Hot rolling method for 600MPa-grade high-strength steel 1.5 mm plate

Abstract

The invention discloses a hot rolling method of a 600MPa-grade high-strength steel 1.5 mm plate, which comprises the following steps: heating a casting blank at the temperature of 1250-1300 DEG C; the rough rolling inlet temperature ranges from 1140 DEG C to 1200 DEG C, the rough rolling outlet temperature ranges from 1030 DEG C to 1070 DEG C, and the rough rolling outlet speed ranges from 3 m / s to 5 m / s; the finish rolling inlet temperature is 1020-1070 DEG C, the finish rolling outlet temperature is 860-900 DEG C, and the finish rolling outlet speed is 6.85-8.37 m / s; the gradient of the roll gaps of the F1-F7 finishing rolls is designed to be 11.19 mm, 4.97 mm, 3.82 mm, 2.57 mm, 1.96 mm, 1.66 mm and 1.5 mm. A traditional cold rolling process is replaced with a hot rolling process, and the plate with uniform mechanical property and surface quality is obtained by optimizing temperature control, rolling speed and gradient design of a finish roll gap in hot rolling, so that the ductility and formability of the high-strength steel are improved.

Description

Technical Field

[0001] The invention belongs to the field of hot-rolled steel production, relates to a hot rolling process for high-strength steel plates, and specifically relates to a hot rolling method for a 600MPa-grade high-strength steel 1.5mm plate. Background Art

[0002] With the increasing demand for high-strength steel in modern industry, especially in automobiles, bridges, ships and other structural applications, 600MPa grade high-strength steel has become an indispensable key material in many engineering designs. In order to meet multiple performance requirements such as lightweight, high strength and corrosion resistance, thin-gauge high-strength steel occupies an important position in product design. However, the process of producing such high-strength, thin-gauge steel plates has always faced many challenges.

[0003] The production of thin-gauge high-strength steel mainly relies on the traditional cold rolling process. During the cold rolling process, the steel is cold-worked to increase its hardness and strength, but this also leads to a decrease in its ductility, limiting its application in subsequent processing such as deep drawing. In addition, the cold rolling process is prone to surface defects and microcracks, and consumes a lot of energy, further increasing production costs. In contrast, the hot rolling process, by rolling at a higher temperature, can not only effectively avoid the surface defects generated during the cold rolling process, but also maintain the good plasticity and ductility of the steel, thereby improving the operability of subsequent processing. Moreover, compared with the cold rolling process, the hot rolling process significantly reduces energy consumption and production costs.

[0004] For the production of 600MPa grade high-strength steel, especially 600MPa grade high-strength steel plates with a thickness of 1.5mm, hot rolling is used instead of cold rolling, which can not only obtain more uniform plate quality, but also significantly improve the ductility and formability of high-strength steel. In addition, by optimizing key parameters such as temperature control, rolling speed and deformation during hot rolling, production efficiency can be effectively improved, energy consumption can be reduced, and production costs can be reduced. However, the current conventional hot rolling process is generally suitable for the production of thin high-strength steel with a thickness of 2.0mm to 10mm. It is more difficult to roll thinner steel plates, with low production efficiency and low yield rate.

[0005] The invention patent with publication number CN116065095A discloses a 500-800Mpa grade one-steel multi-grade cold-rolled low-alloy high-strength steel and its production method. It adopts the hot rolling + cold rolling method for production, and its cost is bound to be too high. In addition, it mainly discusses the influence of chemical composition on the strength of high-strength steel, and relatively little research on the rolling part.

[0006] The invention patent with the publication number CN117583387A discloses a preparation method of a 1.5mm hot-rolled high-strength weather-resistant photovoltaic support steel, which details various parameters during the rolling process. However, the roll gap of F4 - F7 in the finish rolling stage is designed with a fixed value of 2mm, which is bound to lead to a decrease in accuracy for rolling 1.5mm thick weather-resistant steel. Summary of the Invention

[0007] To solve the above technical problems existing in the prior art, the present invention provides a hot-rolling method for 1.5mm thick plates of 600MPa grade high-strength steel, including the following processes: hot metal desulfurization, converter smelting, argon blowing in the argon station, calcium treatment in the LF ladle furnace, continuous casting, slab slow cooling, slab heating, hot-rolling roughing, hot-rolling finishing, strip laminar cooling and coiling. Among them, the hot-rolling method for 1.5mm thick plates of 600MPa grade high-strength steel includes:

