JP3875322B2

JP3875322B2 - Vacuum heat treatment furnace

Info

Publication number: JP3875322B2
Application number: JP27426696A
Authority: JP
Inventors: 丈夫加藤
Original assignee: Ulvac Inc
Current assignee: Ulvac Inc
Priority date: 1996-09-25
Filing date: 1996-09-25
Publication date: 2007-01-31
Anticipated expiration: 2016-09-25
Also published as: JPH10103874A

Description

【０００１】
【発明の属する技術分野】
本発明は真空熱処理炉に関するものであり、更に詳しくは加熱時間の短縮化、および熱処理雰囲気の均一化を図った真空熱処理炉に関するものである。
【０００２】
【従来の技術】
図４は従来使用されている縦型２室式の真空熱処理炉１００の縦断面図である。真空熱処理炉１００は被処理物Ｔを搬入し搬出するための前室１０１と真空下に熱処理するための真空室１１１とからなり、それらの境には両室の間を気密に開閉する仕切弁１０２が設けられている。
【０００３】
前室１０１は側面に被処理物Ｔを搬入搬出するための開閉扉１０３、底部には真空室１１１との間で被処理物Ｔを昇降させるための支持台１０４をシャフト１０６の頂部に備え、その下方には上昇時に後述の熱処理区画１１６を閉塞するための断熱板１０５をシャフト１０６に取り付けた昇降用シリンダ１０７が設けられている。
【０００４】
また、扉１０３と対向する側にはモーターファン１０８が取り付けられ、その風道の周囲にはフィン付きの筒状熱交換器１０９が取り付けられており、前室１０１内の空気または不活性ガスを循環させて熱処理後の被処理物Ｔを冷却するようになっている。
【０００５】
真空室１１１は鋼板の二重壁構造として冷却水が通水可能な側壁１１２、および同様な構造の上蓋１１３で外殻が構成されている。真空室１１１内には、金属性リフレクタが張設された断熱材１１５で囲われて熱処理区画１１６が形成されている。また、熱処理区画１１６内には断熱材１１５の内面に近接してグラファイト製のヒーター１１７が配置されており、側壁１１２に設けた給電端子１１８に接続されている。更には必要な場合に、熱処理区画１１６内に反応性のガスを吹き込むためのガス吹出管１２１が設けられている。
【０００６】
上記の真空熱処理炉１００によって、被処理物Ｔは次ぎのように熱処理される。定常状態においては、真空室１１１内は常時真空排気系によって排気されている。昇降用シリンダ１０７のシャフト１０６が下降され、仕切弁１０２が閉じられた状態において、開閉扉１０３を開けて被処理物Ｔが搬入され、昇降用シリンダ１０７の支持台１０４に載置されて開閉扉１０３が閉じられる。
【０００７】
次いで仕切弁１０２が開けられ、昇降用シリンダ１０７のシャフト１０６が上昇されて、被処理物Ｔは熱処理区画１１６内へ装填され、シャフト１０６に取り付けられている断熱板１０５によって熱処理区画１１６は閉塞される。そして、ヒーター１１７に通電され、熱処理区画１１６内を所定の温度に保持して被処理物Ｔの熱処理が行なわれる。必要な場合には不活性ガスまたは反応性のガスがガス吹出管１２１から導入される。
【０００８】
所定の熱処理時間の経過後、ヒーター１１７の加熱が停止され、ガスが導入されている場合にはそれを停止し、昇降用シリンダ１０７のシャフト１０６が下降されて、被処理物Ｔは前室１０１内へ降ろされ仕切弁１０２が閉じられる。次いで、図示しない配管から大気または不活性ガスが前室１０１内へ導入されると共に、モーターファン１０８が起動され、前室１０１内の空気または不活性ガスが筒状熱交換器１０９で冷却され循環されることにより被処理物Ｔは冷却され、冷却の完了後、開閉扉１０３から外部へ取り出される。
【０００９】
【発明が解決しようとする課題】
従来例の真空熱処理炉１００によって熱処理を行なう場合、加熱に長時間を要するほか、吹き込まれるガスの熱処理区画１１６内における分布も均一でないという不都合な点がある。
【００１０】
図４に示すように、ヒーター１１７は熱処理区画１１６内において断熱材１１５に近接して、すなわち、被処理物Ｔの外周側にのみ設けられているので、加熱時間は真空熱処理炉１００が大型になり熱処理区画１１６の容積が大になるに従って長時間化する。図５、図６は外寸法の異なる熱処理領域Ｔ₁ 、Ｔ₂ 内で複数の被処理物Ｔを熱処理する場合に生じる昇温速度の差を概念的に示す図である。図５のＡは外周上の点ａ、中心点ｂを持つ半径ｒの円柱状の熱処理領域Ｔ₁ 、図５のＢは外周上の点Ａ、中心点Ｂを持つ半径Ｒの円柱状の熱処理領域Ｔ₂ であり、その外周上の点ａ、またはＡは何れもヒーター１１７から同一の距離にある。これらの熱処理領域Ｔ₁ 、Ｔ₂ の上記各点における加熱時間と温度は図６に示すようになる。すなわち、外周面のａ点、Ａ点の温度は熱処理領域Ｔ₁ 、Ｔ₂ の外寸法に関係なく同一曲線に従って時間と共に上昇するのに対し、外寸法の大きい熱処理領域Ｔ₂ の中心点Ｂの温度上昇は外寸法の小さい熱処理領域Ｔ₁ の中心点ｂよりも遅れる。
【００１１】
