Production process of SPA-H plate strip for thin-gauge hot-rolled container

Abstract

The invention discloses a production process of an SPA-H plate strip for a thin-gauge hot-rolled container, belongs to the field of steel and iron material processing, and aims to solve the technical problems that in the prior art, the plate shape quality, the thickness precision control, the corrosion resistance uniformity, the overall product quality and the production efficiency of the thin-gauge hot-rolled SPA-H plate strip need to be further improved. The method specifically comprises the following steps that after iron is molten, sulfur removal is conducted through a blowing method, phosphorus removal is conducted through a top-bottom combined blowing converter, after the iron, waste steel, a slag former and alloy elements are added into the converter for rough smelting, the mixture is transferred into a refining furnace for refining, finally continuous casting, rough rolling and finish rolling are conducted, cooling and coiling are conducted, and the SPA-H plate strip for the thin-gauge hot-rolled container is obtained. The strip shape quality, thickness precision control, corrosion resistance uniformity and production efficiency of the SPA-H strip are further improved through molten iron pretreatment, primary smelting, refining, rolling and cooling.

Description

Technical Field

[0001] This invention relates to the field of steel material processing, specifically to a production process for thin-gauge hot-rolled SPA-H strip for containers. Background Technology

[0002] Due to its excellent resistance to atmospheric corrosion, SPA-H steel has become a core steel material in the container manufacturing industry. As the container industry develops towards lightweight and low-cost directions, the demand for thin-gauge hot-rolled SPA-H steel strip is increasing. It can not only effectively reduce the weight of containers and reduce logistics and transportation costs, but also improve the utilization rate of container space. However, the manufacturing process of this type of steel strip still faces many technical bottlenecks, and conventional production processes are difficult to meet high-quality requirements.

[0003] Currently, the manufacturing method of thin-gauge hot-rolled SPA-H strip still needs further optimization. In the hot metal pretreatment stage, the desulfurization and dephosphorization processes are inefficient, and harmful impurities are not completely removed. Residual impurities can easily affect the purity and mechanical properties of the subsequent steel. During the smelting process, the addition ratio of alloying elements is not precise enough, and there is a lack of efficient stirring and dispersion methods, resulting in uneven distribution of elements in the molten steel. This directly causes significant differences in corrosion resistance in different parts of the strip, shortening the service life of containers. If effective organizational control measures are not taken in the continuous casting stage, it is easy to form a billet with compositional segregation or uneven grain size, which will create hidden dangers for subsequent rolling defects. In the rough rolling stage, the billet heating temperature is uneven and the homogenization time is insufficient. In the finishing rolling stage, the reduction rate is not reasonably distributed and the temperature difference between the head and tail of the strip is not optimized, which often leads to problems such as poor strip shape and excessive thickness accuracy. If stress relief treatment is ignored after cooling and coiling, it will further aggravate the internal stress of the strip and weaken the stability of corrosion resistance.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a production process for thin-gauge hot-rolled SPA-H strip for containers, which solves the technical problems in the manufacturing process of thin-gauge hot-rolled SPA-H strip in the prior art, such as the need to further improve the shape quality, thickness accuracy control, corrosion resistance uniformity, and overall product quality and production efficiency.

[0006] The objective of this invention can be achieved through the following technical solution: a production process for thin-gauge hot-rolled SPA-H sheet and strip for containers, comprising the following steps: S1. After melting iron at 1400-1600℃, desulfurization is carried out by injection and dephosphorization is carried out by top and bottom combined blowing converter to obtain pretreated molten iron; S2. Add pretreated molten iron, scrap steel, slag-forming agent and alloying elements to the converter and smelt at 1620-1680℃ for 20-30 minutes. Then transfer it to the LF refining furnace for refining. Add deoxidizer and alloy fine-tuning agent to obtain refined steel. S3. After continuous casting, rough rolling, and finish rolling of refined steel, it is cooled and coiled to obtain thin-gauge hot-rolled SPA-H strip for containers.

