WO2015159965A1 - Tôle d'acier laminée à chaud ayant une excellente aptitude à l'écrouissage et une excellente dureté après travail - Google Patents

Tôle d'acier laminée à chaud ayant une excellente aptitude à l'écrouissage et une excellente dureté après travail Download PDF

Info

Publication number
WO2015159965A1
WO2015159965A1 PCT/JP2015/061767 JP2015061767W WO2015159965A1 WO 2015159965 A1 WO2015159965 A1 WO 2015159965A1 JP 2015061767 W JP2015061767 W JP 2015061767W WO 2015159965 A1 WO2015159965 A1 WO 2015159965A1
Authority
WO
WIPO (PCT)
Prior art keywords
less
steel
hot
steel sheet
hardness
Prior art date
Application number
PCT/JP2015/061767
Other languages
English (en)
Japanese (ja)
Inventor
梶原　桂
Original Assignee
株式会社神戸製鋼所
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 株式会社神戸製鋼所 filed Critical 株式会社神戸製鋼所
Priority to MX2016013517A priority Critical patent/MX2016013517A/es
Priority to DE112015001872.7T priority patent/DE112015001872T5/de
Priority to KR1020167028769A priority patent/KR101736019B1/ko
Priority to US15/303,658 priority patent/US20170037496A1/en
Priority to CN201580019843.9A priority patent/CN106232847B/zh
Publication of WO2015159965A1 publication Critical patent/WO2015159965A1/fr

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
    • C22C38/18—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
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/02—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
    • C22C38/04—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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/16—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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B2001/225—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by hot-rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2261/00—Product parameters
    • B21B2261/22—Hardness
    • 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
    • C21D2211/005—Ferrite
    • 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
    • C21D2211/009—Pearlite
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing

