WO2021039484A1 - Rectangular steel pipe and method for manufacturing same, and building structure - Google Patents
Rectangular steel pipe and method for manufacturing same, and building structure Download PDFInfo
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- WO2021039484A1 WO2021039484A1 PCT/JP2020/031054 JP2020031054W WO2021039484A1 WO 2021039484 A1 WO2021039484 A1 WO 2021039484A1 JP 2020031054 W JP2020031054 W JP 2020031054W WO 2021039484 A1 WO2021039484 A1 WO 2021039484A1
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- square
- steel pipe
- flat plate
- stand
- corner
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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
-
- 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
- B21C37/0803—Making tubes with welded or soldered seams the tubes having a special shape, e.g. polygonal tubes
-
- 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
- B21D51/00—Making hollow objects
- B21D51/02—Making hollow objects characterised by the structure of the objects
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Definitions
- the present invention relates to a square steel pipe having high toughness and a low yield ratio, which is used for building members of medium-rise buildings, factories, warehouses and other large buildings having a height of more than 20 m.
- the pillar material of a building is a four-sided box column manufactured by welding four thick steel plates, or a press-formed square manufactured by cold press bending and then welding one or two thick steel plates.
- Steel pipes have been widely used in the past, but in recent years, in order to reduce costs and shorten the construction period, the use of roll-formed square steel pipes that can be manufactured at low cost and in a short period of time is increasing.
- the steel strip is formed into a cylindrical open pipe shape by cold roll forming, the butt portion is welded by electric stitching, and then the steel strip is squeezed in the tubular axial direction by the rolls arranged vertically and horizontally. Is added and subsequently formed into a square shape.
- the butt portion is heated, melted, pressure-welded and solidified to complete the joining.
- the roll-formed square steel pipe has a large difference in strength, ductility, and toughness in the peripheral cross section, which causes problems such as complicated selection of welding material, welding method, and building structure design in welding with the diaphragm.
- the seismic performance of building structures that use roll-formed square steel pipes as columns by suppressing the ductility and toughness of roll-formed square steel pipes from becoming partially low, as columns. It has been sought to further improve the deformation performance and impact resistance performance of the steel pipe.
- a square steel pipe causes a large strain on the outer surface of the corner when deformed by an external force such as an earthquake, it is necessary to improve the ductility and toughness of the outer surface of the corner.
- Patent Document 1 Japanese Patent Document 1
- Patent Document 2 Japanese Patent Document 1
- Patent Document 3 A square steel pipe characterized by being obtained by cooling has been proposed.
- Patent Document 2 proposes a square steel pipe in which a cold-formed portion is heat-treated.
- Patent Document 3 improves the toughness and plastic deformability of the corners by appropriately controlling the chemical composition of the material steel sheet, the bainite fraction of the metal structure, and the Vickers hardness of the surface layer of the corners.
- Square steel pipes have been proposed.
- Patent Document 4 proposes a square steel pipe having improved toughness at the corners by appropriately controlling the chemical composition of the material steel sheet and the average crystal grain size of the hard phase of the metal structure and ferrite.
- Patent Documents 5 and 6 disclose techniques for improving shape characteristics by adjusting manufacturing conditions during roll molding. Specifically, in Patent Document 5, when a steel pipe is formed into a square pipe with a three-stage or four-stage square forming roll and the reduction rate of the final stage roll is constant, the wall thickness / outer diameter ratio of the steel pipe becomes large. As a result, a technique for forming a square steel pipe in which the roll caliber in the final stage is made smaller (from a convex shape to a concave shape) is disclosed.
- a technique for manufacturing a structural square tube that undergoes the second and subsequent stages of forming a raw tube formed into a shape into a target shape is disclosed.
- Japanese Unexamined Patent Publication No. 2004-330222 Japanese Unexamined Patent Publication No. 10-60580
- Japanese Patent No. 5385760 JP-A-2018-53281 Japanese Unexamined Patent Publication No. 4-224023 Japanese Patent No. 3197661
- Patent Documents 5 and 6 are used as techniques for flattening the flat plate portion of the square steel pipe, reducing the variation in hardness within the peripheral cross section, and sufficiently ensuring the ductility and toughness of the outer surface of the square portion. Was not enough.
- the present invention has been made in view of the above circumstances, and is a square steel pipe having a small variation in hardness in the peripheral cross section, excellent ductility and toughness on the outer surface of the corner, and having a flat flat plate portion, and a method for manufacturing the same. In addition, it aims to provide a building structure having excellent seismic performance.
- the small variation in hardness in the peripheral cross section means that the difference between the maximum value and the minimum value of Vickers hardness in the steel pipe is 80 HV or less.
- excellent ductility of the outer surface of the corner means that the uniform elongation at the t / 4 position from the outer surface of the corner portion is 0.80 times or more the uniform elongation at the t / 4 position from the outer surface of the flat plate portion. Point to that.
- excellent toughness of the outer surface of the corner means that the Charpy absorption energy of the corner at 0 ° C. is 70 J or more.
- the flatness of the flat plate portion is represented by the maximum bulge amount and the maximum dent amount with respect to a straight line passing through two points at both ends in the circumferential direction on the same side of the outer surface of the flat plate portion. However, it means that it is 2.5 mm or less (see FIG. 10).
- the present inventors have reduced the variation in hardness (particularly, the variation in hardness between the flat plate portion and the corner portion) in the peripheral cross section of the square steel pipe, and the corner portion. It has been found that in order to sufficiently secure the ductility and toughness of the outer surface, the radius of curvature on the outside of the corner of the square steel pipe should be more than 3.0 times the average plate thickness. It was also found that in order to make the flat plate portion sufficiently flat, the radius of curvature on the outside of the corner portion of the roll-formed square steel pipe should be 4.0 times or less the average plate thickness.
- the radius of curvature on the outside of the corner is the plate thickness. It is possible to manufacture a square steel pipe that is more than 0 times and 4.0 times or less, reduces the variation in hardness within the peripheral cross section to a desired level, improves the ductility and toughness of the outer surface of the corner, and makes the flat plate part sufficiently. We found that it could be flattened.
- the present invention has been completed based on the above findings, and its gist structure is as follows.
- a plurality of flat plate portions and corner portions are alternately formed in the circumferential direction of the pipe. Further welds extending in the pipe axis direction are formed, The width of the melt-solidified portion in the welded portion in the pipe circumferential direction is 1.0 ⁇ m or more and 1000 ⁇ m or less.
- C IN Perimeter (mm) of the electric resistance pipe on the entrance side of the square forming stand of the first stage
- C OUT Perimeter (mm) of the square steel pipe on the exit side of the square forming stand in the final stage
- t Average plate thickness (mm) after square forming
- H Average side length (mm) after square molding
- the radius of curvature may be the average radius of curvature or the radius of curvature at any place. However, from the viewpoint of ensuring a better effect, it is preferable to set the radius of curvature at an arbitrary position.
- the average plate thickness t is obtained from the following formula (2).
- t (t1 + t2 + t3) / 3 ... Equation (2)
- t1, t2 plate thickness (mm), t3 at the center of each of the two flat plate portions adjacent to each other with the corner portion sandwiched by the flat plate portion including the welded portion (electrically sewn welded portion).
- H (H1 + H2) / 2 ... Equation (3)
- H (H1 + H2) / 2 ... Equation (3)
- H1 vertical cross section in the pipe axis direction
- H2 Flat plate portions adjacent to the flat plate portions having a side length of H1 with a corner portion in between.
- the present invention it is possible to provide a square steel pipe having a small variation in hardness in the peripheral cross section, excellent ductility and toughness of the outer surface of the corner portion, and having a flat flat plate portion, a method for manufacturing the same, and a building structure. It becomes.
- This makes it possible to manufacture a cold roll-formed square steel pipe having a small difference in strength in the peripheral cross section and having excellent ductility and toughness.
- the building structure using the square steel pipe of the present invention as a column material exhibits more excellent seismic performance as compared with the building structure using the conventional cold-formed square steel pipe.
- FIG. 1 is a schematic view showing a cross section perpendicular to the pipe axis direction of the square steel pipe of the present invention.
- FIG. 2 is a schematic view showing an example of an electric resistance pipe manufacturing facility.
- FIG. 3 is a schematic view for explaining a melt-solidified portion in a welded portion.
- FIG. 4 is a schematic view showing a molding process of the square steel pipe of the present invention.
- FIG. 5 is a schematic view showing an example of the building structure of the present invention.
- FIG. 6 is a schematic view showing the sampling positions of the tensile test pieces of the flat plate portion and the corner portion, respectively.
- FIG. 7 is a schematic view showing a detailed sampling position of the tensile test piece at the corner.
- FIG. 1 is a schematic view showing a cross section perpendicular to the pipe axis direction of the square steel pipe of the present invention.
- FIG. 2 is a schematic view showing an example of an electric resistance pipe manufacturing facility.
- FIG. 3 is
- FIG. 8 is a schematic view showing a collection position of the Charpy test piece at the corner.
- FIG. 9 is a schematic view showing a detailed collection position of the Charpy test piece at the corner.
- FIG. 10 is a schematic diagram for explaining a method of measuring flatness.
- FIG. 11 is a schematic view showing the sampling positions of the tensile test pieces at the position of t / 4 from the outer surface of the flat plate portion and the position of t / 4 from the outer surface of the corner portion.
- FIG. 12 is a schematic view showing a detailed sampling position of the tensile test piece at a position t / 4 from the outer surface of the corner.
- FIG. 1 is a schematic view showing a cross section of the square steel pipe 10 of the present invention perpendicular to the pipe axis direction.
- a plurality of flat plate portions 11 and square portions 12 are alternately formed in the circumferential direction of the pipe.
- the square steel pipe 10 has a square portion 12, a flat plate portion 11, a square portion 12, a flat plate portion 11, a square portion 12, a flat plate portion 11, a square portion 12, and a flat plate portion 11 in this order.