[0007] Further, in step S1, the injection method includes: using argon gas as a carrier, injecting desulfurizing agent through a spray gun inserted to a depth of 1.0-1.5m into the molten iron at a rate of 8-10kg / min, thereby reducing the sulfur content in the molten iron to 0.004%; the operation of the top-and-bottom combined blowing converter includes: injecting desulfurizing agent at a rate of 1.2-1.5Nm into the top of the top-and-bottom combined blowing converter. 3 Oxygen is blown in at a flow rate of / (t·min), while dephosphorizing agent is added from the charging hopper above the converter mouth at a rate of 0.03-0.15 Nm at the bottom. 3 Argon gas was blown in at a volumetric flow rate of / (t·min) to reduce the phosphorus content in the molten iron to 0.01%.

[0008] Furthermore, the desulfurizing agent is magnesium particles with a particle size of 0.5-1 mm, the phosphorus removal agent is obtained by mixing lime and dolomite in a mass ratio of 4:1, the argon concentration is 99.99%, and the oxygen concentration is 99.5%.

[0009] Furthermore, in step S2, the refining operation in the LF refining furnace includes: transferring molten steel into the LF refining furnace, then adding deoxidizer and alloy fine-tuning agent, and blowing 99.99% argon gas from the bottom at a flow rate of 140-160 L / min for 15-30 min. After refining, the temperature of the molten steel stabilizes at 1580-1620℃.

[0010] Further, in step S2, the mass ratio of the pretreated molten iron to scrap steel is 9:1-2; the slag-forming agent is composed of lime and dolomite in a mass ratio of 5:1, and the amount of slag-forming agent added is adjusted according to the slag basicity to ensure that the slag basicity is between 2.5 and 3.5; the alloying elements are obtained by mixing copper, chromium, and nickel in a mass ratio of 5:8:1; the deoxidizer is aluminum wire; and the alloy fine-tuning agent is composed of titanium wire and ferrosilicon in a mass ratio of 1:10; the alloying elements, The addition amounts of deoxidizer and alloy fine-tuning agent are to ensure that the element content in the refined steel meets the following ranges: C: 0.05-0.12%, Si: 0.20-0.50%, Mn: 0.20-0.50%, P: 0.005-0.065%, S: 0.01-0.02%, Cu: 0.25-0.55%, Cr: 0.30-1.25%, Ni: 0.05-0.12%, Ti: 0.02-0.05%.

[0011] Furthermore, in step S3, the continuous casting operation includes: adding refined steel into the continuous casting machine, using a crystallizer and end electromagnetic stirring technology, controlling the continuous casting speed to be 1.0-1.3m / min, and obtaining a continuous casting billet with a thickness of 230±5mm.

[0012] Furthermore, in step S3, the roughing operation includes: first feeding the continuously cast billet into a heating furnace, heating it at a rate of 6-12℃ / min, holding it at 1250-1280℃ for 3-4 hours, and then feeding it into a roughing mill. A 6-pass rolling mill is used to press the billet at a total reduction rate of 70-80%, and a vertical roll mill is used to control the side pressure of the vertical rolls to 30-50mm, thereby rolling a steel billet with a thickness of 35-50mm.

[0013] Furthermore, in step S3, the finishing rolling operation includes: rolling the steel billet into a coil and placing it in a hot rolling box, holding it at 1020-1050℃ for 20-30 minutes, spraying hot-rolled lubricating oil onto the surface of the steel billet and the surface of the rolled plate of the finishing mill, transferring the steel billet to the finishing mill, controlling the reduction rate of the first 3 stands of the pressing unit to be 40-50%, and the reduction rate of the last 4 stands to gradually decrease to 15%, with a threading speed of 10-11 m / s, to obtain a strip with a thickness of 1.8-3.0 mm.

[0014] Furthermore, in step S3, the cooling and coiling operation includes: placing the finished strip into a laminar flow cooling device, controlling the cooling rate at 25-35℃ / s, and when the final cooling temperature of the strip reaches 580-600℃, it is then placed into a coiler and coiled with a constant tension of 70-100kN. After coiling, the strip is sent into a slow cooling pit for heat preservation for 2-4 hours, finally obtaining thin-gauge hot-rolled SPA-H strip for containers.

