CN108350550B - High-strength cold-rolled steel sheet having excellent shear workability and method for producing same - Google Patents

High-strength cold-rolled steel sheet having excellent shear workability and method for producing same Download PDF

Info

Publication number
CN108350550B
CN108350550B CN201680067955.6A CN201680067955A CN108350550B CN 108350550 B CN108350550 B CN 108350550B CN 201680067955 A CN201680067955 A CN 201680067955A CN 108350550 B CN108350550 B CN 108350550B
Authority
CN
China
Prior art keywords
steel sheet
rolled steel
cold
strength
shear workability
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.)
Active
Application number
CN201680067955.6A
Other languages
Chinese (zh)
Other versions
CN108350550A (en
Inventor
金成一
徐石宗
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.)
Posco Holdings Inc
Original Assignee
Posco Co Ltd
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 Posco Co Ltd filed Critical Posco Co Ltd
Publication of CN108350550A publication Critical patent/CN108350550A/en
Application granted granted Critical
Publication of CN108350550B publication Critical patent/CN108350550B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • 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
    • B21B1/02—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 heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
    • B21B1/026—Rolling
    • 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
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C21D8/0236—Cold 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
    • C21D8/0263—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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0436—Cold 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0463—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment following hot rolling
    • 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
    • C22C38/06—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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • 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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • 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
    • 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • 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
    • 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
    • C21D2211/004—Dispersions; Precipitations
    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0405—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0426—Hot rolling

Abstract

One aspect of the present invention relates to a high strength cold rolled steel sheet excellent in shear workability, comprising in wt%: c: 0.05 to 0.10%, Si: 0.01-0.5%, Mn: 1.2-2.0%, Al: 0.01-0.1%, Cr: 0.005-0.3%, B: 0.0003 to 0.0010%, Mo: 0.005-0.2%, P: 0.001-0.05%, S: 0.001-0.01%, N: 0.001 to 0.01%, Nb: 0.005-0.08%, Ti: 0.005-0.13%, V: 0.005 to 0.2%, and the balance Fe and unavoidable impurities, and one or more of carbide, nitride and carbonitride satisfying the following relational expressions (1) and (2). Relation (1): 2.0 < Mn > +2.5 < Mo > +1.5 < Cr > +300 < B > is < 2.5, the relation (2): 0.2 ≦ ([ Nb ]/93+ [ Ti ]/48+ [ V ]/51)/([ C ]/12+ [ N ]/14) ≦ 0.5 (wherein each element symbol in the relational expressions (1) and (2) represents weight% of the alloy element).

