EP4206338A1 - Tuyau en acier soudé par résistance électrique - Google Patents

Tuyau en acier soudé par résistance électrique Download PDF

Info

Publication number
EP4206338A1
EP4206338A1 EP20951521.2A EP20951521A EP4206338A1 EP 4206338 A1 EP4206338 A1 EP 4206338A1 EP 20951521 A EP20951521 A EP 20951521A EP 4206338 A1 EP4206338 A1 EP 4206338A1
Authority
EP
European Patent Office
Prior art keywords
weld
less
base material
material portion
microstructure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20951521.2A
Other languages
German (de)
English (en)
Other versions
EP4206338A4 (fr
Inventor
Kensuke Nagai
Tatsuo Yokoi
Hideto KAWANO
Shunichi Kobayashi
Shuji Iwamoto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Publication of EP4206338A1 publication Critical patent/EP4206338A1/fr
Publication of EP4206338A4 publication Critical patent/EP4206338A4/fr
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • 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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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 an electric resistance welded steel pipe.
  • trunk line pipes that are used in long-range transportation pipelines are designed according to the standards of the American Petroleum Institute (API).
  • API American Petroleum Institute
  • Patent Documents 1 and 2 as a material for 5L-X56 or higher-grade high-strength electric resistance welding steel pipes in terms of API standard, high strength hot rolled steel sheets having excellent toughness in the base material portion and the weld and having a sheet thickness of 18 mm or more in consideration of improvement in the toughness of the circumferential welds of electric resistance welding steel pipes are disclosed.
  • Patent Documents 1 and 2 the high-strength hot rolled steel sheets need to contain boron (B) as a chemical composition and have a problem in that the material properties of the steel pipe are likely to be uneven.
  • Patent Document 3 discloses a technique for improving the toughness of a base material portion and the electric resistance welding portion in an electric resistance welded steel pipe for a line pipe that does not contain B.
  • Patent Document 3 a tempering treatment performed after pipe making is premised, and there is a problem in that the number of manufacturing steps increases.
  • An object of the present invention is to provide an electric resistance welded steel pipe that does not contain B, does not require a tempering step after pipe making, has high strength, and has excellent toughness in a base material portion and a weld.
  • the present invention has been made to solve the above-described problems and relates to the following electric resistance welded steel pipe.
  • an electric resistance welded steel pipe that does not contain B, does not require a tempering step after pipe making, has high strength, and has excellent toughness in a base material portion and a weld.
  • FIG. 1 is a view showing a relationship between a development degree of a texture and a Charpy absorbed energy at -20°C of a weld.
  • the present inventors have studied a method for obtaining an electric resistance welded steel pipe having high strength and having excellent toughness in both a base material portion and a weld and obtained the following findings.
  • the electric resistance welded steel pipe according to the present embodiment has a base material portion and a weld, the base material portion has a predetermined chemical composition, when the wall thickness of the base material portion is represented by tB, the microstructure at a (1/4)tB position from the outer surface of the base material portion is composed of, by area%, 10% to 50% of bainite, 50% to 90% polygonal ferrite, and 1% or less of a remainder in microstructure, the average grain size at the (1/4)tB position is 20 ⁇ m or less, when the wall thickness of the weld is represented by tS, the microstructure at a (1/4)tS position from the outer surface of the weld is composed of, by area%, 70% to 90% of bainite, polygonal ferrite, and 1% or less of a remainder in microstructure, the average grain size at the (1/4)tS position from the outer surface of the weld is 15 ⁇ m or less, the development degree of ⁇ 001 ⁇ on the butting surface of the weld
  • the Charpy impact absorbed energy of the base material portion and the Charpy impact absorbed energy of the weld at -20°C are each 150 J or more, the yield stress is 360 to 600 MPa, and the tensile strength is 465 to 760 MPa.
  • the electric resistance welded steel pipe according to the present embodiment has a steel sheet that serves as the base material portion and a weld (electric resistance welding portion) that is provided in a butting portion of the steel sheet and extends in the longitudinal direction of the steel sheet.
  • the chemical composition becomes substantially the same in the base material portion and in the weld except for C.
  • C there are cases where the C content in the weld and the C content in the base material portion differ due to decarburization during electric resistance welding.
  • the C is an effective element for increasing the strength of steel.
  • the C content is set to 0.040% or more.
  • the C content is preferably 0.060% or more.
  • the C content is set to 0.120% or less.
  • the C content is preferably 0.100% or less.
  • the Si content is set to 0.03% or more.
  • the Si content is preferably 0.05% or more.
  • the Si content exceeds 0.50%, a Si oxide is formed in the weld, and the toughness deteriorates. Therefore, the Si content is set to 0.50% or less.
  • the Si content is preferably 0.45% or less.
  • Mn is an effective element for ensuring the strength and toughness of the base material portion.
  • the Mn content is set to 0.50% or more.
  • the Mn content is preferably 0.70% or more.
  • the Mn content is set to 2.00% or less.
  • the Mn content is preferably 1.60% or less.
  • P is an element that is contained as an impurity and affects the toughness of steel.
  • the P content exceeds 0.020%, intergranular embrittlement is caused in the base material portion and the weld, and the toughness significantly deteriorates. Therefore, the P content is set to 0.020% or less.