[0008] The thickness of the slab obtained through the continuous casting process is controlled to be 210mm. In the slab heating process, the slab heating temperature is controlled at 1250 - 1300°C, and the residence time in the furnace is controlled at 170 - 200min;

[0009] In the hot-rolling roughing process, the roughing entry temperature is controlled at 1140 - 1200°C, the roughing exit temperature is controlled at 1030 - 1070°C, the roughing exit speed is controlled at 3 - 5m / s, and hot-rolling roughing is carried out in 5 passes to obtain an intermediate slab with a thickness of 25 - 30mm;

[0010] In the hot-rolling finishing process, the finishing entry temperature is controlled at 1020 - 1070°C, the finishing exit temperature is controlled at 860 - 900°C, the finishing exit speed is controlled at 6.85 - 8.37m / s, and hot-rolling finishing is carried out in 7 passes to obtain a strip with a thickness of 1.5mm;

[0011] In the hot-rolling finishing process, the finishing mill unit includes a total of 7 groups of finishing rolls from F1 to F7, and the roll gap, roll speed, and roll diameter of the finishing rolls are controlled as follows:

[0012] Roll gap of the finishing rolls: F1: 11.19mm, F2: 4.97mm, F3: 3.82mm, F4: 2.57mm, F5: 1.96mm, F6: 1.66mm, F7: 1.5mm;

[0013] Roll speed of the finishing rolls: F1: 0.77 - 0.93m / s, F2: 1.44 - 1.76m / s, F3: 2.57 - 3.14m / s, F4: 3.87 - 4.73m / s, F5: 5.18 - 6.33m / s, F6: 6.20 - 7.58m / s, F7: 6.85 - 8.37m / s;

[0014] Finish rolling roll diameter: F1: 793 mm, F2: 776 mm, F3: 745 mm, F4: 726 mm, F5: 558 mm, F6: 578 mm, F7: 583 mm.

[0015] Further, in the hot rolling method of the 1.5 mm sheet of the 600 MPa grade high-strength steel, in the strip laminar cooling process, the strip after finish rolling is subjected to laminar cooling, and the laminar cooling rate is controlled at 20 - 30 °C / s.

[0016] Further, in the hot rolling method of the 1.5 mm sheet of the 600 MPa grade high-strength steel, in the coiling process, the coiling temperature is controlled at 585 - 635 °C.

[0017] Further, in the hot rolling method of the 1.5 mm sheet of the 600 MPa grade high-strength steel, the intermediate billet obtained by hot rough rolling is sent to the finish rolling group for hot finish rolling after passing through the heat preservation cover and the hot coil box.

[0018] Further, in the hot rolling method of the 1.5 mm sheet of the 600 MPa grade high-strength steel, the hot rolled coil obtained by coiling is lifted into the slow cooling box and slowly cooled to room temperature.

[0019] Further, the chemical composition of the steel used in the hot rolling method of the 1.5 mm sheet of the 600 MPa grade high-strength steel is controlled by mass percentage as follows: C: 0.05 - 0.07%, Si: 0.30 - 0.40%, Mn: 0.95 - 1.15%, P ≤ 0.025%, S ≤ 0.005%, Cr: 0.60 - 0.70%, Ni: 0.15 - 0.25%, Cu: 0.25 - 0.35%, Nb: 0.035 - 0.045%, Ti: 0.08 - 0.09%, and the rest is Fe and unavoidable impurity elements.

[0020] The hot rolling method of the 1.5 mm sheet of the 600 MPa grade high-strength steel of the present invention has the following advantages and beneficial effects:

[0021] By replacing the traditional cold rolling process with the hot rolling process, optimizing the key parameters such as temperature control and rolling speed during hot rolling, and adopting a gradient design for the finish rolling roll gap, the present invention can not only obtain sheets with uniform mechanical properties and surface quality, effectively ensure the dimensional accuracy of the sheets, but also significantly improve the ductility and formability of high-strength steel, realize the efficient production of high-strength steel thin sheets, reduce energy consumption, reduce production costs, and is suitable for the industrial production of high-strength steel thin sheets. Specific embodiments

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in combination with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0023] The present invention aims to replace the traditional cold rolling process by optimizing the hot rolling process to achieve the efficient production of high-strength steel thin plates. For this purpose, a hot rolling method for 1.5-mm-thick plates of 600 MPa grade high-strength steel is provided. By adopting a gradient design for the roll gap of the finishing rolls to adapt to the mechanical requirements and plate deformation conditions in different stages, and by reasonably controlling the rolling parameters, the mechanical properties and surface quality of 1.5-mm-thick plates of 600 MPa grade high-strength steel are optimized, energy consumption is reduced, and production efficiency is improved.