Description

High-strength cold-rolled steel sheet having excellent shear workability and method for producing same
Technical Field
The present invention relates to a high-strength cold-rolled steel sheet having excellent shear workability and a method for manufacturing the same.
Background
In order to use a friction plate for an automatic transmission of an automobile, for example, it is necessary to suppress propagation of cracks due to frictional heat as well as to reduce generation of cracks due to shearing, and to have high strength and high hardness.
As disclosed in patent document 1, a conventional high-strength cold-rolled steel sheet for a friction plate or for securing hardness employs a technique of cold-rolling a medium-carbon steel or a steel containing a plurality of alloying elements by a recovery annealing method and then annealing. Further, a method of subjecting high-carbon steel to a spheroidizing heat treatment process is generally used, and a technique of a secondary cold rolling method using cold rolling-annealing-cold rolling is proposed in patent document 2.
However, the high-strength steel sheet using the recovery annealing method has a problem in that it is difficult to manufacture steel having high strength, and the technique of performing spheroidizing heat treatment using high-carbon steel and the secondary cold rolling technique have a problem in that high manufacturing costs are required.
In addition, although the strength of the steel sheet is effectively improved by the solid solution strengthening effect of the alloy components such as C, Si, Mn, Mo, and Cr mainly used for manufacturing the cold-rolled high-strength steel sheet, when the alloy components are added in an amount of a desired content or more, segregation of the alloy components and unevenness of the microstructure are caused. In particular, hardenability of steel is increased at the time of cooling, so that transformation of ferrite is greatly delayed, and low-temperature phases (martensite phase and austenite phase) are generated, grain boundaries become non-uniform, so that generation of cracks is increased at the time of shear processing, and cracks are easily propagated when frictional heat is generated during use, so that defects are generated.
Further, when the addition of an alloy component such as Ti, Nb, or V used for further improvement of strength is not appropriate, coarse carbides, nitrides, and precipitates are formed in grain boundaries, and the amount of cracks generated during shear processing increases, and cracks are likely to propagate during shear processing. Further, when frictional heat is generated in the sheared portion during use, there is a problem that propagation of cracks is more likely to occur.
(Prior art document)
(patent document 1) application No. KR1998-0059809
(patent document 2) application No. DE2005-10031462
Disclosure of Invention
Technical problem to be solved
The purpose of the present invention is to provide a high-strength cold-rolled steel sheet having excellent shear workability, which is capable of suppressing cracking due to shear work and cracking due to frictional heat, and a method for manufacturing the same.
The technical problem to be solved by the present invention is not limited to the above. The technical problems to be solved by the present invention can be understood through the entire contents of the present specification, and it is no difficult for those skilled in the art to understand additional technical problems of the present invention.
Technical scheme
One aspect of the present invention relates to a high strength cold rolled steel sheet excellent in shear workability, comprising in wt%: c: 0.05 to 0.10%, Si: 0.01-0.5%, Mn: 1.2-2.0%, Al: 0.01-0.1%, Cr: 0.005-0.3%, B: 0.0003 to 0.0010%, Mo: 0.005-0.2%, P: 0.001-0.05%, S: 0.001-0.01%, N: 0.001 to 0.01%, Nb: 0.005-0.08%, Ti: 0.005-0.13%, V: 0.005 to 0.2%, and the balance Fe and unavoidable impurities, and one or more of carbide, nitride and carbonitride satisfying the following relational expressions (1) and (2).
Another aspect of the present invention relates to a method of manufacturing a high strength cold rolled steel sheet having excellent shear workability, comprising the steps of: heating a steel slab to 1200-1350 ℃, wherein the steel slab comprises the following components in percentage by weight: c: 0.05 to 0.10%, Si: 0.01-0.5%, Mn: 1.2-2.0%, Al: 0.01-0.1%, Cr: 0.005-0.3%, B: 0.0003 to 0.0010%, Mo: 0.005-0.2%, P: 0.001-0.05%, S: 0.001-0.01%, N: 0.001 to 0.01%, Nb: 0.005-0.08%, Ti: 0.005-0.13%, V: 0.005 to 0.2%, and the balance Fe and unavoidable impurities, and satisfies the following relational expressions (1) and (2); hot rolling the heated steel slab at a temperature ranging from 850 to 1150 ℃; cooling to the temperature of 550-750 ℃ after hot rolling and rolling; and pickling after the rolling, and cold rolling at a cold rolling reduction rate of 60-70%.
Relation (1): 2.0 to [ Mn ] +2.5[ Mo ] +1.5[ Cr ] +300[ B ] to 2.5
Relation (2): 0.2 ≦ ([ Nb ]/93+ [ Ti ]/48+ [ V ]/51)/([ C ]/12+ [ N ]/14) ≦ 0.5
(wherein each symbol of the elements in the relational expressions (1) and (2) represents a weight% of the alloy element).
Moreover, the described embodiments do not set forth all of the features of the present invention. Various features of the present invention and advantages and effects thereof may be understood in more detail with reference to the following detailed description.
Advantageous effects
The present invention has the effect of providing a high-strength cold-rolled steel sheet excellent in shear workability, which can suppress cracking due to shear workability and cracking due to frictional heat while ensuring high strength and high hardness, and a method for manufacturing the same.
Drawings
Fig. 1 is a graph showing values of relational expression (1) and relational expression (2) of the embodiment.
Best mode for carrying out the invention
Preferred embodiments of the present invention will be described below. However, the embodiments of the present invention may be modified into other various forms, and the scope of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more fully explain the present invention to those having ordinary skill in the art.
The high-strength cold-rolled steel sheet of the present invention having excellent shear workability will be described in detail below. Note that the following alloy composition is in weight%.
