A method for controlling the surface of a hot-rolled steel sheet against rust-preventing mill scale

Abstract

This invention relates to the field of iron and steel metallurgy and proposes a method for controlling the corrosion-resistant iron oxide scale on the surface of hot-rolled steel plates. The method includes the following steps: First, molten steel is smelted and cast into steel billets; then, the steel billets are heated to 550-600℃ and held at an air-fuel ratio of 1.1-1.3 for 20-30 minutes; subsequently, the temperature is raised to 1100-1150℃ and held at an air-fuel ratio of 1.0-1.1 for 40-60 minutes; finally, the temperature is raised to 1180-1220℃ and held at an air-fuel ratio of 0.9-1.0 for 20-30 minutes to obtain the heated steel billet; the heated steel billet is then hot-rolled and cooled to obtain the steel plate. This technical solution solves the problems of uneven iron oxide scale growth and poor adhesion to the matrix in related technologies.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a method for controlling the rust-resistant iron oxide scale on the surface of hot-rolled steel plates. Background Technology

[0002] Surface corrosion is a long-standing technical problem for steel companies, particularly in the production and storage of hot-rolled steel plates. The essence of steel plate corrosion is the oxidation reaction of iron (Fe) in the presence of water and oxygen, producing iron oxides and hydroxides. After the hot rolling process, a layer of iron oxide scale, mainly composed of Fe3O4, forms on the surface of the steel plate, providing some protection to the substrate and delaying further corrosion. However, if the iron oxide scale is unevenly distributed or insufficiently dense, it is prone to breakage and peeling during subsequent lifting and storage, exacerbating the reddening of the steel plate surface, increasing the corrosion current density, and significantly reducing corrosion resistance. Therefore, the density, stability, and integrity of this iron oxide scale layer are crucial in determining the corrosion resistance of the steel plate.

[0003] In existing technologies, improper production process control can easily lead to uneven growth of iron oxide scale and poor adhesion to the matrix, ultimately resulting in breakage, cracking, and peeling, thus reducing the corrosion resistance of the steel plate. Especially for carbon structural steel and other steel grades without added microalloying elements, how to obtain a protective iron oxide scale with a dense structure, good integrity, and strong adhesion to the matrix through process control remains a key technical problem that urgently needs to be solved in this field. Therefore, a method for controlling the corrosion-resistant iron oxide scale on the surface of hot-rolled steel plates is needed. Summary of the Invention

[0004] This invention proposes a method for controlling the rust-resistant iron oxide scale on the surface of hot-rolled steel plates to solve or alleviate the above-mentioned problems.

[0005] The technical solution of the present invention is as follows: This invention proposes a method for controlling the rust and iron oxide scale on the surface of hot-rolled steel plates, comprising the following steps: S1. Molten steel is smelted and cast into steel billets; S2. The steel billet is heated to 550~600℃ and held at an air-fuel ratio of 1.1~1.3 for 20~30 minutes; then the temperature is raised to 1100~1150℃ and held at an air-fuel ratio of 1.0~1.1 for 40~60 minutes; finally, the temperature is raised to 1180~1220℃ and held at an air-fuel ratio of 0.9~1.0 for 20~30 minutes to obtain the heated steel billet. S3. The heated steel billet is hot-rolled and then cooled to obtain a steel plate.

[0006] As a further technical solution, the molten steel, by mass percentage, consists of the following components: C 0.15%~0.17%, Si 0.15%~0.25%, Mn 1.30%~1.40%, P≤0.025%, S≤0.020%, Alt 0.025%~0.050%, with the balance being Fe and unavoidable impurity elements.

[0007] As a further technical solution, during the hot rolling process, the finishing rolling temperature is 780~820℃.

[0008] As a further technical solution, during the cooling process, the red-hot temperature of the steel plate is 590~610℃.

