1150MPa-grade high-strength packaging steel belt as well as preparation method and application thereof

Abstract

The invention discloses a 1150MPa-grade high-strength packaging steel belt as well as a preparation method and application thereof, and relates to the technical field of steel production. Microelements Nb, B and Cr are adopted to achieve a synergistic effect, grains are refined through the Nb element, and the strength and toughness are improved; the element B inhibits the formation of proeutectoid ferrite and coarse sheet pearlite, so that the hardenability is improved, and a bainite structure is favorably obtained; and the Cr element can improve the hardness and wear resistance of the steel, and has certain tempering stability and toughness. And meanwhile, the range of Nb / B is controlled, so that good effects of solid solution strengthening and fine grain strengthening of the steel strip for packaging can be ensured, high strength of the steel strip for packaging is ensured, and meanwhile, the steel strip for packaging also has good toughness. The packaging steel strip obtained from the optimized components can be obtained without thermal refining, the packaging steel strip with good tensile strength and elongation A30 can be obtained, the environmental protection property of the production process of the packaging steel strip is improved, and meanwhile the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of steel production, and in particular to a 1150 MPa-grade high-strength steel strip for packaging, a preparation method thereof, and applications thereof. Background Art

[0002] Steel packaging strapping is a key material for packaging finished and semi-finished products such as steel and non-ferrous metals. Its performance directly impacts the safety and stability of goods during transportation and loading and unloading. To meet packaging requirements, traditional strapping must possess high strength (typically requiring a tensile strength exceeding 1100 MPa) and good toughness to prevent breakage or unraveling under challenging operating conditions. Currently, the industry generally uses a quenching and tempering heat treatment process to achieve the desired combination of mechanical properties. However, with intensifying global manufacturing competition and increasingly stringent environmental regulations, the steel industry faces dual pressures to reduce production costs and minimize its carbon footprint. Traditional quenching and tempering heat treatment processes are not only energy-intensive, involving multiple steps such as heating, quenching, and tempering, but also generate corresponding CO2 emissions. At the same time, end users are placing more stringent demands on materials: they need to reduce heat treatment steps to lower energy consumption and production costs while maintaining the original mechanical properties.

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

[0004] The purpose of the present invention is to provide a 1150MPa grade high-strength steel strip for packaging, a preparation method and an application thereof.

[0005] The present invention is achieved in that: In a first aspect, the present invention provides an 1150 MPa grade high-strength steel strip for packaging, wherein the components, by mass percentage, include C: 0.22%~0.30%, Mn: 1.30%~1.40%, Si: 0.15%~0.25%, Cr: 0.20%~0.30%, Nb: 0.015%~0.030%, B: 0.001%~0.003%, P≤0.020%, S≤0.010% and Alt: 0.010%~0.040%, the balance being Fe and unavoidable impurities; and 5≤Nb / B≤30.

[0006] In a second aspect, the present invention provides a method for preparing a steel strip for packaging as described in any of the aforementioned embodiments, comprising hot rolling a slab obtained by continuous casting to obtain a hot-rolled steel strip, and then laminar cooling, coiling and slow cooling the hot-rolled steel strip.

[0007] In a third aspect, the present invention provides a packaging steel strip according to any one of the aforementioned embodiments or a packaging steel strip obtained by the preparation method according to any one of the aforementioned embodiments, for use in a packaging process of metal or steel products.

[0008] The present invention has the following beneficial effects: The present invention provides a 1150MPa grade high-strength steel strip for packaging, its preparation method and application. By using trace elements Nb, B, and Cr for synergistic effect and controlling the range of Nb / B, it can ensure that the solid solution strengthening and fine grain strengthening of the packaging steel strip achieve good results, ensuring that the packaging steel strip has high strength and good toughness. The packaging steel strip obtained with the above optimized composition can obtain tensile strength and elongation A without quenching and tempering treatment. 30 The present invention provides a better packaging steel belt, which improves the environmental protection of the packaging steel belt production process and reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0010] Figure 1 A metallographic structure diagram of the hot-rolled steel strip for packaging provided in Example 1 of the present invention; Figure 2 The metallographic structure diagram of the packaging steel strip provided in Example 1 of the present invention; Figure 3 A metallographic structure diagram of a hot-rolled steel strip for packaging provided in Example 2 of the present invention; Figure 4 This is the metallographic structure diagram of the packaging steel strip provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0011] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0012] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0013] In a first aspect, the present invention provides an 1150 MPa grade high-strength steel strip for packaging, wherein the components, by mass percentage, include C: 0.22%~0.30%, Mn: 1.30%~1.40%, Si: 0.15%~0.25%, Cr: 0.20%~0.30%, Nb: 0.015%~0.030%, B: 0.001%~0.003%, P≤0.020%, S≤0.010% and Alt: 0.010%~0.040%, the balance being Fe and unavoidable impurities; and 5≤Nb / B≤30.

