WO2020100603A1 - Tuyau d'acier, tuyau d'acier pour palier et procédé de production de tuyau d'acier - Google Patents

Tuyau d'acier, tuyau d'acier pour palier et procédé de production de tuyau d'acier Download PDF

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Publication number
WO2020100603A1
WO2020100603A1 PCT/JP2019/042661 JP2019042661W WO2020100603A1 WO 2020100603 A1 WO2020100603 A1 WO 2020100603A1 JP 2019042661 W JP2019042661 W JP 2019042661W WO 2020100603 A1 WO2020100603 A1 WO 2020100603A1
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steel pipe
mass
steel
welding
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PCT/JP2019/042661
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English (en)
Japanese (ja)
Inventor
秋月　誠
翔平 三町
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日鉄日新製鋼株式会社
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Publication of WO2020100603A1 publication Critical patent/WO2020100603A1/fr

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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
    • B21C37/08—Making tubes with welded or soldered seams
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K13/00—Welding by high-frequency current heating
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints

Definitions

  • the present invention relates to a steel pipe, a steel pipe for bearings, and a method for manufacturing a steel pipe.
  • Welded steel pipe is generally manufactured by welding steel plates or steel strips.
  • high-frequency welding is performed on a low-carbon steel sheet having a carbon content of 0.15 mass% or more and 0.4 mass% or less, and then diameter reduction rolling is performed so that a bond width of an electric resistance welded portion is 25 ⁇ m or less.
  • an electric resistance welded steel pipe which is a kind of welded steel pipe and is mechanically narrowed.
  • Patent Document 1 discloses that a decrease in the strength of the welded portion is prevented by narrowing the bond width of the welded portion in the low carbon steel pipe. However, there is no disclosure about the influence of the bond width of the welded portion in the high carbon steel pipe on the annealing time for improving the workability of the welded portion.
  • One aspect of the present invention is intended to realize a high carbon steel pipe capable of shortening the annealing time of a welded portion.
  • the steel pipe which concerns on one aspect of this invention has C: 0.4 mass% or more and 1.5 mass% or less, P: 0.03 mass% or less, and Cu: 0.3 mass.
  • % Steel plate or steel strip containing less than or equal to 1%, the ends are welded at a welding temperature of 1200 ° C. or higher and 1700 ° C. or lower, and the ends are melted by heating.
  • the width of the formed bond portion is 0.2% or more and 1.2% or less with respect to the plate thickness of the steel plate or steel strip.
  • a manufacturing method of a steel pipe concerning one mode of the present invention is C: 0.4 mass% or more and 1.5 mass% or less, P: 0.03 mass% or less, and Cu: 0.
  • a method for producing a steel pipe in which the ends of steel sheets or steel strips are welded to each other, containing 3 mass% or less, the step of bending the steel sheet or steel strips to bring the ends into contact with each other, and heating the ends. In the state where the end portions are pressed against each other such that the width of the bond portion formed by melting the portion is 0.2% or more and 1.2% or less of the plate thickness of the steel plate or the steel strip. And a step of welding at a temperature of 1200 ° C. or more and 1700 ° C. or less.
  • FIG. 1 It is a schematic diagram which shows the welding part of the steel pipe which concerns on one Embodiment of this invention. It is a figure showing the photograph which shows the welding part of the steel pipe which concerns on one Embodiment of this invention.
  • (A)-(d) is sectional drawing which shows the cross-sectional shape of the steel pipe 1, respectively. It is a schematic diagram which shows the crushing width and crushing angle of the steel pipe which concerns on one Embodiment of this invention.
  • (A) And (b) is a schematic diagram which shows the upset amount of the steel pipe which concerns on one Embodiment of this invention.
  • the welding method in the present invention is not limited to electric resistance welding and is a method of welding and joining by heating the seam portion of the steel pipe. I wish I had it.
  • FIG. 1 is a schematic diagram showing a welded portion 3 of a steel pipe 1 according to this embodiment.
