JP3652915B2

JP3652915B2 - Corrosion-resistant coating forming method on inner surface of cylindrical container and apparatus for forming the same

Info

Publication number: JP3652915B2
Application number: JP07463699A
Authority: JP
Inventors: 拓俊松本; 照正原田; 一男広松; 康森; 義信曽地
Original assignee: Mitsubishi Heavy Industries Ltd; Dai Ichi High Frequency Co Ltd
Current assignee: Mitsubishi Heavy Industries Ltd; Dai Ichi High Frequency Co Ltd
Priority date: 1999-03-19
Filing date: 1999-03-19
Publication date: 2005-05-25
Anticipated expiration: 2019-03-19
Also published as: JP2000268784A

Description

【０００１】
【発明の属する技術分野】
本発明は、ナトリウム二次電池の外筒容器等を構成する円筒容器内面への耐食被覆形成方法及びその形成装置に関するものである。
【０００２】
【従来の技術】
従来のナトリウム二次電池は、硫黄（Ｓ）を含む正極活物資と、ナトリウムを含む負極活物資と、ナトリウムイオンに対して伝導性を有する固体電解質管と、正極端子である円筒缶状の外筒容器と、絶縁リングと、負極端子である封口蓋とを備えている。そして、外筒容器には、正極活物資と中空円筒状導電助材が収納され、該導電助材の中空部には固体電解質管が挿入され、該固体電解質管には負極活物資であるナトリウムが収納されている。
【０００３】
このナトリウム二次電池の放電時には、ナトリウムイオンと硫黄とが反応して腐食性の高い多硫化ナトリウム（Ｎａ₂Ｓｘ）を生成し、該多硫化ナトリウムが硫黄中に拡散することになる。したがって、外筒容器の内面は、電池の放電時等に硫黄あるいは多硫化ナトリウムに曝され、厳しい腐食環境下にある。
そこで、従来におけるナトリウム二次電池の外筒容器の内面には、メッキ又は溶射により耐食被覆が形成され、防食対策が施されている。なお、耐食被覆の材質としては、耐腐食性が高いＦｅ―Ｃｒ系合金等が用いられている。
【０００４】
【発明が解決しようとする課題】
しかしながら、上述した従来の耐食被覆形成方法では、外筒容器の内面全体にわたって厚さが均一な耐食被覆を形成することは困難であり、また、外筒容器の内面に対する耐食被覆の密着性も低いので、耐食被覆にクラックが生じたり、あるいは耐食被覆が外筒容器の内面から剥離したりすることが起こり、多硫化ナトリウムと外筒容器の内面が接触して該外筒容器が腐食されてしまうという不具合があった。
なお、耐食被覆の形成方法としては、メッキ法や溶射法が主流であるが、低コスト化及び信頼性向上の観点から、基材に合金粉末を溶射あるいは塗布し溶融処理を施してコーティングする粉体融着方式も考えられる。即ち、母材表面に配した自溶性合金等の粉体を、バーナ加熱あるいは高周波加熱で１０００℃を超える高温で溶融させ、凝固させて融着させるものいであるが、ナトリウム二次電池の外筒容器のように、胴部と底部を分けるコーナー部において状況が一変する部材に対して、気孔のない緻密な被覆を、クラックなしで形成するのは至難と思われた。
【０００５】
本発明はこのような実状に鑑みてなされたものであって、その目的は、円筒容器の内面に対する密着性が高く、かつ均一な厚さの信頼性の高い耐食被覆を形成すると共に、溶融処理を高速で行い、生産能率の向上を図ることが可能な円筒容器内面の耐食被覆形成方法及びその形成装置を提供することにある。
【０００６】
【課題を解決するための手段】
上記従来技術の有する課題を解決するために、本発明の円筒容器内面への耐食被覆形成方法においては、金属製の円筒容器の内面に、耐食合金の粉体を、層状に配置し、次いで、該容器を回転させながら、容器の胴部に移動方式の高周波加熱を適用して胴部内面の粉体を開口端から底部端に向けて順次溶融させて行くとともに、胴部の加熱が底部端に達する迄の選定された時期に底部の高周波加熱を開始して、胴部加熱の底部端到達と同時に底部の加熱を終了させ円筒容器内面へ耐食被覆を形成させる。
【０００７】
また、本発明の円筒容器内面への耐食被覆形成装置においては、内面に円筒容器を回転自在に支持する支持手段と、前記円筒容器の胴部の周囲に配設されて該胴部を加熱する第１の高周波加熱コイルと、前記円筒容器の底部外面近傍に配設されて該底部を加熱する第２の高周波加熱コイルと、前記第１と第２の高周波加熱コイルに通電するための高周波電源とを備えている。
