CN104018079A - Cold-rolled steel sheet, preparation method thereof, galvanized steel sheet and preparation method thereof - Google Patents
Cold-rolled steel sheet, preparation method thereof, galvanized steel sheet and preparation method thereof Download PDFInfo
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- CN104018079A CN104018079A CN201410274282.4A CN201410274282A CN104018079A CN 104018079 A CN104018079 A CN 104018079A CN 201410274282 A CN201410274282 A CN 201410274282A CN 104018079 A CN104018079 A CN 104018079A
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Abstract
The invention discloses a preparation method of a cold-rolled steel sheet. The method comprises the steps of sequentially carrying out hot rolling, reeling, cold rolling and annealing on a sheet blank, wherein the sheet blank is composed of 0.001-0.005wt% of C, 0.01-0.05wt% of Si, 0.2-0.7wt% of Mn, 0.03-0.08wt% of P, less than or equal to 0.02wt% of S, 0.01-0.08wt% of Al, 0.001-0.02wt% of Ti, 0.003-0.03wt% of Nb and the balance of Fe and unavoidable impurities. The invention also discloses a cold-rolled steel sheet prepared by using the method, a galvanized steel sheet and a preparation method thereof. According to the invention, the galvanized steel sheet with favorable strength (ReL is 250-300MPa, and Rm is at least 360MPa), forming property and surface quality can be obtained.
Description
Technical field
The present invention relates to a kind of cold-rolled steel sheet and preparation method thereof, and the hot-dip galvanizing sheet steel being made by this cold-rolled steel sheet and preparation method thereof.
Background technology
Along with the development of automobile industry, more and more higher for intensity and the formability performance requriements of the required hot dip cold-rolled steel sheet of vehicle body.
CN101036968A discloses a kind of production method of deep drawing skin-passed hot-dip galvanizing sheet steel.The method used by the carbon content control of substrate in the scope of 0.003-0.006 % by weight, Ti* content is controlled in the scope of 0.02-0.04 % by weight.But the yield strength of the deep drawing skin-passed hot-dip galvanizing sheet steel of the method gained is only below 190MPa, intensity is lower.
CN102839322A discloses a kind of automobile hot-dip galvanizing sheet steel and production method thereof.The chemical component weight per-cent of this steel plate is: 0.001%≤C≤0.003%, 0.05%≤Mn≤0.15%, Si≤0.03%, P≤0.02%, 0.008%≤S≤0.015%, 0.02%≤Al≤0.07%, 0.05%≤Ti≤0.09%, 0.0002%≤B≤0.01%, N≤0.004%, surplus is Fe and trace element.But the yield strength of this steel plate is only below 170MPa, tensile strength is also only below 300MPa.
Summary of the invention
The object of the invention is to overcome existing hot-dip galvanizing sheet steel can not have concurrently higher-strength and compared with high formability can defect, provide a kind of intensity and forming property all better and the hot-dip galvanizing sheet steel of excellent surface quality and preparation method thereof, and for the preparation of cold-rolled steel sheet of steel plate galvanized of the present invention and preparation method thereof.
To achieve these goals, the invention provides a kind of preparation method of cold-rolled steel sheet, the method comprises: by slab successively through hot rolling, batch, cold rolling and annealing, wherein,
After described hot rolling and before described batching, the intermediate slab obtaining is cooled to the temperature of batching with the speed of cooling of 20-30 DEG C/s after hot rolling;
Described temperature of batching is 730-780 DEG C;
Described cold rolling draft is 60-75%;
The condition of described annealing comprises: soaking temperature is 840-890 DEG C, and soaking time is 40-70s;
Consisting of of described slab: C:0.001-0.005 % by weight, Si:0.01-0.05 % by weight, Mn:0.2-0.7 % by weight, P:0.03-0.08 % by weight, S :≤0.02 % by weight, Al:0.01-0.08 % by weight, Ti:0.001-0.02 % by weight, Nb:0.003-0.03 % by weight, surplus is Fe and inevitable impurity.
The present invention also provides the cold-rolled steel sheet being made by aforesaid method.
The present invention also provides a kind of preparation method of hot-dip galvanizing sheet steel, and wherein, the method comprises adheres to upper zinc coating by above-mentioned cold-rolled steel sheet through galvanizing.
