JP2740597B2 - Duplex stainless steel with excellent drillability - Google Patents
Duplex stainless steel with excellent drillabilityInfo
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- JP2740597B2 JP2740597B2 JP24468392A JP24468392A JP2740597B2 JP 2740597 B2 JP2740597 B2 JP 2740597B2 JP 24468392 A JP24468392 A JP 24468392A JP 24468392 A JP24468392 A JP 24468392A JP 2740597 B2 JP2740597 B2 JP 2740597B2
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、製紙機械用サクション
ロール用材料に要求される耐食性及び腐食疲労強度を備
えると共に、ドリル加工性にすぐれた二相ステンレス鋼
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplex stainless steel having excellent corrosion resistance and corrosion fatigue strength required for a material for a suction roll for a papermaking machine and excellent in drillability.
【０００２】[0002]
【従来技術】製紙機械におけるサクションロールは、中
空スリーブ構造であって、腐食雰囲気中で使用されるた
め、すぐれた耐食性と高い腐食疲労強度を具備する必要
がある。このため、ロール材料は、一般的にはフェライ
ト−オーステナイト二相組織のステンレス鋼が使用され
ている。2. Description of the Related Art A suction roll in a papermaking machine has a hollow sleeve structure and is used in a corrosive atmosphere. Therefore, the suction roll must have excellent corrosion resistance and high corrosion fatigue strength. For this reason, as a roll material, stainless steel having a ferrite-austenite dual phase structure is generally used.
【０００３】一方、サクションロールは、多湿紙の水分
を吸引するためのサクションホール(口径約３〜６mm)が
ロールの略全領域にわたって、数mmのピッチで開設さ
れ、その個数は数万個にも及ぶ。このサクションホール
の孔明けは、ドリル加工によって行なわれるため、この
二相ステンレス鋼はドリル加工性にすぐれるものでなけ
ればならない。また、ドリル加工性が悪いと、孔形状の
不揃いが大きくなったり、孔部の面粗度が粗くなる不都
合もあり、ロール寿命を短くする結果となる。On the other hand, suction rolls (with a diameter of about 3 to 6 mm) for sucking moisture from humid paper are opened at a pitch of several mm over substantially the entire area of the roll, and the number of the suction rolls is tens of thousands. Extend. Since the suction holes are formed by drilling, the duplex stainless steel must have excellent drillability. In addition, when the drill workability is poor, the irregularity of the hole shape becomes large, and the surface roughness of the hole becomes inconvenient, resulting in shortening the roll life.
【０００４】これまでのサクションロール用二相ステン
レス鋼は、耐食性及び腐食疲労強度を向上させるため
に、Ｃの含有量を少なくし、相当量のＭｏ、Ｃｕ、Ｎを
含有させる傾向にあった。しかし、材料成分のこのよう
な傾向は、ドリル加工性の低下を招き、孔明作業時にド
リルの折損事故が頻繁に発生する結果となり、ドリル加
工のために多大な時間とコストを要しているのが実情で
ある。[0004] Conventional duplex stainless steels for suction rolls have tended to reduce the content of C and contain considerable amounts of Mo, Cu, and N in order to improve corrosion resistance and corrosion fatigue strength. However, such a tendency of the material composition results in a decrease in drill workability, resulting in frequent drill breakage during drilling work, which requires a great deal of time and cost for drilling. Is the actual situation.
【０００５】[0005]
【発明が解決しようとする課題】本発明の目的は、ドリ
ル加工性を改善すると共に、耐食性及び腐食疲労強度に
ついては従来鋼の水準を確保した二相ステンレス鋼を提
供することにある。SUMMARY OF THE INVENTION It is an object of the present invention to provide a duplex stainless steel having improved drill workability and having the same level of corrosion resistance and corrosion fatigue strength as conventional steels.
【０００６】[0006]
【課題を解決するための手段】上記目的を達成するた
め、本発明の二相ステンレス鋼は、重量％にて、Ｃ：
０.０８％以下、Ｓｉ：１.５％以下、Ｍｎ：１.５％以
下、Ｎｉ：４〜６％、Ｃｒ：２０〜２４％、Ｍｏ：１.
