AU2005200300A1 - High strength steel sheet and method for manufacturing same - Google Patents
High strength steel sheet and method for manufacturing same Download PDFInfo
- Publication number
- AU2005200300A1 AU2005200300A1 AU2005200300A AU2005200300A AU2005200300A1 AU 2005200300 A1 AU2005200300 A1 AU 2005200300A1 AU 2005200300 A AU2005200300 A AU 2005200300A AU 2005200300 A AU2005200300 A AU 2005200300A AU 2005200300 A1 AU2005200300 A1 AU 2005200300A1
- Authority
- AU
- Australia
- Prior art keywords
- steel sheet
- high strength
- cooling
- strength steel
- less
- 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims description 105
- 239000010959 steel Substances 0.000 title claims description 105
- 238000000034 method Methods 0.000 title claims description 27
- 238000004519 manufacturing process Methods 0.000 title claims description 16
- 238000001816 cooling Methods 0.000 claims description 93
- 230000000052 comparative effect Effects 0.000 claims description 35
- 229910001568 polygonal ferrite Inorganic materials 0.000 claims description 35
- 238000005098 hot rolling Methods 0.000 claims description 23
- 229910000734 martensite Inorganic materials 0.000 claims description 19
- 239000012535 impurity Substances 0.000 claims description 7
- 229910052719 titanium Inorganic materials 0.000 claims description 7
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 229910052758 niobium Inorganic materials 0.000 claims description 6
- 229910052796 boron Inorganic materials 0.000 claims description 5
- 229910052750 molybdenum Inorganic materials 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 238000005266 casting Methods 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 229910052748 manganese Inorganic materials 0.000 claims description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 22
- 230000015572 biosynthetic process Effects 0.000 description 16
- 230000009977 dual effect Effects 0.000 description 16
- 239000011572 manganese Substances 0.000 description 13
- 230000000694 effects Effects 0.000 description 11
- 229910001562 pearlite Inorganic materials 0.000 description 11
- 229910001563 bainite Inorganic materials 0.000 description 9
- 230000007423 decrease Effects 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 230000009466 transformation Effects 0.000 description 9
- 229910001566 austenite Inorganic materials 0.000 description 8
- 230000002349 favourable effect Effects 0.000 description 8
- 238000005096 rolling process Methods 0.000 description 8
- 229910000885 Dual-phase steel Inorganic materials 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229910052698 phosphorus Inorganic materials 0.000 description 5
- 241000219307 Atriplex rosea Species 0.000 description 4
- 238000011161 development Methods 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910001341 Crude steel Inorganic materials 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 230000000593 degrading effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 101100379080 Emericella variicolor andB gene Proteins 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 239000011573 trace mineral Substances 0.000 description 1
- 235000013619 trace mineral Nutrition 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
- 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
- C21D2211/008—Martensite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Metal Rolling (AREA)
Description
AUSTRALIA
Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): JFE Steel Corporation Invention Title: HIGH STRENGTH STEEL SHEET AND METHOD FOR MANUFACTURING SAME The following statement is a full description of this invention, including the best method of performing it known to me/us: 1A- HIGH STRENGTH STEEL SHEET AND METHOD FOR MANUFACTURING SAME FIELD OF THE INVENTION The present invention relates to a high strength steel sheet most suitable for automobile body, reinforcements, wheels, and chassis parts and further for all kinds of machine structural parts, and to a method for manufacturing same.
DESCRIPTION OF THE RELATED ARTS For global environmental protection and further improvement of the safety of passengers, automobile steel sheets are studied to increase the strength and to decrease the thickness.
Since, however, increase in the strength of a material generally decreases the press-formability, the widening of application fields of high strength steel sheets faces an important issue of increase in the formability.
A known response to the requirement is dual phase steel sheet structured by ferrite and martensite as the main phases, (the steel has several names of Dual Phase steel, DP steel, and composite structural steel). Owing to low yield ratio, (hereinafter referred to simply as YR), and high elongation, the dual phase steel sheet is superior in the press-formability such as draw-forming property and surface precision after press-forming (shape accuracy), thus the dual phase steel sheet drew attention as an automobile material, and the development thereof has been enhanced.
Forexample, the dual phase micro-structure ina hot-rolled 2 steel sheet is achieved during the cooling step after hot-rolling by transformation to polygonal ferrite much enough to enrich a solute element in the residual austenite, thus increasing in the quench-hardenability due to the transformation to martensite.
The technology emphasizes the control of precipitated amount of polygonal ferrite to form the micro-structure and to improve the mechanical characteristics. Accordingly, various development studies on the control of polygonal ferrite precipitation have been given.
Patent Documents 1 through 11 disclose methods combining with what is called the two-stage cooling process as a steel composition design. The methods include the steps of: adding large amount of ferrite-stabilizing elements represented by Si, (and including P, Al, and the like); stopping cooling, in the cooling step after hot-rolling, at near A, temperature where the ferrite precipitation is accelerated; holding the temperature for about 10 seconds; and applying cooling again.
Patent Documents 12 through 15 disclose manufacturing methods to obtain desired steel sheet without adding the ferrite-stabilizing element. That is, the methods adopt a cooling-control pattern different from conventional method, for example, dividing the rapid cooling after finish-rolling into two stages.
Patent Documents 16 through 18 disclose methods to apply rapid coolingimmediately afterthe hot-rolling. Inparticular, Patent Document 16 adopts the above-method for a low Si steel.
3 Patent Document 1: JP-A-60-121225, (the term"JP-A" referred to herein signifies "Japanese Patent Laid-Open Publication".)
C)
0 g 5
(N
in oq Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document Patent Document 2: 3: 4: 5: 6: 7: 8: 9: 10: 11: 12: 13: 14: 15: 16: 17: 18: JP-A-3-10049 JP-A-4-235219 JP-A-4-289126 JP-A-4-337026 JP-A-4-341523 JP-A-7-150294 JP-A-9-67641 JP-A-9-125194 JP-A-9-137249 JP-A-10-195588 JP-A-54-065118 JP-A-56-136928 JP-A-3-126813 JP-A-4-276024 JP-A-2002-69534 JP-A-2001-192736 JP-A-2001-355023 Patent Documents 1 through 11, however, need to add excess Si, P, and Al, though they show favorable mechanical characteristics, thus theyhaveproblems of degradation insurface property caused by red-scale formation, degradation in coatability, and degradation in weldability. Consequently, their applications are limited.
The steel sheets manufactured by the methods according 4 to Patent Documents 12 through 15 contain small amount of Si, P, and A1 so that the cooling method in related art cannot fully progress the transformation from austenite to ferrite on the runout table after hot-rolling. As a result, the volume percentage of polygonal ferrite becomes small, the volume percentage of martensitebecomes large, and thepolygonal ferrite grains become coarse by the same reason, which fails to attain adequatemetallicmicro-structure. Thus, themanufacturedsteel sheet showshigherthan 0.6 ofYRinthemechanicalcharacteristics, which is an inferior characteristic. To increase the strain dispersion and to improve the shape accuracy, YR is required to be 0.6 or less.
As described above, the method for manufacturing hot-rolled dual phase steel sheet according to the related art adopts either the addition of ferrite-stabilizing element (Si, P, Al, or the like) sacrificing the surface property and other features or the sacrification of mechanical characteristics.
Patent Documents 16 and 17, however, do not consider YR and the metallic micro-structure to attain the YR.
Since Patent Document 18 is a technology to manufacture a high Si steel, the surface property of the steel sheet becomes poor. To improve the surface property, Si may be decreased. If, however, the Si content is decreased, no adequate metallic micro-structure is obtained, and the YR characteristic becomes poor. Both the YR and the surface property cannot be satisfied at a time.
5 SUMMARY OF THE INVENTION It would be advantageous if embodiments of the present invention provided a high strength steel sheet having excellent formability (YR s 0.6) and excellent surface property through the development of a method for adequately controlling the metallic micro-structure and improving the mechanical characteristics of the steel sheet without adding excess ferrite-stabilizing elements (Si, P, and Al) which degrade the surface property, weldability, and the like, and to provide a method for manufacturing same.
