Dual-phase wear-resistant steel plate with good formability and high wear resistance and manufacturing method therefor

Abstract

Disclosed in the present invention is dual-phase wear-resistant steel plate with good formability and high wear resistance, comprising, in addition to Fe and inevitable impurities, the following components in percentage by weight: C: 0.16-0.50%, Si: 0.05-1.5%, Mn: 0.40-2.0%, Cr: 0.2-0.8%, Ti: 0.4-1.0%, N: ≤0.005%, P: ≤0.030%, S: ≤0.005%, and O: ≤0.004%. The contents of these elements simultaneously satisfy the following relationship: 0.06%≤C-Ti / 3.98≤0.25%. During calculation, each element symbol in the formula is substituted with the weight percentage of the corresponding element in the steel plate. The steel plate features a combination of low yield strength, high ductility, and high wear resistance and is particularly suitable for manufacturing components such as concrete mixer truck drums that require high wear resistance and good formability. Further disclosed in the present invention is a method for manufacturing the steel plate.

Description

Easily-formed high-wear-resistant dual-phase wear-resistant steel plate and manufacturing method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of wear-resistant steel plate and its manufacturing technology, in particular to an easily-formed high-wear-resistant dual-phase wear-resistant steel plate and a manufacturing method thereof. BACKGROUND

[0002] Wear-resistant steel plates are widely used in the manufacture of dump trucks, mine cars and other mechanical parts used in wear environments, and the working conditions of these devices are harsh, requiring the steel plates used to have high wear resistance.

[0003] The microstructure of conventional wear-resistant steel plates is usually single-phase martensitic steel plates, and the main method to improve the wear resistance of the steel plates is to increase the hardness of the steel plates. However, after the hardness of the steel plates is increased, the yield strength of the steel plates is increased but the elongation of the steel plates is decreased, which greatly increases the processing difficulty and reduces the formability of the steel plates, making it difficult to meet the processing and use requirements of some industries.

[0004] Chinese patent CN103146997A discloses a low-alloy high-toughness wear-resistant steel plate and a manufacturing method thereof. The chemical composition (wt%) of the steel plate is as follows: C: 0.08-0.20%, Si: 0.10-0.60%, Mn: 1.00-2.00%, B: 0.0005-0.0040%, Cr≤1.50%, Mo≤0.80%, Ni≤1.50%, Nb≤0.080%, V≤0.080%, Ti≤0.060%, Al: 0.010-0.080%, Ca: 0.0010-0.0080%, N≤0.0080%, O≤0.0080%, H≤0.0004%, P≤0.015%, S≤0.010%, and satisfies 0.20%≤(Cr / 5+Mn / 6+50B)≤0.55%, 0.02%≤(Mo / 3+Ni / 5+2Nb)≤0.45%, 0.01%≤(Al+Ti)≤0.13%, and the rest is Fe and inevitable impurities. By reducing the content of carbon and alloying elements, fully utilizing the refining and strengthening characteristics of Nb, Ti and other micro-alloying elements, and through TMCP process, the wear-resistant steel plate has high strength and hardness, good toughness, easy welding, excellent wear resistance, and is suitable for various easily-worn parts of mechanical equipment. The microstructure is fine martensite and residual austenite, the volume fraction of the residual austenite is ≤5%, the Brinell hardness of the steel plate is greater than 400HBW, the Charpy V-type longitudinal impact energy at -40℃ is greater than 60, the tensile strength is ≥1200MPa, and the elongation is ≤16%.

[0005] Chinese patent CN114959503A discloses a wear-resistant steel plate and its manufacturing method and product. The wear-resistant steel plate has the following chemical composition in mass percentage: C: 0.1-0.25%; Si: 0.1-0.25%; Mn: 0.3-0.5%; P: 0-0.01%; S: 0-0.002%; Cr: 0.05-0.1%; Ni: 0.01-0.3%; Mo: 1-1.5%; the balance is iron and other inevitable impurities. The microstructure of the wear-resistant steel plate is martensite. The Brinell hardness of the wear-resistant steel plate is HBW430-HBW500. The yield strength is >1150MPa, and the elongation is 8-16%. By introducing micron-sized TiC particles into the structure, the wear resistance of the steel plate can be significantly improved under the condition of the same hardness, but the plasticity and toughness of the martensitic wear-resistant steel will be deteriorated.

