WO2018139672A1 - Tuyau en acier pour composants de dessous de caisse d'automobiles et composant de dessous de caisse d'automobiles - Google Patents

Tuyau en acier pour composants de dessous de caisse d'automobiles et composant de dessous de caisse d'automobiles Download PDF

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Publication number
WO2018139672A1
WO2018139672A1 PCT/JP2018/002959 JP2018002959W WO2018139672A1 WO 2018139672 A1 WO2018139672 A1 WO 2018139672A1 JP 2018002959 W JP2018002959 W JP 2018002959W WO 2018139672 A1 WO2018139672 A1 WO 2018139672A1
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steel pipe
content
cementite
steel
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PCT/JP2018/002959
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English (en)
Japanese (ja)
Inventor
孝聡 福士
坂本　真也
勇次 荒井
卓磨 川本
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新日鐵住金株式会社
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Publication of WO2018139672A1 publication Critical patent/WO2018139672A1/fr

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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

Definitions

  • the present invention relates to a steel pipe for automobile underbody parts and an automobile underbody part using the same.
  • Patent Document 1 discloses a seamless steel pipe that has excellent cold workability, hardenability, toughness, and torsional fatigue strength, and is optimal as a hollow shaft material for an integrally formed hollow drive shaft.
  • Patent Document 2 discloses a steel material for automobile structural members that is excellent in delayed fracture resistance.
  • Patent Document 3 discloses an electric-welded steel pipe excellent in workability and fatigue characteristics after quenching, suitable for materials such as automobile parts and machine structural parts.
  • Patent Document 1 an ERW steel pipe having improved fatigue characteristics after quenching by controlling the form of Ca-based inclusions such as oxides and sulfides present in the base material and welds of the ERW steel pipe. Is obtained.
  • materials for automobile undercarriage parts are required to have both excellent cold workability during production and high notch tensile strength during use.
  • Patent Documents 1 to 3 do not consider notch tensile properties at all and leave room for improvement.
  • the present invention has been made to solve the above problems, and the gist of the present invention is a steel pipe for automobile underbody parts and an automobile underbody part described below.
  • each element symbol in the above formula represents the content of each element contained in the steel.
  • the chemical composition is mass%, Ni: 0.1 to 1.0%, Cu: 0.1 to 1.0%, Cr: 0.3 to 1.5%, Nb: 0.02 to 0.2%, and V: 0.03-0.2%, Containing one or more selected from The steel pipe for automobile undercarriage parts according to the above (1).
  • the chemical composition is mass%, Mg: 0.0001 to 0.02%, and REM: 0.001 to 0.02%, Containing one or more selected from The steel pipe for automobile undercarriage parts according to the above (1) or (2).
  • a steel pipe excellent in cold workability can be obtained.
  • the part manufactured using the steel pipe which concerns on this invention has high notch tensile strength. Therefore, the steel pipe is suitable for automobile undercarriage parts.
  • C 0.35-0.60% Since C has an effect of improving the strength of steel, it is an element to be contained according to the required strength. In order to ensure the strength as an automobile underbody part, it is necessary to contain 0.35% or more of C. On the other hand, if the C content exceeds 0.60%, the toughness decreases. Therefore, the C content is set to 0.35 to 0.60%.
  • the C content is preferably 0.40% or more, and preferably 0.50% or less.
  • Si 0.25 to 1.0%
  • Si is an element that has an effect on deoxidation of steel and enhances hardenability and strengthens steel. In order to acquire said effect, it is necessary to contain Si 0.25% or more. However, when the Si content exceeds 1.0%, coarse inclusions of Si are formed, and the notch tensile strength is reduced. Therefore, the Si content is set to 0.25 to 1.0%. In terms of notch tensile strength, the Si content is preferably low, and is preferably 0.50% or less.
  • Mn 0.05 to 2.0% Mn, like Si, is effective in deoxidizing steel, and is an element that enhances hardenability and strengthens steel. In order to acquire said effect, it is necessary to contain Mn 0.05% or more. However, if the Mn content exceeds 2.0%, coarse MnS is formed, and the notch tensile strength is reduced. Therefore, the Mn content is set to 0.05 to 2.0%. In terms of notch tensile strength, the Mn content is preferably low, and is preferably 1.5% or less.