The present invention also provides the hot-dip galvanizing sheet steel being made by the preparation method of above-mentioned hot-dip galvanizing sheet steel.
By technique scheme, the present invention can obtain one at low cost to be had finished product mechanical property and reaches yield strength R
eLfor 250-300MPa, tensile strength R
m>=360MPa, elongation after fracture A
80>=36%, plastic strain ratio r
90>=1.5, work hardening exponent n
90>=0.2, baking hardening value BH
2ferritic structure, the ferrite grain size that>=60MPa, surface quality feature FC level are above, microstructure is 100% is that 8 grades of above and ferrite grain sizes are the hot-dip galvanizing sheet steel of 12-20 μ m, it is a kind of good baking hardening steel plate galvanized, be particularly suitable for, as the steel plate of complicated and exposed component of manufacturing automobile and motorcycle, thering are good market outlook.
Other features and advantages of the present invention are described in detail the embodiment part subsequently.
Brief description of the drawings
Accompanying drawing is to be used to provide a further understanding of the present invention, and forms a part for specification sheets, is used from explanation the present invention, but is not construed as limiting the invention with embodiment one below.In the accompanying drawings:
Fig. 1 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of embodiment 1.
Fig. 2 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of embodiment 2.
Fig. 3 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of embodiment 3.
Fig. 4 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of embodiment 4.
Fig. 5 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of comparative example 1.
Fig. 6 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of comparative example 2.
Fig. 7 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of comparative example 3.
Fig. 8 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of comparative example 4.
Fig. 9 is the microstructure picture of the hot-dip galvanizing sheet steel that makes of comparative example 5.
Embodiment
Below the specific embodiment of the present invention is elaborated.Should be understood that, embodiment described herein only, for description and interpretation the present invention, is not limited to the present invention.
The invention provides a kind of preparation method of cold-rolled steel sheet, the method comprises: by slab successively through hot rolling, batch, cold rolling and annealing, wherein, after described hot rolling and before described batching, the intermediate slab obtaining is cooled to the temperature of batching after hot rolling with the speed of cooling of 20-30 DEG C/s; Described temperature of batching is 730-780 DEG C; Described cold rolling draft is 60-75%; The condition of described annealing comprises: soaking temperature is 840-890 DEG C, and soaking time is 40-70s; Consisting of of described slab: C:0.001-0.005 % by weight, Si:0.01-0.05 % by weight, Mn:0.2-0.7 % by weight, P:0.03-0.08 % by weight, S :≤0.02 % by weight, Al:0.01-0.08 % by weight, Ti:0.001-0.02 % by weight, Nb:0.003-0.03 % by weight, surplus is Fe and inevitable impurity.
In the present invention, although just can obtain the cold-rolled steel sheet of better intensity and better forming property and made the hot-dip galvanizing sheet steel of good surface quality by this cold-rolled steel sheet in the time that the composition of slab is in above-mentioned scope, but in order to strengthen the performance of obtained cold-rolled steel sheet and hot-dip galvanizing sheet steel, under preferable case, consisting of of described slab: C:0.002-0.005 % by weight, Si:0.01-0.04 % by weight, Mn:0.3-0.65 % by weight, P:0.035-0.07 % by weight, S:0.007-0.015 % by weight, Al:0.03-0.07 % by weight, Ti:0.008-0.018 % by weight, Nb:0.007-0.02 % by weight, surplus is Fe and inevitable impurity.
In the present invention, consider the over-all properties of purity of steel and product, the carbon content in described slab need to be controlled in above-mentioned scope, if carbon (C) content exceedes 0.005 % by weight, and the Plasticity Decreasing of steel plate, forming property worsens; For example, moreover the content of silicon (Si) need to be controlled at lower scope, 0.01-0.05 % by weight; Manganese (Mn) can increase the intensity of described slab, and can be combined into MnS with sulphur (S), prevents the thermal crack causing because of FeS simultaneously, but Mn too high levels, the welding property that can affect steel, therefore, need to be controlled at the content of Mn in above-mentioned scope.In addition, phosphorus (P), as strengthening element, need to be added in above-mentioned scope.Consider the economy of steel making working procedure and the effect of calcium processing, S is controlled at below 0.02 % by weight.Aluminium (Al) mainly adds as deoxidant element, realize complete deoxidation, its content requirement is more than 0.01 % by weight, but too high aluminium will affect welding property and the coating adhesion and uneconomical of steel, therefore, Al content is chosen as 0.01-0.08 % by weight and is advisable.The main fixed interval (FI) of niobium (Nb) C atom, titanium (Ti) is mainly fixed interval (FI) N atom, and interstitial atom is removed, and obtains pure ferrite matrix.In the present invention, the Nb in described slab and the content of Ti are relatively low, and this makes the hot-dip galvanizing sheet steel being formed by this slab have a certain amount of interstitial atom, in bake process, and interstitial atom pinning crystal boundary, thus can improve the finished product intensity.
