Steel belt for steel toecap and preparation method of steel belt

Abstract

The invention discloses a steel strip for a steel toecap and a preparation method of the steel strip, and belongs to the technical field of ferrous metallurgy, the steel strip comprises the following chemical components in percentage by weight: 0.23%-0.30% of C, 0.17%-0.37% of Si, 0.65%-1.05% of Mn, less than or equal to 0.020% of P, less than or equal to 0.015% of S, 0.020%-0.050% of Al and the balance of Fe and unavoidable impurity elements, the sum of the components is 100%, and the balance is Fe and unavoidable impurity elements. The preparation method comprises the steps of molten steel primary smelting, LF refining, continuous casting, blank inspection, heating, rolling and curling. According to the steel strip, the components are reasonably designed, a clean steel process is adopted for smelting, and a controlled rolling and controlled cooling process is adopted for rolling, so that the purity and the hardness meet the standard requirements of the steel strip for the steel toecap in a low-risk environment.

Description

Technical Field

[0001] The present invention relates to a steel strip and a preparation method thereof, in particular to a steel strip for steel toe caps and a preparation method thereof, belonging to the technical field of steel metallurgy. Background Art

[0002] Steel toe caps are an accessory for safety shoes. As a crucial component of protective footwear, they have a wide range of applications. Made from sturdy materials like reinforced steel, these caps effectively withstand external impacts and static pressure, providing comprehensive protection for the wearer's toes. Generally, in high-risk environments, a steel toe cap with a higher hardness and enhanced protection should be selected; in low-risk environments, a steel toe cap with a moderate hardness and increased comfort can be selected. Secondly, consider the wearer's foot characteristics and comfort needs.

[0003] Safety shoes used in high-risk environments require high-quality steel toe caps that meet AN1 standards for impact resistance and can withstand at least 15kN of static pressure and 200J of impact energy. Therefore, steel toe caps are typically made from 50 steel strip, with a hardness generally controlled between 55-62HRC. However, in low-risk environments, it is necessary to develop toe caps with a moderate hardness of 22-28HRC to ensure user comfort. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to propose a steel strip for steel toe caps and a preparation method thereof in view of the shortcomings of the above-mentioned existing technologies. The steel strip has a reasonably designed composition, is smelted using a clean steel process, and is rolled using a controlled rolling and controlled cooling process to ensure that the purity and hardness meet the standard requirements for steel strip for steel toe caps in a low-risk environment.

[0005] The technical solution of the present invention to solve the above technical problems is: A steel strip for steel toe caps, the chemical composition of the steel strip being calculated by weight percentage as follows: C: 0.23%-0.30%, Si: 0.17%-0.37%, Mn: 0.65%-1.05%, P≤0.020%, S≤0.015%, Al: 0.020%-0.050%, the remainder being Fe and inevitable impurity elements, and the sum of the above components being 100%.

[0006] The technical solution further defined in the present invention is: Furthermore, in the aforementioned steel strip for steel toe caps, the chemical composition of the steel strip is calculated by weight as follows: C: 0.24%-0.28%, Si: 0.17%-0.37%, Mn: 0.75%-0.95%, P≤0.020%, S≤0.015%, Al: 0.020%-0.050%, and the remainder is Fe inevitable impurity elements, and the sum of the above components is 100%.

[0007] In the aforementioned steel strip for steel toe caps, the chemical composition of the steel strip is calculated by weight as follows: C: 0.24%-0.28%, Si: 0.20%-0.30%, Mn: 0.80%-0.95%, P≤0.018%, S≤0.012%, Al: 0.025%-0.045%, and the balance is Fe inevitable impurity elements. The sum of the above components is 100%.

[0008] The present invention also provides a method for preparing a steel strip for a steel toe cap, which specifically comprises the following steps: (1) Primary refining of molten steel The molten iron and scrap steel are initially smelted in a converter for 35-45 minutes, the tapping is ensured to have a C ≥ 0.08%, and the retained steel is ≥ 8 tons, to obtain low-oxidation and low-oxidation slag primary molten steel; (2) LF refining The primary molten steel in step (1) is transferred to LF refining, lime and fluorite are used to adjust the slag basicity to 2.5-4.5, ferrosilicon powder and Al blocks are used to adjust the refined slag to white slag and keep it for 30min-60min to obtain a high-clean steel liquid with a total non-metallic inclusion level of ≤4.0; (3) Continuous casting The molten steel is placed in a ladle for continuous casting, and the secondary cooling zone adopts a steam-water spray weak cooling method and a constant casting speed of 0.85m / min to obtain a rectangular billet without corner cracks and subcutaneous cracks; (4) Blank inspection The billet is slowly cooled or red-sent to the strip mill; (5) Heating The casting is heated by step heating, the temperature of the three heating sections and the soaking section is 1150℃-1200℃, and the total heating time is 2.5h-4.0h; (6) Rolling The ingot is rolled into finished product size after passing through the rolling mill. At the same time, the speed of the last flat roll mill is adjusted to 9-11m / s to ensure the final rolling temperature is 880-950℃, forming a fine and uniform structure. (7) Curl After the strip is finally rolled and before it is put on the flat chain, cooling water is turned on in the triangle area to ensure that the curling temperature of the strip is lower than 650℃ after passing through the flat transport chain, so as to obtain the steel strip for steel toe caps.

