JP3798219B2 - Joined body and joining method of iron-based alloy members - Google Patents

Description

【００１８】
【表２】

【００１９】
上記加熱温度で接合後、室温まで冷却し、接合工程が終了するが、このときの冷却速度が接合部、母材の強度特性に大きな影響を与える。５００℃までの冷却速度が１℃／分〜１００℃／分、かつ５００℃から１５０℃までの冷却速度が２℃／分以上で良好な結果を得ることができる。５００℃までの冷却速度が１００℃／分以上であれば、冷却速度が速すぎるために部材内に温度差がつきやすく、熱応力によって接合部に割れが発生する。また、５００℃までの冷却速度が１℃／分以下である場合、もしくは５００℃から１５０℃までの冷却速度が２℃／分未満の場合にはＢ化合物が接合層に析出する。このＢ化合物は直径が１μｍ未満と小さいものの、個数が多く、接合層５０μｍあたり２個以上となる。その結果、接合部に負荷が作用した際にはこれらＢ化合物が破壊の起点となるため、接合部の強度が低下する。
【００２０】
ところで、接合体を構成する鉄基合金部材の組成としては特に限定されるものではなく、表３に化学成分を例示するような、極く一般的に用いられる接合体素材であればよい。
【表３】

【００２１】
なお、Ｃｒ：１０．０〜１５．０質量％、Ｎｉ：２．５〜６．５質量％の鉄基合金、もしくはＣｒ：０．７５〜１．１０質量％、Ｍｏ：０．１５〜０．２５質量％の場合には、４０質量％以上のＮｉを含有する接合層を有することによって特に優れた衝撃特性が得られるので、特に好適な接合体が得られる。
【００２２】
また、Ｃｒ，Ｓｉは、周知のとおり、インサート材の融点を降下させると共に、鉄基合金製の部材とのぬれ性を改善させる役割を果たすものである。したがって、鉄基合金製の部材同士を上記温度範囲内の加熱温度で接合して、部材同士の接合における欠陥の発生を防止するためには、インサート材中のＣｒ，Ｓｉの何れか一方、もしくは両方が含有されていることが好ましい。最も好ましいインサート材としては、例えばＮｉ：６０質量％以上、Ｂ：１．０質量％〜５．０質量％を含有し、かつＣｒ：５．０質量％〜２０質量％とＳｉ：１．０質量％〜１０質量％の何れか一方、もしくは両方を含有するものである。
【００２３】
ところで、Ｂが１．０質量％未満の場合はインサート材の液相線温度が高い（約１３５０℃以上）ので上記温度では接合することができず、逆に５．０質量％を超える場合はＢが多すぎるために接合層中のＢ化合物の個数が多くなり接合部の強度が得られない。Ｃｒ，Ｓｉに関しては、含有量が上記範囲未満の場合には液相線温度が高く（約１４３０℃）、また部材とのぬれ性が悪いために接合層に欠陥が生じ易く、逆に含有量が上記範囲の上限を超えている場合には接合層内にＢ化合物を生成しやすく接合部の強度を得ることができない。
【００２４】
また、インサート材としては、一般にアモルファス箔が使用されるが、その形態は特に制限を受けるものではなく、必要に応じて粉末、メッキ膜、溶射皮膜等の形態を採ることができる。接合層の厚さは重石重量や圧縮荷重で調整することができ、またスペーサ等を利用して調節することもできる。また、インサート材を大気中で加熱すると接合層内に酸化物が含まれ強度が低下することになるので、インサート材は真空中もしくはＡｒ等の不活性ガス雰囲気やＮ２ガス雰囲気中で加熱するのが好ましい。さらに、インサート材の加熱時間は１分間〜１８０分間の範囲が好ましく、この時間内であれば界面での剥離を生じることがなく、また十分な寸法精度を得ることができる。さらに、接合体の製造コスト、母材に対する熱影響を考慮すると、加熱時間は５分間〜６０分間がより好ましく、より高強度の接合部を有する接合体を製造することができる。
【００２５】
【実施例】
本発明の実施例１を説明する。この例は下記表４に示す化学組成の鉄基合金製のブロックと上記表１中のＢＮｉ−２相当のインサート材とを用い、図３に示すように鉄基合金製のブロック１とブロック２との間にインサート材３を介し、このインサート材３を加熱溶融して鉄基合金製のブロック同士１，２を接合し、接合層の厚さと強度との関係を調査したものである。この時の接合条件は加熱温度１１００℃で３０分間保持した。また、このブロック１，２の接合に際しては、接合面間に圧縮荷重を作用させることにより、もしくはスペーサにより所定間隔の隙間を設けることによって、種々の厚さの接合層の接合体を製作した。その後、各接合体より引張試験片を切り出して接合体の強度評価を行った。評価結果を表５に示す。なお、引張試験片は平行部の直径が６ｍｍ、長さ３２ｍｍであり、平行部の中央において、負荷方向に対して接合面が垂直になるように加工してある。また、接合部断面をＥＰＭＡを用いてライン分析し、その分析結果から４０質量％以上のＮｉを含有する接合層が形成されていることを確認した。
【００２６】
【表４】

【００２７】
【表５】

【００２８】
上記表５によれば、本発明に係る接合温度内であっても接合体の接合層の厚さが２．０ｍｍを超える場合には、接合部が低強度になっている。このことから本発明では接合層の厚さを２．０ｍｍ以下とするものである。なお、より好ましい接合層の厚さは０．０１０ｍｍ〜０．２００ｍｍであり、さらに好ましい接合層の厚さは０．０２０ｍｍ〜０．１００ｍｍである。
【００２９】
本発明の実施例２を説明する。この例は上記実施例１と同様、上記表４に示す化学組成の鉄基合金製のブロックと上記表１中のＢＮｉ−２相当のインサート材とを用い、図３に示すように鉄基合金製のブロック１とブロック２との間にインサート材３を介し、このインサート材３を加熱溶融して鉄基合金製のブロック同士１，２を接合した。この実施例２においては、ブロック同士の接合条件として、表６に示すように、インサート材を加熱溶融させる温度およびその溶融温度での保持時間を種々変更し、また接合温度から５００℃までの冷却速度は１０〜５０℃／ｍｉｎとなるよう調節した。そして、製作した接合体を用いて次のごとき調査を行った。なお、この実施例２の場合、４０質量％のＮｉを含有する接合層の厚さは全て０．０５ｍｍである。
【００３０】
【表６】