The high-strength cold-rolled steel sheet having excellent shear workability according to the present invention comprises, in weight%: c: 0.05 to 0.10%, Si: 0.01-0.5%, Mn: 1.2-2.0%, Al: 0.01-0.1%, Cr: 0.005-0.3%, B: 0.0003 to 0.0010%, Mo: 0.005-0.2%, P: 0.001-0.05%, S: 0.001-0.01%, N: 0.001 to 0.01%, Nb: 0.005-0.08%, Ti: 0.005-0.13%, V: 0.005 to 0.2%, and the balance Fe and unavoidable impurities, and one or more of carbide, nitride and carbonitride satisfying the following relational expressions (1) and (2).
C：0.05～0.10％
C is the most economical and effective element for strengthening steel, and increases the precipitation strengthening effect or the fraction of bainite phase when the addition amount is increased, thereby increasing the tensile strength. When the content of C is less than 0.05%, the reaction with Ti, Nb, V, or the like to form precipitates is reduced, and the effect of precipitation strengthening is low. On the other hand, when the content of C exceeds 0.10 wt%, coarse carbides are likely to be generated in grain boundaries, and fine cracks are generated in coarse carbide interfaces during shear processing, thereby deteriorating shear workability. Therefore, the C is preferably contained in an amount of 0.05 to 0.10 wt%.
Si：0.01～0.5％
The Si deoxidizes the molten steel, has a solid solution strengthening effect, and delays the formation of coarse carbides, thereby contributing to the improvement of formability. However, if the content of Si is less than 0.01%, the effect of delaying the formation of carbide is small, and thus formability is difficult to improve, and if the content of Si exceeds 0.5%, red scale due to Si is formed on the surface of the steel sheet during hot rolling, and not only the quality of the surface of the steel sheet is very poor, but also ductility and weldability are reduced. Therefore, the Si is preferably contained in an amount of 0.01 to 0.5%.
Mn：1.2～2.0％
Like Si, Mn is an element effective for solid solution strengthening of steel, and increases hardenability of steel, so that a bainite phase is easily formed in a weld heat affected zone after welding. However, when the content of Mn is less than 1.2%, the above-mentioned effects of Mn addition cannot be sufficiently obtained. On the other hand, when the Mn content exceeds 2.0%, hardenability is greatly increased to delay phase transformation of ferrite, thereby also reducing the precipitation strengthening effect, and segregation portions at the thickness center portion are greatly developed when a slab is cast in a continuous casting process, and fine structures formed in the thickness direction are not uniform when cooling is performed after hot rolling, thereby greatly increasing the occurrence of cracks when shearing is performed. Therefore, the Mn is preferably contained in a content of 1.2 to 2.0%.
Mo：0.005～0.2％
The Mo has a solid solution strengthening effect on the steel and increases hardenability of the steel, thereby improving strength of the steel. However, when the content of Mo is less than 0.005%, the above-mentioned effect by the addition of Mo cannot be obtained, and when the content of Mo exceeds 0.2%, the phase transformation of ferrite is delayed due to an excessive increase in hardenability, and the precipitation strengthening effect is also reduced. Furthermore, it is also economically disadvantageous and detrimental to weldability. Therefore, the content of Mo is preferably limited to 0.005 to 0.2%.
Cr：0.005～0.3％
The Cr has a solid solution strengthening effect on the steel and increases hardenability of the steel, thereby improving strength of the steel. However, when the content of Cr is less than 0.005%, the above-mentioned effect by addition of Cr cannot be obtained, and when the content of Cr exceeds 0.3%, transformation of ferrite is excessively delayed to form a martensite phase, thereby deteriorating elongation and reducing the precipitation strengthening effect. Further, similarly to Mn, the segregation portion at the thickness center portion is greatly developed, and the microstructure in the thickness direction is not uniform, thereby deteriorating the shear workability. Therefore, the content of Cr is preferably limited to 0.005 to 0.3%.
B：0.0003～0.0010％
B is an element that increases hardenability even when added in a small amount in steel, and when 0.0003% or more of B is added, it is segregated into austenite grain boundaries at high temperature, thereby stabilizing the grain boundaries and improving impact resistance, but when the content of B is less than 0.0003%, the above effect cannot be sufficiently obtained. On the other hand, when B is added in excess of 0.0010%, recrystallization is delayed during hot rolling, resulting in increased elongated grains, and phase transformation of ferrite is delayed during cooling, resulting in the fine structure becoming uneven. Further, the precipitation strengthening effect is reduced, so that it is difficult to obtain a desired strength, and the unevenness of the microstructure of the initially hot-rolled sheet becomes a cause of local stress concentration at the time of cold rolling, which is disadvantageous to the present invention. Therefore, the content of B is preferably limited to 0.0003 to 0.0010%.
P：0.001～0.05％
Like Si, P has both the effects of solid solution strengthening and promotion of ferrite transformation. However, in order to produce the P content of less than 0.001%, high production cost is required, which is economically disadvantageous, and sufficient strength cannot be obtained, and when the P content exceeds 0.05%, brittleness due to grain boundary segregation is generated, fine cracks are easily generated at the time of shear processing, and ductility and impact resistance are greatly deteriorated. Therefore, the content of P is preferably limited to 0.001 to 0.05%.
S：0.001～0.01％
S is an impurity present in steel, and when the content of S exceeds 0.01%, it forms a nonmetallic inclusion by bonding with Mn or the like, thereby causing a problem that fine cracks are easily generated at the time of cutting of steel and stretch flangeability and impact resistance are greatly reduced, and further, in order to make the S content less than 0.001%, it takes a lot of time to perform steel making work and productivity is reduced. Therefore, the S content is preferably limited to 0.001 to 0.01%.
Al：0.01～0.1％
