Wear-resistant steel with good low-temperature impact toughness and preparation method thereof

Abstract

The invention provides wear-resistant steel with good low-temperature impact toughness and a preparation method thereof, and relates to the technical field of wear-resistant steel. The wear-resistant steel with the good low-temperature impact toughness is obtained through molten iron pretreatment, refining, continuous casting, primary heat treatment, rolling, secondary heat treatment, quenching and tempering. The wear-resistant steel comprises the following chemical components in percentage by mass: 0.2 wt.%-0.3 wt.% of C, 0.2 wt.%-0.5 wt.% of Si, 0.4 wt.%-0.6 wt.% of Mn, 10 wt.%-15 wt.% of Cr, 0.5 wt.%-1 wt.% of Mo, 0.3 wt.%-0.4 wt.% of V, less than or equal to 0.015 wt.% of S and less than or equal to 0.015 wt.% of P. By adding a specific amount of vanadium into the raw materials and combining a specific preparation process, the content of retained austenite is reduced, precipitation of carbides is promoted, the proportion of large-angle grain boundaries in the wear-resistant steel is increased, and then the low-temperature impact toughness of the wear-resistant steel is improved.

Description

Technical Field

[0001] The invention relates to the technical field of wear-resistant steel, and in particular to a wear-resistant steel with good low-temperature impact toughness and a preparation method thereof. Background Art

[0002] Wear-resistant steel materials refer to iron-based alloys with excellent wear resistance, which are widely used in mining, construction, metallurgy, power and other industries. These materials can significantly improve their wear resistance and service life through specific alloying and heat treatment processes.

[0003] Commonly used wear-resistant steel materials include wear-resistant cast iron, high manganese steel, non-manganese wear-resistant alloy steel, etc. Among them, high manganese steel has a low degree of work hardening under low impact loads and has insufficient wear resistance; high chromium cast iron has coarse carbides in its structure, showing high brittleness and easy cracking; non-manganese wear-resistant alloy steel is widely used in various fields as a wear-resistant steel material due to its wide adjustable performance and controllable cost.

[0004] However, in low temperature environments, the toughness of wear-resistant steel will decrease significantly, and brittle fracture will easily occur, which will lead to sudden fracture due to the expansion of tiny cracks, which is extremely dangerous in industrial applications. At the same time, insufficient low-temperature impact toughness causes the equipment to be unable to be put into use or the reliability and stability are seriously reduced in cold areas or low-temperature conditions. In addition, many industries such as mining, metallurgy, energy, etc. often need to operate in low-temperature environments. Therefore, it is necessary to improve the low-temperature impact toughness of wear-resistant steel, which is of great significance to improving the safety and reliability of materials, extending the service life of equipment, reducing maintenance costs, meeting the needs of specific industries, improving economy and competitiveness, and ensuring the stable operation of equipment in various environments. Summary of the invention

[0005] In view of this, the present invention provides a wear-resistant steel with good low-temperature impact toughness and a preparation method thereof. The present invention reduces the residual austenite content, promotes the precipitation of carbides, and increases the proportion of high-angle grain boundaries in the wear-resistant steel by adding a specific amount of vanadium to the raw materials and combining a specific preparation process, thereby improving the low-temperature impact toughness of the wear-resistant steel.

[0006] The present invention provides a wear-resistant steel with good low-temperature impact toughness. The wear-resistant steel with good low-temperature impact toughness is obtained after molten iron pretreatment, refining, continuous casting, primary heat treatment, rolling, secondary heat treatment, quenching, and tempering. The chemical composition and mass percentage of the wear-resistant steel with good low-temperature impact toughness are as follows:

[0007] C 0.2wt.%~0.3wt.%, Si 0.2wt.%~0.5wt.%, Mn 0.4wt.%~0.6wt.%, Cr10wt.%~15wt.%, Mo 0.5wt.%~1wt.%, V 0.3wt.%~0.4wt.%, S≤0.015wt.%, P≤0.015wt.%.

[0008] The present invention also provides a method for preparing wear-resistant steel with good low-temperature impact toughness, comprising the following steps:

[0009] The raw materials are melted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined. After the refining, they are continuously cast. The ingots are heated and then rolled. After the rolling is completed, they are cooled. Then, the steel plates are heat treated. After the heat treatment is completed, they are quenched and tempered to obtain wear-resistant steel with low-temperature impact toughness.