[0009] Furthermore, in the aforementioned method for preparing the steel strip for steel baotou, the carbon weight percentage in the primary molten steel in step (1) is ≥0.08%, the phosphorus weight percentage is ≤0.018%, and the oxygen concentration is ≤500 ppm.

[0010] In the aforementioned method for preparing the steel strip for steel baotou, in step (1), ferrosilicon and ferromanganese alloy are added when the primary molten steel is tapped, and Al is added for deoxidation.

[0011] Technical effect: When tapping the primary molten steel of the present invention, ferrosilicon, ferromanganese and Al blocks are added for deoxidation to reduce the formation of inclusions.

[0012] In the aforementioned method for preparing the steel strip for steel toe caps, in step (1), the weight percentages are 70%-90% molten steel and 10%-30% scrap steel.

[0013] In the aforementioned method for preparing the steel strip for steel toe caps, the steel strip for steel toe caps obtained in step (7) has a thickness of 2 mm to 5 mm and a width of 330 mm to 385 mm.

[0014] The beneficial effects of the present invention are: Compared with the prior art, the present invention has the following significant advantages: in order to meet market demand and develop materials for steel toe caps with moderate hardness and high comfort, the present invention provides a steel strip for steel toe caps and a preparation method thereof, the method adopts converter primary smelting, LF refining, continuous casting into 250mm×300mm square billets, and hot rolling strip steel process. Under the control of the production process, by adjusting the chemical composition to reduce carbon C: 0.23%-0.30%, increase manganese Mn: 0.65%-1.05% and Al alloy 0.020%-0.050%, the hardness of the steel toe cap after quenching and tempering meets 22 -28HRC requirement; the converter controls the carbon, oxygen and phosphorus content of the steel, the carbon weight percentage is ≥0.08%, the phosphorus weight percentage is ≤0.018%, and the oxygen concentration is ≤500ppm; LF refining controls the refining time and slag composition; continuous casting adopts intermediate cooling and constant drawing speed; billet heating controls the heating temperature and total heating time, and the final rolling temperature and curling temperature are controlled during rolling, providing hot-rolled strip with the total non-metallic inclusions ≤5.0, decarburization layer ≤0.08mm, and grain size ≥8 grades. The hardness value of the steel toe cap after being made is 22-28HRC, which meets the standard requirements of steel toe cap with moderate hardness and high comfort. DETAILED DESCRIPTION

[0015] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0016] The end point composition of the steel strip is shown in Table 1 below. Table 1 is the final composition of Baotou steel strip (wt%) element C Si Mn P S Al Example 1 0.24 0.20 0.80 0.010 0.002 0.025 Example 2 0.28 0.25 0.95 0.018 0.012 0.035 Example 3 0.25 0.30 0.88 0.013 0.005 0.030 Table 1 Composition of steel strip at the end of smelting of steel Baotou, the balance is Fe and unavoidable impurity elements, and the sum of each component is 100%. Example 1

[0017] This embodiment provides a method for preparing a steel strip for a steel toe cap, which specifically includes the following steps: The chemical composition at the smelting endpoint is shown in Table 1; (1) Primary refining of molten steel 70% by weight of molten iron and 30% by weight of scrap steel are initially refined in a converter for 35 minutes to obtain a primary molten steel having a carbon weight percentage of 0.08%, a phosphorus weight percentage of 0.010%, and an oxygen concentration of 300 ppm. ≥8 tons of steel is retained during tapping to obtain a primary molten steel having low oxidation and low oxidation slag. Ferrosilicon and ferromanganese alloy are added during tapping, and Al is added for deoxidation to reduce inclusion formation. (2) LF refining The primary molten steel in step (1) is transferred to LF refining, the slag basicity is adjusted to 2.5 using lime and fluorite, and the refined slag is adjusted to white slag using ferrosilicon powder and Al blocks and maintained for 30 minutes to obtain a high-clean steel liquid with a total non-metallic inclusion level of ≤4.0; (3) Continuous casting The molten steel with the composition and temperature meeting the set requirements is placed in a ladle for continuous casting. The secondary cooling zone adopts a steam-water spray weak cooling method and a constant casting speed of 0.85m / min to obtain a 250mm×300mm square billet without corner cracks or subcutaneous cracks. (4) Blank inspection The billet is slowly cooled or red-sent to the strip mill; (5) Heating The casting was heated by step heating, with the temperature of the three heating sections and the soaking section at 1150°C, and the total heating time was 2.5h. (6) Rolling The ingot is rolled into finished product size after passing through 21 rolling mills. At the same time, the speed of the last flat roll mill is adjusted to 9m / s to ensure the final rolling temperature of 880℃, forming a fine and uniform structure. (7) Curl After the strip is finally rolled and before it is put on the flat chain, cooling water is turned on in the triangular area to ensure that the curling temperature of the strip is 600℃ after passing through the flat transport chain, and the steel strip for steel ferrules with a thickness of 2mm and a width of 330mm-385mm is obtained. Example 2

