JPH0532999U - Tray for degreasing and sintering of metal powder compacts - Google Patents

Abstract

(57) [Abstract] [Purpose] Degreasing efficiency can be prevented by evaporation of impurities in degreasing and sintering tray components during degreasing and sintering, metal powder compacts, and contamination by vapor deposition of impurities on furnace components, and degreasing efficiency It is an object of the present invention to provide a degreasing / sintering tray which can improve the heat treatment efficiency and can reduce the processing cost by improving the thermal efficiency for sintering. [Structure] The degreasing and sintering tray is made of a material having a vapor pressure at the sintering temperature of the compact of 1 × 10 −4 Torr or less and a main material having a purity of 95% or more, and a porosity of 10 or less. %
It is characterized in that it is formed as described above.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 In this invention, for example, a metal powder compact formed by kneading a metal powder of Fe-Co (-Ni) alloy with a binder and molding it into a desired shape is placed, degreased, and further vacuum sintered to burn a magnetic material of a printer head. The present invention relates to a degreasing and sintering tray used for obtaining products.

[0002]

[Prior Art]

 Conventionally, in order to obtain a sintered body from a metal powder compact based on the powder metallurgy method, an organic binder contained in the compact for the purpose of forming a metal powder compact is inert in a degreasing furnace. In a gas or reducing gas atmosphere or under reduced pressure, it is heated and decomposed to remove it, and then degreased, and then the molded body formed of only metal powder is placed in a sintering furnace in an inert gas or reducing gas atmosphere. A method of heating and sintering in medium or under reduced pressure is used.

In this method, a tray for mounting and holding the compact in a degreasing furnace or a sintering furnace is required, and a ceramic base plate or powder is mainly used. However, the use of ceramic powder is difficult to handle because there is a problem that the ceramic powder adheres to the metal powder molded body. Therefore, it is common to use a ceramic base plate that is easy to handle as a tray.

[0004]

[Problems to be solved by the device]

 However, depending on the composition of the ceramic base plate or its purity, evaporation and decomposition of the components that make up the base plate under the environment of degreasing and sintering in an inert gas or reducing gas atmosphere or under reduced pressure. Occurs. As a result, vaporized and decomposed components are vapor-deposited on the molded body and furnace wall during degreasing and sintering, resulting in a large number of defective products and, at the same time, significantly lowering the furnace performance.

Degreasing is intended to remove the organic binder contained for forming a metal powder compact from the surface of the compact by heating and decomposing it. In the part where the degreasing is done, the tray for degreasing becomes an obstacle and prevents the flying of the decomposed binder. For this reason, the degreasing efficiency remarkably decreases, and in some cases, local decomposition of the organic binder causes cracks and the like in the molded body.

Further, in sintering, if a dense base plate made of ceramic is used as a tray for sintering, since the specific gravity of the tray is large, the number of charging into the sintering furnace can be suppressed. The large heat capacity of the tray results in high power consumption for the sintering process. Since the thermal shock resistance of the tray is weak, the temperature rising / falling speed from room temperature to the sintering temperature must be suppressed, and there is a problem that a long processing time is required.

The present invention has been made in order to solve the above-mentioned problems, and is to evaporate and decompose the components of the degreasing and sintering tray during degreasing and baking, and the metal powder compact and the in-furnace structure. The first purpose is to prevent the contamination of the product due to the vapor deposition of impurities, and the porosity of the tray is set to 10% or more so that the organic binder contained in the molded body is thermally decomposed in the degreasing furnace. A second purpose is to remove the organic binder also from the contact portion between the molded body and the tray when removing it by increasing the degreasing efficiency. A third object is to improve the thermal efficiency for sintering and reduce the processing cost by using a tray having a porosity of 10% or more.

