JP2902304B2 - Method of manufacturing hot-rolled steel sheet for high toughness square steel pipe excellent in Zn plating crack resistance and high toughness square steel pipe - Google Patents
Method of manufacturing hot-rolled steel sheet for high toughness square steel pipe excellent in Zn plating crack resistance and high toughness square steel pipeInfo
- Publication number
- JP2902304B2 JP2902304B2 JP16298294A JP16298294A JP2902304B2 JP 2902304 B2 JP2902304 B2 JP 2902304B2 JP 16298294 A JP16298294 A JP 16298294A JP 16298294 A JP16298294 A JP 16298294A JP 2902304 B2 JP2902304 B2 JP 2902304B2
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- weight
- steel pipe
- square steel
- less
- high toughness
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Bending Of Plates, Rods, And Pipes (AREA)
- Heat Treatment Of Steel (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、耐Ｚｎめっき割れ性に
優れた高靱性角鋼管用熱延鋼板の製造方法及びその鋼板
を用いた高靱性角鋼管に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hot-rolled steel sheet for a high-toughness square steel pipe having excellent resistance to cracking of Zn plating, and a high-toughness square steel pipe using the steel sheet.
【０００２】[0002]
【従来の技術】角鋼管は、構造用鋼材として広く使用さ
れている。この角鋼管では、美観或いは防錆が必要な場
合に溶融Ｚｎめっきが施されることがあるが、Ｚｎめっ
き槽に浸漬される際、管コーナー部の内面に割れを生ず
ることがあり、問題となっている。2. Description of the Related Art Square steel pipes are widely used as structural steel materials. In this square steel pipe, hot-dip Zn plating may be applied when aesthetics or rust prevention is required, but when it is immersed in a Zn plating tank, cracks may occur on the inner surface of the pipe corner part, which is a problem. Has become.
【０００３】Ｚｎめっき割れが問題となる角鋼管は、一
般的には、熱延鋼板をまずロール成形により円形に成形
した電縫鋼管とし、この電縫鋼管を引き続き角形にロー
ル成形することにより製造される。その結果、管コーナ
ー部の内面の周方向に残留引張応力が生ずる。そして、
管コーナー部の残留引張応力と、Ｚｎめっき時に侵入し
たＺｎによる粒界の液体金属脆化により、上述の割れを
発生させるのである。[0003] Square steel pipes in which Zn plating cracks are a problem are generally manufactured by forming a rolled hot rolled steel sheet into a rolled ERW steel pipe, and then forming the ERW pipe into a square roll. Is done. As a result, residual tensile stress is generated in the circumferential direction of the inner surface of the pipe corner. And
The above-mentioned cracks are generated due to the residual tensile stress at the corners of the tube and the liquid metal embrittlement at the grain boundaries due to Zn invading during Zn plating.
【０００４】類似の現象として、溶接構造物用鋼材を溶
接にて組み立てたあと、溶融亜鉛めっきする際に生じ
る、溶接熱影響部（ＨＡＺ）での割れが挙げられる。こ
の割れも同様に、応力と、粒界への亜鉛の侵入による液
体金属脆化との作用によって発生している。しかし、こ
の割れは、作用する応力が溶接による残留応力であり、
造管に伴って生じる残留応力を起因とする角鋼管の割れ
とは異なっている。[0004] A similar phenomenon is a crack in a weld heat affected zone (HAZ), which occurs when hot-dip galvanizing is performed after a steel material for a welded structure is assembled by welding. This crack is also generated by the action of stress and liquid metal embrittlement due to the penetration of zinc into grain boundaries. However, in this crack, the acting stress is the residual stress due to welding,
This is different from the cracking of the square steel pipe caused by the residual stress generated during pipe making.
【０００５】溶接構造物用鋼材のＨＡＺに発生するめっ
き割れには数多くの対策が講じられているが、角形鋼管
の割れに対する対策はまだ数少ない。現在とられている
対策として、熱処理によりコーナー部の残留応力を除去
する方法がある。また、特開昭６４−５６８５３号公報
に記載の如く、鋼材のＣ、Ｓｉ、Ｍｎ量を制限すること
により亜鉛めっき割れを防止できるとされている。[0005] Many countermeasures have been taken against plating cracks occurring in the HAZ of steel materials for welded structures, but only a few countermeasures have been taken against cracks in rectangular steel pipes. As a countermeasure currently taken, there is a method of removing residual stress at a corner portion by heat treatment. Further, as described in JP-A-64-56853, it is said that zinc plating cracks can be prevented by limiting the amounts of C, Si, and Mn in a steel material.