[0009] As a further technical solution, the cooling is performed using a scale inhibitor aqueous solution for laminar flow cooling, wherein the total hardness of the water in the scale inhibitor aqueous solution is ≤500mg / L and the chloride ion concentration is ≤200mg / L.

[0010] As a further technical solution, the pH of the water in the scale inhibitor aqueous solution is 7.0~8.0.

[0011] As a further technical solution, the amount of scale inhibitor added in the scale inhibitor aqueous solution is 40~60 mg / L.

[0012] As a further technical solution, the scale inhibitor comprises the following raw materials in parts by weight: 6-10 parts of hydroxyethylidene diphosphonic acid, 6-10 parts of polyepoxysuccinic acid, 4-6 parts of polyacrylic acid, 5-8 parts of sodium molybdate, 2-3 parts of sodium tungstate, 2-4 parts of methylbenzotriazole, 3-5 parts of sodium dodecylbenzenesulfonate, 6-8 parts of alkyl glycoside, 1-2 parts of sodium citrate, and 260-340 parts of water.

[0013] As a further technical solution, the alkyl glycosides include alkyl glycosides APG0814 and alkyl glycosides APG1214.

[0014] As a further technical solution, the mass ratio of the alkyl glycoside APG0814 to the alkyl glycoside APG1214 is 7~9:5, preferably 8:5.

[0015] The beneficial effects of this invention are as follows: This invention discloses a method for controlling the rust-resistant iron oxide scale on the surface of hot-rolled steel plates. By employing a three-stage heating process during the billet heating stage, combined with air-fuel ratio control, the uniformity of iron oxide scale growth and its adhesion to the substrate can be improved. First, the billet is held at 550-600℃ with an air-fuel ratio of 1.1-1.3 for 20-30 minutes, forming a uniform and continuous initial oxide transition layer on the billet surface, providing a good substrate for subsequent oxide layer growth. Then, the temperature is raised to 1100-1150℃ and held at an air-fuel ratio of 1.0-1.1 for 40-60 minutes, promoting sufficient diffusion of interfacial elements between the oxide layer and the steel substrate, and enhancing interfacial adhesion. Finally, the billet is held at 1180-1220℃ in a weak oxidizing atmosphere with an air-fuel ratio of 0.9-1.0 for 20-30 minutes, effectively suppressing excessive thickening and coarsening of the iron oxide scale and the concentration of internal stress. The present invention provides a method for controlling the anti-corrosion iron oxide scale on the surface of hot-rolled steel plates. This method can make the iron oxide scale on the steel plate surface of moderate thickness and improve the bonding force between the iron oxide scale and the substrate. It also improves the problems of iron oxide scale being easy to break, crack and fall off, thus laying the foundation for improving the corrosion resistance of steel plates. Detailed Implementation

[0016] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0017] In existing technologies, the formation of iron oxide scale on the surface of hot-rolled steel plates mainly relies on conventional heating processes. The heating regime is singular and lacks precise control over the air-fuel ratio, which easily leads to uneven growth and insufficient density of the iron oxide scale. Furthermore, the scale has poor adhesion to the steel matrix, making it prone to breakage, cracking, and peeling during subsequent lifting and storage. This exacerbates the corrosion of the steel plate and reduces its corrosion resistance. In particular, for carbon structural steel without added microalloying elements, there is a lack of effective process control methods to obtain a protective iron oxide scale with a dense structure, good integrity, and strong adhesion to the matrix. This fails to fundamentally solve the corrosion problem of hot-rolled steel plates during production and storage.

[0018] To address the aforementioned deficiencies in existing technologies, the present invention addresses the critical stage of iron oxide scale formation during the heating phase by designing a three-stage heating process and precisely controlling the air-fuel ratio at different stages. This optimizes the iron oxide scale growth process in stages, first forming a uniform and continuous initial oxide transition layer, then enhancing the interfacial bonding between the oxide layer and the substrate, and finally suppressing excessive iron oxide scale growth and internal stress concentration. This results in an iron oxide scale of suitable thickness, density, uniformity, and strong adhesion, fundamentally improving the problem of easily damaged iron oxide scale and enhancing the corrosion resistance of hot-rolled steel plates, making it particularly suitable for the production of carbon structural steel.

