Method for producing wide cold-rolled steel strip for economical hot forming and method for producing steel of grade CR1000 / 1500HS

Abstract

The invention discloses a manufacturing method of a cold-rolled wide steel strip for economical hot forming and a manufacturing method of steel with the mark of CR1000 / 1500HS. The steel is subjected to converter smelting, LF furnace refining and slab continuous casting to obtain a continuous casting slab, and the continuous casting slab is subjected to direct hot charging, heating, hot continuous rolling and laminar cooling to obtain a hot-rolled wide steel strip. Warehousing and slowly cooling the coiled hot-rolled wide steel strip to obtain a fine-sheet pearlite as a metallographic structure; the hot-rolled wide steel strip is subjected to acid pickling and then subjected to cold rolling under large pressure for three times of recrystallization annealing, a granular pearlitic structure is obtained, and the spheroidization rate is controlled to be 95% or above; after annealing, the cold-rolled wide steel strip is leveled, deformed and quenched, a martensite structure is obtained, the martensite grade is 4-6, the yield strength can reach 1000 MPa or above, the tensile strength can reach 1500 MPa or above, and the technical requirements of the brand CR1000 / 1500 HS are met.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material forming, and in particular to a method for manufacturing a cold-rolled wide steel strip for economical hot forming and a method for manufacturing steel with a grade of CR1000 / 1500HS. Background Art

[0002] Lightweighting of automobiles is urgent. As a new processing and manufacturing technology, hot forming can obtain martensitic structure by deformation quenching of steel strips. The tensile strength of parts can reach above 1500MPa level. It has high strength, high hardness and other product characteristics. It is widely used in the manufacture of automobile bumpers, A\B\C pillars, roof frames, underbody frames and door anti-collision bars and other parts with high collision requirements. It successfully replaces high-strength cold-formed steel strips such as TRIP steel and DP steel. However, the existing cold-rolled wide steel strips for hot forming usually need to add precious alloy elements such as Nb and V to ensure that the product has good quenching performance, which makes the production and manufacturing cost of hot forming steel strips high and cannot meet market demand.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The object of the present invention is to provide a method for manufacturing an economical cold-rolled wide steel strip for hot forming and a method for manufacturing steel of grade CR1000 / 1500HS, without adding precious alloy elements such as Nb and V, to ensure that the tensile strength of the product after quenching reaches more than 1500MPa and has good quenching performance.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a method for manufacturing an economical hot-forming cold-rolled wide steel strip, comprising:

[0007] (1) Converter smelting;

[0008] (2) LF furnace refining: after converter smelting, LF furnace refining is carried out to obtain a steel having the following chemical composition by mass percentage: C 0.22%-0.25%, Si 0.15%-0.25%, Mn 1.15%-1.30%, P≤0.018%, S≤0.005%, Cr0.15%-0.25%, Ti 0.018%-0.028%, B 0.0015%-0.0025%, Alt 0.020%-0.040%, and the remainder being Fe and unavoidable impurity elements;

[0009] (3) Slab continuous casting: after refining in an LF furnace, continuous casting is performed to obtain a continuous casting slab of 230 mm thick and 1200 mm to 1350 mm wide;

[0010] (4) heating, heating the continuous casting slab to 1235° C. to 1275° C.;

[0011] (5) hot rolling, which is to hot roll the heated continuous casting slab;

[0012] (6) laminar cooling: laminar cooling of the hot-rolled steel strip to the coiling temperature;

[0013] (7) Coiling: After the hot-rolled steel strip is cooled, it is coiled to obtain a hot-rolled wide steel strip with a thickness of 2.6 mm to 4.8 mm and a width of 1200 mm to 1350 mm;

[0014] (8) Warehousing: The hot-rolled wide steel strip after coiling is stacked in the finished product warehouse and cooled naturally;

[0015] (9) pickling, pickling the cooled hot-rolled wide steel strip to obtain a steel coil without iron oxide scale on the surface;

[0016] (10) cold rolling, including three rollings, the total cold rolling reduction of the three rollings is 1.6 mm to 2.8 mm, the total cold rolling reduction rate of the three rollings is 54% to 62%, wherein the first rolling tension is 250 KN to 320 KN, the second rolling tension is 220 KN to 300 KN, and the third rolling tension is 180 KN to 280 KN;