  • P 0.1% or less P is contained as an impurity in the steel. P is an element that decreases the toughness by reducing the bonding force of the grain boundaries. Therefore, the P content is 0.1% or less. The P content is preferably 0.05% or less.
  • S 0.0050% or less S is contained as an impurity in the steel. If the S content exceeds 0.0050%, the required notch tensile strength cannot be ensured. Therefore, the S content is 0.0050% or less.
  • the S content is preferably 0.0030% or less, and more preferably 0.0020% or less.
  • Al 0.005 to 0.1%
  • Al is an element necessary for deoxidation of steel.
  • Al combines with MnS to form composite inclusions, thereby detoxifying MnS and contributing to the improvement of notch tensile properties.
  • it is necessary to contain Al 0.005% or more.
  • the Al content is set to 0.005 to 0.1%.
  • the Al content is preferably 0.01% or more, and preferably 0.05% or less.
  • N 0.01% or less N is contained as an impurity in the steel. If the N content exceeds 0.01%, the toughness decreases. Therefore, the N content is 0.01% or less. The N content is preferably 0.005% or less.
  • O 0.01% or less O (oxygen) is contained as an impurity in the steel. If the O content exceeds 0.01%, the toughness decreases. Therefore, the O content is 0.01% or less.
  • the O content is preferably 0.005% or less.
  • Mo 0.20 to 1.5%
  • Mo has the effect
  • Mo it is necessary to contain Mo 0.20% or more.
  • the Mo content exceeds 1.5%, the effect is saturated and the cost is increased. Therefore, the Mo content is 0.20 to 1.5%.
  • the Mo content is preferably 0.25% or more, and preferably 0.50% or less.
  • Ti 0.01 to 0.05% Ti has the effect of suppressing coarsening of crystal grains and improving toughness. Further, Ti binds to MnS to form composite inclusions, thereby detoxifying MnS and contributing to the improvement of notch tensile properties. In order to acquire said effect, it is necessary to contain Ti 0.01% or more. However, if the Ti content exceeds 0.05%, coarse inclusions are formed. Therefore, the Ti content is set to 0.01 to 0.05%. The Ti content is preferably 0.02% or more, and preferably 0.04% or less.
  • B 0.0001 to 0.01% B is combined with Mo and thus has an effect of improving hardenability and improving the strength of steel. In order to acquire said effect, it is necessary to contain B 0.0001% or more. However, if the B content exceeds 0.01%, B precipitates and the effect of improving hardenability is reduced. Therefore, the B content is set to 0.0001 to 0.01%.
  • the B content is preferably 0.0005% or more, and preferably 0.003% or less.
  • Ni 0 to 1.0%
  • Ni has an effect of improving the strength of the base material, and may be contained as necessary. However, if the Ni content exceeds 1.0%, the effect is saturated and the cost is increased. Therefore, the Ni content is 1.0% or less.
  • the Ni content is preferably 0.5% or less. In order to obtain the above effect, the Ni content is preferably 0.1% or more.
  • Cu 0 to 1.0% Since Cu has the effect of improving the strength of the base material, it may be contained as necessary. However, if the Cu content exceeds 1.0%, the effect is saturated and the cost is increased. Therefore, the Cu content is 1.0% or less. The Cu content is preferably 0.5% or less. In order to acquire said effect, it is preferable that Cu content is 0.1% or more.
  • Cr 0 to 1.5% Since Cr has an effect of improving hardenability, it may be contained as necessary. However, if the Cr content exceeds 1.5%, the effect is saturated and the cost increases. Therefore, the Cr content is 1.5% or less.
  • the Cr content is preferably 1.0% or less. In order to acquire said effect, it is preferable that Cr content is 0.3% or more.
  • Nb 0 to 0.2% Since Nb has an effect of refining crystal grains and improving the strength of the base material, it may be contained as necessary. However, when the Nb content exceeds 0.2%, the effect is saturated and the cost is increased. Therefore, the Nb content is 0.2% or less. The Nb content is preferably 0.1% or less. In order to acquire said effect, it is preferable that Nb content is 0.02% or more.
  • V 0 to 0.2%
  • V has an effect of improving the strength of the base material, and may be contained as necessary. However, when the V content exceeds 0.2%, the effect is saturated and the cost is increased. Therefore, the V content is 0.2% or less.
  • the V content is preferably 0.1% or less. In order to obtain the above effect, the V content is preferably 0.03% or more.
  • Mg and REM both form oxides in the molten steel, have the effect of improving the cleanliness of the steel by deoxidation, and contribute to the improvement of notch tensile properties. Further, since it functions as a carbonitride formation nucleus, it has an effect of suppressing the formation of coarse carbonitride when appropriately finely dispersed. Therefore, you may contain 1 type, or 2 or more types of these elements as needed.