図７は昇温速度に差が発生する理由を説明する図である。熱処理領域には対流する気体が存在しないので、ヒーター１１７の熱は輻射のみによって伝えられるが、図７に示すように、複数の被処理物ＴＡ、ＴＢ、ＴＣが並べて多段に載置されており（多段に載置するための部材は図７において省略されている）、輻射熱が直接に中心部まで届かない場合には、ヒーター１１７から被処理物ＴＡへの輻射熱で被処理物ＴＡが昇温され、被処理物ＴＡから被処理物ＴＢへの輻射熱で被処理物ＴＢが昇温され、被処理物ＴＢから被処理物ＴＣへの輻射熱で被処理物ＴＣが昇温されるようなプロセスを辿るので、中心部の被処理物ＴＣの昇温は遅れ、熱処理領域内での保持時間をかなり長くしなければ外周側の被処理物ＴＡと同程度の温度にすることはできない。この時間遅れはヒーター１１７から熱処理領域の中心部までの距離、すなわちヒーター１１７からヒーター間の中立点までの距離Ｌに大約比例する。
【００１２】
また、図４に示すように、ガス吹出管１２１は被処理物Ｔの上方に設置されており、その部分の拡大図である図８において、ガスは矢印で示すようにダウンブローに流され、被処理物ＴＡ、ＴＢ、ＴＣが多段に載置されている場合に、外周部への流れが大で中央部の被処理物ＴＣはガスとの接触が不十分となり、反応性のガスを使用する場合には全体を均一に処理することは困難で、その改善が求められている。
【００１３】
【課題を解決するための手段】
本発明の真空熱処理炉は、熱処理区画内へ装填される被処理物の中心部となるようにガス吹込管を設置し、ガス吹込管に複数のガス吹出孔を開口して、被処理物に対しガスが均一に接触するようにしている。
【００１４】
また本発明の真空熱処理炉は、熱処理区画を囲う断熱材の内面に近接してヒーターを設けると共に、熱処理区画内へ装填される被処理物の中心部となるようにガス吹込管兼用の筒状のヒーターを設けて、被処理物を外周側と中心部とから加熱するようにしている。
【００１５】
そして、ガス吹込管兼用の筒状のヒーターは内筒と外筒とが直列に接続された二重筒として内筒と外筒をそれぞれ給電端子に接続すると共に、ガスは内筒へ供給して連通孔から外筒へ導き、外筒の外周面に多段にガス吹出孔を設けたものとしている。
【００１６】
【発明の実施の形態】
以下、本発明の実施の形態による真空熱処理装置について、図面を参照して説明する。
【００１７】
図１は実施の形態の真空熱処理装置に置ける真空室１１の断面図である。真空室１１の下方に設けられる仕切弁や冷却ファン、昇降用シリンダを備えた前室は従来例の真空熱処理装置１００と全く同様に設けられているので、それらの説明は省略する。
【００１８】
真空室１１は鋼板の二重構造として冷却水が通水可能な側壁１２、および同様な構造の上蓋１３で外郭が構成され、その内部に金属製リフレクタが張設された断熱材１５で囲われて熱処理区画１６が形成されていることは従来例の真空熱処理装置１００と同様である。更には、熱処理区画１６内において、断熱材１５の内面に近接してヒーター１７が設けられており、側壁１２に設けた筒状部１４内に固定されている銅製の水冷電極端子１９と一体的なモリブデン製の導電軸１８に接続されている。
【００１９】
そして、本発明を構成する筒状のヒーター２１が熱処理区画１６の中央部に天井面から挿入され、下方から被処理物Ｔを載置して挿入される支持台４にほぼ達する長さに垂下されている。ヒーター２１は二重筒とされ、内筒２２と外筒２３とが直列に接続されて電気回路が形成されており、それぞれは上蓋１３に設けられた水冷電極端子３２、３６に接続されている。すなわち、外筒２３の下端部において、内筒２２と外筒２３とは導電性の環状栓２４によって電気的に接続され、内筒２２の下端部には絶縁性の円柱栓２６が嵌入されている。他方、外筒２３の上端部においては、内筒２２と外筒２３とは絶縁性の環状栓２５によって絶縁されている。
【００２０】
また、内筒２２はその外周端部に固定した電極バー３４を介し、上蓋１３に設けた筒状部３１内に固定されている銅製の水冷電極端子３２と一体的なモリブデン製の導電軸３３に接続されている。同じく外筒２３もその外周端部に固定した電極バー３８を介して、上蓋１３に設けた筒状部３５内に固定されている水冷電極３６と一体的な導電軸３７に接続されている。
【００２１】
更にはこのヒーター２１はガスの吹込管として兼用されるようになっている。すなわち、上蓋１３に設けたガス導入端子４２に外部のガス供給源４１が接続され、ガス導入端子４２に付属するノズル４３が内筒２２の上端にかぶせた絶縁性のキャップ４４に挿通されている。そして、内筒２２には、外筒２３内の上方に位置して、内筒２２と外筒２３との連通孔４５が開口されており、外筒２３の熱処理区画１６内に挿入されている部分には、多段に載置される被処理物Ｔの各段間にガスが放射状に流れ込むように、ガス吹出孔４６が多段に、かつ各段において円周を４等分する位置に開口されている。なお、図１において、ヒーター２１は明確に示すために太く画かれており、実際にはヒーター１７と同程度の径である。また、支持台４上に被処理物Ｔを多段に載置するための部材は省略されている。そのほか、熱処理区画１６は支持台４が挿入されると同時に底面が断熱板５によって閉塞される。なおガスとしては不活性ガスまたは反応性ガスが導入される。すなわち不活性ガスは炉内圧力の調整、被処理物Ｔからの放出ガスの除去、昇温の加速に、また反応性ガスは被処理物Ｔの変性と昇温の加速を目的として導入される。
