JP2006231724A - Method for producing sintered tube and supporting jig - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a sintered tube which can precisely maintain the shape of a tubular molding before being sintered and a supporting jig. <P>SOLUTION: The method for producing the sintered tube includes a step (a) for manufacturing the tubular molding 20 containing a metal or ceramic powder and a binder, a step (b) in which a cylindrical support member 10 with its outside diameter contracted and enlarged is inserted into the hollow part of the molding (20) while the diameter of the support member 10 is contracted, and a step (c) in which the support member 10, after being inserted into the hollow part of the molding 20, is expanded. The outside diameter of the contracted support member 10 is smaller than the inside diameter of the molding 20, and the outside diameter of the expanded support member 10 is substantially equal to the inside diameter of the molding 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a tube made of sintered metal or ceramics, and more particularly to a method for manufacturing a sintered tube and a supporting jig capable of maintaining the shape of a green compact before sintering with high accuracy.

  Tubes made of sintered metal or ceramics (hereinafter sometimes collectively referred to as ceramics) are used in various applications. In the most general manufacturing process of this ceramic tube, first, a ceramic raw material powder and a resin binder are kneaded and extruded to produce a tubular molded body. The obtained tubular molded body is sintered at a predetermined temperature.

Conventionally, various proposals have been made to prevent deformation during sintering. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2002-255659) proposes to sinter a tubular molded body while rotating the tubular molded body around its central axis while holding the tubular molded body horizontally. is doing. According to this proposal, deformation of the diameter of the tubular molded body is suppressed by applying isotropic weight to the tubular molded body.
Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-137099) forms a first hole and a second hole in a cylindrical molded body, and reinforces the periphery or the vicinity of each of the first hole and the second hole. Reinforce with members, insert a rod-shaped or tubular jig into the first hole and the second hole, and sinter while holding the tubular molded body with the jig so that the longitudinal direction of the tubular molded body is oriented in the vertical direction Propose to do.

JP 2002-255659 A JP 2004-137099 A

As described above, deformation during sintering has been regarded as a problem as deformation in the production of ceramic tubes. However, when the thickness of the ceramic tube is reduced, the strength of the tubular molded body is insufficient, and deformation in the process from extrusion molding to sintering becomes a problem. For example, the tubular molded body may be deformed before sintering and cannot be used for sintering. Or the yield after sintering may deteriorate.
The present invention was made based on such a technical problem, and aims to provide a method for manufacturing a sintered tube and a support jig capable of accurately maintaining the shape of a tubular molded body before sintering. To do.

In order to maintain the shape of the tubular molded body, a mandrel having an outer diameter equal to the inner diameter may be inserted into the hollow portion of the tubular molded body. However, the ceramic molded body after extrusion molding is distorted, and it is difficult to insert a mandrel having an outer diameter equal to the inner diameter. Therefore, a mandrel having an outer diameter that forms a predetermined clearance with the tubular molded body is used. However, in this case, the large effect of maintaining the shape cannot be expected due to the presence of the clearance between the tubular molded body and the bar. Therefore, the present invention is in a reduced diameter state when inserted into the hollow portion of the tubular molded body, but after inserting into the hollow portion of the tubular molded body, the diameter is expanded and its outer diameter is substantially equal to the inner diameter of the tubular molded body. We propose to use the same mandrel.
That is, the present invention provides a step (a) for producing a tubular molded body containing a metal or ceramic powder and a binder, and a rod-like support member having a reduced diameter state with a small outer diameter and an expanded state with a large outer diameter. A step (b) of inserting into the hollow portion of the molded body in a reduced diameter state, and a step (c) of setting the support member in a diameter-expanded state after inserting the support member into the hollow portion of the molded body. The outer diameter of the reduced diameter support member is smaller than the inner diameter of the molded body, and the outer diameter of the expanded diameter support member substantially matches the inner diameter of the molded body.

  In the present invention, the support member may be configured to include a coil member that uses a torsion spring and twists around the axis to form a reduced diameter state and an expanded diameter state. The function of expanding / reducing the diameter by twisting the coil is used. The reduced diameter state and the expanded diameter state can be realized by a simple method such as twisting the coil member. In the present invention, the support member can include a balloon member that is in a reduced diameter state when the amount of gas inside is small, and that is in a state of diameter expansion when the amount of gas inside is relatively large. This form can also realize a reduced diameter state and an enlarged diameter state by a simple method of introducing and discharging gas.

In the present invention, a step (d) of shaping the outer peripheral surface of the molded body while rotating the molded body about the support member can be provided. In order to prevent deformation of the molded body in the process of sintering the molded body, a support member is used.
Moreover, this invention can be equipped with the step (e) of sintering a molded object in the state which stood the support member. In Patent Document 2, the molded body is sintered in a suspended state, but the molded body can be stably supported by, for example, standing a support member on the base material. However, it is difficult to support the entire sintering process with a support member, and the support member is removed after a temperature of about 200 to 300 ° C. at which the strength deteriorates due to removal of the binder contained in the molded body. is required.