[0017] (11) Annealing: A full hydrogen strong convection hood annealing furnace is used to perform recrystallization annealing on the steel strip after three rolling. After the steel coil is loaded into the furnace, it is first heated to 560℃~580℃ and kept at this temperature for 1.8h~2.2h, then continued to be heated to 660℃~680℃ and kept at this temperature for 14h~15h, and then cooled to below 70℃ and taken out of the furnace;

[0018] (12) Flattening: The annealed steel strip is flattened to obtain a finished cold-rolled wide steel strip with a thickness of 1.0 mm to 2.0 mm and a width of 1200 mm to 1350 mm.

[0019] In an optional embodiment, the continuous casting speed is 1.30 m / min to 1.40 m / min.

[0020] In an optional embodiment, the continuously cast slab is heated in sequence through a preheating section, a heating section, a second heating section and a soaking section of a heating furnace, wherein the preheating section temperature is 750°C to 850°C, the first heating section temperature is 1185°C to 1225°C, the second heating section temperature is 1225°C to 1265°C, and the soaking section temperature is 1235°C to 1275°C.

[0021] In an optional embodiment, the temperature of the continuous casting slab entering the furnace in the heating step is 580° C. to 650° C., and the time in the furnace is 131 min to 155 min.

[0022] In an optional embodiment, in the hot rolling step, the finishing rolling temperature is 850°C to 870°C.

[0023] In an optional embodiment, the coiling temperature in the coiling step is 565°C to 615°C.

[0024] In an optional embodiment, the concentration of the acid solution used in the pickling step is 140 g / L to 200 g / L;

[0025] And / or, in the cold rolling step, after the steel coil is rolled up, it is cold rolled using a 1450mm single-stand reversible six-roll rolling mill.

[0026] In an optional embodiment, the yield strength of the cold-rolled wide steel strip after recrystallization annealing is 300MPa-430MPa, the tensile strength is 450MPa-600MPa, the elongation is 20%-32%, a granular pearlite structure is obtained, and the spheroidization rate is controlled above 95%.

[0027] In an optional embodiment, in the leveling step, a 1550 mm single-stand four-roller leveling machine is used to level the annealed steel strip, and the leveling elongation is 0.8% to 1.10%.

[0028] In a second aspect, the present invention provides a method for manufacturing steel of grade CR1000 / 1500HS, comprising: deforming and quenching the cold-rolled wide steel strip obtained by the method described in any one of the aforementioned embodiments.

[0029] The present invention has the following beneficial effects:

[0030] In the manufacturing method of the economical hot forming cold-rolled wide steel strip of the present invention, the steel is smelted in a converter, refined in an LF furnace, and continuously casted to obtain a 230mm thick continuous casting slab, and the continuous casting slab is directly hot-charged, heated, hot-rolled, and laminar-cooled to a coiling temperature to obtain a hot-rolled wide steel strip with a specification of 2.6-4.8mm thickness. The coiled hot-rolled wide steel strip is stored and slowly cooled to room temperature, and the obtained metallographic structure is fine lamellar pearlite; after the hot-rolled wide steel strip is pickled, a 1450mm single-frame reversible six-roll rolling mill is used for large-reduction cold rolling, and the total cold rolling reduction is controlled at 1.6mm-2.8mm, and the total cold rolling reduction rate is controlled at 54% ~62%; reciprocating cold rolling 3 times; then adopt full hydrogen strong convection hood annealing furnace for recrystallization annealing, the cold-rolled wide steel strip obtains granular pearlite structure after recrystallization annealing, and the spheroidization rate is controlled above 95%; after annealing, the cold-rolled wide steel strip is flattened, deformed and quenched to obtain martensitic structure, the martensitic grade is 4 to 6, the yield strength can reach more than 1000MPa, the tensile strength can reach more than 1500MPa, and the elongation is 6 to 9%, which meets the technical requirements of the national standard GB / T34566~2017 "Hot stamping steel plates and steel strips for automobiles" with grade CR1000 / 1500HS. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 is the recrystallization annealing temperature control curve of the cold-rolled wide steel strip in Example 1 of the present invention;