【００３１】
接合体より引張試験片を切り出して接合体の引張試験を行った。また、引張試験片を切り出した接合体の残部からミクロ試験片を採取し、接合部の組織を顕微鏡で観察すると共に、ＥＰＭＡにより分析した。さらにマイクロビッカース硬度計により、０．４９Ｎの荷重で接合層中央部の硬度を測定した。なお、引張試験片は平行部の直径が６ｍｍ、長さ３２ｍｍであり、平行部の中央において負荷方向に対して接合面が垂直になるように加工してある。
【００３２】
引張試験片の引張試験および接合部の組織観察結果は上記表６に示すとおりである。上記表６によれば、接合するときの加熱温度が１０５０℃以上の本実施例の場合、接合層内に１μｍ以上のＢ化合物が２個／５０μｍ以下しか存在していないため、接合体の強度は母材の強度と同等もしくはそれ以上になっている。
特に、接合温度が１１００℃以上の場合には、接合体の引張試験であるにもかかわらず、母材部で破断している。しかし、接合温度が１０５０℃未満の場合には、接合層内に直径１μｍ以上のＢ化合物が３個／５０μｍ以上残っているため、接合体は接合部で破断している。このように接合体が接合部で破断するのは、接合部が低強度、もしくは高強度であっても伸びが得られず脆くなっているためであると考えられる。また、上記表６によれば、接合層内におけるＢ化合物の析出特性、強度特性は加熱温度での保持時間の長短に殆ど影響されず、加熱温度で決まることがわかる。
【００３３】
本発明の実施例３を説明する。この例は上記表４に示す組成の鉄基合金を、上記表１中のＢＮｉ−２相当のインサート材である、２０μｍ厚さの４枚のアモルファス箔を用いて接合したもので、図４に示すように、空洞部７を有するブロック１と相手のブロック２とを接合した後、空胴部分の高さ変化を接合前後で比較したものである。より詳しくは、加熱温度１１９０℃にて接合を行い、接合時には１ＭＰａの面圧になるように荷重を負荷した。このとき接合時の保持時間を種々変化させ、保持時間に対する接合前後の変形量を調べたものである。
なお、接合前後の変形量は接合前のブロック１の空胴部分の高さをａ０とし、接合後の空間部分の高さをａとしたとき、[[ａ０+インサート材厚さ（０．０２×４＝０．０８ｍｍ）]−ａ]で定義し、ノギスにて測定し、合計５回測定した平均値を用いている。
【００３４】
そして、試験後に接合層の断面を鏡面研磨しＥＰＭＡにより分析した結果、接合後における４０質量％以上のＮｉを含有する接合層の厚さはすべて０．０３ｍｍ〜０．０６ｍｍの範囲であった。また、接合時における加熱温度での保持時間と接合前後の変形量は、下記表７に示すとおりであった。
【００３５】
【表７】

【００３６】
上記表７中において、接合のための保持時間があまりにも短い０．５分、０．７５分の場合には接合後の寸法測定時に接合部が剥離してしまい、接合後の寸法測定ができなかった。このように接合部が剥離してしまうのは、接合界面における反応が不十分であり、界面強度が弱かったことが原因であると想定される。
【００３７】
また、保持時間が長い２４０分、３００分、３６０分の場合には母材が変形し、接合後の変形量が大きかった。一方、保持時間が適切である１分〜１８０分の場合は、界面に剥離が生じておらず、また接合後の変形量も少ないために、本方法によって優れた寸法精度で接合体を作製することができる。ここで、保持時間が長い場合には接合体の製造コストが高くなる欠点があり、逆に保持時間が短い場合には大型の接合体を作製する場合の接合面内の温度差によって、接合部が低強度になる可能性があるので、接合のための時間としては５分〜６０分が好ましい。
【００３８】
本発明の実施例４を説明する。この例は下記表８に示す組成の鉄基合金を用いると共に、表１中のＢＮｉ−２相当のインサート材を用い、加熱溶融による接合によって接合条件を決定した例である。この場合には下記表９に示すように、インサート材を加熱溶融させる温度およびその温度での保持時間を種々変更して接合体を製造したものである。そして、引張試験片の切り出し残部からミクロ試験片を採取して接合部の組織を顕微鏡で観察し、ＥＰＭＡにより分析した。なお、接合温度から５００℃までの冷却速度は１０〜５０℃／ｍｉｎとなるように調節した。また、引張試験方法は上記実施例１の場合と同じである。なお、４０質量％のＮｉを含有する接合層の厚さは全て０．０８ｍｍである。下記表９に引張試験片および接合部の組織観察結果を示す。
【００３９】
【表８】

【００４０】
【表９】

【００４１】
表９によれば、部材同士を接合するときの加熱温度が１０４０℃以上の場合には、接合層内に直径１μｍ以上のＢ化合物が５０μｍ当たり２個以上存在せず、接合部の強度は母材と同等以上の強度になっている。
さらに、この接合体の接合層内におけるＢ化合物の生成特性および強度特性は加熱温度での保持時間の長短に殆ど影響されず、加熱温度によって決まることが分かる。一方、接合するときの加熱温度が１０４０℃未満の場合には、接合層内に１μｍ以上のＢ化合物が５０μｍ当たり３個以上残っているので、この接合層は高硬度になっている。そのため、低強度であるが、上記の場合と同様、この接合層の組織特性および強度特性は接合時における加熱温度での保持時間には影響されず、加熱温度によって決まるものである。
【００４２】
本発明の実施例５を説明する。この例は上記表８に示す組成の鉄基合金を用い、表１０に示す組成のインサート材を介し加熱溶融して接合する方法について検討した。その際、表１１に示すような接合温度・接合時間で接合体を製造したものである。接合後、母材の調質のため７００℃にて焼戻しを行った後、実施例１と同様の引張試験片を切り出し、引張試験に供するとともに、残部より切り出した接合部断面を樹脂に埋め込み後、鏡面研磨し、ＥＰＭＡ分析を行った。
【００４３】
【表１０】