The inventors of the present invention found a phenomenon which significantly enhances the fine ferrite formation compared with conventional two-stage cooling process, even without adding excess ferrite-stabilization elements, by beginning the ultra-rapid cooling at 150OC/s or higher cooling rate within 2 seconds after the hot-rolling, followed by holding the temperatures between 750 0 C and 600 0 C for a specified period of time. The inventors of the present invention applied the finding to the manufacture of dual phase hot-rolled high strength steel sheet, and have perfected the present invention.
According toa first aspect, the present inventionprovides a high strength steel sheet which consists essentially of 0.05 to 0.15% C, 0.5% or less Si, 1.00 to 2.00% Mn, 0.09% or less P, 0.01% or less S, 0.005% or less N, 0.01 to 0.1% Sol.Al, by mass, and the balance being Fe and inevitable impurities; and 60% or more of polygonal ferrite by volume, and 5 to 30% of martensite 6 by volume.
The polygonal ferrite is preferably from 60 to 95% by volume.
The polygonal ferrite preferably has a mean grain size of 5 to P m.
The martensite is preferably from 10 to 20% by volume.
The high strength steel sheet preferably contains 0.01 to 0.5% Si by mass. The Si content is more preferably 0.25% or less by mass. Since Si has an effect to increase the strength, the Si content is preferably 0.01% or more. The P content is preferably from 0.020 to 0.06% by mass.
The high strength steel sheet may further contain at least one element selected from the group consisting of 0.01 to 0.3% Mo, 0.001 to 0.05% Nb, 0.001 to 0.1% Ti, 0.0003 to 0.002% B, and 0.05 to 0.49% Cr, by mass.
The high strength steel sheet preferably has a yield ratio of 0.6orlower. If the yield ratio exceeds 0.6, the shape accuracy deteriorates during press-forming.
According to a further aspect, the present invention also provides a method for manufacturing high strength steel sheet comprising the steps of: casting a slab consisting essentially of 0.05 to 0.15% C, 0.5% or less Si, 1.00 to 2.00% Mn, 0.09% or less P, 0.01% or less S, 0.005% or less N, 0.01 to 0.1% Sol.A1, by mass, and the balance being Fe and inevitable impurities; hot-rolling the cast slab, directly or heating thereof, at a temperature of Ar3 point or more to form a hot rolled steel sheet; a primary cooling step of cooling the hot-rolled steel sheet 7 beginning cooling thereof within 2 seconds after completing the hot-rolling to a temperature of from 750 0 C to 600 0 C at a cooling rate of 1500C/s or more; holding the cooled steel sheet at a temperaturebetween750 C and600 Cfor2 to15 seconds; asecondary cooling step of cooling the temperature-held steel sheet at a cooling rate of 200C/s or more; and coiling the steel sheet at a coiling temperature of 400 0 C or less.
The slab may further contain at least one element selected from the group consisting of 0.01 to 0.3% Mo, 0.001 to 0.05% Nb, 0.001 to 0.1% Ti, 0.0003 to 0.002% B, and 0.05 to 0.49% Cr, by mass.
The cooling rate in the primary cooling step is preferably in a range from 150 to 10000C/s, and more preferably from 200 to 700°C/s.
The cooling rate inthesecondarycoolingstep ispreferably in a range from 20 to 10000C/s.
The coiling temperature is preferably in a range from 0 C to 400 0
C.
The percentage for the ingredients of the steel, given in the description, is by mass.
The term "high strength steel sheet" referred to herein signifies a steel sheet havingmore than 590 MPa of tensile strength which TS values are suitable for the machine structural parts.
An embodiment of the present invention provides a high strength steel sheet having excellent formability and surface property. The steel sheet manufactured by the present invention 8 has low YR (0.6 or less) with high strength, high ductility, excellent press-formability, excellent surface property, and excellent spot weldability, thus the steel sheet can readily be applied to the automobile parts and machine structural parts.
Since the high strength steel sheet can be manufactured by the conventionalprocessformanufacturingmildsteelsheet, andsince the attained performance thereof is favorable without adding special elements, the manufacturing cost can be decreased.
Accordingly, the high strength steel sheet according to an embodiment of the present invention is highly expected in practical uses in the future, and is expected to contribute to the conservation of global environment by the weight reduction of automobile and to the social development through the improvement of safety of automobile.
BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a graph showing the relation between the yield ratio (YR) and the primary cooling rate.
EMBODIMENTS OF THE INVENTION The high strength steel sheet according to an embodiment of the present invention specifies the composition as below, specifies the volume percentage of polygonal ferrite to 60% or more, specifies the volume percentage of martensite to a range from 5 to 30%, and specifies the mean grain size of polygonal ferrite to a range from 5 to 10 p m. With the composition and micro-structure specified above, the high strength steel sheet 9 having excellent formability and surface property can be obtained.
The high strength steel sheet can be manufactured by the sequential steps of: hot-rolling the steel at Ar3 pint or higher temperature; beginning cooling of the steel sheet within 2 seconds after the completion of hot-rolling; cooling the steel sheet to temperatures between 750 C and 600 °C at cooling rates of 150 C/sormore; holding the temperature of steel sheet in a range from 750 0 C to 600°C for 2 to 15 seconds; cooling the steel sheet at cooling rates of 20°C/s or more; and coiling the steel sheet at 400 0 C or below.
In the manufacturing method, the beginning of cooling within 2 seconds after completing the hot-rolling, the ultra-rapid cooling at 150 0°C/s or higher cooling rate, and the holding in a temperature range from 750 0 C to 600 0 C are critical conditions of the present invention.
Embodiments of the present invention are described in more detail in the following.
The reason of specifying the chemical composition of the steel sheet according to embodiments of the present invention is described.
C: 0.05 to 0.15% Carbon is an important element to strengthen the martensitic phase. To attain satisfactory strength, the C content needs to be 0.05% or more. If, however, the C content exceeds 0.15%, austenite stabilizes, and the dual phase formation becomes difficult, which degrades the ductility. Accordingly, 10 the C content is specified to a range from 0.05% to 0.15%.
Regarding the spot weldability, the C content below 0.07% may degrade the tensile shear strength. If the C content exceeds 0.10%, the cross tension strength may decrease. Therefore, the C content is preferably in a range from 0.07 to 0.10%.
Si: 0.5% or less Silicon degrades the surface property by red scale and also degrades the coatability and weldability. If the Si content 0LO exceeds the bad influence of Si becomes significant.
Consequently, the Si content is specified to 0.5% or less. If the application of steel sheet emphasizes the surface property, the Si content is preferably 0.25% orless. Since Si has an effect to increase the strength, the Si content is preferably 0.01% or more.
Mn: 1.00 to 2.00% Manganese plays an important role for forming dual phase micro-structure by suppressing the pearlite formation during cooling after hot-rolling. If the Mn content is less than 1.00%, however, the effect is not sufficient, and pearlite is formed to increase YR, thus degrading the press-formability. If the Mn content exceeds 2.00%, austenite excessively stabilizes to prevent the formation of polygonal ferrite. Therefore, the Mn content is specified to a range from 1.00 to 2.00%. Furthermore, the Mn content below 1.30% may decrease the strength so that the Mn content is preferably 1.30% or more. When the Mn content 11 exceeds 1.80%, the elongation may degrade so that the Mn content is preferably 1.80% or less.
P: 0.09% or less When the P content exceeds 0.09%, the elongation is significantly degraded. Accordingly, the P content is specified to 0.09% or less. If the P content exceeds 0.06%, the toughness at welded section degrades to decrease the joint strength in some cases. Therefore, the P content is preferably 0.06% or less.
LO Furthermore, the P content of 0. 020% ormore enhances the formation of polygonal ferrite to decrease YR. Thus the P content is preferably 0.020% or more.
S: 0.01% or less Sulfur is an impurity in the crude steel and degrades the formability and weldability of steel sheet as the base material.