  The present invention, as a support jig used in the above method for manufacturing a sintered tube, is a support jig that is inserted into the hollow portion of a tubular molded body containing metal or ceramic powder and a binder and supports the molded body. , A reduced diameter state with a small outer diameter and an expanded state with a large outer diameter, a reduced diameter state when the length is relatively long, and an expanded state when the length is relatively short What is provided with the coil member which makes | forms is provided.

  As the support shaft, a mandrel can be provided in addition to the coil member, and the coil member can be disposed around the mandrel so that the diameter of the coil member can be expanded or reduced with respect to the mandrel.

  As described above, according to the present invention, the support member is inserted into the hollow portion of the molded body in a reduced diameter state, and the support member is inserted into the hollow portion of the molded body, and then the support member is expanded in diameter. Can be supported. Therefore, the insertion into the molded body can be performed smoothly, and the clearance from the molded body can be eliminated in the expanded diameter state, so that the shape of the molded body can be accurately maintained.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
In this embodiment, an example of manufacturing a ceramic tube for a fuel cell will be described. As shown in FIG. 1, the ceramic tube for a fuel cell includes a kneaded material preparation step (step S101), a molded body preparation step (step S102), a support member insertion step (step S103), a drying step (step S104), and printing. A process (step S105) and a sintering process (step S106) are provided. Hereinafter, it demonstrates in order of a process.

(1) Kneaded material preparation process (step S101)
An organic binder (including a solvent and an additive) is mixed with a ceramic powder raw material (calcium stabilized zirconia, yttrium stabilized zirconia, alumina, etc.) having a predetermined particle size to form a uniform kneaded product. The kneaded material may be produced according to a conventional method. Here, the present invention will be described by taking ceramics as an example, but it goes without saying that the present invention can be applied when a sintered tube is manufactured using metal powder.
(2) Molded body manufacturing process (step S102)
Next, a tubular molded body is produced using the kneaded material obtained above. It is effective to use an extrusion molding method for producing a molded body. That is, as shown in FIG. 2, the kneaded product is put into an extrusion molding machine 30, and a tubular molded body 20 is produced by an extrusion method.

(3) Support member insertion step (step S103)
As shown in FIG. 2, the support member 10 is inserted into the hollow portion of the tubular molded body 20 formed by the extrusion molding machine 30. In the present embodiment, the support member 10 is waiting at a position corresponding to the hollow portion of the tubular molded body 20 continuously produced from the extrusion molding machine 30. As a result of continuous extrusion from the extrusion molding machine 30 and progressing on the conveyor 31 in the left direction in the figure, the support member 10 is inserted into the hollow portion of the molded body 20. When extrusion of a predetermined length is performed, extrusion is temporarily stopped and the molded body 20 is cut.
In this example, the support member 10 is inserted into the hollow portion of the molded body 20 while the molded body 20 is extruded. However, after the molded body 20 having a predetermined length is manufactured, the support member 10 is inserted into the molded body 20. Needless to say, it may be inserted into the hollow portion.

FIGS. 3A and 3B are diagrams showing a procedure for supporting the molded body 20 by the support member 10 in the present embodiment. FIG. 3A is a diagram showing the support member 10 in a reduced diameter state, and FIG. It is a figure which shows a state.
As shown in FIG. 3, the support member 10 includes a coil member 1, a mandrel 2, and a coil adjustment nut 3. The coil member 1 wound in the clockwise direction is disposed around the mandrel 2. One end E1 of the wire constituting the coil member 1 is fixed to the mandrel 2. Further, the other end E <b> 2 of the wire constituting the coil member 1 is fixed to the outer periphery of the coil adjustment nut 3. The outer periphery of the mandrel 2 is threaded, and the coil adjustment nut 3 is screwed onto the mandrel 2.
The support member 10 is provided with a protective tube 4 on the outer periphery of the coil member 1. The protective tube 4 is provided in order to prevent contact marks on the inner peripheral surface of the molded body 20 when the coil member 1 is in direct contact with the molded body 20. Since the protective tube 4 needs to be deformed as the coil member 1 expands and contracts, it is desirable that the protective tube 4 be made of a flexible material such as resin or rubber.