[0010] Preferably, the continuous casting speed is 3.5-4.0 m / min, and the superheat is 10°C-30°C.

[0011] Preferably, the heat treatment temperature is 950°C to 1050°C, and the heat treatment time is 2 to 4 hours. More preferably, the temperature rise procedure of the heat treatment stage is as follows: first, the temperature is raised to 300°C to 350°C at a rate of 45°C / h to 50°C / h, then the temperature is raised to 800°C to 850°C at a rate of 65°C / h to 75°C / h, and finally the temperature is raised to 950°C to 1050°C at a rate of 70°C / h to 75°C / h for heat treatment.

[0012] Compared with the prior art, the present invention effectively promotes the precipitation of carbides and reduces the content of residual austenite by adding a specific amount of vanadium to the raw materials and combining a specific preparation process, thereby refining the grains and increasing the proportion of large-angle grain boundaries in the wear-resistant steel, thereby significantly improving the low-temperature impact toughness of the wear-resistant steel. The precise heating program (gradually heating to the target temperature and keeping warm at different stages) during the heat treatment of the present invention can optimize the internal structure of the steel, thereby improving its toughness and wear resistance, and ensuring that the wear-resistant steel exhibits excellent impact toughness in a low-temperature environment. The preparation method of the present invention adopts traditional smelting, refining, continuous casting, rolling and other processes, combined with appropriate heat treatment and cooling steps, is relatively simple to operate, does not require overly complex equipment or excessive cost investment, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described below in conjunction with the accompanying drawings.

[0014] Figure 1 The present invention is a flow chart of the preparation process of wear-resistant steel with good low-temperature impact toughness. DETAILED DESCRIPTION

[0015] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0016] The present invention provides a wear-resistant steel with good low-temperature impact toughness. The wear-resistant steel with good low-temperature impact toughness is obtained after molten iron pretreatment, converter smelting, refining, continuous casting, rolling, heat treatment, quenching, and tempering. The chemical composition and mass percentage of the wear-resistant steel with good low-temperature impact toughness are as follows:

[0017] C 0.2wt.%~0.3wt.%, Si 0.2wt.%~0.5wt.%, Mn 0.4wt.%~0.6wt.%, Cr10wt.%~15wt.%, Mo 0.5wt.%~1wt.%, V 0.3wt.%~0.4wt.%, S≤0.015wt.%, P≤0.015wt.%, and the balance is Fe and unavoidable impurities.

[0018] The present invention reduces the grain size and precipitates carbides to improve the low-temperature impact toughness of wear-resistant steel by adding a certain amount of V to the raw materials. However, the present invention strictly limits the content of V. In the technical embodiment of the present invention, the content of V is preferably 0.3wt.% to 0.4wt.%. Vanadium is a strong carbide-forming element that can promote the precipitation of carbides. An appropriate amount of vanadium content helps to form stable carbides in steel, thereby improving the wear resistance of steel. However, too high a vanadium content will cause excessive precipitation of carbides, affecting the toughness of steel, especially under low temperature conditions. In addition, in the present invention, vanadium can effectively improve the grain boundary strength of steel and increase the proportion of high-angle grain boundaries. An appropriate amount of vanadium helps to improve the overall strength and low-temperature toughness of steel. However, too much vanadium will reduce the plasticity of steel, thereby affecting the low-temperature impact toughness. The addition of vanadium as an alloying element will increase production costs. Excessive vanadium content not only increases production costs, but also affects the machinability of steel, especially during casting and heat treatment. Therefore, limiting the content of V is of great significance for balancing the relationship between carbide precipitation and the toughness of steel, ensuring that the steel has good low-temperature impact toughness and comprehensive mechanical properties, and avoiding unnecessary costs and processing difficulties. Finally, vanadium has a synergistic effect with other alloying elements (such as chromium, molybdenum, etc.), which can optimize the structure and performance of steel. An increase or decrease in its content will affect its synergistic effect with other alloying elements, resulting in performance that is not as expected. Therefore, the vanadium content of 0.3wt.% to 0.4wt.% in the alloy steel of the present invention can ensure the best performance of wear-resistant steel in terms of low-temperature impact toughness, wear resistance and comprehensive mechanical properties, while avoiding the adverse effects of excessive vanadium.