  • the content of each element is as described above.
  • the content of each element is preferably 0.01% or less, and more preferably 0.0050% or less.
  • REM refers to a total of 17 elements of Sc, Y, and lanthanoid
  • the content of REM refers to the total content of these elements.
  • a lanthanoid it is industrially added in the form of misch metal.
  • the balance is Fe and impurities.
  • impurities are components that are mixed due to various factors of raw materials such as ores and scraps and manufacturing processes when steel is industrially manufactured, and are allowed within a range that does not adversely affect the present invention. Means something.
  • each element symbol in the above formula represents the content of each element contained in the steel.
  • Al and Ti have the effect of detoxifying MnS by combining with MnS to form composite inclusions.
  • the side value in the formula (i) is preferably 45.0 or less, and more preferably 30.0 or less.
  • each element symbol in the above formula represents the content of each element contained in the steel.
  • Si, Mo, and B are elements that enhance hardenability. Therefore, in order to increase the strength of the steel and improve the notch tensile properties, each element must satisfy the above formula (ii) in addition to satisfying the above range.
  • 450 is practically the upper limit.
  • the right side value of the formula (ii) is preferably 75.0 or less, and is preferably 50.0 or less. More preferably.
  • the steel pipe according to the present invention has a metal structure in which the area ratio of cementite is 25 to 70% and the spheroidization ratio of cementite is 70% or more.
  • the area ratio of cementite is less than 25%, sufficient notch tensile strength may not be obtained.
  • the area ratio of cementite exceeds 70%, as will be described later, even if cementite is spheroidized, it is hard and processability deteriorates.
  • the area ratio of cementite is preferably 30% or more, and more preferably 35% or more. Moreover, the area ratio of cementite is preferably 65% or less, and more preferably 60% or less. In the above metal structure, the balance is preferably ferrite.
  • the spheroidization rate of cementite is preferably 75% or more.
  • the “spheroidization rate of cementite” refers to the total area of all cementite when cementite particles having an aspect ratio of 3.0 or less are used as spheroidized cementite. , Means the ratio of the total area of spheroidized cementite.
  • the area ratio and spheroidization ratio of cementite are calculated by the following methods, respectively.
  • a specimen for observing the structure is cut out from the steel pipe sample so that the position of the thickness 1/4 of the cross section perpendicular to the longitudinal direction of the steel pipe becomes the observation surface.
  • the above observation surface is mirror-polished, it undergoes nital corrosion to reveal a metal structure.
  • the area ratio of cementite is calculated
  • the area ratio of all cementite is obtained by observing the observation surface at a magnification of 2000 using a scanning electron microscope (SEM). Further, in the same field of view, the area ratio of spheroidized cementite having an aspect ratio of 3.0 or less is obtained. The aspect ratio is obtained by elliptically approximating cementite by image analysis and dividing the major axis length by the minor axis length. Then, the spheroidizing ratio of the cementite is calculated by dividing the area ratio of the spheroidized cementite by the area ratio of all the cementites obtained in the same field of view.
  • the steel pipe according to the present invention includes, for example, a seamless steel pipe and an electric resistance steel pipe. There are no particular restrictions on the production conditions.
  • the seamless steel pipe can be manufactured, for example, by the following method.
  • ⁇ Melting and casting> For melting and casting, a method performed by a general steel pipe manufacturing method can be used, and the casting may be ingot casting or continuous casting. Moreover, you may cast in the shape of the round billet for pipe making by round CC.
  • Hot working such as forging, drilling and rolling is performed.
  • processes such as forging and partial rolling for forming the circular billet are not necessary.
  • rolling is performed using a mandrel mill or a plug mill. Desirable conditions for hot working such as piercing and rolling are as follows.
  • the billet may be heated to such an extent that hot piercing with a piercing and rolling mill is possible, but a desirable temperature range is 1000 to 1250 ° C.
  • a desirable temperature range is 1000 to 1250 ° C.
  • the finishing temperature should be 900 ° C or higher. Is desirable.
