Deformation-resistant high-strength steel bar and preparation method thereof

Abstract

The invention relates to a deformation-resistant high-strength steel bar and a preparation method thereof.The preparation method comprises the following steps that S1, molten steel is provided, and the molten steel contains a silicon element; s2, the molten steel is subjected to continuous casting, hot rolling and cooling in sequence, and a steel bar blank is obtained; s3, spreading FeCoCrNi high-entropy alloy powder on the surface of the steel bar blank, and adopting laser cladding to enable the FeCoCrNi high-entropy alloy powder to form a high-entropy alloy coating on the surface of the steel bar blank to obtain a steel bar coarse material; and S4, performing shape processing on the steel bar coarse material to obtain a steel bar finished product. Compared with the prior art, the prepared steel bar has good plasticity and toughness on the basis of high strength, and can bear large deformation without breakage.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials and relates to a deformation-resistant high-strength steel bar and a preparation method thereof. Background Art

[0002] In construction projects, steel bars are indispensable materials in building structures, and their performance directly affects the safety and durability of buildings. Although the common steel bars on the market currently meet the construction requirements to a certain extent, there are still deficiencies in high strength and deformation resistance. With the development of modern buildings towards high-rise and large-scale, higher requirements are put forward for the strength and deformation resistance of steel bars. In the production process of some existing high-strength steel bars, due to the limitations of the process, their toughness is often insufficient, and brittle fracture and other problems are likely to occur in actual use. Some improved steel bars on the market may be improved in terms of strength or deformation resistance, but it is difficult to simultaneously take into account high strength and good deformation resistance. For example, for some steel bars with increased strength by adding alloying elements, their crystal structure may become more fragile, and the deformation resistance ability decreases instead. Therefore, it is of great practical significance to develop a deformation-resistant high-strength steel bar and its preparation method. Summary of the Invention

[0003] The purpose of the present invention is to provide a deformation-resistant high-strength steel bar and a preparation method thereof to solve the deficiencies of existing steel bars in terms of high strength and deformation resistance.

[0004] The purpose of the present invention can be achieved by the following technical solutions: A preparation method of a deformation-resistant high-strength steel bar includes the following steps: S1. Provide molten steel containing silicon element; S2. Subject the molten steel to continuous casting, hot rolling and cooling in sequence to obtain a steel bar blank; S3. Spread FeCoCrNi high-entropy alloy powder on the surface of the steel bar blank, and use laser cladding to form a high-entropy alloy coating on the surface of the steel bar blank to obtain a rough steel bar; S4. Perform shape processing on the rough steel bar to obtain a finished steel bar.

[0005] In the prior art, the strength and deformation resistance of steel bars are generally improved by adding alloying elements, but there are problems such as high brittleness and easy occurrence of cross-sections. In this technical solution, the toughness of steel bars is effectively improved by adding silicon elements to the molten steel, making up for the deficiencies of steel bars. In addition, in the present invention, a high-entropy alloy coating is formed on the surface of the steel bar blank, and the overall performance can be improved only by surface modification, avoiding the high cost problem of bulk high-entropy alloys. And the Cr element in the high-entropy alloy coating forms a dense passivation film (Cr2O3), and the corrosion rate in NaCl or acidic media is greatly reduced compared with traditional steel bars. At the same time, the addition of Mo element can inhibit high-temperature oxidation.

[0006] Further, in step S1, the molten steel is mainly prepared by melting raw materials such as hot metal, scrap steel, carbon steel or low-alloy steel in a converter or an electric furnace, adjusting the chemical composition, and removing impurities. Among them, the melting temperature is controlled at 1500-1600 °C, and the melting time is 3-5 hours.

[0007] Preferably, the mass ratio of hot metal to scrap steel is 2-4:1.

[0008] In step S2, the specific steps of continuous casting are as follows: injecting the high-temperature molten steel at 1500-1600 °C into the continuous casting machine mold, and forming a steel billet through cooling and solidification.