[0019] The present invention also provides a method for preparing wear-resistant steel with good low-temperature impact toughness, comprising the following steps:

[0020] The raw materials are melted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined. After the refining, they are continuously cast. The ingots are heated and then rolled. After the rolling is completed, they are cooled. Then, the steel plates are heat treated. After the heat treatment is completed, they are quenched and tempered to obtain wear-resistant steel with low-temperature impact toughness.

[0021] In some specific embodiments of the present invention, the refining is LF refining and / or RH refining. In some preferred embodiments of the present invention, the refining is LF refining. In the present invention, LF refining is mainly used for desulfurization, deoxidation, removal of inclusions and fine-tuning of composition, and at the same time, the molten steel is heated to reduce temperature fluctuations so that it has good temperature stability in subsequent processes. However, LF refining has limited ability to remove gaseous impurities (such as hydrogen and nitrogen) and is not effective in controlling oxidation losses of micro-alloying elements. RH refining is mainly used for degassing, which can effectively remove gaseous impurities such as hydrogen, oxygen and nitrogen, and significantly improve the toughness and fatigue resistance of steel. However, since RH refining is carried out in a vacuum environment, the cost is relatively high and the effect on desulfurization and deoxidation is limited, and the present invention mainly improves the low-temperature toughness of wear-resistant steel by combining element control with heat treatment process. Therefore, under the condition that the design requirements of alloy steel can be met, the present invention does not strictly limit the refining method, as long as the technical requirements can be met.

[0022] In some specific embodiments of the present invention, the continuous casting speed is 3.5-4.0 m / min, and the superheat is 10° C.-30° C.

[0023] The pulling speed in the continuous casting process of the present invention affects the solidification and crystallization process of the ingot. Too fast a pulling speed will lead to the formation of coarse grains or defects, while too slow a pulling speed will lead to uneven temperature gradients inside the ingot, affecting the grain structure and uniformity. In combination with the control of elements in the present invention, the continuous casting pulling speed is limited to the range of 3.5m / min to 4.0m / min, which helps the molten steel to cool stably during continuous casting and form a uniform and fine grain structure. In addition, a suitable continuous casting pulling speed helps to control the distribution of grains and grain boundary morphology, avoiding the occurrence of macroscopic defects (such as cracks or pores). A higher pulling speed may lead to rapid cooling of the ingot, thereby affecting the uniformity of the grains; while a too low pulling speed may lead to larger grains, reducing the strength and toughness of the steel. By precisely controlling the pulling speed, a more ideal grain structure can be achieved, which helps the smooth progress of subsequent processes.

[0024] Superheat refers to the difference between the actual temperature of the molten steel and the liquidus temperature. In the continuous casting process of the present invention, appropriate superheat helps to improve the fluidity of the molten steel and ensure that the molten steel can evenly fill the mold. Low superheat leads to increased viscosity of the molten steel and poor fluidity, while excessive superheat easily causes excessive oxidation and inclusion formation, reducing purity. The present invention also optimizes the solidification process of the molten steel by controlling the superheat. Within the appropriate superheat range (10°C to 30°C), uniform solidification of the molten steel can be promoted, the formation of coarse grains can be avoided, and excessive carbides and oxides can be avoided from precipitating in the ingot, affecting the purity of the steel and subsequent processing performance.

[0025] In some specific embodiments of the present invention, the rolling is rough rolling and finishing rolling, the rough rolling start temperature is 1180℃~1230℃, the finishing rolling start temperature is 880℃~920℃, and the finishing rolling final temperature is 850℃~875℃; the finishing rolling stage starts after the intermediate billet temperature drops to the rough rolling start temperature, the finishing rolling passes are 3 to 5 times, and the cooling rate after rolling is 20℃ / s~30℃ / s. In the preferred embodiment of the present invention, dephosphorization is performed as appropriate during the rolling process.

[0026] In some specific embodiments of the present invention, the heat treatment temperature is 950° C. to 1050° C., and the heat treatment time is 2 to 4 hours.

[0027] The present invention limits the heat treatment temperature to 950°C to 1050°C and the heat treatment time to 2 to 4 hours in order to reduce the residual austenite content, promote the precipitation of carbides, increase the proportion of large-angle grain boundaries in the wear-resistant steel, and further optimize the organizational structure of the wear-resistant steel and improve its performance, especially in terms of low-temperature impact toughness, wear resistance and mechanical properties.