At the stage of FIG. 2 in which the support member 10 is inserted into the hollow portion of the molded body 20, the support member 10 is in a reduced diameter state as shown in FIG. Since the outer diameter of the support member 10 at this time (the outer diameter of the protective tube 4) is smaller than the inner diameter of the molded body 20, the support member 10 can be easily inserted into the hollow portion of the molded body 20.
After inserting the support member 10 into the molded body 20 as much as necessary, the diameter of the support member 10, specifically, the diameter of the coil member 1 is increased (expanded) as shown in FIG. In order to increase the diameter of the coil member 1, the coil adjustment nut 3 is twisted counterclockwise so as to advance in the left direction in the figure. Since the coil member 1 is wound in the clockwise direction as described above, by twisting the coil adjusting nut 3 in the counterclockwise direction, the coil member 1 is twisted in the opposite direction to the winding around the axis. To be added, its diameter increases. The coil adjustment nut 3 is twisted until the diameter of the coil member 1 increases and the outer diameter of the protective tube 4 substantially matches the inner diameter of the molded body 20.

(4) Drying process (step S104)
After the supporting member 10 is brought into the expanded state, the molded body 20 is dried to mainly remove the solvent contained in the binder contained in the molded body 20. This drying is performed by maintaining the temperature at, for example, 50 to 200 ° C. in a drying furnace. At this time, drying can be performed in a state where both ends of the support member 10 that supports the molded body 20 are suspended, but the molded body 20 immediately after extrusion includes a large amount of binder, and thus is easily deformed. Therefore, as shown in FIG. 4, it is desirable to dry in a state of being placed on a pair of rotating rollers 5. Since the outer surface of the molded body 20 is in contact with the roller 5, deformation is prevented. At this time, as shown in FIG. 4, it is desirable that the link 6 that regulates the distance between the support member 10 and the rotation shaft of the roller 5 is spanned between the support member 10 and the roller 5. This is to prevent the molded body 20 from being separated from the roller 5.

(5) Printing process (step S105)
After the molded body 20 is dried to a predetermined extent, a paste-like fuel electrode material (for example, Ni / zirconia) is applied to the outer surface of the molded body 20 by screen printing. The fuel electrode film is printed on the outer peripheral surface of the molded body 20 in a striped pattern with a constant width in the longitudinal direction. Next, a paste-like electrolyte material (for example, zirconia) is applied thereon (screen printing) and dried at 50 to 200 ° C. in a drying furnace. The electrolyte membrane is printed in a striped manner, similar to the fuel electrode membrane. However, shift it slightly in one direction. Subsequently, a paste-like interconnector material (for example, lanthanum chromite or titanium oxide) is overlaid thereon so that the electrolyte membrane of a certain stripe and the fuel electrode membrane of the adjacent stripe are connected by the interconnector film. Apply (screen printing) and dry at 50-200 ° C. in a drying oven. Further, a paste-like air electrode material (for example, lanthanum manganate) is applied on the electrolyte membrane in an overlapping manner (screen printing), and dried at 50 to 200 ° C. in a drying furnace.

(6) Sintering process (step S106)
The molded body 20 for which predetermined printing has been completed is then sintered. Sintering can be performed after the support member 10 is removed from the molded body 20. Prior to removing the support member 10 from the molded body 20, the coil adjustment nut 3 of the support member 10 is twisted clockwise to reduce the diameter of the coil member 1 and reduce the diameter of the support member 10. To.
In the case of sintering after removing the support member 10 from the molded body 20, the molded body 20 can be sintered in a state where it is suspended in a sintering furnace by a method as disclosed in Patent Document 2. In the sintering, for example, the temperature is raised to a holding temperature (1200 to 1700 ° C.) at an appropriate heating rate (eg, 1 ° C./min). When the holding temperature is reached, the temperature is held for a predetermined time. Thereafter, the sintering temperature is lowered. The temperature is lowered at an appropriate rate of temperature reduction (for example, 2 ° C./min).

  In addition, sintering can be started with the support member 10 inserted into the molded body 20. However, in this case, it does not mean that the support member 10 is inserted into the molded body 20 until the completion of sintering. When the predetermined temperature is reached, the support member 10 needs to be removed from the molded body 20. For example, while the molded body 20 is suspended in a sintering furnace, the support member 10 is inserted into the hollow portion of the molded body 20. At this time, the support member 10 is in an expanded state. Further, the other end of the support member 10 that is not inserted into the hollow portion of the molded body 20 is positioned outside the sintering furnace through the sintering furnace. When the temperature reaches a predetermined temperature, the support member 10 is removed from the molded body 20 by operating the support member 10 positioned outside the sintering furnace to reduce the diameter. In this sintering process, the binder is removed.

  Through the above process, a solid electrolyte type in which a plurality of fuel cells (one fuel cell of interconnector membrane-fuel electrode membrane-electrolyte membrane-air electrode membrane-interconnector membrane) are assembled on the surface of the ceramic tube. The cell tube of the fuel cell is completed.