  • the P content is preferably as small as possible and may be 0%. However, the substantial lower limit in mass-produced steel is 0.002%.
  • S is an element that is contained as an impurity.
  • the S content exceeds 0.003%, a coarse sulfide is formed, and the toughness deteriorates. Therefore, the S content is set to 0.003% or less.
  • the S content is preferably as small as possible and may be 0%. However, the substantial lower limit in mass-produced steel is 0.0003%.
  • Al is an effective element as a deoxidizing material.
  • the Al content exceeds 0.060%, a large amount of anAl oxide is formed, and the toughness in the base material portion and the weld deteriorates. Therefore, the Al content is set to 0.060% or less.
  • the Al content is preferably 0.050% or less.
  • the Al content may be 0%, but the Al content is preferably 0.010% or more in order to obtain the deoxidizing effect.
  • Ti is a nitride-forming element and is an element that contributes to the refinement of crystal grains through forming a nitride.
  • the Ti content is set to 0.005% or more.
  • the Ti content is preferably set to 0.010% or more.
  • the Ti content exceeds 0.030%, the toughness significantly deteriorates due to the formation of a coarse carbide. Therefore, the Ti content is set to 0.030% or less.
  • the Ti content is preferably set to 0.025% or less.
  • Nb is an element that forms a carbide, a nitride, and/or a carbonitride and contributes to increase in the strength of steel.
  • Nb is an element having an effect of improving the toughness of the base material portion of the steel pipe by expanding the non-recrystallization rolling temperature range.
  • the Nb content is set to 0.005% or more.
  • the Nb content is preferably set to 0.010% or more.
  • the Nb content exceeds 0.050%, a large amount of a Nb-based carbonitride is formed, and the toughness of the base material and the weld deteriorates. Therefore, the Nb content is set to 0.050% or less.
  • the Nb content is preferably set to 0.040% or less.
  • N is an element that forms a nitride, refines the crystal grain of steel, and improves toughness. In order to obtain these effects, the N content is set to 0.0010% or more.
  • the N content exceeds 0.0080%, a large amount of a nitride is formed, which degrades the toughness of the base material portion and the weld. Therefore, the N content is set to 0.0080% or less.
  • O is an element that is contained as an impurity and affects the toughness of steel.
  • the O content exceeds 0.005%, a large amount of an oxide is formed, and the toughness of the base material portion and the weld significantly deteriorates. Therefore, the O content is set to 0.005% or less.
  • the O content is preferably as small as possible and may be 0%. However, the substantial lower limit in mass-produced steel is 0.001%.
  • the basic chemical composition of the electric resistance welded steel pipe according to the present embodiment is that the above-described elements are contained and the remainder is Fe and an impurity.
  • Cu, Ni, Cr, Mo, V, W, Ca, and REM may be further contained within ranges to be described below. However, these elements are not essentially contained, and thus the lower limits thereof are all 0%.
  • impurity refers to a component that is incorporated from a raw material such as an ore or a scrap or from a variety of causes in manufacturing steps during the industrial manufacturing of steel and is allowed to be contained to an extent that the characteristics of the electric resistance welded steel pipe according to the present embodiment are not adversely affected.
  • Cu is an effective element for increasing strength without degrading toughness. Therefore, Cu may be contained as necessary. In the case of obtaining the above-described effect, the Cu content is preferably set to 0.010% or more.
  • the Cu content exceeds 0.500%, cracking is likely to occur during the heating and the welding of steel pieces. Therefore, even in a case where Cu is contained, the Cu content is set to 0.500% or less.
  • Ni is an effective element for improving toughness and strength. Therefore, Ni may be contained as necessary. In the case of obtaining the above-described effect, the Ni content is preferably set to 0.010% or more.
  • the Ni content exceeds 0.500%, weldability deteriorates. Therefore, even in a case where Ni is contained, the Ni content is set to 0.500% or less.
  • Cr is an element that improves the strength of steel through precipitation hardening. Therefore, Cr may be contained as necessary. In the case of obtaining this effect, the Cr content is preferably set to 0.010% or more.
  • the Cr content exceeds 0.500%, hardenability improves, which makes the proportion of bainite in the structure increase excessively and degrades toughness. Therefore, even in a case where Cr is contained, the Cr content is set to 0.500% or less.
  • Mo is an element that improves hardenability, at the same time, forms a carbonitride, and contributes to increase in the strength of steel. Therefore, Mo may be contained as necessary. In the case of obtaining the above-described effect, the Mo content is preferably set to 0.010% or more.
  • the Mo content exceeds 0.500%, the strength of steel becomes higher than necessary, and the toughness deteriorates. Therefore, even in a case where Mo is contained, the Mo content is set to 0.500% or less.
  • V 0% to 0.100%
  • V is an element that forms a carbide and/or a nitride and contributes to increase in the strength of steel. Therefore, V may be contained as necessary. In the case of obtaining the above-described effect, the V content is preferably set to 0.001% or more.
  • V content exceeds 0.100%, a number of precipitates are formed, and toughness deteriorates. Therefore, even in a case where V is contained, the V content is set to 0.100% or less.
  • W is an element that forms a carbide and contributes to increase in the strength of steel. Therefore, W may be contained as necessary. In the case of obtaining the above-described effect, the W content is preferably set to 0.100% or more.
  • the W content exceeds 0.500%, a number of carbides are formed, and toughness deteriorates. Therefore, even in a case where W is contained, the W content is set to 0.500% or less.