Definitions

  • the present invention shows a good cold workability (strong cold workability) during processing that causes extremely high deformation strain locally in cold working, and a heat that shows a predetermined hardness after working. It relates to rolled steel sheets.
  • cold working (cold forging) has advantages of higher productivity than hot working and warm working and good dimensional accuracy and yield of steel materials.
  • the problem in manufacturing parts by such cold working is that in order to ensure the strength of the cold-worked parts to be higher than the expected value, the strength, ie deformation, is inevitably required. It is necessary to use a steel material with high resistance. However, the higher the deformation resistance of the steel material used, the shorter the service life of the cold working mold.
  • This steel material realizes both cold workability and high hardness (high strength) after processing, but is a hot forging material, like the wire rod and bar steel described in Patent Document 1 above.
  • the manufacturing cost is high. Therefore, in order to further reduce the manufacturing cost, it has been studied to produce automobile parts by cold working using hot-rolled steel sheets instead of the conventional hot forging materials.
  • Patent Document 3 For example, a hot-rolled steel sheet for nitriding that has a high surface hardness and a sufficient hardening depth after nitriding has been proposed (see Patent Document 3).
  • a hot-rolled steel sheet having a composition and having a microstructure of 95% or more of a substantially ferritic single-phase structure has been proposed.
  • This hot-rolled steel sheet has excellent dimensional accuracy of a precision punched surface and a stamped surface after processing. Is extremely high in surface hardness and is also excellent in red scale resistance (see Patent Document 4).
  • N is limited to a very low content as a harmful element, and the technical idea is completely different from the hot-rolled steel sheet according to the present invention that actively uses N. It is.
  • the present invention has been made by paying attention to the above circumstances, and its purpose is to show good cold workability (strong cold workability) during working that causes extremely high strain in cold working. It is to provide a hot-rolled steel sheet having a predetermined hardness after processing.
  • a hot-rolled steel sheet excellent in strong cold workability and hardness after processing according to the first invention of the present invention The plate thickness is 3-20mm
  • Ingredient composition is mass%, C: more than 0% and 0.3% or less, Si: more than 0% and 0.5% or less, Mn: 0.2 to 1% P: more than 0% and 0.05% or less, S: more than 0% and 0.05% or less, Al: 0.01 to 0.1%, N: 0.008 to 0.025%,
  • the balance consists of iron and inevitable impurities, Solid solution N: 0.007% or more, and The content of C and N satisfies the relationship of 10C + N ⁇ 3.0
  • the structure is an area ratio with respect to the entire structure, bainitic ferrite: 5% or more, pearlite: less than 20%, the balance: polygonal ferrite, The average grain size of the bainitic ferrite is in the range of 3 to 50 ⁇ m;
  • t is the thickness of the thickness direction
  • Ingredient composition is further mass%, Cr: more than 0% and 2% or less, and Mo: At least one selected from the group consisting of more than 0% and 2% or less Is included.
  • Ingredient composition further Ti: more than 0% and 0.2% or less, Nb: more than 0% and 0.2% or less, and V: At least one selected from the group consisting of more than 0% and 0.2% or less Is included.
  • Ingredient composition is further mass%, B: Over 0% to 0.005% or less Is included.
  • Ingredient composition is further mass%, Cu: more than 0% and 5% or less, Ni: more than 0% and 5% or less, and Co: at least one selected from the group consisting of more than 0% and not more than 5% Is included.
  • Ingredient composition is further mass%, Ca: more than 0% and 0.05% or less, REM: more than 0% and 0.05% or less, Mg: more than 0% and 0.02% or less, Li: more than 0% and 0.02% or less, Pb: more than 0% and 0.5% or less, and Bi: At least one selected from the group consisting of more than 0% and 0.5% or less Is included.
  • a solid solution N amount is ensured, and the C content and the N content have a predetermined relationship.
  • the hot-rolled steel sheet according to the present invention (hereinafter also referred to as “the steel sheet of the present invention” or simply “the steel sheet”) will be described in more detail.
  • the steel sheet of the present invention is common to the hot forging material described in Patent Document 2 above in that the N solid solution amount is ensured and the C content and the N content satisfy a predetermined relationship.
  • the C content is allowed to a higher range
  • the structure is a bainitic ferrite-polygonal ferrite-pearlite double phase structure
  • the bainitic ferrite grains are refined
  • the hardness in the thickness direction The difference is that the distribution is limited within a predetermined range.
  • the steel sheet of the present invention has a thickness of 3 to 20 mm. If the plate thickness is less than 3 mm, rigidity as a structure cannot be secured. On the other hand, if the plate thickness exceeds 20 mm, it is difficult to achieve the tissue form defined in the present invention, and the desired effect cannot be obtained.
  • a preferred plate thickness is 4 to 19 mm.
  • Component composition of the steel sheet of the present invention ⁇ C: more than 0% and 0.3% or less>
  • C is an element that has a great influence on the formation of the structure of a steel sheet, and the structure is bainitic ferrite-polygonal ferrite-pearlite multiphase structure, but bainitic ferrite-polygonal ferrite mainly containing as little pearlite as possible. It is an element whose content needs to be limited in order to form a structure.
  • C is contained excessively, the pearlite fraction in the steel sheet structure increases, and the deformation resistance may be excessive due to work hardening of the pearlite.
  • the C content in the steel sheet is limited to 0.3% or less, preferably 0.25% or less, more preferably 0.2% or less, and particularly preferably 0.15% or less.
  • the content of C is too small, deoxidation during the melting of steel becomes difficult, and it becomes difficult to satisfy the strength and hardness after cold working, so 0.0005% or more, more preferably Is 0.0008% or more, particularly preferably 0.001% or more.
  • Si is an element that needs to be reduced as much as possible in order to increase the deformation resistance of the steel sheet by dissolving in steel. Therefore, the Si content in the steel sheet is 0.5% or less, preferably 0.45% or less, more preferably 0.4% or less, and particularly preferably 0.3% or less in order to suppress an increase in deformation resistance. Restrict to. However, if the Si content is extremely small, deoxidation during melting becomes difficult, and it becomes difficult to satisfy the strength and hardness after cold working, so 0.005% or more, more preferably 0.008% or more, particularly preferably 0.01% or more.
  • Mn is an element having a deoxidizing and desulfurizing action in the steel making process. Furthermore, when the content of N in the steel material is increased, cracks are likely to occur due to dynamic strain aging due to heat generation during processing. On the other hand, Mn improves the workability at that time and has the effect of suppressing cracks. . In order to effectively exhibit these actions, the Mn content in the steel material is 0.2% or more, preferably 0.22% or more, and more preferably 0.25% or more. However, when the Mn content is excessive, the deformation resistance becomes excessive and the structure is not uniform due to segregation. Therefore, the content is set to 1% or less, preferably 0.98% or less, and more preferably 0.95% or less.