[0028] In some preferred embodiments of the present invention, the temperature rising program of the heat treatment stage is as follows: first, the temperature is raised to 300°C-350°C at a rate of 45°C / h-50°C / h, then the temperature is raised to 800°C-850°C at a rate of 65°C / h-75°C / h, and finally the temperature is raised to 950°C-1050°C at a rate of 70°C / h-75°C / h for heat treatment.

[0029] In the heat treatment stage of the present invention, the temperature rise procedure is limited to ensure that the internal structure of the steel is uniform and stable, and to avoid unnecessary stress, defects or uneven organization during the heating process. Specifically: the initial temperature rises to 300°C to 350°C at a rate of 45°C / h to 50°C / h. In this stage, the temperature rises slowly to release the residual stress inside the steel, prevent the concentration of thermal stress caused by rapid temperature rise, and reduce the risk of cracks or deformation. At the same time, this slow heating can also reduce the thermal stress caused by the temperature difference, avoid cracks or ruptures in the steel due to thermal shock at a lower temperature, and ensure the integrity of the steel structure. Subsequently, the temperature is raised to 800°C to 850°C at a rate of 65°C / h to 75°C / h. The faster heating rate in this stage can promote the uniform growth of grains, gradually transform the internal organization into austenite, and prepare for the subsequent high temperature stage. Finally, the temperature is raised to 950℃~1050℃, and the rate is 70℃ / h~75℃ / h. Rapid heating can keep the steel in a small and uniform grain structure, which not only ensures the strength of the steel, but also improves its toughness. Alloy elements such as vanadium and chromium can fully diffuse and combine with carbon to form uniformly distributed carbide particles, further enhancing the wear resistance and hardness of the steel. It can be seen that the present invention can gradually diffuse heat into the steel through the gradual heating procedure, ensure uniform temperature distribution of the material at different parts, avoid internal and external stress differences caused by temperature differences, ensure the uniformity of the material organization, and then improve the overall performance of the material, so that the precipitation of carbides and grain boundary structure in the steel reach an ideal state.

[0030] In some specific embodiments of the present invention, the quenching process is oil quenching, the quenching temperature is 950° C. to 1050° C., and the holding time is 2.5 to 3 hours.

[0031] In some specific embodiments of the present invention, the tempering temperature is 220° C. to 250° C., the holding time is 2 to 3 hours, and the cooling method is air cooling.

[0032] In some specific embodiments of the present invention, after the tempering process, the steps of sampling and testing, warehousing, and product shipment are also included.

[0033] In order to further illustrate the present invention, the following examples are provided for detailed description. The raw materials used in the following examples of the present invention are all commercially available.

[0034] Unless otherwise specified, all experiments were repeated three times. SPSS 21.0 was used for analysis of variance (ANOVA) and Duncan's multiple comparison analysis. The results were expressed as mean or mean ± standard deviation. P < 0.05 indicated a significant difference.

[0035] Example 1 Effect of V content on low temperature impact toughness of wear-resistant steel

[0036] The main components of wear-resistant steel are shown in Table 1.

[0037] Table 1 Main chemical composition of wear-resistant steel (mass fraction, %)

[0038] C Si Mn Cr Mo S P V Fe 0.25 0.32 0.46 13.27 0.93 0.01 0.01 0.20～0.45 margin

[0039] The preparation method of wear-resistant steel is as follows:

[0040] The raw materials are smelted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined by LF. After the refining, they are continuously cast at a pulling speed of (3.5±0.2) m / min and a superheat of (25±5)°C. The ingot is heated to 1230°C and then rough rolled. After the rough rolling is completed, the rough rolling is followed by finish rolling. The start rolling temperature of the rough rolling is 1193°C, the start rolling temperature of the finish rolling is 915°C, and the final rolling temperature of the finish rolling is 857°C. The finish rolling stage is performed from the intermediate billet temperature down to the rough rolling temperature. The rolling starts after the rolling temperature is opened, the finishing passes are 5 times, the cooling rate after rolling is 25℃ / s, and after rolling is completed, the temperature is first increased to 350℃ at a rate of 50℃ / h, then increased to 850℃ at a rate of 65℃ / h, and finally increased to 1050℃ at a rate of 75℃ / h. Heat treatment is performed for 2h. After the heat treatment is completed, it is oil quenched at 980℃×3h, tempered at 230×2.5h, and air cooled to obtain wear-resistant steel with low-temperature impact toughness.