【０００６】[0006]
【発明が解決しようとする課題】然しながら、熱処理に
より管コーナー内面の残留引張応力を除去する方法は高
コストとなる。However, the method of removing the residual tensile stress on the inner surface of the pipe corner by heat treatment is expensive.
【０００７】尚、角形ロール成形時に管コーナー内面に
生ずる残留引張応力起因のＺｎめっき割れを防止する方
法として、上述の特開昭64-56853号公報に記載の方法を
転用したとしても、割れが発生することがあり、また、
鋼材のＣ量を0.13重量％以上に制限しているため、特に
管コーナー部で十分な靱性を確保できない。[0007] As a method of preventing Zn plating cracks due to residual tensile stress generated on the inner surface of a pipe corner when forming a square roll, even if the method described in Japanese Patent Application Laid-Open No. 64-56853 is diverted, the cracks remain. May occur,
Since the C content of the steel material is limited to 0.13% by weight or more, sufficient toughness cannot be ensured especially at the pipe corner.
【０００８】本発明は、熱延鋼板を角形ロール成形し、
更に、溶融Ｚｎめっきを施して製造される角鋼管におい
て、低コストで、耐Ｚｎめっき割れ性に優れ、強度、靱
性も良好な角鋼管を製造可能とすることを目的とする。According to the present invention, a hot rolled steel sheet is formed into a square roll,
It is another object of the present invention to make it possible to manufacture a square steel pipe manufactured by applying hot-dip Zn plating at low cost, having excellent resistance to cracking of Zn plating, and having good strength and toughness.
【０００９】[0009]
【課題を解決するための手段】請求項１に記載の本発明
に係る耐Ｚｎめっき割れ性に優れた高靱性角鋼管用熱延
鋼板の製造方法は、Ｃ：0.02〜0.12重量％、Ｓｉ：0.5
重量％以下、Ｍｎ：0.2 〜2.0 重量％、残部Ｆｅ及び不
可避不純物からなる鋼を、1050℃以下での圧下率を60％
以下とする熱間圧延条件で製造することを特徴とするも
のである。According to the first aspect of the present invention, there is provided a method for producing a hot-rolled steel sheet for a high toughness square steel pipe excellent in Zn plating crack resistance according to the present invention, wherein C: 0.02 to 0.12% by weight, Si: 0.5
% By weight, Mn: 0.2 to 2.0% by weight, balance of Fe and inevitable impurities is reduced by 60% at 1050 ° C or less.
It is characterized by being manufactured under the following hot rolling conditions.
【００１０】請求項２に記載の本発明は、請求項１に記
載の本発明において更に、前記鋼が、Ｎｂ：0.08重量％
以下、Ｖ：0.08重量％以下、Ｔｉ：0.05重量％以下を１
種又は２種以上含むことを特徴としたものである。According to a second aspect of the present invention, the steel according to the first aspect further comprises Nb: 0.08% by weight.
Below, V: 0.08% by weight or less, Ti: 0.05% by weight or less
It is characterized by containing two or more species.
【００１１】請求項３に記載の本発明は、請求項１又は
２に記載の方法により製造した熱延鋼板を角形ロール成
形してなる耐Ｚｎめっき割れ性に優れた高靱性角鋼管で
ある。According to a third aspect of the present invention, there is provided a high-toughness square steel pipe which is formed by subjecting a hot-rolled steel sheet produced by the method according to the first or second aspect to a square roll forming and has excellent Zn plating cracking resistance.
【００１２】[0012]
【作用】本発明者は、耐Ｚｎめっき割れ性に及ぼす熱延
鋼板の組成と圧延条件の影響を検討し、以下の知見を得
た。The present inventors have studied the effects of the composition of hot-rolled steel sheet and rolling conditions on the resistance to cracking of Zn plating, and have obtained the following findings.
【００１３】（組成） Ｃ：0.02〜0.12重量％ Ｃは、最も簡便に鋼の強度を上昇させるのに役立つ成分
であり、0.02重量％未満ではその効果が期待できない。
一方、0.12重量％を超えると靱性が低下することから、
Ｃは0.02重量％以上、0.12重量％以下とする。(Composition) C: 0.02 to 0.12% by weight C is a component which is most useful for increasing the strength of steel, and its effect cannot be expected if it is less than 0.02% by weight.
On the other hand, if the content exceeds 0.12% by weight, the toughness decreases.
C is 0.02% by weight or more and 0.12% by weight or less.
【００１４】即ち、Ｃを0.015 、0.04、0.07、0.10、0.