[0008]

[Means for Solving the Problems]

 In order to achieve this object, the tray for degreasing and sintering metal powder compacts of the present invention has a metal powder compact formed by kneading metal powder with a binder and shaping it into a desired shape, degreasing it, and further vacuum baking. A degreasing and sintering tray used for binding to obtain a fired product, wherein the vapor pressure at the sintering temperature of the compact is 1 × 10 -4 Torr or less, and the purity of the main material is 95% or more. It is characterized in that it is made of the above material and is formed so that the porosity is 10% or more. Here, the vapor pressure is set to 1 × 10 -4 Torr or less, because it is economically unprofitable for a vacuum device with a vacuum degree of 1 × 10 -4 Torr or less, and it is considered that a material that can withstand this vacuum degree is sufficient. This is because the. The material, purity, porosity, etc. of the tray will be described in detail in Examples.

[0009]

[Action]

 According to the degreasing / sintering tray for a metal powder compact of the present invention having the above-mentioned configuration, the porosity of the tray is 10% or more during the degreasing process, and the tray has a porous property, so that the tray does not come into contact with the tray. From the aspect, the binder is decomposed and removed, the binder removal efficiency is improved, and the time required for degreasing is shortened.

Further, during the sintering process, the tray is chemically stable against the in-furnace conditions, can prevent evaporation and decomposition of the components constituting the tray, and can also form a metal powder compact by evaporation and decomposition. Also, a sound degreased body and a sintered body can be obtained without depositing impurities on the furnace components.

Further, since the heat capacity of the tray is small and the tray is strong against thermal shock and is lightweight, the energy required to raise the temperature of the tray itself is small, the power consumption is small, and a large amount of processing can be performed in a short time, so operating costs are high. Significantly reduced. In addition, damage to the tray itself is avoided and it can withstand repeated use.

[0012]

【Example】

 An embodiment embodying the present invention will be described below with reference to the drawings.

Example 1 As a metal powder compact, an Fe—Co (—Ni) alloy powder and an organic binder were kneaded and molded by an injection molding machine. The compounding ratio of the organic binder was set to 40% in consideration of injection moldability. Three types of degreasing / sintering trays were prepared as shown in Table 1, and as shown in FIG. 1, molded articles were arranged on the trays for degreasing and sintering.

[0014]

[Table 1]

FIG. 1 shows a sintering furnace. A furnace floor 4 is provided in the sintering furnace 3, and molded articles 2a and 2b are placed on degreasing and sintering trays 1a and 1b that are stacked on the furnace floor 4, respectively. In the figure, the difference between the molded bodies 2a and 2b is whether or not the upper side of the molded bodies is shielded by the degreasing and sintering tray. Although degreasing is not shown, the temperature was raised to 450 ° C at 10 ° C / h by a degreasing furnace and kept for 1 hour for cooling, during which N2 gas was flowed at a flow rate of 20 l / min. After degreasing, take out the tray and the compact from the furnace, transfer them to the sintering furnace as they are, raise the temperature to 1400 ° C at 400 ° C / h, hold for 2 hours, and cool to room temperature in 3 hours. During this time, the pressure inside the furnace was maintained at 5 Torr by Ar gas. The results are shown in Table 2.

[0016]

[Table 2]

Under the degreasing conditions of this example, no abnormality was observed after degreasing in the molded body placed on any of the trays A, B, and C, but the surface of the sintered body after sintering was As a result of analysis by EPMA, Si was detected only on the tray B placed on a tray B containing a large amount of SiO2. In addition, a difference in the amount is recognized between the molded products 2a and 2b, and the number of the molded products whose upper portion is shielded by another tray is smaller. These are the ones in which SiO2 in the tray decomposes and evaporates and scatters in the furnace, resulting in vapor deposition on the surface of the compact. Therefore, the rate of vapor deposition of the molded body 2b, that is, the one whose upper side is shielded by another tray is reduced, so that the surface deposits of the molded body 2b are larger than that of the molded body 2a.

Example 2 A metal powder compact was prepared in the same manner as in Example 1, and the degreasing and sintering trays A and C in Table 1 were used to investigate the degreasing efficiency. The degreasing treatment was performed at three different heating rates up to 450 ° C: 10 ° C / h, 20 ° C / h, and 30 ° C / h, and the defective state was examined by visual inspection after degreasing. Table 3 shows the results of the number of defects after degreasing.