Accordingly, it is preferred to remove or reduce S in the steel making process as far as possible. Since, however, excess reduction of S increases the refining cost, the S content is specified to 0.01% or less, which level brings the S substantially harmless.
N: 0.005% or less Nitrogen is an impurity in the crude steel and degrades the formability of steel sheet as the base material. Accordingly, it is preferred to remove or reduce N in the steel making process as far as possible. Since, however, excess reduction of N 12 increases the refining cost, the N content is specified to 0.005% or less, which level brings the N substantially harmless.
Sol.Al: 0.01 to 0.1% Aluminum is added for deoxidization and for precipitating N as A1N. If the Al content is less than 0.01%, the effect of deoxidization and denitrification becomes insufficient. If the Al content exceeds the effect of Al addition saturates, which is uneconomical. Consequently, the Sol.A1 content is .0 specified to a range from 0.01 to 0.1%.
Steel according to an embodiment of the present invention attains the desired characteristics by the addition of above essential elements. Adding to the essential elements, however, the steel according to embodiments of the present invention may further include one or more element of Mo, Nb, Ti, B, and Cr at need for further increasing the strength. In that case, the respective contents of below 0.01%, 0.001%, 0.001%, 0.0003%, and 0.05% cannot give the satisfactory effect of addition. If the content ofMo, Nb, Ti, andB exceeds 0.05%, and 0.002%, respectively, the formation of dual phase micro-structure is hindered and the precipitation hardening becomes excessive so that the mechanical characteristics degrade (YR increases or elongation decreases). If the Cr content exceeds 0.49%, the performance of chemical conversion treatment degrades. When these element are added, therefore, the Mo content is specified to a range from 0.01 to Nb from 0.001 to 0.05%, Ti from 0.001 to B from 0.0003 to 0.002%, and Cr from 0.05 to 0.49%.
13 The balance of the above composition is Fe and inevitable impurities. Regarding the inevitable impurities, for example, o0 is preferably specified to 0.003% or less because O forms a non-metallic inclusion to degrade the quality. According to embodiments of the present invention, the steel may further include trace elements which do not harm the function and use of the present invention, namely Ni, V, Cu, Sb, Sn, Mg, and REM within a range of 0.1% or less.
.0 Secondly, the reason to specify the metallic micro-structure according to embodiments of the present invention are described below.
The volume percentage of polygonal ferrite is specified to 60% or more. The volume percentage of polygonal ferrite is a critical condition to achieve the low YR characteristic which is a feature of the present invention. To attain 0.6 or lower YR, the volume percentage of polygonal ferrite is required to become 60% ormore. The polygonal ferrite is found in the ferritic phase, and is distinguished from the acicular ferrite in the morphology, and is limited to the one having 5 or lower ratio of maximum diameter to minimum diameter of the ferritic crystal grain.
The volume percentage of martensite is specified to a range from 5 to 30%. Similar with the volume percentage of polygonal ferrite, the volume percentage of martensite is an important condition in embodiments of the present invention because the volumepercentage thereof influences the strength, theductility, 14 and the low YR characteristic. If the volume percentage of martensite is less than the strength becomes low, and no low YR characteristic is attained. If the volume percentage of martensite exceeds 30%, the ductility degrades. Therefore, the volume percentage of martensite is specified to a range from to 30%. To attain better low YR characteristic, the volume percentage of martensite is preferably in a range from 10 to The residual micro-structure contains acicular ferrite, bainite, pearlite, and the like. The volume percentage of residual LO micro-structure is, however, not specifically limited because the respective volume percentages of polygonal ferrite and martensite within the above-specified range assure the effect in embodiments of the present invention.
For further improving the balance between the strength and the ductility, or the product of strength and elongation, the mean grain size of polygonal ferrite is preferably specified to a range from 5 to 10 p m. Generally, the elongation in tensile test is expressed by the sum of uniform elongation and local elongation. If the grain size of polygonal ferrite is less than 5 p m, the uniform elongation may decrease in some cases. If the grain size of polygonal ferrite exceeds 10 p m, the local elongation degrades, though the value of local elongation is within allowable range. Presumable reason of the phenomenon is the following. For a dual phase steel, if thegrainsbecome coarse, the deformation becomes nonuniform so that stress intensifies into a certain section, which enhances the generation of micro-cracks.
15 The method for manufacturing high strength steel sheet having excellent formability and surface property according to an embodiment of the present invention is described in the following.
The high strength steel sheet according to the present invention is manufactured by the steps of: casting a slab prepared to have the chemical composition any one of the embodiments given above; applying hot-rolling to the slab, directly or heating thereof, at Ar3 point or higher temperature; beginning cooling .0 the slab within 2 seconds after completing the hot-rolling to temperatures ranging from 750 0 C to 600 0 C at cooling rates of 150CC/s or more; holding the cooled slab at temperatures between 750 0 C and 600 0 C for 2 to 15 seconds; applying cooling to the temperature-held slab at cooling rates of 20°C/s or more; and coiling the cooled slab at temperatures of 400 0 C or below.
The method for casting the slab is not specifically limited.
For the case of continuous casting, hot-rolling may be done directly or may be done after reheating after cooling.
The hot-rolling is conducted at Ar3 point or higher temperature. If the hot-rolling is done below the Ar3 point, the hot-rolling proceeds in the dual phase region of ferrite and austenite, which hinders the formation of polygonal ferrite, increases YR, and decreases the ductility.
After completing the hot-rolling, the cooling begins within 2 seconds to cool the steel to a temperature range from 750 0 C to600 0 C, which is the holding temperature range, at cooling rates of 150°C/s or more. The primary cooling which is given 16 immediately after the hot-rolling is the most important condition to attain the effect of the present invention, (the effect of low YR attained by the enhancement of polygonal ferrite formation) With thus specified primary cooling and conduction of immediate rapid cooling, the holding step at temperatures of from 750 0
C
to 600 0 C succeeding to the primary cooling allows the fine transformed polygonal ferrite to be drastically enhanced. If the period between the completion of hot-rolling and the beginning of cooling exceeds 2 seconds, ferrite is irregularly formed in LO the austenite grain boundaries to hinder the transformation to polygonal ferrite during the holding step after the cooling. If the cooling rate is less than 150°C/s, the irregularprecipitation of ferrite in the austenite grain boundaries during the cooling step cannot be prevented, which hinders the transformation to polygonal ferrite during the holding step after cooling. For further increasing the effect, the primary cooling rate is preferably 200CC/s or more. If the primary cooling rate exceeds 1000C/s, the metallicmicro-structurebecomes nonuniformwithin the sheet thickness range, and the mechanical characteristics maydegrade. Accordingly, theprimary cooling rate is preferably 1000°C/s or less, and more preferably 700CC/s or less.
After completing the primary cooling, the steel is held to a temperature range from 750 0 C to 600 0 C for 2 to 15 seconds.
If the temperature range for holding the steel is above 750 0
C,
the driving force of ferrite transformation becomes small, and no transformation enhancement effect is attained. If the temperature range therefor is below 600 0 C, the ferrite 17 transformation which is controlled by the diffusion of Fe atoms delays, and satisfactory polygonal ferrite formation cannot be attained. If the holding time is less than 2 seconds, the ferrite transformation time is not sufficient, which fails to attain the low YR characteristic. If the holding time exceeds 15 seconds, the pearlite formation begins to degrade the mechanical characteristics.
After holding the steel sheet, the secondary cooling is conducted at cooling rates of 20°C/s or more, and the coiling LO of the steel sheet is done at temperatures of 400 0 C or below.
The cooling rate in the secondary cooling is required to be or more to suppress the formation of pearlite and bainite during cooling. If the secondary cooling rate exceeds 1000CC/s, the metallic micro-structure becomes nonuniform within the sheet thickness range, and the mechanical characteristics may degrade.
Therefore, the secondary cooling rate is preferably 1000°C/s or less.