13重量％のそれぞれに変化させ、Ｓｉ：0.20重量％、Ｍ
ｎ：1.0 重量％、Ｐ：0.013 重量％、Ｓ：0.005 重量％
である熱延鋼板（1050℃以下での圧下率：52％）を角形
成形して角形電縫鋼管を製造し、辺部の引張強さＴＳと
Ｃ量の関係（図１）、管コーナー部の 0℃でのシャルピ
ー吸収エネルギーｖＥ0 とＣ量の関係（図２）、を調査
した。図１、図２より、Ｃ：0.02〜0.12重量％とするこ
とにより、角鋼管の強度と、管コーナー部の靱性をとも
に確保できることを認めた。That is, C is 0.015, 0.04, 0.07, 0.10, 0.
13% by weight, Si: 0.20% by weight, M
n: 1.0% by weight, P: 0.013% by weight, S: 0.005% by weight
A square ERW pipe is manufactured by forming a hot-rolled steel sheet (rolling reduction at 1050 ° C or less: 52%) into a square ERW pipe, the relationship between the tensile strength TS at the side and the C content (Fig. 1), and the pipe corner. The relationship between the Charpy absorbed energy vE 0 at 0 ° C. and the C amount (FIG. 2) was investigated. From FIG. 1 and FIG. 2, it was confirmed that by setting C: 0.02 to 0.12% by weight, both the strength of the square steel pipe and the toughness of the pipe corner can be ensured.
【００１５】Ｓｉ：0.5 重量％以下 Ｓｉは、脱酸作用の利用と強度への寄与を目的として添
加されるが、0.5 重量％を超えて添加されると靱性に悪
影響を及ぼすことから、0.5 重量％以下とする。Si: 0.5 wt% or less Si is added for the purpose of utilizing the deoxidizing action and contributing to the strength. However, if added in excess of 0.5 wt%, the toughness is adversely affected. % Or less.
【００１６】Ｍｎ：0.2 〜2.0 重量％ Ｍｎは、強度確保のため添加され、その効果を得るには
0.2 重量％以上が必要となる。一方、2.0 重量％を超え
ると溶接性や靱性に悪影響を及ぼすことから、Ｍｎは0.
2 〜2.0 重量％とする。Mn: 0.2-2.0% by weight Mn is added for securing the strength.
0.2% by weight or more is required. On the other hand, if the content exceeds 2.0% by weight, the weldability and toughness are adversely affected.
2 to 2.0% by weight.
【００１７】Ｎｂ：0.08重量％以下、Ｖ：0.08重量％以
下、Ｔｉ：0.05重量％以下 Ｎｂ、Ｖ、Ｔｉは、強度を上昇させると共に、結晶粒を
細かくすることで靱性を上昇させる効果があるが、それ
ぞれ0.08重量％、0.08重量％、0.05重量％を超えて含有
すると、析出物が粗大化し、むしろ靱性が低下すること
から、それぞれ0.08重量％以下、0.08重量％以下、0.05
重量％以下とする。Nb: 0.08% by weight or less, V: 0.08% by weight or less, Ti: 0.05% by weight or less Nb, V and Ti have the effect of increasing the strength and increasing the toughness by making the crystal grains fine. However, if the content exceeds 0.08% by weight, 0.08% by weight, and 0.05% by weight, respectively, the precipitates are coarsened, and the toughness is rather reduced.
% By weight or less.
【００１８】（圧延条件）熱間圧延における1050℃以下
での圧下率を60％以下とすることにより、鋼板への転位
の導入が抑制され、その結果粒界へのＺｎの侵入を低減
化できる。これにより、角形ロール成形させた管コーナ
ー部に残留引張応力が作用していても、管コーナー部の
内面へのＺｎの侵入による粒界脆化を防止できる。その
結果として、角形ロール成形後の熱処理による残留応力
除去を施すことなく、低コストにて、Ｚｎめっき割れ性
を改善できる。(Rolling conditions) By setting the rolling reduction at 1050 ° C. or less in hot rolling to 60% or less, introduction of dislocations into the steel sheet is suppressed, and as a result, penetration of Zn into grain boundaries can be reduced. . Thereby, even if residual tensile stress acts on the tube corner formed by the square roll, grain boundary embrittlement due to penetration of Zn into the inner surface of the tube corner can be prevented. As a result, the Zn plating cracking property can be improved at low cost without removing residual stress by heat treatment after the rectangular roll forming.
【００１９】ここで、圧下率とは、圧延前の板厚に対す
る圧延前後の板厚の差の比を100 倍した値をいう。Here, the rolling reduction refers to a value obtained by multiplying the ratio of the difference between the thickness before and after rolling to the thickness before and after rolling by 100 times.