【０００８】
【発明の実施の形態】
以下、本発明を図示の実施の形態に基づいて詳細に説明する。
【０００９】
図１及び図２は、本発明に係る円筒容器内面の耐食被覆形成方法及びその形成装置の実施形態を示している。図における円筒容器１は、一端が開口した胴部２と、該胴部２の他端に設けられた底部３とから構成される円筒缶状の底付き容器である。この円筒容器１は、図２に示すようなナトリウム二次電池の正極外筒容器として使用され、円筒容器１の内面１ａには耐食被覆４が形成されている。
円筒容器１は、炭素鋼、低合金鋼、ステンレス鋼、Ｎｉ系合金等からなる材料を用いて成形加工されている。また、耐食被覆４は、Ｎｉ，Ｃｒを主成分とし、自溶性をもたらすフラックス生成成分Ｂ，Ｓｉが配合されており、加熱溶融させることが気孔をなくして緻密化するとともに下地金属に融着させるための溶融処理が特に容易に行えるＮｉ系（Ｎｉ−Ｃｒ系とも呼ばれる）の自溶合金を用いて形成されている。この自溶合金は、Ｎｉ，Ｃｒ等の耐食性金属を主成分として含んでいるので、３００〜３５０℃の環境下で多硫化ナトリウム及び硫黄に対する耐腐食性が高く、耐食被覆４の材質として好ましい上、耐食被覆４を容易に形成することが可能である。Ｃｏ系自溶合金についても同様である。
【００１０】
上記耐食被覆４は、図１に示すような耐食被覆形成装置５を用いて円筒容器１の内面１ａに形成されている。この形成装置５は、内面１ａに耐食合金の自溶合金が溶射法、スラリー塗動法、遠心焼結法または遠心配置法によって層状に配置された円筒容器１を回転自在に支持する支持手段６と、円筒容器１の胴部２の周囲に移動可能に配設され、胴部２を加熱する第１高周波加熱コイル（胴部高周波加熱コイル）７と、円筒容器１の底部３の外側近傍に配設され、底部３を加熱する第２高周波加熱コイル（底部高周波加熱コイル）８と、これら第１及び第２高周波加熱コイル７，８の高周波加熱電源（図示せず）と、図示しないトランスフォーマ（変圧器）と、Ａｒ，Ｎ２等の不活性ガスを円筒容器１の内面１ａに導入するガスノズル９とをそれぞれ備えている。
【００１１】
上記支持手段６は、図示しない旋盤の主軸などに回転可能に取付けられるチャック（回転台）１０と、基端が当該チャック１０に装着される容器取付治具１１とを備えており、円筒容器１は、胴部２の開口側を容器取付治具１１の先端内部に挿入してボルト締めすることにより、支持手段６を介して旋盤の主軸などに回転自在に支持されるようになっている。
【００１２】
また、上記第１高周波加熱コイル７は、内径が円筒容器１の胴部２の外径よりも大きなリング状（他の形状でもよい）に形成され、円筒容器１の胴部２に遊嵌された状態で配置されている。しかも、第１高周波加熱コイル７は、図示しない移動装置に取付けられており、この移動装置によりチャック１０側から底部３の付近まで円筒容器１の胴部２を軸方向へ沿って加熱しながら移動できるように構成されている。
さらに、上記第２高周波加熱コイル８は渦巻状コイルを用いて形成されている。しかも、第２高周波加熱コイル８は、図示しない支持装置に取付けられており、該支持装置にて円筒容器１の軸心より偏心した位置に配設され、容器を回転させたときに該円筒容器１の底部３が均一に加熱されるようになっている。なお、第１及び第２高周波加熱コイル７，８は、ケーブル，トランスフォーマなどを介して高周波加熱電源（いずれも図示せず）に接続されている。
【００１３】
一方、上記ガスノズル９は、支持手段６のチャック１０及び容器取付治具１１を経て円筒容器１内の底部３の付近まで貫通配置されている。そして、ガスノズル９の一端は、図示しないＡｒ，Ｎ２等の不活性ガス供給源に連結されており、自溶合金の酸化防止のため、このガス供給源から送られた不活性ガスを先端より円筒容器１の内面１ａ全体に供給するように構成されている。したがって、ガスノズル９は、自溶合金が酸化し易い材料の時のみ必要であって、酸化しにくい材料の場合には不要である。
【００１４】
次に、本発明の実施形態の耐食被覆形成装置５を用いて円筒容器１の内面１ａに耐食被覆４を形成する耐食被覆形成方法を説明する。
まず、本発明に用いる耐食合金の平均粒径は、１０〜３００μｍの範囲内であるのが好ましい。これは、平均粒径１０μｍ未満では、小さい粒子同士が結合して形状が不均一な粗大粒子が形成されることになり、また平均粒径が３００μｍを越えると、スラリー化したときに粉末が沈殿してしまうなどの支障が生じるので好ましくないからである。
そして、耐食被覆４の原料粉末とバインダー等とを混合してスラリー状の塗布剤を調製し、この調製した塗布剤を円筒容器１の内面１ａに均一に塗布する。また、溶射皮膜の場合は、プラズマ溶射機、高速燃焼炎溶射機、フレーム溶射機などの溶射機で上記原料粉末を溶解して円筒容器１の内面１ａに均一に吹き付けて溶射する。さらに遠心焼結法または遠心配置法による場合は円筒容器１の内面１ａの下部に均一に分散させる。
