CN102719740A - Method for producing ultra-low carbon high-strength cold rolling sheet - Google Patents

Abstract

The invention provides a method for producing an ultra-low carbon high-strength cold rolling sheet. Carbon content in traditional IF steel is properly increased. Alloying elements of Mn, P, Si, and the like which have a reinforcement effect on steel are added, and elements of Nb and Ti which can form second phase precipitation particles are also added to ensure that the second phase in the steel can be precipitated in a reasonable particle size. Hot rolling and cold rolling technological parameters are controlled. A hot rolling low-temperature coiling technology is used to avoid the formation of FePTid, and further to prevent the destruction effect of the FePTid on steel sheet stamping performance and a steel sheet elongation percentage. By adjusting the cold rolling technology, the steel sheet can have a relatively high [111] texture, and therefore can acquire high tensile strength, a high elongation percentage, and a high r value, to guarantee steel mouldability and shock resistance. A test detection on the steel sheet after the cold rolling shows that the average yield strength of the steel sheet reaches 287 MPa, the tensile strength is 460 MPa, the elongation percentage is 36%, the deep stamping performance index r is equal to 1.74, n is equal to 0.202, and other performance indexes also meet standard requirements.

Description

A kind of working method of Ultra-low carbon high strength cold-rolled plate

Technical field

The invention belongs to and smelt and the rolling technology field, relate in particular to a kind of working method with Ultra-low carbon high strength cold-rolled plate of excellent formability ability.

Background technology

The Hyundai Motor plate to processability and surface quality require high, thereby make third generation automobile punching press steel plate-Ultra-low carbon series product become the center of emphasis production in the world and research.So-called ultra low-carbon steel is meant the steel grade of carbon weight percent content≤0.004%.The characteristics of traditional ultra low-carbon steel not only require the carbon content in the steel extremely low, and deep drawability is good; And require to have very strong deformability, ftracture when preventing punching press; Also require to possess good plastic strain ratio (r value) and tension strain hardenability value (n value) simultaneously, to guarantee having slick surface behind the steel plate forming.

Original IF steel is a gapless atomic steel, has low-yield and low yield strength ratio, ultra preferably deep drawability and good ductility ability.But, in the past few years along with the development of world economy, the raising that vehicle safety is required; Make HS, light-duty automobile become the main flow in market, thereby the production technology of autobody sheet is had higher requirement, require autobody sheet when having good deep drawability; Have the HS shock resistance,, require it must have very favorable mechanical performance promptly as the ultra low-carbon steel of automobile structure and reinforcing member; Yield-point σ s >=250MPa; Tensile strength >=440MPa, deep drawability index r=1.3-2.2, n=0.17-0.25; And the extension performance reaches δ >=30%.

In order to improve autobody sheet each item machinery, physical performance index; The method of generally taking both at home and abroad at present is the chemical ingredients that changes steel; In the IF steel, adding P, Si or Mn strengthens steel; Make it possess the favorable mechanical performance, yet the defective of bringing is secondary processing brittleness, chemical treatment performance and the galvanized flexibility of alloying that has directly influenced steel.What the design that has was adopted is the solution of high Mn, high Ti, though above-mentioned defective is made moderate progress, shortcoming is that the anisotropy of steel is bigger, still directly has influence on the use properties of rolling the back steel plate.

Summary of the invention

The object of the invention aims to provide that a kind of plasticity is good, intensity is high, anisotropy is little, has the working method of the ultra-low carbon cold-rolling plate of good mechanical processing and processability.

For this reason, the solution that the present invention taked is:

A kind of working method of Ultra-low carbon high strength cold-rolled plate adopts hot metal pretreatment-converter smelting-refining furnace refining-continuous casting-hot continuous rolling-cold rolling acid to roll-production process route of continuous annealing-finishing, and its concrete production technique and controlled variable are:

1, the chemical ingredients of steel and weight percent content (wt%) are:

C

Si

Mn

P

S

Als

Ti

Nb

B

≤0.0060

≤0.50

0.50-1.05

0.05-0.10

≤0.025

≤0.06

0.02-0.08

0.01-0.08

0.0005-0.0020

2, hot rolling technology system:

Billet heating temperature: 1200-1260 ℃;

Hot rolling finishing temperature: 880-950 ℃;

Strip coiling temperature: 580-660 ℃;

3, cold-rolling process system:

Cold rolling draft: 69-87%;

Continuous annealing furnace: 800-840 ℃ of soaking temperature out, slow cooling temperature out: 630-690 ℃, fast cold temperature out 410-430 ℃, 370-400 ℃ of overaging temperature out, soaking time 90-180s;

Smooth unit elongation: 0.4%-1.0%.