[0015] The present invention has the following beneficial effects: In this invention, the efficient desulfurization and dephosphorization process in the molten iron pretreatment stage lays the foundation for pure steel. The continuous casting process employs a crystallizer and end-of-line electromagnetic stirring technology to ensure uniform microstructure of the continuously cast billet, providing a solid foundation for subsequent rolling precision. In the roughing stage, a reasonable segmented heating method achieves temperature equilibrium inside and outside the billet. Combined with multi-pass rolling and vertical roll side pressure control, the width and thickness of the billet are initially homogenized. Before finishing rolling, the heat treatment in the hot coil box reduces the temperature difference between the beginning and end of the strip. Lubricating oil spraying on the billet surface and the finishing mill plate surface optimizes the rolling environment. The finishing rolling process... The process employs a gradient reduction rate distribution strategy, combined with a shape control system and an automatic thickness control system, supplemented by precise adjustment of roll parameters, to further optimize the uniformity of metal deformation. During the cooling and winding stage, constant tension control is used to prevent deformation of the strip during winding. The entire process is interconnected, effectively avoiding shape defects and thickness deviations caused by uneven temperature and inconsistent deformation during rolling. This significantly improves the shape regularity and thickness consistency of the prepared thin strip, meeting the high-precision processing requirements of container manufacturing for thin strips.

[0016] The hot metal pretreatment stage of this invention employs injection desulfurization and top-and-bottom combined blowing converter dephosphorization processes to precisely remove harmful impurities in the steel that affect corrosion resistance, laying a pure matrix foundation for the corrosion resistance of the strip. During steelmaking, corrosion-resistant alloying elements are precisely added in specific proportions, and bottom blowing argon stirring is used in the LF refining stage to promote the uniform diffusion of alloying elements in the molten steel, avoiding local differences in corrosion resistance caused by component segregation. In the continuous casting stage, crystallizer and end electromagnetic stirring technology are used to guide the billet to form a uniform microstructure, reducing the negative impact of microstructure inhomogeneity on corrosion resistance. The heating stage employs a segmented heating method to ensure consistent internal and external temperatures of the billet. Combined with reasonable rolling control during roughing and finishing, this ensures that the strip maintains a uniform microstructure during deformation. After coiling, the strip undergoes insulation treatment in a slow cooling pit to further eliminate internal stress and prevent localized weakening of corrosion resistance caused by stress concentration. The entire process controls multiple dimensions, from matrix purity, composition distribution, and microstructure to stress elimination, to ensure consistent corrosion resistance across all parts of the strip. This provides a guarantee for the stable corrosion resistance of containers during long-term outdoor service and extends the service life of containers.

[0017] This invention establishes a production line without significant interruptions, from the efficient synergy of desulfurization by injection and dephosphorization in the hot metal pretreatment stage using a top-and-bottom combined blowing converter, to the orderly connection between converter smelting and LF refining, and then to a continuous production process from continuous casting, roughing, finishing rolling to cooling and coiling. Simultaneously, the finishing mill is equipped with a shape control system and an automatic thickness control system, which can adjust process parameters in real time, reducing manual intervention and adjustment time, further ensuring the continuity and stability of production and effectively improving overall production efficiency. Before finishing rolling, a high-pressure dephosphorization process removes oxide scale from the billet surface, avoiding surface defects caused by oxide scale residue. Furthermore, hot-rolling lubricating oil is sprayed onto the billet surface and the rolled plate surface of the finishing mill before finishing rolling, combined with lubrication rolling technology, significantly reducing friction and wear between the rolls and the strip, preventing scratches and indentations on the strip surface. In the subsequent cooling and coiling stage, constant tension control is used to avoid surface wrinkles or deformation during strip coiling, ultimately ensuring that the prepared thin-gauge hot-rolled container SPA-H strip has a smooth, defect-free, and excellent surface quality. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the microstructure of the present invention; In the figure: a is a schematic diagram obtained under a transmission electron microscope after dephosphorization rolling at a pressure of 22 MPa before finishing rolling; b is a schematic diagram obtained under a transmission electron microscope after dephosphorization rolling at a pressure of 32 MPa before finishing rolling. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 This embodiment provides a production process for thin-gauge hot-rolled SPA-H strip for containers, including the following steps: S1, Hot metal pretreatment After melting iron at 1400℃, magnesium particles with a diameter of 0.5mm are injected into the molten iron at a rate of 8kg / min using 99.99% argon gas as a carrier gas through a lance inserted 1.0m deep into the molten iron. This reduces the sulfur content of the molten iron to 0.004%. Simultaneously, 1.2Nm of argon gas is injected into the top of the top-and-bottom blown converter. 3 Oxygen with a concentration of 99.5% is blown in at a flow rate of / (t·min). Lime and dolomite with a mass ratio of 4:1 are added from the charging hopper above the converter mouth, and the bottom is charged at a flow rate of 0.03 Nm. 3 Argon gas was blown in at a volumetric flow rate of / (t·min) to reduce the phosphorus content in the molten iron to 0.01%, thus obtaining pretreated molten iron.