  • P is an impurity element inevitably contained in the steel, but if it is contained in ferrite, it segregates at the ferrite grain boundaries and degrades the cold workability. It is an element that causes an increase. Therefore, it is desirable to reduce the P content as much as possible from the viewpoint of cold workability. However, since extreme reduction leads to an increase in steelmaking costs, it is 0.05% or less, preferably in consideration of process capability. 0.03% or less.
  • S is an unavoidable impurity and is an element that precipitates in the form of a film at the grain boundary as FeS and degrades workability. It also has the effect of causing hot brittleness. Therefore, from the viewpoint of improving the deformability, in the present invention, the S content is set to 0.05% or less, preferably 0.03% or less. However, it is industrially difficult to reduce the S content to zero. In addition, since S has an effect of improving machinability, it is recommended to contain 0.002% or more, more preferably 0.006% or more from the viewpoint of improving machinability.
  • Al is an element effective for deoxidation in the steelmaking process.
  • the Al content in the steel material is set to 0.01% or more, preferably 0.015% or more, and more preferably 0.02% or more.
  • the content is 0.1% or less, preferably 0.09% or less, and more preferably 0.08% by mass or less.
  • N is an important element for obtaining a predetermined strength by static strain aging after processing. Therefore, the N content in the steel material is 0.008% or more, preferably 0.0085% or more, and more preferably 0.009% or more. However, if the N content is excessive, in addition to static strain aging, the influence of dynamic strain aging during processing becomes significant, and deformation resistance increases, which is unsuitable. Therefore, 0.025% or less, preferably 0 0.02% or less, more preferably 0.02% or less.
  • Solid solution N amount a predetermined amount of solid solution N in the steel sheet
  • the amount of solute N needs to be 0.007% or more.
  • the amount of solute N becomes excessive, cold workability deteriorates and the amount of solute N fixed to the processing strain increases, and hardness distribution tends to occur in the thickness direction of the hot-rolled sheet.
  • it is preferably 0.03% or less.
  • content of N in steel materials is 0.025% or less, the amount of solute N does not become 0.025% or more substantially.
  • the solid solution N amount in the present invention is an amount obtained by subtracting the amount of all N compounds from the total N amount in the steel material in accordance with JIS G 1228.
  • a practical method for measuring the amount of dissolved N will be exemplified below.
  • the sample material is dissolved in this 10% AA-based electrolyte, and the resulting insoluble residue (N compound) is filtered through a polycarbonate filter having a hole size of 0.1 ⁇ m.
  • the obtained insoluble residue is decomposed by heating in a chip made of sulfuric acid, potassium sulfate and pure copper, and the decomposition product is combined with the filtrate.
  • steam distillation is performed, and the distilled ammonia is absorbed in dilute sulfuric acid.
  • phenol, sodium hypochlorite and sodium pentacyanonitrosyl iron (III) are added to form a blue complex, and the absorbance is measured using an absorptiometer to determine the total N compound amount.
  • the amount of solid solution N can be calculated
  • the content of C and N satisfies the relationship of 10C + N ⁇ 3.0>
  • solid solution C greatly increases deformation resistance and does not contribute much to static strain aging
  • solid solution N promotes static strain aging without significantly increasing deformation resistance. Therefore, the hardness after processing can be increased. Therefore, in the steel material of the present invention, in order to increase the hardness after processing without significantly increasing the deformation resistance during processing, the content of C and the content of N are 10C + N ⁇ 3.0. It is essential to satisfy the relationship, preferably 0.009 ⁇ 10C + N ⁇ 2.8, more preferably 0.01 ⁇ 10C + N ⁇ 2.5, and particularly preferably 0.01 ⁇ 10C + N ⁇ 2.0.
  • a C content and a solute C content are required to some extent, but when 10C + N> 3.0, C and / or N The amount becomes excessive and the deformation resistance becomes excessive.
  • the coefficient of the C content is set to 10 times the coefficient of the N content because the solid solution C has the same content as the solid solution N but the strength in the hot-rolled steel sheet of the present invention. Further, it is considered that the degree of increasing the deformation resistance is about one digit (10 times) larger.
  • the steel of the present invention basically contains the above components, and the balance is iron and inevitable impurities, but the following permissible components can be added as long as the effects of the present invention are not impaired.
  • Cr is an element that has the effect of improving the deformability of steel by increasing the strength of the grain boundaries.
  • Cr is preferably contained in an amount of 0.2% or more. .
  • the content is recommended to be 2% or less, more preferably 1.5% or less, especially 1% or less. Is done.
  • Mo is an element having an action of increasing the hardness and deformability of the steel material after processing. In order to effectively exhibit such action, Mo is 0.04% or more, more preferably 0. It is preferable to contain 0.08% or more. However, if Mo is excessively contained, the cold workability may be deteriorated. Therefore, the content is recommended to be 2% or less, further 1.5% or less, particularly 1% or less.
  • ⁇ Ti more than 0% and 0.2% or less
  • Nb more than 0% and 0.2% or less
  • V at least one selected from the group consisting of more than 0% and 0.2% or less>
  • These elements have a strong affinity for N, coexist with N to form N compounds, refine steel grains, improve the toughness of processed products obtained after cold working, and improve crack resistance. It is an element that has a role to improve. However, even if each element is contained exceeding the upper limit value, the effect of improving the characteristics cannot be obtained. It is recommended that the content of each element is 0.2% or less, further 0.001 to 0.15%, particularly 0.002 to 0.1%.
  • B like Ti, Nb, and V, has a strong affinity with N, and coexists with N to form an N compound, refines the grain of steel, and improves the toughness of the workpiece obtained after cold working And an element having a role of improving crack resistance. Therefore, when the steel sheet of the present invention contains B, the required solid solution N amount can be secured and the strength after cold working can be improved, so the content is 0.005% or less, and further 0 0.0001 to 0.0035%, especially 0.0002 to 0.002% is recommended.
  • ⁇ Cu more than 0% and 5% or less
  • Ni more than 0% and 5% or less
  • Co at least one selected from the group consisting of more than 0% and 5% or less>