【００２２】
本実施の形態による真空熱処理炉の真空室１１は以上のように構成されているが、次ぎにその作用を説明する。真空室１１を含む真空熱処理炉としての基本的な作用は従来例の真空熱処理炉１００と同様であるので説明の重複は避け、従来例の真空熱処理炉１００の真空室１１１と異なる作用を主体に説明する。
【００２３】
真空室１１の熱処理区画１６内へ下方から支持台４に多段に載置された被処理物Ｔが装填されると共に、熱処理区画１６の底面が断熱板５で閉塞される。次いで、被処理物Ｔの外周側のヒーター１７と中央部のヒーター２１とが通電され、熱処理区画１６内が所定の温度に保持されて、被処理物Ｔの熱処理が行なわれる。同時にガス供給源４１から反応性のガスが導入されるものとする。反応性のガスはノズル４３から内筒２２内を下降し連通孔４５を経由して外筒２３内へ流れ込み、外筒２３に多段に、かつ各段において９０度の等角度間隔に開口されているガス吹出孔４６から被処理物Ｔの段間へ放射状に均等に吹き出される。
【００２４】
所定の熱処理時間が経過すると、反応性のガスの導入が停止され、ヒーター１７、２１への通電が停止されると共に、支持台４が下降され、被処理物Ｔは冷却されて外部へ取り出される。
【００２５】
以上に説明したように、本実施の形態の真空熱処理炉における真空室１１の熱処理区画１６は被処理物Ｔを外周側から加熱するヒーター１７と中央部から加熱するヒーター２１とを有しているので、加熱の所要時間が大幅に短縮される。従来例の真空熱処理炉１００における熱伝達を説明した図７に対応するものとして、本実施の形態の真空熱処理炉の熱処理区画１６内における熱伝達を図２で説明する。図２は熱処理区画１６内に複数の被処理物ＴＡ、ＴＢが多段に並べて載置されている場合を示すが、被処理物ＴＡ、ＴＢの外周側となるヒーター１７と共に中心部にヒーター２１が設けられている。図２において、被処理物ＴＡは主としてヒーター１７の輻射熱によって、被処理物ＴＢは主としてヒーター２１の輻射熱によってそれぞれ直接に加熱され、被処理物ＴＡの昇温を待って被処理物ＴＡの輻射熱により被処理物ＴＢが昇温されるというようなプロセスではない。
【００２６】
従来例においては、ヒーター１１７から加熱区画１１６の中心部までの距離、すなわち、ヒーター１１７からヒーター間中立点までの距離がＬであったに対して、本実施の形態の加熱区画１６ではこの距離が（Ｌ／２）となるので、被処理物ＴＡ、ＴＢを所定の温度まで昇温させるに要する時間が短縮され、昇温速度が非常に早い真空熱処理炉となる。中心部にヒーター２１を設けることにより、加熱区画１６の有効容積は当然減少するが、熱処理区画１６の有効直径が６００ｍｍ以上である場合、その減少率は５％以下となるので、生産性の向上に対しては、中心部にヒーター２１を設けることによる熱処理速度増大の効果の方が大きい。
【００２７】
また、図３はガス吹込管に兼用されるヒーター２１の部分を示し、図３のＡはその縦断面図、図３のＢは図３のＡにおける［Ｂ］−［Ｂ］線方向の断面図である。被処理物Ｔは外筒２３の周囲に多段に載置され、ガス吹出孔４６が外筒２３に、かつ各段において９０度の等角度間隔に開口されているので、ガスは載置された被処理物Ｔの各段の段間を中心部から外周側へ放射状に広がって流れる。反応性のガスを流して被処理物Ｔと反応させるような熱処理を行なう場合には、反応が均一に進むので最適である。また、ヒーター２１と兼用され、専用の設置スペースを必要としないので、真空熱処理炉の有効容積を低下させず、生産性の点で好ましい。
【００２８】
以上、本発明の実施の形態について説明したが、勿論、本発明はこれに限られることなく、本発明の技術的精神に基づいて種々の変形が可能である。
【００２９】
例えば本実施の形態においては、真空熱処理炉にはガス吹込管を兼用するヒーターを設けたが、ガス吹込管を兼用させずに中央部にヒーターのみを設けるようにしてもよく、また場合によっては、ヒーターを兼用させずに中央部にガス吹込管のみを設けるようにしてもよい。
【００３０】
また本実施の形態においては、上下２室型の真空熱処理炉について説明したが、被処理物Ｔの外周側と同時に被処理物の中心部に設けるヒーターおよびガス吹込管は１室型の真空熱処理炉にも適用され得る。
【００３１】
また本実施の形態においては、熱処理区画１６の中心部に設けるガス吹込管兼用のヒーター２１を二重筒として、ガス吹き込み用のノズル４３を内筒２２へ挿入したが、直接に外筒２３へ挿入するようにしてもよい。
【００３２】
また本実施の形態においては、ガス吹込管兼用のヒーター２１を二重筒としたが、一重筒を縦割りにし絶縁材を挟み込んで両半割り部を直列に接続すると共に上下の両端を塞いで形成される一重筒にガス吹出孔を開口して、ヒーターとガス吹込管とを兼用させるようにしてもよく、本発明のガス吹込管を兼ねるヒーターは被処理物Ｔの中心部に位置するように設置される限りにおいて、その形状は問わない。
【００３３】
また本実施の形態においては、熱処理区画１６は円筒状としたが、角筒状としてもよいことはいうまでもない。
【００３４】
【発明の効果】
本発明は以上に説明したような形態で実施され、次に記載するような効果を奏する。
【００３５】