【００２０】即ち、Ｃ：0.07重量％、Ｓｉ：0.05重量
％、Ｍｎ：0.40重量％、Ｐ：0.013 重量％、Ｓ：0.005
重量％の鋼材について、1050℃以下での圧下率を50、5
3、58、60、65、75％のそれぞれに変化させて製造した
熱延鋼板を角形ロール成形し、角形電縫鋼管を製造し
た。そして、この角鋼管に455 ℃でＺｎめっきを施し、
割れ発生の有無（表１）を調査した。表１より、1050℃
以下での圧下率を60％以下とすることにより、管コーナ
ー内面の割れ発生を防止できることを認めた。That is, C: 0.07% by weight, Si: 0.05% by weight, Mn: 0.40% by weight, P: 0.013% by weight, S: 0.005%
For steel materials of 10% by weight, the reduction rate at 1050 ° C or less
The hot-rolled steel sheet manufactured by changing each of 3, 58, 60, 65 and 75% was formed into a square roll to manufacture a square electric resistance welded steel pipe. Then, this square steel pipe is plated with Zn at 455 ° C.
The occurrence of cracks (Table 1) was investigated. From Table 1, 1050 ℃
It was recognized that by setting the rolling reduction below 60% or less, it was possible to prevent the occurrence of cracks on the inner surface of the pipe corner.
【００２１】[0021]
【表１】 [Table 1]
【００２２】[0022]
【実施例】熱間圧延における1050℃以下の圧下量（Ｒ
-1050)を変化させて製造した熱延鋼板を用い、ロール成
形法にて角鋼管を製造した。平坦部のＬ方向引張試験、
コーナー部の 0℃におけるＬ方向シャルピー試験を実施
した。並びに、実管を酸洗、フラックス処理した後455
℃の溶融Ｚｎめっき槽へ180 秒浸漬するめっき割れ試験
を実施した。[Embodiment] A reduction amount (R) of 1050 ° C. or less in hot rolling.
A square steel pipe was manufactured by a roll forming method using a hot-rolled steel sheet manufactured by changing -1050 ). L direction tensile test of flat part,
An L-direction Charpy test at 0 ° C. at the corner was performed. After pickling and fluxing the actual pipe, 455
A plating crack test was conducted by immersing in a hot-dip Zn plating bath at 180 ° C. for 180 seconds.
【００２３】[0023]
【表２】 [Table 2]
【００２４】表２にまとめた結果のように、本請求範囲
内の化学組成でＲ-1050 を60％以下とすることでＺｎめ
っき割れを回避できる。平坦部の引張強さは、本実施例
ではいずれも500MPa以上であり490MPaグレードとしての
強度を有しており、また、コーナー部の 0℃におけるシ
ャルピー吸収エネルギーは、いずれも30Ｊ以上となって
おり靱性も良好である。As shown in Table 2, Zn plating cracks can be avoided by setting R- 1050 to 60% or less with the chemical composition within the scope of the present invention. In this example, the tensile strength of the flat portion was 500 MPa or more in each case, and the strength was as 490 MPa grade.The Charpy absorption energy at 0 ° C. of the corner portion was 30 J or more in each case. Good toughness.
【００２５】以上、本発明の実施例を図面により詳述し
たが、本発明の具体的な構成はこの実施例に限られるも
のではなく、本発明の要旨を逸脱しない範囲の設計の変
更等があっても本発明に含まれる。例えば、本発明の角
鋼管は、熱延鋼板を円形電縫鋼管とした後に角鋼管とす
るものに限らず、熱延鋼板を直ちに角形成形するもので
あっても良い。Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration of the present invention is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. Even if present, it is included in the present invention. For example, the square steel pipe of the present invention is not limited to a square steel pipe after a hot rolled steel sheet is formed into a circular electric resistance welded steel pipe, but may be a steel sheet immediately formed into a square shape.
【００２６】[0026]
【発明の効果】以上のように本発明によれば、熱延鋼板
を角形ロール成形し、更に、溶融Ｚｎめっきを施して製
造される角鋼管において、低コストで、耐Ｚｎめっき割
れ性に優れ、強度、靱性も良好な角鋼管を製造可能とす
ることができる。As described above, according to the present invention, a square steel pipe manufactured by forming a hot rolled steel sheet into a square roll and further performing hot-dip Zn plating is low in cost and excellent in cracking resistance to Zn plating. It is possible to manufacture a square steel pipe having good strength and toughness.
【図１】図１は角鋼管辺部の引張強さとＣ量の関係を示
す線図である。FIG. 1 is a diagram showing the relationship between the tensile strength at the side of a square steel pipe and the amount of carbon.