Described slab can adopt the known method of preparing continuously cast bloom of this area to be prepared, for example can be by obtaining continuously cast bloom after blast furnace ironmaking, hot metal pretreatment, converter smelting, steel ladle deoxidation, alloying furnace rear refining, LF electrically heated, RH vacuum-treat and sheet billet continuous casting as described slab of the present invention.The condition of its concrete preparation is well known in the art.
In addition, in the present invention, the thickness of described slab can be 190-210mm left and right.
According to the present invention, described hot rolling comprises roughing and finish rolling.The start rolling temperature of described roughing can be 1185-1230 DEG C, is preferably 1189-1220 DEG C; The finishing temperature of described roughing can be 1145-1185 DEG C, is preferably 1155-1175 DEG C.In addition, the thickness of the intermediate slab after described roughing can be 32-37mm, is preferably 32-35mm.
In addition, the start rolling temperature of described finish rolling can be 1120-1165 DEG C, is preferably 1135-1155 DEG C; The finishing temperature of described finish rolling can be 900-945 DEG C, is preferably 905-930 DEG C; The thickness of the intermediate slab after described finish rolling can be 2-5mm, is preferably 3-4.5mm.In order to reach the needed start rolling temperature of roughing of hot rolling, can before roughing, first continuously cast bloom be heated in heater to the required bundle temperature of opening when being heated to continuously cast bloom and carrying out roughing.The thickness of the intermediate slab obtaining after described hot rolling is the thickness of the intermediate slab after the described finish rolling here, and after referring to after described hot rolling that described finish rolling completes.
According to the present invention, under preferable case, after described hot rolling and before described batching, the intermediate slab obtaining is cooled to the temperature of batching with the speed of cooling of 22-28 DEG C/s after hot rolling.
According to the present invention, under preferable case, described cooling can being undertaken or air cooling by laminar flow water cooling, preferably adopts laminar flow water cooling.
According to the present invention, under preferable case, described in the temperature of batching be 735-765 DEG C.
According to the present invention, under preferable case, described cold rolling draft is 63-72%.
According to the present invention, under preferable case, the condition of described annealing comprises: soaking temperature is 845-880 DEG C, and soaking time is 48-65s.
In the present invention, in order to obtain the hot-dip galvanizing sheet steel that surface quality is more superior, preferably before annealing, the cold-rolled steel sheet to gained cleans.Described cleaning can adopt the purging method of the steel plate of this area routine, and for example alkali cleaning and/or electrolytic cleaning its objective is that greasy dirt in order to remove surface of cold-rolled steel plate, iron scale, iron powder etc. affect the impurity of plate surface quality.Preferably, the present invention first carries out alkali cleaning and electrolytic cleaning before described cold-rolled steel sheet is annealed.The condition optimization of described alkali cleaning comprises: the free alkalinity of scavenging solution is 70-90Pt, and temperature is 85-100 DEG C, and the time is 45-65s.Preferably, the condition optimization of described electrolytic cleaning comprises: the free alkalinity of scavenging solution is 70-85Pt, and temperature is 80-100 DEG C, and electric current is 7100-7500A, and the time is 50-70s.
The present invention also provides the cold-rolled steel sheet being made by above-mentioned preparation method.
The present invention also provides a kind of preparation method of hot-dip galvanizing sheet steel, and wherein, the method comprises adheres to upper zinc coating by above-mentioned cold-rolled steel sheet through galvanizing.
According to the present invention, described galvanizing can adopt continous way hot dipping method, also can adopt intermittent type hot dipping method, but in order to boost productivity and lumber recovery, the present invention preferably adopts continous way hot dipping method.The condition of the preferred described galvanizing of the present invention comprises: the temperature of zinc pot is 450-470 DEG C, more preferably 455-465 DEG C.