[0041] The performance of the samples was tested, and the results are shown in Table 2. The impact toughness test was carried out on a JB-30B impact testing machine, with a sample size of 10 mm × 10 mm × 55 mm and a Charpy standard V-notch.

[0042] Table 2 Performance test results

[0043] V content / wt.% Yield strength / MPa Tensile strength / MPa Elongation after break / % AKV(-40℃) / J 0.20 510 630 10.7 51 0.25 580 643 12.1 62 0.30 684 918 14.6 83 0.35 695 982 14.8 89 0.40 699 995 15.1 91 0.45 630 887 13.9 80

[0044] Comparative Example 1

[0045] The main components of wear-resistant steel are as follows:

[0046] C 0.25wt.%, Si 0.32wt.%, Mn 0.46wt.%, Cr 13.27wt.%, Mo 0.93wt.%, V 0.35wt.%, S 0.01wt.%, P 0.01wt.%, and the balance is Fe and inevitable impurities.

[0047] The preparation method of the wear-resistant steel is the same as that of Example 1, except that the drawing speed is different. The specific steps are:

[0048] The raw materials are smelted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined by LF. After the refining, they are continuously cast at a pulling speed of (5.0±0.2) m / min and a superheat of (25±5)°C. The ingot is heated to 1230°C and then rough rolled. After the rough rolling, the ingot is finished rolled. The starting temperature of the rough rolling is 1193°C, the starting temperature of the finishing rolling is 915°C, and the finishing temperature of the finishing rolling is 857°C. The finishing rolling stage is performed from the intermediate billet temperature to the rough rolling temperature. The rolling starts after the rolling temperature is opened, the finishing passes are 5 times, the cooling rate after rolling is 25℃ / s, and after rolling is completed, the temperature is first increased to 350℃ at a rate of 50℃ / h, then increased to 850℃ at a rate of 65℃ / h, and finally increased to 1050℃ at a rate of 75℃ / h. Heat treatment is performed for 2h. After the heat treatment is completed, it is oil quenched at 980℃×3h, tempered at 230×2.5h, and air cooled to obtain wear-resistant steel with low-temperature impact toughness.

[0049] Comparative Example 2

[0050] The main components of wear-resistant steel are as follows:

[0051] C 0.25wt.%, Si 0.32wt.%, Mn 0.46wt.%, Cr 13.27wt.%, Mo 0.93wt.%, V 0.35wt.%, S 0.01wt.%, P 0.01wt.%, and the balance is Fe and inevitable impurities.

[0052] The preparation method of the wear-resistant steel is the same as that of Example 1, except that no heat treatment is performed after rolling. The specific steps are as follows:

[0053] The raw materials are melted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined by LF. After the refining, they are continuously cast at a pulling speed of (3.5±0.2) m / min and a superheat of (25±5)°C. The ingot is heated to 1230°C and then rough rolled. After the rough rolling is completed, the finish rolling is performed. The start rolling temperature of the rough rolling is 1193°C, the start rolling temperature of the finish rolling is 915°C, and the final rolling temperature of the finish rolling is 857°C. The finish rolling stage starts after the temperature of the intermediate billet drops to the start rolling temperature of the rough rolling. The number of finish rolling passes is 5 times. The cooling rate after rolling is 25°C / s. After the rolling is completed, it is oil quenched at 980°C×3h, tempered at 230×2.5h, and air cooled to obtain a wear-resistant steel with low-temperature impact toughness.

[0054] Comparative Example 3

[0055] The main components of wear-resistant steel are as follows:

[0056] C 0.25wt.%, Si 0.32wt.%, Mn 0.46wt.%, Cr 13.27wt.%, Mo 0.93wt.%, V 0.35wt.%, S 0.01wt.%, P 0.01wt.%, and the balance is Fe and inevitable impurities.