The coiling temperature is required to be 400CC or below to prevent the formation of pearlite and bainite after coiling, to form martensite, and to attain the target of 0.6 or lower YR.
Furthermore, to prevent the fluctuations of strength within the coil, the coiling temperature is preferably 300CC or below, and more preferably 200CC or below. If the coiling temperature becomes below 0CC, the cooling by water becomes difficult so that the coiling temperature is preferably 0°C or above.
To thus obtained high strength steel sheet according to an embodiment of the present invention, a skin pass rolling may 18 further be applied for shape-correction. In addition, various surface treatments such as hot-dip galvanization and electro-galvanization may be applied to embodiments of the high strength steel sheet according to the present invention as the base material.
Example 1 Slabs having respective chemical compositions given in Table 1 were prepared by continuous casting. They were cooled, .0 thenheatedtotemperaturesfrom ll00 C to 1300°C, andweretreated by final rolling at temperatures in a range from Ar3 point to 850 0 C to obtain steel sheets having thicknesses of from 1.6 to 3.2 mm. Within 1 second after completing the final rolling, cooling began on the steel sheets to conduct the primary cooling to a temperature range from 680 0 C to 720 0 C at cooling rates from 300 to 5000C/s. After that, the steel sheets were held at the temperature range for 7 to 12 seconds. Then, the steel sheets were cooled at cooling rates from 25 to 30°C/s, and were coiled at 350 0 C or lower temperature to obtain the respective hot-rolled steel sheets. As for Steel No. 4, however, the temperature to stop the primary cooling was 550 0 C, and Steel No. 5 was coiled at 450 0 C, thus adjusting the micro-structure thereof given in Table 1. The percentage of polygonal ferrite and the percentage of martensite were determined by observing the cross section vertical to the sheet width direction and by measuring the area percentage of each phase. Regarding the grain size of polygonal ferrite, the segmental method was applied to measure the 19 above-described cross sectional micro-structure to derive an average value of the value in the rolling direction and the value in the sheet thickness direction.
2005200300 25 Jan 2005 Table 1 Chemical composition (mass%) Volume Volume Main Grain size of Classification Steel percentage of percentage of micro-structure of polygonal ferrite No. C Si Mn P S SoI.AI N Other polygonal martensite residual portion (p m) ferrite Comparative 1 0.03 0.30 1.60 0.015 0.003 0.04 0.003 70 5 Bainite 10% 12 Example Example 2 0.06 0.01 1.50 0.010 0.002 0.05 0.004 80 10 Acicular ferrite 10% Example 3 0.06 0.01 1.50 0.010 0.002 0.05 0.004 0.0008B 70 15 Acicular ferrite 10% Comparative 4 0.06 0.01 1.50 0.010 0.002 0.05 0.004 40 10 Acicular ferrite 50% 11 Example Comparative 5 0.06 0.01 1.50 0.010 0.002 0.05 0.004 70 0 Bainite 15% 8 Example Example 6 0.08 0.20 1.50 0.010 0.005 0.05 0.004 90 10 6 Example 7 0.11 0.01 1.40 0.015 0.001 0.04 0.003 0.1Mo 85 15 8 Example 8 0.14 0.05 1.44 0.020 0.007 0.07 0.002 70 15 Pearlite 10% 6 Comparative 9 0.17 0.15 1.60 0.012 0.004 0.06 0.004 50 35 Pearlite 10% 4 Example Example 10 0.07 0.01 1.70 0.013 0.003 0.03 0.004 80 15 Bainite 5% 9 Example 11 0.06 0.24 1.65 0.008 0.001 0.01 0.003 70 10 Bainite 5% 8 Example 12 0.08 0.45 1.45 0.018 0.005 0.05 0.002 0.02Nb 85 15 7 Comparative 13 0.09 0.70 1.55 0.011 0.002 0.06 0.004 85 15 Example Comparative 14 0.07 0.30 0.80 0.009 0.003 0.04 0.004 80 0 Pearlite 10% 12 Example Example 15 0.11 0.05 1.75 0.012 0.002 0.07 0.003 80 20 9 Comparative 16 0.08 0.22 2.20 0.014 0.001 0.06 0.002 50 50 -7 Example Example 17 0.10 0.31 1.65 0.040 0.004 0.03 0.004 85 15 6 Comparative 18 0.12 0.10 1.54 0.100 0.005 0.05 0.004 90 10 Example Example 19 0.07 0.13 1.35 0.025 0.004 0.04 0.003 0.04Ti 79 21 Example 20 0.06 0.08 1.10 0.045 0.004 0.04 0.004 0.40Cr 84 16 9 21 For each of thus obtained hot-rolled steel sheets, the mechanical characteristics, the surface property, and the spot weldability were evaluated. The result is given in Table 2. The evaluation methods are the following. The mechanical characteristics were determined by the test per JIS Z2241 with a JIS No. 5 Tensile Test sample (prepared by cutting the steel sheet lateral to the rolling direction). The surface property was determined by visual observation in terms of presence/absence of red scale. Regarding the spot weldability, spot-welding was LO given under a condition to form a nugget having the size of x sheet thickness and then the peal test using a chisel was applied to break the sheet to observe the fracture mode.
Fracture on main portion of the sheet was evaluated to o, and fracture on welded section was evaluated to X.
22 Table 2 Mechanical characteristics Surface Spot Classification Steel No.
YP(MPa) TS(MPa) YR property weldability Comparative 1 390 520 36.5 0.75 a o Example Example 2 354 610 31.1 0.58 o o Example 3 352 640 29.7 0.55 o o Comparative 4 390 600 31.7 0.65 o o Example Comparative 5 428 570 33.3 0.75 o o Example Example 6 345 650 29.2 0.53 o o Example 7 373 690 27.5 0.54 o o Example 8 462 810 23.5 0.57 o o Comparative 9 683 1050 18.1 0.65 o x Example Example 10 369 670 28.4 0.55 o o Example 11 336 590 32.2 0.57 o o Example 12 352 640 29.7 0.55 a o Comparative 13 369 670 28.4 0.55 x o Example Comparative 14 451 530 35.8 0.85 o Example Example 15 383 710 26.8 0.54 o o Comparative 16 723 850 22.4 0.85 o o Example Example 17 385 700 27.1 0.55 A o Comparative 18 468 780 24.4 0.60 0 x Example Example 19 398 675 28.1 0.59 o o Example 20 389 695 27.3 0.56 o o Table 2 shows that all the steels according to the present invention, (Example steels), have excellent mechanical characteristics (YR s and give favorable surface property and weldability. Steel Nos. 12 and 17 gave somewhat degraded 23 surface property owing to slightly high Si content. However, Steel Nos. 12 and 17 were judged to be at a level of raising no significant problem in practical use.
In contrast, Steel No. 1 which is a comparative example had low C content, outside the range of embodiments of the present invention; sothat the hardness of martensite was unsatisfactory, which increased the YR value. Steel Nos. 4 and 5 had the volume percentage of polygonal ferrite or the volume percentage of martensite outside the range of embodiments of the present LO invention, so that they failed to form favorable dual phase micro-structure and they gave high YR value. Steel No. 9 had large C content outside the range of embodiments of the present invention so that the ferrite formation delayed to fail in attaining favorable dual phase micro-structure, and resulted in high YR value, as well as degrading the spot weldability. Steel No. 13 had large Si content outside the range of embodiments of the present invention so that red scale was generated to give poor surface property. Steel No. 14 had small Mncontent outside the range of embodiments of the present invention so that the austenite became instable and the pearlite was generated, thus giving high YR value. Steel No. 16 had large Mn content outside the range of embodiments of the present invention so that the amount of formed polygonal ferrite became small, and the YR value became high. Steel No. 18 had large P content outside the range of embodiments of the present invention so that the spot weldability significantly degraded.
24 Example 2 Some of the slabs having the respective chemical compositions given in Table 1 were treated by hot-rolling, cooling, and coiling under the respective manufacturing conditions given in Table 3, thus obtained the respective hot-rolled steel sheets.