ここで遠心焼結法とは、容器内に粉体を軸方向均等に挿入し、回転により周方向にも均等化させ、遠心力で胴部内面に留まった状態で融点未満の加熱で焼結させる手法を、又、遠心配置法とは容器内に粉体を軸方向均等に装入し、回転により周方向にも均等化させ遠心力で胴部内面に留まらせておく手法をそれぞれ指すものとする。
【００１５】
次いで、図１に示す如く、内面１ａに耐食合金が溶射法、スラリー塗布法、遠心焼結法または円筒容器１の開口側を支持手段６の容器取付治具１１を介して旋盤の主軸などに取付け、回転させる。このように、円筒容器１を回転させるのは、溶融処理時に気孔を低減させるために実施するものである。
この状態で、第１高周波加熱コイル７を支持手段６のチャック１０側から円筒容器１の胴部２に沿って軸方向へ移動させることにより当該胴部２を加熱する。そして、第１高周波加熱コイル７が円筒容器１の底部３の近傍に移動したとき、第２高周波加熱コイル８の加熱を開始して円筒容器１の底部３を加熱する。これにより、円筒容器１の全体が加熱され、第１の高周波加熱コイル７が胴部２の底部端のコーナー部までの溶融を終える時点で底部３内面の粉体を過不足のない温度の溶融状態に到達させるよう第２高周波加熱コイル８の加熱開始時期を選定することにより、胴部２と底部３の粉体の溶融がコーナー部において熱的に同等の状態で同時に終了するところとなって、この円筒容器１の内面１ａの全面に、耐食被覆４が、どの部位にも大きな熱応力を残さずに形成されることになる（図２参照）。この耐食被覆４の厚さは、１０μｍ以上１０００μｍ以下、好ましくは５０〜１００μｍの範囲内であることが良い。厚さが１０μｍ未満では、耐食被覆４が薄すぎて円筒容器１の内面１ａが多硫化ナトリウムにより腐食されるおそれがあり、厚さが１０００μｍを超えると、応力の累積などによって剥がれやすくなり、好ましくないからである。
なお、加熱中は円筒容器１の全体を常時回転させておく。そして、加熱温度は、１０３０〜１２００℃の範囲内であることが好ましい。加熱温度が１０３０℃未満では、温度が低すぎて耐食被覆４の原料粉末を融点以上まで加熱できず、１２００℃を越えると、円筒容器１の強度が低下してしまい、好ましくないからである。また、自溶合金の酸化防止の観点から、不活性ガスをガスノズル１０より円筒容器１の内面１ａに導入し、円筒容器１の内部を不活性ガス雰囲気にしておくことが好ましい。
【００１６】
ここで、本発明の実施形態に係る耐食被覆形成方法及び耐食被覆形成装置５によって、円筒容器１の内面１ａに施された溶射皮膜から耐食被覆４を形成することが可能であるか否かの試験を行った。
供試体としては、ステンレス鋼（ＳＵＳ３０４）からなり、外径６０ｍｍ、肉厚１．５ｍｍ、長さ４００ｍｍに成形加工された円筒容器を用い、その内面には耐食合金の溶射皮膜が施されている。また、耐食被覆形成装置５は、下記の表１で示す試験条件の下、胴部移動加熱をチャック側より開始し、予め設定した底部加熱時間と移動加熱の終了時間が同時になるように、底部加熱を開始した。
【００１７】
【表１】

【００１８】
このような試験を実施して熱電対による円筒容器の各部の温度測定を行うと、胴部全長の１／２位置近傍では１０６５℃、底部中心位置では１０７５℃、底部エッヂでは１０３５℃という結果が得られた。また、移動加熱した胴部の温度差は±２０℃の範囲であり、底部はコイルを４０ｍｍ偏心させた状態で、エッヂ部昇温までに７７秒を要した。しかも、底部の中心とエッヂ部の温度差は４０℃と好結果が得られた。
したがって、円筒容器の内面に施された溶射皮膜の溶融処理は、今回試験の加熱方法により施工可能であり、本発明の実施形態に係る耐食被覆形成方法及び耐食被覆形成装置５によって、円筒容器１の内面１ａに耐食被覆４を形成し得ると判断できる。
【００１９】
このように、本発明の実施形態に係る耐食被覆形成方法にあっては、内面１ａに耐食合金が塗布溶射又は挿入されて均一に分散され、耐食被覆形成装置５の支持手段６に支持された円筒容器１を図外の旋盤の主軸などで回転させながら、第１高周波加熱コイル７を円筒容器１に沿って軸方向へ移動させることにより、円筒容器１の胴部２を加熱すると共に、第１高周波加熱コイル７が円筒容器１の底部３の近傍に移動したとき、第２高周波加熱コイル８の加熱を開始して円筒容器１の底部３を加熱しており、これにより円筒容器１の全体を加熱して該円筒容器１の内面１ａに耐食被覆４を形成しているため、簡単な構造の形成装置５で円筒容器１に対して加熱温度を均一にすることが可能となる。したがって、本実施形態の形成方法によれば、内面１ａに均一な厚さであっても、どの部位にも大きな熱応力が残留していない４が形成された信頼性の高い円筒容器１を得ることができる。