[0024] The hot rolling method for 1.5-mm-thick plates of 600 MPa grade high-strength steel of the present invention includes the following processes: hot metal desulfurization, converter smelting, argon blowing in the argon station, calcium treatment in the LF ladle furnace, continuous casting, slab slow cooling, slab heating, hot rolling roughing, hot rolling finishing, strip laminar cooling, and coiling. It mainly involves the control of rolling parameters and the optimization of the roll gap of the finishing rolls, specifically including:

[0025] The thickness of the slab obtained through the continuous casting process is controlled to be 210 mm. In the slab heating process, the slab heating temperature is controlled to be 1250 - 1300 °C, and the residence time in the furnace is controlled to be 170 - 200 min;

[0026] In the hot rolling roughing process, the roughing entry temperature is controlled to be 1140 - 1200 °C, the roughing exit temperature is controlled to be 1030 - 1070 °C, the roughing exit speed is controlled to be 3 - 5 m / s, and hot rolling roughing is carried out in 5 passes to obtain an intermediate slab with a thickness of 25 - 30 mm;

[0027] In the hot rolling finishing process, the finishing entry temperature is controlled to be 1020 - 1070 °C, the finishing exit temperature is controlled to be 860 - 900 °C, the finishing exit speed is controlled to be 6.85 - 8.37 m / s, and hot rolling finishing is carried out in 7 passes to obtain a 1.5-mm-thick strip;

[0028] In the hot rolling finishing process, the finishing mill unit includes a total of 7 groups of finishing rolls from F1 to F7, and the roll gap, roll speed, and roll diameter of the finishing rolls are controlled as follows:

[0029] Finishing roll gap: F1: 11.19 mm, F2: 4.97 mm, F3: 3.82 mm, F4: 2.57 mm, F5: 1.96 mm, F6: 1.66 mm, F7: 1.5 mm;

[0030] Speeds of finishing rolls: F1: 0.77 - 0.93 m / s, F2: 1.44 - 1.76 m / s, F3: 2.57 - 3.14 m / s, F4: 3.87 - 4.73 m / s, F5: 5.18 - 6.33 m / s, F6: 6.20 - 7.58 m / s, F7: 6.85 - 8.37 m / s;

[0031] Diameters of finishing rolls: F1: 793 mm, F2: 776 mm, F3: 745 mm, F4: 726 mm, F5: 558 mm, F6: 578 mm, F7: 583 mm.

[0032] Furthermore, in the laminar cooling process of the steel strip, the steel strip after finishing rolling is subjected to laminar cooling, and the laminar cooling rate is controlled at 20 - 30 °C / s.

[0033] Furthermore, in the coiling process, the coiling temperature is controlled at 585 - 635 °C, and finally a hot-rolled coil with a thickness of 1.5 mm is obtained.

[0034] Furthermore, in the hot rolling method of 1.5 mm thick 600 MPa grade high-strength steel sheet of the present invention, the intermediate billet obtained by hot rough rolling is sent to the finishing group for hot rolling finishing after passing through the heat preservation cover and the hot coil box.

[0035] Furthermore, in the hot rolling method of 1.5 mm thick 600 MPa grade high-strength steel sheet of the present invention, the hot-rolled coil obtained by coiling is lifted into the slow cooling box and slowly cooled to room temperature.

[0036] As a specific embodiment, the chemical composition of the steel used in the hot rolling method of 1.5 mm thick 600 MPa grade high-strength steel sheet of the present invention is controlled by mass percentage as follows: C: 0.05 - 0.07%, Si: 0.30 - 0.40%, Mn: 0.95 - 1.15%, P ≤ 0.025%, S ≤ 0.005%, Cr: 0.60 - 0.70%, Ni: 0.15 - 0.25%, Cu: 0.25 - 0.35%, Nb: 0.035 - 0.045%, Ti: 0.08 - 0.09%, and the rest is Fe and inevitable impurity elements.