本願発明の請求項１および請求項２の真空熱処理炉によれば、支持台に多段に載置されて下方から加熱室の熱処理区画内へ装填される被処理物の中心部にガス吹込管が挿通され、ガス吹込管の外周面には多段に、そして各段においては外周側ヘ向かって等角度間隔に配置された複数のガス吹出孔から放射状に不活性ガスまたは反応性ガスを吹き出して被処理物に均等に接触するようにしているので、反応性ガスを使用する場合には反応が均一に進行する。
【００３６】
請求項２の真空熱処理炉によれば、支持台に多段に載置されて下方から加熱室の熱処理区画へ装填される被処理物の外周側となる第１ヒーターのほかに、被処理物の中心部を挿通するようにガス吹込管兼用の第２ヒーターを設けているので、ヒーター間距離が短くなるだけ被処理物の昇温時間が短縮される。中心部に第２ヒーターを設けることにより熱処理区画の内容積は減少するが、そのことよりも熱処理速度が向上する効果の方が大であり、真空熱処理炉の生産性を増大させる。
【００３７】
そして請求項３の真空熱処理炉によれば、第２ヒーターを内筒と外筒とが直列に接続された二重筒とし、内筒へ吹き込むガスが連通孔を経て外筒内へ導かれ、外筒の外周面のガス吹出孔から吹き出すようにして、第２ヒーターとガス吹込管と兼用させているので、これらの設置スペースが節減されて熱処理区画の有効容積が増大し、結果的に真空熱処理装置の生産性を向上させる。
【図面の簡単な説明】
【図１】実施の形態による真空熱処理炉の加熱室の縦断面図である。
【図２】同加熱室の熱処理区画内における熱伝達を示す図である。
【図３】同加熱室の熱処理区画内に挿入垂下されるヒーター兼用ガス吹込管の一部をガスの流れと共に示し、Ａは縦断面図であり、ＢはＡにおける［Ｂ］−［Ｂ］線方向の断面図である。
【図４】従来例の２室型の真空熱処理炉の縦断面図である。
【図５】図６と共に外寸法の異なる熱処理炉内で複数の被処理物を同時に熱処理する場合の昇温速度の差異を概念的に示す図であり、Ａは外寸法の小さい熱処理領域の温度の測定点とヒーター位置を示し、Ｂは外寸法の大きい熱処理領域の同様な温度側定点を示す。
【図６】図５の外寸法の異なる熱処理領域の各温度測定点における熱処理時間と温度の関係を示す図である。
【図７】図６に示す外寸法の異なる熱処理領域において昇温速度の差異の発生を説明する図である。
【図８】従来例におけるガス吹出管によるガスの流れを示す図である。
【符号の説明】
１１真空室
１２側壁
１３上蓋
１５断熱材
１６熱処理区画
１７ヒーター
１８導電軸
１９水冷電極端子
２１ヒーター
２２内筒
２３外筒
２４導電性環状栓
２５絶縁性円柱栓
２６絶縁性環状栓
３２水冷電極端子
３３導電軸
３４電極バー
３６水冷電極端子
３７導電軸
３８電極バー
４１ガス供給源
４２ガス導入端子
４３ノズル
４４絶縁性キャップ
４５連通孔
４６ガス吹出孔
１００従来例の真空熱処理炉
１０１前室
１０２仕切弁
１０３開閉扉
１０４支持台
１０５断熱板
１０６シャフト
１０７昇降用シリンダ
１０８モーターファン
１０９熱交換器
１１１真空室
１２１ガス吹出管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum heat treatment furnace, and more particularly to a vacuum heat treatment furnace which shortens the heating time and makes the heat treatment atmosphere uniform.
[0002]
[Prior art]
FIG. 4 is a longitudinal sectional view of a conventionally used vertical two-chamber vacuum heat treatment furnace 100. The vacuum heat treatment furnace 100 includes a front chamber 101 for carrying in and carrying out the workpiece T and a vacuum chamber 111 for heat treatment under vacuum, and a gate valve for opening and closing between the two chambers at the boundary. 102 is provided.
[0003]
The front chamber 101 includes an opening / closing door 103 for loading and unloading the workpiece T on the side surface, and a support base 104 for raising and lowering the workpiece T between the vacuum chamber 111 at the bottom and a top portion of the shaft 106. Below that is provided an elevating cylinder 107 in which a heat insulating plate 105 for closing a heat treatment section 116 (described later) is attached to the shaft 106 when it is raised.