５％以下、Ｎ：０.１５％以下、残部実質的にＦｅから
なり、かつ前記Ｃｒ、Ｍｏ及びＮは、Ｃｒ＋３.３Ｍｏ
＋１６Ｎ≦２８％の範囲にあり、金属組織におけるフェ
ライト相の面積率は４０〜７０％である。なお、前記二
相ステンレス鋼は、必要に応じて１.０％以下のＣｕを
含めることができる。In order to achieve the above object, the duplex stainless steel of the present invention contains C:
0.08% or less, Si: 1.5% or less, Mn: 1.5% or less, Ni: 4 to 6%, Cr: 20 to 24%, Mo: 1.
5% or less, N: 0.15% or less, the balance being substantially composed of Fe, and the Cr, Mo and N are Cr + 3.3Mo.
+ 16N ≦ 28%, and the area ratio of the ferrite phase in the metal structure is 40 to 70%. The duplex stainless steel can contain 1.0% or less of Cu as needed.
【０００７】[0007]
【作用】Ｃｕは、含有しないか又はドリル加工性への悪
影響を及ぼさない程度の含有量にとどめたこと、並びに
フェライト量及びＣｒ、Ｍｏ及びＮの含有量の適正化を
図って加工硬化を起こりにくくしたことにより、すぐれ
たドリル加工性を発揮する。溶体化処理の加熱後、適量
の水又はミストを供給しながら空冷(制御空冷)すること
により、残留応力は低減される。従って、水冷のときと
は異なり、残留応力低減化のための焼戻し処理は結果的
に不要となるから、焼戻し段階で炭化物等が析出するこ
とはなく、所定水準の耐食性と腐食疲労強度を確保する
ことができる。[Working] Cu is not contained or has a content that does not adversely affect drilling workability, and work hardening occurs by optimizing the amount of ferrite and the contents of Cr, Mo and N. Due to the difficulty, excellent drill workability is exhibited. After heating in the solution treatment, the residual stress is reduced by air cooling (control air cooling) while supplying an appropriate amount of water or mist. Therefore, unlike the case of water cooling, the tempering treatment for reducing residual stress is not required as a result, so that carbides and the like do not precipitate in the tempering stage, and a predetermined level of corrosion resistance and corrosion fatigue strength are secured. be able to.
【０００８】[0008]
Ｃ：０.０８％以下 Ｃはオーステナイト生成元素であり、強度の向上及びド
リル加工性の向上に寄与する。微量でもこの効果を得る
ことはできるが、約０.０３％以上含有させることが望
ましい。しかし、あまりに多く含有すると、クロム炭化
物が析出しやすくなり、耐食性が損なわれる。このた
め、上限は０.０８％に規定する。C: 0.08% or less C is an austenite-forming element and contributes to improvement in strength and drill workability. Although this effect can be obtained even with a small amount, it is desirable to contain about 0.03% or more. However, if the content is too large, chromium carbides are liable to precipitate and the corrosion resistance is impaired. For this reason, the upper limit is defined as 0.08%.
【０００９】Ｓｉ：１.５％以下 Ｓｉは溶鋼の脱酸及び成形性確保のために含有させる。
しかし、あまりに多く含有すると靱性が損なわれるた
め、１.５％を上限とする。Si: 1.5% or less Si is contained for the purpose of deoxidizing molten steel and ensuring formability.
However, if the content is too large, the toughness is impaired, so the upper limit is 1.5%.
【００１０】Ｍｎ：１.５％以下 Ｍｎは通常の脱酸及び脱硫過程で含まれるもので、１.
５％以下の含有であれば特に問題ない。Mn: 1.5% or less Mn is contained in ordinary deoxidation and desulfurization processes, and
There is no particular problem if the content is 5% or less.