  • the electric resistance welded steel pipe can be manufactured, for example, by the following method.
  • the obtained slab is hot-rolled, and further cold-rolled as necessary to produce a steel plate having a predetermined thickness.
  • the rolled steel sheet may be wound in a coil shape.
  • ⁇ Pipe making> The obtained steel sheet is roll-formed and subjected to high-frequency welding to produce an electric resistance welded steel pipe. You may heat-process with respect to a welding part as needed.
  • the steel pipe obtained by the above method may be cold worked for the purpose of improving the dimensional accuracy as necessary.
  • the cold working method is not particularly limited as long as it can uniformly process a steel pipe, for example, cold rolling called a so-called cold drawing machine or cold pilger mill using a perforated die and a plug. It is industrially advantageous to use a machine.
  • spheroidized cementite grows by setting the average cooling rate after heating to 1 ° C./s or less.
  • the average cooling rate exceeds 1 ° C./s, a part of the re-dissolved cementite may be deposited in a layer shape to form a pearlite structure.
  • the steel pipe manufactured by the above method has the above-described metal structure, it is excellent in cold workability.
  • the heating temperature at the time of quenching is not particularly limited, but it is preferable to set the temperature to Ac 3 points + 50 ° C. Also, the heating time is not particularly limited, but it is desirable that the soaking time is 5 minutes or more.
  • the cooling rate during quenching if the average cooling rate at the central portion of the wall thickness is less than 10 ° C./s, sufficient strength cannot be obtained.
  • the cooling method is not particularly limited as long as it is a method of performing accelerated cooling, but when cooling cracks occur after cooling depending on the shape of the component, it is preferable to perform oil cooling in order to reduce the cooling rate.
  • the tempering temperature is not particularly limited, but is preferably 150 to 300 ° C.
  • the area ratio of all cementite was determined by observing the observation surface at a magnification of 2000 times using SEM. Furthermore, in the same visual field, the area ratio of spheroidized cementite having an aspect ratio of 3.0 or less was determined. Then, the spheroidization rate of cementite was calculated by dividing the area ratio of spheroidized cementite by the area ratio of all cementite obtained in the same field of view.
  • the hardness of each test material was measured for evaluation of cold workability. Specifically, the Vickers hardness was measured at the 1/4 thickness position using the above-mentioned specimen for observing the structure. The test force in the hardness measurement was 9.8N. In the present invention, when the hardness is 240 HV or less, it is determined that the cold workability is excellent.
  • a notched tensile test piece having the shape shown in FIG. 1 was cut out from each test material after the tempering treatment, and a tensile test was performed using the test piece.
  • the unit of the dimension shown in FIG. 1 is mm.
  • the notch tensile strength was calculated
  • the value of notch tensile strength becomes 1440 Mpa or more, it shall be excellent in a notch tensile characteristic.
  • Test No. Reference numerals 1 to 10 are examples of the present invention that satisfy all the provisions of the present invention. As can be seen from Table 1, the hardness is 240 HV or less, excellent cold workability, and after quenching and tempering treatment, show notch tensile strength of 1470 MPa or more, resulting in excellent notch tensile properties. It was.
  • test No. which is a comparative example. 11 and 12
  • the chemical composition satisfied the provisions of the present invention, the spheroidizing annealing conditions were inadequate, so the spheroidizing rate of cementite was lowered and the cold workability was deteriorated. .
  • test no. No. 15 has a high Mn content.
  • No. 16 had a high S content, and in both cases, the median value in the formula (i) was less than the lower limit value, resulting in inferior notch tensile properties.
  • test no. 18 was inferior in notch tensile properties because the median value in the formula (i) was less than the lower limit.
  • a steel pipe excellent in cold workability can be obtained.
  • the part manufactured using the steel pipe which concerns on this invention has high notch tensile strength. Therefore, the steel pipe is suitable for automobile undercarriage parts.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
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  • Manufacturing & Machinery (AREA)
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Abstract

