Low-crack high-aluminum steel controlled by gradient heating and rolling and preparation method thereof

Abstract

The application relates to the technical field of steel smelting, and discloses a low-crack high-aluminum steel prepared through gradient heating and controlled rolling and a preparation method thereof.The low-crack high-aluminum steel prepared through gradient heating and controlled rolling is composed of the following components in percentage by weight: C 0.05%-0.08%, Mn 1.5%-1.9%, Si 0.3%-0.5%, Cr 0.5%-0.7%, Mo 0.35%-0.52%, Al 5%-5.5%, P<=0.015%, S<=0.005%, N<=0.03%, and the balance of Fe and inevitable impurities, wherein (Mn+Si):(C+Mo)=4-4.5.The above technical scheme solves the problem of insufficient strength of the high-aluminum steel in the related art.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, specifically to a low-crack high-alumina steel produced by gradient heating controlled rolling and its preparation method. Background Technology

[0002] High-aluminum steel is a type of alloy steel with iron as the base material and aluminum as the key alloying element. It has been widely used in the automotive industry, engineering machinery, marine engineering, rail transportation and other fields.

[0003] However, existing high-alumina steels exhibit insufficient strength in practical applications, partly due to an imbalance in the alloy element ratios and a lack of strengthening effects between alloy elements, failing to construct a composite strengthening system. Insufficient strength in high-alumina steel can lead to a series of serious hazards. When used as load-bearing components, insufficient strength can cause plastic deformation and creep failure during service, severely impacting the operational safety and reliability of equipment, and potentially even triggering major safety accidents.

[0004] Therefore, it is necessary to develop a high-aluminum steel with high strength. Summary of the Invention

[0005] This invention proposes a low-crack high-alumina steel produced by gradient heating controlled rolling and its preparation method, which solves the problem of insufficient strength of high-alumina steel in related technologies.

[0006] The technical solution of the present invention is as follows: The present invention proposes a low-crack high-alumina steel produced by gradient heating controlled rolling, which, by weight percentage, consists of the following components: C 0.05%~0.08%, Mn 1.5%~1.9%, Si 0.3%~0.5%, Cr 0.5%~0.7%, Mo 0.35%~0.52%, Al 5%~5.5%, P≤0.015%, S≤0.005%, N≤0.03%, with the balance being Fe and unavoidable impurities, wherein (Mn+Si):(C+Mo)=4~4.5.

[0007] This invention also proposes a method for preparing low-crack high-alumina steel by gradient heating controlled rolling, which includes the following steps: S1. After smelting, refining and continuous casting according to the stated ingredients, a billet is obtained; S2. The cast billet is rolled and then heat-treated to obtain the low-crack high-alumina steel produced by gradient heating controlled rolling.

[0008] As a further technical solution, the rolling is gradient heating rolling, which includes the following steps: the billet is gradient heated, and after hot rolling, it is cooled to room temperature to obtain a hot-rolled plate. The hot-rolled plate is then subjected to solution treatment and cold rolling to obtain a cold-rolled plate.

[0009] As a further technical solution, the gradient heating of the billet includes the following steps: the billet is first heated to 720-750℃ at a rate of 6-8℃ / min, and then heated to 1180-1200℃ at a rate of 3-4℃ / min, and held at that temperature for 1-1.5h.

[0010] As a further technical solution, the initial rolling temperature of the hot rolling is 1120~1140℃, and the final rolling temperature of the hot rolling is 950~980℃.

[0011] As a further technical solution, the cooling method is water cooling.

[0012] As a further technical solution, the solution treatment includes the following steps: heating the hot-rolled plate to 1000~1100℃, holding it at that temperature for 1~2 hours, and then quenching and cooling it to room temperature.

[0013] As a further technical solution, the heat treatment includes the following steps: heating the cold-rolled plate to 980~1000℃, holding it at that temperature for 10~15 minutes, and then cooling it to room temperature to obtain the low-crack high-aluminum steel produced by gradient heating controlled rolling.

