CN107164700B - A kind of 800MPa grades of high-yield-ratio cold-rolled strip and its manufacturing method - Google Patents

Abstract

The invention discloses a 800MPa grade high yield ratio cold-rolled steel strip and a manufacturing method thereof. The chemical composition and mass percentage of the steel strip are: C: 0.05-0.08%, Si≤0.15%, Mn: 1.60-1.90 %, P≤0.020%, S≤0.008%, Als: 0.020～0.060%, Nb: 0.045～0.065%, Ti: 0.090～0.110%, Mo: 0.15～0.20%, N≤0.0050%, the rest is iron and non Impurities to avoid; manufacturing methods include continuous casting, hot rolling, acid rolling, continuous annealing, and leveling processes. The invention adopts reasonable composition design and matching hot rolling, acid rolling and continuous annealing process, the thickness of the steel strip produced is 1.0-2.0mm, yield strength ≥ 800MPa, tensile strength ≥ 850MPa, elongation A80 ≥ 8%, 180° Can't bend.

Description

A kind of 800MPa high yield ratio cold-rolled steel strip and its manufacturing method

technical field

The invention belongs to the technical field of metallurgy, and in particular relates to an 800MPa grade high yield ratio cold-rolled steel strip and a manufacturing method thereof.

Background technique

At present, it is the main development trend of steel materials for automobiles to use higher strength thin steel plates instead of thick steel plates to achieve vehicle weight reduction, energy saving and consumption reduction. Taking high-yield ratio cold-rolled low-alloy high-strength steel as an example, high-strength steel series with a yield strength of 260-500 MPa have been developed successively, but reports on higher-strength high-yield ratio cold-rolled low-alloy high-strength steel are relatively rare .

Patent CN 103866182 B discloses a low-cost manufacturing method of 700MPa grade cold-rolled high-strength steel and thin steel strip based on bell annealing treatment. The annealing method is bell annealing, which is not conducive to the control of the surface quality of the strip. Sub-cold rolling, long production process;

Patent CN 103882320 B discloses a high-strength cold-rolled steel plate with excellent stretch flangeability and spot weldability and its manufacturing method. The fast cooling section of the live line has high cooling speed requirements and strict process control;

Patent CN 101956139 B discloses a high-strength cold-rolled steel plate with a yield strength of 700MPa and a preparation method thereof, involving a steel plate with a yield strength ≥ 700MPa, which is obviously lower than the strength level of the steel plate disclosed in this patent.

Contents of the invention

The technical problem to be solved by the present invention is to provide a cold-rolled steel strip with a high yield strength ratio of 800 MPa; the present invention also provides a manufacturing method of a cold-rolled steel strip with a high yield strength ratio of 800 MPa.

In order to solve the above technical problems, the technical solution adopted by the present invention is: a cold-rolled steel strip with a high yield strength ratio of 800MPa, the chemical composition and mass percentage of the steel strip are: C: 0.05-0.08%, Si≤ 0.15%, Mn: 1.60～1.90%, P≤0.020%, S≤0.008%, Als: 0.020～0.060%, Nb: 0.045～0.065%, Ti: 0.090～0.110%, Mo: 0.15～0.20%, N≤ 0.0050%, the rest is iron and unavoidable impurities.

The thickness specification of the steel strip in the present invention is 1.0-2.0mm.

Mechanical properties of the steel strip in the present invention: yield strength ≥ 800MPa, tensile strength ≥ 850MPa, elongation A80 ≥ 8%, no cracking when bent at 180°.

The present invention also provides a method for manufacturing 800MPa-grade high-yield-ratio cold-rolled steel strip. The method includes continuous casting, hot continuous rolling, acid rolling, continuous annealing and leveling.

In the continuous casting process of the present invention, the thickness of the slab is 180-220mm.

In the hot continuous rolling process of the present invention, the slab heating temperature is 1250-1300°C, the furnace time is 200-240min, the finish rolling temperature is 850-890°C, and the coiling temperature is 560-600°C.

In the acid rolling process of the present invention, the reduction rate of acid rolling is ≥55%.

In the continuous annealing process of the present invention, the soaking temperature is 760-780°C, the soaking time is 90-140s, the cooling rate in the slow cooling section is 2-8°C/s, and the slow cooling end temperature is 680-720°C.

In the continuous annealing process of the present invention, the cooling rate of the rapid cooling section is 20-40°C/s, the end temperature of the rapid cooling is 380-420°C, and the temperature of the aging section is 350-390°C.

In the leveling process of the present invention, the leveling elongation is controlled at 0.5-0.8% according to the specifications.

Refer to GB/T228 and GB/T232 for the detection method of the 800MPa grade high yield ratio cold-rolled steel strip of the present invention.