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described through embodiments.

[0020] A specific embodiment of the present invention provides a method for controlling the rust-resistant iron oxide scale on the surface of hot-rolled steel plates, comprising the following steps: S1. Molten steel is smelted and cast into steel billets; S2. Heat the steel billet to 550~600℃ and hold it at an air-fuel ratio of 1.1~1.3 for 20~30 minutes; then heat it to 1100~1150℃ and hold it at an air-fuel ratio of 1.0~1.1 for 40~60 minutes; finally heat it to 1180~1220℃ and hold it at an air-fuel ratio of 0.9~1.0 for 20~30 minutes to obtain the heated steel billet. S3. The heated steel billet is hot-rolled and then cooled to obtain a steel plate.

[0021] In this invention, the billet heating process includes the following stages: In the first stage, the temperature is raised to 550-600℃ to avoid thermal stress caused by excessively rapid heating. The air-fuel ratio is controlled between 1.1 and 1.3, for example, any value from 1.1, 1.15, 1.2, 1.25, and 1.3, or any two values ​​within that range. At this air-fuel ratio, there is excess oxygen, which can initially remove minor oxidation impurities from the billet surface. The holding time is 20-30 minutes, for example, any value from 20 minutes, 22 minutes, 25 minutes, 28 minutes, and 30 minutes, or any two values ​​within that range, to ensure uniform billet temperature. In the second stage, the temperature is raised to 1100-1150℃, and the air-fuel ratio is adjusted to 1.0-1.1, for example, any value from 1.0, 1.02, 1.05, 1.08, and 1.1, or any two values ​​within that range. The holding time is 40-60 minutes, for example, any value between any two points from 40 minutes, 45 minutes, 50 minutes, 55 minutes, and 60 minutes, providing a good microstructure for subsequent hot rolling and oxide scale control. In the third stage, the temperature is raised to 1180-1220℃, and the air-fuel ratio is controlled at 0.9-1.0, for example, any value between any two points from 0.9, 0.92, 0.95, 0.98, and 1.0, which can form a thin and dense initial oxide layer on the surface of the billet, reducing excessive oxidation during subsequent hot rolling. The holding time is 20-30 minutes, for example, any value between any two points from 20 minutes, 23 minutes, 26 minutes, 29 minutes, and 30 minutes, ensuring the billet temperature is stable and meets the requirements of the hot rolling process.

[0022] In this invention, the molten steel is composed of the following components by mass percentage: C 0.15%~0.17%, Si 0.15%~0.25%, Mn 1.30%~1.40%, P≤0.025%, S≤0.020%, Alt 0.025%~0.050%, with the balance being Fe and unavoidable impurity elements.

[0023] In this invention, during hot rolling, the finishing rolling temperature is 780~820℃, for example, any point value or range between any two points from 780℃, 785℃, 790℃, 795℃, 800℃, 805℃, 810℃, 815℃, and 820℃. This temperature range ensures that the steel plate is rolled in the austenitic region, avoiding mixed crystal formation during rolling in the two-phase region. Simultaneously, this temperature range is within the high-temperature plastic region of FeO, making it less prone to oxide scale breakage during rolling and maintaining its integrity, thus laying the foundation for the subsequent formation of a dense iron oxide scale.

[0024] In this invention, the reheating temperature of the steel plate during the cooling process is 590~610℃, for example, any value or range between any two values ​​from 590℃, 595℃, 600℃, 605℃, and 610℃. This temperature window promotes the partial decomposition of unstable FeO into a eutectoid structure of Fe3O4+Fe. This structure is extremely dense, and due to the precipitation of fine iron particles, the bonding force between the oxide scale and the matrix is ​​significantly enhanced, forming a jagged bonding interface that ensures the oxide scale is not easily detached during subsequent processing.

