WO2019176979A1 - Method for manufacturing square steel tube, and square steel tube - Google Patents
Method for manufacturing square steel tube, and square steel tube Download PDFInfo
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- WO2019176979A1 WO2019176979A1 PCT/JP2019/010151 JP2019010151W WO2019176979A1 WO 2019176979 A1 WO2019176979 A1 WO 2019176979A1 JP 2019010151 W JP2019010151 W JP 2019010151W WO 2019176979 A1 WO2019176979 A1 WO 2019176979A1
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- steel pipe
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- forming
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
- B21C37/15—Making tubes of special shape; Making tube fittings
- B21C37/155—Making tubes with non circular section
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
- B21C37/08—Making tubes with welded or soldered seams
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
- B21C37/15—Making tubes of special shape; Making tube fittings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
- B21D5/06—Bending sheet metal along straight lines, e.g. to form simple curves by drawing procedure making use of dies or forming-rollers, e.g. making profiles
- B21D5/10—Bending sheet metal along straight lines, e.g. to form simple curves by drawing procedure making use of dies or forming-rollers, e.g. making profiles for making tubes
- B21D5/12—Bending sheet metal along straight lines, e.g. to form simple curves by drawing procedure making use of dies or forming-rollers, e.g. making profiles for making tubes making use of forming-rollers
Abstract
Description
(1)円筒状の素管である鋼管を角鋼管に成形する場合、上述したように、複数段のロール群に鋼管を通すことで、徐々に円筒形から角形に角成形を施す。ここで角成形において、辺に含まれる直線部の曲げ戻し、角部の曲げおよび周方向の絞り変形が発生する。特に角部周辺は、ロールがほぼ接触することなく角成形が完了する。すなわち、角成形において、角部は自由変形により張り出すことにより、鋼管から角部が形成される。
(2)角部は角成形直前の鋼管の周長に対して、角成形における周方向絞りの余剰分から形成される。本発明では、角成形直前の鋼管の周長と角成形直後の鋼管の周長の比が特定の範囲となることで、角部の曲率半径の寸法精度に優れた角鋼管を得ることができる。
(3)角成形直前の鋼管の周長と角成形直後の鋼管の周長の比は、角鋼管の肉厚と対向する辺の外表面間距離の関係式で表すことができる。また、角成形直前のサイジングスタンドのギャップを制御することにより、角成形直前の鋼管の周長と角成形直後の鋼管の周長の比を、特定の範囲に制御することができる。 The present inventors diligently studied various factors that affect the radius of curvature of the corner of the square steel pipe. As a result, the following was found.
(1) When forming a steel pipe, which is a cylindrical raw pipe, into a square steel pipe, as described above, the steel pipe is passed through a plurality of stages of rolls, so that the square is gradually formed from a cylindrical shape to a square shape. Here, in the corner forming, the straight portion included in the side is bent back, the corner is bent, and the circumferential drawing is deformed. In particular, corner forming is completed in the vicinity of the corner portion without almost contacting the roll. That is, in the corner forming, the corner portion is formed from the steel pipe by protruding by free deformation.
(2) The corner portion is formed from a surplus of the circumferential drawing in the corner forming with respect to the circumference of the steel pipe immediately before the corner forming. In the present invention, the ratio of the circumferential length of the steel pipe immediately before the square forming and the circumferential length of the steel pipe immediately after the square forming is in a specific range, so that a square steel pipe excellent in dimensional accuracy of the curvature radius of the corner can be obtained. .
(3) The ratio of the circumferential length of the steel pipe immediately before the square forming and the circumferential length of the steel pipe immediately after the square forming can be expressed by a relational expression of the distance between the outer surfaces of the sides facing the thickness of the square steel pipe. Further, by controlling the gap of the sizing stand immediately before the square forming, the ratio of the circumferential length of the steel pipe immediately before the square forming and the circumferential length of the steel pipe immediately after the square forming can be controlled within a specific range.
