JP4168211B2 - Temperature control method and apparatus for electric heating type sintering machine - Google Patents

Temperature control method and apparatus for electric heating type sintering machine Download PDF

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JP4168211B2
JP4168211B2 JP24240498A JP24240498A JP4168211B2 JP 4168211 B2 JP4168211 B2 JP 4168211B2 JP 24240498 A JP24240498 A JP 24240498A JP 24240498 A JP24240498 A JP 24240498A JP 4168211 B2 JP4168211 B2 JP 4168211B2
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sample
temperature
heating element
temperature control
electrode
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JP2000073103A (en
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和美 森
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IHI Corp
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IHI Corp
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【０００１】
【発明の属する技術分野】
本発明は、通電加熱し加圧することにより金属粉末を焼結する焼結装置の加熱温度を制御する装置に関する。
【０００２】
【従来の技術】
金属粉末に通電しその抵抗により発生するジュール熱により加熱し、加圧装置で加圧する焼結装置が用いられている。図４はこのような焼結装置の一例を示す。内部に試料１を入れる空間を有する円筒状のモールド２には、試料１に電流と圧力を伝達する上部ダイス３と下部ダイス４が嵌合している。上部ダイス３と下部ダイス４を挟んで電極５が設けられ、電源７に接続している。下部の電極５は基礎１１の上に設定され、上部電極５の上部には加圧装置６が設けられ、電極５、ダイス３、４を介して試料１を加圧するようになっている。モールド２やダイス３、４は高温強度に優れ、試料１が着きにくい黒鉛で構成されている。なお、モールド２、ダイス３、４、電極５等は図示しない真空チャンバー内に設けられ、焼結作業は、真空、不活性ガスや還元ガス等の非酸化雰囲気で行われる。
【０００３】
良好な焼結体を得るためには、試料１の温度管理が必要になる。従来は、モールド２の外周温度を測定し、これより試料１の内部の温度を推定し、電源７の電流を制御していた。また、モデルの試料１の温度と電流を計測したデータを作成し、このデータに基づき電流を制御していた。
【０００４】
【発明が解決しようとする課題】
試料１の温度分布は均一でなく、中心が高くなる。これは電流が周囲よりも中心を通り易いからである。温度が適切な焼結温度を越えた場合、試料１が劣化するので、試料１の温度管理を適切に行う必要があるが、モールド２の外周温度と試料１の中心温度との対応が悪く、適切な温度管理が困難であった。また、モデルのデータを用いる方法はモデルの条件と実際の条件が多少異なると、試料１の中心温度がかなり異なるため、モデルの数を多く必要とした。
【０００５】
本発明は、上述の問題点に鑑みてなされたもので、試料の温度を精度よく制御できる焼結装置の温度制御方法と装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上記目的を達成するため、請求項１の発明では、モールドに粉末状の試料を入れこの試料の上下に設けた電極により通電する焼結装置の温度制御方法において、試料の上下のいずれかと電極の間に試料より大きな抵抗の発熱体を設け、この発熱体の温度に基づき電極に通電する電流を制御し、前記発熱体としてグラファイトの積層板を用いる。
【０００７】
試料よりも抵抗値の大きな抵抗を持つ発熱体を試料と直列に接続し、通電すると、発熱体には試料よりも高い温度が発生するので、この温度に基づき電流を制御することにより、試料が過熱するのを防止できる。また電流をパラメータとして発熱体と試料の温度のデータを求めておけば、発熱体の温度を計測し、これに基づき電流を制御して試料の温度を所望の温度にすることができる。
【０００８】
請求項２の発明では、粉末状の試料を入れるモールドと、この試料の上下に設けられた電極と、この電極に通電する電源と、を備えた焼結装置において、前記試料の上下のいずれかと電極の間に設けられ試料よりも大きな抵抗の発熱体と、この発熱体の温度を計測する温度センサと、この温度センサの計測値に基づき電源の電流を制御する制御器と、を備え、前記発熱体としてグラファイトの積層板を用いた。
【０００９】
発熱体と試料は直列に接続され同一の電流が流れるので、抵抗の大きい発熱体の方が高温となる。この温度に基づき電流を制御することにより、試料が過熱するのを防止できる。また、電流をパラメータに発熱体と試料の温度のデータを予め求めておけば、このデータに基づき試料の温度を制御できる。
【００１０】
請求項３の発明では、前記試料としてニッケル粉末を用いる。
【００１１】
試料としてニッケル粉末を用い、発熱体としてグラファイトの積層板を用い、発熱体の抵抗をニッケル粉末の試料よりやや高くしたところ、試料の中心の温度が、積層板の合わせ目近傍の外面の温度より加熱初期は低いが、時間の経過とともに収斂することが分かった。この温度データを用いることにより、試料の温度を精度よく制御できる。
【００１２】