The amount of the zinc coating of the present invention to hot-dip galvanizing sheet steel there is no special restriction, can adjust according to the concrete requirement to steel plate galvanized, preferably, on every square metre of described hot-dip galvanizing sheet steel, the weight of described zinc coating is 120-270g, more preferably 150-260g, the zinc coating on the described hot-dip galvanizing sheet steel of here every square metre refers to the double-edged zinc coating of steel plate galvanized.
According to the present invention, described preparation method also comprises that the zinc melt on the steel plate to taking out from zinc pot purges, and makes the zinc coating on steel plate distribute more evenly, preferably adopts air knife to purge.The condition optimization that described air knife purges comprises: pressure 16-25KPa is highly 300-340mm, is 25-29mm apart from the vertical range of steel plate.
According to the present invention, described preparation method also comprise to purge after hot-dip galvanizing sheet steel carry out polishing and straightening, described polishing and straightening can adopt the method for this area routine, preferably, described polishing unit elongation is 0.4-0.8%.Preferably, described straightening unit elongation is 0.1-0.5%.More preferably only the hot-dip galvanizing sheet steel after purging is carried out to straightening processing, when only the hot-dip galvanizing sheet steel after purging being carried out straightening processing and do not carry out polishing processing, the steel plate that can the obtain good plate shape simultaneously intensity of this steel plate can remain on R
eLfor 250-300MPa and R
min the scope of>=360MPa.
According to the present invention, the preparation method of described hot-dip galvanizing sheet steel conventionally also comprises the steel plate of gained carried out to passivation, and the present invention preferably adopts chromium-free deactivation.Method to described passivation is not particularly limited, and can be the passivating method of this area routine.Preferably, described passivation is for adopting environmental protection chromium-free passivation liquid, by roll coating model, band steel is carried out to surface treatment, the condition of described passivation comprises: roller coat application roll is (128-136) with the roller speed ratio that dips in liquid roller: (70-85), top roll roll-in is 85-90daN, and lower roll roll-in is 70-80daN.Under this condition, can ensure that uniform film thickness is stable, there is no obvious aberration.
The present invention also provides the hot-dip galvanizing sheet steel being made by aforesaid method.
The yield strength R that the hot-dip galvanizing sheet steel making by method of the present invention can have
eLfor 250-300MPa, be preferably 260-290MPa; Tensile strength R
m>=360MPa, is preferably 360-400MPa; Elongation after fracture A
80>=36%, be preferably 36-39%; Plastic strain ratio r
90>=1.5, be preferably 1.6-2.3; Work hardening exponent n
90>=0.2, be preferably 0.21-0.25; Baking hardening value BH
2>=60MPa, is preferably 60-80MPa; More than the surface quality having is characterized as FC level; And the ferritic structure that microstructure is 100%, ferrite grain size is more than 8 grades, be preferably 8-11 level, ferrite grain size is 12-20 μ m, be preferably 14-19 μ m and cost lower, it is a kind of good super low carbon microalloy baking hardening steel plate galvanized, is particularly suitable for, as the steel plate of complicated and exposed component of manufacturing automobile and motorcycle, having good market outlook.
Below will describe the present invention by embodiment.
Yield strength R in following examples and comparative example
eL, tensile strength R
m, elongation after fracture A
80testing method carry out according to GBT228-2002 metallic substance tensile testing at ambient temperature; Plastic strain ratio r
90testing method carry out according to the measuring method of GBT5027-2007 metal sheet and strip plastic strain ratio (r value); Work hardening exponent n
90testing method carry out according to GBT5028-2008 metal sheet and strip tension strain hardenability value (n value) test method; Baking hardening value (BH
2) testing method carry out according to the part 1 baking hardened steel test method of GBT20564.1-2007 automobile high-strength cold continuous rolling steel plate and steel band; Adopt the method specifying in GB/T2518-2008 to judge the surface quality feature of hot-dip galvanizing sheet steel.
Embodiment 1
The present embodiment is used for illustrating cold-rolled steel sheet of the present invention and preparation method thereof and hot-dip galvanizing sheet steel and preparation method thereof.