  • the steel pipe 1 welds the edge part of the steel plate or steel strip containing C: 0.4 mass% or more and 1.5 mass% or less, P: 0.03 mass% or less, and Cu: 0.3 mass% or less. It is formed by.
  • the ends are welded to each other at a welding temperature of 1200 ° C. or higher and 1700 ° C. or lower, and the width of the bond portion 4 formed by melting the ends by heating is equal to the plate thickness of the steel plate or the steel strip. On the other hand, it is 0.2% or more and 1.2% or less.
  • the welded portion 3 is a portion where the steel strip 2 is welded, for example, a weld bead portion.
  • the steel strip 2 may be a steel plate.
  • a bond 4 and a heat-affected zone 5 are formed in the weld 3.
  • the bond part 4 is formed between the two heat-affected parts 5 in the weld part 3.
  • the electric resistance welded portion is heated to a solid-liquid coexisting region.
  • C contained outside the electric resistance weld is concentrated in the liquid phase and decreased in the solid phase.
  • the liquid phase enriched with C is discharged to the outside of the electric resistance welded portion by pressing (upsetting) the ends of the steel strip 2 to form a bead.
  • the solid phase with reduced C remains in the welded portion 3 and the solid phase forms the bond portion 4.
  • the heat-affected zone 5 is an area in which the metallographic structure at the end portion is changed by heat during electric resistance welding, and is an area other than the bond portion 4.
  • the welded portion 3 is preferably subjected to a spheroidizing annealing treatment described later in order to improve workability.
  • the heat-affected zone 5 has a structure in which undissolved carbide and martensite are mixed due to heating during welding.
  • the bond portion 4 is heated to a temperature higher than that of the heat-affected zone 5 due to heating during welding, and thus has a structure of only martensite containing no undissolved carbide.
  • the heat-affected zone 5 finishes spheroidizing annealing in a short time because the carbide grows with the undissolved carbide as the nucleus, but the bond portion 4 does not undergo the undissolved annealing. Carbides are not included. Therefore, in the bond part 4, after the carbide is first deposited inside the bond part 4, the carbide grows.
  • the bond part 4 needs to be annealed for a longer time than the heat-affected part 5. Further, the wider the bond portion 4 is, the longer the spheroidizing annealing needs to be performed. That is, by reducing the width of the bond portion 4, it is possible to shorten the time required for the spheroidizing annealing of the weld portion 3.
  • FIG. 2 is a view showing a photograph showing the welded portion 3 of the steel pipe 1.
  • the steel pipe 1 is formed such that the width of the bond portion 4 is 0.2% or more and 1.2% or less of the plate thickness of the steel strip 2.
  • the welding temperature is preferably 1200 ° C. or higher and 1700 ° C. or lower.
  • the width of the bond portion 4 is 1.2% or less of the plate thickness, the spheroidizing annealing time after welding can be made relatively short.
  • the width of the bond portion 4 is 0 (zero), it is impossible to determine whether the welding is properly performed. Therefore, the width of the bond portion 4 is 0.2% or more of the plate thickness. preferable.
  • the steel pipe 1 is excellent in rolling contact fatigue life because it contains a specific component in a specific amount as described above.
  • rolling fatigue life refers to a period until surface peeling occurs in the base material of the steel pipe 1 and the welded portion 3 due to rolling movement of the bearing using the steel pipe 1.
  • excellent in rolling contact fatigue life means that the above-mentioned period is as long as that of seamless steel pipe that has been frequently used as high carbon steel pipe.
  • the rolling fatigue life is obtained by, for example, cutting a welded steel pipe and processing it into a plate shape, and then measuring the period until surface peeling occurs in the base material and the welded portion 3 by a thrust type rolling fatigue test. be able to.
  • the steel pipe 1 may contain non-metallic inclusions such as sulfide and oxygen.
  • non-metallic inclusions such as sulfide and oxygen.
  • sulfides, especially MnS aggregate and precipitate on the surface of the steel pipe, causing cracks and surface scratches originating from the non-metallic inclusions, resulting in a rolling fatigue life. It may decrease.
