JPH0765081B2 - Sintering method of green compact - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for sintering green compacts, and more particularly to a technique for preventing stacked green compacts from falling.

[Prior art and its problems] Conventionally, when manufacturing a sintered product such as an oil-impregnated bearing, the powder is compression-molded to form a ring-shaped green compact, and the obtained green compact is vertically moved. A plurality of them are stacked and inserted into a sintering furnace, and heated at a predetermined temperature for a predetermined time for sintering. However, if the green compacts are simply stacked, the green compacts may be displaced in the radial direction during transportation, and the green compacts stacked on the upper side may drop and crack or deform.

Therefore, it is conceivable to insert a metal core member inside the stacked green compacts so that the green compacts do not shift from each other in the radial direction, but this will hinder handling after sintering. There was a problem. That is, when the green compacts are stacked and sintered, the sintered bodies adhere to each other. Therefore, conventionally, the sintered bodies are separated mechanically or by dropping. However, it cannot be separated in the state where the core member is inserted on the inner peripheral side of the sintered body. For this reason, the core member must first be manually extracted before the separating operation.

When the outer diameter of the core member is approximately the same as the inner diameter of the green compact, that is, when the outer peripheral surface of the core member is inserted in contact with the inner peripheral surface of the green compact, sintering In the high temperature state, the core member thermally expands, and a strong external force is applied to the green compact from the inside, so that the green compact may be cracked or deformed. Conversely, when the outer diameter of the core member is sufficiently smaller than the inner diameter of the green compact, that is, when the core member is inserted with a wide gap between the outer peripheral surface and the inner peripheral surface of the green compact. However, the support of the green compact by the core member becomes insufficient, and the green compact may be displaced during the transportation. Therefore, the outer diameter of the core member needs to be set to be as close as possible to the inner diameter of the green compact while considering the thermal expansion of the core member and the green compact. However, it is difficult to insert a core member having an outer diameter suitable for all green compacts because the green compacts stacked have variations in internal diameter. The yield was reduced due to cracking and deformation of the green compact.

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is possible to prevent the stacked green compacts from being displaced from each other without hindering the work of the post-process, and therefore A method for sintering a green compact that can prevent cracking and deformation due to falling of the powder, and that does not give a strong external force to the green compact that causes cracks during sintering. The purpose is to provide.

[Means for Solving Problems] As a method for sintering a green compact for solving the above problems, a plurality of ring-shaped green compacts are stacked in the axial direction and inserted into a sintering furnace, In a method for sintering a green compact which heats and sinters a powder, before the green compact is inserted into a sintering furnace, it is made of a material that can be burned down at the temperature inside the sintering furnace,
In addition, the tape having a width approximately equal to the pile height of the green compact is annularly arranged on the inner peripheral side of the green compact, and the tape is relaxed to press the inner peripheral surface of the green compact. , Adopt the technology of sintering in a sintering furnace.

Further, in the method for sintering a green compact, a plurality of ring-shaped green compacts are stacked in the axial direction and inserted into a sintering furnace, and the green compact is heated and sintered. Before being inserted into the binder, a tape made of a material that can be burned at the temperature inside the sintering furnace and having a width similar to the stack height of the green compact is formed into an annular shape on the outer peripheral surface of the green compact. A technique is adopted in which both ends of the tape are adhered to each other while the tape is wound and then sintered in a sintering furnace.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. In the figure, reference numeral 1 is a green compact, and 2 is a tape. The green compact 1 has a ring shape, and is placed on a belt conveyor or the like in a state where a plurality of green compacts are stacked in the vertical direction and inserted into a sintering furnace. Tape 2
Is made of cardboard, and its width is almost the same as the height of the stacked green compacts 1 ... And the length is set longer than the inner circumference of the green compact 1.