- the square steel pipe 10 of the present invention can be a roll-formed square steel pipe obtained from an electrosewn steel pipe, and also has a welded portion (electrosewn welded portion) 13 formed on a flat plate portion 11 and extending in the pipe axial direction. ..
- the square steel pipe 10 of the present invention has a radius of curvature on the outside of the corner portion of more than 3.0 times and 4.0 times or less of the average plate thickness t.
- the radius of curvature on the outside of the corner portion passes through the intersection P of two straight lines L1 and L2 including the outer surfaces of the flat plate portions 11 on both sides adjacent to the corner portion 12, and becomes L1 or L2.
- the radius of curvature at the intersection of the straight line L forming 45 ° and the outside of the corner.
- the radius of curvature referred to in the present invention may be the average radius of curvature or the radius of curvature at any place. However, from the viewpoint of ensuring a better effect, it is preferable to set the radius of curvature at an arbitrary position.
- the measurement of the radius of curvature consists of the connection points (A, A') of the flat plate portion 11 and the corner portion 12 and the outer surface of the corner portion, and in a sector having a central angle of 90 ° whose center exists on the L, the angle with the L This is performed within a central angle of 65 ° centered on the intersection of the outer surfaces.
- a method for measuring the radius of curvature for example, there is a method of measuring the radius of curvature from a radial gauge that matches well with the outer surface of the corner in the above range of the central angle of 65 °, but these are not limited to these.
- the corner portion is largely work-hardened, and has higher strength and lower ductility and toughness than the flat plate portion.
- the radius of curvature on the outside of the corner portion exceeds 4.0 times the average plate thickness t, the flatness of the flat plate portion becomes insufficient, and the desired square steel pipe is not obtained.
- the peripheral cross-sectional area becomes small, and sufficient member strength cannot be obtained.
- the radius of curvature on the outside of the corner is set to be more than 3.0 times and 4.0 times or less of the average plate thickness t.
- the radius of curvature on the outside of the corner portion is 3.1 times or more and 3.9 times or less of the average plate thickness t, and more preferably 3.2 times or more and 3.8 times or less.
- the square steel pipe 10 is obtained from an electrosewn steel pipe. Therefore, the welded portion 13 is an electric sewing welded portion.
- the width of the melt-solidified portion of the electrosewn welded portion in the tube circumferential direction is 1.0 ⁇ m or more and 1000 ⁇ m or less over the entire thickness of the pipe.
- the ratio (E2 / E1) of the uniform elongation E1 at the position of t / 4 from the outer surface of the flat plate portion and the uniform elongation E2 at the position of t / 4 from the outer surface of the corner portion is 0.80 times or more. Is preferable. More preferably, E2 / E1 is 0.83 times or more, and even more preferably 0.85 times or more. Further, preferably, E2 / E1 is 1.00 times or less.
- t / H can be set to more than 0.030 as the relationship between the average plate thickness t (mm) of the square steel pipe 10 and the average side length H.
- the larger the ratio (t / H) of the average plate thickness t and the average side length H the larger the amount of work hardening at the corners. Therefore, in a square steel pipe having a large ratio (t / H), the difference in strength, ductility and toughness in the peripheral cross section tends to be large.
- the radius of curvature on the outside of the corner is more than 3.0 times and 4.0 times or less of the average plate thickness, even if t / H exceeds 0.030, the strength difference in the peripheral cross section is increased. It is small and has excellent ductility and toughness.
- the average plate thickness t is obtained from the following equation (2).
- t (t1 + t2 + t3) / 3 ... Equation (2)
- t1, t2 plate thickness (plate thickness) at the center of each of the two flat plate portions 11 adjacent to the flat plate portion 11 including the welded portion (electrically sewn welded portion) 13 with the corner portion 12 in between.
- t3 The plate thickness (mm) at the center of the flat plate portion 11 facing the flat plate portion 11 including the welded portion (electrically sewn welded portion) 13 in the pipe circumferential direction.
- H (H1 + H2) / 2 ... Equation (3)
- H1 the vertical side length (mm) in FIG. 1
- H2 the horizontal side length (mm) in FIG. 1, that is, H is a corner portion in the vertical cross section in the pipe axis direction.
- the side lengths H1 and H2 including the corners 12 on both sides of each of the two flat plate portions 11 adjacent to each other with the 12 in between are added and divided by two.
- H1> H2 that is, the side length H2 in the vertical cross section in the pipe axis direction including the flat plate portion 11 on which the welded portion 13 is formed is the side of the flat plate portion 11 adjacent to the flat plate portion 11.
- H1 H2 or H1 ⁇ H2 may be used.
- the difference between the maximum value and the minimum value of Vickers hardness in the steel pipe is preferably 80 HV or less.
- the position measured at each of the flat plate portion 11, the corner portion 12, and the welded portion (electric sewing welded portion) 13 is 1 mm in the thickness direction from the inner surface of the pipe, 1 mm in the thickness direction from the outer surface of the pipe, and the center of the plate thickness.
- the difference between the maximum value and the minimum value of Vickers hardness at the position is preferably 80 HV or less.
- the above Vickers hardness test can be carried out in accordance with JIS Z 2244 with a test force of 98N (10 kgf).
- the average plate thickness t is 20 mm or more and 40 mm or less
- the yield strength of the flat plate portion 11 is 295 MPa or more
- the tensile strength of the flat plate portion 11 is 400 MPa or more
- the square portion 12 It is preferable that the yield ratio is 90% or less and the Charpy absorption energy of the corner 12 at 0 ° C. is 70 J or more.
- the yield strength, tensile strength, yield ratio, and uniform elongation can be obtained by carrying out a tensile test in accordance with JIS Z 2241.
- the Charpy absorbed energy is obtained by performing a Charpy impact test at a test temperature of 0 ° C. using a V-notch standard test piece in accordance with JIS Z 2242.
- the composition of the square steel pipe 10 of the present invention preferably has a Ceq defined by the formula (4) of 0.15% or more and 0.50% or less in order to ensure mechanical properties and weldability. Further, it is preferable that the Pcm defined by the formula (5) is 0.30% or less.
- the component compositions of the various elements in the formulas (4) and (5) are all mass%. Hereinafter, unless otherwise specified, "%" indicating the component composition is "mass%”.
- Ceq C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 ... Equation (4)
- C, Mn, Si, Ni, Cr, Mo, and V are the contents (mass%) of each element. (However, the element not contained is 0 (zero)%.)
- Pcm C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5B ... Equation (5)
- C, Si, Mn, Cu, Ni, Cr, Mo, V, and B are the contents (mass%) of each element.
- Ceq in the formula (4) is a carbon equivalent, and is an index of the hardness of the welded portion (electrically sewn welded portion) 13 and the heat-affected zone. If Ceq is less than 0.15%, the strength required as a pillar material of a building structure may not be obtained. Further, if Ceq exceeds 0.50%, the welded portion 13 and the heat-affected zone may be excessively hardened, and the variation in peripheral cross-sectional strength may become large. Therefore, in the present invention, Ceq is preferably 0.15% or more and 0.50% or less. Further, more preferably, Ceq is 0.20% or more, and even more preferably 0.25% or more. Further, more preferably, Ceq is 0.45% or less, and even more preferably 0.40% or less.
- the Pcm in the formula (5) is susceptible to weld cracking, and if Pcm exceeds 0.30%, low temperature cracking is likely to occur in the welded portion 13 and the heat-affected zone. Therefore, in the present invention, the Pcm is preferably 0.30% or less. Further, more preferably, Pcm is 0.10% or more, and even more preferably 0.15% or more. Further, the Pcm is more preferably 0.28% or less, and further preferably 0.25% or less.
- the square steel pipe 10 of the present invention has a mass% of C: 0.04 to 0.45% and Si: 0.02 to 0 in order to ensure mechanical properties and weldability. .50%, Mn: 0.40 to 2.5%, P: 0.10% or less, S: 0.050% or less, Al: 0.005 to 0.10%, N: 0.010% or less, Ti: may contain 0.005 to 0.15% and may have a component composition consisting of the balance Fe and unavoidable impurities. Further, the square steel pipe 10 of the present invention further has Nb: 0.005 to 0.15%, V: 0.005 to 0.15%, Cr: 0.02 to 1.0%, Mo in mass%. It may contain one or more selected from: 0.02 to 1.0%, Cu: 0.02 to 1.0%, and Ni: 0.02 to 1.0%.
- a steel plate is roll-formed, then the roll-formed steel plate is electrosewn and welded to form an electrosewn steel pipe, and then the electrosewn steel pipe is formed by a sizing stand and then by a square forming stand. It is a method of manufacturing a square steel pipe by square forming, and controls the gap of the sizing stand immediately before the square forming based on the gap of the square forming stand so as to satisfy the following formula (1).
- Equation (1) C IN : Perimeter (mm) of the electric resistance pipe on the entrance side of the square forming stand of the first stage, C OUT : Perimeter (mm) of the square steel pipe on the exit side of the square forming stand in the final stage, t: Average plate thickness (mm) after square forming, H: The average side length (mm) after square molding.
- the average plate thickness t is obtained from the following formula (2).
- t (t1 + t2 + t3) / 3 ... Equation (2)
- t1, t2 plate thickness (plate thickness) at the center of each of the two flat plate portions 11 adjacent to the flat plate portion 11 including the welded portion (electrically sewn welded portion) 13 with the corner portion 12 in between.
- t3 The plate thickness (mm) at the center of the flat plate portion 11 facing the flat plate portion 11 including the welded portion (electrically sewn welded portion) 13 in the pipe circumferential direction.
- H (H1 + H2) / 2 ... Equation (3)
- H1 the vertical side length (mm) in FIG. 1
- H2 the horizontal side length (mm) in FIG. 1, that is, H is a corner portion in the vertical cross section in the pipe axis direction.