[0014] Among them, carbon is the cheapest strengthening element, which improves strength through solid solution strengthening and the formation of Fe3C carbides. However, if the content is too high, the toughness will deteriorate. Therefore, the carbon content should be selected between 0.22% and 0.30%.

[0015] Manganese dissolves in ferrite, providing solid solution strengthening. It also slows pearlite transformation and promotes bainite formation, enabling packaging steel strip to achieve high-strength microstructures even at relatively slow cooling rates. However, excessive manganese content can lead to coarse grains, so it is best to control the manganese content within a range of 1.30% to 1.40%.

[0016] Silicon has a slightly higher solid solution strengthening effect than manganese, but excessive silicon content will reduce toughness. The silicon content should be controlled between 0.15% and 0.25%.

[0017] The surface of chromium-containing steel can form a dense Cr2O3 oxide film to improve corrosion resistance; chromium can also form carbides Cr7C3 or Cr 23 C6 improves the hardness and wear resistance of steel and has certain tempering stability and toughness. Therefore, the chromium content of the present invention is controlled at 0.20% to 0.30%.

[0018] Niobium is a strong carbide and nitride forming element. A small amount of niobium can play a role in grain refinement and precipitation strengthening to improve strength and toughness. Therefore, the niobium content of the present invention is 0.015% to 0.030%.

[0019] When the boron content is controlled at 0.001%~0.003%, it can inhibit the formation of proeutectoid ferrite and coarse lamellar pearlite, while improving the hardenability, helping to expand the process window and obtain bainite structure.

[0020] Aluminum is added to steel as a deoxidizer or alloying element. Its main function in steel is to refine the grains and fix the nitrogen in the steel, thereby significantly improving the impact toughness of the steel and reducing the tendency to cold brittleness and aging. Therefore, the present invention controls the aluminum content to 0.010%~0.040%.

[0021] P and S are impurity elements in steel. The upper limit of impurity elements in steel is controlled to be P≤0.020% and S≤0.010% to improve the purity of steel and improve the plasticity and toughness of steel.

[0022] Based on the above-mentioned element contents, controlling the ratio of 5≤Nb / B≤30, preferably 5≤Nb / B≤15, can achieve synergistic strengthening of Nb and B, avoiding the negative effects of each. This ensures that the packaging steel strip achieves excellent solid solution strengthening and fine grain strengthening, ensuring high strength and good toughness.

[0023] In an optional embodiment, the metallographic structure of the hot-rolled steel strip for packaging includes pearlite, ferrite and bainite.

[0024] Preferably, the metallographic structure of the hot-rolled steel strip for packaging consists of pearlite, ferrite and bainite.

[0025] Preferably, the volume fraction of pearlite in the hot-rolled packaging steel strip is 60-70%, the volume fraction of ferrite is 15-20%, and the volume fraction of bainite is 15-20%. By controlling the pearlite, ferrite, and bainite contents of the packaging steel strip within these ranges, the packaging steel strip can be guaranteed to have good toughness while maintaining high strength, making it easier for the packaging steel strip to meet the high-strength and high-ductility packaging requirements of materials such as steel and metal.

[0026] Preferably, the tensile strength of the hot-rolled steel strip for packaging is ≥850 MPa.

[0027] In an optional embodiment, the tensile strength of the packaging steel strip is ≥1150 MPa and the elongation is >9.0%.

[0028] In a second aspect, the present invention provides a method for preparing a steel strip for packaging as described in any of the aforementioned embodiments, comprising hot rolling a slab obtained by continuous casting to obtain a hot-rolled steel strip, and then laminar cooling, coiling and slow cooling the hot-rolled steel strip.