[0033] Figure 2 The fine lamellar pearlite structure obtained after the hot-rolled wide steel strip is slowly cooled in Example 1;

[0034] Figure 3 The granular pearlite structure obtained after recrystallization annealing in Example 1;

[0035] Figure 4 This is the martensitic structure obtained after deformation quenching in Example 1. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0037] The embodiment of the present invention provides a method for manufacturing an economical hot-forming cold-rolled wide steel strip, comprising:

[0038] (1) Converter smelting;

[0039] (2) LF furnace refining: after converter smelting, LF furnace refining is carried out to obtain a steel having the following chemical composition by mass percentage: C 0.22%-0.25%, Si 0.15%-0.25%, Mn 1.15%-1.30%, P≤0.018%, S≤0.005%, Cr0.15%-0.25%, Ti 0.018%-0.028%, B 0.0015%-0.0025%, Alt 0.020%-0.040%, and the remainder being Fe and unavoidable impurity elements;

[0040] (3) Slab continuous casting: after refining in an LF furnace, continuous casting is performed to obtain a continuous casting slab of 230 mm thick and 1200 mm to 1350 mm wide;

[0041] (4) heating, heating the continuous casting slab to 1235° C. to 1275° C.;

[0042] (5) hot rolling, which is to hot roll the heated continuous casting slab;

[0043] (6) laminar cooling: laminar cooling of the hot-rolled steel strip to the coiling temperature;

[0044] (7) Coiling: After the hot-rolled steel strip is cooled, it is coiled to obtain a hot-rolled wide steel strip with a thickness of 2.6 mm to 4.8 mm and a width of 1200 mm to 1350 mm;

[0045] (8) Warehousing: The hot-rolled wide steel strip after coiling is stacked in the finished product warehouse and cooled naturally;

[0046] (9) pickling, pickling the cooled hot-rolled wide steel strip to obtain a steel coil without iron oxide scale on the surface;

[0047] (10) cold rolling, including three rollings, the total cold rolling reduction of the three rollings is 1.6 mm to 2.8 mm, the total cold rolling reduction rate of the three rollings is 54% to 62%, wherein the first rolling tension is 250 KN to 320 KN, the second rolling tension is 220 KN to 300 KN, and the third rolling tension is 180 KN to 280 KN;

[0048] (11) Annealing: A full hydrogen strong convection hood annealing furnace is used to perform recrystallization annealing on the steel strip after three rolling. After the steel coil is loaded into the furnace, it is first heated to 560℃~580℃ and kept at this temperature for 1.8h~2.2h, then continued to be heated to 660℃~680℃ and kept at this temperature for 14h~15h, and then cooled to below 70℃ and taken out of the furnace;

[0049] (12) Flattening: The annealed steel strip is flattened to obtain a finished cold-rolled wide steel strip with a thickness of 1.0 mm to 2.0 mm and a width of 1200 mm to 1350 mm.

[0050] No precious alloy elements such as Nb and V are added to the cold-rolled wide steel strip prepared in the embodiment of the present application. By adjusting the chemical composition of the steel strip and each step and parameter, a cold-rolled wide steel strip product with a granular pearlite structure can be obtained, and the spheroidization rate of the cold-rolled wide steel strip can reach more than 95%, which can ensure that the tensile strength of the product after quenching reaches more than 1500MPa, has good quenching performance, and greatly reduces the alloy production cost.

[0051] In an optional embodiment, the continuous casting pulling speed is 1.30 m / min to 1.40 m / min. If the pulling speed is too high, cracks are likely to occur, and if the pulling speed is too low, it is not conducive to improving production efficiency.

[0052] In an optional embodiment, the continuously cast slab is heated in sequence through a preheating section, a heating section, a second heating section and a soaking section of a heating furnace, wherein the preheating section temperature is 750°C to 850°C, the first heating section temperature is 1185°C to 1225°C, the second heating section temperature is 1225°C to 1265°C, and the soaking section temperature is 1235°C to 1275°C.