  • Ca is an element that suppresses the formation of elongated MnS by forming a sulfide and contributes to improvement in toughness or lamella tear resistance. Therefore, Ca may be contained as necessary. In the case of obtaining the above-described effect, the Ca content is preferably set to 0.0010% or more.
  • the Ca content exceeds 0.0050%, a large amount of CaO is formed in the weld, and the toughness of the weld deteriorates. Therefore, even in a case where Ca is contained, the Ca content is set to 0.0050% or less.
  • REM is an element that suppresses the formation of elongated MnS by forming a sulfide and contributes to improvement in toughness or lamella tear resistance. Therefore, REM may be contained as necessary. In the case of obtaining the above-described effect, the REM content is preferably set to 0.0010% or more.
  • the REM content exceeds 0.0050%, the number of REM oxides increases, and toughness deteriorates. Therefore, even in a case where REM is contained, the REM content is set to 0.0050% or less.
  • REM refers to a total of 15 lanthanoid elements
  • the REM content refers to the total content of these elements.
  • the electric resistance welded steel pipe according to the present embodiment has a chemical composition in which the essential elements are contained, optional elements contained as necessary, and the remainder is Fe and an impurity in the base material portion and the weld.
  • Ceq is a value that serves as an index of hardenability and is represented by the following formula (i).
  • i a required strength cannot be obtained.
  • Ceq exceeds 0.53, the strength becomes excessively high, and the toughness deteriorates. Therefore, Ceq is set to 0.20 to 0.53.
  • Ceq C + Mn / 6 + Ni + Cu / 15 + Cr + Mo + V / 5
  • each element symbol in the formulae represents the content (mass%) of each element contained in steel and is regarded as zero in a case where the corresponding element is not contained.
  • the toughness of the weld (electric resistance welding portion) deteriorates.
  • the reason therefor is considered that the melting point of a MnSi-based oxide that is formed during welding becomes high, the MnSi-based oxide is likely to remain in the weld and acts as a starting point of brittle fracture, which degrades the toughness.
  • Mn/Si (the ratio of mass% of Mn to mass% of Si) is set to 2.0 to 16.0.
  • Microstructure at 1/4 position of wall thickness from outer surface composed of, by area%, 10% to 50% of bainite, 50% to 90% of polygonal ferrite, and 1% or less of remainder in microstructure
  • the control of the microstructure of the base material portion becomes important. Specifically, the microstructure of the base material portion needs to contain, by area%, 10% to 50% of bainite and 50% to 90% of polygonal ferrite, and the structure other than bainite and polygonal ferrite (remainder in microstructure) needs to be 1% or less.
  • the concept of "bainite" in the electric resistance welded steel pipe according to the present embodiment includes granular bainite, upper bainite, and lower bainite.
  • the microstructure except bainite is mainly polygonal ferrite.
  • Polygonal ferrite also includes quasi-polygonal ferrite.
  • the total of bainite and polygonal ferrite is 99% or more and may be 100%.
  • one or more of pearlite, pseudo- pearlite, and residual austenite are contained in some cases. Even when these are present, the characteristics of the steel pipe are not affected as long as the total area ratio is 1% or less.
  • the remainder in microstructure may be 0%.
  • the microstructure at a 1/4 position of the wall thickness from the outer surface of the base material portion (a position of (1/4)tB in the thickness direction from the outer surface of the base material portion when the wall thickness of the base material portion is represented by tB) is the above-described range.
  • the reason for limiting the microstructure at the (1/4)tB position from the outer surface of the base material portion is that the structure at this position is a representative structure of the base material portion of the steel pipe.
  • the surface of the electric resistance welded steel pipe refers to the outer surface, not the inner surface.
  • the proportion (area%) of each structure can be measured by the following method.
  • a test piece for microstructure observation is collected from the base material such that a cross section parallel to the pipe axis direction and the thickness direction becomes an observed section.
  • the collected test piece for microstructure observation is wet-polished to mirror-finish the observed section, and then the observed section is Nital-etched to expose the microstructure.
  • the structure is observed using an optical microscope at a magnification of 500 times, each structure is identified from a microstructure photograph, and the area ratio of each structure is measured.
  • Each structure has the following characteristics, and each structure is identified based on these characteristics.
  • Polygonal ferrite that is formed by transformation accompanying atomic diffusion has no internal structure in the grains, and the grain boundaries are straight lines or arc-shaped.
  • bainite has an internal structure, has grain boundaries with an acicular shape, and has a clearly different structure from polygonal ferrite. Therefore, polygonal ferrite and bainite are determined by the grain boundary shape and the presence or absence of an internal structure from a microstructure photograph obtained using an optical microscope after the etching with Nital.
  • a microstructure in which no internal structure clearly appears and the grain boundary shape is acicular is referred to as quasi-polygonal ferrite, but counted as polygonal ferrite in the present embodiment.
  • pearlite and pseudo-pearlite are etched black and thus can be clearly distinguished from polygonal ferrite.
  • the total area ratio of residual austenite and M-A constituent can be calculated by performing LePera etching on the same test piece for microstructure observation and performing image analysis on a structure photograph obtained with an optical microscope.