【００４４】
【表１１】

【００４５】
表１１によれば、部材同士の接合温度が１２００℃以上であれば、接合層内に１μｍ以上のＢ化合物が５０μｍ当たり２個以上存在せず、高い接合体の強度が得られる。一方、接合温度が１１９０℃未満の場合には接合層内のＢ化合物が５０μｍ当たり３個以上存在するため、接合体の強度は低い。
【００４６】
本発明の実施例６を説明する。この例は上記表８に示す組成の鉄基合金を用い、表１０に示す組成のインサート材を介し加熱溶融して接合する方法について検討した。その際、表１２に示すような接合温度・時間にて接合し、さらに表１２に示す各冷却速度にて冷却した。なお、冷却速度の調節は冷却時の冷却ガスの圧力を調節、もしくはヒータにて加熱しながら冷却することによって行っている。なお、接合温度から５００℃まで間において冷却速度は常に一定にならないが、ここで用いているのは接合温度から５００℃の温度差を冷却に要する時間で割ることによって求めた平均の冷却速度である。接合後、実施例５と同様に母材調質のための焼戻しを行い、その後、接合体より引張試験片を切り出し引張試験に供すると共に、残部より採取した接合体を鏡面に研磨し、ＥＰＭＡによって接合層内のＢ化合物を分析した。結果を表１２に示す。
【００４７】
【表１２】

