CN101096739A

CN101096739A - Stamping high-strength heating galvanized steel with excellent welding performance and method for manufacturing the same

Info

Publication number: CN101096739A
Application number: CNA2006100282450A
Authority: CN
Inventors: 班必俊
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2006-06-28
Filing date: 2006-06-28
Publication date: 2008-01-02
Anticipated expiration: 2026-06-28
Also published as: CN100473743C

Abstract

The invention relates to a high-intensity hot-dip galvanized steel with good weld ability for stamping and the manufacturing method, which solves the technique problem of the prior high-intensity hot-dip galvanized steel without the high intensity, the good stamping and the good weld ability. The high-intensity hot-dip galvanized steel comprises the following parts: 0.005%-0.015%C, <=0.2% Si, 0.5%-1.5% Mn, <=0.015% P, 0.01%-0.10% Al, 0.03%-0.10%Ti, 0.005%-0.02%Nb, the rest Fe and unavoidable impurity. The method comprises the following steps: preconditioning iron melt; smelting by changing the furnace; refining; hot-rolling; cleaning with the acid; rolling coldly; annealing; getting the product coil ( the heating temperature is less than 1270Deg. C, the final rolling temperature is more than 860Deg. C, the welding temperature is from 580Deg. C to 680Deg. C, the annealing temperature is from 750Deg. C to 850Deg. C, the other proceeds according to the conventional technique). The invention is used for the parts of the cars.

Description

The stamping high-strength hot-galvanized steel and the manufacture method thereof of excellent weldability

Technical field: the present invention relates to a kind of hot-galvanized steel and manufacture method thereof, particularly a kind ofly be used to make automobile with excellent weldability, good high-strength hot-dip zinc-coated steel and the manufacture method thereof of stampability.

Background technology:

Along with developing of automobile industry, people are to the raising of automobile environment-protection consciousness, have lightness and security, processibility requires the material development very fast, such material had both required certain intensity, require deep drawability good simultaneously, deep-draw high-strength steel in the past mainly is to add Si on the IF steel matrix, Mn, elements such as P improve intensity can reach 390Mpa, the 440Mpa level, but owing to a large amount of add alloys to have brought for coating surface quality and deep drawability unfavorable, also unfavorable to welding simultaneously, heavy addition Mn in the past particularly, high-strength IF steel about the 440Mpa of chemical ingredientss such as P is difficult to satisfy the user of welding requirements strictness.The high-strength hot-dip zinc-coated steel of external manufacturer production its composition weight percent by analysis is C:0.002%, Si:0.05%, Mn:1.8%, P:0.095%, S:0.007%, Al:0.047%, Ti:0.026%, Nb:0.02%, all the other are iron and unavoidable impurities.This high-strength galvanizing production mainly adopts high Mn (greater than 1.5%), high P (greater than 0.06%) solution strengthening, and this sample ingredient is the cost height not only, and processing characteristics, weldability, surface quality etc. are all relatively poor by contrast.And its carbon adopts Ultra-low carbon, the also corresponding increase of feasible smelting difficulty.

Summary of the invention: the purpose of this invention is to provide a kind of be used to make automobile excellent weldability, good high-strength hot-dip zinc-coated steel and the manufacture method thereof of stampability.Solve mainly that existing high-strength hot-dip zinc-coated steel can't guarantee to have high strength simultaneously, the technical problem of good deep drawing quality, good weldability.The weight percent of its chemical element moiety of high-strength hot-dip zinc-coated steel is:

C：≤0.005％~0.015％

Si：≤0.2％

Mn：0.5％~1.5％

P：0.02％~0.07％

S：≤0.015％

Al：0.01％~0.10％

Ti：0.03％~0.10％

Nb：0.005％~0.02％

All the other are iron and unavoidable impurities.

Automobile high-strength hot-galvanized steel manufacture method, is processed into the finished product volume through pot galvanize at, hot rolling concise behind hot metal pretreatment, converter smelting, stove by the said ratio material, pickling, cold rolling, annealing.Controlling hot rolling wherein: Heating temperature≤1270 ℃, finishing temperature: 〉=860 ℃, coiling temperature 〉=580 ℃～680 ℃; Annealing temperature: 750 ℃～850 ℃; Other routinely technology carry out.The performance that obtains product is: tensile strength: 390Mpa ~ 490Mpa, r 〉=1.4.

Composition design of the present invention and controlling of production process principle are: because the automobile high-strength hot-galvanized steel not only needs certain intensity, and characteristics such as stampability, superior weldability, secondary processing embrittlement temperature that need be good be low, great surface quality, according to this characteristic and requirement, key design one cover chemical ingredients, hot rolling, cold rolling, annealed technology are to reach certain material pressworkability and good surface quality, abide by (1) formula in order to ensure the design of excellent weldability material composition simultaneously and carry out, carbon equivalent (Pcm) should be less than 0.24%.