  In the above embodiment, the support member 10 is reduced in diameter and expanded using the coil member 1, but a hollow balloon can be used as the support member 40 as shown in FIG. 5. This support member 40 can make the support member 40 into a diameter-reduced state and a diameter-expanded state by controlling the introduction and discharge of gas into the hollow portion. That is, if there is little gas introduction into a hollow part, it will be in a reduced diameter state, and as shown to Fig.5 (a), the support member 40 is inserted in the hollow part of the molded object 20 at this state. After the support member is inserted into the hollow portion of the molded body 20, the support member 40 is in an expanded state by introducing gas from the gas introduction hole H of the support member 40 into the hollow portion.

Next, the example of the specification of the support member 10 for implementing this invention is shown.
As the coil member 1, a torsion spring is used. As is well known, a torsion spring is a type of spring that acts as a spring by twisting a wire. Since it has the characteristic that the area (coil diameter) which a spring occupies can be made small, it can be used for this invention. In the present invention, it is preferable to use a spring having a round and relatively thick wire diameter. The material of the wire constituting the spring can be a soft material having durability such as a stainless steel wire for spring (JIS SUS304WPB) and weak spring repulsion.

The amount of change ΔD in the coil diameter of the torsion spring can be expressed by the following equation.
ΔD = (Δn / n) × D
D: No-load coil center diameter ΔD: Amount of decrease in coil center diameter when torque is applied n: Effective number of turns when no load is applied Δn: Increase amount of turns when torque is applied

If a torsion spring having a relatively small number of turns is used in order to increase the change in the coil center diameter, the strength may be lowered. Therefore, it is preferable to increase the diameter of the wire.
Specifically, when the inner diameter of the molded body 20 is in the range of 20 to 30 mm, the coil diameter needs to be varied between the inner diameter of the molded body 20-(0.2 to 1 mm). For example, when the inner diameter of the molded body 20 is 25 mm, D: 24.8 mm (diameter in the expanded state), ΔD: 0.8 mm, and n: 3, Δn: increase in the number of turns when torque is loaded If a torsion spring having an amount of 10% is used and a torque is applied to the torsion spring, the expanded diameter state can be changed to the reduced diameter state.

It is a flowchart which shows the manufacturing process of the ceramic pipe | tube in this Embodiment. It is a figure which shows the extrusion process and support member insertion process in this Embodiment. It is sectional drawing which shows the procedure which supports a molded object with the support member in this Embodiment, (a) is a figure which shows a diameter reduction state of a support member, (b) is a figure which shows a diameter expansion state of a support member. . It is a figure which shows the drying process in this Embodiment. It is sectional drawing which shows the other support member in this Embodiment, (a) is a figure in which a support member shows a diameter-reduced state, (b) is a figure in which a support member shows a diameter-expanded state.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,40 ... Support member, 1 ... Coil member, 2 ... Mandrel, 3 ... Coil adjustment nut, 4 ... Protective tube, 5 ... Roller, 6 ... Link, 20 ... Molded object, 30 ... Extruder

Claims (7)

Producing a tubular molded body containing a metal or ceramic powder and a binder;
A step (b) of inserting a rod-shaped support member that has a reduced diameter state with a small outer diameter and an expanded state with a large outer diameter into the hollow portion of the molded body in the reduced diameter state;
After inserting the support member into the hollow part of the molded body, the step (c) of making the support member in the expanded state,
The outer diameter of the support member in the reduced diameter state is smaller than the inner diameter of the molded body,
The method for manufacturing a sintered tube, wherein an outer diameter of the support member in the expanded state substantially coincides with an inner diameter of the molded body.   The method for manufacturing a sintered tube according to claim 1, wherein the support member includes a coil member that forms the reduced diameter state and the expanded diameter state by twisting around an axis.   The said support member is provided with the balloon member which makes the said diameter-reduced state when the amount of gas inside is small, and makes the said diameter-expanded state when the amount of gas inside is relatively large. The manufacturing method of the sintered tube of description.   The method for producing a sintered tube according to any one of claims 1 to 3, further comprising a step (d) of shaping the outer peripheral surface of the molded body while rotating the molded body around the support member. .   The method for manufacturing a sintered tube according to any one of claims 1 to 4, further comprising a step (e) of firing the molded body in a state where the support member is erected. A support jig for supporting the molded body inserted into the hollow portion of a tubular molded body containing a metal or ceramic powder and a binder,
It has a reduced diameter state with a small outer diameter and an expanded state with a large outer diameter,
A support jig comprising: a coil member that is in the reduced diameter state when the length is long, and that is in the expanded state when the length is short.   The supporting jig according to claim 6, further comprising a mandrel disposed around the coil member, wherein the diameter of the coil member expands and contracts with respect to the mandrel.

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