Wear-resistant flat steel and production method thereof

Abstract

The invention belongs to the technical field of metallurgy, and relates to wear-resistant flat steel and a production method thereof. The steel comprises the following chemical components in percentage by weight: 0.40 percent to 0.50 percent of C, 0.20 percent to 0.40 percent of Si, 0.60 percent to 0.80 percent of Mn, less than or equal to 0.012 percent of P, less than or equal to 0.012 percent of S, 0.50 percent to 1.00 percent of Cr, 0.10 percent to 0.20 percent of Mo, 0.050 percent to 0.080 percent of Al, 0.0010 percent to 0.0020 percent of B, 1.40 percent to 1.80 percent of Ni and the balance of Fe and inevitable impurities. H removal control is enhanced in the smelting process, and the superheat degree, the pulling speed and tail end electromagnetic stirring parameters are reasonably optimized in the continuous casting process to reduce casting blank macroscopic defects. In the rolling process, the structure is homogenized through the high-temperature diffusion technology, the brittle structure of the material is reduced through the slow cooling technology, and finally the comprehensive performance of the material is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology and relates to a wear-resistant flat steel and its production method. Background Technology

[0002] With the development of China's construction machinery industry, there is a growing demand for high wear-resistant materials to replace easily worn materials. The original wear-resistant materials for construction machinery were mainly made by fire-cutting sheet metal and then machining it. This method is inefficient, time-consuming, and costly. Therefore, it is crucial to develop a new type of wear-resistant material to replace the original method of fire-cutting and machining sheet metal. Summary of the Invention

[0003] To achieve the above objectives, this invention provides a wear-resistant flat steel and its production method. It employs higher levels of Mn and Cr to enhance material strength, adds appropriate amounts of Al to refine grains, reduces P and S content while increasing Ni content to improve toughness, and increases B content to enhance hardenability. The smelting process strengthens H removal control, and the continuous casting process reduces low-magnification defects in the billet through reasonable optimization of superheat, casting speed, and end-stage electromagnetic stirring parameters. The rolling process uses a high-temperature diffusion process to homogenize the microstructure and a slow cooling process to reduce brittle microstructure, ultimately resulting in a significant improvement in the overall performance of the material. The aforementioned wear-resistant flat steel is suitable for manufacturing rectangular wear-resistant strips for engineering machinery with a thickness of 20-40mm and a width of 60-100mm. While maintaining good weldability, it possesses high strength, high toughness, and high wear resistance. After heat treatment, its tensile strength exceeds 1800MPa, its KV2 impact toughness at -20℃ is ≥30J, and its Rockwell hardness is 55-60HRC. This successfully yields wear-resistant strips for engineering machinery that meet high wear resistance requirements, eliminating the need for fire cutting and machining processes, and significantly improving material quality, thus solving problems existing in the prior art.

[0004] The technical solution adopted in this invention is a wear-resistant flat steel with the following chemical composition by weight percentage: C: 0.40%–0.50%, Si: 0.20%–0.40%, Mn: 0.60%–0.80%, P≤0.012%, S≤0.012%, Cr: 0.50%–1.00%, Mo: 0.10%–0.20%, Al: 0.050%–0.080%, B: 0.0010%–0.0020%, Ni: 1.40%–1.80%, with the remainder being Fe and unavoidable impurities.

[0005] The present invention also provides a method for producing wear-resistant flat steel, including converter smelting, LF furnace refining, RH vacuum treatment, continuous casting, rolling and slow cooling processes;

[0006] The rolling process involves controlling the heating temperature of the soaking zone to 1220–1250°C, with a reduction rate greater than 60% in the first and second passes; and performing water-controlled rolling with a final rolling temperature of 650–700°C at an ultra-low temperature, resulting in a cumulative reduction rate greater than 80%.

[0007] The slow cooling process involves: strong water cooling after rolling, controlling the temperature of the upper cooling bed at 730-780℃, slow cooling with close-packed cooling beds, controlling the temperature of the material exiting the cooling hood below 500℃, and a slow cooling rate of 0.05℃ / S.

[0008] Furthermore, in the converter smelting process: the ratio of molten iron to scrap steel fed into the converter is controlled at 8:2; during the tapping process, a composite deoxidizer is added to form slag and deoxidize.

[0009] Furthermore, in the LF furnace refining process: the LF basicity is controlled at 6.0 to 8.0. Before the LF furnace refining is completed, aluminum wire is fed to adjust the aluminum in the molten steel to 0.070% to 0.090%. Before leaving the station, calcium wire is fed to treat the molten steel with calcium. The first furnace is poured for 150 meters, the second furnace and subsequent furnaces are poured for 120 meters. Then, a covering agent is added to protect the molten steel.