[0006] Chinese patent CN104357758A discloses an ultra-hard particle reinforced martensitic wear-resistant steel plate and its manufacturing method. The chemical composition of the martensitic wear-resistant steel plate is as follows in weight percentage: C: 0.20-0.40%; Mn: 0.50-1.00%; Si: 0.30-0.60%; Cr: 0.50-0.80%; Ni: 0.40-0.60%; Mo: 0.30-0.40%; Ti: 0.40-0.80%; Cu: 0.30-0.50%; B: 0.0005-0.003%; S≤0.005%; P≤0.015%; the balance is Fe and inevitable impurity elements. After rolling, the steel plate obtains TiC precipitated phase with a volume fraction of 0.5-1.5%, and the average size of the precipitated phase particles is 1μm. The Brinell hardness of the steel plate is HBW400-500, and the wear resistance reaches 1.5 times that of Hardox450, but the elongation is lower, below 11%.

[0007] Chinese invention patent CN117004867A discloses a manufacturing method of a high-toughness TiC particle reinforced martensitic wear-resistant steel plate. The chemical composition of the steel plate is as follows in weight percentage: C: 0.20-0.40%; Mn: 0.50-1.00%; Si: 0.20-0.30%; Mo: 0.20-0.50%; Ti: 0.30-0.80%; Cr: 0.50-1.00%; N≤0.004%; S≤0.002%; P≤0.008%; the balance is Fe and inevitable impurity elements. In the manufacturing method of the steel plate, the protective casting adopts a reduced casting temperature, the rolling adopts high-permeability rolling and sets the rolling compression ratio, and the size of the TiC particles is controlled to be 1.0-2.5μm. The wear resistance reaches 1.5 times that of the ordinary wear-resistant steel of the same hardness level, but the elongation is only 10-13%.

[0008] Changing the matrix structure can reduce the yield strength of wear-resistant steel and improve the plasticity of wear-resistant steel. For example:

[0009] Chinese patent CN104388821 discloses a TiC particle reinforced complex phase structure high plasticity wear-resistant steel plate and a manufacturing method. The chemical composition of the steel plate is as follows: C: 0.20-0.40%; Mn: 1.00-2.50%; Si: 0.80-1.50%; Ni: 0.20-0.60%; Mo: 0.15-0.50%; Ti: 0.40-0.80%; B: 0.0005-0.003%; S≤0.005%; P≤0.015%; the balance is Fe and unavoidable impurity elements. After rolling, a complex phase structure of granular bainite, lath martensite and TiC particles is obtained, part of the martensite structure is replaced by bainite structure, the yield strength of the steel plate is still above 980 MPa, but the elongation of the steel plate has not been essentially improved, and the elongation is ≤14%.

[0010] Chinese patent CN108118257A discloses a TiC particle reinforced ferrite / bainite based wear-resistant steel plate and a manufacturing method. The chemical composition of the steel plate is as follows: Mn: 0-2.0%, Si: 0.30-0.60%, Mo: 0-1.0%, Ti: 0.4-0.8%, S≤0.030%, P≤0.030%, C is 0.07+Ti / 4; the balance is Fe and unavoidable impurity elements. The matrix structure of the wear-resistant steel plate is mainly ferrite / bainite, and micron-sized TiC particles with a volume fraction of 0.5-3% are uniformly distributed. Although the steel plate has low strength and high elongation, the yield strength is only 500-600 MPa, and the hardness and wear resistance are significantly reduced, and the abrasive wear performance only reaches the level of NM360.

[0011] Chinese patent CN114959489A discloses a ferrite / martensite wear-resistant steel plate and a manufacturing method. The chemical composition of the steel plate is as follows: C 0.14-0.18%, Si 0.10-0.30%, Mn 0.90-1.10%, Cr 0.080-0.30%, Nb 0.005-0.015%, P≤0.025%, S≤0.010%, Ti 0.010-0.030%, Al 0.010-0.050%, Ca 0.001-0.004%, B 0.001-0.003%, the balance is Fe and unavoidable impurities. By introducing ferrite, the yield strength of the steel plate is reduced to ≤670 MPa, and the elongation is ≥14%, but the wear resistance of the steel plate is only comparable to ordinary NM300.

[0012] NM300TP is a ferrite + martensite + residual austenite complex phase steel, which is widely used in the tank body of concrete mixing truck. A certain content of ferrite can reduce the yield strength of the steel plate to a certain extent, so that it has good processing performance and can meet the design and manufacture of concrete mixing tank body.