[0037] The following further illustrates the hot rolling method of 1.5 mm thick 600 MPa grade high-strength steel sheet of the present invention in combination with Examples 1 - 3.

[0038] Example 1

[0039] The specific implementation process of the hot rolling method of 1.5 mm thick 600 MPa grade high-strength steel sheet in Example 1 includes:

[0040] A slab with a thickness of 210 mm is prepared by the process flow of hot metal desulfurization - converter smelting - argon blowing in the argon station, calcium treatment in the LF ladle furnace - continuous casting, and slab slow cooling. The chemical composition of the slab is by mass percentage: 0.07% C, 0.36% Si, 1.03% Mn, 0.014% P, 0.005% S, 0.34% Cu, 0.657% Cr, 0.078% Ti, 0.0075% N, and the rest is Fe and inevitable impurities.

[0041] The slab is sent to a heating furnace for heating. The heating temperature is 1270 - 1280 °C, and the residence time in the furnace is 180 - 192 min. After heating, the slab is sent to a rough rolling mill for rough rolling. The rough rolling inlet temperature is 1150 - 1163 °C, the rough rolling outlet temperature is 1045 - 1052 °C, and the rough rolling outlet speed is 4.0 m / s. After 5 passes of rough rolling, an intermediate slab with a thickness of 30 mm is obtained.

[0042] The intermediate slab passes through a heat preservation cover and a hot coil box and is sent to a finishing mill for finishing rolling. The finishing rolling inlet temperature is 1040 - 1050 °C, the finishing rolling outlet temperature is 871 - 882 °C, and the finishing rolling outlet speed is 8.0 m / s. After 7 passes of finishing rolling, a steel strip with a thickness of 1.5 mm is obtained. In the hot rolling finishing process, the roll gaps, roll speeds, and roll diameters of a total of 7 groups of finishing rolls from F1 to F7 are set as:

[0043] F1 F2 F3 F4 F5 F6 F7 Roll gap / mm 11.19 4.97 3.82 2.57 1.96 1.66 1.5 Roll speed / m / s 0.89 1.68 3.0 4.52 6.0 7.23 8.0 Roll diameter / mm 793 776 745 726 558 578 583

[0044] The steel strip after finishing rolling is subjected to laminar cooling. The laminar cooling speed is 20 °C / s, and then the steel strip is coiled into a hot rolled coil with a thickness specification of 1.5 mm at a coiling temperature of 610 - 625 °C and is lifted into a slow cooling box to be slowly cooled to room temperature.

[0045] The thickness of the sheet produced by the hot rolling method of the 600 MPa grade high-strength steel 1.5 mm sheet in Example 1 of the present invention is 1.5 mm. After actual testing, the yield strength of the sheet is 682 MPa, and the elongation is 25%.

[0046] Example 2

[0047] The specific implementation process of the hot rolling method of the 600 MPa grade high-strength steel 1.5 mm sheet in Example 2 includes:

[0048] A slab with a thickness of 210 mm is prepared by the process flow of hot metal desulfurization - converter smelting - argon blowing in the argon station, calcium treatment in the LF ladle furnace - continuous casting, and slab slow cooling. The chemical composition of the slab is by mass percentage: 0.07% C, 0.38% Si, 1.12% Mn, 0.014% P, 0.005% S, 0.317% Cu, 0.675% Cr, 0.082% Ti, 0.0076% N, and the rest is Fe and inevitable impurities.

[0049] The billet is fed into a heating furnace for heating. The heating temperature is 1280 - 1292 °C, and the residence time in the furnace is 180 - 193 min. After heating, the billet is fed into a roughing mill for roughing. The roughing inlet temperature is 1140 - 1153 °C, the roughing outlet temperature is 1035 - 1045 °C, and the roughing outlet speed is 4.5 m / s. After 5 passes of roughing, an intermediate billet with a thickness of 28 mm is obtained.