[1]角鋼管の角部におけるビッカース硬さが下記式(2)を満たし、かつ、
前記角部の曲率半径が、下記式(3)を満たす角鋼管。
10≦HVI―HVO≦80 ・・・(2)
Rmax-Rmin≦0.25×t ・・・(3)
なお、式(2)、式(3)において、
HVO:角鋼管の角部における鋼管外面側から1±0.2mmの範囲の位置におけるビッカース硬さ(HV)
HVI:角鋼管の角部における鋼管内面側から1±0.2mmの範囲の位置におけるビッカース硬さ(HV)
Rmax:鋼管軸方向に対して任意の垂直断面における、角部の曲率半径の最大値(mm)
Rmin:鋼管軸方向に対して任意の垂直断面における、角部の曲率半径の最小値(mm)
t:肉厚(mm)
である。
[2]角鋼管の角部におけるビッカース硬さが下記式(4)を満たす[1]に記載の角鋼管。
290×t/H-3.2≦HVI―HVO≦579×t/H+33.7 ・・・(4)
[3]前記肉厚が25~30mmである[1]または[2]に記載の角鋼管。
[4]素材としての鋼板をロール成形し、次いで、ロール成形した鋼板を電縫溶接して電縫鋼管とした後、前記電縫鋼管を複数段のサイジングスタンドにて成形し、次いで複数段の角成形スタンドにて角成形して角鋼管を製造する方法であって、
下記式(1)を満たすように、角成形直前のサイジングスタンドのギャップを制御する角鋼管の製造方法。
CIN/COUT≧0.50×t/H+0.99 ・・・(1)
なお、式(1)において、
CIN:第一段目の角成形スタンド入側における鋼管の周長(mm)
COUT:最終段の角成形スタンド出側における鋼管の周長(mm)
t:肉厚(mm)
H:対向する辺の外表面間距離(mm)
である。
[5]前記肉厚が25~30mmである[4]に記載の角鋼管の製造方法。 The present invention is based on the above findings, and the features thereof are as follows.
[1] The Vickers hardness at the corner of the square steel pipe satisfies the following formula (2), and
A square steel pipe in which the radius of curvature of the corner satisfies the following formula (3).
10 ≦ HV I −HV O ≦ 80 (2)
R max −R min ≦ 0.25 × t (3)
In the formulas (2) and (3),
HV O : Vickers hardness (HV) at a position in the range of 1 ± 0.2 mm from the outer surface side of the steel pipe at the corner of the square steel pipe
HV I : Vickers hardness (HV) at a position in the range of 1 ± 0.2 mm from the inner surface of the steel pipe at the corner of the square steel pipe
R max : Maximum value of the radius of curvature of the corner (mm) in any vertical cross section with respect to the steel pipe axis direction
R min : Minimum value (mm) of the radius of curvature of the corner in an arbitrary vertical cross section with respect to the steel pipe axis direction
t: Wall thickness (mm)
It is.
[2] The square steel pipe according to [1], wherein the Vickers hardness at the corner of the square steel pipe satisfies the following formula (4).
290 × t / H−3.2 ≦ HV I −HV O ≦ 579 × t / H + 33.7 (4)
[3] The square steel pipe according to [1] or [2], wherein the wall thickness is 25 to 30 mm.
[4] Roll forming a steel plate as a raw material, and then forming the electric resistance welded steel pipe by electro-welding the roll formed steel sheet, and then forming the electric resistance welded steel pipe in a plurality of sizing stands, A method of manufacturing a square steel pipe by forming a square steel tube with a square forming stand,
A method of manufacturing a square steel pipe that controls a gap of a sizing stand immediately before square forming so as to satisfy the following formula (1).
C IN / C OUT ≧ 0.50 × t / H + 0.99 (1)
In formula (1),
C IN : Perimeter of steel pipe (mm) on the entrance side of the first stage square forming stand
C OUT : Peripheral length of the steel pipe on the exit side of the last-stage square forming stand (mm)
t: Wall thickness (mm)
H: Distance between outer surfaces of opposing sides (mm)
It is.
[5] The method for manufacturing a square steel pipe according to [4], wherein the thickness is 25 to 30 mm.
