Method for controlling surface cracks of high-carbon alloy steel strip

Abstract

The invention relates to a method for controlling surface cracks of a high-carbon alloy steel strip. The production process of the high-carbon alloy steel strip comprises the steps of molten iron smelting, converter top and bottom combined blowing and alloying, LF furnace refining, continuous casting, heating, rolling, laminar cooling, annealing and coiling. The method mainly aims at solving the problem that surface cracks are prone to being generated in the hot rolling and cooling process of the high-carbon alloy (such as 60Si2Mn) steel belt. By optimizing steel strip component design, rolling process parameters, cooling paths and subsequent heat treatment processes, the occurrence rate of surface cracks is remarkably reduced, and meanwhile it is guaranteed that the mechanical property of the material meets the standard requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of high-carbon alloy steel strip production, and particularly to a method for controlling surface cracks of high-carbon alloy steel strips. Background Art

[0002] 60Si2Mn steel is a widely used silicon-manganese spring steel, mainly used for making flat springs that bear large loads or helical springs with a wire diameter below 30 mm. It is also suitable for making heat-resistant springs in non-corrosive media with a working temperature below 250°C, as well as large and important coiled springs that bear alternating loads and work under high stress, and automotive shock absorption systems, etc. Due to its chemical composition design with high carbon (0.56% - 0.64%) and high silicon (1.5% - 2.0%), it is prone to surface cracks during hot processing (especially in the continuous casting and rolling processes).

[0003] With the improvement of the requirements for the surface quality of steel strips in modern industrial production, crack defects (such as M-shaped cracks, black line cracks, and edge peeling, etc.) have become the core problem restricting the product qualification rate. Especially in recent years, with the improvement of rolling capacity, the maximum thickness of the continuous casting billet has increased from 160 mm to more than 180 mm, and the solidification stress has increased significantly, further exacerbating the crack incidence rate (usually reaching more than 5%), seriously affecting the yield rate of downstream processing processes (such as slitting and quenching).

[0004] At the process level, the traditional continuous casting process uses a high casting speed (about 1.60 m / min) and strong secondary cooling (specific water volume ≥ 0.73 m 3 / h), resulting in too large a temperature difference between the core and the surface of the continuous casting billet, and the straightening zone temperature is lower than 900°C, inducing phase change stress cracks. At the same time, the insufficient performance of the mold powder (such as low alkalinity and high viscosity) leads to an overly thin liquid slag layer (< 6 mm), exacerbating the friction and uneven heat transfer in the mold. In the rolling process, there are problems such as insufficient heating time of the continuous casting billet (< 130 min) and a single annealing process (such as single-stage annealing), which fail to effectively eliminate surface micro-cracks and decarburization stress, resulting in the expansion of residual defects into visible cracks in subsequent processing.

[0005] The Chinese patent application with the publication number CN 117816919 A discloses "A method for controlling surface cracks and slag inclusions of continuous casting slabs of high-carbon alloy steel". The chemical composition of the high-carbon alloy steel in weight percentage is as follows: C: 0.3% - 0.80%, Si: 0.2% - 0.45%, Mn: 0.60% - 1.20%, P ≤ 0.018%, S ≤ 0.010%, Al: 0.01% - 0.08%, Cr ≤ 5.0%, Ni ≤ 1.0%, Mo ≤ 2.2%, V ≤ 0.5%, and the rest is iron and inevitable impurities. The control method includes: 1) During continuous casting, the thickness of the continuous casting slab is 200 - 250 mm, the width is 800 - 1600 mm, and the mold powder uses a CaO-SiO 2 -Al 2 O 3 -Na 2 O-CaF 2 -B 2 O 3 multiple slag system; 2) During continuous casting, the casting speed of the continuous casting machine is 0.3 - 1.5 m / min, and the superheat of the molten steel in the tundish is 5 - 30 °C; 3) During continuous casting, control the vibration parameters of the mold. The continuous casting slab of the high-carbon alloy steel produced is directly hot-transported to the heating furnace for heating, and the surface of the hot-rolled steel plate obtained after hot rolling has no defects caused by surface cracks and slag inclusions of the slab. However, the contents of C and Si in the high-carbon alloy steel are both less than those of 60Si2Mn steel, and it only involves the continuous casting process, so it is different from the present invention.