【００１１】Ｎｉ：４〜６％ Ｎｉはオーステナイト相を安定化する元素であり、靱性
の向上に寄与する。このため、少なくとも４％の含有を
要する。一方、あまりに多く含有するとオーステナイト
相が過剰になって二相の量的バランスが損なわれ、加工
硬化が起こりやすく、ドリル加工性が悪くなる。このた
め、上限を６％と規定する。Ni: 4 to 6% Ni is an element for stabilizing the austenite phase and contributes to improvement in toughness. For this reason, the content of at least 4% is required. On the other hand, if the content is too large, the austenite phase becomes excessive, and the quantitative balance of the two phases is impaired, work hardening easily occurs, and drill workability deteriorates. For this reason, the upper limit is defined as 6%.
【００１２】Ｃｒ：２０〜２４％ Ｃｒは耐食性の向上に寄与し、またフェライト相の形成
により強度を高める。このため、少なくとも２０％以上
含有させる必要がある。一方、あまりに多く含有すると
靱性の低下を招き、また成形時に脆弱なシグマ相を形成
する。このため、上限を２４％と規定する。Cr: 20 to 24% Cr contributes to the improvement of corrosion resistance and increases the strength by forming a ferrite phase. For this reason, it is necessary to contain at least 20% or more. On the other hand, if the content is too large, the toughness is reduced, and a brittle sigma phase is formed during molding. For this reason, the upper limit is defined as 24%.
【００１３】Ｍｏ：１.５％以下 Ｍｏは耐食性の向上に寄与するが、一方ではドリル加工
性に悪影響を及ぼす。このため、本発明の二相ステンレ
ス鋼にあっては、上限を１.５％に規定する。Mo: 1.5% or less Mo contributes to the improvement of corrosion resistance, but on the other hand, adversely affects drill workability. For this reason, in the duplex stainless steel of the present invention, the upper limit is set to 1.5%.
【００１４】Ｎ：０.１５％以下 Ｎはオーステナイト生成元素であり、靱性及び耐食性の
改善に寄与する。しかし、オーステナイト相の強化によ
って加工硬化を起こしやすくなる。含有量が０.１５％
を超えるとその傾向が顕著となるため、上限は０.１５
％と規定する。N: 0.15% or less N is an austenite forming element and contributes to improvement in toughness and corrosion resistance. However, work hardening is likely to occur due to the strengthening of the austenite phase. 0.15% content
Exceeds 0.15, the upper limit is 0.15.
%.
【００１５】Ｃｒ＋３.３Ｍｏ＋１６Ｎ≦２８％ Ｃｒ＋３.３Ｍｏ＋１６Ｎなる数式は、孔食指数として
も利用されるが、本発明者は、この数値が大きくなるに
つれて、母材の硬度が上昇し加工硬化を起こしやすくな
ることを見出した。特に２８％を超えるとその傾向が著
しくなるため、最大値を２８％に規定する。The formula of Cr + 3.3Mo + 16N ≦ 28% Cr + 3.3Mo + 16N is also used as a pitting corrosion index. However, as the numerical value increases, the hardness of the base material increases and work hardening easily occurs. I found out. In particular, if it exceeds 28%, the tendency becomes remarkable, so the maximum value is defined as 28%.
【００１６】Ｃｕ：１.０％以下 Ｃｕはドリル加工性を低下させるが、全面腐食に対する
抵抗性を高める効果を有する。従って、耐食性がより重
要視されるときにのみ含有させる。しかし、その場合で
も、含有量が１.０％を超えるとドリル加工性の低下が
顕著になるので、上限は１.０％と規定する。Cu: 1.0% or less Cu reduces the drill workability, but has the effect of increasing the resistance to general corrosion. Therefore, it is included only when the corrosion resistance is more important. However, even in this case, if the content exceeds 1.0%, the drillability is significantly reduced, so the upper limit is specified as 1.0%.
【００１７】本発明の二相ステンレス鋼は、上記各成分
を含有し、不可避的に混入するＰ、Ｓ等の不純物元素及
びＦｅからなる。The duplex stainless steel of the present invention contains each of the above-mentioned components, and is composed of impurity elements such as P and S, which are inevitably mixed, and Fe.
