A kind of tensile strength 800MPa level contains the production method of the cold-rolled galvanized duplex steel of Si
Technical field
The present invention relates to cold rolling hot dip galvanizing automobile steel manufactures field and in particular to a kind of tensile strength 800MPa level contains Si
Cold-rolled galvanized duplex steel production method.
Background technology
With the development of auto industry, energy-saving, increase safety and reliability, raising car body corrosion resisting property have become use
The generally pursuit at family, has become the inexorable trend of automobile steel development using high-strength galvanized sheet.
Dual phase steel is the high-strength steel that current automobile industry is most widely used, and automobile dual phase steel is different according to processing route
It is divided into hot-rolled dual-phase steel, cold-rolled biphase steel and cold-rolled galvanized duplex steel etc., wherein to have the ferrite/geneva of duplex structure
Body dual phase steel is most representative.Because Galvanized Dual Phase Steel not only has cold-rolled biphase steel high intensity, low yield strength ratio and good formability,
Also there is good antiseptic property, study at present and apply most and the most ripe zinc-plated DP600.With auto industry to subtracting
The important raising further asked, tensile strength can ensure peace in the superhigh intensity Galvanized Dual Phase Steel of 800MPa and its above rank
Entirely, reduce parts thickness on the premise of corrosion resisting property, realize greatly automotive light weight technology.Zinc-plated DP800 is main at present
Be applied to door anti-collision joist, seat support, safety member and the structural member such as floor beams.
By rational composition and technological design it is ensured that tissue in ferrite and martensite content and proportioning, control horse
Family name's body and ferrite disperse degree and distribution, thus obtain 800MPa level two-phase product made from steel of good performance of science, simultaneously
The impact to Coating of composition to be considered and technique.During exploitation 800MPa grade high-strength cold-rolled galvanized duplex steel, by closing
The composition of reason and technological design it is ensured that the requirement of Mechanical Properties of Dual Phase Steels, weldability, forming property and excellent surface quality,
Reduce the usage amount reduces cost of microalloy element simultaneously as far as possible.
Carry out patent retrieval for 800MPa level Galvanized Dual Phase Steel, composition is with present invention contrast as shown in table 1.Each invention
Feature is specific as follows:
In the patent of Application No. CN01807327.1, it discloses high strength dual phase sheet metal and high strength dual phase plating
Sheet metal and its manufacture method, the wherein chemical composition for 780MPa level dual phase steel flat cold-rolled sheet are:C:0.04%, Si:
0.7%, Mn:2.6%, V:0.02%~0.06%, Nb:0.01%~0.12%, Ti:0.01%~0.12%, S≤
0.055%, P≤0.040%, Als:0.04%, balance of Fe;Pass through silicon low-carbon high in this patent and interpolation Nb, V, Ti is micro-
The composition design thinking that one or more of alloy is carried out, obtains a kind of thin steel of high intensity with good drawability
Plate.Its zincincation is partial to electrogalvanizing, would generally cause Coating degradation for high Si (Si >=0.20%).This article
In do not indicate how to avoid the concrete scheme of this problem, but commonly used pre-oxidation-reduction technique or surface flash at present
Method solve high Si surface oxidation.
The patent documentation of Application No. CN200410084680.6 disclose a kind of 800MPa cold-rolled galvanized duplex steel and
Its manufacture method, steel plate chemical composition degree is:C:0.06~0.18%, Si≤0.40%, Mn:1.3~2.5%,
Cr:0.1~1.0%, Mo:0.02~0.5%, Nb:0.005%~0.03%, Ti:0.005~0.05%, S < 0.01%, P+
2S≤0.12%, C+Si/30+Mn/20≤0.24%, T.Al:0.02~0.05%, balance of Fe and inevitable impurity.Move back
Fiery temperature is 800~860 DEG C, preferably 815~840 DEG C of recrystallization annealing temperature.