[0006] The Chinese patent application with the publication number CN 114367645 A discloses "A method for reducing surface cracks of alloy steel and alloy steel and its preparation method", including continuous casting and heating steps; in the continuous casting step, control the upper surface temperature of the continuous casting billet in the straightening section to be greater than the lower surface temperature by 0 < ΔT ≤ 60 °C, and the lower surface temperature of the continuous casting billet in the straightening section is: 840 ≤ T ≤ 900 °C; in the heating step, there are at least two heating stages, the time of the first heating stage is 0 < t ≤ 15 min, the temperature is 1060 ≤ T ≤ 1100 °C, and the total heating time is 110 - 160 min. By controlling the straightening temperature of the continuous casting billet, the temperature difference between the upper and lower surfaces during straightening, and the heating process, the "copper embrittlement" phenomenon of the sulfuric acid dew point corrosion-resistant steel strip is effectively reduced. There are no visible edge cracks on the finished product edge, and there are no V-shaped "copper embrittlement" cracks on the plate surface, reducing the "copper embrittlement" defect rate. However, it only involves the continuous casting and billet heating processes, and the C: 0.06% - 0.09%, Si: 0.25% - 0.40% in the alloy steel it mentions are much lower than the high-carbon alloy steel described in the present invention, so it is different from the present invention. Summary of the Invention

[0007] The present invention provides a method for controlling surface cracks of high-carbon alloy steel strips, aiming at the problem that high-carbon alloy (such as 60Si2Mn) steel strips are prone to surface cracks during hot rolling and cooling processes. By optimizing the steel strip composition design, rolling process parameters, cooling path and subsequent heat treatment process, the incidence of surface cracks is significantly reduced, while ensuring that the mechanical properties of the material meet the standard requirements.

[0008] To achieve the above object, the present invention is implemented by the following technical solutions:

[0009] A method for controlling surface cracks of high-carbon alloy steel strips, the production process of high-carbon alloy steel strips includes: hot metal smelting, combined top and bottom blowing and alloying in a converter, LF furnace refining, continuous casting, heating, rolling, laminar flow cooling, annealing and coiling; the specific control is as follows:

[0010] 1) Control at the end of the converter by mass ratio: [C] ≥ 0.08%, [P] ≤ 0.015%, and the tapping temperature is 1600 - 1640 °C; control the phosphorus return amount from slag under the mass ratio ≤ 0.003%;

[0011] 2) During the LF furnace refining process, ensure that the argon blowing time ≥ 6 min before calcium treatment, and control N ≤ 45 ppm and Ti ≤ 0.002% by mass ratio at the end of refining;

[0012] 3) Control the continuous casting drawing speed at 1.45 - 1.50 m / min, adopt an ultra-weak cooling process in the secondary cooling zone, and control the cooling water flow rate of the mold: 128 - 132 m 3 / h for the wide face, 26 - 30 m 3 / h for the narrow face, and the straightening temperature ≥ 900 °C; the temperature difference between the inlet and outlet of the mold ≤ 9 °C, and control the superheat of the molten steel at 20 - 30 °C; the mold nozzle inclination angle is 14° - 16°, the immersion depth of the nozzle is 80 - 100 mm, and the outlet flow rate of the nozzle is controlled at 0.8 - 1.2 m / s;

[0013] 4) The in-furnace time during slab heating ≥ 150 min, and control the furnace inlet temperature at 646 - 738 °C; the slab surface milling amount ≥ 0.2 mm;

[0014] 5) Rolling includes rough rolling and finish rolling; the starting rolling temperature is 1050 - 1110 °C, and the finishing rolling temperature is 930 - 970 °C;

[0015] 6) The laminar flow cooling temperature is 710 - 750 °C;

[0016] 7) Adopt two-stage annealing, the first-stage annealing temperature is 500 - 550 °C, and keep warm for 1 - 2 h; the second-stage annealing temperature is 300 - 350 °C, and keep warm for 4 - 6 h; use a nitrogen-hydrogen mixed protective gas during the annealing process, and the H 2 volume ratio in the nitrogen-hydrogen mixed protective gas is 3% - 5%, and the dew point ≤ -40 °C.