[0014] As a further technical solution, the quenching and cooling includes the following steps: after the hot-rolled plate is heated and kept at a certain temperature, a first stage of quenching and cooling is performed to cool to 450~550℃, and then a second stage of quenching and cooling is performed to cool to room temperature. The media used for the first stage of quenching and cooling and the second stage of quenching and cooling are different.

[0015] As a further technical solution, the medium for the first stage of quenching and cooling is water, and the medium for the second stage of quenching and cooling is a polyvinyl alcohol aqueous solution, wherein the concentration of the polyvinyl alcohol aqueous solution is 5wt%~8wt%, and the viscosity of the polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5.2~6.0mPa.s.

[0016] In the preparation process of the high-alumina steel of this invention, a combination of water quenching and polyvinyl alcohol aqueous solution quenching is adopted. The first stage of water quenching can quickly suppress grain growth, effectively suppress the growth of austenite grains and the precipitation of proeutectoid ferrite, and retain fine supersaturated austenite structure, creating conditions for subsequent phase transformation to refine the structure. The second stage of slow cooling of polyvinyl alcohol aqueous solution can optimize the phase transformation structure. The moderate cooling rate of polyvinyl alcohol aqueous solution promotes the formation of fine and uniform pearlite and ferrite structure, achieving a balance between strength and toughness.

[0017] The working principle and beneficial effects of this invention are as follows: The high-alumina steel of this invention utilizes adjusted core alloying element content and proportions to fully leverage various strengthening mechanisms and create a synergistic effect, thereby enhancing the strength of the high-alumina steel. Specifically, the Al content is 5%~5.5%, which forms a stable solid solution in the iron matrix. This avoids the problems of insufficient solid solution strengthening and loose oxide film formation caused by excessively low Al content, while overcoming the defects of excessively high Al content leading to the formation of coarse intermetallic compounds and inclusions. Controlling the (Mn+Si):(C+Mo) ratio within the range of 4~4.5 allows for the formation of numerous fine and dispersed carbides in the matrix, avoiding the agglomeration of coarse carbides due to excessive Mo or the waste of Mo due to insufficient C. This strengthens the matrix while preventing toughness degradation, achieving a balance between solid solution strengthening and toughness, and effectively improving the strength of the high-alumina steel. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise specified, the following embodiments and comparative examples are as follows: Polyvinyl alcohol aqueous solution: concentration of 8wt%, viscosity of polyvinyl alcohol is 5.2~6.0mPa.s.

[0020] Example 1 A method for preparing low-crack high-alumina steel by gradient heating controlled rolling includes the following steps: S1. According to the ingredients, after smelting, refining and continuous casting, a billet is obtained; S2. The billet is first heated to 720℃ at a rate of 6℃ / min, then heated to 1180℃ at a rate of 3℃ / min. After holding at this temperature for 1.5h, it is hot rolled at 1120℃, and the final rolling temperature is 950℃. After water cooling to room temperature, a hot-rolled plate is obtained. The hot-rolled plate is heated to 1000℃ and held for 2h, then water quenched and cooled to room temperature. After cold rolling, a cold-rolled plate is obtained. The cold-rolled plate is heated to 980℃, held for 15min, and water cooled to room temperature to obtain low-crack high-alumina steel rolled by gradient heating control. A low-crack high-alumina steel produced by gradient heating controlled rolling, comprising the following components by weight percentage: C 0.05%, Mn 1.5%, Si 0.3%, Cr 0.5%, Mo 0.35%, Al 5%, P 0.011%, S 0.003%, N 0.03%, with the balance being Fe and unavoidable impurities.

[0021] Example 2 A method for preparing low-crack high-alumina steel by gradient heating controlled rolling includes the following steps: S1. According to the ingredients, after smelting, refining and continuous casting, a billet is obtained; S2. The billet is first heated to 735℃ at a rate of 7℃ / min, then heated to 1190℃ at a rate of 4℃ / min. After holding at this temperature for 1.2h, it is hot rolled at 1130℃, and the final rolling temperature is 960℃. After water cooling to room temperature, a hot-rolled plate is obtained. The hot-rolled plate is heated to 1050℃ and held for 1.5h, then water quenched and cooled to room temperature. After cold rolling, a cold-rolled plate is obtained. The cold-rolled plate is heated to 990℃, held for 12min, and then water cooled to room temperature to obtain low-crack high-alumina steel rolled by gradient heating control. A low-crack high-alumina steel produced by gradient heating controlled rolling, comprising the following components by weight percentage: C 0.06%, Mn 1.7%, Si 0.4%, Cr 0.6%, Mo 0.45%, Al 5.3%, P 0.010%, S 0.002%, N 0.02%, with the balance being Fe and unavoidable impurities.