[0050] The intermediate billet passes through a heat-insulating hood and a hot coil box and is then fed into a finishing mill for finishing. The finishing inlet temperature is 1030 - 1041 °C, the finishing outlet temperature is 863 - 875 °C, and the finishing outlet speed is 7.8 m / s. After 7 passes of finishing, a steel strip with a thickness of 1.5 mm is obtained. In the hot rolling finishing process, the roll gaps, roll speeds, and roll diameters of a total of 7 groups of finishing rolls from F1 to F7 are set as follows:

[0051] F1 F2 F3 F4 F5 F6 F7 Roll gap / mm 11.19 4.97 3.82 2.57 1.96 1.66 1.5 Roll speed / m / s 0.87 1.64 2.93 4.4 5.89 7.06 7.8 Roll diameter / mm 793 776 745 726 558 578 583

[0052] The steel strip after finishing is subjected to laminar flow cooling with a cooling rate of 20 °C / s, and then the steel strip is coiled into a hot-rolled coil with a thickness specification of 1.5 mm at a coiling temperature of 615 - 631 °C, and is lifted into a slow-cooling box and slowly cooled to room temperature.

[0053] The plate produced by the hot rolling method of the 600 MPa grade high-strength steel 1.5 mm plate in Example 2 of the present invention has a thickness of 1.5 mm. After actual testing, the yield strength of the plate is 690 MPa, and the elongation is 23.5%.

[0054] Example 3

[0055] The specific implementation process of the hot rolling method of the 600 MPa grade high-strength steel 1.5 mm plate in Example 3 includes:

[0056] A billet with a thickness of 210 mm is prepared by using the technological process of hot metal desulfurization - converter smelting - argon blowing in an argon station, calcium treatment in an LF ladle furnace - continuous casting, and billet slow cooling. The chemical composition of the billet by mass percentage is: 0.07% C, 0.36% Si, 1.03% Mn, 0.014% P, 0.005% S, 0.342% Cu, 0.647% Cr, 0.078% Ti, 0.0075% N, and the rest is Fe and inevitable impurities.

[0057] The billet is fed into a heating furnace for heating. The heating temperature is 1285 - 1295 °C, and the residence time in the furnace is 180 - 192 min. After heating, the billet is fed into a roughing mill for roughing. The roughing inlet temperature is 1143 - 1154 °C, the roughing outlet temperature is 1030 - 1043 °C, and the roughing outlet speed is 4.0 m / s. After 5 passes of roughing, an intermediate billet with a thickness of 26 mm is obtained.

[0058] The intermediate billet is fed into the finishing mill through a soaking hood and a hot coil box for finishing rolling. The finishing rolling inlet temperature is 1022 - 1032 °C, the finishing rolling outlet temperature is 882 - 893 °C, and the finishing rolling outlet speed is 7.1 m / s. After 7 passes of finishing rolling, a steel strip with a thickness of 1.5 mm is obtained. In the hot rolling finishing process, the roll gaps, roll speeds, and roll diameters of a total of 7 groups of finishing rolls from F1 to F7 are set as follows:

[0059] F1 F2 F3 F4 F5 F6 F7 Roll gap / mm 11.19 4.97 3.82 2.57 1.96 1.66 1.5 Roll speed / m / s 0.79 1.49 2.66 4.0 5.37 6.43 7.1 Roll diameter / mm 793 776 745 726 558 578 583

[0060] The steel strip after finishing rolling is subjected to laminar cooling with a laminar cooling rate of 20 °C / s, and then the steel strip is coiled into a hot rolled coil with a thickness specification of 1.5 mm at a coiling temperature of 585 - 595 °C, and is lifted into a slow cooling box and slowly cooled to room temperature.

[0061] The thickness of the sheet produced by using the hot rolling method for 1.5 mm sheet of 600 MPa grade high strength steel according to Embodiment 3 of the present invention is 1.5 mm. After actual detection, the yield strength of the sheet is 680 MPa and the elongation is 24%.

[0062] In summary, the present invention provides a hot rolling method for 1.5 mm sheet of 600 MPa grade high strength steel. By replacing the traditional cold rolling process with a hot rolling process, optimizing key parameters such as temperature control and rolling speed during hot rolling, and adopting a gradient design for the finishing roll gaps, not only can a sheet with uniform mechanical properties and surface quality be obtained, effectively ensuring the dimensional accuracy of the sheet, but also the ductility and formability of the high strength steel can be significantly improved, realizing the efficient production of thin sheets of high strength steel, reducing energy consumption and production costs, and being applicable to the industrial production of thin sheets of high strength steel.