At converter smelting, through LF stove Ca processing, RH decarburization and the thick slab of continuous casting acquisition 200mm, its moiety is in table 1.This heating of plate blank to 1189 DEG C is carried out to roughing, the finishing temperature of roughing is 1152 DEG C, the thickness of the intermediate slab after roughing is 33mm, again the intermediate slab after roughing is carried out to finish rolling again by Coil Box, the starting temperature of finish rolling is 1136 DEG C, the finishing temperature of finish rolling is 906 DEG C, and the thickness of the intermediate slab after finish rolling is 3.75mm; Adopt subsequently laminar flow water cooling to be cooled to 737 DEG C to batch the intermediate slab after hot rolling with the speed of cooling of 25 DEG C/s; Again on cold-rolling mill with 68% draft, be cold-rolled to the thickness of 1.2mm.With carrying out alkali cleaning and electrolytic cleaning by this cold-rolled steel sheet, alkali cleaning condition is: free alkalinity is controlled at 90Pt, and temperature is 87 DEG C, and the time is 64s; The condition of electrolytic cleaning is: free alkalinity is controlled at 79Pt, and temperature is 88 DEG C, and Faradaic current is controlled at 7200A, and the time is 59s.Then anneal (under the soaking temperature of 848 DEG C, carrying out soaking 60s), then enter the zinc pot of 460 DEG C.Steel plate goes out the laggard promoting the circulation of qi cutter of zinc pot and purges, and the condition that air knife purges is: pressure 24KPa is highly 320mm, is 28mm apart from the vertical range of steel plate.Carry out straightening and chromium-free deactivation, wherein, straightening unit elongation is 0.42% again; The condition of passivation comprises: roller coating machine is delivered to application roll by dipping in liquid roller by environment-friendly chromium-free passivating solution, then is rotated and be evenly coated in surface of steel plate by application roll.Roller coat application roll with dip in liquid roller roller speed ratio 130:80, top roll roll-in is 90daN, lower roll roll-in is 78daN.Obtain thus hot-dip galvanizing sheet steel, wherein, with respect to the cold-rolled steel sheet of every square metre, the weight of described zinc coating is 250g (two sides zinc coating).The strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 1 is shown in by the photo of its microstructure.
Embodiment 2
The present embodiment is used for illustrating cold-rolled steel sheet of the present invention and preparation method thereof and hot-dip galvanizing sheet steel and preparation method thereof.
At converter smelting, through LF stove Ca processing, RH decarburization and the thick slab of continuous casting acquisition 200mm, its moiety is in table 1.This heating of plate blank to 1195 DEG C is carried out to roughing, the finishing temperature of roughing is 1168 DEG C, the thickness of the intermediate slab after roughing is 32.4mm, again the intermediate slab after roughing is carried out to finish rolling again by Coil Box, the starting temperature of finish rolling is 1149 DEG C, the finishing temperature of finish rolling is 918 DEG C, and the thickness of the intermediate slab after finish rolling is 3.5mm; Adopt subsequently laminar flow water cooling to be cooled to 748 DEG C to batch the intermediate slab after hot rolling with the speed of cooling of 22 DEG C/s; Again on cold-rolling mill with 71% draft, be cold-rolled to the thickness of 1.0mm.With carrying out alkali cleaning and electrolytic cleaning by this cold-rolled steel sheet, alkali cleaning condition is: free alkalinity is controlled at 74Pt, and temperature is 89 DEG C, and the time is 49s; The condition of electrolytic cleaning is: free alkalinity is controlled at 79Pt, and temperature is 92 DEG C, and Faradaic current is controlled at 7500A, and the time is 68s.Then anneal (under the soaking temperature of 862 DEG C, carrying out soaking 48s), then enter the zinc pot of 455 DEG C.Steel plate goes out the laggard promoting the circulation of qi cutter of zinc pot and purges, and the condition that air knife purges is: pressure 16KPa is highly 310mm, is 25mm apart from the vertical range of steel plate.Carry out straightening and chromium-free deactivation, wherein, straightening unit elongation is 0.3% again; The condition of passivation comprises: roller coating machine is delivered to application roll by dipping in liquid roller by environment-friendly chromium-free passivating solution, then is rotated and be evenly coated in surface of steel plate by application roll.Roller coat application roll with dip in liquid roller roller speed ratio 128:79, top roll roll-in is 87daN, lower roll roll-in is 72daN.Obtain thus hot-dip galvanizing sheet steel, wherein, with respect to the cold-rolled steel sheet of every square metre, the weight of described zinc coating is 160g (two sides zinc coating).The strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 2 is shown in by the photo of its microstructure.
