Hot-rolled wear-resistant steel plate and method for manufacturing the same

Abstract

This invention discloses a hot-rolled wear-resistant steel plate and its manufacturing method. The chemical composition of the hot-rolled wear-resistant steel plate includes C, Si, Mn, B, Ti, Als, and Fe, and must simultaneously satisfy: 0.040% ≤ Ti-3.42*N-3*S-B≤0.14%. This invention adopts a heat-free TMCP process, the material has a tensile strength ≥1050MPa, wear resistance reaches NM300 level, yield strength ratio ≤0.70, cold bending performance reaches 180°, D=1a is qualified, and the plate shape qualification rate is ≥95%. The material has the advantages of high strength, high hardness, low yield strength ratio, easy forming, and low production cost, and can be applied to the manufacture of high-strength wear-resistant parts for special vehicles, engineering machinery, etc.

Description

Technical Field

[0001] This invention belongs to the field of wear-resistant steel technology, specifically relating to a hot-rolled wear-resistant steel plate and its manufacturing method. Background Technology

[0002] Regarding wear-resistant steel plates, the current mainstream production process is quenching and tempering heat treatment, resulting in a martensitic microstructure. Quenched and tempered steel plates offer advantages such as high strength, high wear resistance, and stable plate shape. However, the process is lengthy, production costs are high, and the product's formability is limited; cold bending performance can only guarantee 90°, with D=6a being acceptable. Another process is online quenching without quenching and tempering, producing a martensitic + ferritic microstructure, as shown in patents published under CN103233161A, CN104532126A, CN108411203A, CN110760752A, and CN111334720A. These products have a wear resistance grade of NM300 and offer advantages such as high strength, high wear resistance, and easy formability. However, due to factors such as thin product dimensions, rapid cooling rate, narrow cooling process window, and low-temperature coiling, the plate shape qualification rate of wear-resistant steel plates produced by online quenching is relatively low, and plate shape control has always been a challenge in the industry.

[0003] Compared to martensitic and ferritic structures, bainitic structures exhibit a better balance of strength, hardness, plasticity, and toughness, and have been applied in the production of wear-resistant steels in recent years. Patents published under CN112575263A, CN112575264A, and CN112553543A, among others, describe structures with granular bainite and acicular ferrite. These structures contain a high Ti content (0.5–0.8%), which prevents Ti from completely dissolving into the matrix during heating. Combined with a medium C content design, this results in the formation of numerous micron-sized TiC precipitates. While this may improve wear resistance to some extent, the large number of hard micron-sized TiC particles negatively impacts the material's plasticity and toughness, and the maximum tensile strength is only 900 MPa, indicating a low strength level.

[0004] The patent disclosed in announcement number CN 109234612 B has a bainitic microstructure, a maximum tensile strength of 900 MPa, a relatively low strength level, and a yield strength ratio of 0.89-0.90, which is relatively high.

[0005] The patents published under publication numbers CN114908291A and CN114892080A have a bainitic microstructure and a tensile strength of up to 1000 MPa. However, on the one hand, the alloy composition contains a high content of precious alloying elements such as Mo, Cu, Ni, and rare earth elements, resulting in a high alloy cost. On the other hand, the material has a yield strength ratio > 0.87, which is not conducive to the cold bending forming performance of the material.

[0006] The patents published under publication numbers CN114058945A, CN107747056A, CN110747405A, and CN106636899A have a bainitic microstructure and a tensile strength of 1000MPa. However, their production process requires tempering or quenching + tempering or cold rolling + annealing heat treatment. The improvement in material strength is mainly achieved through tempering or quenching + tempering or annealing processes, which result in a long process flow and high production costs.

[0007] The “A thin-gauge 1400MPa grade bainitic steel and its manufacturing method” published by CN113430467A is produced by thin strip continuous casting and rolling process. The difference from the traditional hot continuous rolling process is that (1) the fine-grained as-cast structure obtained by twin-roll thin strip continuous casting under rapid solidification conditions, combined with the air mist cooling system for rapid cooling, can form a bainitic structure with very fine grain size, which can easily achieve higher strength, and the alloy addition amount is lower. The rolling cooling process parameters are not suitable for the traditional hot continuous rolling process; (2) due to the cast structure with a depth of about 2mm at the edge of the cast strip, the edge quality of the thin strip cast and rolled strip is poor and the edge must be trimmed.