[0029] By adopting the chemical composition provided by the present invention to prepare the steel strip for packaging, and cooperating with the above-mentioned process, the effects of solid solution strengthening, fine grain strengthening, etc. of each chemical element in the steel can be better controlled, thereby ensuring the excellent mechanical properties of the steel strip for packaging. At the same time, the preparation method provided by the present invention can avoid the use of tempering heat treatment processes such as quenching and tempering, thereby greatly increasing the environmental friendliness and economy of the production of the steel strip for packaging.

[0030] In an optional embodiment, the present invention provides a method for preparing a 1150 MPa high-strength packaging steel strip, comprising the following steps: S01, molten iron desulfurization Preferably, in order to ensure that the subsequent refining process proceeds smoothly, the molten iron is pretreated with desulfurization using the KR desulfurization process to obtain desulfurized molten iron.

[0031] Preferably, S in the desulfurized molten iron is ≤ 0.010 wt%, and the slag removal system is strictly implemented.

[0032] S02, converter smelting The desulfurized molten iron obtained in step S01 is subjected to converter smelting, and steel is tapped after the smelting is completed.

[0033] Preferably, the smelting time of the converter smelting is 40-50 min; the endpoint C content of the tapped steel is 0.06-0.20 wt%, P≤0.020 wt%; the tapping temperature is 1530-1600° C., and the tapping time is >4 min.

[0034] Preferably, the converter smelting adopts a top and bottom double-blown oxygen converter for smelting, molten iron and scrap steel are charged into the converter as raw materials, and the carbon and phosphorus contents in the molten steel are reduced to an appropriate range.

[0035] Preferably, ferrosilicon, ferromanganese, and aluminum are added to the molten steel in the ladle during tapping. The ferrosilicon and ferromanganese ensure that the mass percentages of silicon, manganese, and aluminum in the molten steel approach or equal the designed concentrations in the finished steel. The aluminum serves as a deoxidizer to ensure smooth refining.

[0036] S03, LF refining Preferably, the refining adopts LF refining, and the molten steel obtained from the converter in step S02 is subjected to LF refining to obtain refined molten steel.

[0037] Preferably, during the LF refining step, a white slag refining process is strictly implemented. For example, lime, refining slag, and fluorite may be added to the molten steel, and after slag is slaged by electrification, aluminum particles may be added to deoxidize and form the white slag. The white slag retention time may be ≥10 min.

[0038] Preferably, the LF refining process also includes adding ferrochromium alloy, ferroniobium alloy and ferrotitanium alloy to the molten steel, and further adjusting the mass percentage of C, Si, Mn, Cr, Nb, Ti and Al elements in the molten steel to make the molten steel composition reach the content of the target steel grade.

[0039] Preferably, after the molten steel composition meets the steel grade refining requirements, calcium wire is fed to make the Als content in the molten steel 0.020-0.030wt%, and the soft blowing time after calcium wire feeding is ≥12min.

[0040] Preferably, the length of the calcium feeding line is 300-450 m.

[0041] S04, continuous casting The refined molten steel obtained in step S03 is continuously cast to obtain slabs. That is, the refined molten steel is cast into slabs with a thickness of 200-250 mm by a slab continuous casting machine.

[0042] Preferably, during the continuous casting process, the temperature of the molten steel in the tundish is 1519-1539° C., and the continuous casting speed is 0.90-1.20 m / min.

[0043] Preferably, in order to prevent the slab from being too long, flame cutting is performed after the slab leaves the horizontal section of continuous casting.

[0044] S05, hot rolling In an optional embodiment, the slab obtained in step S04 is charged into a heating furnace for heating. The slab is hot charged and the charging temperature is greater than 400° C. to reduce the heat cost required by the heating furnace.

[0045] Preferably, after the heating is completed, a hot rolling mill is used for controlled rolling to roll the heated slab into a hot-rolled steel strip.

[0046] Preferably, during the hot rolling process, the heating temperature is 1200-1260° C., and the heating time is 160-230 min.

[0047] Preferably, during the hot rolling process, the rough rolling outlet temperature is 1010-1080°C, and the finishing rolling temperature is 850-900°C.