CIN/COUT≧0.50×t/H+0.99 ・・・(1)
なお、式(1)において、
CIN:第一段目の角成形スタンド入側における鋼管の周長(mm)
COUT:最終段の角成形スタンド出側における鋼管の周長(mm)
t:肉厚(mm)
H:対向する辺の外表面間距離(mm)
である。 The results are shown in FIG. As shown in FIG. 4, it was found that when C IN / C OUT satisfies the following formula (1), a square steel pipe excellent in dimensional accuracy of the curvature radius of the corner can be easily obtained.
C IN / C OUT ≧ 0.50 × t / H + 0.99 (1)
In formula (1),
C IN : Perimeter of steel pipe (mm) on the entrance side of the first stage square forming stand
C OUT : Peripheral length of the steel pipe on the exit side of the last-stage square forming stand (mm)
t: Wall thickness (mm)
H: Distance between outer surfaces of opposing sides (mm)
It is.
10≦HVI―HVO≦80 ・・・(2)
Rmax-Rmin≦0.25×t ・・・(3)
なお、式(2)、式(3)において、
HVO:角鋼管の角部における鋼管外面側から1±0.2mmの範囲の位置におけるビッカース硬さ(HV)
HVI:角鋼管の角部における鋼管内面側から1±0.2mmの範囲の位置におけるビッカース硬さ(HV)
Rmax:鋼管軸方向に対して任意の垂直断面における、角部の曲率半径の最大値(mm)
Rmin:鋼管軸方向に対して任意の垂直断面における、角部の曲率半径の最小値(mm)
t:肉厚(mm)
である。 The square steel pipe of the present invention is characterized in that the Vickers hardness at the corner of the square steel pipe satisfies the following formula (2), and the radius of curvature of the corner satisfies the following formula (3).
10 ≦ HV I −HV O ≦ 80 (2)
R max −R min ≦ 0.25 × t (3)
In the formulas (2) and (3),
HV O : Vickers hardness (HV) at a position in the range of 1 ± 0.2 mm from the outer surface side of the steel pipe at the corner of the square steel pipe
HV I : Vickers hardness (HV) at a position in the range of 1 ± 0.2 mm from the inner surface of the steel pipe at the corner of the square steel pipe
R max : Maximum value of the radius of curvature of the corner (mm) in any vertical cross section with respect to the steel pipe axis direction
R min : Minimum value (mm) of the radius of curvature of the corner in an arbitrary vertical cross section with respect to the steel pipe axis direction
t: Wall thickness (mm)
It is.
290×t/H-3.2≦HVI―HVO≦579×t/H+33.7 ・・・(4)
上述したように、BCR法では、周方向の曲げ変形だけではなく、絞り変形による長手方向のひずみが発生するため、結果として周方向の曲げの中立軸が外面側へと移動し、内面側の方の硬さが大きくなる。このとき、角鋼管の肉厚が増加すると剛性が増加し、成形に要するひずみが増加する。また、角鋼管の肉厚と対向する辺の外表面間距離の比t/Hが大きくなると、絞り変形による成形ひずみが増加し、角鋼管の肉厚全体の硬さが増加する。したがって、t/Hが大きい角鋼管では角部の加工硬化がより顕著になる。このため、本発明者らは、角部の硬さと角鋼管のt/Hには関係があると考えた。本発明者らが鋭意検討した結果、上記式(4)を満たすことにより、角部の加工硬化の影響(延性悪化や溶接部の止端割れ)を抑制することができる。鋼管外面側と鋼管内面側のビッカース硬さの差が290×t/H+3.2HV未満の場合、外面側の加工硬化が進行しているため、角部の延性が著しく悪化する。ビッカース硬さの差が579×t/H+33.7HV超えの場合、角部内面側の加工度が進展しており、角部内面の残留応力が顕著になるため、後処理で施すめっきの割れなどに悪影響を及ぼす。 Moreover, in this invention, it is preferable that the Vickers hardness in the corner | angular part of a square steel pipe satisfy | fills following formula (4).