[0019]

[Table 3]

At the heating rate of 10 ° C / h, neither tray A nor C had any defect, but at 20 ° C / h, cracks were observed in the molded product on tray C. Tray A showed a defect at 30 ° C / h. This is because the tray A has higher porosity than the tray C, and thus the organic binder decomposed during degreasing was smoothly degreased through the pores of the tray from the molded body. As a result, it is possible to increase the rate of temperature rise during degreasing by using a tray with high porosity, and it is clear that degreasing can be performed efficiently in a short time. Further, economically, it is necessary to have a porosity of at least 10% or more because a temperature rising speed of 20 ° C or more is required.

Example 3 A metal powder compact was prepared in the same manner as in Example 1, and the degreasing and sintering trays were examined for thermal shock resistance using A and C in Table 1. As shown in Table 4, the sintering conditions were set in three ways, and the molded body was placed on each tray and stacked in four stages.

[0022]

[Table 4]

The pressure in the furnace was Ar gas of 5 Torr in all steps. Table 5 shows the results of the degreasing after sintering and the number of broken sheets in the sintering tray.

[0024]

[Table 5]

In the highly porous tray A, two pieces were partially cracked under the condition 3, that is, the temperature rising speed up to 1400 ° C 800 ° C / hr. And the cooling time 3hr. However, no abnormality was found in the sintered body. On the other hand, in the case of tray C, which has a low porosity, a plurality of sheets were completely cut and damaged under the condition 2, that is, the temperature rising speed up to 1400 ° C is 600 ° C / hr. And the cooling time is 5hr. The sintered body that had been placed had also undergone abnormal deformation. As a result, if the tray has low porosity, its thermal shock resistance becomes weak, and its strength against a sudden temperature change decreases, and it is thought that the tray was cracked and damaged. By using a tray with high porosity, it is possible to perform sintering at a rapid heating rate as a condition, and it can be seen that processing can be performed in a short time.

It should be noted that although alumina Al 2 O 3 is used as the tray material in the above embodiment, it is not limited to this and, for example, boron nitride BN or the like can of course be applied. Needless to say, the atmosphere gas at the time of sintering can be applied not only to the inert gas such as Ar gas shown in the above embodiment, but also to an atmosphere such as a reducing gas or an oxidizing gas.

[0027]

[Effect of the device]

 As is clear from the above description, according to the degreasing and sintering tray of the present invention, in the degreasing and sintering of the metal powder compact, the degreasing and sintering components are vaporized and decomposed to evaporate and decompose. It is possible to obtain a sound degreased body and a sintered body without any contamination of the formed body and the components in the furnace due to the vapor deposition of impurities. In addition, when the organic binder is removed during degreasing by adding porosity to the tray, the organic binder in the molded body is not only removed from the surface not in contact with other objects but also from the surface in contact with the tray. Since it is heated and decomposed through the pores and discharged from the inside of the molded body, the degreasing efficiency can be improved, and since it is discharged from the molded body in a short time, the degreasing efficiency can be improved and cracks and the like in the molded body can be obtained in a short time. Can be degreased without causing defects. In addition, the heat capacity of the equipment is smaller than that of a dense tray, and because it is strong against heat shock and lightweight, the power consumption of the sintering furnace can be reduced, and a large amount of processing can be done in a short time, so operating costs are high. It can be greatly reduced. Moreover, since it is not necessary to replace the tray itself in each process of degreasing and sintering, it contributes to the improvement of workability, and since it can be used repeatedly, its economic efficiency is extremely high. Therefore, applying it to the manufacture of magnetic materials for printer heads, as in the above-described embodiment, provides high-quality products and contributes to improving the performance of various information equipment products.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a sintering furnace used in the present invention and a degreasing and sintering tray used therein.

[Explanation of symbols]

 1a, 1b Degreasing and sintering tray 2a, 2b Metal powder compact 3 Sintering furnace

Claims (1)

[Scope of utility model registration request] 1. A degreasing / sintering tray used to obtain a fired product by placing a metal powder compact formed by kneading a metal powder with a binder and shaping the powder into a desired shape and further vacuum sintering. And the vapor pressure at the sintering temperature of the molded body is 1 × 10 −4 Torr or less, and the main material is made of a material having a purity of 95% or more, and the porosity is 10% or more. A tray for degreasing and sintering metal powder compacts, which is characterized in that