[0004]
In addition, a motor fan 108 is attached to the side facing the door 103, and a finned cylindrical heat exchanger 109 is attached around the air passage, and air or inert gas in the front chamber 101 is removed. The workpiece T after the heat treatment is circulated and cooled.
[0005]
The vacuum chamber 111 has an outer shell made up of a side wall 112 through which cooling water can flow and a top cover 113 having a similar structure as a double-wall structure of a steel plate. In the vacuum chamber 111, a heat treatment section 116 is formed by being surrounded by a heat insulating material 115 on which a metallic reflector is stretched. Further, a graphite heater 117 is disposed in the heat treatment section 116 in the vicinity of the inner surface of the heat insulating material 115, and is connected to a power supply terminal 118 provided on the side wall 112. Further, when necessary, a gas blow-out pipe 121 for blowing reactive gas into the heat treatment section 116 is provided.
[0006]
In the vacuum heat treatment furnace 100, the workpiece T is heat-treated as follows. In the steady state, the inside of the vacuum chamber 111 is always exhausted by the vacuum exhaust system. In a state where the shaft 106 of the lifting cylinder 107 is lowered and the gate valve 102 is closed, the opening / closing door 103 is opened, the workpiece T is loaded, and is placed on the support base 104 of the lifting cylinder 107 to be opened / closed. 103 is closed.
[0007]
Next, the gate valve 102 is opened, the shaft 106 of the lifting cylinder 107 is raised, the workpiece T is loaded into the heat treatment compartment 116, and the heat treatment compartment 116 is closed by the heat insulating plate 105 attached to the shaft 106. The Then, the heater 117 is energized, and the heat treatment of the workpiece T is performed while maintaining the inside of the heat treatment section 116 at a predetermined temperature. If necessary, an inert gas or a reactive gas is introduced from the gas blowing pipe 121.
[0008]
After the elapse of a predetermined heat treatment time, the heating of the heater 117 is stopped. When the gas is introduced, the heating is stopped, the shaft 106 of the lifting cylinder 107 is lowered, and the object T to be processed is placed in the front chamber 101. The gate valve 102 is closed and the gate valve 102 is closed. Next, air or an inert gas is introduced into the front chamber 101 from a pipe (not shown), and the motor fan 108 is started, and the air or the inert gas in the front chamber 101 is cooled and circulated by the cylindrical heat exchanger 109. As a result, the workpiece T is cooled, and after the cooling is completed, the workpiece T is taken out from the door 103.
[0009]
[Problems to be solved by the invention]
When heat treatment is performed by the vacuum heat treatment furnace 100 of the conventional example, there are disadvantages in that heating takes a long time and the distribution of the injected gas in the heat treatment section 116 is not uniform.
[0010]
As shown in FIG. 4, the heater 117 is provided close to the heat insulating material 115 in the heat treatment section 116, that is, only on the outer peripheral side of the workpiece T, so that the heating time of the vacuum heat treatment furnace 100 is large. As the volume of the heat treatment section 116 increases, the time increases. FIGS. 5 and 6 are diagrams conceptually showing the difference in the heating rate generated when the plurality of workpieces T are heat-treated in the heat-treated regions T ₁ and T _{2 having} different outer dimensions. 5A shows a cylindrical heat treatment region T ₁ having a radius r having a point a on the outer periphery and a center point b, and FIG. 5B shows a cylindrical heat treatment region having a radius R having a point A on the outer periphery and a center point B. In the region T ₂ , the point a or A on the outer periphery thereof is at the same distance from the heater 117. The heating time and temperature at the above-mentioned points in these heat treatment regions T ₁ and T ₂ are as shown in FIG. That is, the temperatures at points a and A on the outer peripheral surface increase with time according to the same curve regardless of the outer dimensions of the heat treatment regions T ₁ and T ₂ , whereas the temperature at the center point B of the heat treatment region T _{2 having} a larger outer dimension. The temperature rise is delayed from the center point b of the heat treatment region T _{1 having} a small outer dimension .
[0011]
FIG. 7 is a diagram for explaining the reason for the difference in the heating rate. Since there is no convective gas in the heat treatment region, the heat of the heater 117 is transmitted only by radiation. However, as shown in FIG. 7, a plurality of objects to be processed TA, TB, TC are arranged in multiple stages. (Members to be placed in multiple stages are omitted in FIG. 7). When the radiant heat does not reach the central portion directly, the temperature of the object TA increases due to the radiant heat from the heater 117 to the object TA. A process in which the object TB is heated by radiant heat from the object TA to the object TB, and the object TC is heated by the radiant heat from the object TB to the object TC. Therefore, the temperature rise of the workpiece TC in the center is delayed, and the temperature cannot be set to the same level as that of the workpiece TA on the outer peripheral side unless the holding time in the heat treatment region is considerably increased. This time delay is roughly proportional to the distance from the heater 117 to the center of the heat treatment region, that is, the distance L from the heater 117 to the neutral point between the heaters.
[0012]
Moreover, as shown in FIG. 4, the gas blowing pipe 121 is installed above the to-be-processed object T, In FIG. 8 which is the enlarged view of the part, gas is made to flow down as shown by the arrow, When workpieces TA, TB, and TC are placed in multiple stages, the flow to the outer periphery is large, and the central workpiece TC is not in contact with the gas, and a reactive gas is used. In this case, it is difficult to uniformly process the whole, and improvement is required.