Beneficial effect of the present invention is:

Because the present invention is on the basis of conventional I F steel (≤0.004%); An amount of carbon content (≤0.006) that improves in the steel; And add steel is played the alloying element such as Mn, P, Si of strengthening effect and can form Nb, the Ti element of the second phase precipitation particles, guarantee that second in the steel separate out with rational particle diameter in hot rolling with when cold rolling.Effectively control hot rolling and cold-rolling process parameter simultaneously, utilize hot rolling low temperature coiling technique to avoid the formation of FePTid, prevent its destruction steel plate punching performance and unit elongation; Through the adjustment cold-rolling process, make steel plate have higher 111} texture, thus obtain high tensile strength, unit elongation and r value, with the plasticity and the shock resistance of assurance steel.Embodiment of the present invention, through steel plate test detected result after cold rolling is proved: its average yield strength reaches 287MPa, and tensile strength is 460MPa, elongation 36%, deep drawability index r=1.74, n=0.202, other each item performance index also reach standard-required.

Embodiment

Embodiment 1:

Adopt hot metal pretreatment-converter smelting-refining furnace refining-continuous casting-hot continuous rolling-cold rolling acid to roll-production process route of continuous annealing-finishing, its concrete production technique and controlled variable are:

1, the chemical ingredients of steel and weight percent content (wt%) are:

C	Si	Mn	P	S	Als	Ti	Nb	B
									0.0058	0.40	0.50	0.06	0.020	0.05	0.08	0.045	0.0010

2, hot rolling technology system:

Billet heating temperature: 1260 ℃;

Hot rolling finishing temperature: 950 ℃;

Strip coiling temperature: 650 ℃.

3, cold-rolling process system:

Cold rolling draft: 85%;

Continuous annealing furnace: 810 ℃ of soaking temperature outs, the slow cooling temperature out: 650 ℃, 410 ℃ of fast cold temperature outs, 380 ℃ of overaging temperature outs, soaking time 180s.

Smooth unit elongation: 0.8%.Surplus is common process.

Embodiment 2:

Adopt hot metal pretreatment-converter smelting-refining furnace refining-continuous casting-hot continuous rolling-cold rolling acid to roll-production process route of continuous annealing-finishing, its concrete production technique and controlled variable are:

1, the chemical ingredients of steel and weight percent content (wt%) are:

C	Si	Mn	P	S	Als	Ti	Nb	B
									0.0050	0.45	1.0	0.08	0.018	0.06	0.05	0.075	0.0006

2, hot rolling technology system:

Billet heating temperature: 1240 ℃;

Hot rolling finishing temperature: 900 ℃;

Strip coiling temperature: 610 ℃.

3, cold-rolling process system:

Cold rolling draft: 72%;

Continuous annealing furnace: 840 ℃ of soaking temperature outs, the slow cooling temperature out: 690 ℃, 430 ℃ of fast cold temperature outs, 400 ℃ of overaging temperature outs, soaking time 90s.

Smooth unit elongation: 0.5%.Surplus is common process.

Embodiment 3:

Adopt hot metal pretreatment-converter smelting-refining furnace refining-continuous casting-hot continuous rolling-cold rolling acid to roll-production process route of continuous annealing-finishing, its concrete production technique and controlled variable are:

1, the chemical ingredients of steel and weight percent content (wt%) are:

C	Si	Mn	P	S	Als	Ti	Nb	B
									0.0055	0.50	0.75	0.09	0.022	0.04	0.03	0.035	0.0020

2, hot rolling technology system:

Billet heating temperature: 1210 ℃;

Hot rolling finishing temperature: 890 ℃;

Strip coiling temperature: 690 ℃.

3, cold-rolling process system:

Cold rolling draft: 78%;

Continuous annealing furnace: 825 ℃ of soaking temperature outs, the slow cooling temperature out: 635 ℃, 3900 ℃ of fast cold temperature outs, 370 ℃ of overaging temperature outs, soaking time 150s.

Smooth unit elongation: 1.0%.Surplus is common process.

Claims (1)

1. the working method of a Ultra-low carbon high strength cold-rolled plate is characterized in that, concrete production technique and controlled variable are:

(1), the chemical ingredients of steel and weight percent content (wt%) are:

C Si Mn P S Als Ti Nb B ≤0.0060 ≤0.50 0.50-1.05 0.05-0.10 ≤0.025 ≤0.06 0.02-0.08 0.01-0.08 0.0005-0.0020

(2), hot rolling technology system:

Billet heating temperature: 1200-1260 ℃;

Hot rolling finishing temperature: 880-950 ℃;

Strip coiling temperature: 580-660 ℃;

(3), cold-rolling process system:

Cold rolling draft: 69-87%;

Continuous annealing furnace: 800-840 ℃ of soaking temperature out, slow cooling temperature out: 630-690 ℃, fast cold temperature out 410-430 ℃, 370-400 ℃ of overaging temperature out, soaking time 90-180s;

Smooth unit elongation: 0.4%-1.0%.