The Al is a component mainly added for deoxidation. When the content of Al is less than 0.01%, the effect of adding Al is insufficient. On the other hand, when the content of Al exceeds 0.1%, Al is combined with nitrogen to form AlN, so that corner cracks are easily generated on a slab when continuous casting is performed, and defects due to the formation of inclusions are easily generated at an Edge (Edge) portion of a hot-rolled sheet. Further, there is a possibility that surface quality may be deteriorated due to surface defects generated when cold rolling is performed after hot rolling. Therefore, the content of Al is preferably limited to 0.01 to 0.1%.
N：0.001～0.01％
Together with C, the N is a representative solid solution strengthening element, and forms coarse precipitates together with Ti, Al, and the like. In general, N has a better solid solution strengthening effect than carbon, but has a problem of greatly decreasing toughness as the N content in steel increases. In addition, in order to produce the N content of less than 0.001%, a large amount of time is required for steel making operation, and productivity is lowered. Therefore, in the present invention, the content of N is preferably limited to 0.001 to 0.01%.
Ti：0.005～0.13％
The Ti is a representative precipitation strengthening element together with Nb and V, and forms coarse TiN in steel by strong affinity with N. TiN has an effect of inhibiting grain growth during heating for hot rolling. Further, Ti remaining after the reaction with nitrogen is dissolved in the steel and combined with carbon to form TiC precipitates, and therefore Ti is an effective component for improving the strength of the steel. Therefore, when the content of Ti is less than 0.05%, the above effect cannot be obtained, and when the content of Ti exceeds 0.13%, coarse TiN is generated, which causes a problem that shear workability is deteriorated when shear processing is performed. Therefore, in the present invention, the content of Ti is preferably limited to 0.005 to 0.13%.
Nb：0.005～0.08％
The Nb is a typical precipitation strengthening element together with Ti and V, and is effective in improving the strength and impact toughness of steel due to the effect of grain refinement by delayed recrystallization caused by precipitation of Nb in hot rolling. However, when the content of Nb is less than 0.005%, the above effect cannot be sufficiently obtained, and when the content of Nb exceeds 0.08%, elongation grains and coarse composite precipitates are formed due to excessively delayed recrystallization during hot rolling, which has a problem of deteriorating shear workability. Therefore, in the present invention, the content of Nb is preferably limited to 0.005 to 0.08%.
V：0.005～0.2％
The V is a typical precipitation strengthening element together with Nb and Ti, and Ti forms precipitates after being wound, thereby effectively improving the strength of the steel. Therefore, when the content of V is less than 0.005%, the above-mentioned effect cannot be sufficiently obtained, and when the content of V exceeds 0.2%, coarse composite precipitates are formed to deteriorate the shear workability, which is also economically disadvantageous. Therefore, in the present invention, the content of V is preferably limited to 0.005 to 0.2%.
The balance of the present invention is iron (Fe). However, in a general production process, unexpected impurities are inevitably mixed from the raw material or the surrounding environment, and therefore, they cannot be excluded. These impurities are well known to those skilled in the art of typical manufacturing processes and, therefore, not all of them are specifically mentioned in this specification.
In the present invention, when the alloy composition satisfies the following relational expressions (1) and (2), the hot rolling forms a uniform steel microstructure, and the cold rolling and the shearing can suppress the occurrence of cracks.
Relation (1): 2.0 to [ Mn ] +2.5[ Mo ] +1.5[ Cr ] +300[ B ] to 2.5
Relation (2): 0.2 ≦ ([ Nb ]/93+ [ Ti ]/48+ [ V ]/51)/([ C ]/12+ [ N ]/14) ≦ 0.5
(wherein each symbol of the elements in the relational expressions (1) and (2) represents a weight% of the alloy element).
The relational expression (1) relates to hardenability and segregation of steel, and takes into account the solid-solution strengthening effect of steel and the unevenness of the microstructure.
When the relational expression (1) is less than 2.0, the solid solution strengthening effect of the steel is insufficient, and there is a problem that a sufficiently high strength cannot be obtained. On the other hand, if the relation (1) exceeds 2.5, the microstructure in the thickness direction of the steel is not uniformly formed, and the phase transformation of ferrite is delayed, thereby having a problem of reducing the precipitation strengthening effect of the steel.
Therefore, it is preferable to control the relational expression (1) to 2.0 to 2.5.
Since the relational expression (2) limits the components involved in the formation of precipitates in steel and the formation of precipitates is related to the contents of Ti, Nb, V and C, N in the above composition, the relational expression (2) is to set the addition amounts of the Ti, Nb and V alloy elements to contents corresponding to C, N.
When the relation (2) is less than 0.2, the precipitation strengthening effect is remarkably reduced, so that desired strength and hardness values cannot be obtained, and when the relation (2) exceeds 0.5, the yield strength is greatly increased due to the formation of a large amount of fine precipitates, thereby causing deterioration of cold rolling property, and the precipitates formed in the thickness direction of the sheet are not uniform, thereby having a problem that the generation of cracks becomes serious when the shearing work is performed after the cold rolling.
Therefore, it is preferable to control the relational expression (2) to 0.2 to 0.5.
By controlling the alloy composition to satisfy the above, a high-strength cold-rolled steel sheet excellent in shear workability can be obtained, which not only ensures high strength and high hardness, but also suppresses cracks due to shear working and cracks due to frictional heat.
The cold-rolled steel sheet of the present invention is obtained by cold-rolling a hot-rolled sheet having a microstructure of ferrite and fine pearlite, and therefore has a microstructure (fully Hard microstructure) which is severely deformed in the rolling direction. In this case, although each phase in the microstructure of the cold-rolled steel sheet cannot be specified, the hot-rolled steel sheet before cold rolling has an area fraction of ferrite phase of 90% or more and a fine pearlite phase of less than 5%, and in addition, a bainite phase may be inevitably included.