[0048] S06, coiling In an optional embodiment, the hot-rolled steel strip is laminar-cooled to a temperature of 590-620° C. before being coiled, and the coiled steel strip is slowly cooled for 36-72 hours.

[0049] The hot-rolled steel strip is controlled to a certain temperature through laminar cooling to promote the precipitation and strengthening of various components in the steel, thereby improving the mechanical properties of the steel. It is then coiled and slowly cooled, which is conducive to the formation of a high-strength, high-toughness structure with pearlite as the main component and ferrite and bainite as the auxiliary components.

[0050] S07, cold rolling Preferably, before cold rolling, the steel coil obtained by slow cooling in step S06 is pickled to remove surface impurities such as iron oxide scale.

[0051] In an optional embodiment, the pickled steel coil is cold rolled, the total deformation rate of the cold rolling is 50-60%, and the reduction rate of the last cold rolling is 8-11%.

[0052] By controlling the deformation rate of cold rolling within the above range, the internal structure of the steel can be adjusted and the strength and toughness of the steel can be improved.

[0053] S08, longitudinal cutting The cold-rolled steel strip obtained by cold rolling in step S07 is longitudinally cut.

[0054] Preferably, the gap between the longitudinal cutting blades is 0.14 to 0.16 times the thickness of the cold-rolled steel strip, and the overlap of the longitudinal cutting blades is 0.4 to 0.6 mm.

[0055] S09, blue The steel strip obtained by longitudinal cutting is bluing treated in a mesh belt furnace.

[0056] Preferably, the heating temperature of the bluing treatment is 400-450° C., and the running belt speed is 2.0-2.5 m / min.

[0057] In a third aspect, the present invention provides a packaging steel strip according to any one of the aforementioned embodiments or a packaging steel strip obtained by the preparation method according to any one of the aforementioned embodiments, for use in a packaging process of metal or steel products.

[0058] Example 1 This embodiment provides an 1150 MPa high-strength steel strip for packaging, wherein the components, by mass percentage, include C: 0.25%, Mn: 1.33%, Si: 0.20%, Cr: 0.24%, Nb: 0.019%, B: 0.002%, P: 0.015%, S: 0.002% and Alt: 0.025%, with the balance being Fe and unavoidable impurities; Nb / B = 9.5.

[0059] This embodiment also provides a method for preparing a 1150 MPa high-strength steel strip for packaging, comprising: S01, molten iron desulfurization The KR desulfurization process is used to pre-treat the molten iron for desulfurization to obtain desulfurized molten iron. The S content in the desulfurized molten iron is 0.002wt%, and the slag removal system is strictly implemented.

[0060] S02, converter smelting The desulfurized molten iron obtained in step S01 is smelted in a top-bottom double-blown oxygen converter, and the molten iron and scrap steel are charged into the converter as raw materials. After the smelting is completed, steel is tapped, and ferrosilicon alloy, ferromanganese alloy and aluminum blocks are added to the molten steel in the ladle during tapping.

[0061] Among them, the smelting time of converter smelting is 42 minutes; the endpoint C content of the molten steel is 0.078wt%, and the P is 0.013wt%; the tapping temperature is 1560℃, and the tapping time is 5 minutes.

[0062] S03, LF refining The molten steel obtained from the converter in step S02 is subjected to LF refining to obtain refined molten steel.

[0063] In the LF refining step, lime, refining slag and fluorite are added to the molten steel. After electrification to slag, aluminum particles are added to deoxidize and make white slag. The white slag refining process system is strictly implemented, and the white slag is kept for 12 minutes.

[0064] Ferrochromium alloy, ferroniobium alloy and ferrotitanium alloy are added to the molten steel, and the mass percentages of C, Si, Mn, Cr, Nb, Ti and Al elements in the molten steel are further adjusted so that the composition of the molten steel reaches the content of the target steel grade.

[0065] After the composition of the molten steel meets the steel grade refining requirements, the calcium line is fed for 350m. At the same time, the Als content in the molten steel is 0.025wt%, and the soft blowing time after feeding the calcium line is 15min.

[0066] S04, continuous casting The refined molten steel obtained in step S03 is cast into slabs with a thickness of 230 mm through a slab continuous casting machine. During the continuous casting process, the molten steel temperature in the tundish is 1523°C, the continuous casting speed is 1.0 m / min, and the slab is flame cut after exiting the continuous casting horizontal section.