【００４８】
表１２に示すように、接合温度がインサート材の液相線温度より４０℃未満の温度である１１７０℃、１１８０℃である場合には、保持時間に関わらず接合層内にＢ化合物が生成しているため、接合体は低強度である。本Ｂ化合物はインサート材が溶融している間に晶出したものと推測される。それに対し、接合温度がインサート材の液相線温度より４０℃以上高い温度である１２００℃、１２３０℃、１２５０℃の場合、接合温度から５００℃までの冷却速度が１℃／分以上１００℃／分以下であり、かつ５００℃から１５０℃までの冷却速度が２℃／分以上の場合には接合層５０μｍあたりのＢ化合物が２個以下であり、接合体の強度が高い。そして接合温度から５００℃までの冷却速度が１００℃／分以上の場合には接合部にクラックが発生したため、引張試験片を切り出すことができなかった。ただし、健全部より切り出した接合層には５０μｍあたり２個以下のＢ化合物しか見られない。さらに５００℃までの冷却速度が１℃／分未満、および５００℃から１５０℃までの冷却速度が２℃／分未満の場合には接合層５０μｍ当たりのＢ化合物数が２個以上であり接合体の強度が低い。接合層内のＢ化合物は接合温度からの冷却中に析出したものと思われる。
【００４９】
【発明の効果】
以上説明したように、本発明に係る鉄基合金部材同士の接合体は、接合層の強度が母材である鉄基合金部材と同程度の高い強度を有するので、高強度を要求される用途に対して安心して適用することができる。
【００５０】
また、本発明に係る鉄基合金部材同士の接合方法によれば、接合層の強度を母材である鉄基合金部材と同程度にまで高いものとすることができ、高い強度を有する接合体を製造することができる。
【図面の簡単な説明】
【図１】接合層におけるボロン化合物個数の計数の説明図である。
【図２】ボロン化合物の直径を定義するための説明図であって、ａは化合物が円形、ｂは楕円、ｃは滴形、ｄは角形の場合である。
【図３】本発明に係る接合体の展開斜視図である。
【図４】本発明に係る別の接合体の説明図であって、ａは展開斜視図、ｂは斜視図である。
【符号の説明】
１，２：鉄基合金部材 ３：インサート材 ４：接合層
５：ボロン化合物 ６：接合体 ７：空洞部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a joined body and a joining method of iron-based alloy members, and more particularly, a joined body having excellent mechanical strength, and a joining method capable of maintaining excellent mechanical strength. In the technical field, examples of iron-based alloy members include petroleum refining and piping for the chemical industry.
[0002]
[Prior art]
There are various methods for assembling members into products, and typical ones include mechanical fastening and welding with bolts and nuts. Among them, welding is widely used because metallurgical bonding between metal materials can be easily obtained. However, in welding, since it is necessary to heat up to a temperature range in which the base material is locally melted, occurrence of welding deformation is unavoidable. For this reason, the product after welding has a shape different from the design, and design performance cannot be realized, or significant correction work may be required to remove welding deformation.
[0003]
On the other hand, diffusion bonding is known as a method for bonding metal materials. In diffusion bonding, there is no local heating and melting of the base material at the time of bonding, or it is only necessary to heat and melt a thin insert material with a low melting point. There are few features. On the other hand, however, there is a problem to be solved that it is difficult to obtain the strength of the joint in diffusion bonding, and the mechanical properties are difficult. In other words, the joints of members require joint strength that is equivalent to that of the base material and high dimensional accuracy that satisfies design performance with little deformation, but only welding strength for welding and only deformation for diffusion bonding. Any one of the joining methods is satisfied.
[0004]
In view of such a situation, Japanese Patent Application Laid-Open No. 9-262685 discloses a technique that makes it possible to improve the mechanical characteristics, which is a problem of the diffusion bonding, using the latter diffusion bonding. According to the “stainless steel joining method” proposed in Japanese Patent Application Laid-Open No. 9-262585, it can be seen that although the joint strength is improved by improving the mechanical properties of the base material, it may still be insufficient. It was.
[0005]
[Problems to be solved by the invention]
Then, this invention aims at providing the joining body and joining method which were excellent in joining strength in the joining body and joining method of the iron base alloy members joined by diffusion joining.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have made the present invention through repeated studies on diffusion bonding that has been conventionally performed.
[0007]
The present inventors have investigated the cause of not obtaining sufficient mechanical properties, in particular, bonding strength even though a bonded body is manufactured using the bonding method proposed in the above-mentioned JP-A-9-262585. As a result, it was clarified that the cause was boron (hereinafter referred to as B) contained in the insert material. Addition of a few percent of B is effective because of the low melting point of the insert material, the formation of an amorphous foil, and the refining action in the joining process. It was found that by concentrating, the joint was broken and the strength of the joined body was lowered.
[0008]
Therefore, the present invention has been made by further earnest research, and the joined body of the iron-based alloy members according to the present invention (Claim 1) is obtained by inserting two or more iron-based alloy members into the insert. It is a joined body formed by diffusion bonding through a material, wherein the insert material is, B: 1.0% by mass to 5.0% by mass and Cr: 5.0% by mass to 20% by mass and Si: 1.0% by mass to 10% by mass or bothConsists of remaining Ni and inevitable impuritiesA nickel-based alloy,A bonding layer is formed between the iron-based alloy members,The remaining nickel content is 40% by mass or more and the thickness is 2.0 mm or less.And,And,Measured at the center plane perpendicular to the stacking direction of the insert materialThe average number of boron compounds with a diameter of 1 μm or more is 2 or less per 50 μmIt is a joined body characterized by being. Moreover, the joined body of the iron base alloy members according to the present invention (Claim 2) is a joined body formed by diffusion joining two or more members made of an iron base alloy with an insert material interposed therebetween. The insert material contains B: 1.0% by mass to 5.0% by mass, and Cr: 5.0% by mass to 20% by mass and Si: 1.0% by mass to 10% by mass. One or both of them are contained, and Fe: 5 mass% or less, C: 1.1 mass% or less, Co: 1 mass% or less, Mo: 4 mass% or less, Cu: 4 mass% or less A nickel-base alloy comprising the remainder Ni and unavoidable impurities, and a joining layer is formed between the iron-base alloy members, and the joining layer has a remaining nickel content of 40% by mass or more. The thickness is 2.0 mm or less and is perpendicular to the stacking direction of the insert material The number of the measured diameter 1μm or more boron compounds in the central plane of the direction is bonded body, characterized in that an average 2 or less per 50 [mu] m.In the joined body of the present invention, the iron-based alloy member is suitably applied to equipment for petroleum refining and chemical industries, for example, piping (claims).3).
[0009]
The present invention (claims)4) Is a method for joining iron-base alloy members between members made of iron-base alloy., B: 1.0% by mass to 5.0% by mass and Cr: 5.0% by mass to 20% by mass and Si: 1.0% by mass to 10% by mass or bothThe composition of the balance Ni and inevitable impuritiesAfter interposing an insert material made of a nickel-based alloy and melting the insert material by heating for 1 minute to 180 minutes in a temperature range of 40 ° C. or higher than the liquidus temperature of the insert material to 1300 ° C. or lower, By cooling to 500 ° C. at a cooling rate of 1 ° C./min to 100 ° C./min, and then cooling to 150 ° C. at a cooling rate of 2 ° C./min or more,A bonding layer is formed between members made of an iron-based alloy,The remaining nickel content is 40% by mass or more and the thickness is 2.0 mm or less.And,And,Measured at the center plane perpendicular to the stacking direction of the insert materialThe average number of boron compounds with a diameter of 1 μm or more is 2 or less per 50 μmIt is the joining method characterized by being. Moreover, the joining method of the iron base alloy members which concerns on this invention (Claim 5) contains B: 1.0 mass%-5.0 mass% between the members made from an iron base alloy, and One of or both of Cr: 5.0% by mass to 20% by mass and Si: 1.0% by mass to 10% by mass is contained, and Fe: 5% by mass or less, C: 1.1% by mass Hereinafter, Co: 1% by mass or less, Mo: 4% by mass or less, Cu: 4% by mass or less, containing an insert material made of a nickel-based alloy having a composition of the balance Ni and inevitable impurities The insert material is melted by heating for 1 minute to 180 minutes in a temperature range of 40 ° C. or higher to 1300 ° C. or lower than the liquidus temperature of the insert material, and then 1 ° C./min to 100 ° C./min. Cool to 500 ° C at a cooling rate, then 1 at a cooling rate of 2 ° C / min or more. By cooling to 0 ° C., a joining layer is formed between members made of an iron-based alloy, and the joining layer has a remaining nickel content of 40% by mass or more and a thickness of 2.0 mm or less. In addition, the bonding method is characterized in that the number of boron compounds having a diameter of 1 μm or more measured on the center plane in a direction perpendicular to the stacking direction of the insert material is an average of 2 or less per 50 μm.