[0009] In step S2, the specific steps of hot rolling are as follows: heating the steel billet to make it have good plasticity; rolling the steel billet into an intermediate billet with an approximate finished product size through a roughing mill; and then further rolling in a finishing mill group, and rolling the steel billet into the required shape, such as round or ribbed steel bars, through multi-pass deformation. Among them, during the rolling process, the rolling temperature is controlled at 900-1100 °C by computer, the cooling rate is 10-50 °C / s, the grain size is refined to 5-10 μm, the reduction per pass is 20-30%, and the total elongation coefficient is 5-8 to improve the strength.

[0010] Preferably, in step S2, after hot rolling, the following steps are further included: straightening the steel bar blank through a straightening machine to eliminate the bending and waves during the rolling process and ensure that the straightness of the steel bar meets the standard.

[0011] Further, in step S2, the cooling is preferably rapid cooling by spraying water or air cooling.

[0012] Preferably, in step S3, before spreading the FeCoCrNi high-entropy alloy powder on the surface of the steel bar blank, the steel bar blank is first preheated to 200-400 °C. The main function of preheating is to reduce thermal stress and reduce the risk of cracks.

[0013] Preferably, in step S4, before processing the shape of the rough steel bar, the rough steel bar is first annealed.

[0014] Preferably, when annealing treatment is carried out, the annealing temperature is 600 - 700 °C and the annealing time is 1 - 2 hours.

[0015] Preferably, in step S3, the power of the laser cladding is 1200 - 2000 W and the scanning speed is 3 - 8 mm / s.

[0016] Among them, too high a power of laser cladding is likely to cause the molten pool to be too deep or splashing, while too low a power will result in incomplete fusion of the coating. Selecting the scanning speed within the above range can reduce the heat input, lower the residual stress, and avoid uneven cladding layer due to being too fast.

[0017] Furthermore, in step S3, the spot diameter of the laser cladding is 2 - 3 mm, preferably a circular or rectangular spot; the particle size of the FeCoCrNi high - entropy alloy powder is preferably < 60 μm to ensure sufficient wetting of fluidity and the molten pool.

[0018] Preferably, in step S3, the laser cladding is carried out in an oxygen - isolated atmosphere.

[0019] Preferably, oxygen isolation can be achieved by filling argon into the reaction chamber. The flow rate of the filled argon is 15 - 20 L / min.

[0020] Preferably, in step S3, the laser cladding adopts multi - layer cladding, and the thickness of a single - layer cladding is 0.2 - 0.4 mm.

[0021] Preferably, in step S3, the thickness of the high - entropy alloy coating is 1.0 - 2.0 mm.

[0022] Further preferably, the width of the overlapping area during laser cladding is preferably 30 - 50% of the layer thickness.

[0023] In the present invention, the high energy density of the laser cladding enables the high - entropy alloy coating to form a metallurgical bonding interface with the steel bar substrate, effectively preventing interface peeling.

[0024] Preferably, the silicon element is selected from elemental silicon, ferrosilicon alloy, silicomanganese alloy or silicon - containing compounds.

[0025] Preferably, the silicon - containing compound is silicate or silica sol.

[0026] Furthermore, the mass percentage of the silicon element in the molten steel is 0.5 - 1%. The silicon element in the molten steel can not only effectively deoxidize, but also improve the matrix strength through solid - solution strengthening, and at the same time reduce the segregation risk of the manganese element.

[0027] In the present invention, ferrosilicon powder or ferrosilicon-aluminum mixed powder can be loaded into a waste steel pipe, and both ends are sealed with wooden plugs; during the tapping process, an alloy rod is put in, which sinks below the steel slag interface, and after the steel pipe melts, the ferrosilicon powder is evenly dissolved under the impact of the steel flow and bottom blowing stirring, so as to add silicon element into the molten steel. Or, ferrosilicon powder or silica can be added during the hot metal pretreatment stage by mechanical stirring (KR method) to add silicon element. Or, ferrosilicon powder can also be sprayed into the hot metal ladle through a spray gun to add silicon element.

[0028] A deformation-resistant high-strength steel bar is prepared by the above preparation method.

