CN1807669A

CN1807669A - Tensile strength 600Mpa grade dual phase steel plate and its production method

Info

Publication number: CN1807669A
Application number: CN 200610045846
Authority: CN
Inventors: 刘彦春; 刘相华; 李艳梅; 王国栋
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2006-02-17
Filing date: 2006-02-17
Publication date: 2006-07-26
Anticipated expiration: 2026-02-17
Also published as: CN100357474C

Abstract

Disclosed is a steel sheet with a tensile strength of 600 MPa grade wherein its constituents by mass percentage comprise C 0.05-0.08%, Si 0.20-0.40%, Mn 1.30-1.60%, and balancing Fe. Its tissue is a diphase of ferrite and martensite, wherein the volume fraction of the ferrite is 85-90%, the volume fraction of the martensite is 10-15%, and the manufacturing process consists of sheet bar continuous casting and rolling, fast cooling, soaking continuous casting sheet bar through tunnel furnace, controlling the tapping temperature to be 1100-1150 deg. C, controlling the initial rolling temperature between 1100-1150 deg. C, and end rolling temperature at 780-850 deg. C, fast cooling after rolling, and drawing-up after cooling.

Description

A kind of tensile strength 600MPa level dual phase sheet steel and manufacture method

Technical field

The invention belongs to technical field of steel rolling, relate to the high-strength steel manufacturing of automobile structure, be specifically related to a kind of tensile strength 600MPa level dual phase sheet steel and manufacture method.

Background technology

High-strength vehicle is one of focus of domestic and international material work sutdy with the exploitation of hot-rolled steel sheet always.General cable body+perlite hot-rolled steel sheet maximum strength of using is the 500MPa level, though micro alloying elements such as increase Nb or Ti can further improve intensity, plasticity is variation, thereby limited its application.For further improving intensity, developed dual phase steel.Two-phase high-strength steel characteristics are the about 15% hard phases that distribute on tiny ferrite matrix, and further strengthen by the solid solution atom, and the tensile strength of ferrite-bainite and dual phase ferritic-martensitic steel is between 550～650MPa.Because the restriction of plasticity, dual phase steel can't reach 800MPa level level.For the requirement of satisfied more high strength and forming property, developed the 800MPa level three-phase TRIP steel that contains residual austenite again, the residual austenite strain-induced changes martensite in deformation process, when improving intensity, improves forming property.But the way of complex alloysization is adopted in the direct hot-rolled dual-phase steel that can commercially produce at present and the TRIP steel capital, has problems such as cost height, technology difficulty are big, is unfavorable for promoting, domestic still can not scale operation.

Consider environmental problem and energy problem, it is steel (or add trace alloying element) that novel high-strength vehicle structural part will trend towards simple C-Si-Mn with the chemical ingredients of hot-rolled steel sheet; Develop controlled rolling and control cold novel process, comprehensive utilization refined crystalline strengthening and phase transformation strengthening mode improve the steel strength limit.

Summary of the invention

With the problem that hot-rolled steel sheet and production technique thereof exist, the invention provides a kind of tensile strength 600MPa level dual phase sheet steel and manufacture method at existing high-strength vehicle.

The present invention is a composition of steel based on common C-Mn, adopts suitable technology for controlled cooling, exploitation high-strength vehicle structural part hot-rolled steel sheet.This tensile strength 600MPa level ferrite and martensite dual-phase steel plate, its chemical ingredients by mass percent is: 0.05～0.08%C, 0.20～0.40%Si, 1.30～1.60%Mn, surplus is Fe.Be organized as ferrite and martensite duplex structure, wherein: the ferrite volume fraction is 85～90%, and the martensite volume fraction is 10～15%.

The present invention adopts above-mentioned chemical ingredients steel, by CSP and quick process for cooling production tensile strength 600MPa level dual phase sheet steel, specifically carries out according to the following steps:

(1) with the continuous-casting sheet billet of thickness range 60～80mm, through the continuous tunnel furnace soaking, soaking time 15～30min, the control tapping temperature is 1100～1150 ℃.

(2) be rolled 1100～1150 ℃ of control start rolling temperatures, 780～850 ℃ of finishing temperatures.

(3) cool off fast after the hot rolling, adopt laminar flow cooling technology, 25～30 ℃/s of controlled chilling speed, 100～200 ℃ of final cooling temperatures (being coiling temperature).

(4) batch 100～200 ℃ of coiling temperatures, control steel plate thickness 2.5～6mm after the cooling.

The 600MPa level dual phase sheet steel of the inventive method preparation possesses excellent mechanical property, and yield strength is 365～395MPa, and tensile strength is 615～645MPa, and the percentage of total elongation of having no progeny is 28～32%.

Description of drawings

Accompanying drawing is tensile strength 600MPa level ferrite of the present invention and martensite dual-phase steel plate typical gold phase constitution photo.Wherein: (a) for organizing photo after the nital corrosion; (b) be LEPERA reagent (1%Na ₂S ₂O ₅The aqueous solution+4% picral) organize photo after the corrosion, brilliant white is organized as martensite in the photo.