290 × t / H−3.2 ≦ HV I −HV O ≦ 579 × t / H + 33.7 (4)
As described above, in the BCR method, not only circumferential bending deformation but also longitudinal strain due to diaphragm deformation occurs, and as a result, the neutral axis of circumferential bending moves to the outer surface side, and the inner surface side The hardness of the direction increases. At this time, when the thickness of the square steel pipe increases, the rigidity increases and the strain required for forming increases. Further, when the ratio t / H of the distance between the outer surfaces of the opposite sides to the thickness of the square steel pipe increases, the forming strain due to the drawing deformation increases, and the hardness of the entire thickness of the square steel pipe increases. Therefore, the work hardening of the corner becomes more remarkable in the square steel pipe having a large t / H. For this reason, the present inventors considered that there is a relationship between the hardness of the corner and the t / H of the square steel pipe. As a result of intensive studies by the present inventors, satisfying the above formula (4) can suppress the effects of work hardening at the corners (deterioration of ductility and toe cracks in the welded portion). When the difference in Vickers hardness between the outer surface side of the steel pipe and the inner surface side of the steel pipe is less than 290 × t / H + 3.2 HV, work hardening on the outer surface side proceeds, so that the ductility of the corners is significantly deteriorated. When the difference in Vickers hardness exceeds 579 × t / H + 33.7HV, the degree of processing on the inner surface of the corner is progressing, and the residual stress on the inner surface of the corner becomes significant, so that the cracks in the plating applied in post-processing, etc. Adversely affect.
Cは、固溶強化により鋼板の強度を増加させるとともに、第二相の一つであるパーライトの形成に寄与する元素である。Cは、さらに焼入れ性を高めてマルテンサイトの生成に寄与し、オーステナイトの安定化に寄与する元素であることから、硬質相の形成にも寄与する元素である。したがって、所望の引張特性、靭性、さらに所望の鋼板組織を確保するためには、0.04%以上の含有であることが好ましい。一方、0.50%を超える含有は、硬質相の割合が高くなり靱性が低下し、また角形鋼管の溶接時(例えば、角形鋼管同士の溶接時)にマルテンサイト組織が生成し溶接割れの原因となる懸念がある。このため、Cは0.04~0.50%の範囲であることが好ましく、0.07~0.20%がより好ましい。さらに好ましくは、0.12%超0.25%以下である。 C: 0.04 to 0.50%
C is an element that contributes to the formation of pearlite, which is one of the second phases, while increasing the strength of the steel sheet by solid solution strengthening. C is an element that contributes to the formation of a hard phase because it further enhances the hardenability and contributes to the formation of martensite and contributes to the stabilization of austenite. Therefore, in order to secure desired tensile properties, toughness, and a desired steel sheet structure, the content is preferably 0.04% or more. On the other hand, if the content exceeds 0.50%, the ratio of the hard phase increases and the toughness decreases, and a martensitic structure is formed during welding of square steel pipes (for example, when welding square steel pipes), causing weld cracking. There is concern to become. Therefore, C is preferably in the range of 0.04 to 0.50%, more preferably 0.07 to 0.20%. More preferably, it is more than 0.12% and 0.25% or less.
Siは、固溶強化で鋼板の強度増加に寄与する元素であり、所望の鋼板強度を確保するために、必要に応じて含有できる。このような効果を得るためには、0.01%以上のSiの含有が望ましい。一方、Si含有量が2.0%を超えると溶接性が悪化する。このため、Si含有量は2.0%以下とすることが好ましく、0.5%以下とすることがより好ましい。なお、0.4%以上の含有は、鋼板表面に赤スケールと称するファイアライトが形成しやすくなり、表面の外観性状が低下する場合が多くなる。このため、含有する場合には、0.4%未満とすることがさらに好ましい。なお、特にSiを添加しない場合は、Siは不可避的不純物として、そのレベルは0.01%未満である。 Si: 2.0% or less Si is an element that contributes to an increase in the strength of the steel sheet by solid solution strengthening, and can be contained as necessary in order to ensure a desired steel sheet strength. In order to obtain such an effect, the Si content is desirably 0.01% or more. On the other hand, if the Si content exceeds 2.0%, the weldability deteriorates. For this reason, the Si content is preferably 2.0% or less, and more preferably 0.5% or less. In addition, the content of 0.4% or more facilitates the formation of a firelight called red scale on the steel sheet surface, and the appearance quality of the surface often decreases. For this reason, when it contains, it is more preferable to set it as less than 0.4%. In particular, when Si is not added, Si is an inevitable impurity, and its level is less than 0.01%.