[0013]
[Means for Solving the Problems]
In the vacuum heat treatment furnace of the present invention, a gas blowing pipe is installed so as to be the central part of the workpiece to be loaded into the heat treatment section, and a plurality of gas blowing holes are opened in the gas blowing pipe to form the workpiece. The gas is in uniform contact .
[0014]
In addition, the vacuum heat treatment furnace of the present invention is provided with a heater in the vicinity of the inner surface of the heat insulating material surrounding the heat treatment section, and a cylindrical shape also serving as a gas blowing pipe so as to be a central portion of an object to be loaded into the heat treatment section. The object to be processed is heated from the outer peripheral side and the central part .
[0015]
The cylindrical heater also serving as a gas blowing pipe connects the inner cylinder and the outer cylinder to the power supply terminal as a double cylinder in which the inner cylinder and the outer cylinder are connected in series, and supplies gas to the inner cylinder. It leads to the outer cylinder from the communication hole, and gas outlet holes are provided in multiple stages on the outer peripheral surface of the outer cylinder .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a vacuum heat treatment apparatus according to an embodiment of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a cross-sectional view of a vacuum chamber 11 that can be placed in the vacuum heat treatment apparatus of the embodiment. Since the front chamber provided with the gate valve, the cooling fan, and the raising / lowering cylinder provided below the vacuum chamber 11 is provided in the same manner as the vacuum heat treatment apparatus 100 of the conventional example, description thereof will be omitted.
[0018]
The vacuum chamber 11 is surrounded by a heat insulating material 15 in which an outer wall is configured by a side wall 12 through which cooling water can flow and a top cover 13 having a similar structure as a double structure of steel plates, and a metal reflector is stretched inside the vacuum chamber 11. The heat treatment section 16 is formed as in the conventional vacuum heat treatment apparatus 100. Further, in the heat treatment section 16, a heater 17 is provided in the vicinity of the inner surface of the heat insulating material 15, and is integrated with a copper water-cooled electrode terminal 19 fixed in a cylindrical portion 14 provided on the side wall 12. It is connected to a conductive shaft 18 made of molybdenum.
[0019]
And the cylindrical heater 21 which comprises this invention is inserted in the center part of the heat processing division 16 from a ceiling surface, and it hangs down to the length which reaches the support stand 4 inserted by mounting the to-be-processed object T from the downward direction. Has been. The heater 21 is a double cylinder, and an inner cylinder 22 and an outer cylinder 23 are connected in series to form an electric circuit, and each is connected to water-cooled electrode terminals 32 and 36 provided on the upper lid 13. . That is, at the lower end portion of the outer cylinder 23, the inner cylinder 22 and the outer cylinder 23 are electrically connected by a conductive annular plug 24, and an insulating cylindrical plug 26 is fitted into the lower end portion of the inner cylinder 22. Yes. On the other hand, at the upper end portion of the outer cylinder 23, the inner cylinder 22 and the outer cylinder 23 are insulated by an insulating annular plug 25.
[0020]
The inner cylinder 22 has a conductive shaft 33 made of molybdenum integral with a copper water-cooled electrode terminal 32 fixed in a cylindrical part 31 provided in the upper lid 13 through an electrode bar 34 fixed to the outer peripheral end portion thereof. It is connected to the. Similarly, the outer cylinder 23 is also connected to a conductive shaft 37 integral with a water-cooled electrode 36 fixed in a cylindrical portion 35 provided on the upper lid 13 via an electrode bar 38 fixed to the outer peripheral end portion thereof.
[0021]
Further, the heater 21 is also used as a gas blowing pipe. That is, an external gas supply source 41 is connected to a gas introduction terminal 42 provided on the upper lid 13, and a nozzle 43 attached to the gas introduction terminal 42 is inserted through an insulating cap 44 that covers the upper end of the inner cylinder 22. . The inner cylinder 22 is located above the outer cylinder 23, and a communication hole 45 between the inner cylinder 22 and the outer cylinder 23 is opened and inserted into the heat treatment section 16 of the outer cylinder 23. In the portion, gas blowout holes 46 are opened in multiple stages and at positions that divide the circumference into four equal parts in each stage so that the gas flows radially between the stages of the workpiece T placed in multiple stages. ing. In FIG. 1, the heater 21 is drawn thick for the sake of clarity, and actually has the same diameter as the heater 17. Further, members for placing the workpieces T on the support base 4 in multiple stages are omitted. In addition, the bottom surface of the heat treatment section 16 is closed by the heat insulating plate 5 at the same time as the support 4 is inserted. An inert gas or a reactive gas is introduced as the gas. That is, the inert gas is introduced for the purpose of adjusting the pressure in the furnace, removing the released gas from the workpiece T and accelerating the temperature rise, and the reactive gas is introduced for the purpose of denaturing the workpiece T and accelerating the temperature rise. .
[0022]
The vacuum chamber 11 of the vacuum heat treatment furnace according to the present embodiment is configured as described above. Next, the operation will be described. Since the basic operation of the vacuum heat treatment furnace including the vacuum chamber 11 is the same as that of the vacuum heat treatment furnace 100 of the conventional example, the description will not be repeated, and the operation different from that of the vacuum chamber 111 of the vacuum heat treatment furnace 100 of the conventional example will be mainly used. explain.