  • the area ratio of M-A constituent (martensite-austenite constituent) can be obtained by subtracting the area ratio of residual austenite from the total area ratio of residual austenite and M-A constituent (martensite-austenite constituent).
  • measurement is performed on a 300 ⁇ 300 ⁇ m (300 square micrometers) region with a measurement step size of 0.5 ⁇ m.
  • the average grain size at the (1/4)tB position from the outer surface of the base material portion needs to be set to 20 ⁇ m or less.
  • the average grain size exceeds 20 ⁇ m, sufficient toughness cannot be ensured.
  • the Charpy impact absorbed energy at -20°C becomes 150 J or more.
  • the average grain size is measured by the following method.
  • the microstructure at the (1/4)tB position from the outer surface is observed using an SEM-EBSD device.
  • the measurement is performed on a 500 ⁇ m ⁇ 500 ⁇ m region under a condition of a step size of 0.3 ⁇ m.
  • a region that is surrounded by high-angle grain boundaries with an inclination of 15° or more is defined as a crystal grain
  • the equivalent circle diameter of the crystal grain is defined as the crystal grain size
  • the average grain size is calculated by the AREA FRACTION method.
  • regions with an equivalent circle diameter of 0.25 ⁇ m or less are excluded from the calculation of the average grain size.
  • Microstructure at 1/4 position of wall thickness from outer surface being composed of, by area%, 70% to 90% of bainite, polygonal ferrite, and 1 % or less of remainder in microstructure
  • the microstructure of the weld is controlled by reheating the weld and then cooling the weld with water from the outer surface side.
  • a precipitate that contributes to increase in strength is less likely to be formed. Therefore, in the electric resistance welded steel pipe according to the present embodiment, from the viewpoint of ensuring the strength of the weld, the microstructure at a 1/4 position of the wall thickness from the outer surface (a position of (1/4)tS in the thickness direction from the outer surface of the weld when the wall thickness of the weld is represented by tS) needs to be mainly bainite.
  • the area ratio of bainite needs to be 70% to 90%.
  • the area ratio of bainite When the area ratio of bainite is less than 70%, the strength of the weld decreases. In addition, when the area ratio of bainite exceeds 90%, the hardness becomes too high, and the toughness of the weld deteriorates. In addition, when the area ratio of polygonal ferrite is excessive, it is difficult to obtain a required strength. Therefore, the area ratio of polygonal ferrite is set to 30% or less. The total area ratio of bainite and polygonal ferrite is 99% or more and may be 100%.
  • one or more of pearlite, pseudo- pearlite, and residual austenite are contained in some cases. Even when these are present, the characteristics of the steel pipe are not affected as long as the area ratio is 1 % or less.
  • the remainder in microstructure may be 0%.
  • the area ratio of each structure in the microstructure of the weld is obtained as described below.
  • a test piece for microstructure observation is collected such that a cross section that includes the weld and is perpendicular to the pipe circumferential direction and parallel to the thickness direction becomes an observed section.
  • the test piece for microstructure observation is wet-polished to mirror-finish the observed section, and the area ratio of each structure is measured in the same manner as for the base material portion using an optical microscope and EBSD at, as an observation position, a position 200 to 300 ⁇ m away in a direction perpendicular to the thickness direction from the butting surface. Since the butting surface is decarburized, etching makes it possible to specify the butting surface.
  • the refinement of the microstructure is important together with the above-described control.
  • the average grain size at the 1/4 position of the wall thickness from the outer surface ((1/4)tS position from the outer surface) of the weld is controlled to 15 ⁇ m or less. When the average grain size exceeds 15 ⁇ m, the toughness deteriorates.
  • the average grain size is obtained by the following method.
  • the microstructure at the (1/4)tS position from the outer surface is observed using an SEM-EBSD device.
  • the measurement is performed on a 500 ⁇ m ⁇ 500 ⁇ m region under a condition of a step size of 0.3 ⁇ m.
  • a region that is surrounded by high-angle grain boundaries with an inclination of 15° or more is defined as a crystal grain
  • the equivalent circle diameter of the crystal grain is defined as the crystal grain size
  • the average grain size is calculated by the AREA FRACTION method.
  • regions with an equivalent circle diameter of 0.25 ⁇ m or less are excluded from the calculation of the average grain size.
  • An electric resistance welded steel pipe is obtained by forming a steel sheet into a tubular shape and joining both end portions by contact bonding while heating the end surfaces of the steel sheet by high-frequency induction heating or electric resistance heating. At this time, compressive stress is applied in the circumferential direction. That is, high-temperature hot working is performed on heated portions. This high-temperature hot working develops the texture. This texture remains even when the weld is heated after welding.
  • the development degree of ⁇ 001 ⁇ on the butting surface is set to 1.5 or less. While there is no need to limit the lower limit of the development degree, the development degree becomes 1.0 in structures where the crystal orientations are random, and thus the lower limit may be set to 1.0.
  • the texture is measured as described below.
  • a test piece is collected from the weld, a surface perpendicular to the pipe axis direction is polished and Nital-etched to expose the butting surface, and the test piece is cut and polished such that the butting surface becomes a measurement surface, thereby producing a test piece for texture measurement. Crystal orientations are measured using an SEM-EBSD device on this test piece.
  • the measurement position is the wall thickness center ((1/2)tS) position of the cross section.