The high-strength cold-rolled steel sheet having excellent shear workability according to the present invention contains at least one of carbide, nitride and carbonitride. For example, TiN, TiC, NbC, NbN, (Ti, Nb) (C, N), (Ti, Mo, Nb) (C, N) and (Fe, Mn)3C. More than one of (Fe, Mn, Mo) C.
In this case, the average size of the carbide, nitride and carbonitride is preferably 10 to 50 nm.
When the average size of carbides, nitrides and carbonitrides is less than 10nm, the yield strength of the hot-rolled sheet is excessively increased, so that local work hardening variation is likely to occur at the time of cold rolling, and cracks are likely to occur at the time of shear working and heat treatment of the cold-rolled sheet.
However, when the average size of the carbides, nitrides and carbonitrides exceeds 50nm, there is a problem that it is difficult to obtain desired tensile strength and hardness values.
In addition, the cold-rolled steel sheet may have a tensile strength of 1200MPa or more and a hardness value (Micro-Vickers) of 340Hv or more. By satisfying the tensile strength and hardness value, it can be preferably applied to a friction plate application of an automobile automatic transmission or the like.
Further, the length of the largest crack among cracks generated in the cold-rolled steel sheet in the shearing process is preferably 1mm or less.
The length of the maximum crack is a result of measuring the length of the maximum crack generated on the cross section after punching with a circular die having a diameter of 10mm under a condition of a 6% Clearance (Clearance) and then heat-treating at 200 c for one hour.
This is because when the length of the maximum crack exceeds 1mm, there are the following problems: the amount of generation of cracks is increased, and cracks are easily propagated when shear processing is performed, and cracks are more easily propagated when the temperature is increased by frictional heat.
Next, a method for manufacturing a high-strength cold-rolled steel sheet having excellent shear workability according to another aspect of the present invention will be described in detail.
A method of manufacturing a high strength cold rolled steel sheet excellent in shear workability according to another aspect of the present invention includes the steps of: heating a steel billet which meets the composition of the alloy at 1200-1350 ℃; hot rolling the heated steel slab at a temperature ranging from 850 to 1150 ℃; cooling to the temperature of 550-750 ℃ after hot rolling and rolling; and pickling after the rolling, and cold rolling at a cold rolling reduction rate of 60-70%.
Heating step
Heating the steel billet to 1200-1350 ℃.
When the heating temperature is less than 1200 ℃, precipitates are not sufficiently re-dissolved, so that the formation of precipitates is reduced in the step after hot rolling, and coarse TiN remains. On the other hand, when the heating temperature exceeds 1350 ℃, Abnormal Grain Growth of austenite grains (Abnormal Grain Growth) leads to a decrease in strength, and therefore, it is preferable to limit the reheating temperature to 1200 to 1350 ℃.
In this case, the billet may be produced in a process directly connected to the continuous casting process and the hot rolling process.
In order to re-dissolve the precipitates of TiN, TiC, NbC, NbN, (Ti, Nb) (C, N), (Ti, Mo, Nb) (C, N), it is important to set the temperature of the billet to 1200 to 1350 ℃.
Step of Hot Rolling
Hot rolling the heated slab at a temperature in the range of 850 to 1150 ℃.
When hot rolling is started at a temperature higher than 1150 ℃, the temperature of the hot rolled steel sheet becomes high, so that the grain size may become coarse and the surface quality of the hot rolled steel sheet may be deteriorated. Further, when the hot rolling is terminated at a temperature lower than 850 ℃, excessive delay of recrystallization causes development of elongated grains and a high yield ratio is obtained, so that cold rolling property is deteriorated and shear workability is also deteriorated.
Cooling and winding step
And cooling to the temperature of 550-750 ℃ after hot rolling and rolling.
When cooled to 550 ℃ or less and wound, a bainite phase and a martensite phase are formed in the steel, and the material quality of the steel is deteriorated, and when cooled to 750 ℃ or more and wound, coarse ferrite grains are formed, and coarse carbides and nitrides are easily formed, and the material quality of the steel is deteriorated.
In this case, the cooling can be performed at an average cooling rate of 10 to 70 ℃/sec.
When the average cooling rate is less than 10 ℃/sec at the time of cooling, coarse ferrite grains are formed, and the microstructure becomes uneven, and when the average cooling rate exceeds 70 ℃/sec, a bainite phase is easily formed, and the microstructure in the thickness direction of the plate also becomes uneven, and the shear workability of the steel becomes poor.
Step of Cold Rolling
And pickling after the rolling, and cold rolling at a cold rolling reduction rate of 60-70%.
When the cold rolling reduction is less than 60%, a sufficient work hardening effect cannot be obtained, so that it is difficult to secure strength and hardness of the steel. On the other hand, when the cold rolling reduction exceeds 70%, the quality of the Edge (Edge) portion of the steel may be deteriorated, and the shear workability may be deteriorated.
The cold-rolled steel sheet manufactured by the manufacturing method can not only ensure high strength and high hardness, but also suppress cracks caused by shear processing and cracks caused by frictional heat.
The cold-rolled steel sheet produced by the above production method may include one or more of carbide, nitride and carbonitride, and the average size of the carbide, nitride and carbonitride may be 10 to 50 nm. The tensile strength may be 1200MPa or more, the hardness may be 340Hv or more, and the length of the largest crack among cracks generated during shear processing may be 1mm or less.
Detailed Description