[0018] This embodiment provides a method for preparing a steel strip for a steel toe cap, which specifically includes the following steps: The chemical composition at the smelting endpoint is shown in Table 1; (1) Primary refining of molten steel 80% by weight of molten iron and 20% of scrap steel are initially smelted in a converter for 45 minutes to obtain a primary molten steel having a carbon weight percentage of 0.12%, a phosphorus weight percentage of 0.016%, and an oxygen concentration of 500 ppm. Ten tons of steel is retained when tapping to obtain a primary molten steel with low oxidation and less oxidation slag. Ferrosilicon and ferromanganese alloy are added during tapping, and Al is added for deoxidation to reduce the formation of inclusions. (2) LF refining The primary molten steel in step (1) is transferred to LF refining, the slag basicity is adjusted to 3.5 using lime and fluorite, and the refined slag is adjusted to white slag using ferrosilicon powder and Al blocks and maintained for 60 minutes to obtain a high-clean steel liquid with a total non-metallic inclusion level of ≤4.0; (3) Continuous casting The molten steel with the composition and temperature meeting the set requirements is placed in a ladle for continuous casting. The secondary cooling zone adopts a steam-water spray weak cooling method and a constant casting speed of 0.85m / min to obtain a 250mm×300mm square billet without corner cracks or subcutaneous cracks. (4) Blank inspection The billet is slowly cooled or red-sent to the strip mill; (5) Heating The casting was heated by step heating, with the temperature of the three heating sections and the soaking section at 1200°C, and the total heating time was 4.0 h. (6) Rolling The ingot is rolled into finished product size after passing through 21 rolling mills. At the same time, the speed of the last flat roll mill is adjusted to 11m / s to ensure the final rolling temperature is 950℃, forming a fine and uniform structure. (7) Curl After the strip is finished rolling and before it is put on the flat chain, cooling water is turned on in the triangle area to ensure that the curling temperature of the strip is 650℃ after passing through the flat transport chain, and the steel strip for steel ferrules with a thickness of 5mm and a width of 330mm-385mm is obtained. Example 3

[0019] This embodiment provides a method for preparing a steel strip for a steel toe cap, which specifically includes the following steps: The chemical composition at the smelting endpoint is shown in Table 1; (1) Primary refining of molten steel 90% by weight of molten iron and 10% of scrap steel are initially refined in a converter for 45 minutes to obtain a primary molten steel having a carbon weight percentage of 0.09%, a phosphorus weight percentage of 0.013%, and an oxygen concentration of 400 ppm. 11 tons of steel is retained when tapping to obtain a primary molten steel with low oxidation and less oxidation slag. Ferrosilicon and ferromanganese alloy are added during tapping, and Al is added for deoxidation to reduce the formation of inclusions. (2) LF refining The primary molten steel in step (1) is transferred to LF refining, the slag basicity is adjusted to 4.5 using lime and fluorite, and the refined slag is adjusted to white slag using ferrosilicon powder and Al blocks and maintained for 45 minutes to obtain a high-clean steel liquid with a total non-metallic inclusion level of ≤4.0; (3) Continuous casting The molten steel with the composition and temperature meeting the set requirements is placed in a ladle for continuous casting. The secondary cooling zone adopts a steam-water spray weak cooling method and a constant casting speed of 0.85m / min to obtain a 250mm×300mm square billet without corner cracks or subcutaneous cracks. (4) Blank inspection After the billet is slowly cooled, it is shot blasted to check if there are no surface defects before being transferred to the strip steel mill; (5) Heating The casting was heated by step heating, with the temperature of the three heating sections and the soaking section at 1180°C, and the total heating time was 3.5h. (6) Rolling The ingot is rolled into finished product size after passing through 21 rolling mills. At the same time, the speed of the last flat roll mill is adjusted to 10m / s to ensure the final rolling temperature is 920℃, forming a fine and uniform structure. (7) Curl After the strip is finally rolled and before it is put on the flat chain, cooling water is turned on in the triangle area to ensure that the curling temperature of the strip is 610℃ after passing through the flat transport chain, and a steel strip for steel ferrules with a thickness of 3.5mm and a width of 330mm-385mm is obtained.