[0067] S05, hot rolling The slab obtained in step S04 is loaded into a heating furnace for heating. The slab is hot loaded and the charging temperature is 539° C. to reduce the heat cost required by the heating furnace.

[0068] During the hot rolling process, the heating temperature is 1240°C for 180 minutes. After heating, the heated slab is rolled into hot-rolled steel strip using a hot rolling mill. The rough rolling exit temperature is 1060°C, and the finishing temperature is 880°C.

[0069] S06, coiling The hot rolled steel strip in step S05 is subjected to laminar cooling to a temperature of 610° C. and then coiled. The coiled steel strip is placed in a slow cooling pit for slow cooling for 48 hours.

[0070] S07, cold rolling The steel coil obtained by slow cooling in step S06 is pickled to remove surface impurities such as iron oxide scale, etc. The pickled steel coil is then cold rolled, with a total cold rolling deformation rate of 55% and a final cold rolling reduction rate of 10%.

[0071] S08, longitudinal cutting The cold-rolled steel strip obtained by cold rolling in step S07 is longitudinally cut, and the gap between the longitudinal cutting blades is 0.15 times the thickness of the cold-rolled steel strip, and the overlap of the longitudinal cutting blades is 0.5 mm.

[0072] S09, blue The steel strip obtained by longitudinal cutting in step S08 is bluing treated in a mesh belt furnace. The heating temperature for the bluing treatment is 430° C. and the belt speed is 2.2 m / min.

[0073] The hot-rolled steel strip obtained in step S06 of this embodiment and the packaging steel strip obtained in step S09 were respectively placed under a metallographic microscope for observation, and the following results were obtained: Figure 1 and Figure 2 The results are shown. Figure 1 It can be seen that the hot-rolled steel strip provided by the embodiment of the present invention contains a large amount of pearlite and part of ferrite and bainite; Figure 2 It can be seen that the packaging steel strip contains a large amount of deformed pearlite and part of ferrite and bainite, among which the volume fraction of pearlite is 66%, the volume fraction of ferrite is 19%, and the volume fraction of bainite is 15%.

[0074] Example 2 This embodiment provides an 1150 MPa high-strength steel strip for packaging, wherein the components, by mass percentage, include C: 0.26%, Mn: 1.38%, Si: 0.23%, Cr: 0.26%, Nb: 0.022%, B: 0.002%, P: 0.014%, S: 0.003% and Alt: 0.019%, with the balance being Fe and unavoidable impurities; and Nb / B=11.

[0075] This embodiment also provides a method for preparing a 1150 MPa high-strength steel strip for packaging, comprising: S01, molten iron desulfurization The KR desulfurization process is used to pre-treat the molten iron for desulfurization to obtain desulfurized molten iron. The S content in the desulfurized molten iron is 0.005wt%, and the slag removal system is strictly implemented.

[0076] S02, converter smelting The desulfurized molten iron obtained in step S01 is smelted in a top-bottom double-blown oxygen converter, and the molten iron and scrap steel are charged into the converter as raw materials. After the smelting is completed, steel is tapped, and ferrosilicon alloy, ferromanganese alloy and aluminum blocks are added to the molten steel in the ladle during tapping.

[0077] Among them, the smelting time of converter smelting is 48 minutes; the endpoint C content of the molten steel is 0.079wt%, and P is 0.012wt%; the tapping temperature is 1549℃, and the tapping time is 4.5 minutes.

[0078] S03, LF refining The molten steel obtained from the converter in step S02 is subjected to LF refining to obtain refined molten steel.

[0079] In the LF refining step, lime, refining slag and fluorite are added to the molten steel. After electrification to slag, aluminum particles are added to deoxidize and make white slag. The white slag refining process system is strictly implemented, and the white slag is kept for 12 minutes.

[0080] Ferrochromium alloy, ferroniobium alloy and ferrotitanium alloy are added to the molten steel, and the mass percentages of C, Si, Mn, Cr, Nb, Ti and Al elements in the molten steel are further adjusted so that the composition of the molten steel reaches the content of the target steel grade.

[0081] After the composition of the molten steel meets the steel grade refining requirements, the calcium line is fed for 380m. At the same time, the Als content in the molten steel is 0.021wt%, and the soft blowing time after feeding the calcium line is 15min.