The beneficial effects produced by adopting the above-mentioned technical scheme are: 1, the present invention adopts low carbon, Nb, Ti microalloying, Si, Mn solid-solution strengthening composition design idea, adds a certain amount of Mo simultaneously to promote the carbon nitrogen of Nb, Ti To play the strengthening role of chemical compounds, through reasonable composition design and matching corresponding hot rolling, acid rolling, and continuous annealing processes, a simple and easy-to-control manufacturing method of 800MPa high-yield-ratio cold-rolled steel strip is provided. The product Both high strength and good plasticity. 2. The thickness specification of the cold-rolled steel strip of the present invention is 1.0-2.0 mm, yield strength ≥ 800 MPa, tensile strength ≥ 850 MPa, elongation A80 ≥ 8%, and 180° bending without cracking.

Detailed ways

The manufacturing method of the 800MPa grade high yield ratio cold-rolled steel strip adopts the following process steps:

(1) Continuous casting process: slab thickness 180-220mm;

(2) Continuous hot rolling process: slab heating temperature 1250-1300°C, furnace time 200-240min, final rolling temperature 850-880°C, coiling temperature 560-590°C;

(3) Acid rolling process: acid rolling reduction rate ≥ 55%;

(4) Continuous annealing process: soaking temperature 760-780°C, soaking time 90-140s, slow cooling section cooling speed 2-8°C/s, slow cooling end temperature 680-720°C, fast cooling section cooling speed 20- 40°C/s, the end temperature of rapid cooling is 380-420°C, and the temperature of aging period is 350-390°C;

(5) Leveling process: Leveling elongation is controlled at 0.5-0.8% according to specifications.

The present invention will be described in further detail below in conjunction with specific embodiments.

Example 1

In this embodiment, the thickness of the 800MPa-grade high-yield ratio cold-rolled steel strip is 1.0mm, and the chemical composition and mass percentage of the steel strip are shown in Table 1.

The manufacturing method includes continuous casting, hot continuous rolling, acid rolling, continuous annealing and leveling. The specific process steps are as follows:

(1) Continuous casting process: slab thickness 195mm;

(2) Continuous hot rolling process: slab heating temperature 1250°C, furnace time 228min, final rolling temperature 865°C, coiling temperature 560°C;

(3) Acid rolling process: the reduction rate of acid rolling is 66%;

(4) Continuous annealing process: soaking temperature 765°C, soaking time 99s, slow cooling section cooling rate 6°C/s, slow cooling end temperature 695°C, fast cooling section cooling rate 36°C/s, fast cooling end temperature 405 °C, the aging temperature is 350 °C;

(5) Leveling process: the leveling elongation rate is 0.5%.

The mechanical properties of the steel strip are shown in Table 2.

Example 2

In this embodiment, the thickness of the 800MPa-grade high-yield ratio cold-rolled steel strip is 1.2mm, and the chemical composition and mass percentage of the steel strip are shown in Table 1.

The manufacturing method includes continuous casting, hot continuous rolling, acid rolling, continuous annealing and leveling. The specific process steps are as follows:

(1) Continuous casting process: slab thickness 180mm;

(2) Continuous hot rolling process: slab heating temperature 1280°C, furnace time 240min, final rolling temperature 855°C, coiling temperature 575°C;

(3) Acid rolling process: the reduction rate of acid rolling is 60%;

(4) Continuous annealing process: soaking temperature 760°C, soaking time 99s, slow cooling section cooling rate 6°C/s, slow cooling end temperature 680°C, fast cooling section cooling rate 38°C/s, fast cooling end temperature 380 °C, the aging temperature is 370 °C;

(5) Leveling process: the leveling elongation rate is 0.5%.

The mechanical properties of the steel strip are shown in Table 2.

Example 3

In this embodiment, the thickness of the 800MPa grade high yield ratio cold-rolled steel strip is 1.4mm, and the chemical composition and mass percentage of the steel strip are shown in Table 1.

The manufacturing method includes continuous casting, hot continuous rolling, acid rolling, continuous annealing and leveling. The specific process steps are as follows:

(1) Continuous casting process: slab thickness 205mm;

(2) Continuous hot rolling process: slab heating temperature 1275°C, furnace time 221min, final rolling temperature 850°C, coiling temperature 580°C;

(3) Acid rolling process: the reduction rate of acid rolling is 60%;

(4) Continuous annealing process: soaking temperature 772°C, soaking time 119s, slow cooling section cooling rate 4°C/s, slow cooling end temperature 705°C, fast cooling section cooling rate 33°C/s, fast cooling end temperature 388 °C, the aging temperature is 365 °C;

(5) Leveling process: the leveling elongation rate is 0.6%.

The mechanical properties of the steel strip are shown in Table 2.

Example 4

In this embodiment, the thickness of the 800MPa grade high yield ratio cold-rolled steel strip is 1.6 mm, and the chemical composition and mass percentage of the steel strip are shown in Table 1.

The manufacturing method includes continuous casting, hot continuous rolling, acid rolling, continuous annealing and leveling. The specific process steps are as follows:

(1) Continuous casting process: slab thickness 208mm;

(2) Continuous hot rolling process: slab heating temperature 1300°C, furnace time 205min, final rolling temperature 870°C, coiling temperature 565°C;

(3) Acid rolling process: the reduction rate of acid rolling is 55%;

(4) Continuous annealing process: soaking temperature 770°C, soaking time 90s, slow cooling section cooling rate 2°C/s, slow cooling end temperature 710°C, fast cooling section cooling rate 20°C/s, fast cooling end temperature 398 °C, the aging temperature is 385 °C;

(5) Leveling process: the leveling elongation rate is 0.6%.