Embodiment 3
The present embodiment is used for illustrating cold-rolled steel sheet of the present invention and preparation method thereof and hot-dip galvanizing sheet steel and preparation method thereof.
At converter smelting, through LF stove Ca processing, RH decarburization and the thick slab of continuous casting acquisition 200mm, its moiety is in table 1.This heating of plate blank to 1208 DEG C is carried out to roughing, the finishing temperature of roughing is 1170 DEG C, the thickness of the intermediate slab after roughing is 33.7mm, again the intermediate slab after roughing is carried out to finish rolling again by Coil Box, the starting temperature of finish rolling is 1145 DEG C, the finishing temperature of finish rolling is 925 DEG C, and the thickness of the intermediate slab after finish rolling is 3.5mm; Adopt subsequently laminar flow water cooling to be cooled to 763 DEG C to batch the intermediate slab after hot rolling with the speed of cooling of 28 DEG C/s; Again on cold-rolling mill with 66% draft, be cold-rolled to the thickness of 1.5mm.With carrying out alkali cleaning and electrolytic cleaning by this cold-rolled steel sheet, alkali cleaning condition is: free alkalinity is controlled at 76Pt, and temperature is 94 DEG C, and the time is 58s; The condition of electrolytic cleaning is: free alkalinity is controlled at 80Pt, and temperature is 82 DEG C, and Faradaic current is controlled at 7400A, and the time is 53s.Then anneal (under the soaking temperature of 875 DEG C, carrying out soaking 55s), then enter the zinc pot of 465 DEG C.Steel plate goes out the laggard promoting the circulation of qi cutter of zinc pot and purges, and the condition that air knife purges is: pressure 18KPa is highly 300mm, is 27mm apart from the vertical range of steel plate.Carry out straightening and chromium-free deactivation, wherein, straightening unit elongation is 0.28% again; The condition of passivation comprises: roller coating machine is delivered to application roll by dipping in liquid roller by environment-friendly chromium-free passivating solution, then is rotated and be evenly coated in surface of steel plate by application roll.Roller coat application roll with dip in liquid roller roller speed ratio 133:82, top roll roll-in is 88daN, lower roll roll-in is 76daN.Obtain thus hot-dip galvanizing sheet steel, wherein, with respect to the cold-rolled steel sheet of every square metre, the weight of described zinc coating is 200g (two sides zinc coating).The strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 3 is shown in by the photo of its microstructure.
Embodiment 4
According to the method for embodiment 1, difference is, the steel plate after air knife is purged is carrying out first carrying out polishing before straightening, and polishing elongation control is 0.75%, the strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 4 is shown in by the photo of its microstructure.
Comparative example 1
According to the method for embodiment 1, difference is that the moiety difference of slab, is specifically shown in Table 1, the strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, plastic strain ratio r
90, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 5 is shown in by the photo of its microstructure.
Comparative example 2
According to the method for embodiment 1, difference is with the speed of cooling of 50 DEG C/s, the intermediate slab after hot rolling to be cooled to 737 DEG C and to batch, the strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, plastic strain ratio r
90, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 6 is shown in by the photo of its microstructure.
Comparative example 3
According to the method for embodiment 1, difference is that coiling temperature is 700 DEG C, the strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, plastic strain ratio r
90, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 7 is shown in by the photo of its microstructure.
Comparative example 4
According to the method described in embodiment 1, difference is that cold rolling draft is 50%, the strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, plastic strain ratio r
90, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 8 is shown in by the photo of its microstructure.
Comparative example 5
According to the method described in embodiment 1, difference is that the soaking temperature of described annealing is 780 DEG C, the strong R of surrender of gained hot-dip galvanizing sheet steel
eL, tensile strength R
m, elongation after fracture A
80, plastic strain ratio r
90, work hardening exponent n
90with baking hardening value BH
2in table 2, the measurement result of microstructure and surface quality feature is in table 3, and Fig. 9 is shown in by the photo of its microstructure.