【００１８】なお、本発明の二相ステンレス鋼は、金属
組織におけるフェライト相の面積率は４０〜７０％であ
る。これは、健全なフェライト−オーステナイト相のバ
ランスを確保するためである。即ち、オーステナイト相
の占める割合が多くなって６０％を超える(フェライト
相は４０％よりも少なくなる)と加工硬化を起こしやす
くなり、オーステナイト相が３０％より少なくなる(フ
ェライト相は７０％よりも多くなる)と所望の鋳造性を
確保することができなくなるためである。In the duplex stainless steel of the present invention, the area ratio of the ferrite phase in the metal structure is 40 to 70%. This is to ensure a sound ferrite-austenite phase balance. That is, when the ratio of the austenite phase increases and exceeds 60% (the ferrite phase is less than 40%), work hardening is likely to occur, and the austenite phase is less than 30% (the ferrite phase is more than 70%). This is because it becomes impossible to secure the desired castability when the amount increases.
【００１９】[0019]
【実施例】供試材として、表１に示す成分組成及びフェ
ライト量を有する遠心鋳造管を調製した。供試材No.１
〜５は本発明の実施例、供試材No.６及び７は比較例で
ある。比較例No.６は、Ｃｒ、Ｍｏ及びＮ、並びにＣｒ
＋３.３Ｍｏ＋１６Ｎの規定が本発明の範囲から逸脱し
ている。比較例No.７はＣｒ、Ｍｏ及びＮは個別的には
本発明の範囲内に含まれているが、Ｃｒ＋３.３Ｍｏ＋
１６Ｎの規定については逸脱しており、また、Ｎｉの含
有量が多いため、オーステナイト量が多くなってフェラ
イト量が本発明の範囲よりも少ない。EXAMPLES As test materials, centrifugally cast tubes having the component compositions and ferrite contents shown in Table 1 were prepared. Sample No.1
5 are examples of the present invention, and test materials Nos. 6 and 7 are comparative examples. Comparative Example No. 6 was composed of Cr, Mo and N, and Cr
The definition of + 3.3Mo + 16N deviates from the scope of the present invention. In Comparative Example No. 7, Cr, Mo and N are individually included in the scope of the present invention, but Cr + 3.3Mo +
Since the content of 16N is deviated and the content of Ni is large, the amount of austenite is increased and the amount of ferrite is smaller than the range of the present invention.
【００２０】各供試材について、機械的性質試験、耐食
試験、腐食疲労試験、残留応力試験及びドリル加工性試
験を行なった。各種試験結果を表２に示す。Each test material was subjected to a mechanical property test, a corrosion resistance test, a corrosion fatigue test, a residual stress test, and a drill workability test. Table 2 shows the results of various tests.
【００２１】[0021]
【表１】 [Table 1]
【００２２】[0022]
【表２】 [Table 2]
【００２３】各種試験を行なう前に、供試材は、所定の
溶体化温度に加熱した後、管体内面に水又はミストを吹
き付けながら空気を強制的に送り込み、冷却速度を制御
しながら空冷した。なお、供試材No.１ａは供試材No.１
と同成分の遠心鋳造管であって、溶体化温度に加熱した
後、別に水冷・焼戻しを施したものである。Before conducting various tests, the test material was heated to a predetermined solution temperature, then forcibly fed air while spraying water or mist on the inner surface of the tube, and air-cooled while controlling the cooling rate. . In addition, the test material No. 1a is the test material No. 1
This is a centrifugally cast tube having the same composition as that described above, which is heated to a solution heat temperature and then water-cooled and tempered separately.
【００２４】機械的性質試験は、ＪＩＳの規定に準拠し
て行ない、0.2％耐力、引張強さ、伸び、絞り及び衝撃
値を調べた。なお、耐食性試験は、各供試材を５％沸騰
硫酸中に６時間浸漬した後の腐食減量を求めた。The mechanical property test was carried out in accordance with JIS regulations, and the 0.2% proof stress, tensile strength, elongation, drawing, and impact value were examined. In addition, in the corrosion resistance test, the corrosion loss after immersing each test material in 5% boiling sulfuric acid for 6 hours was determined.