  • a range where decarburization occurs is determined as the butting surface.
  • the measurement range is set to a 1 mm ⁇ 1 mm or more region, and the step size is set to 3.0 ⁇ m.
  • the development degree of ⁇ 001 ⁇ parallel to the measurement surface is calculated from the obtained data using OIM Data Analysis, which is analysis software.
  • the calculated development degree becomes 1.0 in a case where the crystal orientations are random, and this value becomes larger as texture develops more.
  • HV10 refers to "hardness symbol” in a case where a Vickers hardness test is performed with a test force set to 98 N (10 kgf) (JIS Z 2244: 2009).
  • the average hardness of the base material portion is preferably 250 HV10 or less.
  • a test piece is collected from the weld such that the butting surface becomes a measurement surface, and measurement is performed at 5 points in a (1/4)tS portion from the outer surface of the measurement surface using a Vickers hardness meter with a load of 10 kgf. Out of 3 points excluding the maximum value and the minimum value from the 5 points, the highest value is regarded as the maximum hardness of the weld, and, if this maximum hardness is 250 Hv or less, the hardness of the weld is determined to be 250 Hv or less.
  • the average hardness of the base material portion is obtained as described below.
  • a test piece is collected such that a surface (C cross section) including two axes of the wall thickness direction axis and the circumferential direction axis becomes a measurement surface, and measurement is performed at 5 points in a (1/4)tB portion from the outer surface of the measurement surface and at 5 points in a (3/4)tB portion from the outer surface using the Vickers hardness meter with a load of 10 kgf.
  • a value obtained by averaging the obtained values is defined as the average hardness of the base material portion.
  • the yield stress that is measured from the base material portion is set to 360 to 600 MPa, and the tensile strength is set to 465 to 760 MPa.
  • the electric resistance welded steel pipe according to the present embodiment has a Charpy impact absorbed energy of 150 J or more at -20°C in both the base material portion and the weld. In this case, sufficient toughness can be ensured even when the electric resistance welded steel pipe is used in cold regions.
  • the above-described mechanical properties can be evaluated by a tensile test and a Charpy test.
  • the tensile test and the Charpy test are performed according to API 5CT of the American Petroleum Institute.
  • the test piece is collected such that the butting surface (abutment surface) is specified in a C cross section by etching and a notch is formed in the wall thickness direction in the butting surface.
  • the wall thickness of the base material portion of the electric resistance welded steel pipe there is no particular limitation provided regarding the wall thickness of the base material portion of the electric resistance welded steel pipe according to the present embodiment.
  • the wall thickness is preferably 10.0 mm or more in order to increase the internal pressure from the viewpoint of improving the transportation efficiency of fluids passing through the pipe.
  • the upper limit of the wall thickness of the electric resistance welded steel pipe is generally 25.4 mm.
  • the pipe diameter is preferably 300 to 670 mm with an assumption of a line pipe.
  • the electric resistance welded steel pipe according to the present embodiment can obtain the effects as long as the electric resistance welded steel pipe has the above-described characteristics regardless of the manufacturing method.
  • the electric resistance welded steel pipe according to the present embodiment can be manufactured by, for example, a manufacturing method including the following steps.
  • the casting step steel having the above-described chemical composition is melted in a furnace, and then a slab is produced by casting.
  • the casting method is not particularly limited and may be a method such as normal continuous casting, casting by an ingot method, or, additionally, thin slab casting.
  • the slab is heated up to a temperature range of Ac3 point or higher and hot-rolled.
  • the heating temperature before the hot rolling is preferably 1000°C or higher.
  • the heating temperature is more preferably 1100°C or higher.
  • the heating temperature is preferably set to 1250°C or lower.
  • the reduction ratio in the recrystallization region is set to 2.0 or more and the reduction ratio in the non-recrystallization region is set to 2.0 or more.
  • the reduction ratio in the non-recrystallization region is set to 2.0 or more, it becomes possible to set the average grain size of the base material portion to 20 ⁇ m or less.
  • the boundary between the recrystallization region and the non-recrystallization region is approximately 900°C to 950°C although depending on the composition of the steel.
  • the hot rolling finishing temperature (finish rolling finishing temperature) is preferably set to 770°C or higher.
  • the hot rolling finishing temperature is lower than 770°C, the hot rolling becomes dual phase rolling, and the toughness of the base material portion deteriorates.
  • the finish rolling start temperature is preferably 900°C to 950°C in order to ensure toughness by rolling in the non-recrystallization region.
  • the steel sheet after the hot rolling step is cooled to a temperature range of 500°C to 650°C in terms of the surface temperature such that the average cooling rate at the sheet thickness center portion falls into a range of 10 to 80 °C/sec and coiled in the temperature range.
  • the average cooling rate at the sheet thickness center portion can be calculated by heat transfer calculation from the temperature history of the outer surface.
  • the control of the cooling rate is important.
  • the average cooling rate is slower than 10 °C/sec, ferritic transformation proceeds, and the bainite fraction becomes less than 10%.
  • the average cooling rate exceeds 80 °C/sec, since the cooling rate is too fast, ferritic transformation does not occur, and the bainite fraction exceeds 50%.