[0017] The high-carbon alloy steel strip is a 60Si2Mn steel strip. The chemical components in the steel are calculated by mass percentage as follows: C: 0.58% - 0.62%; Mn: 0.77% - 0.83%; Si: 1.65% - 1.85%; S ≤ 0.010%; P ≤ 0.015%; Als: 0.015% - 0.025%; Cr: 0.15% - 0.21%.

[0018] During continuous casting, a special protective slag is used. The ternary basicity CaO / SiO 2 / AlO 3 of the protective slag is 1.05 - 1.15, the hemispherical point temperature is 1100 - 1150 °C, and the viscosity is 0.15 - 0.25 Pa·s; the consumption of the protective slag is ≥ 0.30 kg / t of steel, and the thickness of the liquid slag layer is ≥ 8 mm.

[0019] The cast billet after heating and the steel strip after rough rolling are respectively descaled.

[0020] The tensile strength of the finished steel strip is ≥ 1570 MPa, and the elongation after fracture is ≥ 12%.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1) In the prior art, the solutions for eliminating surface cracks of alloy steel strips mostly focus on a single link, including: adding titanium to refine grains through microalloying (such as the "45MnVS free-cutting non-quenched and tempered steel containing magnesium and calcium and its manufacturing method" disclosed in the Chinese patent application with the publication number CN105803308A), but excessive titanium in the steel will form brittle phases; low-temperature rolling (such as the "device for reducing the formation of zinc slag in a continuous hot-dip galvanizing zinc pot" disclosed in the Chinese patent application with the publication number CN106191729A), although it is beneficial to reduce cracks, it greatly increases the equipment load. In addition, the optimization of the protective slag is mostly limited to the adjustment of basicity, lacking the comprehensive control of the thickness of the liquid slag layer and the heat transfer coefficient. The above methods have not achieved the synergistic effect of the whole process of "steelmaking - continuous casting - rolling", resulting in a high crack rate of wide steel strips (width 600 - 780 mm) and being difficult to meet the requirements of high-end equipment manufacturing; while the present invention provides a systematic optimization solution, through the step-by-step improvement and synergistic effect of composition control, continuous casting steady-state process, improvement of protective slag performance, and rolling annealing, realizing low-cost and high-adaptability crack control.

[0023] 2) The present invention mainly aims at the problem that the 60Si2Mn steel strip is prone to surface cracks during hot rolling and cooling. By optimizing the steel strip composition design, rolling process parameters, cooling path and subsequent heat treatment process, the incidence of surface cracks is significantly reduced. Specifically, it includes: adjusting the content of residual elements in the steel (such as S, P, O, N), optimizing the temperature range of rough rolling and finish rolling, adopting gradient cooling technology to inhibit stress concentration, and at the same time combining two-stage annealing process to eliminate internal stress;

[0024] 3) The present invention can reduce the surface crack rate of the 60Si2Mn steel strip from more than 3% in the traditional process to less than 0.5%. Among them, the M-shaped crack is reduced from more than 5.2% to less than 0.8%, the black line crack is reduced from more than 3.5% to less than 0.5%, and the edge peeling defect is reduced from more than 2.1% to less than 0.3%;

[0025] 4) While significantly reducing the surface crack defects of the steel strip, ensure that the mechanical properties of the material meet the requirements of the GB / T 1222 "Spring Steel" standard, that is, the tensile strength ≥ 1570 MPa, the elongation after fracture ≥ 12%, and the toughness is improved while the strength is increased;

[0026] 5) The production cost is reduced, the unit consumption of mold powder is reduced by about 15%, and the rolling qualification rate is increased from less than 92% to more than 98%. Specific embodiments

[0027] The method for controlling the surface cracks of a high-carbon alloy steel strip described in the present invention, the production process of the high-carbon alloy steel strip includes: hot metal smelting, combined top and bottom blowing and alloying in a converter, LF furnace refining, continuous casting, heating, rolling, laminar flow cooling, annealing and coiling; The specific control is as follows:

[0028] 1) Converter end point control by mass ratio: [C] ≥ 0.08%, [P] ≤ 0.015%, tapping temperature is 1600 - 1640 °C; control the phosphorus return amount from the slag under the mass ratio ≤ 0.003%;