  • the particle size of non-metallic inclusions such as sulfides is preferably 20 ⁇ m or less, and more preferably 10 ⁇ m or less. Since the particle size of the non-metallic inclusions in the steel pipe 1 is as small as the above-mentioned preferable range, reduction of rolling fatigue life and increase of manufacturing cost are prevented especially when the non-metallic inclusions are sulfides. can do.
  • the oxygen content in the steel pipe 1 is preferably 20 ppm or less, and more preferably 15 ppm or less.
  • the steel pipe 1 having higher cleanliness can be obtained.
  • the steel pipe 1 having a better rolling fatigue life can be obtained.
  • the diameter of the steel pipe 1 is preferably 15 mm or more and 300 mm or less. Further, the thickness of the steel plate or the steel strip used to form the steel pipe 1 is preferably 2 mm or more and 10 mm or less. Since the diameter of the steel pipe 1 and the thickness of the steel plate or the steel strip are in the above-described preferable ranges, the steel pipe 1 can be manufactured without requiring special manufacturing conditions.
  • the steel pipe 1 may be a round pipe having a substantially circular cross-sectional shape in a cross section perpendicular to the drawing direction of the steel pipe 1.
  • the steel pipe 1 may be a rectangular pipe having the above-mentioned cross-sectional shape of a substantially rectangular shape.
  • it may be a deformed tube whose cross-sectional shape is other than substantially circular or rectangular.
  • the cross-sectional shape of the deformed tube may be, for example, a semicircular shape as shown in FIG. 3C or a drum shape as shown in FIG. 3D.
  • the steel strip 2 is preferably used as a raw material for the steel pipe 1.
  • the steel strip 2 is formed into a tubular shape by being subjected to roll forming, and becomes the steel pipe 1 by being subjected to welding, quenching treatment, tempering treatment and spheroidizing annealing.
  • the amount and size of non-metallic inclusions on the outer surface side and the inner surface side of the steel pipe differ due to the effect of center segregation of the steel bar that is the base material.
  • the non-metallic inclusions on the outer surface side are fine and minute, but a large amount of the non-metallic inclusions are present on the inner surface and are exposed on the inner surface.
  • the outer ring of the rolling bearing uses the inner surface of the seamless steel pipe, but the large amount of non-metallic inclusions on the inner surface has a great influence on the rolling fatigue life. .. From this, in order to prolong the rolling fatigue life, it is necessary to largely perform the turning process on the inner surface of the bearing seamless steel pipe, which is in contact with the rolling elements, which increases the processing cost.
  • the steel pipe 1 that is, the welded steel pipe such as the electric resistance welded steel pipe to which the steel strip 2 is welded, unlike the seamless steel pipe, has many non-metallic inclusions inside the steel strip and almost all on the front and back surfaces. do not do. Therefore, the welded steel pipe using a steel strip as a base material has a higher cleanness on the inner surface side than the seamless steel pipe, and the difference in cleanness between the inner surface and the outer surface of the steel pipe can be reduced.
  • the steel pipe 1 since the steel pipe 1 has a high degree of cleanliness on the inner surface side, it is possible to obtain a rolling fatigue life equivalent to that of a seamless steel pipe while reducing the amount of cutting when processing into a part shape.
  • the steel pipe 1 is obtained by welding the steel strip 2, it is possible to easily mass-produce the steel pipe, as compared with the case of manufacturing the steel pipe by punching a bar material.
  • the steel strip 2 refers to, among steel plates, a coil-shaped product having a thickness of 10 mm or less, for example.
  • either the steel strip 2 or the steel plate can be used as the raw material of the present embodiment, but it is preferable to manufacture the steel pipe 1 using the steel strip 2.
  • the productivity is improved by using the steel strip 2 which is thinner than the steel plate and has excellent roll formability described later. Thereby, the steel pipe 1 can be manufactured more efficiently.
  • the steel strip 2 can be obtained, for example, by hot rolling steel.
  • the steel strip 2 is formed into a tubular shape by passing the steel strip 2 between the rollers.
  • the roll forming is easier when the steel strip 2 is used as the base material than the above steel plate, it is preferable to form the coiled steel strip 2 by hot rolling the steel before the roll forming. ..