また、本実施形態の第２高周波加熱コイル８は、円筒容器１の底部３の外側近傍で、円筒容器１の軸心より偏心した位置に配設されているため、当該円筒容器１の底部３をより一層均一に加熱することができる。
【００２０】
以上、本発明の実施の形態につき述べたが、本発明は既述の実施の形態に限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々の変形及び変更を加え得るものである。
例えば、円筒容器１は、ナトリウム二次電池の正極外筒容器以外の円筒容器にも使用できる。また、耐食合金の原料粉末が酸化しにくい材料である場合には、円筒容器１内にガスノズル９を貫通配置する必要がない。
【００２１】
【発明の効果】
上述した如く、本発明に係る円筒容器内面の耐食被覆形成方法は、内面に耐食合金が塗布又は溶射された円筒容器を回転させ、この状態で第１高周波加熱コイルを前記円筒容器に沿って移動させることにより前記円筒容器の胴部を加熱し、次いで、前記第１高周波加熱コイルが前記円筒容器の底部近傍に移動したとき、第２高周波加熱コイルの加熱を開始して前記円筒容器の底部を加熱して胴部と底部の加熱が同時に終了するようにし、これにより円筒容器全体を準一方向的に加熱しひいては凝固させて前記円筒容器の内面に耐食被覆を形成しているので、円筒容器の内面に対する密着性が高く緻密であり、かつ均一な厚さと性状を有する残留応力の小さい耐食被覆を確実に形成でき、製品の信頼性向上を図ることができる。
【００２２】
また、他の本発明に係る円筒容器内面の耐食被覆形成装置は、内面に耐食合金、溶射法、スラリー塗布法、遠心焼結法、または遠心配置法によって施工された円筒容器を回転自在に支持する支持手段と、前記円筒容器の胴部の周囲に移動可能に配設され、該胴部を加熱する第１高周波加熱コイルと、前記円筒容器の底部の外側近傍に配設され、該底部を加熱する第２高周波加熱コイルと、前記第１及び第２高周波加熱コイルの高周波加熱電源とをそれぞれ備えているので、上記発明と同様の効果が得られる上、簡単な構造で溶融処理を高速で行い、生産能率を向上させることができる。
【図面の簡単な説明】
【図１】本発明の実施形態に係る円筒容器内面の耐食被覆形成方法を説明するものであって、その方法で使用される耐食被覆形成装置を概念的に示す側面図である。
【図２】本発明の実施形態に係る耐食被覆形成方法により得られた円筒容器を示す断面図である。
【符号の説明】
１円筒容器
１ａ円筒容器の内面
２胴部
３底部
４耐食被覆
５耐食被覆形成装置
６支持手段
７第１高周波加熱コイル
８第２高周波加熱コイル
９ガスノズル
１０チャック
１１容器取付治具[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for forming a corrosion-resistant coating on the inner surface of a cylindrical container constituting an outer container or the like of a sodium secondary battery.
[0002]
[Prior art]
A conventional sodium secondary battery includes a positive electrode active material containing sulfur (S), a negative electrode active material containing sodium, a solid electrolyte tube having conductivity with respect to sodium ions, and a cylindrical can-shaped outer electrode serving as a positive electrode terminal. A cylindrical container, an insulating ring, and a sealing lid that is a negative electrode terminal are provided. The outer casing container contains a positive electrode active material and a hollow cylindrical conductive aid, a solid electrolyte tube is inserted into the hollow portion of the conductive aid, and the solid electrolyte tube has sodium as a negative electrode active material. Is stored.