[0025] In this invention, laminar flow cooling is achieved using an aqueous solution of a scale inhibitor. The total hardness of the water in the scale inhibitor aqueous solution is ≤500 mg / L, and the chloride ion concentration is ≤200 mg / L. The total hardness of the water ≤500 mg / L can be any value not exceeding 500 mg / L, such as 500 mg / L, 450 mg / L, 400 mg / L, 320 mg / L, or 280 mg / L, or any range between any two values, to prevent calcium chloride buildup. 2+ Mg 2+ During the high-temperature cooling of steel plates, scale is formed by the precipitation of carbonates on the steel plate surface, preventing uneven heat dissipation, thermal stress cracks, and under-deposit corrosion caused by scale coverage. The chloride ion concentration should be ≤200 mg / L, for example, any point value not exceeding 200 mg / L or any range between any two points such as 200 mg / L, 120 mg / L, 100 mg / L, 85 mg / L, and 65 mg / L. Chloride ions are corrosive; excessive chloride ions will damage the passivation film of the iron oxide scale. Controlling the chloride ion concentration to ≤200 mg / L can significantly reduce the risk of FeCl2 concentrate forming at microcracks in the oxide scale, preventing corrosion caused by chloride ions during warehouse storage. - This leads to deep pitting corrosion.

[0026] In this invention, the pH of the water in the scale inhibitor aqueous solution is 7.0~8.0, for example, it can be any point value among 7.0, 7.2, 7.4, 7.5, 7.6, 7.8, 8.0 and the range between any two point values.

[0027] In this invention, the amount of scale inhibitor added to the scale inhibitor aqueous solution is 40~60 mg / L, for example, it can be any point value among 40 mg / L, 45 mg / L, 50 mg / L, 55 mg / L, 60 mg / L and any range between any two point values.

[0028] In this invention, the scale inhibitor comprises the following raw materials in parts by weight: 6-10 parts of hydroxyethylidene diphosphonic acid, 6-10 parts of polyepoxysuccinic acid, 4-6 parts of polyacrylic acid, 5-8 parts of sodium molybdate, 2-3 parts of sodium tungstate, 2-4 parts of methylbenzotriazole, 3-5 parts of sodium dodecylbenzenesulfonate, 6-8 parts of alkyl glycoside, 1-2 parts of sodium citrate, and 260-340 parts of water.

[0029] In this invention, the alkyl glycosides include alkyl glycosides APG0814 and APG1214. The two alkyl glycosides work synergistically to further enhance the surface activity, dispersibility and stability of the scale inhibitor, ensuring that the scale inhibitor performs optimally during the cooling process. At the same time, they can enhance the density of the passivation film on the steel plate surface and improve the corrosion resistance.

[0030] In this invention, the mass ratio of alkyl glycoside APG0814 to alkyl glycoside APG1214 is 7~9:5, for example, it can be any value from 7:5, 7.5:5, 8:5, 8.5:5, 9:5, or any range between any two values. This mass ratio optimizes the synergistic effect of the two alkyl glycosides, ensuring both good wettability and dispersibility of the scale inhibitor aqueous solution, and enhancing the scale inhibition and corrosion inhibition effects.

[0031] The present invention will now be described in detail with reference to preferred embodiments and comparative examples. The preferred embodiments of the invention described below can be modified in various ways, and therefore the scope of the invention should not be construed as limited to the preferred embodiments described in detail below. Preferred embodiments are provided to help those skilled in the art to more readily understand the invention.