Mnは、固溶強化を介して鋼板の強度を増加させる元素であり、またフェライト変態開始温度を低下させることで組織の微細化に寄与する元素である。0.3%未満の含有では、フェライト変態開始温度の上昇を招き、組織が過度に粗大化しやすい。また、所望の鋼板強度および組織を確保するために、Mnは0.3%以上の含有であることが好ましい。しかしながら、Mn含有量が3.0%を超えると溶接性が悪化する。このため、Mn含有量は0.3~3.0%とすることが好ましい。なお、2.0%を超えて含有すると、中心偏析部の硬度が上昇し、角形鋼管の現場溶接時の割れの原因となる懸念がある。このため、Mnは0.3~2.0%であることがさらに好ましい。最も好ましくは、0.5~2.0%である。 Mn: 0.3 to 3.0%
Mn is an element that increases the strength of the steel sheet through solid solution strengthening, and is an element that contributes to refinement of the structure by lowering the ferrite transformation start temperature. If the content is less than 0.3%, the ferrite transformation start temperature rises and the structure tends to become excessively coarse. Moreover, in order to ensure desired steel plate intensity | strength and structure | tissue, it is preferable that Mn contains 0.3% or more. However, if the Mn content exceeds 3.0%, the weldability deteriorates. For this reason, the Mn content is preferably 0.3 to 3.0%. If the content exceeds 2.0%, the hardness of the central segregation part increases, which may cause cracks during field welding of the square steel pipe. Therefore, Mn is more preferably 0.3 to 2.0%. Most preferably, it is 0.5 to 2.0%.
Pは、フェライト粒界に偏析して、靭性を低下させる作用を有する元素であり、本発明では、不純物としてできるだけ低減することが望ましい。しかし、過度の低減は、精錬コストの高騰を招くため、0.002%以上とすることが好ましい。なお、0.10%までは許容できる。このため、Pは0.10%以下であることが好ましい。Pは、より好ましくは0.03%以下であり、さらに好ましくは0.025%以下である。 P: 0.10% or less P is an element that has the effect of segregating at the ferrite grain boundaries and reducing toughness. In the present invention, P is preferably reduced as much as possible. However, excessive reduction leads to an increase in refining costs, so 0.002% or more is preferable. In addition, up to 0.10% is acceptable. For this reason, it is preferable that P is 0.10% or less. P is more preferably 0.03% or less, and still more preferably 0.025% or less.
Sは、鋼中では硫化物として存在し、本発明の組成範囲であれば、主としてMnSとして存在する。MnSは、熱延工程で薄く延伸され、延性、靭性に悪影響を及ぼすため、本発明ではできるだけMnSは低減することが望ましい。しかし、過度の低減は、精錬コストの高騰を招くため、Sは0.0002%以上とすることが好ましい。なお、0.050%までは許容できる。このため、Sは0.050%以下であることが好ましい。Sは、より好ましくは0.015%であり、さらに好ましくは0.010%以下である。 S: 0.050% or less S is present as sulfide in steel, and is mainly present as MnS within the composition range of the present invention. Since MnS is thinly stretched in the hot rolling step and adversely affects ductility and toughness, it is desirable to reduce MnS as much as possible in the present invention. However, excessive reduction leads to an increase in refining costs, so S is preferably 0.0002% or more. In addition, up to 0.050% is acceptable. For this reason, it is preferable that S is 0.050% or less. S is more preferably 0.015%, and still more preferably 0.010% or less.