The patent documentation of Application No. CN201110439563.7 discloses a kind of 780MPa grade cold rolling hot dip galvanizing dual phase steel
And preparation method thereof, its chemical composition is:C:0.10~0.15%, Si:≤ 0.05%, Mn:1.8~2.0%, Cr:0.2~
0.35%, Nb:0.03%~0.04%, Mo:0.2%~0.25%, S < 0.01%, P < 0.01%, Alt:0.02~
0.07%, N:≤ 0.005% balance of Fe and impurity.In this patent, recrystallization annealing temperature is 790~830 DEG C, is first cooled to
720 DEG C~760 DEG C, then blow again and be cooled to 450 DEG C~460 DEG C of zinc-plated temperature soon.
The patent documentation of Application No. CN201510968633.6 discloses a kind of 800MPa level car Galvanized Dual Phase Steel
And production method, its chemical composition is:C:0.06~0.010%, Si:≤ 0.1%, Mn:1.5%~2.5%, Cr:0.02%
~0.9% or Mo:0.01%~0.30%, P≤0.015%, S≤0.010%, N:≤ 0.005%, Nb:0.001%~
0.03%, Als:0.01%~0.08%.Crucial annealing temperature is 790 DEG C~850 DEG C.
The synopsis (wt%) that table 1 present component system is invented with other
Namely there are the following problems in prior art:Galvanized Dual Phase Steel not only have cold-rolled biphase steel high intensity, low bend strong
Than with good formability, also there is good antiseptic property, extensive as typical trade mark 800MPa level hot dip galvanized dual phase steel
Be applied to door anti-collision joist, seat support, safety member and the structural member such as floor beams.Generally high Si component system needs to adopt at present
Avoid the surface quality that high Si causes poor with the mode such as pre-oxidation-reduction technique or flash Ni, higher to equipment requirements, lead to
Often need scrap build or newly-built producing line just to enable, and improvement cost is higher, be not easy to realize.In addition no Si becomes split
System, makes up the effect of Si by needing to add the alloy such as Cr, Mo, Nb, Ti, thus realizing good combination property and good
Surface quality.Virtually increasing cost, the interpolation of multiple alloying elements simultaneously is to technology controlling and process it is also proposed that higher requirement for this.
Content of the invention
For above prior art problem, it is an object of the invention to provide a kind of tensile strength 800MPa level contains the cold of Si
Roll the production method of hot dip galvanized dual phase steel, by, on the premise of ensureing coating surface quality, increasing cost as far as possible relatively low
Si element addition, it is to avoid the interpolation of other relatively costly alloying elements, steel-making region adopt LF+RH duplex control protect
Card composition accurately hits, and controls inclusion content, and continuous casting zone adopts the advanced production technology such as dynamic soft-reduction and electromagnetism roller, subtracts
Few strand component segregation and the defect of center porosity, anti-coordinating rational hot rolling, continuous annealing process and zincincation to be obtained in that
Tensile strength more than 780MPa, elongation percentage be higher than 14% high intensity Galvanized Dual Phase Steel it is ensured that good mechanical property and coating
Quality, formability and welding performance.Concrete technical scheme is as follows:
A kind of tensile strength 800MPa level contains the cold-rolled galvanized duplex steel of Si, and its chemical composition mass percent is:C:
0.08~0.12%, Si:0.10~0.18%, Mn:1.5~2.5%, Cr:0.2~0.4%, Mo:0.12~0.20%, Als:
0.03-0.06%, P≤0.015%, S≤0.04%, N:≤ 0.005%, balance of Fe and inevitable impurity.
The preparation technology that above-mentioned tensile strength 800MPa level contains the cold-rolled galvanized duplex steel of Si comprises the steps:
(1) smelt and solidification;
(2) hot continuous rolling of strand or ingot casting;
(3) pickling and cold-rolling;
(4) continuous annealing is zinc-plated.
Further, further include step (5):Alloying.
Further, adopt converter, electric furnace and induction furnace to smelt in step (1), and adopt continuous casting strand.
Further, in step (2), strand is heated through 1200~1250 DEG C, 5-7 passes is carried out by roughing mill,
Hot rolling, to 20-40mm thickness specification, carries out 5-7 passes by hot tandem, is rolled to after target thickness in 620-670 DEG C of model
Carry out in enclosing coiling into coil of strip.