[0032] Example 1 A method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates includes the following steps: S1. Molten steel is smelted and cast into steel billets; wherein the molten steel, by mass percentage, consists of the following components: C 0.15%, Si 0.15%, Mn 1.30%, P 0.01%, S 0.010%, Alt 0.025%, with the balance being Fe and unavoidable impurity elements; S2. Heat the steel billet to 550℃ and hold it at an air-fuel ratio of 1.1 for 20 minutes; then heat it to 1100℃ and hold it at an air-fuel ratio of 1.0 for 40 minutes; finally heat it to 1180℃ and hold it at an air-fuel ratio of 0.9 for 20 minutes to obtain the heated steel billet. S3. The heated steel billet is hot-rolled, with the finishing rolling temperature controlled at 780℃. After hot rolling, the steel plate is cooled using a laminar flow cooling solution of a scale inhibitor. The scale inhibitor solution must meet the following requirements: total water hardness 320mg / L, chloride ion concentration 120mg / L, pH 7.0, and the amount of scale inhibitor added is 40mg / L. At the same time, the red-hot temperature of the steel plate must be controlled at 590℃ during the cooling process. After cooling, the steel plate is obtained. The scale inhibitor comprises the following raw materials in parts by weight: 6 parts hydroxyethylidene diphosphonic acid, 6 parts polyepoxysuccinic acid, 4 parts polyacrylic acid, 5 parts sodium molybdate, 2 parts sodium tungstate, 2 parts methylbenzotriazole, 3 parts sodium dodecylbenzenesulfonate, 6 parts alkyl glycoside, 1 part sodium citrate, and 260 parts water; the alkyl glycoside is alkyl glycoside APG0814.

[0033] Example 2 A method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates includes the following steps: S1. Molten steel is smelted and cast into steel billets; wherein, the molten steel is composed of the following components by mass percentage: C 0.17%, Si 0.25%, Mn 1.40%, P 0.025%, S 0.020%, Alt 0.050%, with the balance being Fe and unavoidable impurity elements; S2. Heat the steel billet to 550℃ and hold it at an air-fuel ratio of 1.1 for 30 minutes; then heat it to 1100℃ and hold it at an air-fuel ratio of 1.0 for 60 minutes; finally heat it to 1180℃ and hold it at an air-fuel ratio of 0.9 for 30 minutes to obtain the heated steel billet. S3. The heated steel billet is hot-rolled, with the finishing rolling temperature controlled at 780~820℃. After hot rolling, the steel plate is cooled using a laminar flow cooling solution of a scale inhibitor. The scale inhibitor solution must meet the following requirements: total water hardness 500mg / L, chloride ion concentration 200mg / L, pH 8.0, and the scale inhibitor addition amount is 60mg / L. At the same time, the red-hot temperature of the steel plate must be controlled at 610℃ during the cooling process. After cooling, the steel plate is obtained. The scale inhibitor comprises the following raw materials in parts by weight: 10 parts hydroxyethylidene diphosphonic acid, 10 parts polyepoxysuccinic acid, 6 parts polyacrylic acid, 8 parts sodium molybdate, 3 parts sodium tungstate, 4 parts methylbenzotriazole, 5 parts sodium dodecylbenzenesulfonate, 8 parts alkyl glycoside, 2 parts sodium citrate, and 340 parts water; the alkyl glycoside is alkyl glycoside APG0814.

[0034] Example 3 A method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates includes the following steps: S1. Molten steel is smelted and cast into steel billets; wherein the molten steel, by mass percentage, consists of the following components: C 0.15%, Si 0.18%, Mn 1.35%, P 0.018%, S 0.012%, Alt 0.032%, with the balance being Fe and unavoidable impurity elements; S2. Heat the steel billet to 550℃ and hold it at an air-fuel ratio of 1.1 for 25 minutes; then heat it to 1100℃ and hold it at an air-fuel ratio of 1.0 for 50 minutes; finally heat it to 1180℃ and hold it at an air-fuel ratio of 0.9 for 25 minutes to obtain the heated steel billet. S3. The heated steel billet is hot-rolled, with the finishing rolling temperature controlled at 795℃. After hot rolling, the steel plate is cooled using laminar flow water. The laminar flow cooling water must meet the following requirements: total hardness 320mg / L, chloride ion concentration 85mg / L, pH 7.5. At the same time, the red-hot temperature of the steel plate must be controlled at 600℃ during the cooling process. After cooling, the steel plate is obtained.