Alは、脱酸剤として作用するとともに、AlNとしてNを固定する作用を有する元素である。このような効果を得るためには、0.005%以上の含有を必要とする。0.005%未満では、Si無添加の場合に脱酸力が不足し、酸化物系介在物が増加し、鋼板の清浄度が低下する。一方、0.10%を超える含有は、固溶Al量が増加し、角形鋼管の長手溶接時(角形鋼管の製造時の溶接時)に、特に大気中での溶接の場合に、溶接部に酸化物を形成させる危険性が高くなり、角形鋼管溶接部の靭性が低下するとともに、アルミナ系介在物が多くなり、表面性状が悪化する。このため、Alは0.005~0.10%であることが好ましい。Alは0.01~0.06%であることがより好ましい。 Al: 0.005 to 0.10%
Al is an element that acts as a deoxidizer and has the effect of fixing N as AlN. In order to acquire such an effect, 0.005% or more of content is required. If it is less than 0.005%, the deoxidizing power is insufficient when Si is not added, the oxide inclusions increase, and the cleanliness of the steel sheet decreases. On the other hand, if the content exceeds 0.10%, the amount of solute Al increases, and when welding square steel pipes in the longitudinal direction (when welding square steel pipes), especially in the atmosphere, The risk of forming an oxide increases, the toughness of the welded portion of the square steel pipe decreases, and the amount of alumina inclusions increases, resulting in deterioration of the surface properties. Therefore, Al is preferably 0.005 to 0.10%. More preferably, Al is 0.01 to 0.06%.
Nは、転位の運動を強固に固着することで靭性を低下させる作用を有する元素である。本発明では、Nは不純物としてできるだけ低減することが望ましく、0.010%までは許容できる。このため、Nは0.010%以下であることが好ましい。Nは、より好ましくは0.0080%以下であり、さらに好ましくは0.006%以下であり、最も好ましくは0.005%以下である。 N: 0.010% or less N is an element having an effect of lowering toughness by firmly fixing dislocation movement. In the present invention, it is desirable to reduce N as an impurity as much as possible, and it is acceptable up to 0.010%. For this reason, it is preferable that N is 0.010% or less. N is more preferably 0.0080% or less, still more preferably 0.006% or less, and most preferably 0.005% or less.
Nb、Ti、Vは、いずれも鋼中で微細な炭化物、窒化物を形成し、析出強化を通じて鋼の強度向上に寄与する元素であり、必要に応じて含有できる。このような効果を得るためには、Nb:0.005%以上、Ti:0.005%以上、V:0.005%以上の含有が必要である。一方で、過度の含有は降伏比の上昇および靱性の低下を招く。このためNb、Ti、Vの含有量は、Nb:0.005~0.150%、Ti:0.005~0.150%、V:0.005~0.150%とすることが好ましい。より好ましくは、Nb:0.008~0.10%、Ti:0.008~0.10%、V:0.008~0.10%である。 One or more selected from Nb: 0.005 to 0.150%, Ti: 0.005 to 0.150%, V: 0.005 to 0.150% Nb, Ti and V are These are elements that form fine carbides and nitrides in steel and contribute to improving the strength of steel through precipitation strengthening, and can be contained as required. In order to obtain such an effect, it is necessary to contain Nb: 0.005% or more, Ti: 0.005% or more, and V: 0.005% or more. On the other hand, excessive inclusion causes an increase in yield ratio and a decrease in toughness. Therefore, the contents of Nb, Ti, and V are preferably Nb: 0.005 to 0.150%, Ti: 0.005 to 0.150%, and V: 0.005 to 0.150%. More preferably, Nb is 0.008 to 0.10%, Ti is 0.008 to 0.10%, and V is 0.008 to 0.10%.