The mechanical properties of the steel strip are shown in Table 2.

Example 5

In this embodiment, the thickness of the 800MPa grade high yield ratio cold-rolled steel strip is 1.8mm, and the chemical composition and mass percentage of the steel strip are shown in Table 1.

The manufacturing method includes continuous casting, hot continuous rolling, acid rolling, continuous annealing and leveling. The specific process steps are as follows:

(1) Continuous casting process: slab thickness 220mm;

(2) Continuous hot rolling process: slab heating temperature 1285°C, furnace time 216min, final rolling temperature 880°C, coiling temperature 575°C;

(3) Acid rolling process: the reduction rate of acid rolling is 55%;

(4) Continuous annealing process: soaking temperature 780°C, soaking time 140s, slow cooling section cooling rate 8°C/s, slow cooling end temperature 720°C, fast cooling section cooling rate 40°C/s, fast cooling end temperature 420 °C, the aging temperature is 390 °C; (5) Smoothing process: the smoothing elongation rate is 0.7%.

The mechanical properties of the steel strip are shown in Table 2.

Example 6

In this embodiment, the thickness of the 800MPa grade high yield ratio cold-rolled steel strip is 2.0mm, and the chemical composition and mass percentage of the steel strip are shown in Table 1.

The manufacturing method includes continuous casting, hot continuous rolling, acid rolling, continuous annealing and leveling. The specific process steps are as follows:

(1) Continuous casting process: slab thickness 212mm;

(2) Continuous hot rolling process: slab heating temperature 1280°C, furnace time 200min, final rolling temperature 875°C, coiling temperature 590°C;

(3) Acid rolling process: the reduction rate of acid rolling is 55%;

(4) Continuous annealing process: soaking temperature 771°C, soaking time 132s, slow cooling section cooling rate 5°C/s, slow cooling end temperature 685°C, fast cooling section cooling rate 26°C/s, fast cooling end temperature 410 °C, the aging temperature is 375 °C;

(5) Leveling process: the leveling elongation rate is 0.8%.

The mechanical properties of the steel strip are shown in Table 2.

Table 1 Example 1-6 steel strip chemical composition and its mass percentage (%)

Table 2 The mechanical properties of steel strips in Examples 1-6

The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced without departing from it. Any modifications or partial replacements within the spirit and scope of the present invention shall fall within the scope of the claims of the present invention.

Claims (6)

1. a kind of 800MPa grades of high-yield-ratio cold-rolled strip, which is characterized in that the steel band chemical composition composition and quality percentage Content is：C：0.05~0.08%, Si≤0.15%, Mn：1.60~1.90%, P≤0.020%, S≤0.008%, Als：0.020~ 0.060%, Nb：0.045~0.065%, Ti：0.090~0.110%, Mo：0.15~0.20%, N≤0.0050%, remaining for iron and Inevitable impurity, the thickness of strips specification are 1.0~2.0mm, the steel band mechanical property：Yield strength >= 800MPa, tensile strength >=850MPa, elongation percentage A80 >=8%, 180 ° of bendings are not cracked.

2. based on a kind of manufacturing method of 800MPa grades of high-yield-ratio cold-rolled strip described in claim 1, which is characterized in that institute The method of stating includes the smooth processes of Lian Zhu ﹑ Re Lian Zha ﹑ Suan Zha ﹑ Lian Tui ﹑, and the continuous annealing process, soaking temperature is 760~780 DEG C, Hot time 90-140s, 2-8 DEG C of slow cooling section cooling rate/s, slow cooling end temp are 680~720 DEG C, rapid cooling section 20-40 DEG C/s of cooling rate, Rapid cooling end temp is 380~420 DEG C, and aging section temperature is 350~390 DEG C.

3. a kind of manufacturing method of 800MPa grades of high-yield-ratio cold-rolled strips according to claim 2, which is characterized in that institute State continuous casting working procedure, slab thickness 180-220mm.

4. a kind of manufacturing method of 800MPa grades of high-yield-ratio cold-rolled strips according to claim 2 or 3, feature exist In the hot continuous rolling process, slab heating temperature is 1250-1300 DEG C, time inside furnace 200-240min, finishing temperature 850- 890 DEG C, 560-600 DEG C of coiling temperature.

5. a kind of manufacturing method of 800MPa grades of high-yield-ratio cold-rolled strips according to claim 4, which is characterized in that institute It states acid and rolls process, acid rolls reduction ratio >=55%.

6. a kind of manufacturing method of 800MPa grades of high-yield-ratio cold-rolled strips according to claim 5, which is characterized in that institute Smooth process is stated, smooth elongation percentage divides specifications control 0.5~0.8%.