[0057] The preparation method of the wear-resistant steel is the same as that of Example 1, except that the heat treatment temperature rise procedure after rolling is different. The specific steps are:

[0058] The raw materials are smelted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined by LF. After the refining, they are continuously cast at a pulling speed of (3.5±0.2) m / min and a superheat of (25±5)°C. The ingot is heated to 1230°C and then rough rolled. After the rough rolling is completed, the fine rolling is performed. The rough rolling start temperature is 1193°C, the fine rolling start temperature is 915°C, and the fine rolling final temperature is 857°C. The fine rolling stage starts after the intermediate billet temperature drops to the rough rolling start temperature. The fine rolling passes are 5 times. The cooling rate after rolling is 25°C / s. After the rolling is completed, the temperature is increased to 1050°C at a temperature rate of 75°C / h, and heat treated for 2h. After the heat treatment is completed, it is oil quenched at 980°C×3h, tempered at 230×2.5h, and air cooled to obtain a wear-resistant steel with low-temperature impact toughness.

[0059] Comparative Example 4

[0060] The main components of wear-resistant steel are as follows:

[0061] C 0.25wt.%, Si 0.32wt.%, Mn 0.46wt.%, Cr 13.27wt.%, Mo 0.93wt.%, V 0.35wt.%, S 0.01wt.%, P 0.01wt.%, and the balance is Fe and inevitable impurities.

[0062] The preparation method of the wear-resistant steel is the same as that of Example 1, except that quenching and tempering are not performed. The specific steps are as follows:

[0063] The raw materials are smelted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined by LF. After the refining, they are continuously cast at a pulling speed of (3.5±0.2) m / min and a superheat of (25±5)°C. The ingot is heated to 1230°C and then rough rolled. After the rough rolling is completed, the fine rolling is performed. The rough rolling start temperature is 1193°C, the fine rolling start temperature is 915°C, and the fine rolling final temperature is 857°C. The fine rolling stage starts after the intermediate billet temperature drops to the rough rolling start temperature. The fine rolling passes are 5 times. The cooling rate after rolling is 25°C / s. After the rolling is completed, the temperature is first increased to 350°C at a rate of 50°C / h, then increased to 850°C at a rate of 65°C / h, and finally increased to 1050°C at a temperature rate of 75°C / h. The steel is heat treated for 2h and air cooled to obtain a wear-resistant steel with low-temperature impact toughness.

[0064] The low temperature impact toughness of the samples of Comparative Examples 1 to 4 was tested, and the sample with a V content of 0.35 wt.% in Example 1 was used as a control. The testing method was the same as that in Example 1. The test results are shown in Table 3.

[0065] Table 3 Performance test results of samples of comparative examples 1 to 4

[0066] sample AKV(-40℃) / J Control group 88.67±1.53a Comparative Example 1 79.33±2.08b Comparative Example 2 47.67±1.53d Comparative Example 3 55.33±3.06c Comparative Example 4 59.33±2.08c

[0067] Example 2 A wear-resistant steel with good low-temperature impact toughness, the chemical composition and mass percentage are as follows:

[0068] C 0.3wt.%, Si 0.35wt.%, Mn 0.45wt.%, Cr 12.85wt.%, Mo 0.82wt.%, V 0.3wt.%, S 0.01wt.%, P 0.01wt.%, and the balance is Fe and inevitable impurities.

[0069] The preparation method of the wear-resistant steel with good low-temperature impact toughness is as follows:

[0070] The raw materials are smelted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined by LF. After the refining, they are continuously cast at a pulling speed of (3.7±0.2) m / min and a superheat of (25±5)°C. The ingot is heated to 1250°C and then rough rolled. After the rough rolling is completed, the rough rolling is followed by finish rolling. The start rolling temperature of the rough rolling is 1182°C, the start rolling temperature of the finish rolling is 887°C, and the final rolling temperature of the finish rolling is 872°C. The temperature of the intermediate ingot is reduced from the rough rolling temperature to the start rolling temperature of the finish rolling. The rolling starts after the rolling temperature is reached, the finishing passes are 5 times, the cooling rate after rolling is 20℃ / s, and after rolling is completed, the temperature is first increased to 300℃ at a rate of 45℃ / h, then increased to 800℃ at a rate of 75℃ / h, and finally increased to 950℃ at a rate of 65℃ / h. Heat treatment is performed for 4h. After the heat treatment is completed, it is oil quenched at 950℃×2.5h, tempered at 220×2h, and air cooled to obtain wear-resistant steel with low-temperature impact toughness.

[0071] According to tests, the wear-resistant steel obtained in this embodiment has a yield strength of 792 MPa, a tensile strength of 988 MPa, an elongation after fracture of 14.9%, and an AKV (-40° C.) of 90 J.