[0008] In summary, regarding the publicly available patents for wear-resistant steel, existing technologies employing quenching and tempering heat treatment with a martensitic microstructure suffer from drawbacks such as long process flows, high production costs, and limited material formability. Existing technologies using heat-free online quenching with a martensitic + ferrite microstructure exhibit low strip shape qualification rates and difficulties in shape control. Existing technologies using hot rolling with a bainitic microstructure have several limitations. Firstly, the highest tensile strength is only 900 MPa, indicating a low strength level and a relatively high yield strength ratio. Secondly, even with tensile strengths reaching 1000 MPa, the alloy composition requires high levels of expensive alloying elements such as Mo, Cu, Ni, and rare earth elements, resulting in high alloy costs and a high yield strength ratio. Alternatively, the production process may require tempering, quenching + tempering, or cold rolling + annealing heat treatment, leading to long process flows and high production costs. Furthermore, even with tensile strengths reaching 1000 MPa, the alloy composition and process parameters of thin-strip continuous casting and rolling processes are not suitable for traditional hot rolling processes. Summary of the Invention

[0009] The purpose of this invention is to provide a hot-rolled wear-resistant steel plate and its manufacturing method. The plate adopts the heat-free TMCP process, the tensile strength of the material is ≥1050MPa, the wear resistance reaches the NM300 level, the yield strength ratio is ≤0.70, the cold bending performance reaches 180°, D=1a is qualified, and the plate shape qualification rate is ≥95%. The material has the advantages of high strength, high hardness, low yield strength ratio, easy forming, and low production cost, and can be used in the manufacture of high-strength wear-resistant parts for special vehicles, engineering machinery, etc.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A hot-rolled wear-resistant steel plate comprises the following chemical composition by weight percentage: C: 0.08–0.13%; Si: 0.60–1.40%; Mn: 1.60–2.40%; Ti: 0.050–0.15%; B: 0.0008–0.0030%; Als: 0.020–0.60%; P: ≤0.012%; S: ≤0.005%; N: ≤0.0050%; O: ≤0.0030%; the remainder being Fe and unavoidable inclusions; and must simultaneously satisfy: 0.040% ≤ Ti - 3.42 * N - 3 * SB ≤ 0.14%.

[0012] The metallographic structure of the hot-rolled wear-resistant steel plate consists of granular bainite and nano-sized precipitates, with the nano-precipitate size ≤20nm and the volume fraction of nano-sized precipitates 0.15~0.22%.

[0013] The hot-rolled wear-resistant steel plate has a yield strength ≥700MPa, tensile strength ≥1050MPa, yield ratio ≤0.70, and elongation A. 50 ≥16%, hardness ≥310HB, cold bending performance reaches 180°, D=1a qualified, flatness control of open plate ≤5mm / m, and plate shape qualification rate ≥95%.

[0014] The manufacturing method of the hot-rolled wear-resistant steel plate provided by the present invention includes the following steps: smelting, continuous casting, heating, rolling, cooling, coiling, leveling, and slitting.

[0015] In the heating step, the final temperature of the second heating stage is ≥1200℃, the heat soaking time is ≥30min, the slab exit temperature is 1230~1280℃, and the holding time to control the slab temperature to ≥1230℃ is ≥40min.

[0016] In the rolling process, a 2-stand roughing mill and a 7-stand finishing mill hot continuous rolling unit are used. The roughing mill finishing temperature R2DT is 1080–1130℃, and the cumulative reduction rate is ≥80%. The finishing mill finishing temperature FDT is 850–900℃, and the cumulative reduction rate is ≥85%. Constant speed rolling is used. The finishing mill F7 stand rolling speed v ≥6.5 m / s; the F7 stand crown C 40 10–30 μm, wedge-shaped W 40 The range is -10 to 10 μm.

[0017] In the cooling process, the strip steel is cooled in stages after exiting the F7 frame. The first stage uses centralized cooling at a cooling rate of ≥100℃ / s to 620-680℃. Then, the second stage is air-cooled for 8-12 seconds. After air-cooling, the third stage is cooled at a cooling rate of ≥30℃ / s to 490-550℃ for winding. After winding and unwinding, an insulation cover is placed on top for online tempering. The hot coil is kept at the heat for 60-90 minutes, then the insulation cover is removed and the coil is air-cooled to room temperature.