Further, in step (3), by hot-strip through hydrochloric acid trough pickling, after removing scale on surface, carry out cold company
Roll or cold rolling, cold rolling reduction ratio >=50%, be rolled to target thickness.
Further, comprise the steps in step (4):
(4-1) cold-strip steel is heated slowly to 180 DEG C of preheatings;
(4-2) strip steel through preheating is heated to 770~820 DEG C, and cold rolling pearlite and ferrite occur in the process
Recrystallization, when temperature is more than Ac1When begin with austenite produce;
(4-3) strip steel after heating carries out two-phase section annealing in 780~820 DEG C of insulation 60~120s;
(4-4) strip steel after insulation is adopted two-stage cooling:
A. 670~710 DEG C are slowly cooled to;
B. strip steel is cooled to soon 470~500 DEG C;
(4-5) strip steel carries out galvanizing at 450~470 DEG C, and zinc liquid temperature controls at 455~465 DEG C;
(4-6) it is cooled to 200 DEG C or lower with the cooldown rate of 5 DEG C/more than s again after going out zinc pot.
Further, in step (5), zinc-plated rear strip steel is heated to 500~530 DEG C and carries out Alloying Treatment, go out zinc
It is cooled to 200 DEG C or lower with the cooldown rate of 5 DEG C/more than s again after pot.
Further, in step (1) using continuous casting strand when come into operation dynamic soft-reduction and electromagnetic stirring system.
Compared with currently available technology, the present invention passes through Design of Chemical Composition with reference to cold rolling, hot rolling, continuous annealing, hot dip
Zinc technology controls, and ensure that the steady production of steel plate.The steel being produced, yield strength is 426MPa~540MPa, and tension is strong
Spend for >=800MPa, elongation percentage >=15%, have the characteristics that cost economy, equipment is simple, products application performance is good.According to current
Market situation, 800MPa level hot dip galvanized dual phase steel product ton steel profit is about 1000 yuan, and current year sells about 2000 tons, accumulative year
The new profit is roughly equal to 2,000,000 yuan.
Brief description
Fig. 1 is continuous hot galvanizing process schematic representation (GI:Pure zinc product, GA:Zn-Fe alloying product)
Fig. 2 (a) (b) is product metallographic structure figure
Specific embodiment
Describe the present invention below according to accompanying drawing, it is that one of numerous embodiments of the present invention are preferably real
Apply example.
In a preferred embodiment, a kind of 800MPa level economical hot dip galvanized dual phase steel steel plate containing Si, its chemistry becomes
Point mass percent is:C:0.08~0.12%;Si:0.10~0.18%;Mn:1.5~2.5%;Cr:0.2~0.4%;Mo:
0.12~0.20%;Als:0.03-0.06%, P≤0.015%, S≤0.04%, N:≤ 0.005%, balance of Fe and can not
The impurity avoiding.
The preparation method of the present invention, comprises the following steps successively:
(1) smelt and solidification:It is applied to converter, electric furnace and induction furnace to smelt;Using continuous casting strand, for ensureing strand
Quality can come into operation dynamic soft-reduction and electromagnetic stirring system;
(2) hot continuous rolling of strand or ingot casting:Strand is heated through 1200~1250 DEG C, 5-7 passage is carried out by roughing mill and rolls
System, hot rolling to 20-40mm thickness specification, 5-7 passes are carried out by hot tandem, is rolled to after target thickness in 620-670
Carry out in the range of DEG C coiling into coil of strip;
(3) pickling and cold-rolling:By hot-strip through hydrochloric acid trough pickling, after removing scale on surface, carry out cold continuous rolling or cold
Roll, cold rolling reduction ratio >=50%, be rolled to target thickness.
(4) continuous annealing is zinc-plated:Cold-strip steel is heated slowly to 180 DEG C of preheatings first, further through the strip steel of preheating
It is heated to (770~820) DEG C, cold rolling pearlite and ferrite recrystallize in the process, when temperature is more than Ac1When start
Austenite is had to produce.Strip steel after heating carries out two-phase section annealing in (780~820) DEG C insulation (60~120) s.After being incubated
Strip steel adopt two-stage cooling:Slowly cool to (670~710) DEG C first, then strip steel is cooled to (470~500) DEG C soon.