[0013] The Chinese patent CN117051305A discloses a production method of NM300TP steel and NM300TP steel, and the mass percentage of the components is: C: 0.10-0.16%; Si: 1.0-1.5%; Mn: 1.5-2.0%; P≤0.020%; S≤0.005%; Als: 0.4-0.6%; Ti≤0.030%; the balance is Fe and other unavoidable impurities. The yield strength of the steel plate is less than 700 MPa, but the wear resistance can only be equivalent to NM300.

[0014] At present, due to the lightweighting needs of the mixing truck, it is required to realize higher wear resistance of the steel under the same forming conditions, so as to improve the service life of the steel plate or thin the steel plate. Based on the research findings, the existing steel plate is difficult to have both good processing forming property (low yield strength, high elongation) and high wear resistance. SUMMARY

[0015] The purpose of the present application is to provide a dual-phase wear-resistant steel plate with easy forming and high wear resistance and a manufacturing method thereof, so as to obtain a steel plate with low yield strength, high elongation and high wear resistance, and solve the problem that the existing steel plate cannot have both forming property and high wear resistance. Preferably, the yield strength of the steel plate of the present application is ≤800 MPa, the elongation is ≥18%, the impact energy at-40℃ is ≥20 J, the Brinell hardness is 270-330 HBW, and the abrasive wear performance is equivalent to NM450.

[0016] To achieve the above purpose, the technical scheme of the present application is:

[0017] A dual-phase wear-resistant steel plate, in addition to containing Fe and unavoidable impurities, also contains the following components in terms of weight percentage: C: 0.16-0.50%, preferably 0.25-0.45%, Si: 0.05-1.5%, preferably 0.05-0.5%, Mn: 0.40-2.0%, Cr: 0.2-0.8%, Ti: 0.4-1.0%, N≤0.005%, P≤0.030%, S≤0.005%, O≤0.004%; and the above element contents simultaneously satisfy the following relationship:

[0018] 0.06% < C - Ti / 3.98 < 0.25%, preferably 0.14% < C - Ti / 3.98 < 0.21%, calculated by substituting the weight percentage of each element in the steel plate into the formula. For example, when the content of C in the steel plate is 0.25%, 0.25% is substituted into the formula for calculation.

[0019] Preferably, the steel plate further comprises one or a combination of Mo, V, Nb, Cu, Ni, B, Al, Ca, RE, wherein Mo < 0.5%, V < 0.06%, Nb < 0.050%, Cu < 0.5%, Ni < 0.5%, B < 0.003%, Al < 0.06%, Ca < 0.004%, RE < 0.005%.

[0020] Preferably, the steel plate comprises the following ingredients in weight percentage: C: 0.25-0.45%, Si: 0.05-0.5%, Mn: 0.40-2.0%, Cr: 0.2-0.8%, Ti: 0.4-1%, N < 0.005%, P < 0.030%, S < 0.005%, O < 0.004%, and the balance of Fe and inevitable impurities.

[0021] Preferably, the microstructure of the steel plate of the present application comprises 20-60% ferrite + 40-80% martensite + 0.4-2.0% TiC particles, and the volume fraction of the three is more than 99%.

[0022] According to some embodiments of the present application, a small amount of other carbides also exist in the steel plate of the present application. In these embodiments, in addition to the ferrite, martensite and TiC particles described above, the balance of the microstructure of the steel plate is other carbides, such as NbC, VC, ε-carbide, etc., with a content of less than 1%.

[0023] Preferably, in the microstructure of the above-mentioned steel plate, the average particle size of the TiC particles is 0.5-10 μm or the volume fraction of the TiC particles with a particle size of 0.5-10 μm in the steel plate accounts for more than 95% of the total volume fraction of all TiC particles.

[0024] Unless otherwise specified, the content of each phase in the microstructure of the steel plate of the present application is the volume fraction.

[0025] Preferably, the steel plate of the present application has a yield strength of < 800 MPa, an elongation of > 18%, an impact energy at -40°C of > 20 J, a Brinell hardness of 270-330 HBW, and abrasive wear performance comparable to NM450.

[0026] Preferably, the properties of the steel plate of the present application satisfy at least one of the following: yield strength of 600-800 MPa, preferably 620-800 MPa; elongation of 18.0%-22.0%, preferably 19.0-22.0%; impact energy at -40℃ of 20-50 J, preferably 30-50 J; Brinell hardness of 270-330 HBW, preferably 295-330 HBW; and abrasive wear performance of the steel plate of 0.95-1.25 times, preferably 1.06-1.25 times, that of NM450.