  • the steel strip 2 may be washed with an acid or annealed under the conditions of 600 ° C. or higher and 800 ° C. or lower and 1 hour or longer and 50 hours or shorter. This facilitates roll forming.
  • crushing In order to adjust the shape and strength of the welded portion 3 between the ends of the steel strip 2 formed into a tubular shape by the roll forming, the corner portions located inside the pipe at the ends are formed by a crushing roll. It is crushed (hereinafter, "crushing"). By properly setting the width and angle of the crushing, it is possible to obtain a sound welded portion 3 with little strength reduction in butt welding described later.
  • FIG. 4 is a schematic diagram showing the crushing width C and the crushing angle ⁇ of the steel pipe 1 according to the present embodiment.
  • the width of the crushing (crushing width C) is preferably 5% or more and 40% or less of the plate thickness of the steel strip 2.
  • the crushing width C is a portion in which the corners of the steel strip 2 are crushed in the plate width direction of the steel strip 2 when the longitudinal direction of the steel pipe 1 is the longitudinal direction of the steel strip 2. Means the length corresponding to.
  • the crushing angle ⁇ means the smaller one of the angles formed by the plane including the lower surface 2A (or the upper surface) of the steel strip 2 and the surface 2B formed by the crushing.
  • the crushing angle ⁇ is preferably 20 degrees or more and 60 degrees or less, and most preferably 45 degrees.
  • the crushing width C When the crushing width C is small or when the crushing angle ⁇ is small, the amount of molten metal generated during welding is discharged from the boundary between the welded ends of the steel strip 2 (molten metal discharge amount) is small. Become. Therefore, a wide portion is formed in the bond portion 4, and a long-time annealing process is required in the wide portion. Further, when the crushing width C is large or the crushing angle ⁇ is large, the area of the welded end of the steel strip 2 is reduced, so that the strength of the welded portion 3 is reduced.
  • the crushing width C is 5% or more and 40% or less of the plate thickness
  • the temperature of the welded portion 3 does not vary, and the width of the bond portion 4 to be formed may be constant. it can. Therefore, long-time annealing treatment is not required due to the large part of the bond portion 4.
  • FIG. 5 are schematic diagrams showing the upset amount of the steel pipe 1 according to the present embodiment.
  • the ends are pressed against each other and abutted against each other.
  • a point separated by a predetermined distance X in the plate width direction from one end of the steel strip 2 before being welded is P1
  • the other end of the steel strip 2 is A point separated from the end by a predetermined distance Y in the plate width direction is P2.
  • the distance Z between the welded P1 and P2 is the distance X and the distance Y. Will be shorter than the total length.
  • the length (X + Y ⁇ Z) of the end portion shortened by the pressing in the direction in which the end portions are pressed against each other is referred to as the upset amount.
  • the upset amount at each end is preferably 20% or more and 30% or less with respect to the plate thickness of the steel strip 2.
  • the molten metal discharge amount is reduced. Therefore, the amount of the molten metal remaining in the bond portion 4 increases, and as a result, the width of the bond portion 4 increases.
  • the upset amount is larger than 30% of the plate thickness, the end portion is excessively crushed.
  • Examples of the welding method in the present embodiment include high-density energy welding such as resistance welding, laser beam welding, and electron beam welding.
  • resistance welding is preferable, and high-frequency welding (high-frequency resistance) among resistance welding is preferable.
  • Welding is preferred.
  • High-frequency welding is resistance welding in which welding is performed by resistance heat generated by high-frequency current while applying pressure to the welded joint.
  • high frequency contact resistance welding or high frequency induction resistance welding may be used.
  • the welding temperature is preferably 1200 ° C or higher and 1700 ° C or lower. If the welding temperature is too high, the amount of molten metal produced during welding increases, and the width of the bond portion 4 becomes wider. Further, when the welding temperature is 1200 ° C. or lower, the amount of the molten metal becomes small, and a part of the welded portion 3 which is not welded is generated. With the welding temperature as described above, welding can be performed such that the width of the bond portion 4 is 0.2% or more and 1.2% or less of the plate thickness of the steel strip 2.