[0003]
During discharge of the sodium secondary battery, sodium ions and sulfur react to generate highly corrosive sodium polysulfide (Na ₂ Sx), and the sodium polysulfide diffuses into the sulfur. Therefore, the inner surface of the outer casing is exposed to sulfur or sodium polysulfide when the battery is discharged, and is in a severe corrosive environment.
Therefore, a corrosion-resistant coating is formed on the inner surface of the outer casing of the conventional sodium secondary battery by plating or spraying, and anti-corrosion measures are taken. As a material for the corrosion resistant coating, an Fe—Cr alloy or the like having high corrosion resistance is used.
[0004]
[Problems to be solved by the invention]
However, in the conventional corrosion-resistant coating forming method described above, it is difficult to form a corrosion-resistant coating having a uniform thickness over the entire inner surface of the outer cylinder container, and the adhesion of the corrosion-resistant coating to the inner surface of the outer cylinder container is low. As a result, the corrosion-resistant coating cracks or the corrosion-resistant coating is peeled off from the inner surface of the outer cylinder container, and sodium polysulfide and the inner surface of the outer cylinder container come into contact with each other and the outer cylinder container is corroded. There was a problem that.
As a method for forming a corrosion-resistant coating, a plating method or a thermal spraying method is the mainstream, but from the viewpoint of cost reduction and reliability improvement, a powder to be coated by spraying or applying an alloy powder to a base material and subjecting it to a melting treatment. A body fusion method is also conceivable. That is, a powder such as a self-fluxing alloy disposed on the surface of a base material is melted at a high temperature exceeding 1000 ° C. by burner heating or high-frequency heating, and solidified and fused. It seems that it is very difficult to form a dense coating without cracks on a member whose situation changes completely in a corner part that separates the body part and the bottom part like a container.
[0005]
The present invention has been made in view of such a situation, and an object thereof is to form a highly reliable corrosion-resistant coating having a high adhesion to the inner surface of the cylindrical container and a uniform thickness, and a melting treatment. It is an object of the present invention to provide a method and apparatus for forming a corrosion-resistant coating on the inner surface of a cylindrical container that can improve the production efficiency at a high speed.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems of the prior art, in the corrosion-resistant coating forming method on the inner surface of the cylindrical container of the present invention, the corrosion-resistant alloy powder is arranged in a layer on the inner surface of the metal cylindrical container, While rotating the container, the high frequency heating of the moving system is applied to the body of the container to melt the powder on the inner surface of the body sequentially from the opening end to the bottom end, and the heating of the body is performed at the bottom end. High frequency heating of the bottom is started at a selected time until reaching the bottom, and at the same time as the bottom end of the body heating is reached, the bottom heating is terminated and a corrosion-resistant coating is formed on the inner surface of the cylindrical container.
[0007]
Further, in the corrosion-resistant coating forming apparatus for the inner surface of the cylindrical container according to the present invention, the supporting means for rotatably supporting the cylindrical container on the inner surface and the periphery of the cylindrical portion of the cylindrical container are heated. A first high-frequency heating coil; a second high-frequency heating coil disposed near the outer surface of the bottom of the cylindrical container to heat the bottom; and a high-frequency power source for energizing the first and second high-frequency heating coils And.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments.
[0009]
1 and 2 show an embodiment of a method and apparatus for forming a corrosion-resistant coating on the inner surface of a cylindrical container according to the present invention. A cylindrical container 1 in the figure is a cylindrical can-shaped bottomed container including a barrel portion 2 having one end opened and a bottom portion 3 provided at the other end of the barrel portion 2. The cylindrical container 1 is used as a positive electrode outer container of a sodium secondary battery as shown in FIG. 2, and a corrosion resistant coating 4 is formed on the inner surface 1 a of the cylindrical container 1.
The cylindrical container 1 is formed using a material made of carbon steel, low alloy steel, stainless steel, Ni-based alloy, or the like. Further, the corrosion-resistant coating 4 is mainly composed of Ni and Cr, and is blended with flux generating components B and Si that bring about self-solubility. Heat-melting eliminates pores and densifies and fuses to the base metal. Therefore, it is formed using a Ni-based (also referred to as Ni-Cr-based) self-fluxing alloy that can be particularly easily melted. Since this self-fluxing alloy contains a corrosion-resistant metal such as Ni or Cr as a main component, it has high corrosion resistance against sodium polysulfide and sulfur in an environment of 300 to 350 ° C. and is preferable as a material for the corrosion-resistant coating 4. The corrosion-resistant coating 4 can be easily formed. The same applies to Co-based self-fluxing alloys.