[0082] S04, continuous casting The refined molten steel obtained in step S03 is cast into slabs with a thickness of 230 mm through a slab continuous casting machine. During the continuous casting process, the molten steel temperature in the tundish is 1528°C, the continuous casting speed is 1.05 m / min, and the slab is flame cut after exiting the continuous casting horizontal section.

[0083] S05, hot rolling The slab obtained in step S04 is loaded into a heating furnace for heating. The slab is hot loaded and the charging temperature is 600°C to reduce the heat cost required by the heating furnace.

[0084] During the hot rolling process, the heating temperature is 1230°C for 170 minutes. After heating, the heated slab is rolled into hot-rolled steel strip using a hot rolling mill. The rough rolling exit temperature is 1050°C, and the finishing temperature is 860°C.

[0085] S06, coiling The hot-rolled steel strip in step S05 is subjected to laminar cooling to a temperature of 600° C. and then coiled. The steel coil obtained after coiling is placed in a slow cooling pit for slow cooling for 54 hours.

[0086] S07, cold rolling The steel coil obtained by slow cooling in step S06 is pickled to remove surface impurities such as iron oxide scale, etc. The pickled steel coil is then cold rolled, with a total cold rolling deformation rate of 60% and a final cold rolling reduction rate of 11%.

[0087] S08, longitudinal cutting The cold-rolled steel strip obtained by cold rolling in step S07 is longitudinally cut, and the gap between the longitudinal cutting blades is 0.16 times the thickness of the cold-rolled steel strip, and the overlap of the longitudinal cutting blades is 0.5 mm.

[0088] S09, blue The steel strip obtained by longitudinal cutting in step S08 is bluing treated in a mesh belt furnace. The heating temperature for the bluing treatment is 420° C. and the belt speed is 2.3 m / min.

[0089] The hot-rolled steel strip obtained in step S06 of this embodiment and the packaging steel strip obtained in step S09 were respectively placed under a metallographic microscope for observation, and the following results were obtained: Figure 3 and Figure 4 The results are shown. Figure 3 It can be seen that the hot-rolled steel strip provided by the embodiment of the present invention contains a large amount of pearlite and part of ferrite and bainite; Figure 4 It can be seen that the packaging steel strip contains a large amount of deformed pearlite and part of ferrite and bainite, among which the volume fraction of pearlite is 67%, the volume fraction of ferrite is 14%, and the volume fraction of bainite is 19%.

[0090] Comparative Example 1 This comparative example provides a 1150 MPa grade high-strength steel strip for packaging. The preparation method is the same as that of Example 1, except that the components, by mass percentage, include C: 0.25%, Mn: 1.34%, Si: 0.22%, Cr: 0.01%, Nb: 0.018%, B: 0.002%, P: 0.015%, S: 0.002% and Alt: 0.026%, with the balance being Fe and unavoidable impurities; Nb / B=9.

[0091] Comparative Example 2 This comparative example provides a 1150 MPa grade high-strength steel strip for packaging. The preparation method is the same as that of Example 1, except that the components, by mass percentage, include C: 0.24%, Mn: 1.33%, Si: 0.20%, Cr: 0.25%, Nb: 0.008%, B: 0.002%, P: 0.014%, S: 0.001% and Alt: 0.024%, with the balance being Fe and unavoidable impurities; Nb / B=4.

[0092] Comparative Example 3 This comparative example provides an 1150 MPa grade high-strength steel strip for packaging, which has the same elemental composition as Example 2 and a preparation method similar to Example 2, with the only difference being that step S06 is: the hot-rolled steel strip is laminar-cooled to a temperature of 680°C and then coiled, and the steel coil obtained after coiling is placed in a slow cooling pit for slow cooling for 54 hours.

[0093] Comparative Example 4 This comparative example provides an 1150 MPa grade high-strength steel strip for packaging, which has the same elemental composition as Example 2 and a preparation method similar to Example 2, with the only difference being that step S06 is: the hot-rolled steel strip is laminar-cooled to a temperature of 560°C and then coiled, and the steel coil obtained after coiling is placed in a slow cooling pit for slow cooling for 54 hours.

