CN104328349A - High-strength medium-carbon low-silicon aluminum cold-rolled dual-phase steel and production method - Google Patents

Abstract

The invention provides high-strength medium-carbon low-silicon aluminum cold-rolled dual-phase steel. The high-strength medium-carbon low-silicon aluminum cold-rolled dual-phase steel is prepared from the following components in percentage by weight: 0.185-0.28% of C, 0.01-0.02% of Si, 1.5-2.5% of Mn, 1.12-1.5% of Cr, 0.2-0.3% of Al, less than 0.005% of S, less than 0.01% of P and less than 0.01% of N. The production method comprises the following production steps: smelting, continuously casting to form a blank conventionally heating the cast blank, and then performing hot rolling on a cast blank; winding; performing cold rolling after conventional acid pickling; annealing before zinc plating; cooling; evenly preserving heat; performing zinc plating; performing air cooling until the temperature reaches a room temperature. According to the production method of the high-strength medium-carbon low-silicon aluminum cold-rolled dual-phase steel, the medium carbon component is combined with low silicon, low manganese and high chromium for alloy compounding strengthening, and therefore, the surface enrichment oxidization degree of the alloy elements can be effectively reduced, the zinc platability of the steel plate can be improved, and the tensile strength of the steel plate is improved to 800MPa and above under the premise of guaranteeing no reduction in automobile safety; as a result, the development requirements on light weight and high strength of automobiles are met.

Description

The system cold-rolled dual phase steel of the low sial of carbon and production method in a kind of high strength

Technical field

The present invention relates to a kind of automobile steel and production method, belong to the system cold-rolled dual phase steel of the low sial of carbon and production method in a kind of high strength of automobile particularly.

Background technology

Dual phase steel is a kind of advanced high-strength steel based on phase transformation strengthening, and microtexture adds tough martensite by the ferrite of high ductility and formed.Unique weave construction defines the premium properties features such as the yield-point of dual phase steel in mechanical property is low, intensity is high, initial manufacture hardening rate is high and strength and ductility is worked good, the features such as high intensity and work hardening exponent, low yield strength ratio and good bake hardenability, have become the New Type Punching Steel that a kind of intensity high formability is good.

Because dual phase steel combines the requirement that intensity is high, plasticity is good of automobile high-strength steel, be therefore widely used in structural part and the safety member of Hyundai Motor manufacture, to improve vehicle body security and to realize body lightening.Research finds, is ensureing that under the prerequisite that vehicle safety does not reduce, the intensity of material brings up to 600MPa from 200MPa, then automobile can realize loss of weight about 13%.Along with automotive light weight technology designs the enforcement with development and ultralight steel car body research project, with dual phase steel be the novel high-strength automobile steel [4-8] of representative development & application research be widely applied and development, and product strength rank also constantly promotes, wherein have with DP600, DP800 consumption maximum.

Through retrieval, Chinese Patent Application No. is CN201110071272.7 patent documentation, it discloses C:0.10 ~ 0.18%, Si:0.03 ~ 0.19%, Mn:2.6 ~ 3.0%, Als:0.01 ~ 0.04%, Cr:0.15 ~ 0.9%; Number of patent application is CN201110071272.7 patent documentation C:0.06%-0.08%; Si:1.0%-1.3%; Mn:2.1%-2.3%; P≤0.01%; S≤0.01%; Alt:0.02%-0.07%; N≤0.005%.Because alloying element content is high, particularly Si, Mn alloy, causes surface oxidation enrichment, causes galvanized sheet surface quality to worsen.

The deficiency such as surface enrichment oxidation so that coating adhesion difference is caused because the alloying element contents such as Si, Mn are high for existing most product, the applicant has carried out the 800MPa level cold-rolled biphase steel laboratory study of a kind of middle carbon low sial chromium system, on the basis that mechanical property is up to standard, adherence of coating improves greatly.The present invention can be used for the processing and manufacturing of the multiple forming mode part of automobile, and can meet the requirement of domestic automobile lightweight and raising security, its economic benefit and social benefit are very remarkable.