[0029] 2) During the LF furnace refining process, ensure that the argon blowing time ≥ 6 min before calcium treatment, and control N ≤ 45 ppm and Ti ≤ 0.002% by mass ratio at the refining end point;

[0030] 3) The continuous casting drawing speed is controlled at 1.45 - 1.50 m / min, the ultra-weak cooling process is adopted in the secondary cooling zone, and the cooling water flow rate of the mold is controlled: 128 - 132 m 3 / h for the wide face, 26 - 30 m 3 / h for the narrow face, straightening temperature ≥ 900 °C; the temperature difference between the inlet and outlet of the mold ≤ 9 °C, the superheat of the molten steel is controlled at 20 - 30 °C; the mold nozzle inclination angle is 14° - 16°, the nozzle immersion depth is 80 - 100 mm, and the nozzle outlet flow rate is controlled at 0.8 - 1.2 m / s;

[0031] 4) The residence time in the furnace during the heating of the continuous casting billet is ≥ 150 min, and the furnace inlet temperature is controlled at 646 - 738 °C; the surface milling amount of the continuous casting billet is ≥ 0.2 mm;

[0032] 5) Rolling includes rough rolling and finish rolling; the starting rolling temperature is 1050 - 1110 °C, and the finishing rolling temperature is 930 - 970 °C;

[0033] 6) The laminar cooling temperature is 710 - 750 °C;

[0034] 7) Two-stage annealing is adopted. The annealing temperature of the first stage is 500 - 550 °C, and the holding time is 1 - 2 h; the annealing temperature of the second stage is 300 - 350 °C, and the holding time is 4 - 6 h; a nitrogen-hydrogen mixed protective gas is used during the annealing process, and the volume ratio of H in the nitrogen-hydrogen mixed protective gas 2 is 3% - 5%, and the dew point is ≤ -40 °C.

[0035] The high-carbon alloy steel strip is 60Si2Mn steel strip, and the chemical composition of the steel is calculated by mass percentage as follows: C: 0.58% - 0.62%; Mn: 0.77% - 0.83%; Si: 1.65% - 1.85%; S ≤ 0.010%; P ≤ 0.015%; Als: 0.015% - 0.025%; Cr: 0.15% - 0.21%.

[0036] During the continuous casting process, a special protective slag is used. The ternary basicity CaO / SiO 2 / AlO 3 of the protective slag is 1.05 - 1.15, the hemispherical point temperature is 1100 - 1150 °C, and the viscosity is 0.15 - 0.25 Pa·s; the consumption of the protective slag is ≥ 0.30 kg / t of steel, and the thickness of the liquid slag layer is ≥ 8 mm.

[0037] The descaling treatment is carried out on the heated continuous casting billet and the steel strip after rough rolling respectively.

[0038] The tensile strength of the finished steel strip is ≥ 1570 MPa, and the elongation after fracture is ≥ 12%.

[0039] To more intuitively reflect the present invention, the implementation mode of the present invention will be further described in combination with the embodiments. The following embodiments are only the preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technical solution that can be obtained obviously by those skilled in the art within the technical scope disclosed by the present invention, including simple changes or equivalent replacements, is within the protection scope of the present invention.

[0040]

Embodiment 1

[0041] This embodiment takes the production of 60Si2Mn steel strip (specification: width 600 mm × thickness 10 mm) as an example. The production process includes hot metal smelting → combined top and bottom blowing in the converter and alloying treatment → refining in the LF furnace → continuous casting → hot charging → heating → descaling → rough rolling → descaling → finish rolling → laminar flow cooling → coiling; among which the following production processes are controlled:

[0042] 1. Converter end point control: [C]=0.09% (mass percentage), [P]=0.010% (mass percentage), tapping temperature 1620 °C. Ensure circular tapping, use a slide gate to prevent slag from tapping, and the phosphorus return amount of the tapped slag is 0.002%.

[0043] 2. Ensure the submerged arc effect during LF furnace refining and reduce the nitrogen increase amount during the refining process; the argon blowing time before calcium treatment is 8 minutes, and S=0.012%, N=42 ppm, Ti=0.0015% are controlled according to the mass ratio;

[0044] 3. During continuous casting, control the molten steel superheat degree at 25 °C, casting speed at 1.48 m / min, secondary cooling water ratio at 0.65 m 3 / h, crystallizer nozzle inclination angle at 15°; crystallizer cooling water flow rate: 130 m for the wide face 3 / h, 28 m for the narrow face 3 / h, tundish liquid level height at 816 mm, slag layer thickness at 30 mm, straightening temperature at 975 °C.