  • All of these elements have the effect of strain aging and hardening the steel material, and are effective in improving the strength after processing. In order to effectively exhibit such an action, these elements are preferably contained in an amount of 0.1% or more, and more preferably 0.3% or more. However, if the content of these elements is excessive, the effects of strain aging and hardening of the steel material, and the effect of improving the strength after processing are saturated, and there is a possibility of promoting cracking. In the following, 4% or less, particularly 3% or less is recommended.
  • Ca is an element that spheroidizes sulfide compound inclusions such as MnS, improves the deformability of steel, and contributes to improvement of machinability.
  • Ca is preferably contained in an amount of 0.0005% or more, more preferably 0.001% or more. However, even if contained excessively, the effect is saturated and an effect commensurate with the content cannot be expected. Therefore, 0.05% or less, further 0.03% or less, particularly 0.01% or less is recommended.
  • REM is an element that, like Ca, spheroidizes compound inclusions such as MnS to increase the deformability of steel and contribute to the improvement of machinability.
  • REM is preferably contained in an amount of 0.0005% or more, more preferably 0.001% or more.
  • REM means a lanthanoid element (15 elements from La to Ln), Sc (scandium) and Y (yttrium).
  • it is preferable to contain at least one element selected from the group consisting of La, Ce and Y, more preferably La and / or Ce.
  • Mg is an element that spheroidizes sulfide compound inclusions such as MnS to enhance the deformability of steel and contribute to the improvement of machinability.
  • Mg is preferably contained in an amount of 0.0002% or more, more preferably 0.0005% or more.
  • 0.02% or less is an element that spheroidizes sulfide compound inclusions such as MnS to enhance the deformability of steel and contribute to the improvement of machinability.
  • Mg is preferably contained in an amount of 0.0002% or more, more preferably 0.0005% or more.
  • 0.02% or less, further 0.015% or less, and particularly 0.01% or less is recommended.
  • Li can spheroidize sulfide compound inclusions such as MnS and increase the deformability of steel like Ca, and lower the melting point of Al-based oxides to make them harmless and improve machinability. It is a contributing element.
  • Li is preferably contained in an amount of 0.0002% or more, and more preferably 0.0005% or more. However, even if contained excessively, the effect is saturated and an effect commensurate with the content cannot be expected, so 0.02% or less, further 0.015% or less, and particularly 0.01% or less is recommended.
  • Pb is an effective element for improving machinability.
  • Pb is preferably contained in an amount of 0.005% or more, and more preferably 0.01% or more. However, if it is contained excessively, production problems such as generation of rolling defects occur, so 0.5% or less, further 0.4% or less, particularly 0.3% or less is recommended.
  • Bi is an element effective for improving the machinability like Pb.
  • Bi is preferably contained in an amount of 0.005% or more, and more preferably 0.01% or more.
  • the effect of improving the machinability is saturated even if contained excessively, 0.5% by mass or less, further 0.4% or less, particularly 0.3% or less is recommended.
  • the steel sheet according to the present invention is based on bainitic ferrite-polygonal ferrite pearlite double phase steel, and in particular, controls the bainitic ferrite grain size within a specific range, The hardness distribution in the thickness direction is controlled.
  • the structure of the steel sheet of the present invention is composed of a multiphase structure of bainitic ferrite, polygonal ferrite and pearlite.
  • Bainitic ferrite has the effect of improving the workability during cold working and increasing the hardness after processing while suppressing the occurrence of stretcher strain marks.
  • the area ratio is 5% or more, preferably 10% or more, and more preferably 15% or more.
  • the upper limit of the area ratio of bainitic ferrite in the steel sheet of the present invention is substantially about 90%, preferably 85%, more preferably 80%.
  • the pearlite is 20% or less in area ratio, more preferably 19% or less, still more preferably 18% or less, and particularly preferably 15% or less.
  • the lower limit of the area ratio of pearlite in the steel sheet of the present invention is substantially about 0.5%, preferably 1%.
  • the balance is polygonal ferrite, but the area ratio of polygonal ferrite is preferably 5% or more.
  • a cementite phase is also present in the structure of the steel sheet of the present invention, but the area ratio is at most 1% or less, so in this specification, The area ratios of tick ferrite, polygonal ferrite, and pearlite were defined as those normalized so that the total area ratio of these three phases was 100%.
  • ⁇ Average crystal grain size of the bainitic ferrite in the range of 3 to 50 ⁇ m>
  • the average grain size of bainitic ferrite constituting the bainitic ferrite structure needs to be in the range of 3 to 50 ⁇ m in order to improve the workability of the steel sheet and satisfy the surface properties after processing. . If the bainitic ferrite grains become too fine, the deformation resistance becomes too high, so the average crystal grain size is 3 ⁇ m or more, preferably 4 ⁇ m or more, more preferably 5 ⁇ m or more.
  • the average crystal grain size is 50 ⁇ m or less, preferably 45 ⁇ m or less, more preferably 40 ⁇ m. The following.
  • the hardness distribution in the thickness direction is the surface portion, the thickness t / 4 portion, and the central portion at three locations.
  • HV max the maximum value
  • HV min the minimum value
  • the alloy component of the present invention contains a large amount of solute N, it also affects that the hardness of such a region with a large processing strain increases due to the fixing action of N to the region with a large processing strain. .
  • a hardness distribution in the thickness direction is generated due to a plurality of complicated factors, and variations in strength tend to occur in the thickness direction. Therefore, the steel sheet of the present invention can be obtained by reducing the hardness distribution in the plate thickness direction by subjecting the hot rolled plate to batch annealing under the recommended conditions described later.
  • Polygonal ferrite is defined as ferrite grains having equiaxed crystal grains and an aspect ratio (major axis / minor axis ratio) of less than 2.
  • the average crystal grain size of the bainitic ferrite can be measured as follows. That is, the crystal grain size of bainitic ferrite existing at three locations, the outermost layer portion, the plate thickness 1 ⁇ 4 portion, and the plate thickness center portion, is measured. As for the particle size of one bainitic ferrite particle, the side part in the rolling direction of each measurement point was subjected to nital corrosion, and the corresponding part was photographed with five fields of view with a scanning electron microscope (SEM; magnification 1000 times). The average crystal grain size of ferrite crystal grains was determined based on the center of gravity diameter by image analysis.
  • the steel plate of the present invention may be produced according to any method as long as the raw steel having the above composition can be formed into a desired plate thickness. For example, it can be carried out by preparing a molten steel having the above component composition in a converter under the conditions shown below, slab this by ingot casting or continuous casting, and then rolling it into a hot-rolled steel sheet having a desired thickness. .