- the side lengths H1 and H2 including the corners 12 on both sides of each of the two flat plate portions 11 adjacent to each other with the 12 in between are added and divided by two.
- the first-stage square molding stand and the final-stage square molding stand are the same square molding stand.
- FIG. 2 is a schematic view showing an example of an electric resistance pipe manufacturing facility.
- a steel plate 1 having the above-mentioned component composition wound around a coil (hereinafter, also referred to as a steel strip 1) is dispensed and corrected by a leveler 2, and a cage roll group 3 composed of a plurality of rolls is used.
- finish molding is performed with a finpass roll group 4 composed of a plurality of rolls.
- the open pipe may have a cylindrical shape obtained by cold roll molding.
- a pair of butt portions facing each other in the circumferential direction of the steel strip 1 are electrically resistance welded by a welding machine 6 while being pressure-welded with a squeeze roll 5 to form an electrosewn steel pipe 7.
- the manufacturing equipment for the electrosewn steel pipe 7 is not limited to the pipe making process as shown in FIG.
- the butt portion is heated, melted, pressure-welded and solidified to complete the joining.
- one welded portion (electrically sewn welded portion) 13 is extended in the pipe axis direction.
- the amount of upset by the squeeze roll 5 is preferably 20% or more and 100% or less of the plate thickness of the electrosewn steel pipe 7.
- the amount of upset is less than 20% of the plate thickness, the discharge of molten steel becomes insufficient and the toughness of the welded portion deteriorates.
- the amount of upset is more than 100% of the plate thickness, the squeeze roll load becomes large, and the work hardening amount of the welded portion (electrically sewn welded portion) 13 becomes large and the hardness becomes excessively high.
- the total circumference of the steel pipe is 0.30% or more in order to satisfy the preferable roundness and the residual stress in the pipe axial direction.
- the diameter of the steel pipe may be reduced so as to decrease in proportion. However, if the diameter is reduced so that the circumference of the steel pipe decreases at a rate of more than 2.0% in total, the amount of bending in the pipe axis direction when passing through the roll becomes large, and the residual stress in the pipe axis direction after the diameter reduction increases. On the contrary, it rises. Therefore, it is preferable to reduce the diameter so that the circumference of the steel pipe decreases at a rate of 0.30% or more and 2.0% or less.
- the sizing step in order to minimize the bending amount in the pipe axis direction when passing through the roll and suppress the generation of residual stress in the pipe axis direction, it is preferable to perform multi-step diameter reduction by a plurality of stands.
- the diameter reduction in the stand is preferably performed so that the circumference of the steel pipe is reduced at a rate of 1.0% or less.
- Whether or not the square steel pipe 10 was obtained from the electric resistance pipe 7 is determined by cutting the square steel pipe 10 perpendicularly to the pipe axis direction, polishing the cut surface including the welded portion (electric stitch welded portion) 13, and then corroding it with an optical microscope. It can be judged by observing. If the width of the melt-solidified portion of the welded portion (electrically sewn welded portion) 13 in the pipe circumferential direction is 1.0 ⁇ m or more and 1000 ⁇ m or less over the entire pipe thickness, the electric resistance steel pipe 7 is used.
- FIG. 3 is a diagram schematically showing a melt-solidified portion in the welded portion 13.
- the melt-solidified portion can be visually recognized as a region 16 having a structure shape and contrast different from those of the base material portion 14 and the heat-affected zone 15 in FIG.
- the melt-solidified portion 16 of the electrosewn steel pipe of carbon steel and low alloy steel can be identified as a region observed white by an optical microscope in the cross section corroded by nital.
- the melt-solidified portion 16 of the UOE steel pipe of carbon steel and low alloy steel can be identified as a region containing a cell-like or dendrite-like solidified structure by an optical microscope in the above cross section corroded by nital.
- FIG. 4 is a schematic view showing a molding process of the square steel pipe 10 of the present invention.
- the electrosewn steel pipe 7 is reduced in diameter by a sizing roll group (sizing stand) 8 composed of a plurality of rolls arranged vertically and horizontally, and then a square forming roll composed of the plurality of rolls.
- the group (square forming stand) 9 sequentially forms a shape such as R1, R2, and R3 to form a square steel pipe 10.
- the roll of the square forming stand 9 is a hole-shaped roll having a caliber curvature, and the radius of curvature of the caliber increases as the stand becomes a latter stage, forming the flat plate portion 11 and the square portion 12 of the square steel pipe 10.
- the number of stands of the sizing roll group 8 and the square forming roll group 9 is not particularly limited. Further, the caliber curvature of the sizing roll group 8 or the square forming roll group 9 is preferably one condition.
- the circumference of the electric resistance pipe 7 immediately before square forming (the circumference (mm) of the electric resistance pipe 7 on the entrance side of the square forming stand of the first stage, hereinafter referred to as "CIN ") and the angle.
- the ratio (C IN / C OUT ) of the circumference of the square steel pipe 10 immediately after molding (the circumference (mm) of the steel pipe on the exit side of the square molding stand in the final stage, hereinafter referred to as “C OUT ”), and after square molding.
- the ratio (t / H) of the average plate thickness t to the average side length H after square forming satisfies the formula (1).
- the corner forming is completed with almost no contact between the rolls. That is, in square forming, the corner portion 12 is formed by projecting by free deformation. At this time, the higher the rigidity of the corner portion 12 and the smaller the amount of drawing in the circumferential direction, the smaller the bending deformation amount of the corner portion 12, and the larger the radius of curvature on the outside of the corner portion. On the other hand, the lower the rigidity of the corner portion 12 and the larger the circumferential diaphragm, the larger the bending deformation of the corner portion 12 and the smaller the radius of curvature on the outside of the corner portion 12.
- the rigidity of the corner portion 12 against bending deformation increases as the ratio (t / H) of the average plate thickness t to the average side length H increases.
- the circumferential drawing amount in square forming is determined by the peripheral length ratio (C IN / C OUT ), and the larger this is, the larger the circumferential drawing amount is.
- (C IN / C OUT ) is 0.33 ⁇ t / H + 0.99 or more, and more preferably 0.35 ⁇ t / H + 0.99 or more. Further, (C IN / C OUT ) is preferably 0.47 ⁇ t / H + 0.99 or less, and more preferably 0.45 ⁇ t / H + 0.99 or less.
- C IN is the peripheral length (the length of the outer circumference in the peripheral direction of the pipe) (mm) of the electric pipe 7 on the entrance side of the square forming stand of the first stage.
- the pipe making direction is the positive direction of the X axis
- the X coordinate of any one of the sizing stands immediately before square forming is Xa (m)
- any one of the first stage square forming stands is Xb (m)
- it can be obtained by measuring the outer peripheral length of the peripheral cross section of the pipe in the plane X (Xa + Xb) / 2 (m) perpendicular to the X axis with a winding scale (Fig.). 4).
- C OUT is the peripheral length (the length of the outer circumference in the peripheral direction of the pipe) (mm) of the square steel pipe 10 on the exit side of the square forming stand in the final stage.
- the X coordinate of the rotation axis of any one of the square forming stands in the final stage of the roll group is Xc (m)
- C IN and C OUT are controlled by controlling the gap between the recesses of the caliber roll.
- the difference ⁇ g between the maximum gap between the recesses of the sizing stand immediately before square molding (hereinafter, also referred to as “sizing stand gap”) and the maximum gap between the recesses of the square molding stand (hereinafter, also referred to as “square molding stand gap”). It is preferable to adjust the gap of the sizing stand immediately before the square forming so that the value G ( ⁇ g / (t / H)) divided by (t / H) is 70 or more and 180 or less.
- (C IN / C OUT ) in equation (1) is smaller than the value on the left side, and when G is more than 180, (C IN / C OUT ) in equation (1) is greater than or equal to the value on the right side. It becomes.
- the gap of the sizing stand immediately before the square forming and the gap of the other sizing stands may be the same.
- the gap of the square forming stand is the gap of the first stage of the square forming stand. Further, the gaps between the first stage and the other square forming stands may all be the same.
- FIG. 5 is a schematic view showing an example of the building structure 100 of the present invention.
- the diaphragm 17 and the square steel pipe 10 are welded together, and the square steel pipe 10 is used as a column material.
- the building structure 100 is formed by a girder 18, a girder 19, and a stud 20, and may be formed by other known members.
- the square steel pipe 10 has a flat flat plate portion 11 having a small variation in hardness in the peripheral cross section. Therefore, the building structure 100 of the present invention using the square steel pipe 10 as a pillar material exhibits excellent seismic performance.
- a hot-rolled steel sheet having the composition shown in Table 1 is continuously formed into an open pipe having an elliptical cross section by a cage roll group and a finpath roll group, and then the opposite end faces of the open pipe are melted by high-frequency induction heating or high-frequency resistance heating. It was heated above and pressure-welded with a squeeze roll to form a raw steel pipe.
- the obtained electrosewn steel pipe is formed into a cylindrical shape with a 2-stand (2-stage) sizing roll group, and then square-formed with a 4-stand (4 stage) square forming roll group, as shown in Table 2.
- Square steel pipes having a substantially rectangular shape in a vertical cross-sectional view in the axial direction were obtained.
- the average plate thickness t was obtained from the following formula (2).
- t (t1 + t2 + t3) / 3 ... Equation (2)
- t1, t2 plate thickness (mm), t3 at the center of each of the two flat plate portions adjacent to each other with the corner portion sandwiched by the flat plate portion including the welded portion (electrically sewn welded portion).
- H (H1 + H2) / 2 ... Equation (3)
- H2 the side length of the side including the flat plate portion on which the electric sewing welded portion is formed and the corners on both sides in the vertical cross section in the pipe axis direction
- H1 the flat plate portion having the side length of H2. It is the side length (mm) of the side including the flat plate portion adjacent to each other across the corner portion and the corner portions on both sides.