[0045] 4. Use a special mold powder for 60Si2Mn, and the ternary basicity CaO / SiO 2 / AlO 3 of the mold powder is 1.10, the hemispherical point temperature is 1130 °C, the viscosity is 0.20 Pa·s, and the mold powder consumption is 0.32 kg / t.

[0046] 5. When heating the continuous casting billet, the in-furnace time is controlled within 155 min;

[0047] 6. The finish rolling temperature is controlled at 943 °C, the laminar flow cooling temperature is controlled at 721 °C, and the surface milling amount is 0.3 mm;

[0048] 7. After rolling, two-stage annealing is adopted, and the annealing temperature and time are: 530 °C × 1.5 h + 330 °C × 5 h, and the protective gas is a nitrogen-hydrogen mixed protective gas N 2 -4% H 2 .

[0049] Final product inspection results:

[0050] 1. The inclusion control situation is shown in the following table:

[0051]

[0052] That is, the inclusions of type A, type B, type C, and type D in the finished strip steel do not exceed grade 0.5, the inclusions of type Ds are grade 1.0, and the banded structure is grade 0.5.

[0053] 2. The surface crack rate is 0.9%.

[0054] 3. The tensile strength of the finished strip steel is 1585 MPa, and the elongation is 14.1%.

[0055] 4. The central porosity of the bloom in macrostructure is grade 0.5, and there are no intermediate cracks.

[0056] Conclusion: The surface quality of the 60Si2Mn spring steel strip produced according to the control method of the present invention is good, without fine black lines and M-shaped cracks, and the surface crack defects are significantly improved compared with the conventional process.

[0057]

Example 2

[0058] This example takes the production of 45# steel strip (specification: width 650 mm × thickness 10 mm) as an example, and the production process is the same as that of Example 1; the following production process is controlled:

[0059] 1. Converter end point control: [C] = 0.09% (mass percentage), [P] = 0.010% (mass percentage), tapping temperature 1640 °C. Ensure circular tapping, use a slide gate to prevent slag from tapping, and the phosphorus return amount of the slag is 0.003%.

[0060] 2. The LF furnace refining ensures the submerged arc effect and reduces the nitrogen increase during the refining process; the argon blowing time before calcium treatment is 8 minutes, and S = 0.010%, N = 38 ppm, Ti = 0.0020% are controlled according to the mass ratio;

[0061] 3. The continuous casting controls the molten steel superheat degree to be 27 °C, the casting speed to be 1.50 m / min, the secondary cooling water ratio to be 0.65 m 3 / h, the crystallizer nozzle inclination angle to be 15°; the crystallizer cooling water flow rate: 130 m for the wide face 3 / h, 28 m for the narrow face 3 / h, the tundish liquid level height to be 816 mm, the slag layer thickness to be 30 mm, and the straightening temperature to be 975 °C.

[0062] 4. Use the special protective slag for 45# steel. The ternary basicity CaO / SiO 2 / AlO 3 is 1.10, the hemispherical point temperature is 1130 °C, the viscosity is 0.20 Pa·s, and the consumption of the protective slag is 0.32 kg / t.

[0063] 5. The residence time in the furnace during the bloom heating is controlled at 155 min;

[0064] 6. The finish rolling temperature is controlled at 943°C, the laminar cooling temperature is controlled at 721°C, and the surface milling amount is 0.3 mm;

[0065] 7. After rolling, two-stage annealing is adopted, and the annealing temperature and time are: 540°C × 1.5 h + 340°C × 5 h, and the protective gas is a nitrogen-hydrogen mixed protective gas N 2 -4% H 2 .

[0066] Final product inspection results:

[0067] 1. The inclusion control is as shown in the following table:

[0068]

[0069] That is, the inclusions of type A, type B, type C, and type D in the finished strip steel do not exceed grade 0.5, the inclusions of type Ds are grade 1.0, and the banded structure is grade 0.5.