[0022] S2, Smelting A slag-forming agent consisting of pretreated molten iron and scrap steel in a mass ratio of 9:1, lime and dolomite in a mass ratio of 5:1, and an alloying agent consisting of copper, chromium, and nickel in a mass ratio of 5:8:1 were added to the converter. The slag basicity was adjusted using the slag-forming agent to ensure it was 2.5. The smelting was carried out at 1620℃ for 20 minutes, and then transferred to an LF refining furnace. Aluminum wire as a deoxidizer and an alloy fine-tuning agent consisting of titanium wire and ferrosilicon in a mass ratio of 1:10 were added. Argon gas with a concentration of 99.99% was blown in from the bottom at a flow rate of 140 L / min for 15 minutes to ensure that the element content in the refined steel was: C: 0.05%, Si: 0.20%, Mn: 0.20%, P: 0.005%, S: 0.01%, Cu: 0.25%, Cr: 0.30%, Ni: 0.05%, Ti: 0.02%. After refining, the temperature of the molten steel was stabilized at 1580℃ to obtain refined steel.

[0023] S3, Continuous Casting Refined steel is added to a continuous casting machine, and a crystallizer and end electromagnetic stirring technology are used to control the continuous casting speed at 1.0 m / min, resulting in a continuously cast billet with a thickness of 225 mm.

[0024] S4, rough rolling The continuously cast billet is first fed into a heating furnace and heated in sections at a rate of 6℃ / min. The temperatures of each section are as follows: 900℃ for the preheating section, 1100℃ for the first heating section, 1180℃ for the second heating section, 1230℃ for the third heating section, and 1200℃ for the soaking section. The billet is held in the soaking section for 3 hours and then enters the roughing mill. It is rolled in a 6-pass mill at a total reduction rate of 70% and a vertical roll mill is used. The side pressure of the vertical rolls is controlled at 30mm to produce a steel billet with a thickness of 35mm.

[0025] S5, precision rolling The rough-rolled steel billet is rolled into a coil and placed in a hot coil box with the ends inverted. After being held at 1020℃ for 20 minutes, it enters a high-pressure descaling box and is descaled at 22MPa. Then, hot-rolling lubricating oil is sprayed onto the surface of the steel billet and the surface of the rolled plate of the finishing mill. The steel billet is then transferred to the finishing mill. The entry temperature of the finishing mill is 1020℃ and the exit temperature is 840℃. The pressing unit controls the reduction rate of the first 3 stands to be 40%, and the reduction rate of the last 4 stands decreases to 15% for each subsequent stand. The bending roll force is set to 65t, the strip threading speed is 10m / s, and the diameter of the work roll of the penultimate stand is controlled at 650mm. After rolling, a strip with a thickness of 1.8mm is obtained.