  • the cooling stop temperature exceeds 650°C, since ferritic transformation occurs after coiling, the bainite fraction (area%) becomes less than 10%.
  • the cooling stop temperature becomes lower than 500°C, the temperature unevenness during cooling becomes significant, the strength becomes uneven, and the stable production of the electric resistance welded steel pipe according to the present embodiment is not possible.
  • the obtained hot rolled steel sheet is roll-formed, and an electric resistance welded steel pipe is manufactured by electric resistance welding (electric resistance welding or high frequency welding).
  • the end portions of the steel sheet are melted by high-frequency induction heating or electric resistance heating, and both are butted together to be welded.
  • an oxide or the like is formed, and, if the oxide or the like remains as it is, the toughness of the weld is degraded.
  • compressive stress is applied (upset) in the circumferential direction to the weld with a squeeze roll, thereby discharging and removing the oxide.
  • the upset amount can be organized with the absolute value of a change in the circumferential length before and after the welding.
  • the electric resistance welded steel pipe manufacturing method it is important to set the upset amount to 22.0 mm or less (including 0) in order to control the texture.
  • the present inventors found that a decrease in the upset amount makes it possible to control the texture and consequently makes it possible to improve the toughness of the weld. Furthermore, it was found that, in steel pipes having a low S content, when the fluctuation in the upset is minimized by performing measures, such as the tightening of the sheet width and the appropriate adjustment of forming conditions in accordance with facilities for preventing fluctuation of the welding point in a complex manner, the oxide can be stably discharged even when the upset amount is decreased.
  • the weld formed in the electric resistance welding step is heated and then water-cooled from the outer surface side.
  • the weld can be heated by, for example, high-frequency heating.
  • the weld is heated up to a temperature range of 900°C to 1050°C and cooled to a temperature range of 500°C to 680°C by water cooling.
  • This heat treatment heat treatment (heating and cooling) makes it possible to control the microstructure (the fraction of each structure and the average grain size) and hardness (maximum hardness) of the weld within the above-described ranges.
  • the development degree of ⁇ 001 ⁇ on the butting surface does not change.
  • the heating temperature is lower than 900°C, a region where austenite transformation does not occur during the heat treatment remains, whereby the microstructure coarsens, and the toughness deteriorates.
  • the heating temperature exceeds 1050°C, coarse austenite is formed during the heat treatment, whereby the microstructure after the cooling coarsens, and the toughness deteriorates.
  • the cooling stop temperature when the cooling stop temperature is lower than 500°C, the bainite fraction becomes excessive, the maximum hardness of the weld is surpassed, and the toughness deteriorates.
  • the cooling stop temperature exceeds 680°C, coarse pearlite is formed, and the toughness deteriorates.
  • the weld may be cooled to room temperature by air cooling (air cooling).
  • the microstructures at the (1/4)tB positions from the outer surfaces of the base material portions, the average grain sizes at the (1/4)tB positions from the outer surfaces of the base material portions, the microstructures at the (1/4)tS positions from the outer surfaces of the welds, the average grain sizes at the (1/4)tS positions from the outer surfaces of the weld, the development degrees of ⁇ 001 ⁇ at the (1/2)tS positions from the outer surfaces of the butting surfaces of the welds, and the maximum hardness at the (1/4)tS positions of the welds were evaluated by the above-described methods.
  • tensile tests and Charpy tests were performed to evaluate the strengths (yield stress and tensile strength) and toughness (absorbed energies).
  • the tensile tests and the Charpy tests were performed in the above-described manner in accordance with API 5CT of the American Petroleum Institute.
  • the test temperature of the Charpy test was set to -20°C.
  • structures other than polygonal ferrite and bainite were 1% or less of the remainders in microstructure in the microstructures of the base material portions.
  • the microstructures of the welds contained 1% or less of residual austenite as the remainder in microstructure in addition to bainite and polygonal ferrite.
  • 1% or less of pearlite was contained as the remainder in microstructure.
  • No. 21 to No. 49 which were the comparative examples, did not satisfy the characteristics for reasons to be described below.
  • the Ti content exceeded the upper limit of the scope of the present invention.
  • a large amount of a Ti-based carbide was formed, and the toughness of the base material and the weld deteriorated.
  • the Nb content was below the lower limit of the scope of the present invention, and the crystal grain size became large. As a result, the toughness of the base material portion deteriorated.
  • the Nb content exceeded the upper limit of the scope of the present invention.
  • a large amount of a Nb-based carbonitride was formed, and the toughness of the base material and the weld deteriorated.
  • the Mn/Si ratio was below the lower limit of the scope of the present invention. As a result, a MnSi-based oxide having a high melting point remained in the weld, and the toughness of the weld deteriorated.
  • the present disclosure it becomes possible to obtain an electric resistance welded steel pipe having a high strength and excellent toughness in the base material portion and in the weld. Therefore, the present disclosure is highly industrially applicable.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Heat Treatment Of Steel (AREA)
EP20951521.2A 2020-08-28 2020-08-28 Tuyau en acier soudé par résistance électrique Pending EP4206338A4 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2020/032636 WO2022044271A1 (fr) 2020-08-28 2020-08-28 Tuyau en acier soudé par résistance électrique