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors pay attention to diffusion bonding that can obtain high dimensional accuracy with little deformation of the joint, and conduct various studies on how to improve the mechanical characteristics of the resulting bonded body. It was. B in insert material is indispensable for lowering melting point, making amorphous foil of insert material, and refining action at the time of joining, so insert material mainly containing nickel containing B (hereinafter referred to as Ni) is used. Then, investigation was made focusing on liquid phase diffusion bonding in which the insert material is melted. As a result, when performing liquid phase diffusion bonding that melts such an insert material, Ni cannot be completely diffused into the base material, and remains as a bonding layer containing Ni at the joint portion between members. I found it. In terms of the fact that a bonding layer containing Ni remains in the bonded portion, it is considered that it is classified into the category of brazing rather than diffusion bonding.
[0011]
And as mentioned above, it was ascertained that the reason why sufficient mechanical properties could not be obtained for the joined body was the B compound in the joining layer and the thickness of the joining layer, leading to the present invention. . Although the bonding layer can be characterized as a region containing Ni of 40% by mass or more, this bonding layer has a great influence on the mechanical properties of the bonded portion. Specifically, it is preferable for the toughness of the entire bonded body that the bonding layer containing Ni of 40% by mass or more disappears rather than disappearing, and the thickness of the remaining bonding layer is good at 2.0 mm or less. A result can be obtained, and when the thickness of the bonding layer exceeds 2.0 mm, the bonding layer having low strength dominates the strength of the bonded body, so that the mechanical strength of the bonded portion is reduced. I found out. The contents of Ni and B compounds in the bonding layer described below are measured by EPMA (Electron Probe Micro Analyzer) or the like.
[0012]
Furthermore, it was found that the B compound in the bonding layer containing 40% by mass or more of Ni greatly affects the mechanical properties of the bonded body. That is, the compound B has a small influence on the strength of the joint if the number of compounds having a diameter of 1 μm or more is 2 or less per 50 μm on the average in the cross section of the bonding layer, and bonding is performed if the average is 3 or more per 50 μm. It turned out that the intensity | strength of a part falls remarkably. As shown in FIG. 1, the number of B compounds means that the B compound 5 appears almost at the center of the bonding layer 4, so that the bonding layer 4 between the body members 1 and 2 of the bonded body 6 is cut vertically. It is the number that appears between 50 μm of the bonded cross section. Further, since the shape of the B compound 5 is not necessarily circular, the longest portion of the various shapes as shown in FIGS. 2A to 2D is defined as the diameter d.
[0013]
Next, in the present invention for obtaining a joined body in which the B compound having a diameter of 1 μm or more in the joining layer having a thickness of 2.0 mm or less containing nickel of 40% by mass or more mentioned above becomes an average of 2 or less per 50 μm. Such a joining method will be described. What is important in this joining method is that the present invention has been obtained with the knowledge that the joining temperature and the cooling rate from the joining temperature are obtained.
[0014]
In other words, there are two processes for generating the B compound in the bonding layer, one is holding at the bonding temperature, crystallization in the molten state of the insert material, and the other is holding at the bonding temperature. Thereafter, precipitation during cooling. In order to suppress the formation of the B compound in both processes, it is necessary to appropriately control the bonding temperature affecting crystallization and the cooling rate affecting precipitation. Therefore, in the present invention, the conditions under which B compound generation can be suppressed while taking into account the base material characteristics are as follows. The bonding temperature is a temperature range of 40 ° C. or higher to the liquidus temperature of the insert material to 1300 ° C. or lower, and the cooling rate is the bonding temperature. From the temperature to 500 ° C., it is 1 ° C./min to 100 ° C./min, and from 500 ° C. to 150 ° C., the knowledge of 2 ° C./min or more has been obtained, and the present invention has been achieved. The reasons for these limitations will be described in detail below.
[0015]
A good joined body can be obtained by setting the temperature for joining (joining temperature) to a temperature range of 40 ° C. to 1300 ° C. lower than the liquidus temperature of the insert material. When the heating temperature at the time of joining is a low temperature lower than 40 ° C. from the liquidus temperature of the insert material, the B compound is crystallized in the joining layer. Since the crystallized B compound is coarse and large in number with a diameter of 1 μm or more, it becomes a starting point of breakage when a load is applied to the joint, so that the joint has low strength. On the other hand, if the temperature exceeds 1300 ° C., the base material is affected by heat and the base material is deteriorated in toughness. Further, when an iron-base alloy of Cr: 10.0 to 15.0 mass% and Ni: 2.5 to 6.5 mass% is used as a base material, the insert is only required if the heating temperature during bonding is 1050 ° C. or higher. Since the wettability of the material is improved and defects in the joint portion are reduced, good joining characteristics can be obtained. Furthermore, when the heating temperature at the time of joining is in the temperature range of 1100 ° C. to 1200 ° C., the strength of the joined portion is equal to or higher than that of the base material, which is particularly desirable as a joined body.
[0016]
Further, the insert material that can be used needs to contain Ni of 60% by mass or more. For example, a JIS standard Ni insert material (JIS Z3265) shown in Table 1 and a JIS standard self-fluxing alloy shown in Table 2 All of (JIS Z8303) can be used. When a Ni-based alloy having Ni of 60% by mass or less is used, the Ni concentration of the bonding layer decreases due to melting of the Fe-based alloy base material when the insert material is melted, and the Ni concentration of the bonding layer becomes less than 40% by mass. There is concern about a decrease in toughness.
[0017]
[Table 1]