Strip steel carries out galvanizing in (450~470) DEG C, and usual zinc liquid temperature controls in (455~465) DEG C;Go out after zinc pot again with 5 DEG C/s
Above cooldown rate is cooled to 200 DEG C or lower.
(5) alloying:Zinc-plated rear strip steel is heated to (500~530) DEG C and carries out Alloying Treatment, go out after zinc pot again with
The cooldown rate of 5 DEG C/more than s is cooled to 200 DEG C or lower.
In a further advantageous embodiment, a kind of 800MPa level economical hot dip galvanized dual phase steel steel plate containing Si, its chemistry
Composition quality percent is:C:0.08~0.12%;Si:0.10~0.18%;Mn:1.5~2.5%;Cr:0.2~0.4%;
Mo:0.12~0.20%;Als:0.03-0.06%, P≤0.015%, S≤0.04%, N:≤ 0.005%, balance of Fe and not
Evitable impurity.
Preparation method comprises the following steps successively:
(1) smelt and solidification:It is applied to converter, electric furnace and induction furnace to smelt;Using continuous casting strand, for ensureing strand
Quality can come into operation dynamic soft-reduction and electromagnetic stirring system;
(2) hot continuous rolling of strand or ingot casting:Strand is heated through 1200~1250 DEG C, 5-7 passage is carried out by roughing mill and rolls
System, hot rolling to 20-40mm thickness specification, 5-7 passes are carried out by hot tandem, is rolled to after target thickness in 620-670
Carry out in the range of DEG C coiling into coil of strip;
(3) pickling and cold-rolling:By hot-strip through hydrochloric acid trough pickling, after removing scale on surface, carry out cold continuous rolling or cold
Roll, cold rolling reduction ratio >=50%, be rolled to target thickness.
(4) continuous annealing is zinc-plated:Cold-strip steel is heated slowly to 180 DEG C of preheatings first, further through the strip steel of preheating
It is heated to (770~820) DEG C, cold rolling pearlite and ferrite recrystallize in the process, when temperature is more than Ac1When start
Austenite is had to produce.Strip steel after heating carries out two-phase section annealing in (780~820) DEG C insulation (60~120) s.After being incubated
Strip steel adopt two-stage cooling:Slowly cool to (670~710) DEG C first, then strip steel is cooled to (470~490) DEG C soon.
Strip steel carries out galvanizing in (450~470) DEG C, and usual zinc liquid temperature controls in (455~465) DEG C;Go out after zinc pot again with 5 DEG C/s
Above cooldown rate is cooled to 200 DEG C or lower.
(5) alloying:Zinc-plated rear strip steel is heated to (500~530) DEG C and carries out Alloying Treatment, go out after zinc pot again with
The cooldown rate of 5 DEG C/more than s is cooled to 200 DEG C or lower.
C:One of maximally effective intensified element, the formation for martensite plays a crucial role, and in steel, carbon content determines two-phase
The intensity rank of steel and the performance of martensite;Due to the design requirement of martensite content and quenching degree, the two-phase of this rank intensity
Steel C content is typically between 0.06~0.18%.In the present invention, the Composition Control of C is in the relatively low scope of (0.08~0.12) %.
Si:Ferrite former, plays the effect of solution strengthening, in two-phase section insulation and slow cooling, can effectively facilitate C
To the bulk diffusion effect of Ovshinsky, there is significant purification to ferrite, improve ferrite degree of purity in dual phase steel, stable Austria
Family name's body is organized;On the other hand, Si content exceedes and easily forms refractory oxide in surface of steel plate during certain limit, thus affecting into
Product Coating effect, will rationally control the addition of Si, so Si weight percentage of the present invention controls in Si:(0.1~
0.18) %.