Publications (2)

Publication Number Publication Date
EP4206338A1 true EP4206338A1 (fr) 2023-07-05
EP4206338A4 EP4206338A4 (fr) 2023-10-25

Family

ID=76310148

Family Applications (1)

Application Number Title Priority Date Filing Date
EP20951521.2A Pending EP4206338A4 (fr) 2020-08-28 2020-08-28 Tuyau en acier soudé par résistance électrique

Country Status (3)

Country Link
EP (1) EP4206338A4 (fr)
JP (1) JP6885524B1 (fr)
WO (1) WO2022044271A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7549285B1 (ja) 2024-02-13 2024-09-11 日本製鉄株式会社 ラインパイプ用電縫鋼管
JP7549286B1 (ja) 2024-02-13 2024-09-11 日本製鉄株式会社 ラインパイプ用電縫鋼管

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0847716A (ja) * 1994-08-05 1996-02-20 Nkk Corp 耐ｈｉｃおよび耐ｓｓｃｃ特性に優れた電縫鋼管の製造方法
JPH08300172A (ja) * 1995-04-28 1996-11-19 Nkk Corp 溶接鋼管の製造方法
JP4978146B2 (ja) 2005-10-18 2012-07-18 Ｊｆｅスチール株式会社 厚手高強度熱延鋼板およびその製造方法
JP4940882B2 (ja) 2005-10-18 2012-05-30 Ｊｆｅスチール株式会社 厚手高強度熱延鋼板およびその製造方法
WO2013027779A1 (fr) * 2011-08-23 2013-02-28 新日鐵住金株式会社 Tube d'acier soudé par résistance électrique à paroi épaisse et procédé de fabrication de ce dernier
JP5979373B2 (ja) * 2011-12-08 2016-08-24 Ｊｆｅスチール株式会社 低温靭性に優れる電縫鋼管の製造方法
KR20160078600A (ko) * 2014-12-24 2016-07-05 주식회사 포스코 확관성이 우수한 파이프용 열연강판 및 그 제조방법
WO2017163987A1 (fr) 2016-03-22 2017-09-28 新日鐵住金株式会社 Tube en acier soudé par résistance électrique pour canalisation
CN109072379B (zh) * 2016-07-06 2020-11-06 日本制铁株式会社 干线管用电阻焊钢管
JP7206793B2 (ja) * 2018-10-22 2023-01-18 日本製鉄株式会社 ラインパイプ用電縫鋼管、及び、ラインパイプ用熱延鋼板
WO2020170333A1 (fr) * 2019-02-19 2020-08-27 日本製鉄株式会社 Tuyau en acier soudé par résistance électrique destiné à un tuyau de canalisation
KR102630980B1 (ko) * 2019-08-23 2024-01-30 닛폰세이테츠 가부시키가이샤 라인 파이프용 전봉 강관