[0018]
[Table 2]

[0019]
After joining at the above heating temperature, it is cooled to room temperature, and the joining process is completed. The cooling rate at this time greatly affects the strength characteristics of the joined part and the base material. Good results can be obtained when the cooling rate to 500 ° C. is 1 ° C./min to 100 ° C./min and the cooling rate from 500 ° C. to 150 ° C. is 2 ° C./min or more. If the cooling rate up to 500 ° C. is 100 ° C./min or more, the cooling rate is too high, so that a temperature difference is likely to occur in the member, and cracks occur in the joint due to thermal stress. Further, when the cooling rate to 500 ° C. is 1 ° C./min or less, or when the cooling rate from 500 ° C. to 150 ° C. is less than 2 ° C./min, the B compound precipitates in the bonding layer. Although this B compound has a small diameter of less than 1 μm, it has a large number and is 2 or more per 50 μm of the bonding layer. As a result, when a load acts on the joint, these B compounds serve as starting points for destruction, so that the strength of the joint is reduced.
[0020]
By the way, the composition of the iron-based alloy member constituting the joined body is not particularly limited, and any joined material that is generally used as exemplified in Table 3 may be used.
[Table 3]

[0021]
In addition, Cr: 10.0-15.0 mass%, Ni: 2.5-6.5 mass% iron-base alloy, or Cr: 0.75-1.10 mass%, Mo: 0.15-0 In the case of .25% by mass, particularly excellent impact characteristics can be obtained by having a joining layer containing 40% by mass or more of Ni, so that a particularly suitable joined body is obtained.
[0022]
As is well known, Cr and Si lower the melting point of the insert material and improve the wettability with the iron-based alloy member. Therefore, in order to join the members made of iron base alloy at the heating temperature within the above temperature range and prevent the occurrence of defects in the joining of the members, either one of Cr and Si in the insert material, or It is preferable that both are contained. As the most preferable insert material, for example, Ni: 60% by mass or more, B: 1.0% by mass to 5.0% by mass, Cr: 5.0% by mass to 20% by mass, and Si: 1.0 It contains either one or both of mass% to 10 mass%.
[0023]
By the way, when B is less than 1.0% by mass, the liquidus temperature of the insert material is high (about 1350 ° C. or higher), so that it cannot be bonded at the above temperature, and conversely when it exceeds 5.0% by mass. Since there are too many B, the number of B compounds in a joining layer increases, and the intensity | strength of a junction part cannot be obtained. Regarding Cr and Si, when the content is less than the above range, the liquidus temperature is high (about 1430 ° C.), and the wettability with the member is poor, so that the bonding layer is likely to be defective, and conversely the content When the value exceeds the upper limit of the above range, a B compound is easily generated in the bonding layer, and the strength of the bonded portion cannot be obtained.
[0024]
Further, as the insert material, an amorphous foil is generally used, but the form is not particularly limited, and a form such as a powder, a plating film, or a sprayed coating can be adopted as necessary. The thickness of the bonding layer can be adjusted by the weight of the weight or the compressive load, and can also be adjusted using a spacer or the like. In addition, when the insert material is heated in the air, the oxide is contained in the bonding layer and the strength is lowered. Therefore, the insert material is heated in a vacuum, an inert gas atmosphere such as Ar, or an N2 gas atmosphere. Is preferred. Furthermore, the heating time of the insert material is preferably in the range of 1 minute to 180 minutes. Within this time, peeling at the interface does not occur, and sufficient dimensional accuracy can be obtained. Furthermore, in consideration of the manufacturing cost of the bonded body and the thermal effect on the base material, the heating time is more preferably 5 minutes to 60 minutes, and a bonded body having a higher strength bonded portion can be manufactured.
[0025]
【Example】
A first embodiment of the present invention will be described. This example uses an iron-based alloy block having the chemical composition shown in Table 4 below and an insert material equivalent to BNi-2 in Table 1 above, and as shown in FIG. The insert material 3 is heated and melted between the two and the iron-based alloy blocks 1 and 2 are joined together, and the relationship between the thickness and strength of the joining layer is investigated. The bonding conditions at this time were maintained at a heating temperature of 1100 ° C. for 30 minutes. Further, when the blocks 1 and 2 were joined, joints of joining layers having various thicknesses were manufactured by applying a compressive load between the joining surfaces or by providing gaps with a predetermined interval with spacers. Then, the tensile test piece was cut out from each joined body, and the strength evaluation of the joined body was performed. The evaluation results are shown in Table 5. The tensile test piece has a parallel portion with a diameter of 6 mm and a length of 32 mm, and is processed so that the joint surface is perpendicular to the load direction at the center of the parallel portion. Moreover, the cross-section of the joint portion was subjected to line analysis using EPMA, and it was confirmed from the analysis result that a joint layer containing 40% by mass or more of Ni was formed.
[0026]
[Table 4]

[0027]
[Table 5]

[0028]
According to Table 5 above, even within the bonding temperature according to the present invention, when the thickness of the bonding layer of the bonded body exceeds 2.0 mm, the bonded portion has low strength. Therefore, in the present invention, the thickness of the bonding layer is 2.0 mm or less. A more preferable thickness of the bonding layer is 0.010 mm to 0.200 mm, and a more preferable thickness of the bonding layer is 0.020 mm to 0.100 mm.
[0029]
A second embodiment of the present invention will be described. In this example, similarly to Example 1, an iron-based alloy block having the chemical composition shown in Table 4 above and an insert material equivalent to BNi-2 in Table 1 were used. As shown in FIG. The insert material 3 was heated and melted between the made block 1 and the block 2 to join the iron-based alloy blocks 1 and 2 together. In this Example 2, as shown in Table 6, as a joining condition between the blocks, the temperature at which the insert material is heated and melted and the holding time at the melting temperature are variously changed, and the cooling from the joining temperature to 500 ° C. is performed. The speed was adjusted to 10 to 50 ° C./min. And the following investigation was conducted using the manufactured joined_body | zygote. In the case of Example 2, the thickness of the bonding layer containing 40% by mass of Ni is all 0.05 mm.
[0030]
[Table 6]

[0031]
A tensile test piece was cut out from the joined body, and the joined body was subjected to a tensile test. Further, a micro test piece was collected from the remaining part of the joined body from which the tensile test piece was cut out, and the structure of the joined part was observed with a microscope and analyzed by EPMA. Furthermore, the hardness of the central part of the bonding layer was measured with a load of 0.49 N using a micro Vickers hardness meter. The tensile test piece has a parallel part with a diameter of 6 mm and a length of 32 mm, and is processed so that the joint surface is perpendicular to the load direction at the center of the parallel part.
[0032]
Table 6 shows the tensile test results of the tensile test pieces and the observation results of the structure of the joints. According to Table 6 above, in the case of the present example in which the heating temperature at the time of bonding is 1050 ° C. or higher, since there are only 2 B compounds of 1 μm or more / 50 μm or less in the bonding layer, the strength of the bonded body Is equal to or higher than the strength of the base metal.
In particular, when the joining temperature is 1100 ° C. or higher, the base material part is broken despite the tensile test of the joined body. However, when the bonding temperature is less than 1050 ° C., 3/50 μm or more of B compounds having a diameter of 1 μm or more remain in the bonding layer, so that the bonded body is broken at the bonded portion. The reason why the bonded body breaks at the bonded portion in this way is considered to be that even if the bonded portion has low strength or high strength, elongation cannot be obtained and it is brittle. Also, according to Table 6, it can be seen that the precipitation characteristics and strength characteristics of the B compound in the bonding layer are almost unaffected by the length of the holding time at the heating temperature and are determined by the heating temperature.
[0033]
A third embodiment of the present invention will be described. In this example, an iron-base alloy having the composition shown in Table 4 above is joined using four amorphous foils having a thickness of 20 μm, which is an insert material corresponding to BNi-2 in Table 1 above. As shown, after the block 1 having the cavity 7 and the mating block 2 are joined, the height change of the cavity portion is compared before and after joining. More specifically, bonding was performed at a heating temperature of 1190 ° C., and a load was applied so that the surface pressure was 1 MPa at the time of bonding. At this time, the holding time at the time of joining was variously changed, and the deformation amount before and after the joining with respect to the holding time was examined.
The amount of deformation before and after joining is calculated by assuming that the height of the cavity portion of the block 1 before joining is a0 and the height of the space portion after joining is a, [[a0 + insert material thickness (0.02 × 4 = 0.08 mm)]-a], measured with calipers, and used an average value measured five times in total.
[0034]
And after the test, the cross section of the joining layer was mirror-polished and analyzed by EPMA. As a result, the thickness of the joining layer containing 40% by mass or more of Ni after joining was in the range of 0.03 mm to 0.06 mm. Further, the holding time at the heating temperature at the time of bonding and the deformation amount before and after the bonding were as shown in Table 7 below.
[0035]
[Table 7]