  • the said welding may weld the edge parts of one steel strip 2 or a steel plate, and may form a steel pipe, and may join the edge parts of two or more steel strips 2 or steel plates. May be
  • the metal structure of the bond portion 4 may be hard martensite. Therefore, the workability of the welded portion 3 is reduced.
  • spheroidizing annealing treatment is preferably performed.
  • the spheroidizing annealing treatment means annealing the high carbon steel at a temperature near the A1 transformation point so that the carbide contained in the high carbon steel is spheroidized and precipitated. By performing the spheroidizing annealing treatment, the high carbon steel becomes soft and the workability is improved.
  • the bond part 4 can transform the martensite structure into a ferrite structure in which spherical carbides are dispersed by a spheroidizing annealing treatment. As a result, the workability of the bond portion 4 is improved.
  • the steel pipe provided with the welded portion 3 in which the width of the bond portion 4 is 0.2% or more and 1.2% or less of the plate thickness of the steel strip 2 without having to perform the diameter reduction rolling step. 1 can be manufactured.
  • the steel pipe 1 contains C (carbon): 0.4 mass% or more and 1.5 mass% or less, P: 0.03 mass% or less, and Cu: 0.3 mass% or less, with the balance being Fe and unavoidable impurities. Consists of.
  • the steel pipe 1 contains a specific component in a specific amount, has a small amount of impurities, and has high hardness and cleanliness, and thus has excellent rolling fatigue life.
  • the steel pipe 1 contains 0.4 mass% or more and 1.5 mass% or less C. That is, the steel pipe 1 is a high carbon welded steel pipe. C is the most basic element in carbon steel, and the hardness and the amount of carbide of the steel pipe greatly vary depending on the content. When the content of C is 0.4% by mass or more, the strength required for use as a mechanical component such as a bearing can be obtained. Further, when the C content is 0.6% by mass or more, the effect of obtaining the strength required for use as a mechanical component such as a bearing becomes remarkable.
  • the spheroidizing annealing treatment can impart sufficient workability to the welded portion 3.
  • P P (phosphorus) is an element that reduces the ductility and toughness of a steel pipe.
  • the P content in the steel pipe 1 is preferably 0.03 mass% or less, more preferably 0.02 mass% or less, and further preferably 0.01 mass% or less.
  • the steel pipe 1 may not contain P.
  • the P content is 0.03 mass% or less, it is possible to prevent the toughness of the former austenite grain boundary in the steel pipe 1 from increasing after quenching and to prevent the rolling fatigue resistance of the steel pipe 1 after heat treatment from decreasing. ..
  • Cu Cu (copper) is an element that improves the surface properties of the steel strip and the steel pipe obtained from the steel strip by improving the peelability of the oxide scale produced in the steel strip during hot rolling.
  • the Cu content in the steel pipe 1 is preferably 0.3 mass% or less.
  • the steel pipe 1 may not contain Cu. When the Cu content is 0.3 mass% or less, fine cracks are less likely to occur on the surface of the steel strip 2 and the steel pipe 1 obtained from the steel strip 2.
  • the steel pipe 1 is a range in which the problem of efficiently manufacturing a high carbon welded steel pipe can be solved, and in addition to the above-mentioned components, Si, Mn, Cr, S, Al, Cr, Mo, Ti, Nb, V, And B may be further included.
  • the total content of these components is preferably 7.2 mass% or less with respect to the steel pipe 1, and 6.0 mass%.
  • the content is more preferably below, and even more preferably 4.0% by mass or less.
  • Si Si silicon
  • Si is an element that delays the precipitation of carbides in the spheroidizing annealing treatment.
  • the Si content in the steel pipe 1 is preferably 2.0% by mass or less. Since the content of Si is not too large as described above, precipitation of spherical carbides is not hindered in the spheroidizing annealing treatment, and the spheroidizing annealing treatment proceeds efficiently.