Also Published As

Publication number Publication date
EP4206338A4 (fr) 2023-10-25
JPWO2022044271A1 (fr) 2022-03-03
JP6885524B1 (ja) 2021-06-16
WO2022044271A1 (fr) 2022-03-03

Similar Documents

Publication Publication Date Title
CN111094610B (zh) 钢管和钢板
EP3042976B1 (fr) Tôle d'acier pour tube de canalisation à paroi épaisse et à haute résistance mécanique ayant d'excellentes caracteristiques de résistance à la corrosion et à l'affaissement, et une ductilité aux basses températures, ainsi que tube de canalisation
EP1473376B1 (fr) Tole d'acier haute resistance et procede de production
EP2036995B1 (fr) Tuyau en acier à haute résistance présentant une excellente dureté à basse température pour tuyau de revetement, tole en acier à haute résistance pour tuyau de revetement et procédé pour les fabriquer
RU2518830C1 (ru) Горячекатаный стальной лист и способ его изготовления
EP2799575B1 (fr) Feuille d'acier laminée à chaud à haute résistance et son procédé de fabrication
JP5748032B1 (ja) ラインパイプ用鋼板及びラインパイプ
EP2395122A1 (fr) Tube d'acier à haute résistance pour utilisation à basse température, présentant, au niveau des zones affectées par la chaleur du soudage, des qualités supérieures de résistance au flambage et de ténacité
KR101795979B1 (ko) 전봉 용접 강관
CN110462080B (zh) 耐酸性管线管用高强度钢板及其制造方法和使用耐酸性管线管用高强度钢板的高强度钢管
EP2942415A1 (fr) Tôle d'acier résistant à l'abrasion qui présente une excellente ténacité à basse température ainsi qu'une certaine résistance à la fragilisation par l'hydrogène, et procédé de fabrication de cette dernière
EP2980250A1 (fr) Tôle d'acier résistant à l'abrasion qui présente une certaine ténacité à basse température et procédé de fabrication de cette dernière
CN104937125B (zh) 高强度管线钢管用热轧钢板
EP2902519A1 (fr) Tuyau en acier soudé par résistance électrique
JP2008101242A (ja) 耐ｈｉｃ特性に優れたラインパイプ用高強度鋼板およびその製造方法
EP3375900A1 (fr) Tube en acier soudé par résistance électrique pour canalisation
CN112752857B (zh) 耐酸性管线管用高强度钢板及其制造方法及使用耐酸性管线管用高强度钢板的高强度钢管
JP5768603B2 (ja) 高一様伸び特性を備え、かつ溶接部低温靱性に優れた高強度溶接鋼管、およびその製造方法
JP2012031509A (ja) 高一様伸び特性を備えた高強度低降伏比鋼、その製造方法、および高強度低降伏比溶接鋼管
EP3428299A1 (fr) Tuyau en acier électrosoudé pour tuyau de canalisation
WO2015151468A1 (fr) Matériau en acier pour tuyaux de canalisation hautement déformables ayant des caractéristiques de vieillissement après déformation et caractéristiques anti-hic supérieures, procédé de fabrication de ce dernier et tuyau en acier soudé
EP4206338A1 (fr) Tuyau en acier soudé par résistance électrique
CN115298340B (zh) 耐酸管线用高强度钢板及其制造方法以及使用耐酸管线用高强度钢板的高强度钢管
CN114846163B (zh) 钢板和钢管
CN115210396A (zh) 钢管和钢板

Legal Events

Date Code Title Description
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE

PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE

17P Request for examination filed

Effective date: 20221214

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

A4 Supplementary search report drawn up and despatched

Effective date: 20230921

RIC1 Information provided on ipc code assigned before grant

Ipc: C21D 9/46 20060101ALI20230915BHEP

Ipc: C22C 38/28 20060101ALI20230915BHEP

Ipc: C22C 38/26 20060101ALI20230915BHEP

Ipc: C22C 38/16 20060101ALI20230915BHEP

Ipc: C22C 38/14 20060101ALI20230915BHEP

Ipc: C22C 38/12 20060101ALI20230915BHEP

Ipc: C22C 38/08 20060101ALI20230915BHEP

Ipc: C22C 38/04 20060101ALI20230915BHEP

Ipc: C22C 38/02 20060101ALI20230915BHEP

Ipc: C21D 8/02 20060101ALI20230915BHEP

Ipc: C21D 1/42 20060101ALI20230915BHEP

Ipc: C21D 1/18 20060101ALI20230915BHEP

Ipc: C21D 1/02 20060101ALI20230915BHEP

Ipc: C22C 38/58 20060101ALI20230915BHEP

Ipc: C22C 38/00 20060101ALI20230915BHEP

Ipc: C21D 9/50 20060101ALI20230915BHEP

Ipc: C21D 9/08 20060101ALI20230915BHEP

Ipc: C21D 8/10 20060101AFI20230915BHEP

DAV Request for validation of the european patent (deleted)
DAX Request for extension of the european patent (deleted)