[0094] Comparative Example 5 This comparative example provides an 1150 MPa-grade high-strength steel strip for packaging. Its elemental composition is the same as that of Example 1, and its preparation method is similar to that of Example 1, with the only difference being that step S07 involves pickling the steel coil obtained by slow cooling in step S06 to remove surface impurities such as iron oxide scale. The pickled steel coil is then cold rolled with a total cold rolling deformation of 40% and a final cold rolling reduction of 11%.

[0095] Comparative Example 6 This comparative example provides an 1150 MPa-grade high-strength steel strip for packaging. Its elemental composition is the same as that of Example 1, and its preparation method is similar to that of Example 1, with the only difference being that step S07 involves pickling the steel coil obtained by slow cooling in step S06 to remove surface impurities such as iron oxide scale. The pickled steel coil is then cold rolled with a total cold rolling deformation of 65% and a final cold rolling reduction of 11%.

[0096] The packaging steel strips provided in Examples 1 and 2 and Comparative Examples 1 to 6, as well as the hot-rolled steel strips obtained in their preparation processes, were subjected to performance testing using the following testing methods, and the results shown in Tables 1 and 2 were obtained.

[0097] The metallographic structure test results were obtained by observation using a metallographic microscope.

[0098] Tensile strength and elongation A 30 Test according to the method specified in GB / T228.1 standard.

[0099] Table 1 Properties of hot rolled steel strip

[0100] Table 2 Performance of packaging steel straps

[0101] It can be seen from Tables 1 and 2 that the tensile strength of the steel strip for packaging provided by the embodiment of the present invention and the hot-rolled steel strip obtained in the preparation process thereof are both high, and the elongation of the steel strip for packaging is better, indicating that the steel strip for packaging provided by the embodiment of the present invention has higher strength packaging performance.

[0102] In Comparative Example 1, since no chromium element is added, the solid solution strengthening effect is poor, and the tensile strength of the hot-rolled state is low, resulting in a tensile strength of the packaging steel strip lower than 1150 MPa and a slightly poor elongation. In Comparative Example 2, since the amount of niobium added is small, Nb / B=4, and the niobium-boron ratio is low, it is difficult to play a role in refining grains and regulating phase transformation. The microstructure ratio and strength of the hot-rolled steel strip basically meet the requirements, but the obtained microstructure is coarse and the toughness is poor, resulting in the tensile strength of the packaging steel strip meeting the requirements, but the elongation is not satisfactory. The coiling temperatures of Comparative Examples 3 and 4 are both outside the target range. The coiling temperature of Comparative Example 3 is high, the relative cooling rate is slow, the microstructure ratio is inconsistent with the hot-rolled tensile strength, and the final The tensile strength of the packaging steel strip does not meet the requirements. The coiling temperature of Example 4 is low, the relatively fast cooling rate, the amount of ferrite in the structure is small, and the amount of bainite is large. Excessive bainite structure will cause the plasticity of the material to be significantly reduced, so that the elongation of the packaging steel strip does not meet the requirements; the cold rolling reduction rate of Example 5 and Example 6 is not within the target range. The total cold rolling deformation rate of Example 5 is 40%, and the elongation of the packaging steel strip is high, but the tensile strength does not meet the requirements. The total cold rolling deformation rate of Example 6 is 65%. The high deformation amount causes the dislocation density to reach saturation, and the fiber structure is over-elongated, resulting in an imbalance between strength and plasticity and a decrease in toughness. Therefore, although the packaging steel strip has high strength, the elongation is poor.

[0103] The present invention provides a 1150 MPa high-strength steel strip for packaging, a preparation method thereof, and an application thereof, which have at least the following advantages: Conventional high-strength packaging steel strips with tensile strengths exceeding 1100 MPa typically require quenching and tempering to achieve the required strength and toughness. However, the present invention utilizes a synergistic compositional design of Nb, B, and Cr. Nb refines grains, improving strength and toughness; B inhibits the formation of proeutectoid ferrite and coarse lamellar pearlite, enhancing hardenability and helping to achieve a bainitic structure; and Cr increases the steel's hardness and wear resistance, while also providing a certain degree of tempering stability and toughness.