[0053] The high-temperature rapid firing process is adopted in the implementation mode of the present application. The rapid firing temperature is conducive to improving production efficiency, but too rapid temperature rise is usually accompanied by more serious cracking problems.

[0054] In an optional embodiment, the temperature of the continuous casting slab entering the furnace in the heating step is 580°C to 650°C, and the time in the furnace is 131min to 155min. The hot charging production mode is beneficial to reducing the cracking problem of the slab, shortening the time of the slab in the furnace, saving energy consumption and improving production efficiency.

[0055] In an optional embodiment, in the hot rolling step, the finishing rolling temperature is 850°C to 870°C.

[0056] In an optional embodiment, the coiling temperature in the coiling step is 565°C to 615°C.

[0057] The use of a lower coiling temperature is conducive to obtaining a finer pearlite structure, which is conducive to improving the elongation and spheroidization rate of the cold-rolled wide steel strip. However, if the fine pearlite structure is blindly pursued and too low a temperature is used, brittle fracture problems are likely to occur. The metallographic structure obtained in the coiling step is fine lamellar pearlite.

[0058] In an optional embodiment, the concentration of the acid solution used in the pickling step is 140 g / L to 200 g / L; the pickling removes the cured iron scale on the surface of the steel strip.

[0059] In an optional embodiment, in the cold rolling step, after the steel coil is rolled up, a 1450mm single-frame reversible six-roll mill is used for cold rolling. The 1450mm single-frame reversible six-roll mill is used for high-reduction rolling, with fewer rolling passes, high production efficiency and low manufacturing cost.

[0060] In an optional embodiment, the yield strength of the cold-rolled wide steel strip after recrystallization annealing is 300MPa-430MPa, the tensile strength is 450MPa-600MPa, the elongation is 20%-32%, a granular pearlite structure is obtained, and the spheroidization rate is controlled above 95%.

[0061] In an optional embodiment, in the leveling step, a 1550 mm single-stand four-roller leveling machine is used to level the annealed steel strip, and the leveling elongation is 0.8% to 1.10%.

[0062] An embodiment of the present invention further provides a method for manufacturing steel of grade CR1000 / 1500HS, comprising: deforming and quenching the cold-rolled wide steel strip obtained by the method described in any one of the aforementioned embodiments.

[0063] After deformation quenching, the cold-rolled wide steel strip of the present invention obtains a martensitic structure, the martensitic level is 4 to 6, the yield strength of the parts can reach more than 1000 MPa, the tensile strength can reach more than 1500 MPa, and the elongation is 6% to 9%, meeting the technical requirements of the grade CR1000 / 1500HS in the national standard GB / T34566-2017 "Hot stamping steel plates and steel strips for automobiles".

[0064] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0065] Each embodiment of the present invention provides an economical hot-forming cold-rolled wide steel strip, and the specific steps are as follows:

[0066] (1) Converter smelting: conventional smelting using top and bottom double-blown converters;

[0067] (2) LF furnace refining: LF furnace refining is carried out after converter smelting, and the steel obtains the chemical composition within the set range, C: 0.22~0.25%, Si: 0.15~0.25%, Mn: 1.15~1.30%, P≤0.018%, S≤0.005%, Cr: 0.15~0.25%, Ti: 0.018~0.028%, B: 0.0015~0.0025%, Alt: 0.020~0.040%, and the rest is Fe and unavoidable impurity elements.

[0068] (3) Slab continuous casting: After refining in the LF furnace, continuous casting is carried out, and the casting speed is controlled to be 1.30m / min to 1.40m / min to obtain a continuous casting slab with a thickness of 230mm and a width of 1200 to 1350mm;

[0069] (4) Heating: The slab adopts direct hot charging production mode. The slab temperature is controlled at 580-650℃ before entering the furnace. The slab is heated after entering the furnace. The heating furnace is controlled in four areas, namely preheating section, heating section 1, heating section 2 and soaking section. The temperature of the preheating section is 750-850℃, the temperature of the heating section 1 is 1185-1225℃, the temperature of the heating section 2 is 1225-1265℃, the temperature of the soaking section is 1235-1275℃, and the time in the furnace is 131-155min.