[0010] Furthermore, the RH vacuum treatment process involves: evacuating the RH pump to below 67 Pa, maintaining the vacuum for 15 minutes, breaking the vacuum to determine the hydrogen content in the molten steel, and controlling the hydrogen content to ≤1.5 ppm. The soft blowing time before leaving the station is 25-35 minutes.

[0011] Furthermore, the continuous casting process employs: weak cooling with a specific water volume of 0.20 L / KG, a target superheat value of 25℃~35℃ in the tundish, fine-tuning the water distribution in each zone through a light-reduction process, and reducing continuous casting segregation by cooperating with the crystallizer and end electromagnetic stirring. The temperature of the center point of the inner arc surface of the billet entering the straightening machine is monitored at 1100~1150℃, the billet size is 280*280*mm*6.0m, and the billet is stacked and cooled for 24 hours.

[0012] Furthermore, the wear-resistant flat steel is suitable for manufacturing rectangular wear-resistant strips for engineering machinery with a thickness of 20-40mm and a width of 60-100mm. The microstructure is composed of sorbite, pearlite, and ferrite as the matrix. After heat treatment, the tensile strength is 1800-2000MPa, the KV2 impact toughness value at -20℃ is ≥30J, and the Rockwell hardness is 55-60HRC.

[0013] The main features and significant effects of this invention are as follows:

[0014] 1. This invention achieves grain refinement and strengthening by increasing the Mn and Cr content in steel, rationally setting the Al content in steel, and improving hardenability by adding trace amounts of B.

[0015] 2. This invention employs a high reduction initial rolling technology, with the reduction rate reaching 60% in the first two passes, thus breaking up the grains.

[0016] 3. This invention uses ultra-low temperature final rolling technology, with the final rolling temperature controlled at 650-700℃, to further refine the grains.

[0017] 4. After rolling, collect the material quickly and allow it to cool slowly. Control the cooling rate between 730-780℃ and 500℃ at 0.05℃ / s to ensure that the original microstructure is free of brittle structures such as bainite.

[0018] 5. This invention utilizes existing equipment and process conditions in steel plants to create processes that meet customer needs without significantly increasing investment and production costs.

[0019] 6. The product of this invention can provide experience for the research and development of high-quality steel to special steel products.

[0020] The beneficial effects of this invention are as follows: This invention adopts a series of new rolling technologies such as smelting composition design, large reduction, controlled rolling and slow cooling, which breaks through the limits of existing materials and processes, gives full play to the advantages of equipment, and produces flat steel with sorbite + pearlite + ferrite as the matrix, with a strength of 1800-2000MPa after heat treatment and a wear-resistant flat steel with a V-shaped strength of more than 30J at low temperature impact (-20℃), thus promoting the research and development process of high-quality high alloy flat steel. Attached Figure Description

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a metallographic image of the flat steel produced in Embodiment 1 of the present invention. Detailed Implementation

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] This invention provides a wear-resistant flat steel and its production method. It utilizes higher levels of Mn and Cr elements to improve material strength, adds an appropriate amount of Al to refine grain size, reduces P and S content and increases Ni content to improve toughness, and increases B content to improve hardenability. Through large reduction and controlled rolling and cooling processes, it fully utilizes fine-grain strengthening and austenite recrystallization during the final rolling stage to refine the original austenite grain size. Simultaneously, it increases the content of low-cost elements, reducing costs while effectively improving the hardenability of the material, thus meeting the requirements for high strength, high toughness, and high wear resistance. The technical solution to the above-mentioned technical problems is a manufacturing method for wear-resistant flat steel. The process route is smelting – continuous casting – hot charging – rolling – controlled cooling – slow cooling – warehousing, which can well meet user requirements.

[0025] The chemical composition of the steel by weight percentage is as follows: C: 0.40%–0.50%, Si: 0.20%–0.40%, Mn: 0.60%–0.80%, P≤0.012%, S≤0.012%, Cr: 0.50%–1.00%, Mo: 0.10%–0.20%, Al: 0.050%–0.080%, B: 0.0010%–0.0020%, Ni: 1.40%–1.80%, with the remainder being Fe and unavoidable impurities.

[0026] The specific production process and technical parameters are as follows:

[0027] (1) Converter smelting: The ratio of molten iron to scrap steel in the converter is controlled at 8:2; a composite deoxidizer is added during the tapping process to form slag and deoxidize.