[0104] Further combined with the hot rolling process of the present invention, a high-strength and toughness hot-rolled structure of pearlite + ferrite + bainite is obtained, and then cold-rolled with a total deformation rate of 50.0%-60.0% and bluing treatment is obtained to obtain a tensile strength of more than 1150MPa and an elongation of A 30 The high-strength packaging steel strip with a content greater than 9.0% has all technical indicators that meet the requirements of the packaging steel strip standard GB / T25820, breaking the limitation of traditional high-strength steel above 1100Mpa relying on tempering heat treatment, significantly reducing production and processing costs, and facilitating the green production of packaging steel strip.

[0105] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A 1150MPa grade high strength steel strip for packaging, characterized in that: The components, calculated by mass percentage, include C: 0.22%~0.30%, Mn: 1.30%~1.40%, Si: 0.15%~0.25%, Cr: 0.20%~0.30%, Nb: 0.015%~0.030%, B: 0.001%~0.003%, P≤0.020%, S≤0.010% and Alt: 0.010%~0.040%, with the balance being Fe and unavoidable impurities; and 5≤Nb / B≤30.

2. The packaging steel strip according to claim 1, characterized in that: The metallographic structure of the hot-rolled steel strip for packaging includes pearlite, ferrite and bainite; Preferably, in the hot-rolled steel strip for packaging, the volume fraction of pearlite is 60-70%, the volume fraction of ferrite is 15-20%, and the volume fraction of bainite is 15-20%; Preferably, the tensile strength of the hot-rolled steel strip for packaging is ≥850 MPa.

3. The packaging steel strip according to claim 1, characterized in that: The tensile strength of the packaging steel strip is ≥1150 MPa, and the elongation is >9.0%.

4. A method for preparing a packaging steel strip according to any one of claims 1 to 3, characterized in that: The method comprises hot rolling a slab obtained by continuous casting to obtain a hot-rolled steel strip, and then laminar cooling, coiling and slow cooling the hot-rolled steel strip.

5. The preparation method according to claim 4, characterized in that During the hot rolling process, the heating temperature is 1200-1260° C. and the heating time is 160-230 min. Preferably, the slab is hot charged before heating, and the charging temperature is greater than 400°C; Preferably, during the hot rolling process, the rough rolling outlet temperature is 1010-1080°C, and the finishing rolling temperature is 850-900°C.

6. The preparation method according to claim 4, characterized in that The hot rolled steel strip is cooled in a laminar flow to a temperature of 590-620° C. and then coiled; Preferably, the steel coil obtained after coiling is slowly cooled for 36 to 72 hours.

7. The preparation method according to claim 4, characterized in that The steel coil obtained after slow cooling is cold rolled, the total deformation rate of the cold rolling is 50-60%, and the reduction rate of the final cold rolling is 8-11%; Preferably, the steel coil obtained by slow cooling is pickled before cold rolling.

8. The preparation method according to claim 7, characterized in that It also includes slitting and bluing the cold-rolled steel strip obtained by cold rolling; Preferably, the heating temperature of the bluing treatment is 400-450° C., and the running belt speed is 2.0-2.5 m / min; Preferably, the gap between the longitudinal cutting blades is 0.14 to 0.16 times the thickness of the cold-rolled steel strip, and the overlap of the longitudinal cutting blades is 0.4 to 0.6 mm.

9. The preparation method according to claim 4, characterized in that The slab preparation method comprises smelting and refining desulfurized molten iron in a converter to obtain refined molten steel, and then continuously casting the refined molten steel; Preferably, S in the desulfurized iron water is ≤ 0.010 wt%; Preferably, the converter smelting time is 40-50 min; the endpoint C content of the tapped steel is 0.06-0.20 wt%, P≤0.020 wt%; the tapping temperature is 1530-1600° C., and the tapping time is >4 min; Preferably, the refining adopts LF refining, and during the LF refining process, the white slag holding time is ≥10min; after the molten steel composition meets the steel grade refining requirements, the calcium wire is fed to make the Als content in the molten steel 0.020-0.030wt%, and the soft blowing time after feeding the calcium wire is ≥12min; Preferably, during the continuous casting process, the temperature of the molten steel in the tundish is 1519-1539° C., and the continuous casting speed is 0.90-1.20 m / min.

10. Use of the packaging steel strip according to any one of claims 1 to 3 or the packaging steel strip obtained by the preparation method according to any one of claims 4 to 9 in the packaging process of metal or steel products.

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