  • Mn manganese Mn (manganese) suppresses the ferrite transformation of the steel in the steel pipe in the cooling process after quenching when the steel pipe is heated by quenching, and becomes a martensite-centered structure even at a relatively slow cooling rate. It is an element that enhances hardenability.
  • the Mn content in the steel pipe 1 is preferably 0.1% by mass or more and 2.0% by mass or less, and more preferably 0.5% by mass or more and 1.5% by mass or less. As described above, when the Mn content is 0.1% by mass or more, deterioration of the hardenability of the steel pipe 1 is prevented, and high-temperature generation of pearlite and upper bainite is generated in the steel of the steel pipe 1 during cooling. It is possible to prevent an object from being formed. Thereby, when the steel pipe 1 is used as a bearing, the hardness required for the bearing can be obtained. Further, when the Mn content is 2.0% by mass or less, it is possible to prevent the ferrite from being hardened and hindering the roll forming during pipe making.
  • S sulfur
  • S is an element that affects the workability and rolling fatigue life of steel pipes.
  • the S content in the steel pipe 1 is preferably 0.02 mass% or less.
  • S produces MnS-based non-metallic inclusions.
  • the generation of MnS-based non-metallic inclusions may be the starting point of fatigue fracture due to stress concentration, which may reduce the rolling fatigue life.
  • the content of S is 0.02 mass% or less, the generation of MnS-based nonmetallic inclusions can be suppressed, and the reduction of rolling contact fatigue life can be prevented.
  • the S content is 0.02 mass% or less, it is possible to suppress the generation of secondary shear planes and tongues in the slit coil end face shape before pipe making, and to form a suitable welded portion.
  • Al Al (aluminum) is an element that is used as a deoxidizing agent for molten steel and also has an action of fixing N (nitrogen).
  • the Al content in the steel pipe 1 is preferably 0.2 mass% or less, and more preferably 0.005 mass% or more and 0.05 mass% or less.
  • the content of Al is 0.005 mass% or more, the effect of fixing N becomes more remarkable.
  • the Al content is 0.2% by mass or less, the cleanliness of steel can be prevented from being impaired, and as a result, the reduction of rolling fatigue life due to fatigue fracture can be prevented. Further, it is possible to prevent the deterioration of the surface quality of the steel strip 2.
  • (Cr) Cr (chromium) is an element effective in improving hardenability.
  • the Cr content in the steel pipe 1 is preferably 5.0% by mass or less, more preferably 2.0% by mass or less, and 0.5% by mass or more and 1.6% by mass or less. It is more preferably 0.8% by mass or more and 1.5% by mass or less.
  • the Cr content is 0.2 mass% or more, the hardenability of the steel pipe 1 can be further improved.
  • the content of Cr is 5.0 mass% or less, the content of Cr is not too large, and thus it is possible to prevent the workability from being deteriorated.
  • Mo mobdenum
  • Mo mobdenum
  • the Mo content in the steel pipe 1 is preferably 0.5 mass% or less.
  • the content of Mo is not too large, i.e., 0.5% by mass or less, when the steel strip 2 is annealed, it tends to be softened, and the roll formability at the time of pipe forming can be prevented from deteriorating.
  • Nb Nb (niobium) is an element that forms very hard Nb.Ti-based carbide particles in the steel in the cooling process after casting of steel and contributes to improvement of wear resistance.
  • the Nb content in the steel pipe 1 is preferably 0.5 mass% or less.
  • Ti titanium
  • Ti titanium
  • the content of Ti in the steel pipe 1 is preferably 0.3 mass% or less.
  • V vanadium
  • vanadium is an element effective in improving the toughness of steel.
  • the V content in the steel pipe 1 is preferably 1.5 mass% or less.
  • B (boron) is an element that improves the hot workability of the steel pipe and is effective in preventing cracks during hot rolling. However, if the steel pipe contains an excessive amount of B, the hot workability is rather deteriorated. Therefore, the content of B in the steel pipe 1 is preferably 0.01% by mass or less.
  • the method for manufacturing the steel pipe 1 in the present embodiment includes a step of forming the steel strip 2 and a step of welding the ends of the steel strip 2 to each other. These steps are similar to the roll forming process and the welding process described above, respectively.