[0018] In the cooling process, the strip steel is cooled in stages after exiting the F7 frame. The first stage uses centralized cooling, cooling to 620-680°C at a cooling rate of 110-120°C / s. Then, the second stage is air-cooled for 8-12 seconds. After air-cooling, the third stage is cooled to 490-550°C at a cooling rate of 30-60°C / s before winding. After winding and unwinding, an insulation cover is placed on top for online tempering. The hot coil is kept at the heat for 60-90 minutes, then the insulation cover is removed and the coil is air-cooled to room temperature.

[0019] In the leveling step, the rolling force of the leveling machine is 500-800t, the bending roll force is 70-100t, and the leveling speed is 50-100m / min.

[0020] The functions and controls of each component in the hot-rolled wear-resistant steel plate provided by this invention are as follows:

[0021] C: 0.08%-0.13%. As a basic element in steel, C plays a very important role in improving the strength and hardness of steel. In order to obtain higher strength and hardness, the C content must be above 0.08%, but the C content cannot be too high. When the C content is ≥0.13%, the size of the Mao islands in the formed bainite is larger and the proportion is more, which is not conducive to improving the plasticity and toughness of the material.

[0022] Si: 0.60%-1.40%. Si has a strong solid solution strengthening effect, which can improve the strength of the material. At the same time, Si can inhibit the formation of cementite, which is beneficial to obtaining a fine-grained bainitic structure after rolling and cooling. However, if the Si content is too high, the red rust on the strip surface will be severe and difficult to remove, which is not conducive to the control of surface quality.

[0023] Mn: 1.60%~2.40%. As a strengthening element of steel, Mn can significantly improve the hardenability and strength of steel. In order to ensure that the tensile strength of the material is ≥1050MPa, the Mn content should be controlled above 1.60%. However, if the Mn content is >2.40%, it is easy to cause segregation in the center of the billet and is not conducive to the welding performance and forming performance of the material.

[0024] Ti: 0.05%–0.15%. As a key element in this invention, the high content of Ti serves two purposes: firstly, it refines the original austenite grains during heating; secondly, the Ti dissolved in the matrix during heating can precipitate a large amount of nano-sized TiC after cooling in the air-cooling section and during roll-up heat preservation, resulting in precipitation strengthening and improving the material's strength and hardness; furthermore, Ti can fix excess B, reducing the amount of FeB and other substances precipitated at grain boundaries, allowing them to disperse diffusely in the ferrite matrix, which is beneficial for improving the material's strength, hardness, and wear resistance. However, the Ti content cannot be too high. Considering that the C content in this invention is 0.08–0.15%, according to the solubility product formula, if the Ti content is greater than 0.15%, the Ti that cannot be completely dissolved in the matrix during heating will form a large amount of hard micron-sized TiC after rolling and cooling. Micron-sized TiC will become a crack initiation source, which is detrimental to the material's ductility, toughness, and cold bending forming performance. To fully utilize the precipitation strengthening effect of Ti, the content of Ti-3.42*N-3*SB must be no less than 0.040%. Considering that the corresponding C content in this invention is 0.08% to 0.13%, according to the solid solubility product formula, when the content of Ti-3.42*N-3*SB is greater than 0.14%, the total solid solution temperature of TiC is >1278℃. Ti that cannot be completely dissolved in the matrix during the heating process will form a large amount of hard micron-sized TiC after rolling and cooling. Micron-sized TiC will become a crack initiation source, which is not conducive to the material's plasticity, toughness, and cold bending forming performance.

[0025] B: 0.0008%~0.0030%. B, as another important element in this invention, can improve the stability of austenite. On the one hand, it can prevent the formation of pearlite in the air-cooling section; on the other hand, it can delay the transformation of austenite to ferrite, avoiding the problem of a large amount of soft ferrite forming and reduced material strength and hardness caused by the need to extend the air-cooling time to increase the amount of TiC precipitation and improve precipitation strengthening. Adding a certain amount of B and appropriately extending the air-cooling time can control the proportion of ferrite while increasing the amount and proportion of TiC precipitation, thus improving the precipitation strengthening effect.

[0026] Als: 0.020%-0.060%. Als is mainly used as a deoxidizer and can react with N to form AlN grain boundaries, which can refine the grains.

[0027] P and S, as impurity elements, can adversely affect the plasticity, formability, and weldability of steel. The lower their content, the better. Considering production cost factors, in actual production, P should be controlled at ≤0.012% and S at ≤0.005%.