[0027] In the component design of the steel plate of the present application:

[0028] C: C is an essential element in steel and also an important element for improving the Brinell hardness and wear resistance of the steel. Since C in the matrix can chemically react with Ti to form TiC particles, it consumes part of the C in the matrix, so that the actual remaining C content in the matrix decreases. By controlling the C content in the matrix, the present application ensures that the Brinell hardness of the steel is about 300 HBW. In addition, due to the partitioning of carbon, C in the steel will be enriched in the martensite, the higher the content of martensite, the higher the strength of the martensite, and the greater the difference in strength between the two phases, leading to deterioration of the toughness of the steel grade. The present application controls 0.06%≤C-Ti / 3.98≤0.25%, ensures that the carbon content in the martensite is <0.5%, and weakens the strength difference between ferrite and martensite, ensuring the toughness of the steel grade. It not only ensures that the steel has appropriate Brinell hardness and toughness, but also ensures that a certain amount of TiC particles can be generated to improve wear resistance. If C-Ti / 3.98 in the steel is <0.06%, the Brinell hardness of the steel is too low, the matrix is not enough to support the TiC particles during the wear process, the TiC particles are concave, and the wear resistance is reduced; if C-Ti / 3.98 in the steel is >0.25%, the Brinell hardness of the steel is too high, the matrix is brittle, and the TiC particles are easily peeled off, reducing the wear resistance. Therefore, the total C content in the steel plate of the present application is controlled at 0.16-0.50%, preferably 0.25-0.45%, more preferably 0.27-0.39%, which not only ensures that the steel has appropriate hardness, but also ensures that sufficient TiC particles can be generated to improve wear resistance.

[0029] Si: The presence of 0.05% or more of Si in the steel plate can have a good deoxidizing effect, and Si is a ferrite stabilizing element that can promote the formation of ferrite during post-rolling cooling or during quenching and holding. However, if the Si content exceeds 1.5%, the hot rolling force will increase significantly, making it difficult to produce on site. Therefore, the silicon content in the steel plate of the present application is controlled at 0.05-1.5%, preferably 0.05-0.5%, more preferably 0.10-0.35%.

[0030] Mn: Mn element can improve the hardenability of the steel when it is above 0.40%, but when the content of Mn exceeds 2.0%, segregation and MnS inclusions are easily generated, which deteriorate the plasticity and toughness of the wear-resistant steel. Therefore, the content of Mn in the steel plate of the present application is controlled to be 0.40-2.0%, preferably 0.80-1.6%.

[0031] Cr: Cr element can improve the hardenability of the steel when it is above 0.2%, which is beneficial to form martensite structure during quenching; but Cr is a noble metal element, and high content of Cr can significantly increase the cost. Therefore, the content of Cr in the present application is controlled to be 0.2-0.8%, preferably 0.3-0.6%.

[0032] Ti: Ti element is one of the key elements in the present application, and Ti can react with C element to form TiC. When the content of Ti is low, the precipitation temperature of TiC is low, and the precipitated TiC is difficult to grow up, with a size of nanometer or <0.5 μm, which has no obvious effect on the wear resistance. Only when the content of Ti is above 0.4%, TiC can precipitate in the liquid phase and high-temperature solid phase during continuous casting, and TiC particles with a size of 0.5-10 μm and a volume fraction of above 0.4% can be formed. The hardness of the micron-sized TiC particles can reach 3200 HV, which is much higher than the steel matrix. During the wear process, the TiC particles can effectively prevent the sliding of abrasive particles on the steel surface, thereby significantly improving the wear resistance of the material. When the content of Ti exceeds 1%, the volume fraction of TiC particles exceeds 2%, and the particles are severely coarsened, with a size of above 10 μm, which seriously damages the plasticity and toughness of the steel plate. Therefore, the content of Ti in the present application is controlled to be 0.4-1.0%, preferably 0.55-0.9%.

[0033] N: The content of N element is strictly controlled in the present application. When the content of N exceeds 0.005%, coarse precipitate particles are easily formed, which deteriorate the toughness. Therefore, the content of N in the present application is controlled to be ≤0.005%, preferably ≤0.0038%.