- the square steel pipe is cut perpendicularly to the pipe axis direction, the cut surface including the electric stitch welded portion is polished and then nital corroded, and by observing with an optical microscope, the melt-solidified portion of the electric stitch welded portion is formed. It was also confirmed that the width of the pipe in the circumferential direction was 1.0 ⁇ m or more and 1000 ⁇ m or less over the entire thickness of the pipe. The melt-solidified portion was identified as a region observed white with an optical microscope in the cross section corroded by nital.
- the pipe forming direction is the positive direction of the X axis, and the rotation axis of any one of the sizing stands immediately before the square forming.
- the X coordinate is Xa (m)
- the X coordinate of any one of the rotation axes of the first stage square forming stand is Xb (m)
- the plane X (Xa + Xb) / 2
- the outer peripheral length of the peripheral cross section of the pipe in m) was measured with a winding scale and used as the peripheral length C IN (mm) of the electrosewn steel pipe (see FIG. 4 again).
- the radii of curvature of the outer surfaces (outside the corners) of the four corners were measured at 10 arbitrary positions in the pipe axis direction of the obtained square steel pipe, and the maximum value Rmax and the minimum value Rmin of the total of 40 points were measured. I asked for each.
- a radial gauge was used to measure the radius of curvature on the outside of the corner.
- the intersection of the straight line L forming 45 ° with L1 or L2 and the outside of the corner through the intersection P of the two straight lines L1 and L2 including the outer surfaces of the flat plates on both sides adjacent to the corner.
- the radius of curvature in was measured as the radius of curvature outside the corner (see FIG. 1 again).
- the measurement of the radius of curvature consists of the connection points (A, A') of the flat plate portion and the corner portion and the outer surface of the corner portion, and in a sector having a central angle of 90 ° whose center exists on the above L, the above L
- the measurement was performed in a range of a central angle of 65 ° centered on the intersection of the outer surfaces of the corners, and the radius of curvature was measured from a radial gauge that closely coincided with the outer surface of the corners in the range of 65 ° of the central angle.
- the Vickers hardness of the flat plate portion, the corner portion and the welded portion is 1 mm in the thickness direction from the inner and outer surfaces and the center of the plate thickness, respectively.
- the maximum value HVmax and the minimum value HVmin were determined respectively.
- the above Vickers hardness test was carried out in accordance with JIS Z 2244 with a test force of 98 N (10 kgf). The hardness of the flat plate portion was measured at the flat plate portion adjacent to the flat plate portion including the electric sewing welded portion, and the hardness of the corner portion was measured at the corner portion adjacent to the flat plate portion including the electric sewing welded portion.
- FIG. 6 is a schematic view showing the sampling positions of the tensile test pieces at the flat plate portion and the corner portion, respectively.
- FIG. 7 is a schematic view showing a detailed sampling position of the tensile test piece at the corner.
- FIG. 11 is a schematic view showing the sampling positions of the tensile test pieces at the position of t / 4 from the outer surface of the flat plate portion and the position of t / 4 from the outer surface of the corner portion.
- FIG. 12 is a schematic view showing a detailed sampling position of the tensile test piece at a position t / 4 from the outer surface of the corner.
- JIS No. 5 tensile test pieces and JIS No. 12B tensile test pieces were taken from the flat plate portion and the corner portion of the square steel pipe so that the tensile direction was parallel to the pipe axis direction, respectively. More specifically, as shown in FIG. 7, the tensile test piece at the corner portion passes through an intersection in which the outer surfaces of the flat plate portions on both sides adjacent to the corner portion are extended, and 45 ° with each of the outer surfaces of the flat plate portion. Collected from the eggplant line.
- JIS No. 5 tensile test pieces and JIS No. 12B tensile test pieces shown by broken lines were collected from the flat plate portion and the corner portion of the square steel pipe so that the tensile direction was parallel to the pipe axis direction, respectively. Each of them was ground so that the thickness was 5 mm and the thickness center was at the t / 4 position of the plate thickness t from the outer surface of the pipe, and a tensile test piece was taken. More specifically, as shown in FIG. 12, the tensile test piece at the corner portion passes through an intersection in which the outer surfaces of the flat plate portions on both sides adjacent to the corner portion are extended, and 45 ° with each of the outer surfaces of the flat plate portion. Collected from the eggplant line.
- a tensile test was carried out in accordance with the provisions of JIS Z 2241, and the yield strength YS, tensile strength TS, and uniform elongation (flat plate: E1, corner: E2) were measured, and (yield strength) / ( The yield ratio defined by (tensile strength) was calculated.
- the uniform elongation is the value of the total elongation at the maximum load.
- the tensile test piece of the flat plate portion was taken from the position of the center of the width in the flat plate portion next to the flat plate portion including the electric resistance welded portion of the square steel pipe.
- Tensile test pieces at the corners were taken from the corners adjacent to the flat plate including the electric stitch welded part. The number of test pieces was two each, and the average values thereof were calculated to determine the yield strength YS, tensile strength TS, yield ratio, and uniform elongation.
- FIG. 8 is a schematic view showing the collection position of the Charpy test piece at the corner.
- FIG. 9 is a schematic view showing a detailed collection position of the Charpy test piece at the corner.
- JIS Charpy impact test
- FIGS. 8 and 9 JIS was taken so that the longitudinal direction of the test piece was parallel to the axial direction of the pipe at the t / 4 position of the plate thickness t from the outer surface of the square steel pipe.
- a V-notch standard test piece conforming to the provisions of Z 2242 was used.
- a Charpy impact test was carried out at a test temperature of 0 ° C., and the absorbed energy (J) was determined. The number of test pieces was 3 each, and the average value of them was calculated to obtain the absorbed energy (J).
- FIG. 10 is a schematic diagram for explaining a method of measuring flatness.
- the flatness was measured at 10 arbitrary positions in the pipe axis direction of the square steel pipe, and at 40 points in total, with 4 flat plate portions as measurement targets.
- the maximum bulge amount and the maximum dent amount with respect to the straight line passing through the two points at both ends in the circumferential direction of each flat plate portion are measured, and the maximum absolute value of the maximum bulge amount and the maximum dent amount at each measurement point is measured.
- the value was flatness.
- the bulge amount was set to a positive value
- the dent amount was set to a negative value
- the bulge amount or dent amount value was set to 0.
- the square steel pipes of the examples of the present invention all have a circumference ratio (C IN / C OUT ) within the range of Eq. (1), and the radius of curvature (Rmin, Rmax) on the outside of the corner is 3.0 times the plate thickness. It is super 4.0 times or less, and the uniform elongation at the position of t / 4 from the outer surface of the corner portion is 0.80 times or more of the uniform elongation at the position of t / 4 from the outer surface of the flat plate portion, and the uniform elongation of the corner portion and the flat plate portion.
- the difference in hardness was 80 HV or less between the maximum and minimum values of Vickers hardness at the position 1 mm from the inner and outer surfaces and the position at the center of the plate thickness. Further, the square steel pipe of the example of the present invention had a flatness of 2.5 mm or less.
- the radius of curvature on the outside of the corner is set to be more than 3.0 times and 4.0 times or less of the average plate thickness. It is possible to provide a square steel pipe having a flat flat plate portion having a small variation in hardness in a peripheral cross section, excellent ductility and toughness on the outer surface of the corner portion, a method for manufacturing the same, and a building structure having excellent seismic performance. ..
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Abstract
Description
また、ロール成形角形鋼管を柱材として使用した建築構造物の耐震性能をより向上させるためにも、ロール成形角形鋼管の延性や靭性が部分的に低くなることを抑制することで、柱材としての変形性能や耐衝撃性能をより向上させることが希求されていた。
特に、角形鋼管は、地震等の外力で変形する際に角部外面に大きなひずみが生じるため、角部外面の延性および靭性を向上させることが必要であった。 For the above reasons, the roll-formed square steel pipe has a large difference in strength, ductility, and toughness in the peripheral cross section, which causes problems such as complicated selection of welding material, welding method, and building structure design in welding with the diaphragm. Was there.
In addition, in order to further improve the seismic performance of building structures that use roll-formed square steel pipes as columns, by suppressing the ductility and toughness of roll-formed square steel pipes from becoming partially low, as columns. It has been sought to further improve the deformation performance and impact resistance performance of the steel pipe.
In particular, since a square steel pipe causes a large strain on the outer surface of the corner when deformed by an external force such as an earthquake, it is necessary to improve the ductility and toughness of the outer surface of the corner.
具体的に、特許文献5では、鋼管を、3段または4段の角成形ロールで、かつ最終段ロールの圧下率を一定で角管成形する際、鋼管の肉厚/外径比が大きくなるにつれて、最終段のロールカリバーを小さくして(凸型から凹型にして)成形する角鋼管の成形方法の技術が開示されている。
また、特許文献6では、円筒状の素管を角管にロール成形する際、素管の外径をD、素管の肉厚をt、最大カリバー高さをHとするとき、Q=(D-H)/(D-t)×100で定義される設定押込み率Qを12~23%の範囲に維持して素管を矩形断面形状に成形する第1段の成形工程と、矩形断面形状に成形された素管を目標形状に成形する第2段以降の成形工程を経る構造用角管の製造方法の技術が開示されている。 By the way, in roll-formed square steel pipes, it is also required to establish a technique for improving shape characteristics, particularly a technique for making a flat plate portion sufficiently flat. In this regard,
Specifically, in
Further, in
なお、本発明において、周断面内の硬さのばらつきが小さいとは、鋼管内でビッカース硬さの最大値と最小値の差が80HV以下であることを指す。
また、本発明において、角部外面の延性に優れるとは、角部外面からt/4の位置における均一伸びが、平板部外面からt/4の位置における均一伸びの0.80倍以上であることを指す。
また、本発明において、角部外面の靭性に優れるとは、0℃における角部のシャルピー吸収エネルギーが、70J以上であることを指す。
また、本発明において、平板部が平坦であるとは、周断面において、平板部外面の同一辺上において周方向両端の2点を通る直線に対する最大膨らみ量及び最大凹み量で表される平坦度が、2.5mm以下であることを指す(図10参照)。 The present invention has been made in view of the above circumstances, and is a square steel pipe having a small variation in hardness in the peripheral cross section, excellent ductility and toughness on the outer surface of the corner, and having a flat flat plate portion, and a method for manufacturing the same. In addition, it aims to provide a building structure having excellent seismic performance.