[0028] (2) LF furnace refining: The basicity of LF is controlled at 6.0 to 8.0. Before the end of LF furnace refining, aluminum wire is fed to adjust the aluminum in the molten steel to 0.070% to 0.090%. Before leaving the station, calcium wire is fed to treat the molten steel with calcium. The amount of calcium wire fed in the first continuous casting is 150 meters, and the amount fed in the second continuous casting and subsequent castings is 120 meters. Then, a covering agent is added to protect the molten steel.

[0029] (3) RH vacuum treatment: RH is evacuated to below 67Pa, and the vacuum is maintained for 15 minutes. After evacuation, the hydrogen content of the molten steel is determined and controlled to be ≤1.5ppm. The soft blowing time before leaving the station is 25 to 35 minutes.

[0030] (4) Continuous casting: Weak cooling is adopted, the specific water volume is 0.20L / KG, the target value of the superheat of the tundish is 25℃~35℃, the water distribution in each zone is finely adjusted by the light pressing process, and the segregation of continuous casting is reduced by the crystallizer and the end electromagnetic stirring. The temperature of the center point of the inner arc surface of the billet entering the straightening machine is monitored at 1100~1150℃. The billet size is 280*280*mm*6.0m. The billet is stacked and cooled for 24h.

[0031] (5) Rolling: Control the heating temperature of the soaking zone to 1220-1250℃, and the reduction rate of the first and second passes to be greater than 60%; carry out water-controlled rolling, with an ultra-low temperature final rolling temperature of 650-700℃ and a cumulative reduction rate of greater than 80%.

[0032] (6) Slow cooling after rolling: After rolling, the water is used for strong cooling, and the temperature of the upper cooling bed is controlled at 730-780℃. The cooling bed is densely packed for slow cooling, and the temperature of the exit of the hood is controlled below 500℃. The slow cooling rate is 0.05℃ / S.

[0033] The following examples further illustrate the process. Each example was produced according to the process flow of converter-refining-continuous casting-rolling; the chemical composition of the steel in each example is shown in Table 1, with the remainder being Fe and unavoidable impurities; the performance results of the flat steel produced in each example and comparative example are shown in Table 2.

[0034] Example 1:

[0035] A wear-resistant flat steel and its production method are disclosed. The chemical composition of the steel (by weight percentage) is: C: 0.42%, Si: 0.32%, Mn: 0.70%, P: 0.009%, S: 0.005%, Cr: 0.62%, Mo: 0.16%, Al... T :0.060%, B: 0.0012%, Ni: 1.53%.

[0036] The specific production steps are as follows:

[0037] (1) Smelting: The weight of molten iron fed into the converter is 120 tons, and the weight of scrap steel is 30 tons;

[0038] (2) The basicity of the final slag of the LF furnace refining slag is 6.5; RH soft blowing for 30 minutes, and the outlet temperature is 1550℃.

[0039] (3) The secondary cooling water ratio is 0.20L / KG, the superheat of the tundish is 26℃, the temperature of the center point of the inner arc surface of the billet entering the straightening machine is monitored to be 1100~1120℃, and the secondary cooling water distribution is finely adjusted.

[0040] (4) The billet heating time is 240 minutes, the high temperature section temperature is controlled at 1220℃ for 75 minutes, and the final rolling temperature is 680℃.

[0041] (5) After rolling, the water cooling and controlled cooling are directly applied. The temperature in the slow cooling zone is 770℃ and the temperature out of the slow cooling zone is 280℃.

[0042] Example 2:

[0043] A wear-resistant flat steel and its production method are disclosed. The chemical composition of the steel (by weight percentage) is: C: 0.41%, Si: 0.35%, Mn: 0.74%, P: 0.008%, S: 0.001%, Cr: 0.60%, Mo: 0.15%, Al: 0.41%.T :0.065%, B: 0.0013%, Ni: 1.52%.

[0044] The specific production steps are as follows:

[0045] (1) Smelting: The weight of molten iron fed into the converter is 122 tons, and the weight of scrap steel is 31 tons;

[0046] (2) The basicity of the final slag of the LF furnace refining slag is 7.0; RH soft blowing for 31 minutes, and the outlet temperature is 1550℃.

[0047] (3) The secondary cooling water ratio is 0.20L / KG, the tundish superheat is 30℃, and the temperature of the center point of the inner arc surface of the billet entering the straightening machine is monitored to be 1100~1120℃. The secondary cooling water distribution is finely adjusted.

[0048] (4) The billet heating time is 260 minutes, the high temperature section temperature is controlled at 1230℃ for 70 minutes, and the final rolling temperature is 670℃.

[0049] (5) After rolling, the water cooling and controlled cooling are directly applied. The temperature in the slow cooling zone is 760℃ and the temperature out of the slow cooling zone is 300℃.