2005200300 25 Jan 2005 Table 3 lSteel Heating Finish Cooling Primary Stop Holding Secondary oiling Classification Symbol No. temperature temperature beginning time cooling temperature time cooling rate temperature (C) No (oC) (oC) speed (oC/s) Example A 2 1200 850 0.5 460 738 4 45 382 Example B 2 1250 830 1 290 738 4 21 373 Example C 2 1230 840 2 530 644 11 38 324 Comparative D 2 1050 820 5 230 701 12 42 144 example Comparative E 2 1150 830 1 50 707 12 45 136 example Example F 2 1250 850 1 180 717 6 40 317 Example G 2 1200 840 1 220 686 7 24 259 Example H 2 1100 830 1 450 698 6 20 116 Comparative I 6 1120 820 1 340 800 8 50 217 example Example J 6 1150 810 1 280 730 10 22 184 Example K 6 1280 830 1 530 680 10 22 181 Example L 6 1200 830 1 270 850 13 30 347 Comparative M 6 1130 820 1 390 350 11 41 285 example Comparative N 6 1180 840 1 240 634 46 158 example Example O 6 Hot direct rolling 820 1 560 682 8 33 350 Example P 6 1230 830 1 590 725 10 30 342 Comparative Q 6 1210 840 1 580 646 25 21 219 example Comparative R 17 1200 850 1 500 719 12 10 293 example Example S 17 1180 830 1 330 656 6 25 272 Example T 17 1240 820 1 470 632 12 35 382 Example U 17 1200 830 1 500 634 10 33 <100 Example V 17 1150 830 1 460 663 3 39 353 Comparative W 17 1220 830 1 480 712 7 20 450 example 26 0
O
O
0 N 0 (N For each of thus obtained hot-rolled steel sheets, the mechanical characteristics, the surface property, and the spot weldability were evaluated. The result is given in Table 4. The evaluation methods were the same with those in Example 1.
Table 4 Volume Volume Grain size of Mechanical characteristics Classification Symbol percentage of percentage of polygonal ferrite TS El polygonal ferrite YP TS El YR ol f martensite (p m) (MPa) (MPa) YR ap A 7 1 8 3 Example A 75 10 8 341 620 30.6 0.55 Example B 75 10 9 342 610 31.1 0.56 Example C 80 10 10 354 610 31.1 0.58 Comparative D 50 10 13 447 630 30.2 0.71 example Comparative E 40 5 15 488 650 29.2 0.75 example Example F 80 10 9 365 640 29.7 0.57 Example G 75 10 7 330 600 31.7 0.55 Example H 80 10 6 369 670 28.4 0.55 Comparative I 30 15 10 490 680 27.9 0.72 example Example J 85 12 8 381 680 27.9 0.56 Example K 90 10 7 336 590 32.2 0.57 Example L 80 10 5 364 650 29.2 56 Comparative M 35 5 4 446 550 34.5 0.81 example Comparative N 45 10 4 441 630 30.2 0.70 example Example 0 85 13 9 389 670 28.4 0.58 Example P 80 10 8 358 640 29.7 0.56 Comparative Q 80 0 12 451 530 35.8 0.85 example Comparative R 80 3 11 498 560 33.9 0.89 example Example S 85 8 9 369 670 28.4 0.55 Example T 75 18 8 412 710 26.8 0.58 Example U 85 15 5 366 690 27.5 0.53 Example V 85 15 8 385 700 27.1 0.55 Comparative W 75 0 9 475 650 29.2 0.73 example 27 Table 4 shows that all the steels according to embodiments of the present invention, (Example steels), have excellent mechanical characteristics (YR s All the Example steels showed favorable surface property and spot weldability within the range of Example 2.
In contrast, Symbol D which is a comparative example had a long period between the completion of rolling and the beginning ofprimary cooling, outside the range of embodiments of the present invention, thus ferrite was formed irregularly before beginning the cooling, which resulted in unfavorable dual phase micro-structure and high YR value. Symbol E had low primary cooling rate outside the range of embodiments of the present invention so that ferrite was formedirregularly before beginning the cooling, which resulted in unfavorable dual phase micro-structure and high YR value. Symbol I had high temperature of stopping the primary cooling outside the range of embodiments of the present invention so that the formation of ferrite during the succeeding holding step became insufficient, which resulted in unfavorable dual phase micro-structure and high YR value.
Symbol M had low temperature of stopping the primary cooling outside the range of embodiments of the present invention so that the formationofferriteduringthesucceedingholdingstepbecame insufficient, which resulted in unfavorable dual phase micro-structure and high YR value. Symbol N had insufficient holding time after the primary cooling outside the range of embodiments of the present invention so that the formation of ferrite became insufficient, which resulted in unfavorable dual vs -28 V% phasemicro-structureandhighYRvalue. Symbol Q hadlongholding time after the primary cooling outside the range of embodiments of the present invention so that pearlite was formed during holding Sstep, which resulted in unfavorable dual phase micro-structure andhighYRvalue. Symbol Rhad low secondary cooling rate outside the range of embodiments of the present invention so that bainite (1 was formed during cooling step, which resulted in unfavorable dual phase micro-structure and high YR value. Symbol W had high coiling temperature outside the range of embodiments of the present invention so that bainite was formed after coiling, which resulted in unfavorable dual phase micro-structure and high YR value.
Figure 1 shows the relation between YR and the primary cooling rate for Steel No. 2. The figure shows that favorable characteristics giving low YR value is attained at 150°C/s or higher primary cooling rate, which is the range of an embodiment of the present invention. Symbol D failed to attain favorable result because the time before the primary cooling was 5 seconds, which is outside the range of an embodiment of the present invention.
Since the steel sheet according to an embodiment of the present invention has excellent press-formability and excellent surface property, the steel is also applicable to formed parts which emphasize the appearance.
29 It is to be understood that a reference herein to a prior art publication does not constitute an admission that the publication forms a part of the common general knowledge in the art in Australia, or any other country.
Claims (14)
- 2. The high strength steel sheet according to claim 1, wherein the polygonal ferrite is 60 to 95% by volume.
- 3. The high strength steel sheet according to claim 1, wherein the martensite is 10 to 20% by volume.
- 4. The high strength steel sheet according to claim 1, wherein the polygonal ferrite has a mean grain size of 5 to 10 p m. N The high strength steel sheet according to claim 1, further containing at least one element selected from the group consisting of 0.01 to 0.3% Mo, 0.001 to 0.05% Nb, 0.001 to 0.1% Ti, 0.0003 to 0.002% B, and 0.05 to 0.49% Cr, by mass.
- 6. The high strength steel sheet according to claim 1, wherein the Si content is 0.01 to 0.5% by mass. 31
- 7. The high strength steel sheet according to claim 1, wherein the Si content is 0.01 to 0.25% by mass.
- 8. The high strength steel sheet according to claim 1, wherein the P content is 0.020 to 0.06% by mass.
- 9. The high strength steel sheet according to claim 1, having a yield ratio of 0.6 or less.
- 10. A method for manufacturing high strength steel sheet comprising the steps of: casting a slab consisting essentially of 0.05 to 0.15% C, or less Si, 1.00 to 2.00% Mn, 0.09% or less P, 0.01% or less S, 0.005% or less N, 0.01 to 0.1% Sol.Al, by mass, and the balance being Fe and inevitable impurities; hot-rolling the cast slab, directly or heating thereof, at a temperature of Ar3 point or more to form a hot-rolled steel sheet; a primary cooling step of cooling the hot-rolled steel sheet at a cooling rate of 150°C/s or more to a temperature of from 750 0 C to 600° C, beginning cooling thereof within 2 seconds after completing the hot-rolling; holding the cooled steel sheet at a temperature between 750 °C and 600°C for 2 to 15 seconds; a secondary cooling step of cooling the temperature-held steel sheet at a cooling rate of 20°C/s or more; and coiling the cooled steel sheet at a coiling temperature of 32 400 0 C or less.