  • the steel pipe 1 includes a step of bending the steel plate or the steel strip 2 to bring the ends of the steel plate or the steel strip 2 into contact with each other, and a bond portion 4 formed by melting the end portion by heating.
  • the steel pipe for bearing according to the present embodiment includes the steel pipe 1 according to the present embodiment described above.
  • the steel pipe 1 has a high hardness and cleanliness because it contains a specific component in a specific amount and contains a small amount of impurities. Therefore, the steel pipe 1 can be suitably used as a bearing steel pipe.
  • a steel pipe according to an aspect of the present invention is a steel plate or steel strip containing C: 0.4 mass% or more and 1.5 mass% or less, P: 0.03 mass% or less, and Cu: 0.3 mass% or less.
  • the end portions are formed by welding, the end portions are welded at a welding temperature of 1200 ° C. or higher and 1700 ° C. or lower, and the width of the bond portion formed by melting the end portions by heating is: It is 0.2% or more and 1.2% or less with respect to the plate thickness of the above steel plate or steel strip.
  • the C content in the steel pipe may be 0.6% by mass or more and 1.2% by mass or less.
  • the steel pipe which concerns on 1 aspect of this invention has Si: 2.0 mass% or less, Mn: 0.1 mass% or more and 2.0 mass% or less, S: 0.02 mass% or less, and Al: 0.2 mass%. At least one of the following conditions may be further satisfied.
  • the steel pipe according to one aspect of the present invention may further satisfy at least one condition of Cr: 5.0 mass% or less and Mo: 0.5 mass% or less.
  • At least 1 of Ti 0.3 mass% or less, Nb: 0.5 mass% or less, V: 1.5 mass% or less, and B: 0.01 mass% or less. The two conditions may be further satisfied.
  • the above welding may be high frequency welding.
  • the steel pipe according to one aspect of the present invention may be formed by heating the ends and pressing each other so that the crushing amount is 20% or more and 30% or less with respect to the plate thickness.
  • the end is crushed at a corner, and the length corresponding to the crushed portion in the plate width direction of the steel plate or the steel strip is equal to the plate thickness.
  • it is 5% or more and 40% or less, and the smaller one of the angles formed by the plane including the upper surface or the lower surface of the steel plate or steel strip and the surface formed by the crushing is 20 degrees or more and 60 degrees. It may be the following.
  • the steel pipe according to one aspect of the present invention may be a round pipe, a square pipe, or a deformed pipe.
  • a bearing steel pipe according to an aspect of the present invention includes the steel pipe according to any one of the above.
  • a method for manufacturing a steel pipe according to one aspect of the present invention includes a steel sheet containing C: 0.4 mass% or more and 1.5 mass% or less, P: 0.03 mass% or less, and Cu: 0.3 mass% or less.
  • a method for manufacturing a steel pipe in which ends of steel strips are welded to each other is formed by bending the steel plate or steel strip to bring the ends into contact with each other, and by melting the ends by heating.
  • the step of welding with is
  • Hot rolling coils (steel strips) having a thickness of 6.0 mm were manufactured by heating the slabs of various steels in Table 1 to 1250 to 1300 ° C. and hot rolling. The obtained hot-rolled coils were pickled, and all steel types were annealed at 750 ° C. for 10 hours. Then, the hot rolled coil was slit in the longitudinal direction and roll-formed. After roll forming, the end faces of the hot-rolled coils facing each other were high-frequency welded at various welding temperatures (heating temperatures), crushing amounts, and upset amounts to manufacture steel pipes having a diameter of 34 mm and a thickness of 6.0 mm. The steel pipe after welding was annealed. In the annealing treatment, after soaking at 700 ° C., air cooling was performed.
  • the bond portion which is the width of the bond portion
  • the bond portion was measured at 5 locations every 100 mm, and the widest portion was defined as the maximum bond width.