[0022] Example 3 A method for preparing low-crack high-alumina steel by gradient heating controlled rolling includes the following steps: S1. According to the ingredients, after smelting, refining and continuous casting, a billet is obtained; S2. The billet is first heated to 750℃ at a rate of 8℃ / min, then heated to 1200℃ at a rate of 4℃ / min. After holding at this temperature for 1 hour, it is hot rolled at 1140℃, and the final rolling temperature is 980℃. After water cooling to room temperature, a hot-rolled plate is obtained. The hot-rolled plate is heated to 1100℃ and held for 1 hour, then water quenched and cooled to room temperature. After cold rolling, a cold-rolled plate is obtained. The cold-rolled plate is heated to 1000℃, held for 10 minutes, and then water cooled to room temperature to obtain low-crack high-alumina steel rolled by gradient heating control. A low-crack high-alumina steel produced by gradient heating controlled rolling, comprising the following components by weight percentage: C 0.08%, Mn 1.9%, Si 0.5%, Cr 0.7%, Mo 0.52%, Al 5.5%, P 0.010%, S 0.002%, N 0.02%, with the balance being Fe and unavoidable impurities.

[0023] Example 4 Compared with Example 2, Example 4 differs in that, in this example, the preparation method of low-crack high-alumina steel by gradient heating controlled rolling includes the following steps in step S2: the billet is first heated to 735°C at a rate of 10°C / min, then heated to 1190°C at a rate of 6°C / min, held for 1.2 hours, then hot-rolled at 1130°C, with a final rolling temperature of 960°C. After water cooling to room temperature, a hot-rolled plate is obtained. The hot-rolled plate is then heated to 1050°C and held for 1.5 hours, then water-quenched and cooled to room temperature. After cold rolling, a cold-rolled plate is obtained. The cold-rolled plate is then heated to 990°C, held for 12 minutes, and water-cooled to room temperature to obtain low-crack high-alumina steel by gradient heating controlled rolling.

[0024] Example 5 Compared with Example 2, Example 5 differs in that, in this example, the preparation method of low-crack high-alumina steel by gradient heating controlled rolling includes the following steps in step S2: the billet is first heated to 735°C at a rate of 5°C / min, then heated to 1190°C at a rate of 2°C / min, held for 1.2 hours, then hot-rolled at 1130°C, with a final rolling temperature of 960°C. After water cooling to room temperature, a hot-rolled plate is obtained. The hot-rolled plate is then heated to 1050°C and held for 1.5 hours, then water-quenched and cooled to room temperature. After cold rolling, a cold-rolled plate is obtained. The cold-rolled plate is then heated to 990°C, held for 12 minutes, and water-cooled to room temperature to obtain low-crack high-alumina steel by gradient heating controlled rolling.

[0025] Example 6 Compared with Example 2, Example 6 differs in that, in this example, the preparation method of low-crack high-alumina steel by gradient heating controlled rolling includes the following steps in step S2: the billet is first heated to 735°C at a rate of 7°C / min, then heated to 1190°C at a rate of 4°C / min, held for 1.2 hours, then hot-rolled at 1130°C, with a final rolling temperature of 960°C. After water cooling to room temperature, a hot-rolled plate is obtained. The hot-rolled plate is then heated to 1050°C and held for 1.5 hours, quenched in a polyvinyl alcohol aqueous solution and cooled to room temperature. After cold rolling, a cold-rolled plate is obtained. The cold-rolled plate is then heated to 990°C, held for 12 minutes, and water-cooled to room temperature to obtain low-crack high-alumina steel by gradient heating controlled rolling.

