JPH0368704A - Sheet for burning - Google Patents

Abstract

PURPOSE:To form a sheet, which is difficult to break when used to burning of a burning material having heavy weight by applying high m.p. ceramic powder layer on surface of an organic film, which is heat decomposed at the time of heating under vacuum, through organic adhesive layer containing the specific content of carbon powder. CONSTITUTION:On the surface of organic film 1 (polyvinyl alcohol, etc., having about 40mu thickness), which heat-decomposition is generated at the time of heating under the vacuum or non-oxidizing atmosphere, the high m. p. ceramic powder layer 3 (Al2O3, ZrO2, etc., having about 10 - 200mu average particle diame ter) is applied through the organic adhesive layer 2 (acrylic series adhesive, etc.) containing 2 - 70 wt.% carbon powder 4 to manufacture the sheet for burning. This sheet is spread on the carbon plate 6, and on the upper face thereof, the body 5 to be burnt of cemented carbide is laid and at the time of burning under the vacuum, the organic film 1 and organic adhesive layer 2 is heat decomposed, and the high m.p. ceramic powder layer 3 and carbon powder 4 remains as layer-state, and the burnt body 5 is held to non-contacting condition to the carbon plate 5 and melt-sticking is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to improvement of a firing sheet used for firing cemented carbide.

(Prior art) It has been known for a long time that when firing cemented carbide, a firing sheet is placed between the carbon plate serving as the base and the cemented carbide to prevent mutual welding, etc. The inventors have already proposed the structure of a firing sheet for this purpose in Japanese Patent Laid-Open No. 63-319145. The firing sheet described in this publication has ceramic powder held on the surface of an organic film by an organic binder, and is highly effective in preventing scratches and improving flatness when firing ordinary cemented carbide. did.

However, if this firing sheet is used when firing a large cemented carbide fired body with a weight of 3.0 kg or more per piece, the weight per unit area of the firing sheet becomes large, so the fired body The sheet is easily damaged due to heat shrinkage,
In addition, for ring-shaped fired bodies, sheet deviation occurs toward the center of the ring, and when the fired body comes into contact with the carbon plate, components such as Co from the carbon plate enter the fired body. There were drawbacks.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems and makes it possible to prevent sheet breakage even when firing a cemented carbide fired body having a large weight per unit area. , was completed in order to provide a firing sheet that can prevent troubles caused by contact between the fired body and the carbon plate.

(Means for Solving the Problems) The present invention, which has been made to solve the above-mentioned problems, has a method of adding 2 to 70% of It is characterized by coating a high melting point ceramic powder layer through an organic adhesive layer containing % of carbon powder.

(Example) Next, the present invention will be described in more detail with reference to the drawings. Note that the drawing shows the firing sheet enlarged in the vertical direction.

In the figure, (1) is an organic film, (2) is an organic adhesive layer formed on the surface thereof, and (3) is a high melting point ceramic powder layer held by the organic adhesive layer (2). The organic film (1) has the property of being thermally decomposed when fired at a temperature of 500°C or less in vacuum or in a non-oxidizing atmosphere (neutral or reducing atmosphere), such as polyvinyl. For example, a material having a thickness of about 40 μm and made of a material such as alcohol or polyvinyl alcohol can be used.

The organic adhesive N (2) is made of, for example, an acrylic adhesive, and in the present invention, carbon powder (4) is contained therein in an amount of 2 to 70% by weight. This carbon powder (4) improves the slipperiness between the organic film (1) and the high melting point ceramic powder layer (3) during firing, and causes the sheet to shrink due to shrinkage of the fired body (5) and shrinkage of the sheet for firing. This is to prevent damage, and if carbon powder (4) is less than 2%, sufficient effect cannot be obtained, and 70%
%, the adhesive force of the organic adhesive layer (2) decreases and the ability to hold the high melting point ceramic powder layer (3) gradually decreases.

The high melting point ceramic powder layer (3) is Alzol, ZrJ
,AIN, BN, SiC, Si, N4, Mg0-
In addition to powders such as Al□01, powders such as ferrite can be used, and the average particle size is 10 to 200 am.
It is preferable to set it as approximately.

(Function) The firing sheet of the present invention, which has been bottomed in this way, is spread on a carbon plate (6) as shown in the figure, and a cemented carbide fired body (5) is placed on top of the carbon plate (6), for example, in a vacuum furnace. During firing, the organic film (1) and organic adhesive N (2) are thermally decomposed, leaving only the high melting point ceramic powder layer (3) and carbon powder (4). remains in a layered manner. These keep the fired body (5) out of contact with the carbon plate (6) and prevent welding.

In particular, in the present invention, the organic adhesive layer (2) has a
% of carbon powder (4), the carbon powder (4) remaining in layers significantly improves the slipperiness and prevents damage to the firing sheet even when the weight of the fired body (5) is heavy. It can be prevented. Also, this carbon powder (4
) is the CO component fired body (5) inside the carbon plate (6)
It has the effect of preventing infiltration into the sintered body (5), and can prevent the contact surface of the sintered body (5) with the sintering sheet from turning into a liquid phase. Furthermore, by incorporating this carbon powder (4) into the organic adhesive layer (2), shrinkage of the firing sheet itself during firing can be suppressed, so damage to the firing sheet can be more reliably prevented. Become.

Since the sheet of the present invention has a uniform thickness and a smooth surface, it is difficult to cause waviness or pinholes in the fired product.
Moreover, since it is sufficient to simply sandwich it between the lower surfaces of the fired body, there is an advantage that no trouble is required for firing.

Note that the firing sheet of the present invention and the above-mentioned JP-A-63-3
Using the baking sheet described in No. 19145, the outer diameter is 3.
12 pieces of abrasion-resistant and impact-resistant cemented carbide with a diameter of 20 m, an inner diameter of 100 wa, a thickness of lOloll, and a weight of 10.8 kg.
Vacuum degree 10-'torr, baking temperature 1350°
It was fired in a vacuum furnace of C. As a result, the properties of the fired products were good both when using the conventional firing sheet and when using the firing sheet of the present invention, but when using the conventional firing sheet, the firing Carburization was observed in 3 out of 12 pieces due to breakage of the sheet, and high melting point ceramic powder was found to be attached to the fired product, although it could be easily removed. On the other hand, when the firing sheet of the present invention was used, no carburization was observed among the 12 sheets, and there was no adhesion of high melting point ceramic powder. Furthermore, when conventional firing sheets were used, dents of about 0.2 to 0.3 m were formed on the bottom surface of the fired product, but according to the present invention, there are almost no dents, and even if there are, the dents are only 0.1 as. It was no more than the following.

(Effects of the Invention) As explained above, the sheet for bottom pits of the present invention is suitable for firing cemented carbide in a vacuum or the like, and in particular, by incorporating carbon powder into the organic adhesive layer. It is possible to prevent damage to the sheet, prevent contact between the fired body and the carbon plate, and reliably prevent carburization. Therefore, the sheet for bottom pits of the present invention will greatly contribute to the industry, especially as it can be used to sinter cemented carbide, which has a large weight per unit area.

[Brief explanation of drawings]

The drawings are cross-sectional views showing embodiments of the present invention. (1): Organic film, (2): Organic adhesive layer, (3
): High melting point ceramic powder layer, (4): Carbon powder.

Claims (1)

[Claims] An organic adhesive layer (2) containing 2 to 70% by weight of carbon powder (4) is applied to the surface of an organic film (1) that can be thermally decomposed when heated in vacuum or in a non-oxidizing atmosphere. A firing sheet characterized by being coated with a high melting point ceramic powder layer (3).