[0029] The beneficial effects of the present invention: (1) In the preparation of the steel bar of the present invention, the FeCoCrNi high-entropy alloy powder forms a simple solid solution phase through the synergistic effect of multiple main elements, and significant lattice distortion and solid solution strengthening effects are generated during the laser cladding process, significantly improving the hardness of the coating; at the same time, combined with the laser cladding process, silicon element can form a gradient composite structure of the matrix and the coating, avoiding the brittleness problem caused by too high carbon content in traditional high-strength steel bars. Therefore, the steel bar prepared by the present invention has good plasticity and toughness on the basis of high strength, and can withstand large deformation without fracture.

[0030] (2) Through innovative designs such as optimizing the molten steel composition, controlling rolling and controlled cooling to refine grains, and laser cladding coating of high-entropy alloy, the present invention realizes the coordinated improvement of high strength, deformation resistance, corrosion resistance and low-cost preparation. Specific embodiments

[0031] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following takes examples to illustrate in detail the specific embodiments, structures, features and their effects according to the present invention.

[0032] Specifically, the FeCoCrNi high-entropy alloy powder used in this embodiment and the comparative example is purchased from Beijing Ruichi High-Tech Co., Ltd. The ferrosilicon alloy is purchased from Tianjin Zhuxin Metal Materials Co., Ltd. The silicomanganese alloy is purchased from Dongguan Junfeng Special Steel Co., Ltd.

[0033] Example 1 A preparation method of a deformation-resistant high-strength steel bar includes the following steps: S1. Provide molten steel, and the molten steel contains silicon element; wherein, the molten steel is prepared by melting hot metal and scrap steel in a converter or an electric furnace to remove impurities. Among them, the mass ratio of hot metal to scrap steel is 7:3; the melting temperature is controlled at 1550 ± 20 °C, and the melting time is about 4 hours. Among them, the silicon element is provided by ferrosilicon alloy; the mass percentage of the silicon element in the molten steel is 0.75%.

[0034] S21. Continuous casting: Pour the high-temperature molten steel at 1500 ± 20 °C into the continuous casting machine mold, and form a steel billet through cooling and solidification; S22. Hot rolling: Heat the steel billet to about 1000 ± 20 °C, roll the steel billet into an intermediate billet with an approximate finished product size through a rough rolling mill; then further roll it in the finishing mill group, and roll the steel billet into the required shape through 5 - 6 passes of deformation; S23. Straightening: Straighten the steel bar billet through a straightening machine to eliminate the bending and waves during the rolling process, and ensure that the straightness of the steel bar meets the standard; S24. Cooling: Water-cool at a rate of 30 °C / s to 500 ± 20 °C, and then air-cool to room temperature; S3. Under an argon atmosphere, first preheat the steel bar billet to 300 °C, then spread FeCoCrNi high-entropy alloy powder on the surface of the steel bar billet, and use multi-layer laser cladding. The power of the laser cladding is 1500 ± 20 W, and the scanning speed is 6 mm / s, so that the FeCoCrNi high-entropy alloy powder forms a high-entropy alloy coating on the surface of the steel bar billet. The thickness of a single-layer cladding is 0.2 - 0.4 mm, and the total thickness of the coating is 1.0 - 2.0 mm; obtain the rough steel bar; S4. Anneal the rough steel bar, the annealing temperature is 650 °C, and the annealing time is 2 hours; then process the shape of the rough steel bar to obtain the finished steel bar.

[0035] Example 2 A method for preparing a deformation-resistant high-strength steel bar, comprising the following steps: S1. Provide molten steel, and the molten steel contains silicon element; wherein, the molten steel is made by melting pig iron and scrap steel in a converter or an electric furnace to remove impurities. Among them, the mass ratio of pig iron to scrap steel is 3:1; control the melting temperature to be 1500 ± 20 °C, and the melting time is about 4 hours. Among them, the silicon element is provided by ferrosilicon alloy; the mass percentage of the silicon element in the molten steel is 0.5%.