[0026] S6, Cooling Curl The finished strip is placed in a laminar flow cooling device, and the cooling rate is controlled at 25℃ / s. When the final cooling temperature of the strip reaches 580℃, it is then put into a coiler and wound with a constant tension of 70kN. After winding, the strip is sent to a slow cooling pit for 2 hours to obtain thin-gauge hot-rolled SPA-H strip for containers.

[0027] Example 2 This embodiment provides a production process for thin-gauge hot-rolled SPA-H strip for containers, including the following steps: S1, Hot metal pretreatment After melting iron at 1500℃, magnesium particles with a diameter of 0.7mm are injected into the molten iron at a rate of 9 kg / min using 99.99% argon gas as a carrier gas through a lance inserted 1.2m deep into the molten iron. This reduces the sulfur content of the molten iron to 0.004%. Simultaneously, magnesium particles with a diameter of 1.3Nm are injected into the top of the top-and-bottom blown converter. 3 Oxygen with a concentration of 99.5% is blown in at a flow rate of / (t·min). Lime and dolomite with a mass ratio of 4:1 are added from the charging hopper above the converter mouth, and the bottom is charged at a flow rate of 0.09 Nm. 3 Argon gas was blown in at a volumetric flow rate of / (t·min) to reduce the phosphorus content in the molten iron to 0.01%, thus obtaining pretreated molten iron.

[0028] S2, Smelting A slag-forming agent consisting of pretreated molten iron and scrap steel in a mass ratio of 9:1.5, lime and dolomite in a mass ratio of 5:1, and an alloying agent consisting of copper, chromium, and nickel in a mass ratio of 5:8:1 are added to the converter. The slag basicity is adjusted using the slag-forming agent to ensure it is 3.0. The smelting is carried out at 1650℃ for 25 minutes, then transferred to an LF refining furnace. A deoxidizer, aluminum wire, and an alloy fine-tuning agent consisting of titanium wire and ferrosilicon in a mass ratio of 1:10 are added, and the mixture is then added from the bottom. Argon gas with a concentration of 99.99% was blown in at a flow rate of 150 L / min for 22 minutes to ensure that the elemental content in the refined steel was C: 0.08%, Si: 0.35%, Mn: 0.35%, P: 0.035%, S: 0.015%, Cu: 0.35%, Cr: 0.75%, Ni: 0.08%, and Ti: 0.03%. After refining, the temperature of the molten steel was stabilized at 1600℃, and refined steel was obtained.

[0029] S3, Continuous Casting Refined steel is added to a continuous casting machine, and a crystallizer and end electromagnetic stirring technology are used to control the continuous casting speed at 1.1 m / min, resulting in a continuously cast billet with a thickness of 230 mm.

[0030] S4, rough rolling The continuously cast billet is first fed into a heating furnace and heated in sections at a rate of 9℃ / min. The temperatures of each section are as follows: 950℃ for the preheating section, 1140℃ for the first heating section, 1200℃ for the second heating section, 1260℃ for the third heating section, and 1220℃ for the soaking section. The billet is held in the soaking section for 3.5 hours and then enters the roughing mill. It is rolled in a 6-pass mill at a total reduction rate of 75% and a vertical roll mill is used. The side pressure of the vertical rolls is controlled at 40mm to produce a steel billet with a thickness of 42mm.

[0031] S5, precision rolling The rough-rolled steel billet is rolled into a coil and placed in a hot coil box with the ends inverted. After being held at 1030℃ for 25 minutes, it enters a high-pressure descaling box and is descaled at 27MPa. Then, hot-rolling lubricating oil is sprayed onto the surface of the steel billet and the surface of the rolled plate of the finishing mill. The steel billet is then transferred to the finishing mill. The entry temperature of the finishing mill is 1030℃ and the exit temperature is 860℃. The pressing unit controls the reduction rate of the first 3 stands to be 45%, and the reduction rate of the last 4 stands decreases to 15% for each subsequent stand. The bending roll force is set to 70t, the strip threading speed is 10m / s, and the diameter of the work roll of the penultimate stand is controlled at 680mm. After rolling, a strip with a thickness of 2.4mm is obtained.