【発明の実施の形態】
以下、本発明の実施形態を図面を参照して説明する。
図１は実施形態の焼結装置の構成を示す図である。なお、図４と同一符号は同一のものを表す。内部に試料１を入れる空間を有する円筒状のモールド２には、試料１に電流と圧力を伝達する上部ダイス３が、試料１の上部に嵌合し、下部には発熱体８が設けられている。発熱体８はグラファイトの板を積層したもので、電流を通し圧力に耐える。上部ダイス３と発熱体８を挟んで電極５が設けられ 、下部電極５は基礎１１の上に設定されている。上部電極５の上部には加圧装置６が設けられ、上部電極５、上部ダイス３を介して試料１を加圧するようになっている。モールド２やダイス３は高温強度に優れ、粉末１が着きにくい黒鉛で構成されている。なお、モールド２、ダイス３、発熱体８、両電極５等は図示しない真空チャンバー内に設けられ、焼結作業は、真空、不活性ガスや還元ガス等の非酸化雰囲気で行われる。
【００１３】
電源７が両電極５に接続され、上部ダイス３、試料１、発熱体８に電流を供給する。発熱体８を構成する積層板の外面で、積層位置近傍の表面温度を計測する放射温度計９が設けられ、その計測データを制御器１０に伝達する。制御器１０は予め求めてある電流値と、発熱体８の温度計測データと、試料１の中心温度データに基づき、電源７の電流を制御して、試料１の温度制御を行う。
【００１４】
図２は試料１としてニッケル粉末を用い、発熱体８として厚み２０ｍｍのグラファイト板５枚を積層し通電したときの温度曲線を示す。発熱体８の抵抗はニッケル粉末の抵抗よりやや高い値となっている。試料１の温度計測位置は中心であり、発熱体８の計測位置は外周面の積層位置である。積層面は接触抵抗が高くなるので温度が高くなり、計測位置として適している。通電開始時は試料中心温度の立ち上がりは遅いが、時間とともに発熱体表面温度に収斂してゆく。このように試料中心温度と発熱体表面温度の相関関係が良いので、良好な温度制御ができる。
【００１５】
図３は発熱体８のグラファイト積層板の圧力による抵抗値の変化を示す。グラファイト積層板は積層面での接触が悪いと抵抗が大きくなるが、１０ｋｇ／ｃｍ2 を越えると一定値となる。焼結時の圧力は約１５０ｋｇ／ｃｍ2 以上であるので問題はない。
【００１６】
上記実施形態では、発熱体８を試料１の下側に設置したが、試料１の上側に設けてもよい。ただしこの場合、加圧により発熱体８が沈むので、発熱体８として積層板を用いる場合、積層位置が沈むので、この位置に温度計を設定する場合、沈下を考慮して温度センサの位置を設定する。
【００１７】
【発明の効果】
以上の説明より明らかなように、本発明は、試料と電気的に直列に発熱体を設置し、この発熱体の温度を測定することにより、試料の温度を精度良く制御できる。この場合、発熱体の抵抗を試料の抵抗より大きく設定し、試料より高い温度を計測するようにして、試料の過熱を防止することができる。
【図面の簡単な説明】
【図１】本発明の実施形態の構成を示す図である。
【図２】試料中心温度と発熱体表面温度の関係の一例を示す図である。
【図３】グラファイト積層板の圧力による抵抗値の変化を示す図である。
【図４】従来の焼結装置の構成を示す図である。
【符号の説明】
１ 試料
２ モールド
３ 上部ダイス
４ 下部ダイス
５ 電極
６ 加圧装置
７ 電源
８ 発熱体
９ 放射温度計（温度センサ）
１0 制御器
１１ 基礎[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for controlling the heating temperature of a sintering apparatus that sinters metal powder by energization heating and pressurization.
[0002]
[Prior art]
A sintering apparatus is used in which a metal powder is energized, heated by Joule heat generated by its resistance, and pressurized by a pressure apparatus. FIG. 4 shows an example of such a sintering apparatus. An upper die 3 and a lower die 4 that transmit current and pressure to the sample 1 are fitted in a cylindrical mold 2 having a space for containing the sample 1 therein. An electrode 5 is provided between the upper die 3 and the lower die 4 and is connected to a power source 7. The lower electrode 5 is set on the base 11, and a pressurizing device 6 is provided on the upper electrode 5 to pressurize the sample 1 through the electrode 5 and the dies 3 and 4. The mold 2 and the dies 3 and 4 are made of graphite excellent in high-temperature strength and difficult to reach the sample 1. The mold 2, the dies 3, 4, the electrode 5 and the like are provided in a vacuum chamber (not shown), and the sintering operation is performed in a non-oxidizing atmosphere such as a vacuum, an inert gas or a reducing gas.