Embodiment

Chemical ingredients steel shown in the option table 1 is a raw material, and the continuous casting and rolling thin slab is of a size of 60～80mm (thick) * 1250mm (wide) * 8000mm (length).With continuous-casting sheet billet through the continuous tunnel furnace soaking, continuous tunnel furnace length 100m, rolling through the hot continuous rolling unit then, control start rolling temperature, finishing temperature, cool off fast after rolling, adopt laminar flow cooling technology, controlled chilling speed and final cooling temperature, batch then, control steel plate thickness specification is 2.5～6mm.Process for cooling such as table 2, mechanical property with organize mark such as table 3.

Table 1 embodiment surveys chemical ingredients (massfraction %, surplus is Fe)

The composition numbering	C	Mn	Si
The composition numbering	C	Mn	Si	S0	0.05	1.60	0.22
S1	0.06	1.50	0.20	S0	0.05	1.60	0.22
S1	0.06	1.50	0.20	S2	0.07	1.40	0.40
S3	0.08	1.30	0.30	S2	0.07	1.40	0.40

Table 2 embodiment surveys the process for cooling parameter

Numbering	Thickness of strand	Soaking time	Tapping temperature	Start rolling temperature	Finishing temperature	Speed of cooling	Curling temperature
	Thickness of strand	Soaking time	Tapping temperature	Start rolling temperature	Finishing temperature	Speed of cooling	Curling temperature	(mm)	(Min)	(℃)	(℃)	(℃)	(℃/s)	(℃)
	S0-1	67	15	1100	1100	825	25	(mm)	(Min)	(℃)	(℃)	(℃)	(℃/s)	(℃)	200
S0-2	S0-1	67	15	1100	1100	825	25	67	30	1150	1150	830	26	170	200
S0-2	S1-1	60	20	1150	1150	850	26	67	30	1150	1150	830	26	170	200
S1-2	S1-1	60	20	1150	1150	850	26	60	30	1100	1100	835	28	150	200
S1-2	S2-1	80	15	1100	1100	815	30	60	30	1100	1100	835	28	150	105
S2-2	S2-1	80	15	1100	1100	815	30	80	25	1150	1150	800	30	100	105
S2-2	S3-1	67	30	1120	1120	780	28	80	25	1150	1150	800	30	100	100
S3-2	S3-1	67	30	1120	1120	780	28	67	30	1130	1130	820	26	120	100

Table 3 embodiment mechanical property and tissue volume mark

Numbering	Steel plate thickness	R _e	R _m	A ₅₀	Volume fraction
					Volume fraction		The cable body	Martensite
					(mm)	(MPa)	The cable body	Martensite	(MPa)	(％)	(％)	(％)
	S0-1	2.5	365	625	(mm)	(MPa)	30	90	(MPa)	(％)	(％)	(％)	10
S0-2	S0-1	2.5	365	625	2.5	365	30	90	620	32	90	10	10
S0-2	S1-1	4.0	375	615	2.5	365	28	90	620	32	90	10	10
S1-2	S1-1	4.0	375	615	4.0	375	28	90	635	28	90	10	10
S1-2	S2-1	5.0	380	645	4.0	375	30	87	635	28	90	10	13
S2-2	S2-1	5.0	380	645	5.0	385	30	87	645	30	85	15	13
S2-2	S3-1	6.0	395	640	5.0	385	32	85	645	30	85	15	15
S3-2	S3-1	6.0	395	640	6.0	390	32	85	640	32	85	15	15

Wherein: R _e-yield strength; R _m-tensile strength; A ₅₀-the percentage of total elongation of having no progeny (gauge length 50mm); The implementation data that composition is numbered the steel correspondence of S0 is S0-1, S0-2, and all the other together.

Claims

1, a kind of tensile strength 600MPa level dual phase sheet steel, its chemical ingredients by mass percent is: 0.05～0.08%C, 0.20～0.40%Si, 1.30～1.60%Mn, surplus is Fe; Be organized as ferrite and martensite duplex structure, wherein: the ferrite volume fraction is 85～90%, and the martensite volume fraction is 10～15%; Yield strength is 365～395MPa, and tensile strength is 615～645MPa, and the percentage of total elongation of having no progeny is 28～32%.

2, the manufacture method of the described tensile strength 600MPa level of claim 1 dual phase sheet steel adopts CSP and quick cooling-production technology, it is characterized in that processing step and processing parameter are:

(1) be the continuous-casting sheet billet of 60～80mm, the described chemical ingredients of claim 1 with thickness, through the continuous tunnel furnace soaking, the control tapping temperature is 1100～1150 ℃;

(2) be rolled 1100～1150 ℃ of control start rolling temperatures, 780～850 ℃ of finishing temperatures;

(3) cool off fast after the hot rolling, 25～30 ℃/s of controlled chilling speed, final cooling temperature are 100～200 ℃ of coiling temperatures;