[0032] S6, Cooling Curl The finished strip is placed in a laminar flow cooling device, and the cooling rate is controlled at 30℃ / s. When the final cooling temperature of the strip reaches 590℃, it is then put into a coiler and wound with a constant tension of 85kN. After winding, the strip is sent to a slow cooling pit for 3 hours to obtain thin-gauge hot-rolled container SPA-H strip.

[0033] Example 3 This embodiment provides a production process for thin-gauge hot-rolled SPA-H strip for containers, including the following steps: S1, Hot metal pretreatment After melting iron at 1600℃, magnesium particles with a diameter of 1mm are injected into the molten iron at a rate of 10kg / min using 99.99% argon gas as a carrier gas through a lance inserted 1.5m deep into the molten iron. This reduces the sulfur content of the molten iron to 0.004%. Simultaneously, magnesium particles with a diameter of 1mm are injected into the top of the top-and-bottom blown converter at a rate of 1.5Nm. 3 Oxygen with a concentration of 99.5% is blown in at a flow rate of / (t·min). Lime and dolomite with a mass ratio of 4:1 are added from the charging hopper above the converter mouth, and the bottom is charged at a flow rate of 0.15 Nm. 3 Argon gas was blown in at a volumetric flow rate of / (t·min) to reduce the phosphorus content in the molten iron to 0.01%, thus obtaining pretreated molten iron.

[0034] S2, Smelting A slag-forming agent consisting of pretreated molten iron and scrap steel in a mass ratio of 9:2, lime and dolomite in a mass ratio of 5:1, and alloying elements consisting of copper, chromium, and nickel in a mass ratio of 5:8:1 were added to the converter. The slag basicity was adjusted using the slag-forming agent to ensure it was 3.5. The smelting was carried out at 1680℃ for 30 minutes, and then transferred to an LF refining furnace. Aluminum wire as a deoxidizer and an alloy fine-tuning agent consisting of titanium wire and ferrosilicon in a mass ratio of 1:10 were added. Argon gas with a concentration of 99.99% was blown in from the bottom at a flow rate of 160 L / min for 30 minutes to ensure that the element content in the refined steel was: C: 0.12%, Si: 0.50%, Mn: 0.50%, P: 0.065%, S: 0.02%, Cu: 0.55%, Cr: 1.25%, Ni: 0.12%, Ti: 0.05%. After refining, the temperature of the molten steel was stabilized at 1620℃ to obtain refined steel.

[0035] S3, Continuous Casting Refined steel is added to a continuous casting machine, and a crystallizer and end electromagnetic stirring technology are used to control the continuous casting speed at 1.3 m / min, resulting in a continuously cast billet with a thickness of 235 mm.

[0036] S4, rough rolling The continuously cast billet is first fed into a heating furnace and heated in sections at a rate of 12℃ / min. The temperatures of each section are as follows: preheating section 1000℃, first heating section 1180℃, second heating section 1230℃, third heating section 1280℃, and soaking section 1250℃. The billet is held in the soaking section for 4 hours and then enters the roughing mill. It is rolled in a 6-pass mill at 80% total reduction and a vertical roll mill is used to control the side pressure of the vertical rolls to 50mm, resulting in a steel billet with a thickness of 50mm.

[0037] S5, precision rolling The rough-rolled steel billet is rolled into a coil and placed in a hot coil box with the ends inverted. After being held at 1050℃ for 30 minutes, it enters a high-pressure descaling box and is descaled at 32MPa. Then, hot-rolling lubricating oil is sprayed onto the surface of the steel billet and the surface of the rolled plate of the finishing mill. The steel billet is then transferred to the finishing mill. The entry temperature of the finishing mill is 1050℃ and the exit temperature is 890℃. The pressing unit controls the reduction rate of the first 3 stands to be 50%, and the reduction rate of the last 4 stands to be reduced to 15% for each subsequent stand. The bending roll force is set to 75t, the strip threading speed is 11m / s, and the diameter of the work roll of the penultimate stand is controlled at 700mm. After rolling, a strip with a thickness of 3.0mm is obtained.