- 11. The method according to claim 10, wherein the slab further contains at least one element selected from the group consisting of 0.01 to 0.3% Mo, 0.001 to 0.05% Nb, 0.001 to 0.1% Ti, 0.0003 to 0.002% B, and 0.05 to 0.49% Cr, by mass.
- 12. The method according to claim 10, wherein the cooling rate in the primary cooling step is from 150 to 10000C/s.
- 13. The method according to claim 12, wherein the cooling rate in the primary cooling step is from 200 to 700°C/s.
- 14. The method according to claim 10, wherein the cooling rate in the secondary cooling step is from 20 to 10000C/s. The method according to claim 10, wherein the coiling temperature is from 0°C to 400 0 C.
- 16. A high strength steel substantially as herein described with reference to the examples and/or the accompanying drawing, excluding any comparative examples.
- 17. A method for manufacturing high strength steel sheet substantially as herein described with reference to the examples and/or the accompanying drawing, excluding any comparative examples. 33 Dated this 2 5 st day of January 2005 JFE Steel Corporation By Its Patent Attorneys GRIFFITH HACK
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004-020843 | 2004-01-29 | ||
| JP2004020843 | 2004-01-29 | ||
| JP2004-326545 | 2004-11-10 | ||
| JP2004326545A JP4470701B2 (en) | 2004-01-29 | 2004-11-10 | High-strength thin steel sheet with excellent workability and surface properties and method for producing the same |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| AU2005200300A1 true AU2005200300A1 (en) | 2005-08-18 |
| AU2005200300B2 AU2005200300B2 (en) | 2007-05-03 |
| AU2005200300C1 AU2005200300C1 (en) | 2008-03-06 |
Family
ID=34656285
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU2005200300A Ceased AU2005200300C1 (en) | 2004-01-29 | 2005-01-25 | High strength steel sheet and method for manufacturing same |
Country Status (8)
| Country | Link |
|---|---|
| US (2) | US20050173031A1 (en) |
| EP (1) | EP1559797B1 (en) |
| JP (1) | JP4470701B2 (en) |
| KR (1) | KR100673424B1 (en) |
| CN (1) | CN100439542C (en) |
| AU (1) | AU2005200300C1 (en) |
| CA (1) | CA2493523C (en) |
| TW (1) | TWI277658B (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7879160B2 (en) | 2004-11-24 | 2011-02-01 | Nucor Corporation | Cold rolled dual-phase steel sheet |
| US7959747B2 (en) | 2004-11-24 | 2011-06-14 | Nucor Corporation | Method of making cold rolled dual phase steel sheet |
| US8337643B2 (en) | 2004-11-24 | 2012-12-25 | Nucor Corporation | Hot rolled dual phase steel sheet |
| US8435363B2 (en) | 2007-10-10 | 2013-05-07 | Nucor Corporation | Complex metallographic structured high strength steel and manufacturing same |
| US9149868B2 (en) | 2005-10-20 | 2015-10-06 | Nucor Corporation | Thin cast strip product with microalloy additions, and method for making the same |
| US9999918B2 (en) | 2005-10-20 | 2018-06-19 | Nucor Corporation | Thin cast strip product with microalloy additions, and method for making the same |
| US10071416B2 (en) | 2005-10-20 | 2018-09-11 | Nucor Corporation | High strength thin cast strip product and method for making the same |
| US11155902B2 (en) | 2006-09-27 | 2021-10-26 | Nucor Corporation | High strength, hot dip coated, dual phase, steel sheet and method of manufacturing same |
| US11193188B2 (en) | 2009-02-20 | 2021-12-07 | Nucor Corporation | Nitriding of niobium steel and product made thereby |
Families Citing this family (42)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4476923B2 (en) * | 2005-12-15 | 2010-06-09 | 株式会社神戸製鋼所 | Steel sheet with excellent impact absorption and base metal toughness |
| CN100348767C (en) * | 2005-12-27 | 2007-11-14 | 东北大学 | Strength of extension 750-795 MPa grade double-phase steel plate and mfg. method thereof |
| CN1330785C (en) * | 2005-12-27 | 2007-08-08 | 东北大学 | Strength of extension 1000 MPa grade complex phase steel plate and mfg. method thereof |
| CA2636652A1 (en) * | 2006-01-26 | 2007-08-02 | Giovanni Arvedi | Hot rolled dual phase steel strip having features of a cold rolled strip |
| JP4518029B2 (en) * | 2006-02-13 | 2010-08-04 | 住友金属工業株式会社 | High-tensile hot-rolled steel sheet and manufacturing method thereof |
| CN100435987C (en) * | 2006-11-10 | 2008-11-26 | 广州珠江钢铁有限责任公司 | Method for manufacturing 700MPa high-strength weathering steel based on thin slab continuous casting and rolling flow by use of Ti microalloying process |
| CN101802238B (en) * | 2007-08-01 | 2012-05-23 | 株式会社神户制钢所 | High-strength steel sheet having excellent bending workability and fatigue strength |
| KR100957944B1 (en) | 2007-12-28 | 2010-05-13 | 주식회사 포스코 | High strength hot rolled steel sheet with excellent flange flange and weldability, hot leaded steel sheet and manufacturing method thereof |
| JP5365217B2 (en) * | 2008-01-31 | 2013-12-11 | Ｊｆｅスチール株式会社 | High strength steel plate and manufacturing method thereof |
| JP5194858B2 (en) * | 2008-02-08 | 2013-05-08 | Ｊｆｅスチール株式会社 | High strength hot rolled steel sheet and method for producing the same |
| KR101079529B1 (en) * | 2008-12-24 | 2011-11-03 | 주식회사 포스코 | High-strength and high ductility hot rolled steel sheet having excellent surface property and method for manufacturing the same |
| JP4998755B2 (en) | 2009-05-12 | 2012-08-15 | Ｊｆｅスチール株式会社 | High strength hot rolled steel sheet and method for producing the same |
| EP2460613A4 (en) * | 2009-07-31 | 2015-11-04 | Neturen Co Ltd | WELDED COMPONENT AND WELDING METHOD |
| JP5744575B2 (en) | 2010-03-29 | 2015-07-08 | 新日鐵住金ステンレス株式会社 | Double phase stainless steel sheet and strip, manufacturing method |
| JP5884148B2 (en) * | 2010-04-16 | 2016-03-15 | Ｊｆｅスチール株式会社 | Thick steel plate excellent in coating film peeling resistance and method for producing the same |
| RU2449843C1 (en) * | 2010-11-01 | 2012-05-10 | Открытое акционерное общество "Магнитогорский металлургический комбинат" | Method of hot rolling of high-strength low-alloy sheets |
| RU2457912C2 (en) * | 2010-11-01 | 2012-08-10 | Открытое акционерное общество "Магнитогорский металлургический комбинат" | Method of hot rolling of low-alloy sheets |
| JP5365673B2 (en) * | 2011-09-29 | 2013-12-11 | Ｊｆｅスチール株式会社 | Hot rolled steel sheet with excellent material uniformity and method for producing the same |
| JP5842515B2 (en) | 2011-09-29 | 2016-01-13 | Ｊｆｅスチール株式会社 | Hot-rolled steel sheet and manufacturing method thereof |
| JP5365758B2 (en) | 2011-10-06 | 2013-12-11 | 新日鐵住金株式会社 | Steel sheet and manufacturing method thereof |
| JP5953952B2 (en) * | 2011-11-30 | 2016-07-20 | Ｊｆｅスチール株式会社 | Steel material excellent in impact resistance and method for producing the same |
| US10253386B2 (en) * | 2012-03-07 | 2019-04-09 | Jfe Steel Corporation | Steel sheet for hot press-forming, method for manufacturing the same, and method for producing hot press-formed parts using the same |
| CN102732794B (en) * | 2012-05-31 | 2014-08-06 | 攀钢集团攀枝花钢铁研究院有限公司 | Hot-rolled pickled plate for Cr-containing automobile structure and production method thereof |