[0035] Example 4 A method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates includes the following steps: S1. Molten steel is smelted and cast into steel billets; wherein the molten steel, by mass percentage, consists of the following components: C 0.16%, Si 0.22%, Mn 1.38%, P 0.015%, S 0.010%, Alt 0.040%, with the balance being Fe and unavoidable impurity elements; S2. Heat the steel billet to 550℃ and hold it at an air-fuel ratio of 1.1 for 25 minutes; then heat it to 1100℃ and hold it at an air-fuel ratio of 1.0 for 50 minutes; finally heat it to 1180℃ and hold it at an air-fuel ratio of 0.9 for 25 minutes to obtain the heated steel billet. S3. The heated steel billet is hot-rolled, with the finishing rolling temperature controlled at 810℃. After hot rolling, the steel plate is cooled using laminar flow water. The laminar flow cooling water must meet the following requirements: total hardness 450mg / L, chloride ion concentration 120mg / L, pH 7.2. At the same time, the red-hot temperature of the steel plate must be controlled at 615℃ during the cooling process. After cooling, the steel plate is obtained.

[0036] Example 5 A method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates includes the following steps: S1. Molten steel is smelted and cast into steel billets; wherein the molten steel, by mass percentage, consists of the following components: C 0.17%, Si 0.20%, Mn 1.32%, P 0.020%, S 0.015%, Alt 0.028%, with the balance being Fe and unavoidable impurity elements; S2. Heat the steel billet to 550℃ and hold it at an air-fuel ratio of 1.1 for 25 minutes; then heat it to 1100℃ and hold it at an air-fuel ratio of 1.0 for 50 minutes; finally heat it to 1180℃ and hold it at an air-fuel ratio of 0.9 for 25 minutes to obtain the heated steel billet. S3. The heated steel billet is hot-rolled, with the finishing rolling temperature controlled at 785℃. After hot rolling, the steel plate is cooled using a scale inhibitor aqueous solution for laminar flow cooling. The scale inhibitor aqueous solution must meet the following requirements: total water hardness 280mg / L, chloride ion concentration 65mg / L, pH 7.8, and the scale inhibitor addition amount is 50mg / L. At the same time, the red-hot temperature of the steel plate must be controlled at 590~610℃ during the cooling process. After cooling, the steel plate is obtained. The scale inhibitor comprises the following raw materials in parts by weight: 8 parts hydroxyethylidene diphosphonic acid, 8 parts polyepoxysuccinic acid, 5 parts polyacrylic acid, 7 parts sodium molybdate, 2.5 parts sodium tungstate, 3 parts methylbenzotriazole, 4 parts sodium dodecylbenzenesulfonate, 7 parts alkyl glycoside, 1.5 parts sodium citrate, and 300 parts water; the alkyl glycoside is alkyl glycoside APG0814.

[0037] Example 6 Except for replacing step S2 with the step S2 described below, the rest is the same as in Example 1; S2. Heat the steel billet to 580℃ and hold it at an air-fuel ratio of 1.2 for 20 minutes; then heat it to 1120℃ and hold it at an air-fuel ratio of 1.05 for 40 minutes; finally heat it to 1200℃ and hold it at an air-fuel ratio of 0.95 for 20 minutes to obtain the heated steel billet.

[0038] Example 7 Except for replacing step S2 with the step S2 described below, the rest is the same as in Example 1; S2. Heat the steel billet to 600℃ and hold it at an air-fuel ratio of 1.3 for 20 minutes; then heat it to 1150℃ and hold it at an air-fuel ratio of 1.1 for 40 minutes; finally heat it to 1220℃ and hold it at an air-fuel ratio of 1.0 for 20 minutes to obtain the heated steel billet.