[0063] It should be noted that in this article, the term "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that an article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such article or device.

[0064] It also should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the present invention.

Claims

1. A hot rolling method for 1.5 mm thick sheet of 600 MPa grade high strength steel, characterized in that It includes the following processes: hot metal desulfurization, converter smelting, argon blowing in the argon station, calcium treatment in the LF ladle furnace, continuous casting, slab slow cooling, slab heating, hot rolling roughing, hot rolling finishing, strip laminar cooling and coiling. The hot rolling method for the 1.5-mm-thick sheet of 600 MPa grade high-strength steel includes: The thickness of the slab obtained through the continuous casting process is controlled to be 210 mm. In the slab heating process, the slab heating temperature is controlled to be 1250 - 1300 °C, and the residence time in the furnace is controlled to be 170 - 200 min; In the hot rolling roughing process, the roughing entry temperature is controlled to be 1140 - 1200 °C, the roughing exit temperature is controlled to be 1030 - 1070 °C, the roughing exit speed is controlled to be 3 - 5 m / s, and the hot rolling roughing is carried out in 5 passes to obtain an intermediate slab with a thickness of 25 - 30 mm; In the hot rolling finishing process, the finishing entry temperature is controlled to be 1020 - 1070 °C, the finishing exit temperature is controlled to be 860 - 900 °C, the finishing exit speed is controlled to be 6.85 - 8.37 m / s, and the hot rolling finishing is carried out in 7 passes to obtain a strip with a thickness of 1.5 mm; In the hot rolling finishing process, the finishing mill unit includes a total of 7 groups of finishing rolls F1 - F7, and the roll gaps, roll speeds, and roll diameters of the finishing rolls are controlled as follows: Finishing roll gap: F1: 11.19 mm, F2: 4.97 mm, F3: 3.82 mm, F4: 2.57 mm, F5: 1.96 mm, F6: 1.66 mm, F7: 1.5 mm; Finishing roll speed: F1: 0.77 - 0.93 m / s, F2: 1.44 - 1.76 m / s, F3: 2.57 - 3.14 m / s, F4: 3.87 - 4.73 m / s, F5: 5.18 - 6.33 m / s, F6: 6.20 - 7.58 m / s, F7: 6.85 - 8.37 m / s; Finishing roll diameter: F1: 793 mm, F2: 776 mm, F3: 745 mm, F4: 726 mm, F5: 558 mm, F6: 578 mm, F7: 583 mm.

2. The hot rolling method for 1.5 mm sheet of 600 MPa grade high strength steel as claimed in claim 1, characterized in that, In the strip laminar cooling process, the strip after hot rolling finishing is subjected to laminar cooling, and the laminar cooling rate is controlled to be 20 - 30 °C / s.

3. The hot rolling method of a 1.5 mm sheet of 600 MPa grade high-strength steel as described in claim 1, characterized in that, In the coiling process, the coiling temperature is controlled to be 585 - 635 °C.

4. The hot rolling method of 1.5mm sheet of 600MPa grade high-strength steel as described in claim 1, characterized in that, The intermediate slab obtained by hot rolling roughing is sent to the finishing mill group for hot rolling finishing after passing through the heat preservation cover and the hot coil box.

5. The hot rolling method of 1.5 mm thick sheet of 600 MPa grade high-strength steel as claimed in claim 1, characterized in that, The hot rolled coil obtained by coiling is lifted into the slow cooling box and slowly cooled to room temperature.

6. The hot rolling method for 1.5 mm thick sheet of 600 MPa grade high strength steel according to any one of claims 1 to 5, characterized in that, The chemical composition of the steel used in the hot rolling method for the 1.5-mm-thick sheet of 600 MPa grade high-strength steel is controlled by mass percentage as follows: C: 0.05 - 0.07%, Si: 0.30 - 0.40%, Mn: 0.95 - 1.15%, P ≤ 0.025%, S ≤ 0.005%, Cr: 0.60 - 0.70%, Ni: 0.15 - 0.25%, Cu: 0.25 - 0.35%, Nb: 0.035 - 0.045%, Ti: 0.08 - 0.09%, and the rest is Fe and inevitable impurity elements.