[0070] (5) Hot rolling: The heated continuous casting slab is subjected to hot rolling, and the finishing rolling temperature is controlled to be 850-870°C;

[0071] (6) Laminar cooling: The hot-rolled steel strip is subjected to laminar cooling to the coiling temperature;

[0072] (7) Coiling: After the hot-rolled steel strip is cooled, it is coiled, and the coiling temperature is controlled to be 565-615° C. to obtain a hot-rolled wide steel strip with a thickness of 2.6-4.8 mm and a width of 1200-1350 mm; the obtained metallographic structure is fine lamellar pearlite;

[0073] (8) Slow cooling in storage: The hot-rolled wide steel strip after coiling is stacked in the finished product warehouse and naturally cooled to room temperature;

[0074] (9) Pickling: After slowly cooling to room temperature, the hot-rolled wide steel strip is pickled, and the acid concentration is controlled to be 140-200 g / L to obtain a steel coil with no iron oxide scale on the surface;

[0075] (10) Cold rolling: After the steel coil is rolled, it is rolled three times in a reciprocating manner using a 1450mm single-frame reversible six-roll mill to finally obtain the product order thickness. The total cold rolling reduction is controlled at 1.6mm to 2.8mm, and the total cold rolling reduction rate is controlled at 54% to 62%. During the first rolling, the tension is controlled at 250 to 320KN, during the second rolling, the tension is controlled at 220 to 300KN, and during the third rolling, the tension is controlled at 180 to 280KN.

[0076] (11) Annealing: After cold rolling, the steel strip is recrystallized in a full hydrogen strong convection hood annealing furnace. After the steel coil is loaded into the furnace, the temperature is raised to 560-580℃ for 2h in the first stage, and then the temperature is raised to 660-680℃ for 14-15h in the second stage. After the insulation is completed, the steel strip is cooled to below 70℃ before being taken out of the furnace. For details, see Figure 1 As shown;

[0077] (12) Leveling: After annealing, the steel strip is leveled using a 1550mm single-frame four-roller leveling machine, and the leveling elongation is controlled at 0.8% to 1.10%, to obtain a finished cold-rolled wide steel strip with a thickness of 1.0 to 2.0 mm and a width of 1200 to 1350 mm;

[0078] The step parameters and material compositions of each step in each embodiment are shown in Tables 1 to 4, wherein the fine lamellar pearlite structure obtained after slow cooling of the hot-rolled wide steel strip in Example 1 is as follows Figure 2 As shown, the granular pearlite structure obtained after recrystallization annealing in Example 1 is as follows Figure 3 As shown, the martensitic structure obtained after deformation quenching in Example 1 is as follows Figure 4 shown.

[0079] After deformation quenching, the cold-rolled wide steel strips prepared in each embodiment meet the technical requirements of the grade CR1000 / 1500HS in the national standard GB / T34566-2017 "Hot stamping steel sheets and steel strips for automobiles", specifically:

[0080] The deformation quenching step includes: after stamping the cold-rolled wide steel strip, heating it to 850-900°C, then deformation quenching it in a mold, cooling it to below 200°C and then air cooling it to room temperature.

[0081] Table 1 Chemical composition of steel in various embodiments of the present invention (mass percentage) %

[0082] Case C Mn Si S P Cr Ti B Alt Example 1 0.23 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027 Example 2 0.24 1.28 0.22 0.002 0.015 0.20 0.025 0.0022 0.026 Example 3 0.24 1.28 0.24 0.002 0.015 0.22 0.026 0.0021 0.032 Example 4 0.22 1.23 0.22 0.003 0.016 0.23 0.023 0.0022 0.033 Example 5 0.25 1.21 0.17 0.002 0.011 0.24 0.024 0.0024 0.035 Example 6 0.23 1.29 0.21 0.002 0.014 0.18 0.022 0.0024 0.023 Example 7 0.23 1.22 0.22 0.001 0.017 0.21 0.023 0.0020 0.028 Example 8 0.24 1.29 0.24 0.002 0.015 0.20 0.026 0.0019 0.026 Example 9 0.24 1.23 0.16 0.003 0.016 0.23 0.025 0.0020 0.029 Example 10 0.25 1.21 0.18 0.002 0.015 0.24 0.023 0.0018 0.030 Embodiment 11 0.24 1.24 0.21 0.002 0.013 0.22 0.027 0.0024 0.031 Example 12 0.23 1.27 0.24 0.001 0.014 0.17 0.026 0.0023 0.027 Example 13 0.22 1.28 0.22 0.003 0.012 0.18 0.024 0.0022 0.025 Embodiment 14 0.24 1.29 0.23 0.003 0.017 0.21 0.023 0.0023 0.036 Comparative Example 1 0.18 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027 Comparative Example 2 0.30 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027 Comparative Example 3 0.23 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027 Comparative Example 4 0.23 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027 Comparative Example 5 0.23 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027 Comparative Example 6 0.23 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027 Comparative Example 7 0.23 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027 Comparative Example 8 0.23 1.18 0.18 0.003 0.017 0.17 0.022 0.0017 0.027