[0028] O and N are harmful gaseous elements. Due to the extreme reactivity of Ti, they will preferentially react with O and N to precipitate, affecting the yield of Ti, the amount of TiC precipitated, and the precipitation enhancement effect. Based on the consideration of Ti yield and improving the precipitation enhancement effect of TiC, N: ≤0.0050%; O: ≤0.0030%.

[0029] The chemical composition of this invention adopts a low C, medium Si, high Mn, high Ti and B micro-alloying design, without adding expensive alloying elements such as Mo, Ni, Nb, V, etc., resulting in lower alloy cost.

[0030] In the manufacturing method of hot-rolled wear-resistant steel plate provided by this invention, the heating process takes into account the small austenite grain size and high Ti solid solution, adopts high-temperature heating, and emphasizes extending the holding time in the high-temperature section rather than the total time in the furnace. The purpose of high-temperature heating and the billet exiting the furnace at a temperature of 1230-1280°C is mainly to increase the proportion of Ti atoms dissolved in the matrix, creating conditions for the precipitation of TiC precipitates during the cooling and coiling process. Controlling the holding time of the billet temperature ≥1230°C for 30-50 minutes is to allow Ti atoms sufficient time to fully dissolve into the matrix, while avoiding excessively coarse austenite grains which are not conducive to improving strength, and excessively thick furnace-grown iron oxide scale which is not conducive to surface quality control.

[0031] In the rolling process, the roughing stage fully utilizes the characteristics of high temperature and large deformation to ensure sufficient recrystallization of austenite. Increasing the cumulative deformation in the non-recrystallized zone during the finishing stage, combined with a lower final rolling temperature, is beneficial for generating greater cumulative strain energy, increasing nucleation sites, refining the austenite grain size, and improving the grain size of austenite transforming into ferrite or bainite, thus enhancing the fine-grain strengthening effect. Controlling the finishing rolling speed to ≥6.5 m / s primarily aims to minimize the precipitation of micron-sized TiC in austenite and increase the amount of nano-sized TiC precipitated during the air cooling section and coiling process. Simultaneously, to control the strip shape quality at the finishing mill exit, a control strategy of small crown, small wedge shape, and constant speed rolling is adopted.

[0032] In terms of cooling process, this invention adopts a control strategy of segmented cooling + online tempering after coiling, which gives full play to the synergistic effect of three strengthening methods: fine grain strengthening, precipitation strengthening and phase transformation strengthening. This avoids the problem that a single continuous cooling process after rolling cannot simultaneously address precipitation strengthening (requiring high coiling temperature) and phase transformation strengthening (requiring low coiling temperature).

[0033] The first stage employs concentrated cooling and an increased cooling rate of over 100℃ / s primarily to enhance phase transformation undercooling, increase nucleation sites, and refine the grain size of ferrite formed from austenite transformation and bainite formed from retained austenite transformation. This is beneficial for improving material strength and cold bending performance. Rapid cooling to 620–680℃ is mainly aimed at this temperature range, which is near the nose temperature of the PTT curve. This allows for the rapid formation of a larger proportion of nanoscale TiC precipitates, fully leveraging the precipitation strengthening effect and the wear resistance enhancement effect of hard TiC.

[0034] The second stage of air cooling time is controlled between 8 and 12 seconds. If the air cooling time is less than 8 seconds, the amount of TiC precipitation is relatively small. If the air cooling time is greater than 12 seconds, the proportion of ferrite gradually increases and the grain size increases. The proportion of TiC precipitates is large, but the increase in material strength due to precipitation strengthening is less than the decrease in phase transformation strengthening due to the proportion of ferrite. This is not conducive to improving the material's strength, hardness, and wear resistance. In addition, the laminar flow cooling line has a limited length and does not meet the conditions for long-term air cooling. The initial air-cooling temperature for the second stage is controlled between 620 and 680℃. If the initial air-cooling temperature is >680℃, the undercooling is small and the phase transformation driving force is low. When boron can significantly inhibit the formation of ferrite, on the one hand, austenite is difficult to transform into ferrite, resulting in lath bainite after cooling. Although the strength and hardness are guaranteed, it is not conducive to cold bending performance. On the other hand, with a lower proportion of ferrite, the amount of TiC precipitates within the grains is also lower, and they are not in the optimal precipitation temperature range for TiC precipitates, resulting in a lower proportion of TiC precipitates, which is not conducive to improving the effect of precipitation strengthening on the material strength. If the initial air-cooling temperature is too low, especially <600℃, although a bainite structure and a better phase transformation strengthening effect can be obtained, the amount of TiC precipitates will be reduced, reducing the precipitation strengthening effect, which is not conducive to improving the final material strength and wear resistance.

