JP2019069877A - Sintering tray - Google Patents

Abstract

To provide a sintering tray capable of preventing damage such as cracking and to prevent defects such as shape defects of a sintered body.SOLUTION: This invention provides a sintering tray which is made of a flexible ceramic, in particular, aluminium titanate, and the sintering tray 2 is used for placing a green compact 3 thereon in the sintering process. The green compact 3 is taken out from a heating furnace as a sintered body after passing predetermined processes such as heating in the furnace in a state of being placed on the tray 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sintering tray.

  The powder metallurgical product can be obtained by pressing the alloy powder in a pressing process to form a green compact, and then sintering the green powder in a state where the green compact is placed on a tray in the sintering process.

  The sintering tray used in the above-mentioned sintering step causes cracks in the product when it is placed or when it is sintered, which causes shape defects, flaws, and structure defects of the product. Then, the invention which prevents the crack of such a tray for sintering is already made.

  For example, in patent document 1, the invention which prevents the crack of a tray is disclosed by providing many hollows which are not penetrated to the tray in the thickness direction. Moreover, what formed the film of the oxide in the surface of the base material which consists of a carbon material on the surface as a tray for sintering is disclosed (for example, patent document 2).

Japanese Patent Application Laid-Open No. 9-89469 JP 2008-38228 A

  In the invention of Patent Document 1, when a dedicated mold is required to mold the tray, or when a depression is formed on the mounting surface of the green compact, the green compact is not mounted on the tray at the depression. , There was a problem that the shape accuracy is deteriorated. Further, in the invention of Patent Document 2, there has been a problem that the film on the surface peels off from the base material due to physical impact, or the film peels off also due to the difference in the thermal expansion coefficient at the time of sintering.

  From such circumstances, the present invention aims to prevent breakage of the sintering tray such as cracks and prevent defects such as shape defects of the sintered body.

  In order to solve the above-described problems, the present invention is characterized in that the sintering tray is formed of a flexible ceramic.

  The sinter tray of the present invention is sinterable when physical force is applied to the surface of the sinter tray, such as placing the green compact on the sinter tray by having flexibility. The tray can be elastically deformed to absorb its force, and breakage such as cracking can be reduced as much as possible.

  Aluminum titanate can be used for ceramics as said sintering tray. Thus, the sintering tray can be made flexible.

  As described above, according to the present invention, it is possible to realize a sintering tray which is resistant to physical impact and less likely to be broken such as a crack.

It is sectional drawing which shows the state which mounted the green compact on the tray.

  In the present embodiment, the sintering tray is formed by the following method. The sintering tray of the present embodiment is a tray for mounting and sintering the green compact when the green compact is compacted.

First, a binder for molding and ethanol are added to a predetermined proportion of raw material powder, mixed by a ball mill, and granulated to 50 to 80 μm by a spray dryer. The proportion of raw material powder is as shown in Table 1 below, and the proportion of Al ₂ O ₃ is the largest, and 55 to 60 [wt%] accounts for more than half of the whole, and TiO ₂ is 35 to 40 [wt%] , 5 [wt%] SiO ₂ is included. Further, as each of the above-mentioned raw materials, for example, those manufactured by High Purity Chemical Laboratory Co., Ltd. were used.

The powder obtained by the above-mentioned processing is uniaxially press-formed and then subjected to CIP treatment to obtain a green compact. The green compact was heat treated at 600 ° C. to remove the binder, and then sintered in the air at 1600 ° C. to 1700 ° C. for 8 to 16 hours. Thus, a ceramic tray made of aluminum titanate (Al ₂ TiO ₅ ) can be obtained. The sintering tray has flexibility by being made of aluminum titanate, and the flexibility can provide impact resistance described later.

  The contents of the evaluation test of the durability in the sintering step and the results thereof will be described below for the sintering tray of the present embodiment described above. As the tray of the embodiment, one obtained by cutting the ceramic tray manufactured by the above method into a substantially rectangular shape having a size of about 110 × 110 × 5 [mm] and polishing the surface thereof is used. .