| CN102719755A (en) * | 2012-05-31 | 2012-10-10 | 攀钢集团攀枝花钢铁研究院有限公司 | High-strength high-processability hot-rolled pickled plate for automobile structures and production method thereof |
| CN102912235B (en) * | 2012-10-29 | 2014-11-12 | 武汉钢铁(集团)公司 | Hot-rolled dual-phase steel in 590MPa tensile strength grade and method for manufacturing hot-rolled dual-phase steel |
| EP2980247B1 (en) * | 2013-03-29 | 2023-10-18 | JFE Steel Corporation | Method for producing a steel structure for hydrogen gas |
| JP6311793B2 (en) * | 2014-09-17 | 2018-04-18 | 新日鐵住金株式会社 | Hot rolled steel sheet |
| WO2016132549A1 (en) | 2015-02-20 | 2016-08-25 | 新日鐵住金株式会社 | Hot-rolled steel sheet |
| MX2017008622A (en) | 2015-02-20 | 2017-11-15 | Nippon Steel & Sumitomo Metal Corp | Hot-rolled steel sheet. |
| MX2017010537A (en) * | 2015-02-20 | 2017-12-14 | Nippon Steel & Sumitomo Metal Corp | Hot-rolled steel sheet. |
| JP6399201B2 (en) | 2015-02-25 | 2018-10-03 | 新日鐵住金株式会社 | Hot rolled steel sheet |
| WO2016135898A1 (en) | 2015-02-25 | 2016-09-01 | 新日鐵住金株式会社 | Hot-rolled steel sheet or plate |
| US20180030557A1 (en) * | 2015-03-06 | 2018-02-01 | Jfe Steel Corporation | High-strength electric resistance welded steel pipe and method for producing the same |
| WO2017006144A1 (en) | 2015-07-09 | 2017-01-12 | Arcelormittal | Steel for press hardening and press hardened part manufactured from such steel |
| RU2605037C1 (en) * | 2015-11-20 | 2016-12-20 | Федеральное Государственное Унитарное Предприятие "Центральный научно-исследовательский институт черной металлургии им. И.П. Бардина" (ФГУП "ЦНИИчермет им. И.П. Бардина") | Method for production of high-strength hot-rolled steel |
| EP3495529B1 (en) | 2016-08-05 | 2021-03-03 | Nippon Steel Corporation | Steel sheet and plated steel sheet |
| TWI629369B (en) | 2016-08-05 | 2018-07-11 | 日商新日鐵住金股份有限公司 | Steel plate and plated steel plate |
| MX2019001600A (en) * | 2016-08-10 | 2019-06-20 | Jfe Steel Corp | Thin steel sheet, and production method therefor. |
| CN109576581A (en) * | 2018-11-30 | 2019-04-05 | 宝山钢铁股份有限公司 | A kind of great surface quality, low yield strength ratio hot-rolled high-strength steel plate and manufacturing method |
| KR102236852B1 (en) * | 2018-11-30 | 2021-04-06 | 주식회사 포스코 | Steel plate for structure having excellent low yield ratio property and low temperature toughness and manufacturing method thereof |
| KR20240077000A (en) * | 2022-11-24 | 2024-05-31 | 주식회사 포스코 | Steel material having extremely low manganeses contents and method of manufacturing the same |
| CN118639115B (en) * | 2024-08-16 | 2024-11-29 | 鞍钢股份有限公司 | A 375MPa grade cold stamping automobile bridge housing steel and its production method |
Family Cites Families (29)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5465118A (en) * | 1977-11-04 | 1979-05-25 | Nippon Kokan Kk <Nkk> | Manufacture of high strength hot rolled steel sheet |
| JPS55110733A (en) * | 1979-02-19 | 1980-08-26 | Nippon Kokan Kk <Nkk> | Manufacture of cold-rolled high tensile steel having excellent strength-ductility balance |
| US4296919A (en) * | 1980-08-13 | 1981-10-27 | Nippon Steel Corporation | Apparatus for continuously producing a high strength dual-phase steel strip or sheet |
| JPS57137426A (en) * | 1981-02-20 | 1982-08-25 | Kawasaki Steel Corp | Production of low yield ratio, high tensile hot rolled steel plate by mixed structure |
| JPH0774377B2 (en) * | 1989-10-07 | 1995-08-09 | 新日本製鐵株式会社 | Manufacturing method of hot-rolled high-strength steel sheet with excellent fatigue resistance |
| JPH0826407B2 (en) * | 1991-02-28 | 1996-03-13 | 日本鋼管株式会社 | Method for manufacturing high strength hot rolled steel sheet with excellent stretch flangeability |
| US5213634A (en) * | 1991-04-08 | 1993-05-25 | Deardo Anthony J | Multiphase microalloyed steel and method thereof |
| JP2840479B2 (en) * | 1991-05-10 | 1998-12-24 | 株式会社神戸製鋼所 | Manufacturing method of high strength hot rolled steel sheet with excellent fatigue strength and fatigue crack propagation resistance |
| JP3276258B2 (en) * | 1995-01-20 | 2002-04-22 | 株式会社神戸製鋼所 | High-strength hot-rolled steel sheet with good chemical conversion property and workability and method for producing the same |
| FR2735147B1 (en) * | 1995-06-08 | 1997-07-11 | Lorraine Laminage | HIGH-STRENGTH, HIGH-STRENGTH HOT-ROLLED STEEL SHEET CONTAINING TITANIUM, AND METHODS OF MAKING SAME. |
| JPH0949026A (en) * | 1995-08-07 | 1997-02-18 | Kobe Steel Ltd | Production of high strength hot rolled steel plate excellent in balance between strength and elongation and in stretch-flange formability |
| JP3538990B2 (en) * | 1995-08-31 | 2004-06-14 | Ｊｆｅスチール株式会社 | High-strength hot-rolled steel sheet excellent in impact resistance and method for producing the same |
| JPH09170048A (en) * | 1995-12-15 | 1997-06-30 | Kobe Steel Ltd | High strength hot rolled steel plate for working, excellent in fatigue characteristic and bore expandability |
| JP3253880B2 (en) * | 1996-12-27 | 2002-02-04 | 川崎製鉄株式会社 | Hot-rolled high-strength steel sheet excellent in formability and collision resistance, and method for producing the same |
| JPH11279693A (en) * | 1998-03-27 | 1999-10-12 | Nippon Steel Corp | Good workability high-strength hot-rolled steel sheet with excellent bake hardenability and method for producing the same |
| DE19911287C1 (en) * | 1999-03-13 | 2000-08-31 | Thyssenkrupp Stahl Ag | Process for producing a hot strip |
| DE19936151A1 (en) * | 1999-07-31 | 2001-02-08 | Thyssenkrupp Stahl Ag | High-strength steel strip or sheet and process for its manufacture |
| JP3873579B2 (en) * | 2000-06-09 | 2007-01-24 | Ｊｆｅスチール株式会社 | Manufacturing method of high formability hot-rolled steel sheet |
| DE60045303D1 (en) * | 1999-09-29 | 2011-01-13 | Jfe Steel Corp | STEEL PLATE AND METHOD FOR THE PRODUCTION THEREOF |
| JP3879381B2 (en) * | 1999-09-29 | 2007-02-14 | Ｊｆｅスチール株式会社 | Thin steel plate and method for producing thin steel plate |
| EP1227167B1 (en) * | 2000-01-24 | 2006-01-18 | JFE Steel Corporation | Hot dip zinc plated steel sheet and method for producing the same |
| JP4193315B2 (en) * | 2000-02-02 | 2008-12-10 | Ｊｆｅスチール株式会社 | High strength steel sheet and high strength galvanized steel sheet with excellent ductility and low yield ratio, and methods for producing them |
| JP4313507B2 (en) | 2000-08-23 | 2009-08-12 | 新日本製鐵株式会社 | High-strength steel sheet for automobile cabin structural parts and its manufacturing method |
| CA2387322C (en) * | 2001-06-06 | 2008-09-30 | Kawasaki Steel Corporation | High-ductility steel sheet excellent in press formability and strain age hardenability, and method for manufacturing the same |
| TWI317383B (en) * | 2001-06-15 | 2009-11-21 | Nippon Steel Corp | High-strength alloyed aluminum-system plated steel sheet and high-strength automotive part excellent in heat resistance and after-painting corrosion resistance |
| KR100437930B1 (en) * | 2001-10-18 | 2004-07-09 | 스미토모 긴조쿠 고교 가부시키가이샤 | Steel sheet having excellent workability and shape accuracy and a method for its manufacture |