[0003]
In order to obtain a good sintered body, the temperature control of the sample 1 is required. Conventionally, the outer peripheral temperature of the mold 2 is measured, the temperature inside the sample 1 is estimated from this, and the current of the power source 7 is controlled. Moreover, the data which measured the temperature and electric current of the model sample 1 were created, and the electric current was controlled based on this data.
[0004]
[Problems to be solved by the invention]
The temperature distribution of the sample 1 is not uniform and the center is high. This is because the current is easier to pass through the center than the surroundings. When the temperature exceeds an appropriate sintering temperature, the sample 1 deteriorates, so it is necessary to appropriately manage the temperature of the sample 1. However, the correspondence between the outer peripheral temperature of the mold 2 and the center temperature of the sample 1 is poor, Appropriate temperature control was difficult. Further, the method using model data requires a large number of models because the center temperature of the sample 1 is considerably different if the model conditions and actual conditions are slightly different.
[0005]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a temperature control method and apparatus for a sintering apparatus that can accurately control the temperature of a sample.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, in a temperature control method for a sintering apparatus in which a powdered sample is put in a mold and energized by electrodes provided above and below the sample, A heating element having a resistance larger than that of the sample is provided between them, and the current supplied to the electrode is controlled based on the temperature of the heating element, and a graphite laminate is used as the heating element .
[0007]
When a heating element having a resistance greater than that of the sample is connected in series with the sample and energized, the heating element generates a temperature higher than that of the sample. By controlling the current based on this temperature, the sample is It can prevent overheating. If the data of the temperature of the heating element and the sample are obtained using the current as a parameter, the temperature of the heating element can be measured, and the current can be controlled based on this to make the temperature of the sample the desired temperature.
[0008]
In a second aspect of the present invention, in a sintering apparatus comprising a mold for storing a powdered sample, electrodes provided above and below the sample, and a power source for energizing the electrode, A heating element that is provided between the electrodes and has a resistance greater than that of the sample, a temperature sensor that measures the temperature of the heating element, and a controller that controls the current of the power source based on the measurement value of the temperature sensor , A graphite laminate was used as the heating element .
[0009]
Since the heating element and the sample are connected in series and the same current flows, the heating element having a higher resistance has a higher temperature. By controlling the current based on this temperature, the sample can be prevented from overheating. In addition, if data on the temperature of the heating element and the sample is obtained in advance using the current as a parameter, the temperature of the sample can be controlled based on this data.
[0010]
In the invention of claim 3, nickel powder is used as the sample .
[0011]
When nickel powder was used as the sample, a graphite laminate was used as the heating element, and the resistance of the heating element was slightly higher than that of the nickel powder sample, the temperature at the center of the sample was higher than the temperature of the outer surface near the joint of the laminate. It was found that the initial stage of heating was low but converged over time. By using this temperature data, the temperature of the sample can be accurately controlled.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of a sintering apparatus according to an embodiment. The same reference numerals as those in FIG. 4 denote the same components. A cylindrical mold 2 having a space for containing the sample 1 therein is provided with an upper die 3 for transmitting current and pressure to the sample 1 and fitted to the upper part of the sample 1 and a heating element 8 provided at the lower part. Yes. The heating element 8 is a laminate of graphite plates, and withstands pressure through an electric current. An electrode 5 is provided between the upper die 3 and the heating element 8, and the lower electrode 5 is set on the foundation 11. A pressure device 6 is provided on the upper electrode 5 so as to press the sample 1 through the upper electrode 5 and the upper die 3. The mold 2 and the die 3 are made of graphite that has excellent high-temperature strength and is difficult for the powder 1 to adhere to. The mold 2, the die 3, the heating element 8, both electrodes 5 and the like are provided in a vacuum chamber (not shown), and the sintering operation is performed in a non-oxidizing atmosphere such as vacuum, inert gas, reducing gas, or the like.