[0036]
In Table 7 above, when the holding time for bonding is too short for 0.5 minutes and 0.75 minutes, the bonded part peels off during dimension measurement after bonding, and dimension measurement after bonding can be performed. There wasn't. It is assumed that the joint is peeled in this way because the reaction at the joint interface is insufficient and the interface strength is weak.
[0037]
Further, when the holding time was long 240 minutes, 300 minutes, and 360 minutes, the base material was deformed, and the deformation amount after joining was large. On the other hand, when the holding time is appropriate from 1 minute to 180 minutes, no peeling occurs at the interface and the deformation amount after joining is small, so that the joined body is produced with excellent dimensional accuracy by this method. be able to. Here, when the holding time is long, there is a disadvantage that the manufacturing cost of the bonded body becomes high, and conversely, when the holding time is short, due to the temperature difference in the bonding surface when producing a large bonded body, the bonded portion Is likely to have low strength, and the time for bonding is preferably 5 minutes to 60 minutes.
[0038]
Embodiment 4 of the present invention will be described. In this example, an iron-base alloy having the composition shown in Table 8 below was used, and an insert material corresponding to BNi-2 in Table 1 was used, and the joining conditions were determined by joining by heating and melting. In this case, as shown in Table 9 below, a joined body was manufactured by variously changing the temperature at which the insert material is heated and melted and the holding time at the temperature. And the micro test piece was extract | collected from the cutting remainder of the tensile test piece, the structure | tissue of the junction part was observed with the microscope, and it analyzed by EPMA. The cooling rate from the bonding temperature to 500 ° C. was adjusted to 10 to 50 ° C./min. The tensile test method is the same as in the case of Example 1. In addition, the thickness of the joining layer containing 40 mass% Ni is all 0.08 mm. Table 9 below shows the structure observation results of the tensile test piece and the joint.
[0039]
[Table 8]

[0040]
[Table 9]

[0041]
According to Table 9, when the heating temperature when the members are joined is 1040 ° C. or more, two or more B compounds having a diameter of 1 μm or more do not exist per 50 μm in the joining layer, and the strength of the joined portion is the mother. The strength is equal to or better than the material.
Further, it can be seen that the generation characteristics and strength characteristics of the B compound in the bonding layer of this bonded body are hardly affected by the length of the holding time at the heating temperature, and are determined by the heating temperature. On the other hand, when the heating temperature at the time of bonding is less than 1040 ° C., since 3 or more B compounds of 1 μm or more remain in 50 μm in the bonding layer, the bonding layer has high hardness. Therefore, although the strength is low, as in the case described above, the structure characteristics and strength characteristics of the bonding layer are not affected by the holding time at the heating temperature at the time of bonding, but are determined by the heating temperature.
[0042]
A fifth embodiment of the present invention will be described. In this example, an iron-base alloy having the composition shown in Table 8 above was used, and a method of joining by heating and melting through an insert material having the composition shown in Table 10 was examined. At that time, the joined body was manufactured at the joining temperature and joining time as shown in Table 11. After joining, after tempering at 700 ° C. for the tempering of the base material, the same tensile test piece as in Example 1 was cut out and subjected to a tensile test, and the joint section cut out from the remainder was embedded in the resin Then, mirror polishing was performed and EPMA analysis was performed.
[0043]
[Table 10]

[0044]
[Table 11]

[0045]
According to Table 11, when the bonding temperature between the members is 1200 ° C. or higher, two or more B compounds of 1 μm or more do not exist in 50 μm in the bonding layer, and high strength of the bonded body can be obtained. On the other hand, when the bonding temperature is less than 1190 ° C., since there are three or more B compounds in the bonding layer per 50 μm, the strength of the bonded body is low.
[0046]
A sixth embodiment of the present invention will be described. In this example, an iron-base alloy having the composition shown in Table 8 above was used, and a method of joining by heating and melting through an insert material having the composition shown in Table 10 was examined. At that time, bonding was performed at a bonding temperature and time as shown in Table 12, and further cooled at each cooling rate shown in Table 12. The cooling rate is adjusted by adjusting the pressure of the cooling gas during cooling or by cooling while heating with a heater. The cooling rate is not always constant between the bonding temperature and 500 ° C., but the average cooling rate obtained by dividing the temperature difference from the bonding temperature to 500 ° C. by the time required for cooling is used here. is there. After joining, tempering for tempering the base material was performed in the same manner as in Example 5. Thereafter, a tensile test piece was cut out from the joined body and subjected to a tensile test. The B compound in the bonding layer was analyzed. The results are shown in Table 12.
[0047]
[Table 12]