| JP3912181B2 (en) * | 2002-03-28 | 2007-05-09 | Ｊｆｅスチール株式会社 | Composite structure type high-tensile hot-dip galvanized cold-rolled steel sheet excellent in deep drawability and stretch flangeability and manufacturing method thereof |
| JP3870840B2 (en) * | 2002-05-23 | 2007-01-24 | Ｊｆｅスチール株式会社 | Composite structure type high-tensile cold-rolled steel sheet excellent in deep drawability and stretch flangeability and method for producing the same |
| EP1398390B1 (en) * | 2002-09-11 | 2006-01-18 | ThyssenKrupp Steel AG | Steel with a very fine ferritic and martensitic microstructure having a high tensile strength |
-
2004
- 2004-11-10 JP JP2004326545A patent/JP4470701B2/en not_active Expired - Fee Related
-
2005
- 2005-01-20 US US11/040,994 patent/US20050173031A1/en not_active Abandoned
- 2005-01-20 EP EP05001139.4A patent/EP1559797B1/en not_active Ceased
- 2005-01-21 CA CA002493523A patent/CA2493523C/en not_active Expired - Fee Related
- 2005-01-25 AU AU2005200300A patent/AU2005200300C1/en not_active Ceased
- 2005-01-26 CN CNB2005100063139A patent/CN100439542C/en not_active Expired - Fee Related
- 2005-01-26 TW TW094102230A patent/TWI277658B/en not_active IP Right Cessation
- 2005-01-27 KR KR1020050007363A patent/KR100673424B1/en not_active Expired - Fee Related
-
2009
- 2009-04-17 US US12/386,518 patent/US20090223607A1/en not_active Abandoned
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7879160B2 (en) | 2004-11-24 | 2011-02-01 | Nucor Corporation | Cold rolled dual-phase steel sheet |
| US7959747B2 (en) | 2004-11-24 | 2011-06-14 | Nucor Corporation | Method of making cold rolled dual phase steel sheet |
| US8337643B2 (en) | 2004-11-24 | 2012-12-25 | Nucor Corporation | Hot rolled dual phase steel sheet |
| US8366844B2 (en) | 2004-11-24 | 2013-02-05 | Nucor Corporation | Method of making hot rolled dual phase steel sheet |
| US9149868B2 (en) | 2005-10-20 | 2015-10-06 | Nucor Corporation | Thin cast strip product with microalloy additions, and method for making the same |
| US9999918B2 (en) | 2005-10-20 | 2018-06-19 | Nucor Corporation | Thin cast strip product with microalloy additions, and method for making the same |
| US10071416B2 (en) | 2005-10-20 | 2018-09-11 | Nucor Corporation | High strength thin cast strip product and method for making the same |
| US11155902B2 (en) | 2006-09-27 | 2021-10-26 | Nucor Corporation | High strength, hot dip coated, dual phase, steel sheet and method of manufacturing same |
| US8435363B2 (en) | 2007-10-10 | 2013-05-07 | Nucor Corporation | Complex metallographic structured high strength steel and manufacturing same |
| US9157138B2 (en) | 2007-10-10 | 2015-10-13 | Nucor Corporation | Complex metallographic structured high strength steel and method of manufacturing |
| US11193188B2 (en) | 2009-02-20 | 2021-12-07 | Nucor Corporation | Nitriding of niobium steel and product made thereby |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1648277A (en) | 2005-08-03 |
| TWI277658B (en) | 2007-04-01 |
| CA2493523A1 (en) | 2005-07-29 |
| US20050173031A1 (en) | 2005-08-11 |
| CA2493523C (en) | 2009-01-27 |
| TW200530409A (en) | 2005-09-16 |
| JP2005240172A (en) | 2005-09-08 |
| JP4470701B2 (en) | 2010-06-02 |
| US20090223607A1 (en) | 2009-09-10 |
| EP1559797B1 (en) | 2013-06-05 |
| AU2005200300C1 (en) | 2008-03-06 |
| KR20050077757A (en) | 2005-08-03 |
| AU2005200300B2 (en) | 2007-05-03 |
| EP1559797A1 (en) | 2005-08-03 |
| KR100673424B1 (en) | 2007-01-24 |
| CN100439542C (en) | 2008-12-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| AU2005200300B2 (en) | High strength steel sheet and method for manufacturing same | |
| EP1918396B1 (en) | High-tension steel sheet and process for producing the same | |
| US6315946B1 (en) | Ultra low carbon bainitic weathering steel | |
| US20230220509A1 (en) | Cold rolled and annealed steel sheet, method of production thereof and use of such steel to produce vehicle parts | |
| CN103146992A (en) | High-strength hot-dip galvanized steel sheet with excellent processability and process for producing the same | |
| US12060629B2 (en) | Method of production of a cold rolled and heat treated steel sheet and use of such steel to produce vehicle parts | |
| WO2013088666A1 (en) | High-yield-ratio high-strength cold-rolled steel sheet and method for producing same | |
| CN112739834A (en) | Hot rolled steel sheet and method of making the same | |
| JP5394306B2 (en) | High-strength steel plate with excellent plating properties and manufacturing method thereof | |
| EP1493828A1 (en) | High tensile steel excellent in high temperature strength and method for production thereof | |
| JP3417878B2 (en) | High-strength hot-rolled steel sheet excellent in stretch flangeability and fatigue properties and its manufacturing method | |
| JPH10130776A (en) | High ductility type high tensile cold rolled steel sheet | |
| KR100903546B1 (en) | High tensile hot rolled steel sheet with excellent freezing properties and endurance fatigue characteristics after molding and its manufacturing method | |
| JP2005213566A (en) | High-strength thin steel sheet excellent in workability, surface properties and plate flatness and method for producing the same | |
| CN111465710A (en) | High yield ratio type high strength steel sheet and method for manufacturing same | |
| JPH0790482A (en) | Thin steel sheet excellent in impact resistance and method of manufacturing the same | |
| JPH10204576A (en) | High-strength hot-rolled steel sheet excellent in workability and low-temperature toughness and method for producing the same | |
| KR101406561B1 (en) | High strength hot rolled steel sheet having excellent impact toughness and method for manufacturing the same | |
| CN104350170B (en) | Elongation and the excellent low yield ratio, high strength cold-rolled steel sheet of stretch flangeability and its manufacture method | |
| JP7519202B2 (en) | High-tensile steel plate with excellent base material toughness and joint toughness and its manufacturing method | |
| JP4639464B2 (en) | High-tensile hot-rolled steel sheet with excellent workability and method for producing the same | |
| JP2002003996A (en) | High tensile strength steel sheet with excellent impact resistance and manufacturing method | |
| JP2001059131A (en) | 60kg-class direct quenched and tempered steel with excellent weldability and toughness after strain aging | |
| CN118974301A (en) | Hot rolled steel sheet and method for producing the same | |
| JP2001115232A (en) | 60kg-class direct quenched and tempered steel with excellent weldability and toughness after strain aging |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| DA2 | Applications for amendment section 104 |
Free format text: THE NATURE OF THE AMENDMENT IS AS SHOWN IN THE STATEMENT(S) FILED 04 OCT 2007. |
|
| DA3 | Amendments made section 104 |
Free format text: THE NATURE OF THE AMENDMENT IS AS SHOWN IN THE STATEMENT(S) FILED 04 OCT 2007 |
|
| FGA | Letters patent sealed or granted (standard patent) | ||
| MK14 | Patent ceased section 143(a) (annual fees not paid) or expired |