  • the N content in the molten steel is adjusted by adding a raw material containing an N compound to the molten steel and / or controlling the converter atmosphere to an N 2 atmosphere during melting in the converter. can do.
  • Heating before hot rolling is performed at 1100 to 1300 ° C. This heating requires high-temperature heating conditions in order to dissolve as much N as possible without producing an N compound.
  • the minimum with a preferable heating temperature is 1100 degreeC, and a more preferable minimum is 1150 degreeC.
  • temperatures exceeding 1300 ° C. are difficult to operate.
  • Hot rolling is performed so that the finish rolling temperature is 880 ° C. or higher. If the finish rolling temperature is too low, ferrite transformation will occur at a high temperature, and the precipitated carbides in ferrite (generically referred to as bainitic ferrite and polygonal ferrite) will become coarse and fatigue strength will deteriorate.
  • the above finish rolling temperature is required.
  • the finish rolling temperature is more preferably 900 ° C. or higher in order to coarsen the austenite grains and increase the grain size of the bainitic ferrite to some extent.
  • the upper limit of the finish rolling temperature is set to 1000 ° C. because it is difficult to secure the temperature.
  • the thickness of the hot-rolled steel sheet of the present invention is 3 to 20 mm.
  • the final reduction ratio of tandem rolling of finish rolling is set to 15% or more.
  • the finish rolling is performed by tandem rolling of 5 to 7 passes, but a pass schedule is set from the viewpoint of control of sheet penetration, and the final rolling reduction is about 12 to 13%.
  • the final rolling reduction is preferably 16% or more, more preferably 17% or more.
  • the higher the final reduction ratio is 20% or 30%, the more effective the crystal grains are refined, but the upper limit is defined to be about 30% from the viewpoint of rolling control.
  • the pearlite transformation is promoted, or when the quenching stop temperature is less than 550 ° C., the bainite transformation is suppressed, both of which are bainitic ferrite-polygonal having a predetermined phase fraction. It becomes difficult to obtain ferrite-pearlite steel, and cold workability and surface quality after processing deteriorate.
  • the quenching stop temperature is 650 ° C. or more, the precipitated carbide in the ferrite is coarsened, and the fatigue strength is deteriorated.
  • the quenching stop temperature is preferably 560 to 640 ° C, more preferably 580 to 620 ° C.
  • the hot rolled plate (hot rolled coil) is subjected to batch annealing under the following conditions. That is, in this batch annealing, in order to suppress generation of surface scale and decarburization, the steel sheet is heated from room temperature to 400 ° C. or higher and Ac1 or lower in an atmosphere of H 2 : 15 to 20% by volume, and then 1 h or longer and 15 h or shorter. Hold and do.
  • the holding temperature and holding time vary depending on the thickness of the hot rolled plate and the size of the coil, but the degree of hardness distribution limit required in correspondence with the required cold working degree, It is appropriately selected depending on the uniformity of the temperature inside the coil.
  • This heat treatment removes residual stress generated during hot rolling, softens it, reduces strain, promotes the release of fixed N elements and spheroidization of carbides, and dissolves fine lamellae in austenite. By doing so, the hardness distribution in the plate thickness direction is reduced.
  • the steel sheet is cooled to 600 ° C. at a rate of 10 ° C./h or less, thereby promoting the spheroidization of the carbide.
  • the cooling is performed at a rate of 15 ° C./h or less from 600 to 400 ° C., in order to stabilize the shape such as coil crushing by uniformly cooling the inside of the coil.
  • cooling can be performed at a high cooling rate (such as about 50 to 100 ° C./h or higher) by water cooling or the like as long as the temperature distribution in the coil can be uniformly cooled.
  • the holding temperature is more preferably 450 to 650 ° C, particularly preferably 500 to 600 ° C.
  • the holding time is more preferably 2 to 14 h, particularly preferably 3 to 12 h.
  • cooling was performed at a cooling rate of 10 ° C./h or less up to 600 ° C., 15 ° C./h or less from 600 to 400 ° C., and water cooling was performed at 400 ° C. or less.
  • the hot-rolled steel sheet was evaluated for the cold workability and the hardness after working as follows.
  • FORGE manufactured by TRANSVALOR
  • FORGE manufactured by TRANSVALOR
  • steel no. 1-2 to 1-6, 2, 3, 7 to 14, and 25 to 28 were all manufactured using the steel types satisfying the requirements of the component composition provisions of the present invention under the recommended production conditions.
  • Invented steel that meets the requirements of the organization regulations. Both cold workability and post-working hardness satisfy the acceptance criteria, and good strong cold during machining that causes extremely high strain in cold working. It was confirmed that a hot-rolled steel sheet having a predetermined hardness (strength) was obtained after the processing while exhibiting the workability.
  • Steel No. 1-1, 1-7 to 1-10, 4 to 6, 15 to 24, and 29 are comparative steels that do not satisfy at least one of the component composition and the structure requirements defined in the present invention, and are strongly cold worked. At least one of the properties and post-processing hardness does not satisfy the acceptance criteria.
  • steel No. 1-1 satisfies the requirements of the component composition, but is not subjected to batch annealing after hot rolling, the hardness distribution in the plate thickness direction is expanded, and at least the cold workability is inferior.
  • steel No. In No. 1-8 although the requirements of the component composition are satisfied, the holding temperature of batch annealing after hot rolling is too high outside the recommended range, and the post-processing hardness is inferior.
  • steel No. 1-10 satisfies the requirements of the component composition, but the holding time of batch annealing after hot rolling is too short outside the recommended range, the hardness distribution in the sheet thickness direction is expanded, and at least strong cold workability Is inferior.
  • steel No. No. 16 steel type k
  • the production conditions are in the recommended range, the N content is too high and at least the strong cold workability is inferior.
  • Steel No. No. 18 (steel type m) has a manufacturing condition in the recommended range, but the Si content is too high, and at least the cold workability is inferior.
  • steel no Although 20 (steel type o) has a production condition in the recommended range, the Mn content is too high and at least the strong cold workability is inferior.
  • steel No. for 24 steel type s
  • the production conditions other than the final rolling reduction during hot rolling are in the recommended range
  • the Al content is too high and at least the cold workability is poor.
  • steel No. Although 29 (steel type x) is in the recommended range of manufacturing conditions, it does not satisfy the requirement of 10C + N ⁇ 3.0, and at least strong cold workability is inferior.
  • the hot-rolled steel sheet of the present invention exhibits good workability during cold working and exhibits a predetermined hardness after working, and is particularly used for various parts for automobiles, such as transmission parts such as gears and cases. Useful as steel.