[0023]
A workpiece T placed in multiple stages on the support 4 is loaded into the heat treatment section 16 of the vacuum chamber 11 from below, and the bottom surface of the heat treatment section 16 is closed with the heat insulating plate 5. Next, the outer peripheral side heater 17 and the central heater 21 of the workpiece T are energized, the inside of the heat treatment section 16 is maintained at a predetermined temperature, and the workpiece T is heat-treated. At the same time, a reactive gas is introduced from the gas supply source 41. The reactive gas descends in the inner cylinder 22 from the nozzle 43 and flows into the outer cylinder 23 through the communication hole 45, and is opened in the outer cylinder 23 in multiple stages and at equal angular intervals of 90 degrees in each stage. The gas blowout holes 46 are blown out radially and uniformly between the stages of the workpiece T.
[0024]
When a predetermined heat treatment time elapses, the introduction of the reactive gas is stopped, the energization to the heaters 17 and 21 is stopped, the support base 4 is lowered, and the workpiece T is cooled and taken out to the outside. .
[0025]
As described above, the heat treatment section 16 of the vacuum chamber 11 in the vacuum heat treatment furnace of the present embodiment has the heater 17 for heating the workpiece T from the outer peripheral side and the heater 21 for heating from the center. Therefore, the time required for heating is significantly shortened. The heat transfer in the heat treatment section 16 of the vacuum heat treatment furnace according to the present embodiment will be described with reference to FIG. 2 as corresponding to FIG. 7 illustrating the heat transfer in the vacuum heat treatment furnace 100 of the conventional example. FIG. 2 shows a case where a plurality of workpieces TA 1, TB are placed in multiple stages in the heat treatment section 16, and a heater 21 is provided at the center along with the heater 17 on the outer peripheral side of the workpieces TA 2, TB 2. Is provided. In FIG. 2, the object to be processed TA is directly heated mainly by the radiant heat of the heater 17 and the object to be processed TB is directly heated mainly by the radiant heat of the heater 21, and the temperature of the object to be processed TA is increased. This is not a process in which the temperature of the workpiece TB is increased.
[0026]
In the conventional example, the distance from the heater 117 to the center of the heating section 116, that is, the distance from the heater 117 to the neutral point between the heaters is L, whereas in the heating section 16 of the present embodiment, this distance. (L / 2), the time required to raise the temperature of the workpieces TA 1 and TB 2 to a predetermined temperature is shortened, resulting in a vacuum heat treatment furnace having a very high temperature raising rate. By providing the heater 21 at the center, the effective volume of the heating section 16 is naturally reduced. However, when the effective diameter of the heat treatment section 16 is 600 mm or more, the reduction rate is 5% or less, so that productivity is improved. In contrast, the effect of increasing the heat treatment rate by providing the heater 21 in the center is greater.
[0027]
3 shows a portion of the heater 21 that is also used as a gas blowing pipe. FIG. 3A is a longitudinal sectional view thereof, and FIG. 3B is a sectional view taken along the line [B]-[B] in FIG. FIG. Since the workpiece T is placed in multiple stages around the outer cylinder 23, and the gas blowing holes 46 are opened in the outer cylinder 23 and at equal angular intervals of 90 degrees in each stage, the gas was placed. It flows radially between the steps of the workpiece T from the center to the outer periphery. When heat treatment is performed such that a reactive gas is flowed to react with the workpiece T, it is optimal because the reaction proceeds uniformly. Further, since it is also used as the heater 21 and does not require a dedicated installation space, it is preferable in terms of productivity without reducing the effective volume of the vacuum heat treatment furnace.
[0028]
The embodiment of the present invention has been described above. Of course, the present invention is not limited to this, and various modifications can be made based on the technical spirit of the present invention.
[0029]
For example, in this embodiment, the vacuum heat treatment furnace is provided with a heater that also serves as a gas blowing pipe, but it may be provided with only a heater in the center without using a gas blowing pipe. Alternatively, only the gas blowing pipe may be provided in the center without using the heater.
[0030]
In this embodiment, the upper and lower two-chamber type vacuum heat treatment furnace has been described. However, the heater and the gas blowing pipe provided at the center of the workpiece simultaneously with the outer peripheral side of the workpiece T are one-chamber vacuum heat treatment. It can also be applied to furnaces.
[0031]
Further, in the present embodiment, the gas blowing pipe heater 21 provided at the center of the heat treatment section 16 is a double cylinder and the gas blowing nozzle 43 is inserted into the inner cylinder 22, but directly to the outer cylinder 23. You may make it insert.
[0032]
In the present embodiment, the gas blower pipe combined heater 21 is a double cylinder, but the single cylinder is vertically divided, the insulating material is sandwiched between the two halves, and the upper and lower ends are closed. A gas blowing hole may be opened in the single cylinder formed so that the heater and the gas blowing pipe are used together. The heater serving as the gas blowing pipe of the present invention is located at the center of the workpiece T. As long as it is installed, the shape is not limited.
[0033]
In the present embodiment, the heat treatment section 16 has a cylindrical shape, but it goes without saying that it may have a rectangular tube shape.
[0034]
【The invention's effect】
The present invention is implemented in the form as described above, and has the following effects.