Cr、Mo、Cu、Niは、固溶強化により鋼の強度を上昇させる元素であり、またいずれも鋼の焼入れ性を高め、オーステナイトの安定化に寄与する元素であることから、硬質なマルテンサイトおよびオーステナイトの形成に寄与する元素であり、必要に応じて含有できる。このような効果を得るためには、Cr:0.01%以上、Mo:0.01%以上、Cu:0.01%以上、Ni:0.01%以上の含有が必要である。一方で、過度の含有は靱性の低下および溶接性の悪化を招く。このためCr、Mo、Cu、Niの含有量は、Cr:0.01~1.0%、Mo:0.01~1.0%、Cu:0.01~0.50%、Ni:0.01~0.30%とすることが好ましい。より好ましくは、Cr:0.1~1.0%、Mo:0.1~1.0%、Cu:0.1~0.50%、Ni:0.1~0.30%である。 Cr: 0.01 to 1.0%, Mo: 0.01 to 1.0%, Cu: 0.01 to 0.50%, Ni: 0.01 to 0.30%
Cr, Mo, Cu, and Ni are elements that increase the strength of the steel by solid solution strengthening, and all of them are elements that increase the hardenability of the steel and contribute to the stabilization of austenite. And an element that contributes to the formation of austenite, and can be contained if necessary. In order to obtain such an effect, it is necessary to contain Cr: 0.01% or more, Mo: 0.01% or more, Cu: 0.01% or more, and Ni: 0.01% or more. On the other hand, excessive inclusion causes a decrease in toughness and a deterioration in weldability. Therefore, the contents of Cr, Mo, Cu, and Ni are as follows: Cr: 0.01 to 1.0%, Mo: 0.01 to 1.0%, Cu: 0.01 to 0.50%, Ni: 0 It is preferable that the content be 0.01% to 0.30%. More preferably, Cr: 0.1 to 1.0%, Mo: 0.1 to 1.0%, Cu: 0.1 to 0.50%, Ni: 0.1 to 0.30%.
Caは、熱間圧延工程で薄く延伸されるMnS等の硫化物を球状化することで鋼の靱性向上に寄与する元素であり、必要に応じて含有できる。このような効果を得るためには、0.001%以上のCaを含有することが好ましい。しかし、Ca含有量が0.010%を超えると、鋼中にCa酸化物クラスターが形成され靱性が悪化する場合がある。このため、Ca含有量は0.001~0.010%とすることが好ましい。より好ましくは、Ca含有量は0.001~0.0050%である。 Ca: 0.001 to 0.010%
Ca is an element that contributes to improving the toughness of steel by spheroidizing sulfides such as MnS that are thinly stretched in the hot rolling process, and can be contained as necessary. In order to acquire such an effect, it is preferable to contain 0.001% or more of Ca. However, if the Ca content exceeds 0.010%, Ca oxide clusters may be formed in the steel and the toughness may deteriorate. Therefore, the Ca content is preferably 0.001 to 0.010%. More preferably, the Ca content is 0.001 to 0.0050%.
Bは、フェライト変態開始温度を低下させることで組織の微細化に寄与する元素である。このような効果を得るためには、0.0005%以上のBを含有することを必要とする。しかしながら、B含有量が0.010%を超えると降伏比が上昇する。このため、B含有量は0.0005~0.010%とすることが好ましい。より好ましくは、B含有量は0.0005~0.0050%である。 B: 0.0005 to 0.010%
B is an element that contributes to refinement of the structure by lowering the ferrite transformation start temperature. In order to obtain such an effect, it is necessary to contain 0.0005% or more of B. However, when the B content exceeds 0.010%, the yield ratio increases. Therefore, the B content is preferably 0.0005 to 0.010%. More preferably, the B content is 0.0005 to 0.0050%.
2 レベラー
3 ケージロール群
4 フィンパスロール群
5 スクイズロール
6 溶接機
7 電縫鋼管
8 サイジングロール群
9 角成形ロール群
10 角鋼管
R1~R3 (鋼管の)形状 DESCRIPTION OF
Claims (5)
- 角鋼管の角部におけるビッカース硬さが下記式(2)を満たし、かつ、
前記角部の曲率半径が、下記式(3)を満たす角鋼管。
10≦HVI―HVO≦80 ・・・(2)
Rmax-Rmin≦0.25×t ・・・(3)
なお、式(2)、式(3)において、
HVO:角鋼管の角部における鋼管外面側から1±0.2mmの範囲の位置におけるビッカース硬さ(HV)
HVI:角鋼管の角部における鋼管内面側から1±0.2mmの範囲の位置におけるビッカース硬さ(HV)
Rmax:鋼管軸方向に対して任意の垂直断面における、角部の曲率半径の最大値(mm)
Rmin:鋼管軸方向に対して任意の垂直断面における、角部の曲率半径の最小値(mm)
t:肉厚(mm)
である。 The Vickers hardness at the corner of the square steel pipe satisfies the following formula (2), and
A square steel pipe in which the radius of curvature of the corner satisfies the following formula (3).