The present invention will be described more specifically with reference to examples. However, it should be noted that the following examples are merely illustrative for describing the present invention in more detail, and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the contents described in the claims and reasonably derived therefrom.
A steel slab having a composition shown in the following table 1 was heated at 1250 ℃, and a cold-rolled steel sheet was manufactured using the manufacturing conditions shown in the following table 2. In this case, the cooling rate after hot rolling is set to 20 to 30 ℃/sec.
Table 2 below shows the values of the relational expressions (1) and (2) calculated for the comparative examples and the invention examples, and FDT and CT respectively indicate the finish rolling temperature and the take-up temperature at the time of hot rolling.
In addition, the mechanical properties and the results of observing the fine structure of the inventive examples and the comparative examples are shown in table 3 below. In the following table 3, TS, Hv and maximum crack length are respectively a tensile strength and a Micro-Vickers (Micro-Vickers) hardness value of a cold rolled sheet, and the maximum crack length is a result of measuring the length of a maximum crack generated on a cross section after punching the cold rolled sheet with a circular die having a diameter of 10mm under a condition of 6% Clearance (Clearance) and then heat-treating the pressed sheet at 200 ℃ for one hour. The length of the crack was measured from the observation result of an optical microscope at 100 magnifications.
The hot-rolled sheet before cold rolling was analyzed for the size of carbides, nitrides and carbonitrides formed in the steel. The size and fraction of carbides, nitrides and carbonitrides having an average size of 10 to 50nm formed in steel were not changed by cold rolling, and a microstructure which was severely deformed after cold rolling had a problem in that it was difficult to accurately observe the size and fraction, and therefore, a hot-rolled sheet was analyzed. The average size of carbides, nitrides and carbonitrides was determined from the results measured by a transmission electron microscope. The carbide and nitride having an average size of 100nm or more were measured at a magnification of 50,000, and the precipitate having an average size of 100nm or less was measured at a magnification of 100,000. A tensile test was carried out using test pieces obtained in accordance with JIS5 standard with reference to the 0 ° direction with respect to the rolling direction of the rolled sheet.
[ Table 1]
Figure GDA0001667333540000121
Figure GDA0001667333540000131
[ Table 2]
Figure GDA0001667333540000132
Figure GDA0001667333540000141
[ Table 3]
Figure GDA0001667333540000142
Figure GDA0001667333540000151
Comparative example 1 and comparative example 2 do not satisfy the relational expressions (1) and (2), and the content of C in comparative example 1 does not satisfy the scope of the present invention. Both comparative examples did not obtain sufficient solid solution strengthening effect, and exceeded the upper limit of the relational expression (2) due to the relatively low C content and the relatively excessive Ti, Nb, and V. Therefore, the size of carbides, nitrides, and precipitates formed in the steel is fine, but the strength of the steel is not sufficiently ensured. In addition, as a result of applying the cold rolling reduction to comparative example 2 in a range exceeding the control of the present invention, a slightly severe crack was generated on the sheared surface after press working, and it was confirmed that the quality of the sheared surface was deteriorated.
In comparative examples 3 and 5, the relational expression (1) is not satisfied, and in comparative example 3, the occurrence of segregation in the central portion of the steel is increased and the quality of the shear-worked portion is deteriorated by exceeding the invention range of the relational expression (1). In comparative example 5, the contents of Mn, Cr, and B were small, and segregation was less generated, so that the quality of the shear worked surface was very good, but the desired strength and hardness value were not obtained because a sufficient solid solution strengthening effect was not obtained.
In comparative example 4 and comparative example 6, the relational expression (2) was not satisfied, and in comparative example 4, C remained, coarse precipitates and carbides were formed, and the precipitation strengthening effect was insufficient, and the desired strength and hardness values could not be obtained.
In comparative example 6, although a large amount of fine precipitates were formed beyond the scope of the invention of the relational expression (2), and a high strength was obtained, severe cracks were generated in the sheared portion.
Comparative examples 7, 8, 9 and 10 are steels produced with the target of tensile strength of 1350MPa or more and hardness of 355Hv or more after cold rolling, and comparative example 7 does not satisfy the relational expression (1), but the desired physical properties are secured by high cold rolling reduction. However, due to the high cold rolling reduction, a slightly severe crack was generated in the shear worked portion.
Comparative example 8 and comparative example 9 both satisfied the relational expressions (1) and (2), but the cold rolling reduction was not suitable, and the desired physical properties could not be obtained, or the quality of the shear-worked portion was poor. In comparative example 10, both the relational expressions (1) and (2) were not satisfied, and the quality of the shear-worked portion was poor.
On the other hand, the invention examples satisfy the component ranges and the production conditions proposed in the present invention, and the relational expressions (1) and (2), and thus, it can be confirmed that the desired material can be secured and the quality of the shear-worked portion is excellent.
Fig. 1 shows the relationship between the relational expressions (1) and (2) of the invention example and the comparative example, and the length of the maximum crack in the shear worked portion. The hatched area in fig. 1 corresponds to the scope of the present invention.
While the embodiments of the present invention have been described in detail, it will be apparent to those skilled in the art that various modifications and changes can be made without departing from the technical spirit of the present invention described in the claims.