[0038] S6, Cooling Curl The finished strip is placed in a laminar flow cooling device, and the cooling rate is controlled at 35℃ / s. When the final cooling temperature of the strip reaches 600℃, it is then put into a coiler and wound with a constant tension of 100kN. After winding, the strip is sent to a slow cooling pit for 4 hours to obtain thin-gauge hot-rolled SPA-H strip for containers.

[0039] Performance testing: After the prepared steel billet was dephosphorized in a high-pressure dephosphorization chamber, the oxide layer thickness of the dephosphorized steel billet prepared in Examples 1-3 was observed under a transmission electron microscope. The yield strength, tensile strength, and elongation of the thin-gauge hot-rolled SPA-H steel sheets and strips for container use prepared in Examples 1-3 were determined according to standard GB / T 20887.1-2017 "High-strength hot-rolled steel sheets and strips for automobiles - Part 1: High-yield strength steels for cold forming". The specific test results are shown in Table 1 below: Table 1 - Performance Test Data of Samples Data Analysis: Comparative analysis of the data in Table 1 above shows that the yield strength of the thin-gauge hot-rolled SPA-H strip for containers prepared by this invention is 474 MPa, the tensile strength is 545 MPa, the elongation is 34%, and the oxide layer thickness is 6.0 μm. In the hot metal pretreatment stage, efficient desulfurization by injection and precise dephosphorization by top and bottom blowing converter are used to remove harmful impurities from the steel. In the LF refining stage, bottom blowing argon gas stirring is used to promote uniform diffusion of corrosion-resistant alloying elements. In the continuous casting stage, crystallizer and end electromagnetic stirring are used to ensure uniform billet structure. Rough rolling segmented heating and finishing rolling gradient reduction rate control optimize the uniformity of metal deformation. These whole-process processes control the purity, composition distribution and microstructure of steel. Therefore, in Examples 1 to 3, the yield strength and tensile strength of thin-gauge hot-rolled SPA-H strip for containers are gradually increased, and the elongation is also continuously increased, achieving a balance between high strength and excellent plasticity of the strip. Because the high-pressure dephosphorization process is used to remove the oxide scale on the surface of the billet before finishing rolling, and the hot rolling lubricating oil spraying on the surface of the billet and the finishing mill plate reduces the oxidation residue and surface damage during the rolling process, the oxide layer thickness of the strip in Examples 1 to 3 is always maintained in a low range, which provides a guarantee for the surface quality and corrosion resistance of the strip.

[0040] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A production process for thin-gauge hot-rolled SPA-H sheet and strip for containers, characterized in that, Includes the following steps: S1. After melting iron at 1400-1600℃, desulfurization is carried out by injection and dephosphorization is carried out by top and bottom combined blowing converter to obtain pretreated molten iron; S2. Add pretreated molten iron, scrap steel, slag-forming agent and alloying elements to the converter and smelt at 1620-1680℃ for 20-30 minutes. Then transfer it to the LF refining furnace for refining. Add deoxidizer and alloy fine-tuning agent to obtain refined steel. S3. After continuous casting, rough rolling, and finish rolling of refined steel, it is cooled and coiled to obtain thin-gauge hot-rolled SPA-H strip for containers.

2. The production process of a thin-gauge hot-rolled SPA-H strip for containers according to claim 1, characterized in that, In step S1, the injection method includes: using argon gas as a carrier, injecting desulfurizing agent through a spray gun inserted 1.0-1.5m deep into the molten iron at a rate of 8-10kg / min, reducing the sulfur content in the molten iron to 0.004%; the operation of the top-and-bottom combined blowing converter includes: injecting desulfurizing agent at a rate of 1.2-1.5Nm at the top of the top-and-bottom combined blowing converter. 3 Oxygen is blown in at a flow rate of / (t·min), while dephosphorizing agent is added from the charging hopper above the converter mouth at a rate of 0.03-0.15 Nm at the bottom. 3 Argon gas was blown in at a volumetric flow rate of / (t·min) to reduce the phosphorus content in the molten iron to 0.01%.