[0026] Example 7 Compared with Example 2, Example 7 differs in that, in this example, the preparation method of low-crack high-alumina steel by gradient heating controlled rolling includes the following steps in step S2: the billet is first heated to 735°C at a rate of 7°C / min, then heated to 1190°C at a rate of 4°C / min, held for 1.2 hours, then hot-rolled at 1130°C, with a final rolling temperature of 960°C. After water cooling to room temperature, a hot-rolled plate is obtained. The hot-rolled plate is heated to 1050°C and held for 1.5 hours, then quenched with water to 500°C, and then quenched with a polyvinyl alcohol aqueous solution to room temperature. After cold rolling, a cold-rolled plate is obtained. The cold-rolled plate is heated to 990°C, held for 12 minutes, and then water-cooled to room temperature to obtain low-crack high-alumina steel by gradient heating controlled rolling.

[0027] Example 8 Compared with Example 2, Example 8 differs in that, in this example, the preparation method of low-crack high-alumina steel by gradient heating controlled rolling includes the following steps in step S2: the billet is first heated to 735°C at a rate of 7°C / min, then heated to 1190°C at a rate of 4°C / min, held for 1.2 hours, then hot-rolled at 1130°C, with a final rolling temperature of 960°C. After water cooling to room temperature, a hot-rolled plate is obtained. The hot-rolled plate is heated to 1050°C and held for 1.5 hours, then quenched to 500°C using a polyvinyl alcohol aqueous solution, and then quenched to room temperature using water. After cold rolling, a cold-rolled plate is obtained. The cold-rolled plate is heated to 990°C, held for 12 minutes, and then water-cooled to room temperature to obtain low-crack high-alumina steel by gradient heating controlled rolling.

[0028] Example 9 The difference between Example 9 and Example 7 is that the polyvinyl alcohol aqueous solution with a concentration of 8 wt% and a viscosity of 5.2~6.0 mPa·s was replaced with a polyvinyl alcohol aqueous solution of the same concentration and a viscosity of 12~16 mPa·s.

[0029] Example 10 Compared with Example 7, Example 10 differs in that the polyvinyl alcohol aqueous solution with a concentration of 8 wt% and a viscosity of 5.2~6.0 mPa·s is replaced with a polyvinyl alcohol aqueous solution of the same concentration with a viscosity of 3.2~3.8 mPa·s.

[0030] Comparative Example 1 Compared with Example 2, Comparative Example 1 differs in that the low-crack high-alumina steel rolled by gradient heating in this comparative example is composed of the following components by weight percentage: C 0.06%, Mn 1.4%, Si 0.4%, Cr 0.6%, Mo 0.45%, Al 5.3%, P 0.010%, S 0.002%, N 0.02%, with the balance being Fe and unavoidable impurities.

[0031] Comparative Example 2 Compared with Example 2, Comparative Example 2 differs in that the low-crack high-alumina steel rolled by gradient heating in this comparative example is composed of the following components by weight percentage: C 0.06%, Mn 2.0%, Si 0.4%, Cr 0.6%, Mo 0.45%, Al 5.3%, P 0.010%, S 0.002%, N 0.02%, with the balance being Fe and unavoidable impurities.

[0032] Comparative Example 3 Compared with Example 2, Comparative Example 3 differs in that the low-crack high-alumina steel rolled by gradient heating in this comparative example is composed of the following components by weight percentage: C 0.06%, Mn 1.7%, Si 0.4%, Cr 0.6%, Mo 0.45%, Al 3%, P 0.010%, S 0.002%, N 0.02%, with the balance being Fe and unavoidable impurities.

[0033] Comparative Example 4 Compared with Example 2, Comparative Example 4 differs in that the low-crack high-alumina steel rolled by gradient heating in this comparative example is composed of the following components by weight percentage: C 0.06%, Mn 1.7%, Si 0.4%, Cr 0.6%, Mo 0.45%, Al 7%, P 0.010%, S 0.002%, N 0.02%, with the balance being Fe and unavoidable impurities.