In the present invention, the small variation in hardness in the peripheral cross section means that the difference between the maximum value and the minimum value of Vickers hardness in the steel pipe is 80 HV or less.
Further, in the present invention, excellent ductility of the outer surface of the corner means that the uniform elongation at the t / 4 position from the outer surface of the corner portion is 0.80 times or more the uniform elongation at the t / 4 position from the outer surface of the flat plate portion. Point to that.
Further, in the present invention, excellent toughness of the outer surface of the corner means that the Charpy absorption energy of the corner at 0 ° C. is 70 J or more.
Further, in the present invention, the flatness of the flat plate portion is represented by the maximum bulge amount and the maximum dent amount with respect to a straight line passing through two points at both ends in the circumferential direction on the same side of the outer surface of the flat plate portion. However, it means that it is 2.5 mm or less (see FIG. 10).
また、平板部を十分に平坦にするためには、ロール成形角形鋼管の角部外側の曲率半径を平均板厚の4.0倍以下とすればよいことも見出した。
そして、角成形スタンド出側における角形鋼管の周長に対して角成形スタンド入側における電縫鋼管の周長を適切な範囲に管理することで、角部外側の曲率半径が板厚の3.0倍超4.0倍以下となる角形鋼管を製造でき、周断面内の硬さのばらつきを所望のレベルにまで小さくすると共に、角部外面の延性および靭性を良好にし、平板部を十分に平坦にすることができることを見出した。 As a result of diligent studies to solve the above problems, the present inventors have reduced the variation in hardness (particularly, the variation in hardness between the flat plate portion and the corner portion) in the peripheral cross section of the square steel pipe, and the corner portion. It has been found that in order to sufficiently secure the ductility and toughness of the outer surface, the radius of curvature on the outside of the corner of the square steel pipe should be more than 3.0 times the average plate thickness.
It was also found that in order to make the flat plate portion sufficiently flat, the radius of curvature on the outside of the corner portion of the roll-formed square steel pipe should be 4.0 times or less the average plate thickness.
Then, by managing the circumference of the electric resistance pipe on the entrance side of the square forming stand within an appropriate range with respect to the circumference length of the square steel pipe on the exit side of the square forming stand, the radius of curvature on the outside of the corner is the plate thickness. It is possible to manufacture a square steel pipe that is more than 0 times and 4.0 times or less, reduces the variation in hardness within the peripheral cross section to a desired level, improves the ductility and toughness of the outer surface of the corner, and makes the flat plate part sufficiently. We found that it could be flattened.
[1]管周方向に平板部と角部とが交互に夫々複数形成されており、
管軸方向に延びる溶接部が更に形成されており、
前記溶接部における溶融凝固部の管周方向の幅が1.0μm以上1000μm以下であり、
前記角部外側の曲率半径が平均板厚tの3.0倍超4.0倍以下である角形鋼管。
[2]前記平均板厚tが平均辺長Hの0.030倍超である前記[1]に記載の角形鋼管。
[3]鋼管内でビッカース硬さの最大値と最小値の差が80HV以下である前記[1]又は[2]に記載の角形鋼管。
[4]前記平均板厚tが20mm以上40mm以下であり、
前記平板部の降伏強度が295MPa以上であり、
前記平板部の引張強度が400MPa以上であり、
前記角部の降伏比が90%以下であり、
前記角部の0℃におけるシャルピー吸収エネルギーが70J以上である前記[1]~[3]のいずれかに記載の角形鋼管。
[5]前記角部外面からt/4の位置における均一伸びが、平板部外面からt/4の位置における均一伸びの0.80倍以上である前記[1]~[4]のいずれかに記載の角形鋼管。
[6]鋼板をロール成形し、次いでロール成形した前記鋼板を電縫溶接して電縫鋼管とした後、前記電縫鋼管をサイジングスタンドによって成形し、次いで角成形スタンドによって角成形して角形鋼管を製造する方法であって、
以下の式(1)を満たすように、前記角成形スタンドのギャップに基づいて角成形直前の前記サイジングスタンドのギャップを制御する角形鋼管の製造方法。
0.30×t/H+0.99≦CIN/COUT<0.50×t/H+0.99・・・式(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電縫鋼管の周長(mm)、
COUT:最終段の角成形スタンド出側における角形鋼管の周長(mm)、
t:角成形後の平均板厚(mm)、
H:角成形後の平均辺長(mm)、
である。
(但し、1段の角成形スタンドにより前記角成形を行う場合には、前記第一段目の角成形スタンドと前記最終段の角成形スタンドとは、同一の角成形スタンドとする。)
[7]前記平均板厚tが20mm以上40mm以下である前記[6]に記載の角形鋼管の製造方法。
[8]前記[1]~[5]のいずれかに記載の角形鋼管が、柱材として使用されている建築構造物。 The present invention has been completed based on the above findings, and its gist structure is as follows.
[1] A plurality of flat plate portions and corner portions are alternately formed in the circumferential direction of the pipe.
Further welds extending in the pipe axis direction are formed,
The width of the melt-solidified portion in the welded portion in the pipe circumferential direction is 1.0 μm or more and 1000 μm or less.
A square steel pipe having a radius of curvature on the outside of the corner portion of more than 3.0 times and 4.0 times or less of the average plate thickness t.
[2] The square steel pipe according to the above [1], wherein the average plate thickness t is more than 0.030 times the average side length H.
[3] The square steel pipe according to the above [1] or [2], wherein the difference between the maximum value and the minimum value of Vickers hardness in the steel pipe is 80 HV or less.
[4] The average plate thickness t is 20 mm or more and 40 mm or less.
The yield strength of the flat plate portion is 295 MPa or more, and the yield strength is 295 MPa or more.
The tensile strength of the flat plate portion is 400 MPa or more.
The yield ratio of the corner is 90% or less,
The square steel pipe according to any one of [1] to [3], wherein the Charpy absorption energy at 0 ° C. of the corner portion is 70 J or more.
[5] Any of the above [1] to [4], wherein the uniform elongation at the t / 4 position from the outer surface of the corner portion is 0.80 times or more the uniform elongation at the t / 4 position from the outer surface of the flat plate portion. The square steel pipe described.
[6] A steel plate is roll-formed, then the roll-formed steel plate is electro-sewn and welded to form an electro-sewn steel pipe, and then the electro-sewn steel pipe is formed by a sizing stand and then square-formed by a square forming stand to form a square steel pipe. Is a method of manufacturing
A method for manufacturing a square steel pipe that controls the gap of the sizing stand immediately before square forming based on the gap of the square forming stand so as to satisfy the following formula (1).
0.30 × t / H + 0.99 ≦ C IN / C OUT <0.50 × t / H + 0.99 ・ ・ ・ Equation (1)
In addition, in equation (1)
C IN : Perimeter (mm) of the electric resistance pipe on the entrance side of the square forming stand of the first stage,
C OUT : Perimeter (mm) of the square steel pipe on the exit side of the square forming stand in the final stage,
t: Average plate thickness (mm) after square forming,
H: Average side length (mm) after square molding,
Is.
(However, when the square molding is performed by the one-stage square molding stand, the first-stage square molding stand and the final-stage square molding stand are the same square molding stand.)
[7] The method for manufacturing a square steel pipe according to the above [6], wherein the average plate thickness t is 20 mm or more and 40 mm or less.
[8] A building structure in which the square steel pipe according to any one of [1] to [5] above is used as a column material.
t=(t1+t2+t3)/3・・・式(2)
式(2)において、t1、t2:溶接部(電縫溶接部)を含む平板部に対して角部を挟んで隣接する2つの平板部夫々の管周方向中央における板厚(mm)、t3:溶接部(電縫溶接部)を含む平板部に対向する平板部の管周方向中央における板厚(mm)である。 The average plate thickness t is obtained from the following formula (2).
t = (t1 + t2 + t3) / 3 ... Equation (2)
In the formula (2), t1, t2: plate thickness (mm), t3 at the center of each of the two flat plate portions adjacent to each other with the corner portion sandwiched by the flat plate portion including the welded portion (electrically sewn welded portion). : The thickness (mm) of the flat plate portion facing the flat plate portion including the welded portion (electrically sewn welded portion) at the center in the pipe circumferential direction.
H=(H1+H2)/2・・・式(3)
式(3)において、H1:管軸方向垂直断面において、任意の平板部と両側の角部を含めて1辺とした略長方形の辺長(図1中の縦の辺長であり、向かい合う1対の平板部において、一方の平板部外面から他方の平板部外面までの距離とも言える。)(mm)、H2:辺長がH1である平板部に対して角部を挟んで隣接する平板部と両側の角部を含む辺の辺長(図1中の横の辺長)(mm)である。すなわち、Hは、角部を挟んで隣接する2つの平板部の管軸方向垂直断面における辺長H1、H2夫々を足して2で割ったものである。 Further, the average side length H is obtained from the following equation (3).
H = (H1 + H2) / 2 ... Equation (3)
In the formula (3), in the H1: vertical cross section in the pipe axis direction, the side length of a substantially rectangular shape including an arbitrary flat plate portion and the corner portions on both sides (the vertical side length in FIG. 1 and facing each other 1). In a pair of flat plates, it can be said that the distance from the outer surface of one flat plate portion to the outer surface of the other flat plate portion.) (Mm), H2: Flat plate portions adjacent to the flat plate portions having a side length of H1 with a corner portion in between. The side length of the side including the corners on both sides (horizontal side length in FIG. 1) (mm). That is, H is the sum of the side lengths H1 and H2 in the vertical cross section of the two flat plates adjacent to each other with the corner portion in between, and divided by two.