Table 1
Table 2
Note: "---" in table represents not perfect recrystallization of steel plate, when tension test, sample is disconnected in advance, cannot measure n, r value.
Table 3
Note: "---" in table represents not perfect recrystallization of microstructure, cannot pass judgment on according to metallographic structure standard.
Data by table in 1-3 can be found out, adopt preparation method of the present invention, can obtain to have finished product mechanical property and reach yield strength R
eLfor 250-300MPa, tensile strength R
m>=360MPa, elongation after fracture A
80>=36%, plastic strain ratio r
90>=1.5, work hardening exponent n
90>=0.2, baking hardening value BH
2ferritic structure, the ferrite grain size that>=60MPa, surface quality feature FC level are above, microstructure is 100% is that 8 grades of above and ferrite grain sizes are the hot-dip galvanizing sheet steel of 12-20 μ m.
More than describe the preferred embodiment of the present invention in detail; but the present invention is not limited to the detail in above-mentioned embodiment, within the scope of technical conceive of the present invention; can carry out multiple simple variant to technical scheme of the present invention, these simple variant all belong to protection scope of the present invention.
It should be noted that in addition, each concrete technical characterictic described in above-mentioned embodiment, in reconcilable situation, can combine by any suitable mode, for fear of unnecessary repetition, the present invention is to the explanation no longer separately of various possible array modes.
In addition, also can carry out arbitrary combination between various embodiment of the present invention, as long as it is without prejudice to thought of the present invention, it should be considered as content disclosed in this invention equally.
Claims (11)
1. a preparation method for cold-rolled steel sheet, the method comprises: by slab successively through hot rolling, batch, cold rolling and annealing, it is characterized in that,
After described hot rolling and before described batching, the intermediate slab obtaining is cooled to the temperature of batching with the speed of cooling of 20-30 DEG C/s after hot rolling;
Described temperature of batching is 730-780 DEG C;
Described cold rolling draft is 60-75%;
The condition of described annealing comprises: soaking temperature is 840-890 DEG C, and soaking time is 40-70s;
Consisting of of described slab: C:0.001-0.005 % by weight, Si:0.01-0.05 % by weight, Mn:0.2-0.7 % by weight, P:0.03-0.08 % by weight, S :≤0.02 % by weight, Al:0.01-0.08 % by weight, Ti:0.001-0.02 % by weight, Nb:0.003-0.03 % by weight, surplus is Fe and inevitable impurity.
2. method according to claim 1, wherein, consisting of of described slab: C:0.002-0.005 % by weight, Si:0.01-0.04 % by weight, Mn:0.3-0.65 % by weight, P:0.035-0.07 % by weight, S:0.007-0.015 % by weight, Al:0.03-0.07 % by weight, Ti:0.008-0.018 % by weight, Nb:0.007-0.02 % by weight, surplus is Fe and inevitable impurity.
3. method according to claim 1, wherein, after described hot rolling and before described batching, is cooled to the intermediate slab obtaining after hot rolling the temperature of batching with the speed of cooling of 22-28 DEG C/s.
4. according to the method described in claim 1 or 3, wherein, described in the temperature of batching be 735-765 DEG C.
5. method according to claim 1, wherein, described cold rolling draft is 63-72%.
6. method according to claim 1, wherein, the condition of described annealing comprises: soaking temperature is 845-880 DEG C, soaking time is 48-65s.
7. method according to claim 1, wherein, described hot rolling comprises roughing and finish rolling, described roughing open prick temperature be 1185-1230 DEG C, the finishing temperature of described roughing is 1145-1185 DEG C; The start rolling temperature 1120-1165 DEG C of described finish rolling, the finishing temperature of described finish rolling is 900-945 DEG C.
8. the cold-rolled steel sheet being made by the method described in any one in claim 1-7.
9. a preparation method for hot-dip galvanizing sheet steel, is characterized in that, the method comprises adheres to upper zinc coating by cold-rolled steel sheet claimed in claim 8 through galvanizing.
10. preparation method according to claim 9, wherein, on every square metre of described hot-dip galvanizing sheet steel, the weight of described zinc coating is 120-270g.
11. the hot-dip galvanizing sheet steel being made by the preparation method described in claim 9 or 10.
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