[0050] Example 3:

[0051] A wear-resistant flat steel and its production method are disclosed. The chemical composition of the steel (by weight percentage) is: C: 0.41%, Si: 0.35%, Mn: 0.78%, P: 0.010%, S: 0.002%, Cr: 0.64%, Mo: 0.15%, Al: 0.41%. T :0.062%, B: 0.0014%, Ni: 1.52%.

[0052] The specific production steps are as follows:

[0053] (1) Smelting: The weight of molten iron fed into the converter is 120 tons, and the weight of scrap steel is 31 tons;

[0054] (2) The basicity of the final slag of the LF furnace refining slag is 6.8; RH soft blowing for 26 minutes, and the outlet temperature is 1550℃.

[0055] (3) The secondary cooling water ratio is 0.20L / KG, the tundish superheat is 31℃, and the temperature of the center point of the inner arc surface of the billet entering the straightening machine is monitored to be 1100~1120℃. The secondary cooling water distribution is finely adjusted.

[0056] (4) The billet heating time is 255 minutes, the high temperature section temperature is controlled at 1230℃ for 70 minutes, and the final rolling temperature is 670℃.

[0057] (5) After rolling, the water cooling and controlled cooling are directly applied. The temperature in the slow cooling zone is 760℃ and the temperature out of the slow cooling zone is 300℃.

[0058] Example 4:

[0059] A wear-resistant flat steel and its production method are disclosed. The steel's chemical composition by weight percentage is: C: 0.40%, Si: 0.37%, Mn: 0.75%, P: 0.009%, S: 0.003%, Cr: 0.63%, Mo: 0.16%, Al... T :0.070%, B: 0.0015%, Ni: 1.50%.

[0060] The specific production steps are as follows:

[0061] (1) Smelting: The weight of molten iron fed into the converter is 120 tons, and the weight of scrap steel is 31 tons;

[0062] (2) The basicity of the final slag of the LF furnace refining slag is 6.8; RH soft blowing for 26 minutes, and the outlet temperature is 1550℃.

[0063] (3) The secondary cooling water ratio is 0.20L / KG, the tundish superheat is 31℃, and the temperature of the center point of the inner arc surface of the billet entering the straightening machine is monitored to be 1100~1120℃. The secondary cooling water distribution is finely adjusted.

[0064] (4) The billet heating time is 270 minutes, the high temperature section temperature is controlled at 1230℃ for 70 minutes, and the final rolling temperature is 670℃.

[0065] (5) After rolling, the water cooling and controlled cooling are directly applied. The temperature in the slow cooling zone is 760℃ and the temperature out of the slow cooling zone is 300℃.

[0066] Table 1. Chemical composition (%) of the steel in each embodiment.

[0067] Example C Si Mn P S <![CDATA[Al T ]]> Cr Mo B Ni 1 0.42 0.32 0.70 0.009 0.005 0.060 0.62 0.16 0.0012 1.53 2 0.41 0.35 0.74 0.008 0.001 0.065 0.60 0.15 0.0013 1.52 3 0.41 0.35 0.78 0.010 0.002 0.062 0.64 0.15 0.0014 1.52 4 0.40 0.37 0.75 0.009 0.003 0.070 0.63 0.16 0.0015 1.50

[0068] Table 2 Performance test indicators of the examples and comparative examples

[0069] project Tensile strength, MPa -20℃ V-shaped impact Rockwell hardness, HRC Target 1800～2000 ≥30J 55～60 Example 1 1970 41 58 Example 2 1965 46 57 Example 3 1926 45 56 Example 4 1954 49 56 Comparative Example 1 1750 20 54 Comparative Example 2 1920 17 56 Comparative Example 3 1780 18 53

[0070] Comparative Example 1:

[0071] A method for producing wear-resistant flat steel, wherein the chemical composition of the steel by weight percentage is: C: 0.40%, Si: 0.40%, Mn: 0.80%, Cr: 0.02%, Mo: 0.11%, V: 0.11%, Al... T 0.031%, P: 0.012%, S: 0.002%, Cu: 0.02%, N: 0.0038%, with the remainder being Fe and unavoidable impurities.

[0072] The production process steps are the same as in Example 1. Performance testing is shown in Table 2.

[0073] Comparative Example 2:

[0074] A method for producing wear-resistant flat steel, wherein the chemical composition of the steel by weight percentage is: C: 0.42%, Si: 0.22%, Mn: 0.60%, Cr: 1.20%, Mo: 0.15%, V: 0.01%, Al... T 0.025%, P: 0.012%, S: 0.005%, Cu: 0.03%, N: 0.0037%, with the remainder being Fe and unavoidable impurities.