Abstract

La présente invention concerne une tôle d'acier laminée à chaud qui présente une épaisseur de 3 à 20 mm et qui contient des quantités précises de C, Si, Mn, P, S, Al et N, le reste étant constitué de fer et d'impuretés inévitables. Les teneurs en N dissous à l'état solide, C et N sont dans des plages spécifiques, et de la ferrite bainitique ayant une taille de grains cristallins moyenne spécifique et de la perlite ont des occupations de surface spécifique dans la structure, avec le reste étant occupé par de la ferrite polygonale. Cette tôle d'acier laminée à chaud a une distribution de dureté spécifique dans le sens de l'épaisseur.
PCT/JP2015/061767 2014-04-18 2015-04-16 Tôle d'acier laminée à chaud ayant une excellente aptitude à l'écrouissage et une excellente dureté après travail WO2015159965A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
MX2016013517A MX2016013517A (es) 2014-04-18 2015-04-16 Lamina de acero laminada en caliente que tiene buena capacidad de trabajo y excelente dureza despues del trabajo.
DE112015001872.7T DE112015001872T5 (de) 2014-04-18 2015-04-16 Warmgewalztes Stahlblech mit gutem Kaltbearbeitungsvermögen und hervorragender Härte nach der Bearbeitung
KR1020167028769A KR101736019B1 (ko) 2014-04-18 2015-04-16 강냉간 가공성과 가공 후의 경도가 우수한 열연 강판
US15/303,658 US20170037496A1 (en) 2014-04-18 2015-04-16 Hot-rolled steel sheet having good cold workability and excellent hardness after working
CN201580019843.9A CN106232847B (zh) 2014-04-18 2015-04-16 强冷加工性和加工后的硬度优异的热轧钢板