これにより、周断面内の強度差が小さく、延性および靱性に優れた冷間ロール成形角形鋼管を製造することが可能となる。また、本発明の角形鋼管を柱材として使用した建築構造物は、従来の冷間成形角形鋼管を使用した建築構造物と比べて、より優れた耐震性能を発揮する。 According to the present invention, it is possible to provide a square steel pipe having a small variation in hardness in the peripheral cross section, excellent ductility and toughness of the outer surface of the corner portion, and having a flat flat plate portion, a method for manufacturing the same, and a building structure. It becomes.
This makes it possible to manufacture a cold roll-formed square steel pipe having a small difference in strength in the peripheral cross section and having excellent ductility and toughness. Further, the building structure using the square steel pipe of the present invention as a column material exhibits more excellent seismic performance as compared with the building structure using the conventional cold-formed square steel pipe.
図1は、本発明の角形鋼管10の管軸方向に対して垂直な断面を示す模式図である。本発明の角形鋼管10は、管周方向に平板部11と角部12とが交互に夫々複数形成されている。角形鋼管10は、図1に示すように、管周方向に角部12、平板部11、角部12、平板部11、角部12、平板部11、角部12及び平板部11が順に4つずつ形成され、管軸方向垂直断面視で長方形(略長方形)又は正方形(略正方形)となる角形鋼管とすることができる。また、本発明の角形鋼管10は、電縫鋼管から得られるロール成形角形鋼管とすることができ、平板部11に形成され、管軸方向に延びた溶接部(電縫溶接部)13も有する。 <Square steel pipe>
FIG. 1 is a schematic view showing a cross section of the
また、本発明でいう曲率半径は、平均曲率半径としてもよいし、任意の箇所での曲率半径としてもよい。但し、より優れた効果を確保するという点からは、任意の箇所での曲率半径とすることが好ましい。
上記曲率半径の測定は、平板部11と角部12の接続点(A、A’)および角部外面からなり、中心が上記L上に存在する中心角90°の扇形において、上記Lと角部外面の交点を中心とした中心角65°の範囲で行う。なお、曲率半径の測定方法は、例えば、上記の中心角65°の範囲において角部外面とよく一致するラジアルゲージから曲率半径を計測する方法などがあるが、これらの限りではない。 As shown in FIG. 1, the radius of curvature on the outside of the corner portion passes through the intersection P of two straight lines L1 and L2 including the outer surfaces of the
Further, the radius of curvature referred to in the present invention may be the average radius of curvature or the radius of curvature at any place. However, from the viewpoint of ensuring a better effect, it is preferable to set the radius of curvature at an arbitrary position.
The measurement of the radius of curvature consists of the connection points (A, A') of the
一方、角部外側の曲率半径が平均板厚tの4.0倍超えであると、平板部の平坦度が十分でなくなり、所望の角形鋼管ではなくなる。また、周断面積が小さくなり、十分な部材強度が得られない。
よって、本発明では、上記角部外側の曲率半径を平均板厚tの3.0倍超4.0倍以下とする。
好ましくは、上記角部外側の曲率半径は平均板厚tの3.1倍以上3.9倍以下であり、より好ましくは、3.2倍以上3.8倍以下である。 When the radius of curvature on the outside of the corner is 3.0 times or less the average plate thickness t, the variation in hardness within the peripheral cross section becomes large, and the desired square steel pipe is not obtained. That is, the corner portion is largely work-hardened, and has higher strength and lower ductility and toughness than the flat plate portion.
On the other hand, if the radius of curvature on the outside of the corner portion exceeds 4.0 times the average plate thickness t, the flatness of the flat plate portion becomes insufficient, and the desired square steel pipe is not obtained. In addition, the peripheral cross-sectional area becomes small, and sufficient member strength cannot be obtained.
Therefore, in the present invention, the radius of curvature on the outside of the corner is set to be more than 3.0 times and 4.0 times or less of the average plate thickness t.
Preferably, the radius of curvature on the outside of the corner portion is 3.1 times or more and 3.9 times or less of the average plate thickness t, and more preferably 3.2 times or more and 3.8 times or less.
角形鋼管では、平均板厚tと平均辺長Hとの比(t/H)が大きいほど角部の加工硬化量が大きくなる。そのため、上記比(t/H)が大きな角形鋼管において、周断面内における強度差、延性および靱性の差は大きくなる傾向にある。
本発明では、上記角部外側の曲率半径を平均板厚の3.0倍超4.0倍以下とするため、t/Hが0.030超となっても、周断面内の強度差を小さくし、優れた延性および靱性が得られる。 Further, in the present invention, t / H can be set to more than 0.030 as the relationship between the average plate thickness t (mm) of the
In a square steel pipe, the larger the ratio (t / H) of the average plate thickness t and the average side length H, the larger the amount of work hardening at the corners. Therefore, in a square steel pipe having a large ratio (t / H), the difference in strength, ductility and toughness in the peripheral cross section tends to be large.
In the present invention, since the radius of curvature on the outside of the corner is more than 3.0 times and 4.0 times or less of the average plate thickness, even if t / H exceeds 0.030, the strength difference in the peripheral cross section is increased. It is small and has excellent ductility and toughness.
t=(t1+t2+t3)/3・・・式(2)
式(2)において、t1、t2:溶接部(電縫溶接部)13を含む平板部11に対して角部12を挟んで隣接する2つの平板部11夫々の管周方向中央における板厚(mm)、t3:溶接部(電縫溶接部)13を含む平板部11に対向する平板部11の管周方向中央における板厚(mm)である。 Here, the average plate thickness t is obtained from the following equation (2).
t = (t1 + t2 + t3) / 3 ... Equation (2)
In the formula (2), t1, t2: plate thickness (plate thickness) at the center of each of the two
H=(H1+H2)/2・・・式(3)
式(3)において、H1:図1中の縦の辺長(mm)、H2:図1中の横の辺長(mm)であり、すなわち、Hは、管軸方向垂直断面において、角部12を挟んで隣接する2つの平板部11夫々における両側の角部12を含めた辺長H1、H2を足して2で割ったものである。 Further, the average side length H is obtained from the following equation (3).
H = (H1 + H2) / 2 ... Equation (3)
In the formula (3), H1: the vertical side length (mm) in FIG. 1, and H2: the horizontal side length (mm) in FIG. 1, that is, H is a corner portion in the vertical cross section in the pipe axis direction. The side lengths H1 and H2 including the
上記のビッカース硬さ試験は、JIS Z 2244の規定に準拠し、試験力を98N(10kgf)として実施することができる。 In the
The above Vickers hardness test can be carried out in accordance with JIS Z 2244 with a test force of 98N (10 kgf).
上記の降伏強度、引張強度、降伏比、均一伸び(平板部:E1、角部:E2)は、JIS Z 2241の規定に準拠して引張試験を実施することで得られる。シャルピー吸収エネルギーは、JIS Z 2242の規定に準拠して、Vノッチ標準試験片を用い、試験温度:0℃でシャルピー衝撃試験を実施することで得られる。 Further, in the
The yield strength, tensile strength, yield ratio, and uniform elongation (flat plate portion: E1, corner portion: E2) can be obtained by carrying out a tensile test in accordance with JIS Z 2241. The Charpy absorbed energy is obtained by performing a Charpy impact test at a test temperature of 0 ° C. using a V-notch standard test piece in accordance with JIS Z 2242.
ここで、式(4)中、C、Mn、Si、Ni、Cr、Mo、Vは、各元素の含有量(質量%)である。(但し、含有しない元素は0(零)%とする。)
Pcm=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B・・・式(5)
ここで、式(5)中、C、Si、Mn、Cu、Ni、Cr、Mo、V、Bは、各元素の含有量(質量%)である。(但し、含有しない元素は0(零)%とする。)
式(4)中のCeqは炭素当量であり、溶接部(電縫溶接部)13および熱影響部の硬さの指標となる。Ceqが0.15%未満であると建築構造物の柱材として必要な強度が得られない場合がある。また、Ceqが0.50%を超えると溶接部13および熱影響部が過度に硬化し、周断面強度のばらつきが大きくなる場合がある。よって、本発明では、Ceqが0.15%以上0.50%以下であることが好ましい。また、より好ましくは、Ceqは0.20%以上であり、さらに好ましくは、0.25%以上である。また、より好ましくは、Ceqは0.45%以下であり、さらに好ましくは、0.40%以下である。 Ceq = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 ... Equation (4)
Here, in the formula (4), C, Mn, Si, Ni, Cr, Mo, and V are the contents (mass%) of each element. (However, the element not contained is 0 (zero)%.)
Pcm = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5B ... Equation (5)
Here, in the formula (5), C, Si, Mn, Cu, Ni, Cr, Mo, V, and B are the contents (mass%) of each element. (However, the element not contained is 0 (zero)%.)