Pcm＝C+Si/30+Mn/20+2P+4S (1)

Therefore steel grades control principle of the present invention is as follows:

Carbon: add C at steel grade and can improve intensity, but the increase of the C of solid solution can make the r value descend significantly, so technology should reduce carbon content in the steel for high-strength IF steel in the past as far as possible.Thereby the present invention replaces alloy to add raising weldability, favourable surface imperfection minimizing etc. to add trace carbon.But too high stampability of carbon and weldability variation, so carbon can not be too high.The present invention's corresponding raisings Ti alloy content when increasing along with carbon in addition, if carbon content is too high, corresponding Ti alloy adds too much, and is also unfavorable to material property, cost.Therefore carbon is controlled at 0.005 ~ 0.015%.

Manganese: Mn is bigger to the tension intensity effect, along with the raising intensity increase of Mn.Mn and C coexistence form the C-Mn dipole check thereby the generation of 111} texture nuclear hinders growing up of crystal grain, and Mn separates out to react with oxygen on steel plate and generates MnO, that is: Mn+H ₂O=MnO+H ₂, manganese oxide generates thick more also big more to galvanized influence, the bonderizing variation, and the Mn addition is how unfavorable to weldability simultaneously, and Mn adds many more r values low more (situation that particularly has C).For this reason in the adding that guarantees to reduce under the intensity prerequisite Mn as far as possible.

Phosphorus: P is cheap strengthening element, and P is little to r value influence, to r value influence degree less than Mn, and bigger to intensity effect since IF steel crystal boundary a little less than, add P segregation on crystal boundary, precipitate is FePTi, so it is unfavorable and bring secondary embrittlement problem to unit elongation too much to add affiliation.P interpolation simultaneously is too much unfavorable to welding and alloying efficient.

Silicon: Si is a strengthening element, and Si high strength more is high more, but the high more r value of Si is low more, and moreover and can separate out at surface of steel plate and produce oxide film and influence surface treatment, and Si generates SiO at surface of steel plate _x, SiO _xThe increase of growing amount reduces the moistening adhesive tension of steel plate and liquid zinc.Si interpolation simultaneously is too much unfavorable to weldability, makes Si content few as far as possible so the present invention controls the Si alloy.Silicon is smaller or equal to 0.2%.

Sulphur: S is bigger to weldability influence, so that S will try one's best is low.General S is controlled at below 0.015%.

Titanium: Ti adds as the alloy of fixation of C, N element, and Ti＞3.4 * N+1.5 * S+4 * C just can accomplish to eliminate interstitial atom, and it is favourable to processing characteristics to remain some Ti, but Ti can not be too high, otherwise unfavorable to hot-dip galvanized alloyization, bonderizing etc.

Cross and take advantage of Ti ^*: Ti ^*(4 * C+3.4 * N+1.5 * S)＞0 (2) for=Ti-

Calculate the Ti controlled contents according to (2) formula.

Niobium: material of the present invention adopts the compound addition manner of Nb-Ti, and purpose reduces DBTT, and Nb-Ti compound IF steel has lower DBTT than conventional Ti-IF steel.Simultaneously because residual solid solution carbon on the Nb-Ti-IF steel crystal boundary, stoped to resemble the Ti-IF iron from the rapid diffusion of crystal boundary, thereby than the control of Ti-IF steel alloying easily, but recrystallization temperature improves the material property deterioration along with Nb increases simultaneously.Therefore Nb generally is controlled at 0.005% ~ 0.02%.

Steel grade of the present invention is made slab through continuous casting, then carries out hot rolling.Hot rolling, cold-rolling process control principle are as follows:

(1) finishing temperature:

Rolling and cause organizing the generation of mixed crystal in order not make material enter two-phase region, finishing temperature requires more than Ar3, 〉=860 ℃;

(2) coiling temperature:

Low solid solution Nb of coiling temperature and tiny NbC and AL, N influence recrystallization temperature, be that solid solution Nb spread coefficient is little, thereby the mobile difficulty of recrystallization nucleus, the tiny precipitate that distributes of disperse simultaneously suppresses moving of crystal boundary, improving coiling temperature can make precipitate separate out and grow up, recrystallization temperature is reduced, thereby intensity reduce, unit elongation improves.But coiling temperature is too high, and is bigger to the product intensity influence.General coiling temperature is controlled at 580 ℃ ~ 680 ℃.

(3) annealing temperature:

Along with annealing temperature reduces tensile strength raising, n value, the reduction of r value.In order to prevent that the zinc layer from not plating and reduce not galvanized size, preferably annealing temperature is too not low, at high density H ₂Oxide compound along with annealing temperature raising Mn under the condition is reduced into metal M n, generally easily is reduced to MnO more than 750 ℃, thereby reduces not zinc-plated.So it is 750 ℃～850 ℃ that the present invention controls annealing temperature.