[0083] Table 2 Manufacturing process parameters of hot-rolled wide steel strips in various embodiments of the present invention

[0084]

[0085]

[0086] Table 3 shows the manufacturing process parameters of the cold-rolled wide steel strip in various embodiments of the present invention.

[0087]

[0088]

[0089] Table 4 shows the recrystallization annealing manufacturing process parameters of the cold-rolled wide steel strip of each embodiment of the present invention

[0090]

[0091] Table 5 shows the properties and metallographic structure of the cold-rolled wide steel strips after spheroidizing annealing and deformation quenching in various embodiments of the present invention.

[0092]

[0093]

[0094] According to the above embodiments, it can be seen that the yield strength of the cold-rolled wide steel strip after recrystallization annealing is controlled at 300-430MPa, the tensile strength is controlled at 450-600MPa, the elongation is controlled at 20-32%, and a granular pearlite structure is obtained, and the spheroidization rate is controlled at more than 95%; after deformation quenching of the cold-rolled wide steel strip prepared in each embodiment, a martensitic structure is obtained, and the martensitic grade is 4-6. The yield strength of the parts can reach more than 1000MPa, the tensile strength can reach more than 1500MPa, and the elongation is 6-9%, which meets the technical requirements of the grade CR1000 / 1500HS in the national standard GB / T34566-2017 "Hot stamping steel plates and steel strips for automobiles".

[0095] It can be seen from the comparison between Example 1 and Comparative Examples 1-2 that if the carbon content is too low or too high, the mechanical properties of the product after deformation quenching will be affected, and the technical requirements of the grade CR1000 / 1500HS steel strip cannot be met after deformation quenching of the prepared cold-rolled wide steel strip; it can be seen from the comparison between Example 1 and Comparative Examples 3-4 that if the heating temperature is too low or too high, the heating uniformity will be affected, and it is very easy to cause uneven heating and fracture, and thus the grade CR1000 / 1500HS steel strip cannot be prepared; From the comparison with Comparative Examples 5 to 6, it can be seen that if the rolling tension is too low or too high, the cold rolling stability will be affected, which is very likely to cause rolling strip breakage and thickness accuracy, and thus the prepared cold-rolled wide steel strip cannot meet the technical requirements of grade CR1000 / 1500HS after deformation quenching; from the comparison between Example 1 and Comparative Examples 7 to 8, it can be seen that if the annealing temperature is too low or too high, the annealing performance will be affected, and thus the prepared cold-rolled wide steel strip cannot meet the technical requirements of grade CR1000 / 1500HS after deformation quenching;