[0048]
As shown in Table 12, when the bonding temperature is 1170 ° C. or 1180 ° C., which is less than 40 ° C. than the liquidus temperature of the insert material, B compound is generated in the bonding layer regardless of the holding time. Therefore, the joined body has low strength. The present B compound is presumed to have crystallized while the insert material is melted. On the other hand, when the joining temperature is 1200 ° C, 1230 ° C, 1250 ° C, which is 40 ° C higher than the liquidus temperature of the insert material, the cooling rate from the joining temperature to 500 ° C is 1 ° C / min to 100 ° C / min. When the cooling rate from 500 ° C. to 150 ° C. is 2 ° C./min or more, the number of B compounds per 50 μm of the bonding layer is 2 or less and the strength of the bonded body is high. When the cooling rate from the bonding temperature to 500 ° C. was 100 ° C./min or more, cracks occurred in the bonded portion, and thus the tensile test piece could not be cut out. However, only 2 or less B compounds per 50 μm can be seen in the bonding layer cut out from the healthy part. Further, when the cooling rate to 500 ° C. is less than 1 ° C./min and the cooling rate from 500 ° C. to 150 ° C. is less than 2 ° C./min, the number of B compounds per 50 μm of the bonding layer is 2 or more, and the joined body The strength of is low. The B compound in the bonding layer is considered to have precipitated during cooling from the bonding temperature.
[0049]
【The invention's effect】
As described above, the joined body of the iron-based alloy members according to the present invention has a strength that is as high as that of the iron-based alloy member that is the base material of the joining layer. Can be applied with confidence.
[0050]
Further, according to the method for joining iron-base alloy members according to the present invention, the strength of the joining layer can be made as high as that of the iron-base alloy member that is the base material, and a joined body having high strength. Can be manufactured.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of counting the number of boron compounds in a bonding layer.
FIG. 2 is an explanatory diagram for defining the diameter of a boron compound, where a is a circular compound, b is an ellipse, c is a drop shape, and d is a square shape.
FIG. 3 is a developed perspective view of a joined body according to the present invention.
4A and 4B are explanatory views of another joined body according to the present invention, in which a is a developed perspective view and b is a perspective view.
[Explanation of symbols]
1, 2: Iron-based alloy member 3: Insert material 4: Bonding layer
5: Boron compound 6: Conjugate 7: Cavity

Claims (5)

It is a joined body formed by diffusion bonding of two or more iron-based alloy members through an insert material, and the insert material contains B : 1.0% by mass to 5.0% by mass And a nickel-based alloy consisting of the balance Ni and unavoidable impurities containing either or both of Cr: 5.0 mass% to 20 mass% and Si: 1.0 mass% to 10 mass%, A joining layer is formed between the iron-based alloy members, and the joining layer has a remaining nickel content of 40% by mass or more and a thickness of 2.0 mm or less , and the stacking direction of the insert material conjugate of ferrous alloy between the number of the measured diameter 1μm or more boron compounds is equal to or less than 2 on the average per 50μm in the central plane perpendicular to the. It is a joined body formed by diffusion bonding of two or more iron-based alloy members through an insert material, and the insert material contains B: 1.0% by mass to 5.0% by mass And Cr: 5.0% by mass to 20% by mass and Si: 1.0% by mass to 10% by mass, or both, Fe: 5% by mass or less, C: 1. 1% by mass or less, Co: 1% by mass or less, Mo: 4% by mass or less, Cu: 4% by mass or less, a nickel-based alloy comprising at least one of the balance Ni and inevitable impurities, the iron A joining layer is formed between the base alloy members, and the joining layer has a remaining nickel content of 40% by mass or more and a thickness of 2.0 mm or less, and with respect to the stacking direction of the insert material. Boron compound with a diameter of 1 μm or more measured on the vertical center plane Conjugate of ferrous alloy with each other, wherein the number is equal to or less than the average 2 per 50 [mu] m. The joined body of iron-based alloy members according to claim 1 or 2 , wherein the iron-based alloy member is a pipe for petroleum refining or chemical industry. B : 1.0% by mass to 5.0% by mass is contained between members made of an iron-based alloy, and Cr: 5.0% by mass to 20% by mass and Si: 1.0% by mass to 10%. Inserting an insert material made of a nickel-based alloy having a composition of the balance Ni and inevitable impurities containing either one or both of the mass%, and a temperature higher than the liquidus temperature of the insert material by 40 ° C or higher and 1300 ° C or lower After the insert material is melted by heating in the temperature range of 1 to 180 minutes, it is cooled to 500 ° C. at a cooling rate of 1 ° C./min to 100 ° C./min, and then at a cooling rate of 2 ° C./min or more by cooling to 0.99 ° C., the bonding layer is formed between the members to each other made iron-base alloy, the bonding layer, the nickel content is 40 mass% or more remaining, and a thickness of 2.0mm or less, And with respect to the stacking direction of the insert material Bonding method between the ferrous alloy, wherein the number of the measured diameter 1μm or more boron compounds is the average two or less per 50μm in the central plane of vertical Te. Between members made of an iron-based alloy, B: 1.0 mass% to 5.0 mass% is contained, Cr: 5.0 mass% to 20 mass%, and Si: 1.0 mass% to 10 mass% One or both of the mass% is contained, and Fe: 5 mass% or less, C: 1.1 mass% or less, Co: 1 mass% or less, Mo: 4 mass% or less, Cu: 4 mass% A temperature of 40 ° C. or more to a temperature of 1300 ° C. or less higher than the liquidus temperature of the insert material, which includes one or more of the following, interposing an insert material made of a nickel-based alloy having a balance Ni and inevitable impurity composition After the insert material was melted by heating for 1 minute to 180 minutes in the range, it was cooled to 500 ° C. at a cooling rate of 1 ° C./min to 100 ° C./min, and then 150 ° C. at a cooling rate of 2 ° C./min or more. By cooling to between iron-based alloy members A joining layer is formed, and the joining layer has a remaining nickel content of 40 mass% or more and a thickness of 2.0 mm or less, and a central plane perpendicular to the stacking direction of the insert material The number of boron compounds having a diameter of 1 μm or more measured in 1 is an average of 2 or less per 50 μm.

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