[0013]
A power source 7 is connected to both electrodes 5 and supplies current to the upper die 3, the sample 1, and the heating element 8. A radiation thermometer 9 for measuring the surface temperature in the vicinity of the lamination position is provided on the outer surface of the laminated plate constituting the heating element 8, and the measurement data is transmitted to the controller 10. The controller 10 controls the temperature of the sample 1 by controlling the current of the power source 7 based on the current value obtained in advance, the temperature measurement data of the heating element 8, and the center temperature data of the sample 1.
[0014]
FIG. 2 shows a temperature curve when nickel powder is used as the sample 1 and five graphite plates having a thickness of 20 mm are stacked as the heating element 8 and energized. The resistance of the heating element 8 is slightly higher than that of nickel powder. The temperature measurement position of the sample 1 is the center, and the measurement position of the heating element 8 is the stacking position of the outer peripheral surface. Since the laminated surface has a high contact resistance, the temperature is high, which is suitable as a measurement position. At the start of energization, the rise of the sample center temperature is slow, but it converges to the heating element surface temperature with time. Thus, since the correlation between the sample center temperature and the heating element surface temperature is good, good temperature control can be performed.
[0015]
FIG. 3 shows a change in resistance value due to the pressure of the graphite laminate of the heating element 8. The resistance of the graphite laminate increases when the contact on the laminate surface is poor, but becomes a constant value when exceeding 10 kg / cm 2 . Since the pressure during sintering is about 150 kg / cm 2 or more, there is no problem.
[0016]
In the above embodiment, the heating element 8 is installed on the lower side of the sample 1, but may be provided on the upper side of the sample 1. In this case, however, the heating element 8 sinks due to pressurization. Therefore, when a laminated plate is used as the heating element 8, the stacking position sinks. Set.
[0017]
【The invention's effect】
As is apparent from the above description, the present invention can accurately control the temperature of the sample by installing a heating element in series with the sample and measuring the temperature of the heating element. In this case, overheating of the sample can be prevented by setting the resistance of the heating element to be larger than the resistance of the sample and measuring a temperature higher than the sample.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a relationship between a sample center temperature and a heating element surface temperature.
FIG. 3 is a diagram showing a change in resistance value due to pressure of a graphite laminate.
FIG. 4 is a diagram showing a configuration of a conventional sintering apparatus.
[Explanation of symbols]
1 Sample 2 Mold 3 Upper die 4 Lower die 5 Electrode 6 Pressurizer 7 Power source 8 Heating element 9 Radiation thermometer (temperature sensor)
10 Controller 11 Basics

Claims (3)

モールドに粉末状の試料を入れこの試料の上下に設けた電極により通電する焼結装置の温度制御方法において、試料の上下のいずれかと電極の間に試料より大きな抵抗の発熱体を設け、この発熱体の温度に基づき電極に通電する電流を制御し、
前記発熱体としてグラファイトの積層板を用いることを特徴とする通電加熱式焼結装置の温度制御方法。In a temperature control method of a sintering apparatus in which a powdery sample is placed in a mold and energized by electrodes provided above and below this sample, a heating element having a resistance greater than that of the sample is provided between either the top or bottom of the sample and the electrode. Control the current flowing to the electrode based on the body temperature ,
A temperature control method for an electrically heated sintering apparatus, wherein a laminate of graphite is used as the heating element . 粉末状の試料を入れるモールドと、この試料の上下に設けられた電極と、この電極に通電する電源と、を備えた焼結装置において、前記試料の上下のいずれかと電極の間に設けられ試料よりも大きな抵抗の発熱体と、この発熱体の温度を計測する温度センサと、この温度センサの計測値に基づき電源の電流を制御する制御器と、を備え、
前記発熱体としてグラファイトの積層板を用いたことを特徴とする通電加熱式焼結装置の温度制御装置。In a sintering apparatus comprising a mold for storing a powdery sample, electrodes provided above and below this sample, and a power source for energizing this electrode, the sample provided between any of the samples above and below the electrode A heating element having a larger resistance, a temperature sensor for measuring the temperature of the heating element, and a controller for controlling the current of the power source based on the measured value of the temperature sensor ,
A temperature control apparatus for an electrically heated sintering apparatus, wherein a laminate of graphite is used as the heating element . 前記試料としてニッケル粉末を用いたことを特徴とする請求項２に記載の通電加熱式焼結装置の温度制御装置。The temperature control apparatus for an electrically heated sintering apparatus according to claim 2, wherein nickel powder is used as the sample .
JP24240498A 1998-08-28 1998-08-28 Temperature control method and apparatus for electric heating type sintering machine Expired - Lifetime JP4168211B2 (en)

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JP4168211B2 true JP4168211B2 (en) 2008-10-22

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