  • spherical carbide area ratio In order to obtain the spherical carbide area ratio, a photograph was taken at a maximum bond width of 20 locations using a scanning electron microscope (SEM) at a magnification of 5000 times. The spherical carbide area area of the bond portion in the photograph was measured and the spherical carbide area ratio was determined by averaging the measured values of the spherical carbide area.
  • SEM scanning electron microscope
  • Table 2 shows the results of evaluating the amount of spherical carbide precipitation in steel pipes manufactured under various welding conditions in each steel type.
  • Table 2 the steel types according to the comparative examples are underlined.
  • the area ratio of the spherical carbides was 90% or more of f, and a good amount of the precipitated spherical carbides was obtained.
  • the good precipitation amount of the spherical carbide as in the example of the present invention was not obtained. The reason for this is discussed below.
  • the bond width is wide refers to the case where the bond width is wider than 72 ⁇ m, which is 1.2% of the plate thickness 6 mm of the steel strip.
  • the spherical carbide precipitation rate was less than 90%. Therefore, the precipitation amount of spherical carbide was evaluated as x.
  • the area ratio of the spherical carbide was 90% or more of f, and a good amount of the precipitated spherical carbide was obtained. That is, a bond part having good workability was obtained by the annealing treatment for 50 hours.
  • the area ratio of the spherical carbides was less than 90% of f, and sufficient precipitation of the spherical carbides could not be obtained by the annealing treatment for 50 hours. That is, it was suggested that in the steel pipe according to the comparative example, a longer annealing treatment was required in order to obtain a bond part having good workability.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

L'invention concerne un tuyau en acier à haute teneur en carbone (1) avec lequel il est possible de raccourcir le temps de recuit d'une soudure (3). Le tuyau en acier (1) est formé par soudage des bords d'une plaque d'acier ou bande d'acier (2) contenant 0,4 à 1,5 % en masse de C, 0,03 % en masse ou moins de P et 0,3 % en masse ou moins de Cu. Les bords sont soudés à une température de soudage de 1 200 à 1 700 °C, et la largeur d'une partie de liaison (4) est de 0,2 à 1,2 % par rapport à l'épaisseur de la plaque d'acier ou bande d'acier (2).
PCT/JP2019/042661 2018-11-13 2019-10-30 Tuyau d'acier, tuyau d'acier pour palier et procédé de production de tuyau d'acier WO2020100603A1 (fr)

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JP2018-212955 2018-11-13
JP2018212955A JP7196549B2 (ja) 2018-11-13 2018-11-13 鋼管の製造方法

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WO2020100603A1 true WO2020100603A1 (fr) 2020-05-22

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0368740A (ja) * 1989-08-03 1991-03-25 Kobe Steel Ltd 白色層幅の均一な厚肉小径電縫鋼管およびその製造方法
JPH11197850A (ja) * 1998-01-16 1999-07-27 Sumitomo Metal Ind Ltd 電縫鋼管とその製造方法
JP2008208417A (ja) * 2007-02-26 2008-09-11 Jfe Steel Kk 熱処理用電縫溶接鋼管およびその製造方法
JP2009197327A (ja) * 2008-01-21 2009-09-03 Jfe Steel Corp 中空部材およびその製造方法
JP2013234348A (ja) * 2012-05-08 2013-11-21 Jfe Steel Corp 耐疲労特性に優れた自動車部品用電縫溶接鋼管およびその製造方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0368740A (ja) * 1989-08-03 1991-03-25 Kobe Steel Ltd 白色層幅の均一な厚肉小径電縫鋼管およびその製造方法
JPH11197850A (ja) * 1998-01-16 1999-07-27 Sumitomo Metal Ind Ltd 電縫鋼管とその製造方法
JP2008208417A (ja) * 2007-02-26 2008-09-11 Jfe Steel Kk 熱処理用電縫溶接鋼管およびその製造方法
JP2009197327A (ja) * 2008-01-21 2009-09-03 Jfe Steel Corp 中空部材およびその製造方法
JP2013234348A (ja) * 2012-05-08 2013-11-21 Jfe Steel Corp 耐疲労特性に優れた自動車部品用電縫溶接鋼管およびその製造方法

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