[0036] S21. Continuous casting: Pour the high-temperature molten steel at 1500 ± 20 °C into the continuous casting machine mold, and form a steel billet through cooling and solidification; S22. Hot rolling: Heat the steel billet to 900 ± 20 °C, roll the steel billet into an intermediate billet with an approximate finished product size through a rough rolling mill; then further roll it in the finishing mill group, and roll the steel billet into the required shape through 5 - 6 passes of deformation; S23. Straightening: Straighten the steel bar billet through a straightening machine to eliminate the bending and waves during the rolling process, and ensure that the straightness of the steel bar meets the standard; S24. Cooling: Pass in cold air, air-cool at a rate of 10 °C / s to 500 ± 20 °C, and then air-cool to room temperature; S3. Under an argon atmosphere, first preheat the steel bar blank to 200 ± 20 °C, then spread FeCoCrNi high-entropy alloy powder on the surface of the steel bar blank, and use multi-layer laser cladding. The power of the laser cladding is 1500 ± 20 W, and the scanning speed is 5 mm / s, so that the FeCoCrNi high-entropy alloy powder forms a high-entropy alloy coating on the surface of the steel bar blank. The thickness of a single-layer cladding is 0.2 - 0.4 mm, and the total thickness of the coating is 1.0 - 2.0 mm; obtain the rough steel bar; S4. Perform annealing treatment on the rough steel bar, the annealing temperature is 600 °C, and the annealing time is 2 hours; then perform shape processing on the rough steel bar to obtain the finished steel bar.

[0037] Example 3 A method for preparing a deformation-resistant high-strength steel bar, comprising the following steps: S1. Provide molten steel, and the molten steel contains silicon element; wherein, the molten steel is prepared by smelting molten iron and scrap steel in a converter or an electric furnace to remove impurities. Among them, the mass ratio of molten iron to scrap steel is 4:1; control the smelting temperature to be 1600 ± 20 °C, and the smelting time is about 4 hours. Among them, the silicon element is provided by ferrosilicon manganese alloy; the mass percentage of the silicon element in the molten steel is 1%.

[0038] S21. Continuous casting: Inject the high-temperature molten steel at 1600 ± 20 °C into the continuous casting machine mold, and form a steel billet through cooling and solidification; S22. Hot rolling: Heat the steel billet to 1100 ± 20 °C, and roll the steel billet into an intermediate billet with an approximate finished product size through a rough rolling mill; then further roll it in a finishing mill group, and roll the steel billet into the required shape through 5 - 6 passes of deformation; S23. Straightening: Straighten the steel bar blank through a straightening machine to eliminate the bending and waves during the rolling process, and ensure that the straightness of the steel bar meets the standard; S24. Cooling: Cool it to 500 ± 20 °C at a rate of 50 °C / s by water cooling, and then air-cool it to room temperature; S3. Under an argon atmosphere, first preheat the steel bar blank to 400 ± 20 °C, then spread FeCoCrNi high-entropy alloy powder on the surface of the steel bar blank, and use multi-layer laser cladding. The power of the laser cladding is 1500 ± 20 W, and the scanning speed is 5 mm / s, so that the FeCoCrNi high-entropy alloy powder forms a high-entropy alloy coating on the surface of the steel bar blank. The thickness of a single-layer cladding is 0.2 - 0.4 mm, and the total thickness of the coating is 1.0 - 2.0 mm; obtain the rough steel bar; S4. Perform annealing treatment on the rough steel bar, the annealing temperature is 700 °C, and the annealing time is 1 hour; then perform shape processing on the rough steel bar to obtain the finished steel bar.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that in step S1 of this comparative example, no additional silicon element was added to the molten steel.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that in step S3 of this comparative example, the FeCoCrNi high-entropy alloy powder was replaced with FeCrAl high-entropy alloy powder, purchased from Beijing Ruichi High-Tech Co., Ltd.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that in step S3 of this comparative example, the FeCoCrNi high-entropy alloy powder was replaced with FeCoNi high-entropy alloy powder, purchased from Beijing Ruichi High-Tech Co., Ltd.

[0042] Comparative Example 4 The difference between this comparative example and Example 1 is that in step S3 of this comparative example, the FeCoCrNi high-entropy alloy powder was replaced with FeCrNi high-entropy alloy powder, purchased from Shanghai Yanbei New Materials Technology Co., Ltd.