[0070] 2. The surface crack rate is 0.9%.

[0071] 3. The tensile strength of the finished strip steel is 1580 MPa, and the elongation is 15.3%.

[0072] 4. The low magnification center porosity of the continuous casting billet is grade 0.5, and there are no intermediate cracks.

[0073] Conclusion: The surface quality of the 45# steel strip produced according to the control method of the present invention is good, there are no fine black lines and M-shaped cracks, and the surface crack defects are significantly improved compared with the conventional process.

[0074] The present invention optimizes the continuous casting steady-state process and the mold powder synergistically to solve the M-shaped cracks and black line cracks synchronously; by extending the heating time of the continuous casting billet and precisely controlling the rolling process parameters, the rolling rate of surface defects is significantly improved; the ultra-weak cooling process is adopted to reduce the thermal stress and avoid the generation of secondary cracks.

[0075] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for controlling surface cracks in a high carbon alloy steel strip, characterized in that: The production process of high carbon alloy steel strip includes: molten iron smelting, converter top and bottom composite blowing and alloying, LF furnace refining, continuous casting, heating, rolling, laminar cooling, annealing and coiling; the specific control process is as follows: 1) The converter endpoint is controlled by mass ratio: [C] ≥ 0.08%, [P] ≤ 0.015%, and the tapping temperature is 1600-1640°C; the slag rephosphorization amount is controlled by mass ratio ≤ 0.003%; 2) During the LF furnace refining process, the argon blowing time is guaranteed to be ≥6 minutes before calcium treatment, and the refining endpoint is controlled by mass ratio to be N≤45ppm and Ti≤0.002%; 3) The continuous casting speed is controlled at 1.45-1.50 m / min, the secondary cooling zone adopts ultra-weak cooling technology, and the crystallizer cooling water flow control: wide surface 128-132 m 3 / h, narrow side 26~30m 3 / h, straightening temperature ≥900℃; the temperature difference between the inlet and outlet water of the crystallizer is ≤9℃, and the superheat of the molten steel is controlled at 20-30℃; the inclination angle of the crystallizer nozzle is 14°-16°, the nozzle immersion depth is 80-100mm, and the nozzle outlet flow rate is controlled at 0.8-1.2m / s; 4) The furnace time of the billet during heating is ≥150min, and the furnace temperature is controlled at 646~738℃; the milling amount of the billet surface is ≥0.2mm; 5) Rolling includes rough rolling and finish rolling; the starting rolling temperature is 1050-1110°C, and the final rolling temperature is 930-970°C; 6) Laminar cooling temperature is 710~750℃; 7) A two-stage annealing is adopted, the first stage annealing temperature is 500-550°C, and the insulation time is 1-2h; the second stage annealing temperature is 300-350°C, and the insulation time is 4-6h; a nitrogen-hydrogen mixed protective gas is used during the annealing process, and the volume ratio of H2 in the nitrogen-hydrogen mixed protective gas is 3%-5%, and the dew point is ≤-40°C.

2. The method for controlling surface cracks of a high carbon alloy steel strip according to claim 1, characterized in that: The high carbon alloy steel strip is a 60Si2Mn steel strip, and the chemical composition of the steel is C: 0.58% to 0.62%; Mn: 0.77% to 0.83%; Si: 1.65% to 1.85%; S≤0.010%; P≤0.015% by mass percentage; Als: 0.015% ~ 0.025%; Cr: 0.15% ~ 0.21%.

3. The method for controlling surface cracks of a high carbon alloy steel strip according to claim 1, characterized in that: Special protective slag is used in the continuous casting process. The ternary basicity of the protective slag is CaO / SiO2 / AlO3 of 1.05-1.15, the hemisphere point temperature is 1100-1150°C, and the viscosity is 0.15-0.25 Pa·s; the protective slag consumption is ≥0.30kg / t steel, and the thickness of the liquid slag layer is ≥8mm.

4. The method for controlling surface cracks of a high carbon alloy steel strip according to claim 1, characterized in that: The heated ingot and the rough rolled strip are descaled separately.

5. The method for controlling surface cracks of a high carbon alloy steel strip according to claim 1, characterized in that: The tensile strength of the finished steel strip is ≥1570MPa and the elongation after fracture is ≥12%.

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