【００２５】腐食疲労強度試験は、TAPPI Type 1 に準
拠して行ない、腐食性液(Cl-100ppm,SO4 2-1000ppm, pH
3.5)中にて１０8サイクルでの強度を求めた。The corrosion fatigue strength test, carried out in conformity with TAPPI Type 1, corrosive liquid (Cl - 100ppm, SO 4 2- 1000ppm, pH
3.5) was determined by the strength of 10 8 cycles at in.
【００２６】残留応力試験は、リングカット法によって
応力値を求めた。In the residual stress test, a stress value was obtained by a ring cut method.
【００２７】ドリル加工性試験は、ツイストドリルによ
る孔明け加工を行ない、孔明け時に供試片に作用するト
ルクを測定した。このトルクが小さいほど、ドリル加工
性にすぐれている。In the drill workability test, drilling was performed with a twist drill, and the torque acting on the test piece at the time of drilling was measured. The smaller the torque, the better the drill workability.
【００２８】表１及び表２を参照すると、供試材No.６
は、耐食性及び腐食疲労強度にはすぐれるが、伸びが小
さく、ドリル加工時のトルクが大きい。これは、Ｃｒ、
Ｍｏ、Ｎの含有量が多いため、Ｃｒ、Ｍｏ、Ｎの量的バ
ランスが崩れて加工硬化を起こしているものと考えられ
る。Referring to Tables 1 and 2, the test material No. 6
Has excellent corrosion resistance and corrosion fatigue strength, but has low elongation and large torque during drilling. This is Cr,
It is considered that since the contents of Mo and N are large, the quantitative balance of Cr, Mo and N is broken and work hardening is caused.
【００２９】供試材No.７は、伸びが小さく、ドリル加
工時のトルクも大きい。これは、フェライト量が34.9％
と少なく、フェライト−オーステナイト相の量的バラン
スが崩れているためと考えられる。Sample No. 7 has a small elongation and a large torque during drilling. This is because ferrite content is 34.9%
This is probably because the quantitative balance of the ferrite-austenite phase was lost.
【００３０】なお、水冷・焼戻しを施した供試No.１ａ
は、制御空冷した供試No.１よりも耐食性に著しく劣っ
ている。これは、水冷後に焼戻しを施したことにより、
一旦溶け込んだ炭化物が析出したためである。溶体化処
理は、加熱後、水冷を施すのが一般的であるが、サクシ
ョンロールのように質量効果の大きな管体の場合、水冷
すると非常に大きな残留応力が発生する。残留応力が大
きいと、ドリル孔明時に開放された際、孔の周囲に変形
を伴ない、ドリルのかみ込みを生じてドリルの破損につ
ながることがあり、好ましくない。このため、水冷後、
焼戻しを施すことによって残留応力を緩和させているが
(供試No.１ａの残留応力値25.6MPaは、既に緩和された
値である)、供試No.１ａはＣの含有量が通常の二相ステ
ンレス鋼よりも多いため、炭化物が析出してしまうので
ある。Test No. 1a after water cooling and tempering
Is significantly inferior in corrosion resistance to test air-cooled test No. 1. This is due to tempering after water cooling,
This is because the carbide once melted was precipitated. In the solution treatment, water cooling is generally performed after heating. However, in the case of a tube having a large mass effect such as a suction roll, a very large residual stress is generated by water cooling. If the residual stress is large, when the drill is opened at the time of drilling, the periphery of the hole is deformed, and the bite of the drill may be caused, which may lead to breakage of the drill. For this reason, after water cooling,
Tempering reduces the residual stress.
(The residual stress value of 25.6 MPa in Test No. 1a was already relaxed.) In Test No. 1a, since the content of C was larger than that of ordinary duplex stainless steel, carbide was precipitated. It will be lost.