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2014086747A JP6284813B2 (ja) 2014-04-18 2014-04-18 強冷間加工性と加工後の硬さに優れる熱延鋼板
JP2014-086747 2014-04-18

Publications (1)

Publication Number Publication Date
WO2015159965A1 true WO2015159965A1 (fr) 2015-10-22

Family

ID=54324166

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2015/061767 WO2015159965A1 (fr) 2014-04-18 2015-04-16 Tôle d'acier laminée à chaud ayant une excellente aptitude à l'écrouissage et une excellente dureté après travail

Country Status (7)

Country Link
US (1) US20170037496A1 (fr)
JP (1) JP6284813B2 (fr)
KR (1) KR101736019B1 (fr)
CN (1) CN106232847B (fr)
DE (1) DE112015001872T5 (fr)
MX (1) MX2016013517A (fr)
WO (1) WO2015159965A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107268012B (zh) * 2017-06-13 2019-07-19 浙江协和薄钢科技有限公司 酸洗卷制造工艺
CN107190267B (zh) * 2017-06-13 2019-06-14 浙江协和首信钢业有限公司 一种酸洗钢卷的制造工艺
KR20210127922A (ko) * 2019-02-18 2021-10-25 타타 스틸 이즈무이덴 베.뷔. 기계적 특성이 개선된 고강도 강
CN115029618B (zh) * 2021-03-03 2023-10-13 宝山钢铁股份有限公司 一种窄淬透性冷锻齿轮钢及其制造方法
CN114921718A (zh) * 2022-04-12 2022-08-19 首钢京唐钢铁联合有限责任公司 一种多模式薄板坯连铸连轧产线的集装箱用钢及其制备方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002047536A (ja) * 2000-02-23 2002-02-15 Kawasaki Steel Corp 歪時効硬化特性に優れた高張力熱延鋼板およびその製造方法
JP2003231946A (ja) * 2002-02-12 2003-08-19 Jfe Steel Kk 歪時効硬化特性に優れた溶融亜鉛めっき鋼板およびその製造方法
JP2005206943A (ja) * 2003-12-26 2005-08-04 Jfe Steel Kk 焼付硬化性と耐常温時効性に優れた高張力熱延鋼板およびその製造方法
JP2006233309A (ja) * 2005-02-28 2006-09-07 Jfe Steel Kk 焼付硬化性及び成形性に優れた高張力熱延鋼板およびその製造方法
JP2015048527A (ja) * 2013-09-04 2015-03-16 株式会社神戸製鋼所 冷間加工性と加工後の表面性状および硬さに優れる熱延鋼板

Family Cites Families (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52125410A (en) * 1976-04-15 1977-10-21 Nisshin Steel Co Ltd Production of polished steel strrips dispersed fine spherulitic carbides
US4501626A (en) * 1980-10-17 1985-02-26 Kabushiki Kaisha Kobe Seiko Sho High strength steel plate and method for manufacturing same
US5470529A (en) * 1994-03-08 1995-11-28 Sumitomo Metal Industries, Ltd. High tensile strength steel sheet having improved formability
JPH10306345A (ja) 1997-04-28 1998-11-17 Kobe Steel Ltd 歪時効特性に優れた冷間鍛造用線材・棒鋼およびその製造方法
CN1183268C (zh) * 2000-02-23 2005-01-05 杰富意钢铁株式会社 应变时效硬化特性优异的高强度热轧钢板及其制造方法
US6709224B2 (en) * 2002-06-12 2004-03-23 Rockland, Inc. Implement coupling assembly
JP4001116B2 (ja) 2004-02-06 2007-10-31 Ｊｆｅスチール株式会社 精密打ち抜き加工性および耐赤スケール疵性に優れる高張力熱延鋼板
WO2007000955A1 (fr) * 2005-06-29 2007-01-04 Jfe Steel Corporation Feuille d’acier à forte teneur en carbone laminée à chaud et son procédé de fabrication
JP5011846B2 (ja) * 2005-06-29 2012-08-29 Ｊｆｅスチール株式会社 高炭素熱延鋼板およびその製造方法
US20100000063A1 (en) * 2006-08-03 2010-01-07 Ansaldo Energia S.P.A. Method and device for repairing the liquid-cooled electrical windings of the stator of an electric generator
JP4462264B2 (ja) 2006-12-28 2010-05-12 Ｊｆｅスチール株式会社 窒化処理用冷延鋼板の製造方法
JP5297145B2 (ja) * 2008-02-29 2013-09-25 株式会社神戸製鋼所 冷間鍛造性に優れる機械構造用鋼材および冷間鍛造部品
US20090228125A1 (en) * 2008-03-04 2009-09-10 William Stewart Processing of heterogeneous media in a mobile computing device
EP2942416B1 (fr) * 2011-03-31 2017-06-07 Kabushiki Kaisha Kobe Seiko Sho Feuille d'acier à haute résistance avec une excellente aptitude au façonnage et son procédé de fabrication