[0010]
The corrosion-resistant coating 4 is formed on the inner surface 1a of the cylindrical container 1 using a corrosion-resistant coating forming apparatus 5 as shown in FIG. This forming apparatus 5 has a support means 6 that rotatably supports a cylindrical container 1 in which a self-fluxing alloy of a corrosion-resistant alloy is arranged on the inner surface 1a in a layered manner by a thermal spraying method, a slurry coating method, a centrifugal sintering method, or a centrifugal placement method. A first high-frequency heating coil (body high-frequency heating coil) 7 that is movably disposed around the body 2 of the cylindrical container 1 and heats the body 2, and near the outside of the bottom 3 of the cylindrical container 1. A second high-frequency heating coil (bottom high-frequency heating coil) 8 that is disposed and heats the bottom 3, a high-frequency heating power source (not shown) for the first and second high-frequency heating coils 7, 8, and a transformer (not shown) And a gas nozzle 9 for introducing an inert gas such as Ar or N2 into the inner surface 1a of the cylindrical container 1.
[0011]
The support means 6 includes a chuck (rotary table) 10 that is rotatably attached to a main shaft of a lathe (not shown) and a container attachment jig 11 that has a base end attached to the chuck 10. The body 2 is inserted into the front end of the container mounting jig 11 and tightened with bolts so as to be rotatably supported by a main shaft of a lathe through the support means 6.
[0012]
The first high-frequency heating coil 7 is formed in a ring shape (other shape may be acceptable) whose inner diameter is larger than the outer diameter of the body portion 2 of the cylindrical container 1, and is loosely fitted to the body portion 2 of the cylindrical container 1. It is arranged in the state. Moreover, the first high-frequency heating coil 7 is attached to a moving device (not shown), and this moving device moves while heating the body portion 2 of the cylindrical container 1 along the axial direction from the chuck 10 side to the vicinity of the bottom portion 3. It is configured to be able to.
Further, the second high frequency heating coil 8 is formed using a spiral coil. In addition, the second high-frequency heating coil 8 is attached to a support device (not shown), and is disposed at a position eccentric from the axial center of the cylindrical container 1 by the support device, and the cylindrical container is rotated when the container is rotated. The bottom part 3 of 1 is heated uniformly. The first and second high-frequency heating coils 7 and 8 are connected to a high-frequency heating power source (both not shown) via cables, transformers, and the like.
[0013]
On the other hand, the gas nozzle 9 is disposed through the chuck 10 of the support means 6 and the container mounting jig 11 to the vicinity of the bottom 3 in the cylindrical container 1. One end of the gas nozzle 9 is connected to an inert gas supply source such as Ar, N2 or the like (not shown). In order to prevent oxidation of the self-fluxing alloy, the inert gas sent from the gas supply source is cylindrical from the tip. It is configured to be supplied to the entire inner surface 1 a of the container 1. Therefore, the gas nozzle 9 is necessary only when the self-fluxing alloy is a material that is easily oxidized, and is not necessary when the material is difficult to be oxidized.
[0014]
Next, a corrosion resistant coating forming method for forming the corrosion resistant coating 4 on the inner surface 1a of the cylindrical container 1 using the corrosion resistant coating forming apparatus 5 of the embodiment of the present invention will be described.
First, the average particle diameter of the corrosion resistant alloy used in the present invention is preferably in the range of 10 to 300 μm. When the average particle size is less than 10 μm, small particles are bonded to each other to form coarse particles having a non-uniform shape. When the average particle size exceeds 300 μm, the powder precipitates when slurried. This is because it is not preferable because troubles such as the occurrence of trouble occur.
Then, the raw material powder of the corrosion-resistant coating 4 and a binder are mixed to prepare a slurry-like coating agent, and the prepared coating agent is uniformly applied to the inner surface 1 a of the cylindrical container 1. In the case of a sprayed coating, the raw material powder is melted by a spraying machine such as a plasma spraying machine, a high-speed combustion flame spraying machine, or a flame spraying machine, and sprayed uniformly on the inner surface 1a of the cylindrical container 1 for spraying. Further, in the case of the centrifugal sintering method or the centrifugal arrangement method, it is uniformly dispersed in the lower portion of the inner surface 1a of the cylindrical container 1.