The invention has the beneficial effects as follows: the present invention is by controlling a certain amount of carbon content, add a certain amount of Ti and Nb simultaneously, because TiC, NbC disperse distribute and make grain refining and dispersion-strengthened obtain the high-strength hot-dip zinc-coated steel greater than 390Mpa, significantly reduce the interpolation of Mn, P, thereby avoided the influence of the interpolation of high Mn, P the material weldability.Stamping high-strength hot-galvanized steel of the present invention has characteristics such as good weldability, good stampability, anti-secondary workability, great surface quality.The present invention add alloy phase to less, produce easily, steady quality, be fit to all kinds of producers suitability for industrialized production.

Description of drawings:

Accompanying drawing is tensile strength 440Mpa level steel of the present invention and comparative steel Pcm contrast.

Embodiment: three embodiment of the present invention and a comparative example see the following form 1:

Project	C	Si	Mn	P	S	Al	Ti	Nb	Pcm	Unit elongation	Tensile strength	r
	C	Si	Mn	P	S	Al	Ti	Nb	Pcm	Unit elongation	Tensile strength	r	％	％	％	％	％	％	％	％	％	％	Mpa
	The present invention	0.005 ～ 0.015	≤0.2	0.5 ～ 1.5	0.02~ 0.07	≤ 0.015	0.01 ～ 0.10	0 03 ～ 0.10	0.005~ 0.02	≤ 0.24			％	％	％	％	％	％	％	％	％	％	Mpa
Embodiment A	The present invention	0.005 ～ 0.015	≤0.2	0.5 ～ 1.5	0.02~ 0.07	≤ 0.015	0.01 ～ 0.10	0 03 ～ 0.10	0.005~ 0.02	≤ 0.24			0.012	0.12	0.8	0.060	0.008	0.056	0.065	0.010	0.21	36	462	1.65
Embodiment A	Embodiment B	0.008	0.18	1.1	0.062	0.005	0.041	0.061	0.015	0.21	37	451	0.012	0.12	0.8	0.060	0.008	0.056	0.065	0.010	0.21	36	462	1.65	1.57
Embodiment C	Embodiment B	0.008	0.18	1.1	0.062	0.005	0.041	0.061	0.015	0.21	37	451	0.008	0.08	0.7	0.060	0.004	0.053	0.067	0.020	0.18	39	397	1.78	1.57
Embodiment C	Comparative steel	0.002	0.05	1.8	0.095	0 007	0.047	0.026	0.020	0.31	35	448	0.008	0.08	0.7	0.060	0.004	0.053	0.067	0.020	0.18	39	397	1.78	1.35

The technology controlling and process of embodiment A is: controlling hot rolling: Heating temperature :≤1270 ℃, and finishing temperature: 860 ℃, coiling temperature: 600 ℃; 770 ℃ of annealing temperatures.

The technology controlling and process of Embodiment B is: controlling hot rolling: Heating temperature :≤1270 ℃, and finishing temperature: 930 ℃, coiling temperature: 650 ℃; 820 ℃ of annealing temperatures.

The technology controlling and process of Embodiment C is: controlling hot rolling: Heating temperature :≤1270 ℃, and finishing temperature: 890 ℃, coiling temperature: 680 ℃; 840 ℃ of annealing temperatures.

Hardness in the table 1 and tensile property adopt general GB standard testing.Steel of the present invention and comparative steel Pcm contrast are with reference to accompanying drawing.

Claims

1, a kind of stamping high-strength hot-galvanized steel of excellent weldability, the weight percent of its chemical element moiety is:

C：≤0.005％~0.015％

Si：≤0.2％

Mn：0.5％~1.5％

P：0.02％~0.07％

S：≤0.015％

Al：0.01％~0.10％

Ti：0.03％~0.10％

Nb：0.005％~0.02％

All the other are iron and inevitably are mingled with.

2, the stamping high-strength hot-galvanized steel of excellent weldability according to claim 1 is characterized in that, carbon equivalent Pcm is less than 0.24%, Pcm=C+Si/30+Mn/20+2P+4S.

3, the manufacture method of the stamping high-strength hot-galvanized steel of the described excellent weldability of claim 1, may further comprise the steps: hot metal pretreatment, converter smelting, furnace rear refining, hot rolling, pickling, cold rolling, annealing, pot galvanize, be processed into finished product volume, it is characterized in that: hot rolling Heating temperature≤1270 ℃, finishing temperature is controlled at 〉=and 860 ℃, 580 ℃～680 ℃ of coiling temperatures, annealing temperature are controlled at 750 ℃～850 ℃.