[0039] Example 8 Except for replacing step S3 with the step S3 described below, the rest is the same as in Example 3; S3. The heated steel billet is hot-rolled, with the finishing rolling temperature controlled at 850℃. After hot rolling, the steel plate is cooled using laminar flow water. The laminar flow cooling water must meet the following requirements: total hardness 650mg / L, chloride ion concentration 280mg / L, pH 9. At the same time, the red-hot temperature of the steel plate must be controlled at 680℃ during the cooling process. After cooling, the steel plate is obtained.

[0040] Example 9 Except for replacing step S3 with the step S3 described below, the rest is the same as in Example 4; S3. The heated steel billet is hot-rolled, with the finishing rolling temperature controlled at 820℃. After hot rolling, the steel plate is cooled using laminar flow water. The laminar flow cooling water must meet the following requirements: total hardness 350mg / L, chloride ion concentration 220mg / L, pH 6. At the same time, the red-hot temperature of the steel plate must be controlled at 650℃ during the cooling process. After cooling, the steel plate is obtained.

[0041] Example 10 Except for replacing the alkyl glycosides in the scale inhibitor with alkyl glycosides APG0814 and APG1214 in a mass ratio of 7:5, the rest is the same as in Example 1.

[0042] Example 11 Except for replacing the alkyl glycosides in the scale inhibitor with alkyl glycosides APG0814 and APG1214 in a mass ratio of 8:5, the rest is the same as in Example 1.

[0043] Example 12 Except for replacing the alkyl glycosides in the scale inhibitor with alkyl glycosides APG0814 and APG1214 in a mass ratio of 9:5, the rest is the same as in Example 1.

[0044] Example 13 Except for replacing the alkyl glycoside in the scale inhibitor with alkyl glycoside APG1214, the rest is the same as in Example 1.

[0045] Comparative Example 1 Except for replacing step S2 with the step S2 described below, the rest is the same as in Example 1; S2. Heat the steel billet to 550℃ and hold it at an air-fuel ratio of 0.9 for 20 minutes; then heat it to 1100℃ and hold it at an air-fuel ratio of 1.0 for 40 minutes; finally heat it to 1180℃ and hold it at an air-fuel ratio of 1.1 for 20 minutes to obtain the heated steel billet.

[0046] Comparative Example 2 Except for replacing step S2 with the step S2 described below, the rest is the same as in Example 1; S2. Heat the steel billet to 1100℃ and hold it at an air-fuel ratio of 1.0 for 40 minutes; finally, heat it to 1180℃ and hold it at an air-fuel ratio of 1.1 for 20 minutes to obtain the heated steel billet.

[0047] The following performance tests were performed on the steel plates of Examples 1-13 and Comparative Examples 1-2: (1) Iron oxide scale thickness: The iron oxide scale thickness was observed and measured under a metallographic microscope according to the test method specified in GB / T 6462-2005 "Measuring the thickness of metal and oxide coatings by microscopy". Five measuring points were selected for each sample. (2) Adhesion of iron oxide scale to the substrate: After the steel plate production is completed, the sample surface is lightly brushed with a soft brush to observe whether there is any loosening or peeling and to record the iron oxide scale peeling situation; Result judgment criteria: No peeling, that is, there are basically no traces of iron oxide scale peeling on the surface, and no dust is peeled off when the soft brush is lightly brushed; Slight peeling, that is, a small amount of iron oxide scale peeling off locally on the surface, the peeling area accounts for ≤5% of the total sample area, and a small amount of dust is peeled off when the soft brush is lightly brushed; Moderate peeling, that is, iron oxide scale peeling off in many places on the surface, the peeling area accounts for 5%~15% of the total sample area; Severe peeling, that is, a large area of ​​iron oxide scale peeling off on the surface, the peeling area accounts for >15% of the total sample area, or there is a large area of ​​peeling or peeling phenomenon; (3) Corrosion area: The steel plate samples were placed in a simulated storage environment with a temperature of 35℃ and a relative humidity of 85% for 30 days. The presence of obvious red rust and pitting on the sample surface was used as the basis for judgment. The proportion of corrosion area on the sample surface was observed and calculated. The test results are shown in Table 1 below: Table 1. Test results of iron oxide scale thickness, adhesion, and rust area on steel plates.