10 ≦ HV I −HV O ≦ 80 (2)
R max −R min ≦ 0.25 × t (3)
In the formulas (2) and (3),
HV O : Vickers hardness (HV) at a position in the range of 1 ± 0.2 mm from the outer surface side of the steel pipe at the corner of the square steel pipe
HV I : Vickers hardness (HV) at a position in the range of 1 ± 0.2 mm from the inner surface of the steel pipe at the corner of the square steel pipe
R max : Maximum value of the radius of curvature of the corner (mm) in any vertical cross section with respect to the steel pipe axis direction
R min : Minimum value (mm) of the radius of curvature of the corner in an arbitrary vertical cross section with respect to the steel pipe axis direction
t: Wall thickness (mm)
It is. - 角鋼管の角部におけるビッカース硬さが下記式(4)を満たす請求項1に記載の角鋼管。
290×t/H-3.2≦HVI―HVO≦579×t/H+33.7 ・・・(4) The square steel pipe according to claim 1, wherein the Vickers hardness at the corner of the square steel pipe satisfies the following formula (4).
290 × t / H−3.2 ≦ HV I −HV O ≦ 579 × t / H + 33.7 (4) - 前記肉厚が25~30mmである請求項1または2に記載の角鋼管。 The square steel pipe according to claim 1 or 2, wherein the wall thickness is 25 to 30 mm.
- 素材としての鋼板をロール成形し、次いで、ロール成形した鋼板を電縫溶接して電縫鋼管とした後、前記電縫鋼管を複数段のサイジングスタンドにて成形し、次いで複数段の角成形スタンドにて角成形して角鋼管を製造する方法であって、
下記式(1)を満たすように、角成形直前のサイジングスタンドのギャップを制御する角鋼管の製造方法。
CIN/COUT≧0.50×t/H+0.99 ・・・(1)
なお、式(1)において、
CIN:第一段目の角成形スタンド入側における鋼管の周長(mm)
COUT:最終段の角成形スタンド出側における鋼管の周長(mm)
t:肉厚(mm)
H:対向する辺の外表面間距離(mm)
である。 The steel sheet as a raw material is roll-formed, and then the roll-formed steel sheet is electro-welded to form an electric-welded steel pipe, and then the electric-welded steel pipe is formed in a multi-stage sizing stand, and then a multi-stage square forming stand A method of manufacturing a square steel pipe by forming a square with
A method of manufacturing a square steel pipe that controls a gap of a sizing stand immediately before square forming so as to satisfy the following formula (1).
C IN / C OUT ≧ 0.50 × t / H + 0.99 (1)
In formula (1),
C IN : Perimeter of steel pipe (mm) on the entrance side of the first stage square forming stand
C OUT : Peripheral length of the steel pipe on the exit side of the last-stage square forming stand (mm)
t: Wall thickness (mm)
H: Distance between outer surfaces of opposing sides (mm)
It is. - 前記肉厚が25~30mmである請求項4に記載の角鋼管の製造方法。 The method for manufacturing a square steel pipe according to claim 4, wherein the wall thickness is 25 to 30 mm.
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CN112048663A (en) * | 2020-08-07 | 2020-12-08 | 山东钢铁股份有限公司 | Production method of low-cost high-strength rectangular steel pipe |
JP2021188104A (en) * | 2020-06-03 | 2021-12-13 | Jfeスチール株式会社 | Rectangular steel tube and its manufacturing method, as well as building structure |
JP2021188105A (en) * | 2020-06-03 | 2021-12-13 | Jfeスチール株式会社 | Rectangular steel tube and its manufacturing method, as well as building structure |
WO2023276644A1 (en) * | 2021-07-02 | 2023-01-05 | Jfeスチール株式会社 | Square steel tube, method for manufacturing same, and building structure |
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