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002047536A (ja) * 2000-02-23 2002-02-15 Kawasaki Steel Corp 歪時効硬化特性に優れた高張力熱延鋼板およびその製造方法
JP2003231946A (ja) * 2002-02-12 2003-08-19 Jfe Steel Kk 歪時効硬化特性に優れた溶融亜鉛めっき鋼板およびその製造方法
JP2005206943A (ja) * 2003-12-26 2005-08-04 Jfe Steel Kk 焼付硬化性と耐常温時効性に優れた高張力熱延鋼板およびその製造方法
JP2006233309A (ja) * 2005-02-28 2006-09-07 Jfe Steel Kk 焼付硬化性及び成形性に優れた高張力熱延鋼板およびその製造方法
JP2015048527A (ja) * 2013-09-04 2015-03-16 株式会社神戸製鋼所 冷間加工性と加工後の表面性状および硬さに優れる熱延鋼板

Also Published As

Publication number Publication date
MX2016013517A (es) 2017-02-14
JP6284813B2 (ja) 2018-02-28
KR101736019B1 (ko) 2017-05-15
US20170037496A1 (en) 2017-02-09
CN106232847A (zh) 2016-12-14
DE112015001872T5 (de) 2017-01-05
JP2015206071A (ja) 2015-11-19
CN106232847B (zh) 2018-04-27
KR20160124239A (ko) 2016-10-26

Similar Documents

Publication Publication Date Title
JP6058439B2 (ja) 冷間加工性と加工後の表面硬さに優れる熱延鋼板
JP6068314B2 (ja) 冷間加工性と浸炭熱処理後の表面硬さに優れる熱延鋼板
KR101621639B1 (ko) 강판, 도금 강판 및 그들의 제조 방법
KR101706485B1 (ko) 고강도 냉연 강판 및 그 제조 방법
US10060002B2 (en) H-section steel and method of producing the same
JP6177551B2 (ja) 絞り加工性と加工後の表面硬さに優れる熱延鋼板
WO2016148037A1 (fr) Tôle d'acier destinée à la cémentation possédant d'excellentes aptitudes au façonnage à froid et ténacité après traitement thermique de cémentation
KR101965520B1 (ko) 냉간 단조 부품용 압연 봉강 또는 압연 선재
WO2011115279A1 (fr) Tôle d'acier laminé à chaud ayant d'excellentes propriétés d'écrouissage et propriétés de durcissement et son procédé de production
JP5363922B2 (ja) 伸びと伸びフランジ性のバランスに優れた高強度冷延鋼板
KR101965521B1 (ko) 냉간 단조 부품용 압연 봉강 또는 압연 선재
WO2015060311A1 (fr) Tôle d'acier laminée à chaud ayant une excellente dureté de surface après traitement thermique de cémentation au carbone et une excellente emboutissabilité
WO2015159965A1 (fr) Tôle d'acier laminée à chaud ayant une excellente aptitude à l'écrouissage et une excellente dureté après travail
KR101892526B1 (ko) 고탄소 열연 강판 및 그 제조 방법
KR20190028782A (ko) 고주파 담금질용 강
JP4324226B1 (ja) 降伏応力と伸びと伸びフランジ性に優れた高強度冷延鋼板
KR102455453B1 (ko) 우수한 연성과 구멍 확장성을 갖는 고강도 강판
WO2011152328A1 (fr) Tôle d'acier haute résistance laminée à chaud, et son procédé de production
KR102064147B1 (ko) 고강도 박강판 및 그 제조 방법
JP6058508B2 (ja) 冷間加工性と加工後の表面性状および硬さに優れる熱延鋼板
JP2019011510A (ja) 冷間加工性と浸炭熱処理後の靱性に優れる浸炭用鋼板
JP5363867B2 (ja) 伸びおよび伸びフランジ性に優れた高強度冷延鋼板
WO2019203251A1 (fr) Tôle d'acier laminée à chaud
JP2017197816A (ja) 冷間加工性と冷間加工後の硬さに優れる熱延鋼板
JP2018062692A (ja) 熱延鋼板

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15780143

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: 15303658

Country of ref document: US

Ref document number: IDP00201606862

Country of ref document: ID

WWE Wipo information: entry into national phase

Ref document number: MX/A/2016/013517

Country of ref document: MX

ENP Entry into the national phase

Ref document number: 20167028769

Country of ref document: KR

Kind code of ref document: A

WWE Wipo information: entry into national phase

Ref document number: 112015001872

Country of ref document: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15780143

Country of ref document: EP

Kind code of ref document: A1