Ceq in the formula (4) is a carbon equivalent, and is an index of the hardness of the welded portion (electrically sewn welded portion) 13 and the heat-affected zone. If Ceq is less than 0.15%, the strength required as a pillar material of a building structure may not be obtained. Further, if Ceq exceeds 0.50%, the welded
次に、本発明の角形鋼管10の製造方法を述べる。 <Manufacturing method of square steel pipe>
Next, a method for manufacturing the
0.30×t/H+0.99≦CIN/COUT<0.50×t/H+0.99・・・式(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電縫鋼管の周長(mm)、
COUT:最終段の角成形スタンド出側における角形鋼管の周長(mm)、
t:角成形後の平均板厚(mm)、
H:角成形後の平均辺長(mm)、である。 In the method for manufacturing a
0.30 × t / H + 0.99 ≦ C IN / C OUT <0.50 × t / H + 0.99 ・ ・ ・ Equation (1)
In addition, in equation (1)
C IN : Perimeter (mm) of the electric resistance pipe on the entrance side of the square forming stand of the first stage,
C OUT : Perimeter (mm) of the square steel pipe on the exit side of the square forming stand in the final stage,
t: Average plate thickness (mm) after square forming,
H: The average side length (mm) after square molding.
t=(t1+t2+t3)/3・・・式(2)
式(2)において、t1、t2:溶接部(電縫溶接部)13を含む平板部11に対して角部12を挟んで隣接する2つの平板部11夫々の管周方向中央における板厚(mm)、t3:溶接部(電縫溶接部)13を含む平板部11に対向する平板部11の管周方向中央における板厚(mm)である。 The average plate thickness t is obtained from the following formula (2).
t = (t1 + t2 + t3) / 3 ... Equation (2)
In the formula (2), t1, t2: plate thickness (plate thickness) at the center of each of the two
H=(H1+H2)/2・・・式(3)
式(3)において、H1:図1中の縦の辺長(mm)、H2:図1中の横の辺長(mm)であり、すなわち、Hは、管軸方向垂直断面において、角部12を挟んで隣接する2つの平板部11夫々における両側の角部12を含めた辺長H1、H2を足して2で割ったものである。 Further, the average side length H is obtained from the following equation (3).
H = (H1 + H2) / 2 ... Equation (3)
In the formula (3), H1: the vertical side length (mm) in FIG. 1, and H2: the horizontal side length (mm) in FIG. 1, that is, H is a corner portion in the vertical cross section in the pipe axis direction. The side lengths H1 and H2 including the
ただし、鋼管周長が合計で2.0%超の割合で減少するように縮径した場合、ロール通過時の管軸方向の曲げ量が大きくなり、縮径後の管軸方向の残留応力がかえって上昇してしまう。このため、鋼管周長が0.30%以上2.0%以下の割合で減少するように縮径することが好ましい。 In the sizing step after the electric resistance welding, which will be described later with reference to FIG. 4, the total circumference of the steel pipe is 0.30% or more in order to satisfy the preferable roundness and the residual stress in the pipe axial direction. The diameter of the steel pipe may be reduced so as to decrease in proportion.
However, if the diameter is reduced so that the circumference of the steel pipe decreases at a rate of more than 2.0% in total, the amount of bending in the pipe axis direction when passing through the roll becomes large, and the residual stress in the pipe axis direction after the diameter reduction increases. On the contrary, it rises. Therefore, it is preferable to reduce the diameter so that the circumference of the steel pipe decreases at a rate of 0.30% or more and 2.0% or less.
円筒状の素管である電縫鋼管7を角形鋼管10に成形する場合、上述したように、角成形ロール群9に鋼管を通すことで、徐々に円筒形から角形に成形を施す。このような角成形においては、辺の直線部(平板部11(図1も再参照))の曲げ戻し、角部12の曲げおよび周方向の絞り変形が発生する。 0.30 × t / H + 0.99 ≦ C IN / C OUT <0.50 × t / H + 0.99 ・ ・ ・ Equation (1)
When the
また、COUTは、最終段の角成形スタンド出側における角形鋼管10の周長(管周方向の外周の長さ)(mm)である。COUTは、ロール群の最終段の角成形スタンドのいずれか1つの回転軸のX座標をXc(m)とし、X軸に垂直な平面X=Xc+1(m)における管の周断面の外周を巻尺で測定することで得られる(図4参照)。 C IN is the peripheral length (the length of the outer circumference in the peripheral direction of the pipe) (mm) of the
Further, C OUT is the peripheral length (the length of the outer circumference in the peripheral direction of the pipe) (mm) of the
なお、サイジングスタンドが複数段存在する場合には、上記の角成形直前のサイジングスタンドのギャップとその他のサイジングスタンドのギャップとは同じとしてもよい。
また、角成形スタンドが複数段存在する場合には、上記の角成形スタンドのギャップは、第一段目の角成形スタンドのギャップとすることが好ましい。また、第一段目とその他の角成形スタンドのギャップは全て同じとしてもよい。 When G is less than 70, (C IN / C OUT ) in equation (1) is smaller than the value on the left side, and when G is more than 180, (C IN / C OUT ) in equation (1) is greater than or equal to the value on the right side. It becomes.
When there are a plurality of stages of sizing stands, the gap of the sizing stand immediately before the square forming and the gap of the other sizing stands may be the same.
When there are a plurality of stages of the square forming stand, it is preferable that the gap of the square forming stand is the gap of the first stage of the square forming stand. Further, the gaps between the first stage and the other square forming stands may all be the same.
本発明の建築構造物は、前述した本発明の角形鋼管10を柱材として使用される。
図5は、本発明の建築構造物100の一例を示す模式図である。
本発明の建築構造物100は、ダイアフラム17と角形鋼管10とが溶接され、角形鋼管10は柱材として用いられる。その他に、図5に示すように、建築構造物100は、大梁18、小梁19、間柱20により形成され、その他に公知の部材によって形成されてもよい。
角形鋼管10は、前述したように、周断面内の硬さのばらつきが小さく、且つ平坦な平板部11を有する。そのため、この角形鋼管10を柱材として使用した本発明の建築構造物100は、優れた耐震性能を発揮する。 <Building structure>
In the building structure of the present invention, the
FIG. 5 is a schematic view showing an example of the
In the
As described above, the
t=(t1+t2+t3)/3・・・式(2)
式(2)において、t1、t2:溶接部(電縫溶接部)を含む平板部に対して角部を挟んで隣接する2つの平板部夫々の管周方向中央における板厚(mm)、t3:電縫溶接部を含む平板部に対向する平板部の管周方向中央における板厚(mm)である。 The average plate thickness t was obtained from the following formula (2).
t = (t1 + t2 + t3) / 3 ... Equation (2)
In the formula (2), t1, t2: plate thickness (mm), t3 at the center of each of the two flat plate portions adjacent to each other with the corner portion sandwiched by the flat plate portion including the welded portion (electrically sewn welded portion). : The thickness (mm) at the center of the flat plate portion facing the flat plate portion including the electric sewing welded portion in the pipe circumferential direction.
H=(H1+H2)/2・・・式(3)
式(3)において、H2:管軸方向垂直断面において、電縫溶接部が形成された平板部と両側の角部を含む辺の辺長、H1:辺長がH2である平板部に対して角部を挟んで隣接する平板部と両側の角部を含む辺の辺長(mm)である。 The average side length H was obtained from the following equation (3).
H = (H1 + H2) / 2 ... Equation (3)
In the formula (3), H2: the side length of the side including the flat plate portion on which the electric sewing welded portion is formed and the corners on both sides in the vertical cross section in the pipe axis direction, and H1: the flat plate portion having the side length of H2. It is the side length (mm) of the side including the flat plate portion adjacent to each other across the corner portion and the corner portions on both sides.
角部外側の曲率半径測定にはラジアルゲージを使用した。曲率半径の測定方法については、角部に隣接する両側の平板部外面をそれぞれ含む2本の直線L1およびL2の交点Pを通り、L1またはL2と45°をなす直線Lと角部外側の交点における曲率半径を角部外側の曲率半径として測定した(図1再参照)。具体的に、曲率半径の測定は、平板部と角部の接続点(A、A’)および角部外面からなり、中心が上記L上に存在する中心角90°の扇形において、上記Lと角部外面の交点を中心とした中心角65°の範囲で行い、上記の中心角65°の範囲において角部外面とよく一致するラジアルゲージから曲率半径を計測した。 Further, the radii of curvature of the outer surfaces (outside the corners) of the four corners were measured at 10 arbitrary positions in the pipe axis direction of the obtained square steel pipe, and the maximum value Rmax and the minimum value Rmin of the total of 40 points were measured. I asked for each.
A radial gauge was used to measure the radius of curvature on the outside of the corner. Regarding the method of measuring the radius of curvature, the intersection of the straight line L forming 45 ° with L1 or L2 and the outside of the corner through the intersection P of the two straight lines L1 and L2 including the outer surfaces of the flat plates on both sides adjacent to the corner. The radius of curvature in was measured as the radius of curvature outside the corner (see FIG. 1 again). Specifically, the measurement of the radius of curvature consists of the connection points (A, A') of the flat plate portion and the corner portion and the outer surface of the corner portion, and in a sector having a central angle of 90 ° whose center exists on the above L, the above L The measurement was performed in a range of a central angle of 65 ° centered on the intersection of the outer surfaces of the corners, and the radius of curvature was measured from a radial gauge that closely coincided with the outer surface of the corners in the range of 65 ° of the central angle.
上記のビッカース硬さ試験は、JIS Z 2244の規定に準拠し、試験力を98N(10kgf)として実施した。平板部の硬さ測定は、電縫溶接部を含む平板部の隣の平板部において行い、角部の硬さ測定は、電縫溶接部を含む平板部に隣接する角部において行った。 In the cross section obtained by cutting the obtained square steel pipe perpendicularly to the pipe axis direction, the Vickers hardness of the flat plate portion, the corner portion and the welded portion (electrically sewn welded portion) is 1 mm in the thickness direction from the inner and outer surfaces and the center of the plate thickness, respectively. The maximum value HVmax and the minimum value HVmin were determined respectively.
The above Vickers hardness test was carried out in accordance with JIS Z 2244 with a test force of 98 N (10 kgf). The hardness of the flat plate portion was measured at the flat plate portion adjacent to the flat plate portion including the electric sewing welded portion, and the hardness of the corner portion was measured at the corner portion adjacent to the flat plate portion including the electric sewing welded portion.