[0043] Comparative Example 5 The difference between this comparative example and Example 1 is that in step S3 of this comparative example, the FeCoCrNi high-entropy alloy powder was replaced with CoCrNi high-entropy alloy powder, purchased from Beijing Ruichi High-Tech Co., Ltd.

[0044] Mechanical Property Testing Referring to "GB / T1499.2-2024 Steel for Reinforced Concrete Part 2: Hot Rolled Ribbed Bars" and "GB / T228.1-2021 Metallic Materials - Tensile Testing", the yield strength (ReL), tensile strength (Rm), elongation after fracture (A), and strength ratio (Rm / ReL) of the steel bar products in Examples 1-3 and Comparative Examples 1-5 were tested.

[0045] Testing Method: Non-turning machined specimens were used, and room temperature tensile tests were carried out according to GB / T228.1. The nominal cross-sectional area should be used when calculating the cross-sectional area.

[0046] Charpy Impact Test (V-notch) Testing Method: The specimen with a prefabricated notch was impacted by a pendulum hammer to measure the absorbed energy of fracture (KV2).

[0047] The test results are shown in Table 1: Table 1 Specimen Yield strength (MPa) Tensile strength (MPa) Ratio of tensile strength to yield strength (Rm / ReL) Elongation after fracture (%) Absorbed energy at fracture (J) Example 1 853 1123 1.32 19 62 Example 2 794 1097 1.38 18 58 Example 3 946 1210 1.28 20 57 Comparative Example 1 593 688 1.16 16 34 Comparative Example 2 574 674 1.17 15 49 Comparative Example 3 619 708 1.14 15 41 Comparative Example 4 528 685 1.30 14 45 Comparative Example 5 570 725 1.27 16 40 From the test results in Table 1, it can be seen that the data of yield strength, tensile strength, elongation after fracture, and fracture energy absorption of Examples 1-3 are all better than those measured in Comparative Examples 1-5. It can be deduced therefrom that the steel bars obtained by the present invention have better performance by adding silicon element to the molten steel and setting a high-entropy alloy coating on the surface of the steel bar billets. Specifically, the steel bars in the comparative examples lack silicon element, and their fracture energy absorption is significantly lower than that of other steel bars, indicating that the addition of silicon element is beneficial to improving the toughness of the steel bars.

[0048] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a deformation-resistant high-strength steel bar, characterized in that, It includes the following steps: S1. Provide molten steel containing silicon element; S2. Subject the molten steel to continuous casting, hot rolling and cooling successively to obtain a reinforcing bar blank; S3. Spread FeCoCrNi high-entropy alloy powder on the surface of the reinforcing bar blank, and use laser cladding to form a high-entropy alloy coating on the surface of the reinforcing bar blank to obtain a rough reinforcing bar; S4. Perform shape processing on the rough reinforcing bar to obtain a finished reinforcing bar.

2. The preparation method according to claim 1, characterized in that, In step S3, before spreading FeCoCrNi high-entropy alloy powder on the surface of the reinforcing bar blank, preheat the reinforcing bar blank to 200-400 °C first.

3. The preparation method according to claim 1, characterized in that, In step S4, before performing shape processing on the rough reinforcing bar, perform annealing treatment on the rough reinforcing bar first.

4. The preparation method according to claim 3, characterized in that, When performing annealing treatment, the annealing temperature is 600-700 °C and the annealing time is 1-2 hours.

5. The preparation method according to claim 1, wherein, In step S3, the power of the laser cladding is 1200-2000 W and the scanning speed is 3-8 mm / s.

6. The preparation method according to claim 1, characterized in that, In step S3, the laser cladding is carried out in an oxygen-isolated atmosphere.

7. The preparation method according to claim 1, characterized in that, In step S3, the laser cladding adopts multi-layer cladding, and the thickness of a single-layer cladding is 0.2-0.4 mm.

8. The preparation method according to claim 1, wherein In step S3, the thickness of the high-entropy alloy coating is 1.0-2.0 mm.

9. The preparation method according to claim 1, characterized in that, The silicon element is selected from elemental silicon, ferrosilicon alloy, silicomanganese alloy or silicon-containing compound.

10. A deformation-resistant high-strength steel bar, characterized in that, Prepared by the preparation method according to any one of claims 1-9.