Summary of the invention

The present invention is directed to prior art and cause the deficiency such as surface enrichment oxidation so that coating adhesion difference because the alloying element contents such as Si, Mn are high, there is provided a kind of and carry out alloy complex intensifying by carbon component in employing and low silicon, low manganese, Gao Ge, effectively can reduce alloying element surface enrichment degree of oxidation, what promote steel plate can zinc-plated ability, ensureing under the prerequisite that vehicle safety does not reduce, its tensile strength is increased to 800MPa and more than, meet automotive light weight technology, the system cold-rolled dual phase steel of the low sial of carbon and production method in the high strength of the demand for development of high strengthening.

Realize the measure of above-mentioned purpose:

The system cold-rolled dual phase steel of the low sial of carbon in a kind of high strength, its component and weight percent content are: C:0.185 ~ 0.28%, Si:0.01 ~ 0.02%, Mn:1.5 ~ 2.5%, Cr:1.12 ~ 1.5%, Al:0.2 ~ 0.3%, S<0.005%, P<0.01%, N<0.01%, and surplus is Fe and inevitable impurity.

Preferably: the weight percent content of C is 0.208 ~ 0.256 %.

Preferably: the weight percent content of Mn is 1.6 ~ 1.9 %.

Preferably: the weight percent content of Cr is 1.16 ~ 1.46 %.

Produce the method for the system cold-rolled dual phase steel of the low sial of carbon in a kind of high strength, its step:

1) become base and routine to carry out hot rolling to after strand heating through smelting, continuous casting, wherein, control finish rolling finishing temperature at 800 ~ 900 DEG C;

2) batch, control coiling temperature at 560 ~ 660 DEG C;

3) cold rolling after conventional pickling, control its total reduction 50 ~ 70%;

4) carry out zinc-plated front annealing, control its soaking holding temperature at 780 ~ 840 DEG C, annealing time is 180 ~ 240s;

5) cool, under speed of cooling is 15 ~ 25 DEG C/s, is cooled to 470 ~ 520 DEG C;

6) equilibrium insulation is carried out, balanced 3 ~ 5s at temperature is 460 ~ 465 DEG C;

7) carry out zinc-plated, control zinc liquid temperature at 458 ~ 462 DEG C;

8) air-cooled to room temperature.

The effect of each element in the present invention:

C: be the most effective strengthening element, be form martensitic principal element, in steel, carbon content determines the hardness of dual phase steel and martensitic pattern; Carbon belongs to the strongest a kind of solution strengthening element, and increase the intensity that carbon content can significantly improve steel, meanwhile, carbon is also a kind of austenite stable element, effectively improves austenitic condensate depression.In order to improve steel grade martensite content, guaranteeing under the prerequisite not affecting welding property, carbon component design during the present invention adopts.

Mn: belong to typical austenite stabilizer element, significantly improves the hardening capacity of steel, and plays the effect of solution strengthening and fining ferrite grains, can significantly postpone perlitic transformation and bainite transformation.But Mn is as the element expanding γ phase region, when high Mn content is while postponement perlitic transformation, also ferritic precipitation can be postponed; And Mn content is too low easily causes perlitic transformation.Meanwhile, manganese element is very easily oxidized at surface of steel plate, can zinc-plated ability impact steel plate.In order to improve the platability of steel plate, present invention employs the design of low manganese.

Si is ferritic solution strengthening element, and it accelerates carbon to austenitic segregation, has " removing " and " purification " to act on to the solid solution carbon in ferrite, and when reducing gap solution strengthening and can suppress to cool, the generation of thick carbide, improves the ductility of dual phase steel.But Si too high levels makes troubles to hot rolling surface quality and coating, and affecting steel plate can zinc-plated ability.In order to improve the platability of steel plate, present invention employs the design of low silicon.

Cr is middle carbide, significantly improves the hardening capacity of steel, can strongly postpone perlitic transformation and bainite transformation, and expand " batching window ".Though Cr is weak solution strengthening element, can increases and austeniticly cross cold energy power, thus thinning microstructure, strengthened effect.

Al: belong to closed austenite phase field element, can Ac be improved ₁, reduce Ac simultaneously ₃, ferrite and austenitic two-phase region can be expanded, strengthen the handiness of thermal treatment process, contribute to the stability and the circulation ratio that keep dual phase steel performance, just based on this effect of Al in element, invention increases the content of the aluminium in steel; What is more important, Al effectively can improve Ms (martensite start) point Ms point, promotes the acquisition of martensitic stucture; Meanwhile, Al is higher content strengthening element, and the precipitation of AlN can play certain grain refining intensificatiom effect.Al has with Si the same, can promote Carbon diffusion in ferrite, effectively can play the ferritic effect of purification.