[0034] Experimental Example 1 The tensile strength of the high-alumina steels prepared in Examples 1-10 and Comparative Examples 1-4 was tested according to the test methods specified in GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature".

[0035] The test results are shown in Table 1: Table 1 Performance test results of Examples 1-10 and Comparative Examples 1-4

[0036] As shown in Table 1, when the composition of high-alumina steel meets the specified range and (Mn+Si):(C+Mo)=4~4.5, the strength of high-alumina steel can be improved. When gradient heating rolling is used, the strength of high-alumina steel can be further improved. In the solution treatment process, when water quenching and cooling are used first, and then polyvinyl alcohol aqueous solution quenching and cooling are used, the tensile strength of the obtained high-alumina steel is higher.

[0037] The high-alumina steel prepared in Example 2 of this invention has no visible defects such as cracks, scratches, scabs, folds, ears, or inclusions when observed by visual inspection.

[0038] 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 low-crack, high-alumina steel produced by gradient heating controlled rolling, characterized in that, By weight percentage, it consists of the following components: C 0.05%~0.08%, Mn 1.5%~1.9%, Si 0.3%~0.5%, Cr 0.5%~0.7%, Mo 0.35%~0.52%, Al 5%~5.5%, P≤0.015%, S≤0.005%, N≤0.03%, with the balance being Fe and unavoidable impurities, wherein (Mn+Si):(C+Mo)=4~4.5; The method for preparing low-crack high-alumina steel by gradient heating controlled rolling includes the following steps: S1. After smelting, refining and continuous casting according to the stated ingredients, a billet is obtained; S2. The cast billet is rolled and then heat-treated to obtain the low-crack high-aluminum steel produced by gradient heating controlled rolling. The rolling process is gradient heating rolling, which includes the following steps: the billet is gradient heated, hot rolled and then cooled to room temperature to obtain a hot-rolled plate, and the hot-rolled plate is subjected to solution treatment and cold rolling to obtain a cold-rolled plate; The gradient heating of the billet includes the following steps: the billet is first heated to 720-750°C at a rate of 6-8°C / min, and then heated to 1180-1200°C at a rate of 3-4°C / min, and held at that temperature for 1-1.5 hours. The solution treatment includes the following steps: heating the hot-rolled plate to 1000~1100℃, holding it at that temperature for 1~2 hours, and then quenching and cooling it to room temperature; The quenching and cooling process includes the following steps: after the hot-rolled plate is heated and kept at a certain temperature, it undergoes a first stage of quenching and cooling to 450~550℃, and then undergoes a second stage of quenching and cooling to room temperature. The media used for the first stage of quenching and cooling and the second stage of quenching and cooling are different. The medium for the first stage of quenching and cooling is water, and the medium for the second stage of quenching and cooling is an aqueous solution of polyvinyl alcohol, wherein the concentration of the aqueous solution of polyvinyl alcohol is 5wt%~8wt%, and the viscosity of polyvinyl alcohol in the aqueous solution of polyvinyl alcohol is 5.2~6.0 mPa·s.

2. A method for preparing low-crack high-alumina steel by gradient heating controlled rolling, used to prepare the low-crack high-alumina steel by gradient heating controlled rolling as described in claim 1, characterized in that, Includes the following steps: S1. After smelting, refining and continuous casting according to the stated ingredients, a billet is obtained; S2. The cast billet is rolled and then heat-treated to obtain the low-crack high-alumina steel produced by gradient heating controlled rolling.

3. The low-crack high-alumina steel produced by gradient heating controlled rolling according to claim 1, characterized in that, The initial rolling temperature of the hot rolling is 1120~1140℃, and the final rolling temperature of the hot rolling is 950~980℃.

4. The low-crack high-alumina steel produced by gradient heating controlled rolling according to claim 1, characterized in that, The cooling method is water cooling.

5. The low-crack high-alumina steel produced by gradient heating controlled rolling according to claim 1, characterized in that, The heat treatment includes the following steps: heating the cold-rolled sheet to 980~1000℃, holding it at that temperature for 10~15 minutes, and then cooling it to room temperature to obtain the low-crack high-aluminum steel produced by gradient heating controlled rolling.

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