Here, the centrifugal sintering method means that the powder is inserted into the container evenly in the axial direction, and is also equalized in the circumferential direction by rotation, and sintered by heating below the melting point while remaining on the inner surface of the body by centrifugal force. In addition, the centrifugal arrangement method refers to a method in which powder is uniformly loaded in the container in the axial direction, and is also made uniform in the circumferential direction by rotation and kept on the inner surface of the body by centrifugal force. And
[0015]
Next, as shown in FIG. 1, a corrosion resistant alloy is sprayed onto the inner surface 1a by a spraying method, a slurry coating method, a centrifugal sintering method, or the opening side of the cylindrical container 1 via the container mounting jig 11 of the support means 6 to the main spindle of the lathe. Install and rotate. Thus, the cylindrical container 1 is rotated in order to reduce pores during the melting process.
In this state, the first high-frequency heating coil 7 is moved in the axial direction along the body 2 of the cylindrical container 1 from the chuck 10 side of the support means 6 to heat the body 2. And when the 1st high frequency heating coil 7 moves to the vicinity of the bottom part 3 of the cylindrical container 1, the heating of the 2nd high frequency heating coil 8 is started and the bottom part 3 of the cylindrical container 1 is heated. As a result, the entire cylindrical container 1 is heated, and when the first high-frequency heating coil 7 finishes melting up to the corner portion at the bottom end of the body portion 2, the powder on the inner surface of the bottom portion 3 is melted at an appropriate temperature. By selecting the heating start timing of the second high-frequency heating coil 8 so as to reach the state, the melting of the powder of the body portion 2 and the bottom portion 3 ends at the same time in a thermally equivalent state at the corner portion. The corrosion-resistant coating 4 is formed on the entire inner surface 1a of the cylindrical container 1 without leaving a large thermal stress in any part (see FIG. 2). The thickness of the corrosion-resistant coating 4 is 10 μm or more and 1000 μm or less, preferably 50 to 100 μm. If the thickness is less than 10 μm, the corrosion-resistant coating 4 may be too thin and the inner surface 1a of the cylindrical container 1 may be corroded by sodium polysulfide. If the thickness exceeds 1000 μm, it tends to peel off due to accumulated stress, etc. Because there is no.
In addition, the whole cylindrical container 1 is always rotated during heating. And it is preferable that heating temperature exists in the range of 1030-1200 degreeC. This is because if the heating temperature is less than 1030 ° C., the temperature is too low to heat the raw material powder of the corrosion-resistant coating 4 to the melting point or higher, and if it exceeds 1200 ° C., the strength of the cylindrical container 1 decreases, which is not preferable. Further, from the viewpoint of preventing oxidation of the self-fluxing alloy, it is preferable to introduce an inert gas from the gas nozzle 10 to the inner surface 1a of the cylindrical container 1 so that the inside of the cylindrical container 1 is in an inert gas atmosphere.
[0016]
Here, whether or not the corrosion-resistant coating 4 can be formed from the sprayed coating applied to the inner surface 1a of the cylindrical container 1 by the corrosion-resistant coating forming method and the corrosion-resistant coating forming apparatus 5 according to the embodiment of the present invention. A test was conducted.
As a specimen, a cylindrical container made of stainless steel (SUS304) and molded to have an outer diameter of 60 mm, a wall thickness of 1.5 mm, and a length of 400 mm is used, and a thermal spray coating of a corrosion resistant alloy is applied to the inner surface thereof. . Further, the corrosion-resistant coating forming apparatus 5 starts torso moving heating from the chuck side under the test conditions shown in Table 1 below, so that the preset bottom heating time and moving heating end time are simultaneously set. Heating was started.
[0017]
[Table 1]

[0018]
When the temperature of each part of the cylindrical container was measured using a thermocouple after such a test, the results were 1065 ° C. near the half position of the entire body length, 1075 ° C. at the bottom center position, and 1035 ° C. at the bottom edge. Obtained. Further, the temperature difference of the body portion heated and moved was in the range of ± 20 ° C., and the bottom portion required 77 seconds to elevate the edge portion with the coil being eccentric by 40 mm. Moreover, the temperature difference between the center of the bottom and the edge was 40 ° C., and a good result was obtained.
Therefore, the melt treatment of the sprayed coating applied to the inner surface of the cylindrical container can be performed by the heating method of the test this time, and the cylindrical container 1 is processed by the corrosion resistant coating forming method and the corrosion resistant coating forming apparatus 5 according to the embodiment of the present invention. It can be determined that the anticorrosion coating 4 can be formed on the inner surface 1a.