[0035] The third stage involves rapid cooling to 490–550°C at a cooling rate of ≥30°C / s, followed by medium-temperature coiling. This process yields a fine bainitic structure, maximizing the strength-enhancing effect of phase transformation. Furthermore, compared to low-temperature coiling (≤300°C), medium-temperature coiling offers significant advantages in shape control for thin-gauge, high-strength hot-rolled strip steel, improving the yield rate. Simultaneously, online tempering is performed in conjunction with a post-coiling heat treatment process. This allows unprecipitated TiC from the air-cooling stage to continue precipitating, further enhancing precipitation strengthening. Additionally, it facilitates uniform control of temperature, mechanical properties, and residual stress along the length and width of the hot-rolled strip, further improving shape quality and flatness.

[0036] This invention employs a leveling process after coiling, primarily to improve the strip shape and the uniformity of its properties in the width direction. While maintaining the strip shape, a control strategy of using small leveling force and large bending roll force is prioritized. The main purpose is to avoid exacerbating the work hardening of the strip, which is detrimental to the uniformity of its properties in the width direction. Simultaneously, to control the stability of the strip shape during leveling, the leveling rate should not be too fast, and should be controlled between 50 and 100 m / min.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1) The chemical composition of this invention adopts a low C, medium Si, high Mn, high Ti and B micro-alloying design. Compared with the existing 1000MPa grade bainitic wear-resistant steel, on the one hand, it does not add expensive alloying elements such as Mo, Ni, Nb and V, so the alloy cost is lower. On the other hand, it adopts the TMCP process, which eliminates the quenching and tempering heat treatment process, shortens the process flow, and reduces the process cost by 1000 to 1200 yuan / t compared with the quenching and tempering heat treatment process.

[0039] 2) This invention employs a segmented cooling process, which can fully leverage the strength-enhancing effects of both precipitation strengthening and phase transformation strengthening. This solves the problem of simultaneously achieving high precipitation strengthening and high phase transformation strengthening effects in bainitic steel produced by a single-stage continuous cooling process. Compared to bainitic steel produced by traditional hot rolling mills, the material produced by this invention has a tensile strength ≥1050MPa, a hardness ≥310HB, higher strength and hardness, a yield strength ratio ≤0.70, and a cold bending performance of 180° with D=1a meeting the requirements. These yield strength ratios are lower than those of existing bainitic steels (>0.87), which is beneficial for improving the material's cold bending performance.

[0040] 3) The heat-resistant wear-resistant steel plate produced by this invention has an unevenness control of ≤5mm / m after cross-cutting and leveling, and a plate shape qualification rate of ≥95%, which better meets the requirements of downstream users. Attached Figure Description

[0041] Figure 1 A typical metallographic image of the hot-rolled wear-resistant steel in Example 1;

[0042] Figure 2 A typical metallographic image of the hot-rolled wear-resistant steel in Example 2;

[0043] Figure 3 A typical metallographic image of the hot-rolled wear-resistant steel in Example 3;

[0044] Figure 4 A typical metallographic image of the hot-rolled wear-resistant steel in Comparative Example 1;

[0045] Figure 5 A typical metallographic image of the hot-rolled wear-resistant steel in Comparative Example 2;

[0046] Figure 6 A typical metallographic image of the hot-rolled wear-resistant steel in Comparative Example 3;

[0047] Figure 7 A typical metallographic image of the hot-rolled wear-resistant steel in Comparative Example 5;

[0048] Figure 8 A typical metallographic image of the hot-rolled wear-resistant steel in Comparative Example 6; Detailed Implementation

[0049] The present invention provides a hot-rolled wear-resistant steel plate comprising the following chemical composition by weight percentage: C: 0.08-0.13%; Si: 0.60-1.40%; Mn: 1.60-2.40%; Ti: 0.050-0.15%; B: 0.0008-0.0030%; Als: 0.020-0.60%; P: ≤0.012%; S: ≤0.005%; N: ≤0.0050%; O: ≤0.0030%; the remainder being Fe and unavoidable inclusions; and simultaneously satisfying: 0.040% ≤ Ti - 3.42 * N - 3 * SB ≤ 0.14%.