[0048] Table 1 shows that by adopting a segmented heating process, the steel billet is first heated to 550-600℃ and held for 20-30 minutes at an air-fuel ratio of 1.1-1.3; then heated to 1100-1150℃ and held for 40-60 minutes at an air-fuel ratio of 1.0-1.1; finally heated to 1180-1220℃ and held for 20-30 minutes at an air-fuel ratio of 0.9-1.0, thus completing the billet heating. Simultaneously controlling the final rolling temperature to 780-820℃, the reheating temperature to 580-620℃, and controlling the total hardness of the cooling water to ≤500mg / L and the chloride ion concentration to ≤200mg / L, results in a steel plate with a moderate thickness of iron oxide scale, a dense and complete microstructure, and strong adhesion to the substrate, thereby improving its corrosion resistance.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the rust-resistant iron oxide scale on the surface of hot-rolled steel plates, characterized in that, Includes the following steps: S1. Molten steel is smelted and cast into steel billets; S2. The steel billet is heated to 550~600℃ and held at an air-fuel ratio of 1.1~1.3 for 20~30 minutes; then the temperature is raised to 1100~1150℃ and held at an air-fuel ratio of 1.0~1.1 for 40~60 minutes; finally, the temperature is raised to 1180~1220℃ and held at an air-fuel ratio of 0.9~1.0 for 20~30 minutes to obtain the heated steel billet. S3. The heated steel billet is hot-rolled and then cooled to obtain a steel plate.

2. The method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 1, characterized in that, The molten steel, by mass percentage, consists of the following components: C 0.15%~0.17%, Si 0.15%~0.25%, Mn 1.30%~1.40%, P≤0.025%, S≤0.020%, Alt 0.025%~0.050%, with the balance being Fe and unavoidable impurity elements.

3. The method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 1, characterized in that, During the hot rolling process, the finishing rolling temperature is 780~820℃.

4. The method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 1, characterized in that, During the cooling process, the steel plate's red-hot temperature is 590~610℃.

5. The method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 1, characterized in that, The cooling process employs laminar flow cooling using an aqueous solution of scale inhibitor, wherein the total hardness of the water in the scale inhibitor aqueous solution is ≤500mg / L and the chloride ion concentration is ≤200mg / L.

6. The method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 5, characterized in that, The pH of the water in the scale inhibitor aqueous solution is 7.0~8.

0.

7. The method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 5, characterized in that, The scale inhibitor is added at a concentration of 40-60 mg / L in the aqueous solution.

8. The method for controlling rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 7, characterized in that, The scale inhibitor comprises the following raw materials in parts by weight: 6-10 parts of hydroxyethylidene diphosphonic acid, 6-10 parts of polyepoxysuccinic acid, 4-6 parts of polyacrylic acid, 5-8 parts of sodium molybdate, 2-3 parts of sodium tungstate, 2-4 parts of methylbenzotriazole, 3-5 parts of sodium dodecylbenzenesulfonate, 6-8 parts of alkyl glycoside, 1-2 parts of sodium citrate, and 260-340 parts of water.

9. The method for controlling the rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 8, characterized in that, The alkyl glycosides include alkyl glycoside APG0814 and alkyl glycoside APG1214.

10. The method for controlling the rust-resistant iron oxide scale on the surface of hot-rolled steel plates according to claim 9, characterized in that, The mass ratio of the alkyl glycoside APG0814 to the alkyl glycoside APG1214 is 7~9:5.

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