これらを用いてJIS Z 2241の規定に準拠して引張試験を実施し、降伏強度YS、引張強度TS、均一伸び(平板部:E1、角部:E2)を測定し、(降伏強度)/(引張強度)で定義される降伏比を算出した。均一伸びは、最大荷重時の全伸びの値とした。なお、平板部の引張試験片は、角形鋼管の電縫溶接部を含む平板部の隣の平板部における幅中央部の位置から採取した。角部の引張試験片は、電縫溶接部を含む平板部に隣接する角部から採取した。
試験片本数は各2本とし、それらの平均値を算出して降伏強度YS、引張強度TS、降伏比、均一伸びを求めた。 Further, as shown in FIG. 11, JIS No. 5 tensile test pieces and JIS No. 12B tensile test pieces shown by broken lines were collected from the flat plate portion and the corner portion of the square steel pipe so that the tensile direction was parallel to the pipe axis direction, respectively. Each of them was ground so that the thickness was 5 mm and the thickness center was at the t / 4 position of the plate thickness t from the outer surface of the pipe, and a tensile test piece was taken. More specifically, as shown in FIG. 12, the tensile test piece at the corner portion passes through an intersection in which the outer surfaces of the flat plate portions on both sides adjacent to the corner portion are extended, and 45 ° with each of the outer surfaces of the flat plate portion. Collected from the eggplant line.
Using these, a tensile test was carried out in accordance with the provisions of JIS Z 2241, and the yield strength YS, tensile strength TS, and uniform elongation (flat plate: E1, corner: E2) were measured, and (yield strength) / ( The yield ratio defined by (tensile strength) was calculated. The uniform elongation is the value of the total elongation at the maximum load. The tensile test piece of the flat plate portion was taken from the position of the center of the width in the flat plate portion next to the flat plate portion including the electric resistance welded portion of the square steel pipe. Tensile test pieces at the corners were taken from the corners adjacent to the flat plate including the electric stitch welded part.
The number of test pieces was two each, and the average values thereof were calculated to determine the yield strength YS, tensile strength TS, yield ratio, and uniform elongation.
平坦度の測定は、角形鋼管の管軸方向の任意の位置10箇所において、平板部4箇所をそれぞれ測定対象として、計40箇所において行った。図10に示すように、各平板部外面の周方向両端の2点を通る直線に対する最大膨らみ量及び最大凹み量をそれぞれ測定し、各測定箇所における最大膨らみ量及び最大凹み量の絶対値の最大値を平坦度とした。ただし、膨らみ量は正の値、凹み量は負の値とし、膨らみまたは凹みが存在しなかった場合は、膨らみ量または凹み量の値を0とした。 FIG. 10 is a schematic diagram for explaining a method of measuring flatness.
The flatness was measured at 10 arbitrary positions in the pipe axis direction of the square steel pipe, and at 40 points in total, with 4 flat plate portions as measurement targets. As shown in FIG. 10, the maximum bulge amount and the maximum dent amount with respect to the straight line passing through the two points at both ends in the circumferential direction of each flat plate portion are measured, and the maximum absolute value of the maximum bulge amount and the maximum dent amount at each measurement point is measured. The value was flatness. However, the bulge amount was set to a positive value, the dent amount was set to a negative value, and when there was no bulge or dent, the bulge amount or dent amount value was set to 0.
また、本発明例の角形鋼管は、平坦度が2.5mm以下であった。 The square steel pipes of the examples of the present invention all have a circumference ratio (C IN / C OUT ) within the range of Eq. (1), and the radius of curvature (Rmin, Rmax) on the outside of the corner is 3.0 times the plate thickness. It is super 4.0 times or less, and the uniform elongation at the position of t / 4 from the outer surface of the corner portion is 0.80 times or more of the uniform elongation at the position of t / 4 from the outer surface of the flat plate portion, and the uniform elongation of the corner portion and the flat plate portion. The difference in hardness was 80 HV or less between the maximum and minimum values of Vickers hardness at the position 1 mm from the inner and outer surfaces and the position at the center of the plate thickness.
Further, the square steel pipe of the example of the present invention had a flatness of 2.5 mm or less.
また、比較例のNo.2、10、12、15は、いずれも周長比(CIN/COUT)が式(1)の範囲を上回っており、角部外側の曲率半径が板厚の3.0倍以下であり、シャルピー吸収エネルギーが所望の値に達しなかった。 Comparative example No. In 2, 10, 12, and 15, the circumference ratio (C IN / C OUT ) exceeds the range of the equation (1), and the radius of curvature on the outside of the corner is 3.0 times or less of the plate thickness. , The uniform elongation at the t / 4 position from the outer surface of the corner is less than 0.80 times the uniform elongation at the t / 4 position from the outer surface of the flat plate, and the difference between the maximum and minimum values of Vickers hardness is the desired value. Did not reach.
In addition, No. In 2, 10, 12, and 15, the circumference ratio (C IN / C OUT ) exceeds the range of the equation (1), and the radius of curvature on the outside of the corner is 3.0 times or less of the plate thickness. , Charpy absorption energy did not reach the desired value.
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 角形鋼管
11 平板部
12 角部
13 溶接部(電縫溶接部)
14 母材部
15 溶接熱影響部
16 溶融凝固部
17 ダイアフラム
18 大梁
19 小梁
20 間柱
100 建築構造物
1 Steel strip (steel plate)
2
14
Claims (8)
- 管周方向に平板部と角部とが交互に夫々複数形成されており、
管軸方向に延びた溶接部が更に形成されており、
前記溶接部における溶融凝固部の管周方向の幅が1.0μm以上1000μm以下であり、前記角部外側の曲率半径が平均板厚tの3.0倍超4.0倍以下である角形鋼管。 A plurality of flat plates and corners are alternately formed in the circumferential direction of the pipe.
A welded portion extending in the pipe axis direction is further formed.
A square steel pipe in which the width of the melt-solidified portion in the welded portion in the pipe circumferential direction is 1.0 μm or more and 1000 μm or less, and the radius of curvature on the outside of the corner portion is more than 3.0 times and 4.0 times or less of the average plate thickness t. .. - 前記平均板厚tが平均辺長Hの0.030倍超である請求項1に記載の角形鋼管。 The square steel pipe according to claim 1, wherein the average plate thickness t is more than 0.030 times the average side length H.
- 鋼管内でビッカース硬さの最大値と最小値の差が80HV以下である請求項1又は2に記載の角形鋼管。 The square steel pipe according to claim 1 or 2, wherein the difference between the maximum value and the minimum value of Vickers hardness in the steel pipe is 80 HV or less.
- 前記平均板厚tが20mm以上40mm以下であり、
前記平板部の降伏強度が295MPa以上であり、
前記平板部の引張強度が400MPa以上であり、
前記角部の降伏比が90%以下であり、
前記角部の0℃におけるシャルピー吸収エネルギーが70J以上である請求項1~3のいずれかに記載の角形鋼管。 The average plate thickness t is 20 mm or more and 40 mm or less.
The yield strength of the flat plate portion is 295 MPa or more, and the yield strength is 295 MPa or more.
The tensile strength of the flat plate portion is 400 MPa or more.
The yield ratio of the corner is 90% or less,
The square steel pipe according to any one of claims 1 to 3, wherein the charpy absorption energy of the corner portion at 0 ° C. is 70 J or more. - 前記角部外面からt/4の位置における均一伸びが、平板部外面からt/4の位置における均一伸びの0.80倍以上である請求項1~4のいずれかに記載の角形鋼管。 The square steel pipe according to any one of claims 1 to 4, wherein the uniform elongation at the t / 4 position from the outer surface of the corner portion is 0.80 times or more the uniform elongation at the t / 4 position from the outer surface of the flat plate portion.
- 鋼板をロール成形し、次いでロール成形した前記鋼板を電縫溶接して電縫鋼管とした後、前記電縫鋼管をサイジングスタンドによって成形し、次いで角成形スタンドによって角成形して角形鋼管を製造する方法であって、
以下の式(1)を満たすように、前記角成形スタンドのギャップに基づいて角成形直前の前記サイジングスタンドのギャップを制御する角形鋼管の製造方法。
0.30×t/H+0.99≦CIN/COUT<0.50×t/H+0.99・・・式(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電縫鋼管の周長(mm)、
COUT:最終段の角成形スタンド出側における角形鋼管の周長(mm)、
t:角成形後の平均板厚(mm)、
H:角成形後の平均辺長(mm)、
である。
(但し、1段の角成形スタンドにより前記角成形を行う場合には、前記第一段目の角成形スタンドと前記最終段の角成形スタンドとは、同一の角成形スタンドとする。) A steel plate is roll-formed, and then the roll-formed steel plate is electrosewn and welded to form an electrosewn steel pipe, and then the electrosewn steel pipe is formed by a sizing stand and then squarely formed by a square forming stand to manufacture a square steel pipe. It's a method
A method for manufacturing a square steel pipe that controls the gap of the sizing stand immediately before square forming based on the gap of the square forming stand so as to satisfy the following formula (1).
0.30 × t / H + 0.99 ≦ C IN / C OUT <0.50 × t / H + 0.99 ・ ・ ・ Equation (1)
In addition, in equation (1)
C IN : Perimeter (mm) of the electric resistance pipe on the entrance side of the square forming stand of the first stage,
C OUT : Perimeter (mm) of the square steel pipe on the exit side of the square forming stand in the final stage,
t: Average plate thickness (mm) after square forming,
H: Average side length (mm) after square molding,
Is.
(However, when the square molding is performed by the one-stage square molding stand, the first-stage square molding stand and the final-stage square molding stand are the same square molding stand.) - 前記平均板厚tが20mm以上40mm以下である請求項6に記載の角形鋼管の製造方法。 The method for manufacturing a square steel pipe according to claim 6, wherein the average plate thickness t is 20 mm or more and 40 mm or less.
- 請求項1~5のいずれかに記載の角形鋼管が、柱材として使用されている建築構造物。 A building structure in which the square steel pipe according to any one of claims 1 to 5 is used as a column material.
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WO2022075026A1 (en) * | 2020-10-05 | 2022-04-14 | Jfeスチール株式会社 | Rectangular steel pipe and production method therefor, and building structure |
JPWO2023276644A1 (en) * | 2021-07-02 | 2023-01-05 |
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