3. The production process of a thin-gauge hot-rolled SPA-H strip for containers according to claim 2, characterized in that, The desulfurizing agent is magnesium particles with a particle size of 0.5-1 mm, and the phosphorus removal agent is obtained by mixing lime and dolomite in a mass ratio of 4:1; the concentration of argon is 99.99%, and the concentration of oxygen is 99.5%.

4. The production process of a thin-gauge hot-rolled SPA-H strip for containers according to claim 1, characterized in that, In step S2, the refining operation in the LF refining furnace includes: transferring molten steel into the LF refining furnace, then adding deoxidizer and alloy fine-tuning agent, and blowing 99.99% argon gas from the bottom at a flow rate of 140-160 L / min for 15-30 min. After refining, the temperature of the molten steel is stabilized at 1580-1620℃.

5. The production process of a thin-gauge hot-rolled SPA-H strip for containers according to claim 1, characterized in that, In step S2, the mass ratio of pretreated molten iron to scrap steel is 9:1-2; the slag-forming agent is composed of lime and dolomite in a mass ratio of 5:1, and the amount of slag-forming agent added is adjusted according to the slag basicity to ensure that the slag basicity is between 2.5 and 3.5; the alloying elements are obtained by mixing copper, chromium, and nickel in a mass ratio of 5:8:1; the deoxidizer is aluminum wire; and the alloy fine-tuning agent is composed of titanium wire and ferrosilicon in a mass ratio of 1:

10. The amount of alloy fine-tuning agent added is to ensure that the element content in the refined steel meets the following ranges: C: 0.05-0.12%, Si: 0.20-0.50%, Mn: 0.20-0.50%, P: 0.005-0.065%, S: 0.01-0.02%, Cu: 0.25-0.55%, Cr: 0.30-1.25%, Ni: 0.05-0.12%, Ti: 0.02-0.05%.

6. The production process of a thin-gauge hot-rolled SPA-H strip for containers according to claim 1, characterized in that, In step S3, the continuous casting operation includes: adding refined steel into the continuous casting machine, using a crystallizer and end electromagnetic stirring technology, controlling the continuous casting speed to be 1.0-1.3m / min, and obtaining a continuous casting billet with a thickness of 230±5mm.

7. The production process of a thin-gauge hot-rolled SPA-H strip for containers according to claim 1, characterized in that, In step S3, the roughing operation includes: first feeding the continuously cast billet into a heating furnace, heating it at a rate of 6-12℃ / min, holding it at 1250-1280℃ for 3-4 hours, and then feeding it into a roughing mill. A 6-pass rolling mill is used to press the billet at a total reduction rate of 70-80%, and a vertical roll mill is used to control the side pressure of the vertical rolls to 30-50mm, so as to roll a steel billet with a thickness of 35-50mm.

8. The production process of a thin-gauge hot-rolled SPA-H strip for containers according to claim 1, characterized in that, In step S3, the finishing rolling operation includes: rolling the steel billet into a coil and placing it in a hot rolling box, holding it at 1020-1050℃ for 20-30 minutes, spraying hot rolling lubricating oil on the surface of the steel billet and the surface of the rolled plate of the finishing mill, transferring the steel billet to the finishing mill, controlling the reduction rate of the first 3 stands of the pressing unit to be 40-50%, and the reduction rate of the last 4 stands to gradually decrease to 15%, with a strip threading speed of 10-11 m / s, to obtain a strip with a thickness of 1.8-3.0 mm.

9. The production process of a thin-gauge hot-rolled SPA-H strip for containers according to claim 1, characterized in that, In step S3, the cooling and coiling operation includes: placing the finished strip into a laminar flow cooling device, controlling the cooling rate at 25-35℃ / s, and when the final cooling temperature of the strip reaches 580-600℃, it is then placed into a coiler and coiled with a constant tension of 70-100kN. After coiling, the strip is sent into a slow cooling pit for heat preservation for 2-4 hours, finally obtaining thin-gauge hot-rolled SPA-H strip for containers.

Images