant molar ratio Al ₂ O ₃ -TiC by the auto-burning reaction method is excellent in mechanical thermal shock resistance, has a high temperature strength, high temperature cutting is possible, Due to its toughness, it is used for machining hard and hard materials, cast iron and steel, and for medium cutting and finishing. Since their demand is rapidly increasing, it is necessary to manufacture them at low cost.

Various methods for preparing Al ₂ O ₃ and TiC are known, but these methods are disadvantageous because they require a high temperature reactor or a vacuum reactor and must supply energy. Therefore, it has been an important task to develop a method for producing Al ₂ O ₃ -TiC economically in the same reactor.

The inventors believe that the auto combustion method is the most promising means to solve these problems, and while studying the method, when TiO ₂ is used as the raw material and Al and C are used in the known auto combustion method, Al ₂ It was found that O ₃ -TiC can be obtained very economically.

Accordingly, the present invention provides a method for producing Al ₂ O ₃ -TiC by the auto combustion method using TiO ₂ , Al and C in a constant molar ratio. More specifically, the present invention is mixed with TiO ₂ : Al: C in a molar ratio of 3.0: (3.4-4.6) (2.4-3.0) and then compressed to a molding pressure of ⁴ ~ 14 tons / cm ³ and in a self-burning reactor Provided is a method for producing an A1 ₂ O ₃ -TiO composite powder characterized by ignition in an argon atmosphere.

The natural combustion reaction method used in the present invention refers to a method of synthesizing various materials using its own heat of chemical reaction without supplying energy from the outside by using a solid-solid chemical reaction in general as an exothermic reaction.

According to the present invention, a method for preparing Al ₂ O ₃ -TiC using the autogenous combustion reaction method is as follows.

Scheme 1

3TiO ₂ + 4Al + 3C → 2Al ₂ O ₃ + 3TiC

In the present invention, the particle size of the raw powder is used TiO ₂ 0.3μm, Al 5.0μm and C 0.5μm, the purity of these is 98.56% TiO _2, 99.14% Al and 99.90% C. In addition, the chemical composition of the raw powder used in the present invention is as follows.

TABLE 1

The table shows the amount of impurities present in the raw material powder. In the experiment, powders having low purity are used. This is to confirm that the product is higher in purity than the reactant through the auto-burning reaction.

If the purity of the raw material powder is increased, the purity will be increased.

Meanwhile, the chemical composition of Al ₂ O ₃ -TiC synthesized by the autogenous combustion reaction according to the present invention is Si 0.052% by weight, Fe0.002% by weight, Cu 0.001% by weight, Ca 0.003% by weight, K 0.002% by weight, P It consists of 0.001 weight% and Cr (not detected).

Since the impurities are volatilized during the combustion process of the final product prepared according to the method of the present invention, when the complete combustion reaction is completed, high purity of 99.939 wt%

The manufacturing process of Al ₂ O ₃ -TiC according to the present invention is schematically shown in FIG. The auto-combustion reactor can be called a auto-combustion device in any form as long as it produces a device that ignites the specimen in a state where the reactor can be vacuum or gas atmosphere. However, the autogenous combustion reactor used in the present invention, as schematically shown in FIG. 2, was made into a cylinder having a diameter of 30 cm and a length of 40 cm, and then allowed to inject vacuum and argon gas, and to ignite the sample. After connecting the power, the heat of ignition was used as the resistance heat of tungsten wire. The size of the autocombustion reactor is not limited, and the size of the autocombustion reactor can be made large or small depending on the size of the specimen to be manufactured.

According to FIG. 3, the molar ratio of TiO ₂ : C is fixed to 3.0: 3.0 and the molar ratio of Al is changed from 3.4 to 4.6, which is most suitable at 4.0 moles, which is the stoichiometric ratio of Al.

In FIG. 4, when the molar ratio of TiO ₂ : Al is 3.0: 4,0, the molar ratio of C is 2.4 to 3.0 moles is most suitable for combustion synthesis by changing the molar ratio of C from 2.2 to 3.4. In addition, the crystal structure of the final product according to the change in the molding pressure can be obtained pure Al ₂ O ₃ -TiC was not affected by the change in the molding pressure, but the propagation speed was decreased by the increase of the molding pressure.

5 is a photograph observing the product Al ₂ O ₃ -TiC according to the change in the molding pressure with an electron microscope. The particle size of the final product is 4 to 10μm and it can be seen that the particles are larger as the molding pressure increases. The reason that the particles became larger as the molding pressure increased was that the propagation speed was decreased due to the increase in the molding pressure, and the propagation speed was reduced, so that the high temperature heat could be maintained in the specimen during the synthesis reaction. Because.

In the present invention, the molding pressure is 4 to 14 tons / cm ² is good. If the specimen pellets are manufactured at 4 tons or less, the pellets are easily broken due to the low pressure and cannot be used for the experiment.

The present invention does not require a high temperature reactor, the manufacturing process is simple, the reaction proceeds automatically by the self-heating amount to save energy and also provides the advantage that the purity of the product is higher than the purity of the reactants. In addition, the present invention provides the advantage that the reaction itself starts from the oxide can be synthesized in the air without a vacuum reactor.

Hereinafter, although an Example demonstrates this invention, the scope of the present invention is not restrict | limited to these Examples.

EXAMPLE

As a raw material, a ball mill was used with a molar ratio of TiO ₂ (commercially available from Titanium Powder Co., Ltd.), Al powder (commercially available from Changsung Co., Ltd.), and C (reagent), respectively, in a molar ratio of 3.0: (3.4-4.6): (2.4-3.0). To mix for at least 5 hours. Pressure (4 to 14 tons) is applied to the mixed powder to make pellets 15 mm in diameter and 15 to 20 mm in height. The shaped pellets are ignited in an argon atmosphere in a autocombustion reactor. The crystal structure was examined by X-ray and the microstructure was observed by scanning electron microscopy (SEM). The sample showed crystallinity and the particles had particle size distribution of about 4-10rm. In addition, when the sample was measured by atomic absorption spectrometer, it was found to be 99.939% by weight of high purity powder.

Claims (2)

TiO _2, then a solution of the Al and C at a constant molar ratio of 4 to 14 ton / cm is created and ^second pellets to the molding pressure, with the pellet in an argon atmosphere in a rotating combustion reactor Al ₂ O characterized by the Sikkim ignition ₃ -TiC composite powder production method. The method of claim 1, wherein TiO ₂ : Al: C is present in a molar ratio of 3.0: (3.4-4.6): (2.4-3.0).