Next, a method of sintering the green compact 1 using the tape 2 will be described. First, the tape 2 is formed into an annular shape so that both ends thereof overlap with each other, and is wound such that the outer diameter thereof is smaller than the inner diameter of the green compact 1. Then, tape 2 to green compact 1
Insert on the inner side of. Then, the tape 2 relaxes and expands in diameter, and its outer peripheral surface presses the inner peripheral surface of the green compact 1. Therefore, the green compacts 1 ... Can not move relative to each other in any radial direction. Next, the green compacts 1 ... Are inserted into a sintering furnace and sintered for a predetermined time. Then, the tape 2 burns due to the temperature inside the furnace. Then, after heating for a predetermined time, it is taken out from the sintering furnace.

In such a green compact sintering method, the inner peripheral surface of the green compact 1 is pressed by the outer peripheral surface of the tape 2 when the green compact 1 is inserted into the sintering furnace. , The green compacts 1 are not displaced from each other. Therefore, it is possible to prevent cracking or deformation of the green compact 1 ...
Further, since the tape 2 is burnt at the temperature inside the sintering furnace, it is possible to easily separate the sinters adhered to each other by sintering, and to sinter like the case where a metal core member is inserted. At times, a strong external force that causes cracking or deformation of the green compact 1 does not occur, and a good sintered product can be obtained regardless of variations in the inner diameter of the green compact 1.

In the above embodiment, the tape 2 is provided on the inner peripheral side of the green compact 1.
Although the tape 2 is inserted, the tape 2 may be wound around the outer periphery of the green compact 1 and the both ends thereof may be bonded to each other to form the ring body 3, as shown in FIG. In this case, since the tape 2 is wound around and supported by the green compacts 1 ..., The green compacts 1 are not displaced during transportation. Further, although the cardboard tape 2 is used in the above embodiments, a tape made of resin, cloth, or the like may be used as long as it can be burned down at the temperature in the sintering furnace.

[Effects of the Invention] As described above, in the method for sintering a green compact of the present invention,
Before inserting the green compact into the sintering furnace, a tape made of a material that can be burned down at the temperature inside the sintering furnace and having a width approximately equal to the stack height of the green compact is formed into an annular shape. Since it is arranged on the outer or inner peripheral side of the, it is possible to prevent the stacked green compacts from being displaced from each other without hindering the work of the subsequent process, and therefore, to prevent cracking due to the fall of the green compacts. Deformation can be prevented in advance, and an external force that causes cracking or deformation of the green compact during sintering, such as when inserting a metal core member, does not occur, and a good sintered product can be obtained. The effect that it can be obtained is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a state where a tape is inserted on the inner peripheral side of stacked green compacts, and FIG. 2 is a view showing a modification of the embodiment shown in FIG. FIG. 3 is a perspective view showing a state in which a tape is wound around the outer periphery of the green compact. 1 ... green compact, 2 ... tape.

Claims (2)

[Claims] 1. A method for sintering a green compact, comprising stacking a plurality of ring-shaped green compacts in an axial direction, inserting the green compacts into a sintering furnace, and heating and sintering the green compact. Before the body is inserted into the sintering furnace, a tape made of a material that can be burned down at the temperature in the sintering furnace and having a width approximately the same as the stack height of the green compact is formed into an annular shape. A method for sintering a green compact, which is characterized in that it is arranged on the inner peripheral side, and the tape is relaxed so that the inner peripheral surface of the green compact is pressed by the tape, and then sintered in a sintering furnace. . 2. A method for sintering a green compact, which comprises stacking a plurality of ring-shaped green compacts in an axial direction, inserting the green compacts into a sintering furnace, and heating and sintering the green compact. Before the body is inserted into the sintering furnace, a tape made of a material that can be burned down at the temperature in the sintering furnace and having a width approximately the same as the stack height of the green compact is formed into an annular shape. A method for sintering a green compact, which comprises winding the tape on the outer peripheral side, adhering both ends of the tape to each other, and then sintering in a sintering furnace.