Claims (10)

1. A high-strength cold-rolled steel sheet excellent in shear workability, comprising, in wt.%: c: 0.05 to 0.10%, Si: 0.01-0.5%, Mn: 1.2-2.0%, Al: 0.01-0.1%, Cr: 0.005-0.3%, B: 0.0003 to 0.0010%, Mo: 0.005-0.2%, P: 0.001-0.05%, S: 0.001-0.01%, N: 0.001 to 0.01%, Nb: 0.005-0.08%, Ti: 0.005-0.13%, V: 0.005 to 0.2%, and the balance Fe and inevitable impurities,
and satisfies the following relational expression (1) and relational expression (2),
and contains one or more of carbide, nitride and carbonitride,
relation (1): 2.0 to [ Mn ] +2.5[ Mo ] +1.5[ Cr ] +300[ B ] to 2.5
Relation (2): 0.2 ≦ ([ Nb ]/93+ [ Ti ]/48+ [ V ]/51)/([ C ]/12+ [ N ]/14) ≦ 0.5
Wherein each symbol of the elements in the relational expressions (1) and (2) represents a weight% of the alloy element.
2. The high-strength cold-rolled steel sheet excellent in shear workability according to claim 1, wherein the average size of said carbides, nitrides and carbonitrides is 10 to 50 nm.
3. A high-strength cold-rolled steel sheet excellent in shear workability according to claim 1, characterized in that said cold-rolled steel sheet has a tensile strength of 1200MPa or more and a hardness value of 340Hv or more.
4. A high-strength cold-rolled steel sheet having excellent shear workability according to claim 1, wherein the length of the largest crack among cracks generated during shear working is 1mm or less.
5. A high-strength cold-rolled steel sheet having excellent shear workability according to claim 1, wherein the area fraction of the ferrite phase in the microstructure of the hot-rolled steel sheet is 90% or more and the area fraction of the fine pearlite phase is less than 5% before cold rolling, and further, the bainite phase is inevitably contained.
6. A method of manufacturing a high strength cold rolled steel sheet having excellent shear workability, comprising the steps of:
heating a steel slab to 1200-1350 ℃, wherein the steel slab comprises the following components in percentage by weight: c: 0.05 to 0.10%, Si: 0.01-0.5%, Mn: 1.2-2.0%, Al: 0.01-0.1%, Cr: 0.005-0.3%, B: 0.0003 to 0.0010%, Mo: 0.005-0.2%, P: 0.001-0.05%, S: 0.001-0.01%, N: 0.001 to 0.01%, Nb: 0.005-0.08%, Ti: 0.005-0.13%, V: 0.005 to 0.2%, and the balance Fe and unavoidable impurities, and satisfies the following relational expressions (1) and (2);
hot rolling the heated steel slab at a temperature ranging from 850 to 1150 ℃;
cooling to the temperature of 550-750 ℃ after hot rolling and rolling; and
pickling is carried out after the rolling, and cold rolling is carried out at a cold rolling reduction rate of 60-70%;
relation (1): 2.0 to [ Mn ] +2.5[ Mo ] +1.5[ Cr ] +300[ B ] to 2.5
Relation (2): 0.2 ≦ ([ Nb ]/93+ [ Ti ]/48+ [ V ]/51)/([ C ]/12+ [ N ]/14) ≦ 0.5
Wherein each symbol of the elements in the relational expressions (1) and (2) represents a weight% of the alloy element.
7. The method of manufacturing a high strength cold rolled steel sheet excellent in shear workability according to claim 6, wherein said billet is produced by a continuous casting process.
8. The method for manufacturing a high-strength cold-rolled steel sheet having excellent shear workability according to claim 6, wherein said cooling is performed at an average cooling rate of 10 to 70 ℃/sec.
9. The method of manufacturing a high-strength cold-rolled steel sheet excellent in shear workability according to claim 6, wherein said cold-rolled steel sheet comprises one or more of carbides, nitrides and carbonitrides, and the average size of the carbides, nitrides and carbonitrides is 10 to 50 nm.
10. The method of manufacturing a high-strength cold-rolled steel sheet excellent in shear workability according to claim 6, wherein said cold-rolled steel sheet has a tensile strength of 1200MPa or more and a hardness value of 340Hv or more.
CN201680067955.6A 2015-11-20 2016-11-18 High-strength cold-rolled steel sheet having excellent shear workability and method for producing same Active CN108350550B (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
KR10-2015-0163368 2015-11-20
KR1020150163368A KR101778385B1 (en) 2015-11-20 2015-11-20 High strength cold rolled steel sheet having excellent shear workability and method for manufacturing the same
PCT/KR2016/013362 WO2017086745A1 (en) 2015-11-20 2016-11-18 High-strength cold rolled steel sheet having excellent shear processability, and manufacturing method therefor