Mn:Improve the stability of austenite, thus dramatically increasing quenching degree, Mn also functions to solution strengthening and refinement ferrum element
The effect of body crystal grain.On the other hand, Mn is to expand γ p-block element p, when high manganese content makes the perlitic transformation time started postpone
Meanwhile, ferritic precipitation can also be slowed down;And the too low quenching degree that can not meet of manganese content requires, so Mn weight hundred of the present invention
Divide and control in (1.5~2.5) % than content.
Cr:Middle carbide, the quenching degree that can improve steel the same with Mn element, with the collocation of other alloying elements
Add in steel, the quenching degree of steel can be greatly improved, thus postponing perlitic transformation and bainite transformation, and expand and batch window
Mouthful, Cr is also a kind of solution strengthening element, plays the invigoration effect to matrix.On the other hand, too high Cr content, can make steel
Quenching degree greatly improves, so that intensity greatly increases, is degrading formability and the weldability of steel.Therefore preferably Cr content should
Control within (0.2~0.4) %.
Als:Effect played in dual phase steel for the Al is similar to Si, and Al also can form AlN and separate out simultaneously, plays certain thin
Change the effect of crystal grain.The presence of a small amount of Al is it is ensured that on the premise of strength character, can make the extension property of dual phase steel improve.So
Al weight percent content of the present invention controls in (0.03-0.06) %.
P、S、N:For reducing the harmful effect of the punching performance to steel for the objectionable impurities in steel, strict P, S, N controlling in steel
Content.
The main feature of the present invention:In patent of the present invention, composition design rationally, does not add noble metal alloy in a large number, less
C content and a small amount of alloying element it is ensured that good welding performance, and composition can meet large-scale production control.Pass through
The control (control of LF+RH duplex and dynamic soft-reduction and electromagnetic agitation) in steel area ensure that the essence of slab quality and alloying element
Really hit.Hot-rolled area, by the way of high temperature rolling low temperature batches, quick cools down, it is to avoid the product of hot-rolled area banded structure
Raw.The interpolation of the elements such as Si, Cr, Mo can ensure that the stability of austenite and avoids the excessive life of bainite after subsequently plating
Become, thus ensure that typical ferrite and martensite duplex structure it is ensured that the ductility of dual phase steel and low yield tensile ratio.Close simultaneously
Reason adds silicon addition, the easily Surface Segregation element such as Mn, Cr it is ensured that while having good combination property, also ensureing zinc-plated
Finished product has preferable surface quality.
The present invention compared with prior art, the 800MPa level hot dip galvanized dual phase steel that produced, yield strength be 420MPa~
550MPa, tensile strength is >=780MPa, pure zinc elongation percentage >=14% (zinc-iron alloy elongation percentage >=12%), surface quality grades
Reach FB surface.Have the characteristics that cost economy, equipment is simple, product good combination property.
Below in conjunction with the accompanying drawings the feature of the present invention is further described:The chemical composition of steel is as shown in table 2.Its preparation
Technique is:
(1) smelt and solidification:It is applied to converter, electric furnace and induction furnace to smelt;Using continuous casting strand, for ensureing strand
Quality can come into operation dynamic soft-reduction and electromagnetic stirring system;
(2) hot continuous rolling of strand or ingot casting:By strand through (1200-1250) DEG C heating, 5~7 passages are carried out by roughing mill
Rolling, hot rolling to 30mm~50mm thickness specification, 5~7 passes are carried out by hot tandem, be rolled to after target thickness
(620-670) carry out coiling into coil of strip in the range of DEG C;
(3) pickling and cold-rolling:By hot-strip through hydrochloric acid trough pickling, after removing scale on surface, carry out cold continuous rolling or cold
Roll, cold rolling reduction ratio is >=50%, is rolled to target thickness.
(4) continuous annealing galvanizing:Sample after acid is rolled, continuous annealing and zincincation and corresponding properties of product are such as
Shown in table 2.
Table 2 embodiment
Above in conjunction with accompanying drawing, the present invention is exemplarily described it is clear that the present invention implements is not subject to aforesaid way
Restriction, as long as employing method of the present invention design and the various improvement that carry out of technical scheme, or not improved direct application
In other occasions, all within protection scope of the present invention.