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for manufacturing an economical hot-forming cold-rolled wide steel strip, characterized in that: include: (1) Converter smelting; (2) LF furnace refining: after converter smelting, LF furnace refining is carried out to obtain a steel having the chemical composition, by mass percentage, of C 0.22% to 0.25%, Si 0.15% to 0.25%, Mn 1.15% to 1.30%, P ≤ 0.018%, S ≤ 0.005%, Cr 0.15% to 0.25%, Ti 0.018% to 0.028%, B 0.0015% to 0.0025%, Alt 0.020% to 0.040%, and the remainder being Fe and unavoidable impurity elements; (3) Slab continuous casting: after refining in an LF furnace, continuous casting is performed to obtain a continuous casting slab of 230 mm thick and 1200 mm to 1350 mm wide; (4) heating, heating the continuous casting slab to 1235° C. to 1275° C.; (5) hot rolling, which is to hot roll the heated continuous casting slab; (6) laminar cooling: laminar cooling of the hot-rolled steel strip to the coiling temperature; (7) Coiling: After the hot-rolled steel strip is cooled, it is coiled to obtain a hot-rolled wide steel strip with a thickness of 2.6 mm to 4.8 mm and a width of 1200 mm to 1350 mm; (8) Warehousing: The hot-rolled wide steel strip after coiling is stacked in the finished product warehouse and cooled naturally; (9) pickling, pickling the cooled hot-rolled wide steel strip to obtain a steel coil without iron oxide scale on the surface; (10) cold rolling, including three rollings, the total cold rolling reduction of the three rollings is 1.6 mm to 2.8 mm, the total cold rolling reduction rate of the three rollings is 54% to 62%, wherein the first rolling tension is 250 KN to 320 KN, the second rolling tension is 220 KN to 300 KN, and the third rolling tension is 180 KN to 280 KN; (11) Annealing: A full hydrogen strong convection hood annealing furnace is used to perform recrystallization annealing on the steel strip after three rolling. After the steel coil is loaded into the furnace, it is first heated to 560℃~580℃ and kept at this temperature for 1.8h~2.2h, then continued to be heated to 660℃~680℃ and kept at this temperature for 14h~15h, and then cooled to below 70℃ and taken out of the furnace; (12) Flattening: The annealed steel strip is flattened to obtain a finished cold-rolled wide steel strip with a thickness of 1.0 mm to 2.0 mm and a width of 1200 mm to 1350 mm.

2. The method for manufacturing an economical hot-forming cold-rolled wide steel strip according to claim 1, characterized in that: The continuous casting speed is 1.30m / min~1.40m / min.

3. The method for manufacturing an economical hot-forming cold-rolled wide steel strip according to claim 1, characterized in that: The continuously cast slab is heated in sequence through a preheating section, a heating section, a second heating section and a soaking section of a heating furnace, wherein the temperature of the preheating section is 750°C to 850°C, the temperature of the first heating section is 1185°C to 1225°C, the temperature of the second heating section is 1225°C to 1265°C, and the temperature of the soaking section is 1235°C to 1275°C.

4. The method for manufacturing an economical hot-forming cold-rolled wide steel strip according to claim 1, characterized in that: In the heating step, the temperature of the continuous casting slab entering the furnace is 580°C to 650°C, and the time in the furnace is 131min to 155min.

5. The method for manufacturing economical hot-forming cold-rolled wide steel strip according to claim 1, characterized in that: In the hot rolling step, the finishing rolling temperature is 850°C to 870°C.

6. The method for manufacturing an economical hot-forming cold-rolled wide steel strip according to claim 1, characterized in that: The coiling temperature in the coiling step is 565°C to 615°C.

7. The method for manufacturing an economical hot-forming cold-rolled wide steel strip according to claim 1, characterized in that: The acid concentration used in the pickling step is 140g / L to 200g / L; And / or, in the cold rolling step, after the steel coil is rolled up, it is cold rolled using a 1450mm single-stand reversible six-roll rolling mill.

8. The method for manufacturing economical hot-forming cold-rolled wide steel strip according to claim 1, characterized in that: The cold-rolled wide steel strip obtains a granular pearlite structure after recrystallization annealing, with a yield strength of 300MPa-430MPa, a tensile strength of 450MPa-600MPa, an elongation of 20%-32%, and a spheroidization rate controlled at more than 95%.

9. The method for manufacturing economical hot-forming cold-rolled wide steel strip according to claim 1, characterized in that: In the leveling step, a 1550mm single-frame four-roller leveling machine is used to level the annealed steel strip, and the leveling elongation is 0.8% to 1.10%.

10. A method for manufacturing steel of grade CR1000 / 1500HS, characterized in that: include: The method is obtained by deforming and quenching the cold-rolled wide steel strip obtained by the method according to any one of claims 1 to 9.

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