[0072] Example 3 A wear-resistant steel with good low-temperature impact toughness, the chemical composition and mass percentage are as follows:

[0073] C 0.2wt.%, Si 0.30wt.%, Mn 0.50wt.%, Cr 14.11wt.%, Mo 0.95wt.%, V 0.4wt.%, S 0.01wt.%, P 0.01wt.%, and the balance is Fe and inevitable impurities.

[0074] The preparation method of the wear-resistant steel with good low-temperature impact toughness is as follows:

[0075] The raw materials are smelted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined by LF. After the refining, they are continuously cast at a pulling speed of (3.5±0.2) m / min and a superheat of (25±5)°C. The ingot is heated to 1200°C and then rough rolled. After the rough rolling, the ingot is finished rolled. The rough rolling start temperature is 1200°C, the finishing rolling start temperature is 906°C, and the finishing rolling final temperature is 869°C. The finishing rolling stage is from the intermediate billet temperature to the rough rolling temperature. Starting from the rolling temperature, the finishing passes are 5 times, the cooling rate after rolling is 30℃ / s, and after rolling is completed, the temperature is first increased to 330℃ at a rate of 48℃ / h, then to 830℃ at a rate of 67℃ / h, and finally to 1000℃ at a rate of 70℃ / h. Heat treatment is performed for 2h. After the heat treatment is completed, it is oil quenched at 1050℃×2.5h, tempered at 220×2h, and air cooled to obtain wear-resistant steel with low-temperature impact toughness.

[0076] After testing, the wear-resistant steel obtained in this embodiment has a yield strength of 783 MPa, a tensile strength of 986 MPa, an elongation after fracture of 14.5%, and an AKV (-40° C.) of 89 J.

[0077] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A wear-resistant steel with good low-temperature impact toughness, characterized in that: The wear-resistant steel is obtained after molten iron pretreatment, refining, continuous casting, primary heat treatment, rolling, secondary heat treatment, quenching, and tempering. The chemical composition and mass percentage of the wear-resistant steel are as follows: C 0.2wt.%~0.3wt.%, Si 0.2wt.%~0.5wt.%, Mn 0.4wt.%~0.6wt.%, Cr10wt.%~15wt.%, Mo 0.5wt.%~1wt.%, V 0.3wt.%~0.4wt.%, S≤0.015wt.%, P≤0.015wt.%.

2. The method for preparing a wear-resistant steel having good low-temperature impact toughness according to claim 1, characterized in that: The following steps are involved: The raw materials are melted into molten iron and then pretreated. After the pretreatment, they are smelted in a converter and refined. After the refining, they are continuously cast. The ingots are heated and then rolled. After the rolling is completed, they are cooled. Then, the steel plates are heat treated. After the heat treatment is completed, they are quenched and tempered to obtain wear-resistant steel with low-temperature impact toughness.

3. The preparation method according to claim 2, characterized in that: The continuous casting speed is 3.5-4.0 m / min, and the superheat is 10°C-30°C.

4. The preparation method according to claim 2, characterized in that: The rolling includes rough rolling and finish rolling.

5. The preparation method according to claim 4, characterized in that: The starting temperature of the rough rolling is 1180°C to 1230°C, the starting temperature of the finishing rolling is 880°C to 920°C, and the final rolling temperature of the finishing rolling is 850°C to 875°C.

6. The preparation method according to claim 2, characterized in that: The heat treatment temperature is 950° C. to 1050° C., and the heat treatment time is 2 to 4 hours.

7. The preparation method according to claim 6, characterized in that: The temperature rising procedure of the heat treatment stage is as follows: first, the temperature is raised to 300°C-350°C at a rate of 45°C / h-50°C / h, then the temperature is raised to 800°C-850°C at a rate of 65°C / h-75°C / h, and finally the temperature is raised to 950°C-1050°C at a rate of 70°C / h-75°C / h for heat treatment.

8. The preparation method according to claim 2, characterized in that: The quenching process is oil quenching, the quenching temperature is 950° C. to 1050° C., and the holding time is 2.5 to 3 hours.

9. The preparation method according to claim 2, characterized in that: The tempering temperature is 220° C. to 250° C., and the holding time is 2 to 3 hours.

10. The preparation method according to claim 9, characterized in that: The tempering cooling method is air cooling.

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