[0050] The manufacturing method of the hot-rolled wear-resistant steel plate includes the following steps: smelting, continuous casting, heating, rolling, cooling, coiling, leveling, and slitting.

[0051] In the heating step, the final temperature of the second heating stage is ≥1200℃, the heat soaking time is ≥30min, the slab exit temperature is 1230~1280℃, and the holding time to control the slab temperature to ≥1230℃ is ≥40min.

[0052] In the rolling process, a 2-stand roughing mill and a 7-stand finishing mill hot continuous rolling unit are used; the roughing mill finishing temperature R2DT is 1080–1130℃, and the cumulative reduction rate is ≥80%; the finishing mill finishing temperature FDT is 850–900℃, and the cumulative reduction rate is ≥85%; constant speed rolling is used; the finishing mill F7 stand rolling speed v ≥6.5 m / s; the F7 stand crown C 40 10–30 μm, wedge-shaped W 40 The range is -10 to 10 μm.

[0053] In the cooling process, the strip steel is cooled in stages after exiting the F7 frame. The first stage uses centralized cooling, cooling to 620-680°C at a cooling rate of 110-120°C / s. Then, the second stage is air-cooled for 8-12 seconds. After air-cooling, the third stage is cooled to 490-550°C at a cooling rate of 30-60°C / s before winding. After winding and unwinding, an insulation cover is placed on top for online tempering. The hot coil is kept at the heat for 60-90 minutes, then the insulation cover is removed and the coil is air-cooled to room temperature.

[0054] In the leveling step, the rolling force of the leveling machine is 500-800t, the bending roll force is 70-100t, and the leveling speed is 50-100m / min.

[0055] The present invention will now be described in detail with reference to the embodiments.

[0056] The chemical composition of the examples and comparative examples is shown in Table 1, the rolling process parameters are shown in Table 2, the cooling process parameters are shown in Table 3, the leveling process parameters and the flatness of the plate are shown in Table 4, the microstructure type is shown in Table 5, the mechanical properties are shown in Table 6, and the wear resistance is shown in Table 7.

[0057] Table 1 Chemical composition (mass percentage, wt%) of the examples and comparative examples

[0058]

[0059]

[0060] Table 2 Rolling process parameters for the examples and comparative examples

[0061]

[0062]

[0063] Table 3 Cooling process parameters for the examples and comparative examples

[0064]

[0065] Table 4. Leveling process parameters and flattening plate shape qualification rate of the examples and comparative examples.

[0066]

[0067]

[0068] Note: Flatness of the cut plate ≤ 8mm / m is considered a qualified finished product. Plate shape qualification rate = weight of qualified cut plate / weight of hot roll.

[0069] Table 5. Tissue types of the examples and comparative examples

[0070]

[0071] Table 6 Mechanical properties of the embodiments and comparative examples

[0072]

[0073]

[0074] Table 7. Wear resistance properties of the examples and comparative examples

[0075] Example 1 2.6804 1.24 Example 2 2.6631 1.25 Example 3 2.6534 1.26 Comparative Example 1 3.3321 1.00 Comparative Example 2 3.1277 1.07 Comparative Example 3 3.4403 0.97 Comparative Example 4 2.7413 1.21 Comparative Example 5 2.7089 1.23 Comparative Example 6 2.8388 1.17 Comparative Example 7 2.2608 1.47 Comparative Example 8 2.8912 1.15 Comparative Example 9 2.4956 1.34

[0076] Note: Abrasive wear tests were conducted using an MLS-225 wet rubber wheel testing machine. The sample dimensions for the abrasive wear test were 57mm (length) × 25.5mm (width) × 2.5mm (thickness), with the 57mm × 25.5mm surface being the wear surface, which was polished. Test parameters were as follows: rubber wheel hardness 60HS, rubber wheel speed 240 r / min, abrasive solution of quartz sand and water in a 1:1 ratio, quartz sand particle size 20-40 mesh, and load 170N. First, the wear surface of the sample was pre-ground at 1000 r, and the weight m1 after pre-ground was recorded. Then, it was fine-ground for 60 min, and the weight m2 after fine-ground was recorded. Both the pre-ground and fine-ground samples were ultrasonically cleaned, and the weight was measured using an electronic balance (accuracy 0.1 mg). The wear loss weight Δm(m1-m2) was used as the main parameter for evaluating the material's wear resistance; the smaller the wear loss weight, the better the material's wear resistance. Three samples of each test material were selected for abrasive wear test under the same test conditions, and the average weight loss of the three samples was taken as the final weight loss.