【図２】図２は角鋼管コーナー部の 0℃でのシャルピー
吸収エネルギーとＣ量の関係を示す線図である。FIG. 2 is a diagram showing the relationship between the Charpy absorbed energy at 0 ° C. and the C content at the corners of a square steel pipe.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 ＦＩ Ｃ２２Ｃ 38/14 Ｃ２２Ｃ 38/14 (56)参考文献 特開 平５−69039（ＪＰ，Ａ) 特開 平５−17820（ＪＰ，Ａ) 特開 平２−145721（ＪＰ，Ａ) 特開 昭64−56853（ＪＰ，Ａ) (58)調査した分野(Int.Cl.6，ＤＢ名) C21D 8/00 - 8/10 B21C 37/15 B21D 5/12 ──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. 6 identification code FI C22C 38/14 C22C 38/14 (56) References JP-A-5-69039 (JP, A) JP-A-5-17820 (JP) JP-A-2-145721 (JP, A) JP-A-64-56853 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) C21D 8/00-8/10 B21C 37/15 B21D 5/12
Claims (3)
％以下、Ｍｎ：0.2〜2.0 重量％、残部Ｆｅ及び不可避
不純物からなる鋼を、1050℃以下での圧下率を60％以下
とする条件で熱間圧延することを特徴とする耐Ｚｎめっ
き割れ性に優れた高靱性角鋼管用熱延鋼板の製造方法。1. A steel comprising C: 0.02 to 0.12% by weight, Si: 0.5% by weight or less, Mn: 0.2 to 2.0% by weight, balance Fe and unavoidable impurities, and a reduction at 1050 ° C. or less of 60% or less. A method for producing a hot-rolled steel sheet for a high toughness square steel pipe having excellent resistance to cracking of Zn plating, characterized by hot rolling under the following conditions.
0.08重量％以下、Ｔｉ：0.05重量％以下を１種又は２種
以上含むことを特徴とする請求項１に記載の耐Ｚｎめっ
き割れ性に優れた高靱性角鋼管用熱延鋼板の製造方法。2. The steel according to claim 1, wherein Nb: 0.08% by weight or less, V:
The method for producing a hot-rolled steel sheet for a high-toughness square steel pipe excellent in Zn plating crack resistance according to claim 1, comprising one or more of 0.08% by weight or less and Ti: 0.05% by weight or less.
した熱延鋼板を角形ロール成形してなる耐Ｚｎめっき割
れ性に優れた高靱性角鋼管。3. A high-toughness square steel pipe formed by subjecting a hot-rolled steel sheet produced by the method according to claim 1 or 2 to square roll forming and having excellent zinc plating crack resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16298294A JP2902304B2 (en) | 1994-06-22 | 1994-06-22 | Method of manufacturing hot-rolled steel sheet for high toughness square steel pipe excellent in Zn plating crack resistance and high toughness square steel pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16298294A JP2902304B2 (en) | 1994-06-22 | 1994-06-22 | Method of manufacturing hot-rolled steel sheet for high toughness square steel pipe excellent in Zn plating crack resistance and high toughness square steel pipe |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH083634A JPH083634A (en) | 1996-01-09 |
| JP2902304B2 true JP2902304B2 (en) | 1999-06-07 |
Family
ID=15764972
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16298294A Expired - Lifetime JP2902304B2 (en) | 1994-06-22 | 1994-06-22 | Method of manufacturing hot-rolled steel sheet for high toughness square steel pipe excellent in Zn plating crack resistance and high toughness square steel pipe |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2902304B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5811905B2 (en) * | 2012-03-12 | 2015-11-11 | 新日鐵住金株式会社 | Overlapping hot press member and manufacturing method thereof |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6456853A (en) * | 1987-08-28 | 1989-03-03 | Nippon Kokan Kk | Square tube excellent in molten zinc cracking resistance |
| JPH02145721A (en) * | 1988-11-28 | 1990-06-05 | Nippon Steel Corp | Manufacture of steel material having excellent lme resistance |
| JP2573109B2 (en) * | 1991-07-12 | 1997-01-22 | 新日本製鐵株式会社 | Method for producing high-strength steel for Zn plating crack resistant structure |
| JPH0569039A (en) * | 1991-09-13 | 1993-03-23 | Nkk Corp | Manufacturing method of large-diameter rectangular steel pipe |
-
1994
- 1994-06-22 JP JP16298294A patent/JP2902304B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH083634A (en) | 1996-01-09 |
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| Date | Code | Title | Description |
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| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 19990309 |