[0019]
Thus, in the corrosion-resistant coating forming method according to the embodiment of the present invention, the corrosion-resistant alloy is applied and sprayed or inserted on the inner surface 1a and uniformly dispersed and supported by the support means 6 of the corrosion-resistant coating forming apparatus 5. While the cylindrical container 1 is rotated by a main shaft of a lathe not shown in the drawing, the first high-frequency heating coil 7 is moved along the cylindrical container 1 in the axial direction, thereby heating the body portion 2 of the

cylindrical container

1 and 1 When the high frequency heating coil 7 moves to the vicinity of the bottom 3 of the cylindrical container 1, heating of the second high frequency heating coil 8 is started to heat the bottom 3 of the cylindrical container 1. Since the corrosion-resistant coating 4 is formed on the inner surface 1a of the cylindrical container 1 by heating, it is possible to make the heating temperature uniform with respect to the cylindrical container 1 with the forming device 5 having a simple structure. Therefore, according to the forming method of the present embodiment, a highly reliable cylindrical container 1 is obtained in which a large thermal stress 4 is not formed in any part even if the inner surface 1a has a uniform thickness. be able to.
In addition, the second high-frequency heating coil 8 of the present embodiment is disposed near the outside of the bottom 3 of the cylindrical container 1 and at a position that is eccentric from the axis of the cylindrical container 1, and therefore, the bottom 3 of the cylindrical container 1. Can be heated more uniformly.
[0020]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the present invention. is there.
For example, the cylindrical container 1 can be used also for cylindrical containers other than the positive electrode outer cylinder container of a sodium secondary battery. Further, when the corrosion-resistant alloy raw material powder is a material that is difficult to oxidize, the gas nozzle 9 does not need to be disposed through the cylindrical container 1.
[0021]
【The invention's effect】
As described above, the method for forming a corrosion-resistant coating on the inner surface of a cylindrical container according to the present invention rotates a cylindrical container whose inner surface is coated or sprayed with a corrosion-resistant alloy, and moves the first high-frequency heating coil along the cylindrical container in this state. To heat the body of the cylindrical container, and then when the first high-frequency heating coil moves to the vicinity of the bottom of the cylindrical container, heating of the second high-frequency heating coil is started and the bottom of the cylindrical container is moved. Since the heating of the body and the bottom is completed at the same time by heating, the entire cylindrical container is quasi-unidirectionally heated and solidified to form a corrosion-resistant coating on the inner surface of the cylindrical container. Therefore, it is possible to reliably form a corrosion-resistant coating having a high adhesiveness to the inner surface and having a uniform thickness and properties and a small residual stress, thereby improving the reliability of the product.
[0022]
In addition, the corrosion-resistant coating forming apparatus for the inner surface of a cylindrical container according to another aspect of the present invention rotatably supports a cylindrical container constructed on the inner surface by a corrosion-resistant alloy, a thermal spraying method, a slurry coating method, a centrifugal sintering method, or a centrifugal arrangement method. Supporting means, a first high-frequency heating coil that is movably disposed around the body of the cylindrical container, and is disposed in the vicinity of the outside of the bottom of the cylindrical container. Since the second high-frequency heating coil to be heated and the high-frequency heating power sources of the first and second high-frequency heating coils are provided, the same effects as the above invention can be obtained, and the melting process can be performed at a high speed with a simple structure. And improve production efficiency.
[Brief description of the drawings]
FIG. 1 is a side view conceptually showing a corrosion-resistant coating forming apparatus used in the method for explaining a corrosion-resistant coating forming method for an inner surface of a cylindrical container according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a cylindrical container obtained by the corrosion-resistant coating forming method according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylindrical container 1a Inner surface 2 of cylindrical container 2 Body part 3 Bottom part 4 Corrosion-resistant coating 5 Corrosion-resistant coating formation apparatus 6 Support means 7 1st high frequency heating coil 8 2nd high frequency heating coil 9 Gas nozzle 10 Chuck 11 Container attachment jig

Claims

Corrosion-resistant alloy powder is arranged in layers on the inner surface of a metal cylindrical container, and then, by rotating the container, applying high-frequency heating to the body of the container, the powder on the inner surface of the body Are melted sequentially from the opening end toward the bottom end, and at the selected time until the body heating reaches the bottom end, high-frequency heating of the bottom is started, and simultaneously with the bottom end of the body heating A method for forming a corrosion-resistant coating on the inner surface of a cylindrical container, wherein heating of the bottom portion is terminated.

A support means for rotatably supporting the cylindrical container, a first high-frequency heating coil disposed around the body of the cylindrical container to heat the body, and disposed near the outer surface of the bottom of the cylindrical container 2. The method according to claim 1, further comprising: a second high-frequency heating coil for heating the bottom portion; and a high-frequency power source for energizing the first and second high-frequency heating coils. Corrosion-resistant coating forming apparatus for the inner surface of a cylindrical container.

The said 2nd high frequency heating coil is eccentrically arrange | positioned from the axis line of the said cylindrical container, The corrosion-resistant coating formation apparatus to the cylindrical container inner surface of Claim 2 characterized by the above-mentioned.