【００３１】Ｃを多く含むとドリル加工性が改善される
ことはある程度予想されていたが、溶体化処理後の水冷
・焼戻しによって耐食性が損なわれるため、これまでは
Ｃの増量はできないものと考えられていた。しかし、上
記の如く、制御空冷することによって、残留応力を小さ
くできるから、炭化物の析出を伴なう焼戻し処理は不要
となり、Ｃの含有を多くしても所望の耐食性を確保でき
ることがわかった。It has been expected that the drilling property will be improved to some extent if C is contained in a large amount. However, since the corrosion resistance is impaired by water cooling and tempering after the solution treatment, it is considered that C cannot be increased until now. Had been. However, as described above, since the residual stress can be reduced by controlled air cooling, tempering treatment involving precipitation of carbides is not required, and it has been found that desired corrosion resistance can be ensured even when the content of C is increased.
【００３２】表１及び表２から明らかなように、本発明
の供試材No.１〜No.５は、所望の機械的性質、耐食性及
び腐食疲労強度を確保し、残留応力値も低い。また、ド
リル加工時のトルクが小さく、ドリル加工性にすぐれて
いる。As is clear from Tables 1 and 2, the test materials No. 1 to No. 5 of the present invention ensure desired mechanical properties, corrosion resistance and corrosion fatigue strength, and have low residual stress values. Further, the torque during drilling is small, and the drilling is excellent.
【００３３】[0033]
【発明の効果】本発明の二相ステンレス鋼は、所定の耐
食性及び腐食疲労強度を確保しつつすぐれたドリル加工
性を具備するから、製紙機械用サクションロール用の材
料として好適である。The duplex stainless steel of the present invention is suitable as a material for a suction roll for a papermaking machine because it has excellent drilling workability while securing a predetermined corrosion resistance and corrosion fatigue strength.
フロントページの続き (72)発明者 吉竹 晃 大阪府枚方市中宮大池１丁目１番１号 株式会社クボタ枚方製造所内 (56)参考文献 特開 平１−198448（ＪＰ，Ａ) 特開 平４−198456（ＪＰ，Ａ) 特開 昭54−19413（ＪＰ，Ａ)Continuation of the front page (72) Inventor Akira Yoshitake 1-1-1 Nakamiya Oike, Hirakata City, Osaka Prefecture Kubota Hirakata Factory Co., Ltd. (56) References JP-A-1-198448 (JP, A) JP-A-4- 198456 (JP, A) JP-A-54-19413 (JP, A)
Claims (2)
ｉ：１.５％以下、Ｍｎ：１.５％以下、Ｎｉ：４〜６
％、Ｃｒ：２０〜２４％、Ｍｏ：１.５％以下、Ｎ：０.
１５％以下、残部実質的にＦｅからなり、かつ前記Ｃ
ｒ、Ｍｏ及びＮは、Ｃｒ＋３.３Ｍｏ＋１６Ｎ≦２８％
の範囲にあり、金属組織におけるフェライト相の面積率
は４０〜７０％である、ドリル加工性にすぐれる二相ス
テンレス鋼。(1) C: 0.08% or less in weight%
i: 1.5% or less, Mn: 1.5% or less, Ni: 4 to 6
%, Cr: 20 to 24%, Mo: 1.5% or less, N: 0.2%
15% or less, the balance being substantially composed of Fe;
r, Mo and N are Cr + 3.3Mo + 16N ≦ 28%
And the area ratio of the ferrite phase in the metal structure is 40 to 70%.
項１に記載の二相ステンレス鋼。2. The duplex stainless steel according to claim 1, containing Cu: 1.0% or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24468392A JP2740597B2 (en) | 1992-09-14 | 1992-09-14 | Duplex stainless steel with excellent drillability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24468392A JP2740597B2 (en) | 1992-09-14 | 1992-09-14 | Duplex stainless steel with excellent drillability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0693380A JPH0693380A (en) | 1994-04-05 |
| JP2740597B2 true JP2740597B2 (en) | 1998-04-15 |
Family
ID=17122396
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24468392A Expired - Lifetime JP2740597B2 (en) | 1992-09-14 | 1992-09-14 | Duplex stainless steel with excellent drillability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2740597B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3370441B2 (en) * | 1994-07-25 | 2003-01-27 | 日本冶金工業株式会社 | Duplex stainless steel sheet with excellent elongation characteristics and method for producing the same |
-
1992
- 1992-09-14 JP JP24468392A patent/JP2740597B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0693380A (en) | 1994-04-05 |
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