The present invention compared with prior art, alloy complex intensifying is carried out by carbon component and low silicon, low manganese, Gao Ge in adopting, effectively can reduce alloying element surface enrichment degree of oxidation, what promote steel plate can zinc-plated ability, ensureing under the prerequisite that vehicle safety does not reduce, its tensile strength is increased to 800MPa and more than, meet automotive light weight technology, the demand for development of high strengthening.

Embodiment

Below the present invention is described in detail:

Table 1 is the chemical composition value list of various embodiments of the present invention and comparative example;

Table 2 is the main technologic parameters list of various embodiments of the present invention and comparative example;

Table 3 is various embodiments of the present invention and the list of comparative example Performance Detection situation.

Various embodiments of the present invention are produced according to following steps:

1) become base and routine to carry out hot rolling to after strand heating through smelting, continuous casting, wherein, control finish rolling finishing temperature at 800 ~ 900 DEG C;

2) batch, control coiling temperature at 560 ~ 660 DEG C;

3) cold rolling after conventional pickling, control its total reduction 50 ~ 70%;

4) carry out zinc-plated front annealing, control its soaking holding temperature at 780 ~ 840 DEG C, annealing time is 180 ~ 240s;

5) cool, under speed of cooling is 15 ~ 25 DEG C/s, is cooled to 470 ~ 520 DEG C;

6) equilibrium insulation is carried out, balanced 3 ~ 5s at temperature is 460 ~ 465 DEG C;

7) carry out zinc-plated, control zinc liquid temperature at 458 ~ 462 DEG C;

8) air-cooled to room temperature.

The chemical composition value list (wt%) of table 1. various embodiments of the present invention and comparative example

The main technologic parameters list of table 2. various embodiments of the present invention and comparative example

Note: table 1 is not one_to_one corresponding with the value in table 2, is only citing.

Table 3. various embodiments of the present invention and the list of comparative example Performance Detection situation

As can be seen from Table 3, production technique adaptability of the present invention is good, good mechanical performance, and has good high strength galvanized steel.

Above-described embodiment is only the best and exemplifies, and is not the restriction to embodiments of the present invention.

Claims (5)

1. the system cold-rolled dual phase steel of the low sial of carbon in a high strength, its component and weight percent content are: C:0.185 ~ 0.28%, Si:0.01 ~ 0.02%, Mn:1.5 ~ 2.5%, Cr:1.12 ~ 1.5%, Al:0.2 ~ 0.3%, S<0.005%, P<0.01%, N<0.01%, and surplus is Fe and inevitable impurity.

2. the system cold-rolled dual phase steel of the low sial of carbon in a kind of high strength as claimed in claim 1, is characterized in that: the weight percent content of C is 0.208 ~ 0.256 %.

3. the system cold-rolled dual phase steel of the low sial of carbon in a kind of high strength as claimed in claim 1, is characterized in that: the weight percent content of Mn is 1.6 ~ 1.9 %.

4. the system cold-rolled dual phase steel of the low sial of carbon in a kind of high strength as claimed in claim 1, is characterized in that: the weight percent content of Cr is 1.16 ~ 1.46 %.

5. the method for the system cold-rolled dual phase steel of the low sial of carbon in a kind of high strength described in production claim 1, its step:

1) become base and routine to carry out hot rolling to after strand heating through smelting, continuous casting, wherein, control finish rolling finishing temperature at 800 ~ 900 DEG C;

2) batch, control coiling temperature at 560 ~ 660 DEG C;

3) cold rolling after conventional pickling, control its total reduction 50 ~ 70%;

4) carry out zinc-plated front annealing, control its soaking holding temperature at 780 ~ 840 DEG C, annealing time is 180 ~ 240s;

5) cool, under speed of cooling is 15 ~ 25 DEG C/s, is cooled to 470 ~ 520 DEG C;

6) equilibrium insulation is carried out, balanced 3 ~ 5s at temperature is 460 ~ 465 DEG C;

7) carry out zinc-plated, control zinc liquid temperature at 458 ~ 462 DEG C;

8) air-cooled to room temperature.