[0075] The process steps are the same as in Example 2. Performance testing results are shown in Table 2.

[0076] Comparative Example 3:

[0077] The chemical composition of the steel is the same as that in Example 2.

[0078] The difference between the process steps and Example 3 is that the low-temperature rolling technology was not used in this composition system. Instead, the flat steel obtained by conventional continuous rolling was used. The final rolling temperature was controlled above 860°C, the upper cooling bed temperature was controlled at 830°C, the exit cooling bed temperature was 500°C, and the cooling rate reached 1°C / s. The original grain size grew, and the grains could not be refined after heat treatment, resulting in low impact energy, strength and hardness.

[0079] In summary, existing steel grades and flat steel obtained through conventional continuous rolling cannot simultaneously meet the requirements for strength and impact resistance after testing. However, the flat steel produced using the technical solution of this invention is suitable for manufacturing rectangular wear-resistant strips for engineering machinery with a thickness of 20–40 mm and a width of 60–100 mm. While maintaining good weldability, it possesses high strength, high toughness, and high wear resistance. After heat treatment, its tensile strength exceeds 1800 MPa, its KV2 impact toughness at -20℃ is ≥30 J, its Rockwell hardness is 55–60 HRC, and it exhibits excellent wear resistance.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A wear-resistant flat steel, characterized in that, The chemical composition of the steel by weight percentage is as follows: C: 0.40%–0.50%, Si: 0.20%–0.40%, Mn: 0.60%–0.80%, P≤0.012%, S≤0.012%, Cr: 0.50%–1.00%, Mo: 0.10%–0.20%, Al: 0.050%–0.080%, B: 0.0010%–0.0020%, Ni: 1.40%–1.80%, with the remainder being Fe and unavoidable impurities.

2. The method for producing wear-resistant flat steel as described in claim 1, characterized in that, This includes converter smelting, LF furnace refining, RH vacuum treatment, continuous casting, rolling and slow cooling processes; The rolling process is as follows: the heating temperature of the soaking zone is controlled at 1220-1250℃, the reduction rate of the first and second passes is greater than 60%, the final rolling temperature is 650-700℃, and the cumulative reduction rate is greater than 80%. The slow cooling process involves: strong water cooling after rolling, controlling the temperature of the upper cooling bed at 730-780℃, slow cooling with close-packed cooling beds, controlling the temperature of the material exiting the cooling hood below 500℃, and a slow cooling rate of 0.05℃ / S.

3. The method for producing wear-resistant flat steel as described in claim 2, characterized in that, The converter smelting process involves controlling the ratio of molten iron to scrap steel in the converter to be 8:2; and adding a composite deoxidizer during the tapping process to create slag and deoxidize.

4. The method for producing wear-resistant flat steel as described in claim 3, characterized in that, The LF furnace refining process involves controlling the LF basicity at 6.0–8.0, feeding aluminum wire before the LF furnace refining process ends to adjust the aluminum content in the molten steel to 0.070%–0.090%, feeding calcium wire before leaving the station to treat the molten steel with calcium, including 150 meters for the first furnace and 120 meters for the second and subsequent furnaces, and then adding a covering agent to protect the molten steel.

5. The method for producing wear-resistant flat steel as described in claim 4, characterized in that, The RH vacuum treatment process involves: evacuating the RH tank to below 67 Pa, maintaining the vacuum for 15 minutes, breaking the vacuum to determine the hydrogen content in the molten steel, and controlling the hydrogen content to ≤1.5 ppm. The soft blowing time before leaving the station is 25-35 minutes.

6. The method for producing wear-resistant flat steel as described in claim 5, characterized in that, The continuous casting process employs a weak cooling method with a water content of 0.20 L / kg and a target superheat value of 25℃~35℃ in the tundish. The water distribution in each zone is finely adjusted through a light-reduction process. Segregation in continuous casting is reduced by cooperating with the crystallizer and the end electromagnetic stirring. The temperature of the center point of the inner arc surface of the billet entering the straightening machine is monitored at 1100~1150℃. The billet size is 280*280*mm*6.0m. The billet is stacked and cooled for 24 hours.

7. The method for producing wear-resistant flat steel as described in claim 6, characterized in that, The wear-resistant flat steel is suitable for making rectangular wear-resistant strips for engineering machinery with a thickness of 20-40mm and a width of 60-100mm. The microstructure is composed of sorbite + pearlite + ferrite. After heat treatment, the tensile strength is 1800-2000MPa, the KV2 impact toughness value at -20℃ is ≥30J, and the Rockwell hardness is 55-60HRC.

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