L'invention concerne un tuyau en acier destiné à des composants de dessous de caisse d'automobiles qui a une composition chimique qui contient, en % en masse, de 0,35 % à 0,60 % de C, de 0,25 % à 1,0 % de Si, de 0,05 % à 2,0 % de Mn, 0,1 % ou moins de P, 0,0050 % ou moins de S, de 0,005 % à 0,1 % d'Al, 0,01 % ou moins de N, 0,01 % ou moins d'O, de 0,20 % à 1,5 % de Mo, de 0,01 % à 0,05 % de Ti, de 0,0001 % à 0,01 % de B, de 0 % à 1,0 % de Ni, de 0 % à 1,0 % de Cu, de 0 % à 1,5 % de Cr, de 0 % à 0,2 % de Nb, de 0 % à 0,2 % de V, de 0 % à 0,02 % de Mg et 0 % à 0,02 % de REM, le reste étant constitué de Fe et d'impuretés, tout en vérifiant [5,0 ≤ Al × Ti/(Mn × S) × 10 ≤ 60,0] et [2,0 ≤ 3 × Si × Mo × B × 10 4]. Le tuyau en acier pour composants de dessous de caisse d'automobiles de l'invention a une structure métallique, le rapport de surface de la cémentite étant de 25 % à 70 % et le taux de sphéroïdisation de la cémentite étant de 70 % ou plus.
PCT/JP2018/002959 2017-01-30 2018-01-30 Tuyau en acier pour composants de dessous de caisse d'automobiles et composant de dessous de caisse d'automobiles WO2018139672A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113388779A (zh) * 2021-05-21 2021-09-14 鞍钢股份有限公司 1.5GPa级超高强高塑性高扩孔DH钢板及制备方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001131702A (ja) * 1999-11-04 2001-05-15 Nippon Steel Corp 加工性に優れた冷間鍛造用電縫鋼管とその製造方法
JP2003328079A (ja) * 2002-05-14 2003-11-19 Nippon Steel Corp 加工性に優れた冷間鍛造用鋼管とその製造方法。
WO2016013205A1 (fr) * 2014-07-25 2016-01-28 新日鐵住金株式会社 Tuyau en acier faiblement allié pour puits de pétrole

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001131702A (ja) * 1999-11-04 2001-05-15 Nippon Steel Corp 加工性に優れた冷間鍛造用電縫鋼管とその製造方法
JP2003328079A (ja) * 2002-05-14 2003-11-19 Nippon Steel Corp 加工性に優れた冷間鍛造用鋼管とその製造方法。
WO2016013205A1 (fr) * 2014-07-25 2016-01-28 新日鐵住金株式会社 Tuyau en acier faiblement allié pour puits de pétrole

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113388779A (zh) * 2021-05-21 2021-09-14 鞍钢股份有限公司 1.5GPa级超高强高塑性高扩孔DH钢板及制备方法
CN113388779B (zh) * 2021-05-21 2022-07-22 鞍钢股份有限公司 1.5GPa级超高强高塑性高扩孔DH钢板及制备方法

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