  Moreover, an alumina tray (comparative example 1) and a thermal spraying tray (comparative example 2) are respectively used as a comparative example. Comparative Example 1 is an alumina tray having a size of about 110 × 110 × 5 [mm]. In Comparative Example 2, alumina was sprayed on the surface of a carbon plate, the thickness of the sprayed film was 300 to 400 μm, and the size of the entire tray was about 120 × 120 × 5 mm. The thermal spray film is formed on the mounting surface on which the green compact is to be mounted.

  As a method of durability evaluation, as shown in FIG. 1, the tray 1 is placed on the carbon plate 2. Then, the green compact 3 of the metal powder formed in a ring shape is placed on the tray 1. In this state, the tray 1 is put into the heating furnace by the tray pusher, and heat treatment is performed. In the case of Example 1 and Comparative Example 1, as shown in FIG. 1, the tray 1 loaded with the green compact 3 is placed on the carbon plate 2 and introduced into the heating furnace. Further, in Comparative Example 2, the carbon plate 2 is not provided, and the tray 1 carrying the green compact 3 is put into the heating furnace.

The metal powder used as the raw material of green compact is iron-type powder. The green compact of the metal powder has an outer diameter of about 100 mm and an inner diameter of about 80 mm, a thickness of about 6 mm, and a density of about 6.8 (g / cm ³ ). The green compact introduced into the furnace is preheated at a temperature of 800 ° C. for 2 hours and then heated at a temperature of 1250 ° C. for 2.5 hours, and then 0.1 to 3.0 (° C./sec) It is cooled by temperature. The above heating is performed under an atmosphere in which 10% hydrogen is mixed with nitrogen.

  After the sintering step, the tray is taken out of the heating furnace and the sintered body is removed from the tray. Then, the tester visually confirms the surface condition of each tray. If no damage such as cracking or peeling is observed on the surface, the above cycle is repeated again. That is, after performing operations from loading of the green compact to the tray to sintering and taking out of the sintered body, the surface condition of the tray is checked again. If damage such as cracking or peeling is confirmed on the surface, the durability test of the corresponding tray is ended at that point, and the number of cycles repeated is recorded. This operation is performed until surface damage is confirmed or the above cycle is repeated 50 times.

  Table 2 below shows the results of the above durability tests conducted for each tray.

  As shown in Table 2, in Comparative Example 1, when the surface state at the 17th time was confirmed, cracking was confirmed in the tray. This is considered to be due to a visible crack on the surface of the tray due to the impact when the green compact is placed on the tray and the repeated heat treatment after the impact.

  Moreover, in the comparative example 2, peeling of the film was confirmed by the 28th confirmation on the surface. The coated portion is different from the base portion in thermal expansion coefficient, so it is considered that repeated heat treatment and impact during the above handling led to peeling from the base.

  In contrast, in the example, even after the above cycle was repeated 50 times, no surface damage such as cracking or peeling was confirmed on the surface.

  As described above, the sintering tray of the present embodiment formed of ceramics (aluminum titanate) has a physical impact such as placing a green compact as compared with the tray of Comparative Example 1. In addition, since the impact can be absorbed by the flexibility, excellent impact resistance can be exhibited. Further, as compared with the tray in which the film is formed on the surface as in Comparative Example 2, the surface and the inside are homogeneous, and therefore the surface portion is not peeled off by physical impact or thermal shock.

  Furthermore, in the case of a tray formed of a carbon-based material, the surface of the tray reacts with the metal powder during sintering, which causes deformation of the tray surface and shape change of the product. However, since the sintering tray of the present embodiment does not contain a carbon-based material in its component, it is possible to prevent the deformation of the tray or the product due to the reaction with such a green compact.

  As described above, the sintering tray of the present embodiment can be formed at low cost without using a dedicated mold or the like, and can be configured not to cause breakage such as cracking.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, Of course in the range which does not deviate from the summary of this invention, a various change can be added.

1 sinter tray 2 carbon plate 3 green compact

Claims (2)

  A sintering tray characterized in that it is formed of a flexible ceramic.   The sintering tray according to claim 1, wherein the ceramic is aluminum titanate.

Images