Publications (2)

Publication Number Publication Date
CN108350550A CN108350550A (en) 2018-07-31
CN108350550B true CN108350550B (en) 2020-03-20

Family

ID=58719293

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201680067955.6A Active CN108350550B (en) 2015-11-20 2016-11-18 High-strength cold-rolled steel sheet having excellent shear workability and method for producing same

Country Status (5)

Country Link
US (1) US20190136339A1 (en)
JP (1) JP6684905B2 (en)
KR (1) KR101778385B1 (en)
CN (1) CN108350550B (en)
WO (1) WO2017086745A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102221452B1 (en) * 2019-05-03 2021-03-02 주식회사 포스코 Ultra-high strength steel sheet having shear workability excellent and method for manufacturing thereof
KR102328392B1 (en) 2019-12-20 2021-11-19 주식회사 포스코 Ultra high strength steel sheet having excellent punching section quality and method for manufacturing thereof

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10130782A (en) * 1996-11-01 1998-05-19 Nippon Steel Corp Ultrahigh strength cold rolled steel sheet and its production
JP4858286B2 (en) 2007-04-20 2012-01-18 住友金属工業株式会社 Full hard cold rolled steel sheet
JP5347739B2 (en) 2009-06-11 2013-11-20 新日鐵住金株式会社 Method for producing precipitation-strengthened double-phase cold-rolled steel sheet
KR101228753B1 (en) * 2010-12-07 2013-01-31 주식회사 포스코 Ultra high strength cold rolled steel sheet having excellent shape property and method for manufacturing the same
JP5182386B2 (en) * 2011-01-31 2013-04-17 Ｊｆｅスチール株式会社 High-strength cold-rolled steel sheet having a high yield ratio with excellent workability and method for producing the same
JP5725909B2 (en) 2011-02-28 2015-05-27 日新製鋼株式会社 Steel plate for clutch plate having excellent wear resistance and method for producing the same
DE102012002079B4 (en) * 2012-01-30 2015-05-13 Salzgitter Flachstahl Gmbh Process for producing a cold or hot rolled steel strip from a high strength multiphase steel
TWI468530B (en) * 2012-02-13 2015-01-11 新日鐵住金股份有限公司 Cold rolled steel plate, plated steel plate, and method of manufacturing the same
JP5633594B2 (en) * 2013-04-02 2014-12-03 Ｊｆｅスチール株式会社 Cold-rolled steel sheet excellent in punchability and heat-strain resistance and method for producing the same
JP2015034334A (en) * 2013-07-12 2015-02-19 株式会社神戸製鋼所 High-strength plated steel sheet excellent in platability, processability and delayed fracture resistance characteristics and production method thereof
KR101543918B1 (en) * 2013-12-25 2015-08-11 주식회사 포스코 Ultra high strength cold rolled steel sheet having excellent shape property and method for manufacturing the same
JP6119627B2 (en) * 2014-02-05 2017-04-26 Ｊｆｅスチール株式会社 High-strength cold-rolled thin steel sheet with high proportional limit and method for producing the same

Also Published As

Publication number Publication date
JP2018538441A (en) 2018-12-27
JP6684905B2 (en) 2020-04-22
CN108350550A (en) 2018-07-31
KR20170059528A (en) 2017-05-31
KR101778385B1 (en) 2017-09-14
US20190136339A1 (en) 2019-05-09
WO2017086745A1 (en) 2017-05-26

Similar Documents

Publication Publication Date Title
CN110832098B (en) Hot-rolled steel sheet and method for producing same
JP5277648B2 (en) High strength steel sheet with excellent delayed fracture resistance and method for producing the same
EP3653736B1 (en) Hot-rolled steel strip and manufacturing method
KR20160072099A (en) A high-hardness hot-rolled steel product, and a method of manufacturing the same
JP2005126733A (en) Steel sheet for hot press having excellent hot workability, and automotive member
CN110088337B (en) High-strength composite structure steel having excellent punching workability at low temperature and method for producing same
JP2007016296A (en) Steel sheet for press forming with excellent ductility after forming, its forming method and automotive parts using the steel sheet for press forming
EP2792762B1 (en) High-yield-ratio high-strength cold-rolled steel sheet and method for producing same
JP4085826B2 (en) Duplex high-strength steel sheet excellent in elongation and stretch flangeability and method for producing the same
CN114686777A (en) Flat steel product with good aging resistance and method for the production thereof
JP7244723B2 (en) High-strength steel material with excellent durability and its manufacturing method
CN108315637B (en) High carbon hot-rolled steel sheet and method for producing same
CN111356781B (en) High-strength hot-rolled steel sheet having excellent bendability and low-temperature toughness, and method for producing same
US11466336B2 (en) High-strength steel sheet having excellent burring workability in low temperature range and manufacturing method therefor
WO2015146174A1 (en) High-carbon hot-rolled steel sheet and method for producing same
CN111373060A (en) High-strength hot-rolled flat steel product having a high resistance to edge cracking and at the same time a high bake-hardening potential, and method for producing such a flat steel product
JP2010229514A (en) Cold rolled steel sheet and method for producing the same
CN113692456B (en) Ultrahigh-strength steel sheet having excellent shear workability and method for producing same
JP2010126808A (en) Cold rolled steel sheet and method for producing the same
JP3760888B2 (en) High-tensile cold-rolled steel sheet with excellent workability, manufacturing method and processing method thereof
CN108350550B (en) High-strength cold-rolled steel sheet having excellent shear workability and method for producing same
US20170204492A1 (en) Cold-rolled steel sheet having excellent spot weldability, and manufacturing method therefor
US20220403489A1 (en) Thick composite-phase steel having excellent durability and manufacturing method therefor
JP2002363685A (en) Low yield ratio high strength cold rolled steel sheet
KR102307927B1 (en) High strength dp steel sheet of which the durability and flexibility are outstanding and a production metfod therefor

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant
CP03 Change of name, title or address

Address after: Seoul, South Kerean

Patentee after: POSCO Holdings Co.,Ltd.

Address before: Gyeongbuk, South Korea

Patentee before: POSCO

CP03 Change of name, title or address
TR01 Transfer of patent right

Effective date of registration: 20230607

Address after: Gyeongbuk, South Korea

Patentee after: POSCO Co.,Ltd.

Address before: Seoul, South Kerean

Patentee before: POSCO Holdings Co.,Ltd.

TR01 Transfer of patent right