[0077] The relative wear resistance is based on the wear loss weight of Comparative Example 1. Relative wear resistance = wear loss weight of Example or Comparative Example / wear loss weight of Comparative Example 1.

[0078] The above detailed description of a hot-rolled wear-resistant steel plate and its manufacturing method with reference to the embodiments is illustrative rather than limiting. Several embodiments can be listed according to the defined scope. Therefore, changes and modifications without departing from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A hot-rolled wear-resistant steel plate, characterized in that, The chemical composition includes the following weight percentages: C: 0.08~0.13%; Si: 0.60~1.40%; Mn: 1.60~2.40%; Ti: 0.050~0.15%; B：0.0008~0.0030%； Als: 0.020~0.060%; P：≤0.012%； S: ≤0.005%; N: ≤0.0050%; O: ≤0.0030%; the remainder is Fe and unavoidable inclusions; and must simultaneously satisfy: 0.040% ≤ Ti - 3.42 * N - 3 * SB ≤ 0.14%; The metallographic structure of the hot-rolled wear-resistant steel plate consists of granular bainite and nano-sized precipitates, with the nano-sized precipitates having a size ≤20nm and a volume fraction of 0.15~0.22%.

2. The hot-rolled wear-resistant steel plate according to claim 1, characterized in that, The hot-rolled wear-resistant steel plate has a yield strength ≥700MPa, tensile strength ≥1050MPa, yield ratio ≤0.70, and elongation A. 50 ≥16%, hardness ≥310HB, cold bending performance reaches 180°, D=1a qualified, flatness control of flat plate ≤5mm / m, and plate shape qualification rate ≥95%.

3. The method for manufacturing hot-rolled wear-resistant steel plate as described in claim 1 or 2, characterized in that, The manufacturing method includes the following steps: smelting, continuous casting, heating, rolling, cooling, coiling, leveling, and slitting.

4. The manufacturing method according to claim 3, characterized in that, In the heating step, the final temperature of the second heating stage is ≥1200℃, the heating time is ≥30min, the slab exit temperature is 1230~1280℃, and the holding time to control the slab temperature to ≥1230℃ is ≥40min.

5. The manufacturing method according to claim 3, characterized in that, In the rolling process, a 2-stand roughing mill and a 7-stand finishing mill hot continuous rolling unit are used for rolling; the roughing mill finishing temperature R2DT is 1080~1130℃, and the cumulative reduction rate is ≥80%; the finishing mill finishing temperature FDT is 850~900℃, and the cumulative reduction rate is ≥85%; constant speed rolling is used; the finishing mill F7 stand rolling speed v ≥6.5m / s; the F7 stand crown C 40 10~30μm, wedge-shaped W 40 The range is -10 to 10 μm.

6. The manufacturing method according to claim 3, characterized in that, In the cooling process, the strip steel is cooled in stages after exiting the F7 frame. The first stage uses centralized cooling at a cooling rate of ≥100℃ / s to 620~680℃. Then, the second stage is air cooling for 8~12s. After air cooling, the third stage is cooled at a cooling rate of ≥30℃ / s to 490-550℃ for winding. After winding and unwinding, an insulation cover is placed on top for online tempering. The hot coil is kept at the heat for 60~90min, then the insulation cover is removed and the coil is air cooled to room temperature.

7. The manufacturing method according to claim 4, characterized in that, In the cooling process, the strip steel is cooled in stages after exiting the F7 frame. The first stage uses centralized cooling, cooling to 620-680℃ at a cooling rate of 110-120℃ / s. Then, the second stage is air cooling, with an air cooling time of 8-12s. After air cooling, the third stage is cooled to 490-550℃ at a cooling rate of 30-60℃ / s before winding. After winding and unwinding, an insulation cover is placed on top for online tempering. The hot coil is kept at the heat for 60-90 minutes, then the insulation cover is removed, and the coil is air cooled to room temperature.

8. The manufacturing method according to claim 4, characterized in that, In the leveling step, the rolling force of the leveling machine is 500-800t, the bending roll force is 70-100t, and the leveling speed is 50-100m / min.

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