[0035]
According to the vacuum heat treatment furnace of claims 1 and 2 of the present invention, the gas blowing tube is placed in the center of the workpiece to be loaded in the heat treatment section of the heating chamber from below in a multistage manner. The inert gas or the reactive gas is blown out radially from a plurality of gas blowing holes arranged at equal angular intervals on the outer peripheral surface of the gas blowing pipe in multiple stages and toward the outer peripheral side in each stage. Since it is made to contact a processed material equally, when using reactive gas, reaction advances uniformly .
[0036]
According to the vacuum heat treatment furnace of the second aspect, in addition to the first heater which is placed in multiple stages on the support and is loaded from below into the heat treatment section of the heating chamber, Since the second heater also serving as a gas blowing pipe is provided so as to pass through the center portion, the temperature rise time of the workpiece is shortened as the distance between the heaters is shortened . Although the inner volume of the heat treatment section is reduced by providing the second heater in the center, the effect of improving the heat treatment rate is greater than that, and the productivity of the vacuum heat treatment furnace is increased .
[0037]
According to the vacuum heat treatment furnace of claim 3, the second heater is a double cylinder in which the inner cylinder and the outer cylinder are connected in series, and the gas blown into the inner cylinder is guided into the outer cylinder through the communication hole, Since it is blown out from the gas blowout hole on the outer peripheral surface of the outer cylinder, it is also used as the second heater and the gas blowout pipe, so that the installation space is saved and the effective volume of the heat treatment section is increased, resulting in a vacuum. Improve the productivity of heat treatment equipment .
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a heating chamber of a vacuum heat treatment furnace according to an embodiment.
FIG. 2 is a view showing heat transfer in a heat treatment section of the heating chamber.
FIG. 3 shows a part of a heater / gas blowing pipe inserted and suspended in a heat treatment section of the heating chamber together with a gas flow, A is a longitudinal sectional view, and B is [B]-[B] in A It is sectional drawing of a line direction.
FIG. 4 is a longitudinal sectional view of a conventional two-chamber vacuum heat treatment furnace.
FIG. 5 is a diagram conceptually showing a difference in heating rate when heat treating a plurality of workpieces simultaneously in a heat treatment furnace having different outer dimensions together with FIG. 6, and A is a temperature of a heat treatment region having a small outer dimension. The measurement point and the heater position are shown, and B shows a similar temperature side fixed point in the heat treatment region having a large outer dimension.
6 is a diagram showing the relationship between the heat treatment time and the temperature at each temperature measurement point in the heat treatment regions having different outer dimensions in FIG. 5. FIG.
7 is a diagram for explaining the occurrence of a difference in heating rate in heat treatment regions having different outer dimensions shown in FIG.
FIG. 8 is a diagram showing a gas flow through a gas outlet pipe in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Vacuum chamber 12 Side wall 13 Top cover 15 Heat insulating material 16 Heat processing compartment 17 Heater 18 Conductive shaft 19 Water-cooled electrode terminal 21 Heater 22 Inner cylinder 23 Outer cylinder 24 Conductive annular stopper 25 Insulating cylindrical stopper 26 Insulating annular stopper 32 Water-cooled electrode terminal 33 Conductive shaft 34 Electrode bar 36 Water-cooled electrode terminal 37 Conductive shaft 38 Electrode bar 41 Gas supply source 42 Gas introduction terminal 43 Nozzle 44 Insulating cap 45 Communication hole 46 Gas blowout hole 100 Conventional vacuum heat treatment furnace 101 Prechamber 102 Gate valve 103 Opening and closing door 104 Support base 105 Heat insulating plate 106 Shaft 107 Lifting cylinder 108 Motor fan 109 Heat exchanger 111 Vacuum chamber 121 Gas outlet pipe

Claims

In a vacuum heat treatment furnace provided with a heat treatment section in a vacuum chamber, the center of the object to be processed is almost inserted as the object to be processed is placed in the heat treatment section and loaded on a support table. A gas blowing pipe is provided, and an inert gas or a reactive gas is blown out radially from the plurality of gas blowing holes opened in the gas blowing pipe so as to contact the object to be processed almost evenly. A vacuum heat treatment furnace characterized by that .

In a vacuum heat treatment furnace provided with a heat treatment section in a vacuum chamber, a first heater is provided on the outer peripheral side of a workpiece to be placed and loaded on a support table in the heat treatment section, and for loading the workpiece. Along with this, a second heater and a gas blowing pipe are provided so as to serve as the same member so as to be almost inserted through the central portion of the object to be processed, and the object to be processed is the first heater and the second heater. The inert gas or the reactive gas is blown out radially from the plurality of gas blowing holes opened in the gas blowing pipe so as to come into almost uniform contact with the object to be processed. A vacuum heat treatment furnace .

The same member in which the second heater and the gas blowing pipe are formed is a double cylinder composed of an inner cylinder and an outer cylinder, each of which is closed at an end, and each of the second heaters is externally provided. The inner cylinder and the outer cylinder connected to the power supply terminal from are formed as an electric circuit in which the inner cylinder and the outer cylinder are connected in series, and the gas blowing pipe is connected to the inner cylinder into which the gas from the outside is introduced to the outer cylinder The gas outlet is formed in the outer cylinder in multiple stages in the insertion direction, and the gas blowing holes are formed at equiangular intervals around each stage to form a gas flow path. Vacuum heat treatment furnace .