[0020] The present invention reduces carbon and increases manganese and Al alloy on the basis of 50 steel composition so that the hardness of steel toe caps after quenching and tempering meets the requirement of 22-28HRC. The clean steel smelting process and controlled rolling and cooling process are adopted to ensure that the purity and hardness meet the standard requirements of steel strips for steel toe caps.

[0021] Testing has shown that the process described in this invention can produce manganese steel hot-rolled strip with a total non-metallic inclusion count of ≤3.0, a decarburized layer of ≤0.08mm, and a grain size of ≥8.0. This hot-rolled strip, used for chains, is rolled in thicknesses of 2.0mm, 5.0mm, and 3.5mm. After being manufactured into shoe toe caps, it achieves a hardness of 22-28HRC, meeting the standard requirements for moderately hard and comfortable steel toe caps. Annual demand is 2,000 tons, with an economic benefit of 2,000 tons * 200 yuan = 400,000 yuan.

[0022] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A steel strip for steel toe caps, characterized by: The chemical composition of the steel strip is calculated by weight as follows: C: 0.23%-0.30%, Si: 0.17%-0.37%, Mn: 0.65%-1.05%, P≤0.020%, S≤0.015%, Al: 0.020%-0.050%, and the balance is Fe and inevitable impurity elements. The sum of the above components is 100%.

2. The steel strip for steel toe cap according to claim 1, characterized in that: The chemical composition of the steel strip is calculated by weight as follows: C: 0.24%-0.28%, Si: 0.17%-0.37%, Mn: 0.75%-0.95%, P≤0.020%, S≤0.015%, Al: 0.020%-0.050%, and the balance is Fe and inevitable impurity elements. The sum of the above components is 100%.

3. The steel strip for steel toe cap according to claim 1, characterized in that: The chemical composition of the steel strip is calculated by weight as follows: C: 0.24%-0.28%, Si: 0.20%-0.30%, Mn: 0.80%-0.95%, P≤0.018%, S≤0.012%, Al: 0.025%-0.045%, and the balance is Fe and inevitable impurity elements. The sum of the above components is 100%.

4. A method for preparing a steel strip according to any one of claims 1 to 3, characterized in that: The specific steps include: (1) Primary refining of molten steel The molten iron and scrap steel are initially smelted in a converter for 35-45 minutes, and the tapping is ensured to have a C ≥ 0.08% to obtain low-oxidation and low-oxidation slag primary molten steel; (2) LF refining The primary molten steel in step (1) is transferred to LF refining, lime and fluorite are used to adjust the slag basicity to 2.5-4.5, ferrosilicon powder and Al blocks are used to adjust the refined slag to white slag and keep it for 30min-60min to obtain a high-clean steel liquid with a total non-metallic inclusion level of ≤4.0; (3) Continuous casting The molten steel is placed in a ladle for continuous casting, and the secondary cooling zone adopts a steam-water spray weak cooling method and a constant casting speed of 0.85m / min to obtain a rectangular billet without corner cracks and subcutaneous cracks; (4) Blank inspection The billet is slowly cooled or red-sent to the strip mill; (5) Heating The casting is heated by step heating, the temperature of the three heating sections and the soaking section is 1150℃-1200℃, and the total heating time is 2.5h-4.0h; (6) Rolling The ingot is rolled into finished product size through the rolling mill, and the speed of the last flat roll mill is adjusted to ensure the final rolling temperature is 880-950℃, forming a fine and uniform structure; (7) Curl After the strip is finally rolled and before it is put on the flat chain, cooling water is turned on in the triangle area to ensure that the curling temperature of the strip is lower than 650℃ after passing through the flat transport chain, so as to obtain the steel strip for steel toe caps.

5. The method for preparing a steel strip for a steel toe cap according to claim 4, wherein: In the step (1), the carbon weight percentage in the primary steelmaking water is ≥0.08%, the phosphorus weight percentage is ≤0.018%, and the oxygen concentration is ≤500 ppm.

6. The method for preparing a steel strip for a steel toe cap according to claim 4, wherein: In the step (1), ferrosilicon and ferromanganese alloy are added when the primary molten steel is tapped, and Al is added for deoxidation.

7. The method for preparing a steel strip for a steel toe cap according to claim 4, wherein: In the step (1), the molten steel accounts for 70% to 90% by weight, and the scrap steel accounts for 10% to 30% by weight.

8. The method for preparing a steel strip for a steel toe cap according to claim 4, wherein: The steel strip for steel toe caps obtained in step (7) has a thickness of 2 mm to 5 mm and a width of 330 mm to 385 mm.