[0034] P, S and O: P, S and O are impurity elements which affect the plasticity and toughness of the steel. In the present application, the content of P is controlled to be ≤0.030%, preferably ≤0.025%, the content of S is controlled to be ≤0.0050%, preferably ≤0.0042%, and the content of O is controlled to be ≤0.0040%, preferably ≤0.0034%.

[0035] Preferably, the above-mentioned steel plate of the present application further comprises one or a combination of Mo, V, Nb, Cu, Ni, B, Al, Ca and RE, wherein Mo ≤0.5%, V ≤0.06%, Nb ≤0.050%, Cu ≤0.5%, Ni ≤0.5%, B ≤0.003%, Al ≤0.06%, Ca ≤0.004%, and RE ≤0.005%.

[0036] Mo: Mo element can improve the hardenability of steel, which is beneficial to form martensite structure during quenching; however, too high Mo content will lead to a significant increase in cost. Therefore, the Mo content in the steel plate is controlled to be ≤0.50%, preferably below 0.20%.

[0037] V: V element can refine the grain and improve the hardenability of steel, but too high V content will also lead to a significant increase in cost. Therefore, the V content in the steel plate is controlled to be ≤0.06%, preferably below 0.03%.

[0038] Nb: Nb is a micro-alloying element, which forms nanoscale precipitates with C, N and other elements to inhibit the growth of austenite grains during heating; Nb can increase the recrystallization critical temperature and expand the production window, but too high Nb content will lead to a significant increase in cost. Therefore, the niobium content in the steel plate is controlled to be ≤0.050%, preferably below 0.025%.

[0039] Cu: Cu element can produce certain precipitation strengthening effect during tempering, in addition, adding a certain amount of Cu element can improve the corrosion resistance of steel. Therefore, the Cu content in the steel plate is controlled to be ≤0.50%.

[0040] Ni: Ni element has the effect of promoting plastic flow, improving the plasticity and toughness of steel; but too high Ni content will lead to an increase in carbon equivalent, which will deteriorate the welding performance, and Ni is a noble metal, which will increase the cost. Therefore, the Ni content in the steel plate is controlled to be ≤0.50%, preferably below 0.25%.

[0041] B: A small amount of B can improve the hardenability of steel and increase the strength of steel; however, more than 0.0030% B is easy to segregate and form carbon boride, which seriously deteriorates the toughness and welding performance of the steel plate. Therefore, the boron content in the steel plate is controlled to be ≤0.0030%, preferably below 0.0020%.

[0042] Al: Al can refine the grain and improve the impact toughness as a deoxidizer, but Al content exceeding 0.06% is easy to produce Al oxide inclusion defects, therefore, the Al content in the steel plate is controlled to be ≤0.06%, preferably below 0.05%.

[0043] Ca: Ca element can act as a purifying agent during steel smelting process, which improves the toughness of steel; however, Ca content exceeding 0.004% is easy to form larger size Ca compounds, which will deteriorate the toughness. Therefore, the Ca content in the steel plate is controlled to be ≤0.004%, preferably below 0.0036%.

[0044] RE: Rare earth elements can improve the morphology of inclusions in steel, making the inclusions more fine and dispersed, especially for the high Ti component steel of the present application, which can significantly improve the size and morphology of TiN inclusions, and improve the toughness and fatigue performance of the steel. However, too much rare earth element leads to increased cost. Therefore, the content of RE is controlled to be ≤0.005%, for example, 0.001-0.005%.

[0045] The component design of the present application controls the C-Ti / 3.98 range between 0.06-0.25%, controls the volume fraction of TiC particles in the matrix to be more than 0.4%, for example, 0.4-2.0%, and controls the average particle size of TiC particles to be 0.5-10 μm or the volume fraction of TiC particles with a particle size of 0.5-10 μm in the steel plate to be more than 95% of the total volume fraction of TiC particles, so as to control the Brinell hardness of the steel to be around 300 HBW, inhibit the depression and peeling of TiC particles during wear process, and fully play the effect of TiC particles in improving the wear resistance of the steel. Preferably, the steel plate of the present application has a ferrite + martensite dual-phase structure, in which the carbon content in the martensite is <0.5%, which weakens the strength difference between ferrite and martensite, ensures good toughness and plasticity of the steel grade, and reduces the yield strength of the steel plate and improves the formability.

[0046] Another aspect of the present application provides a method for manufacturing the bidirectional wear-resistant steel plate described above.

[0047] According to an embodiment of the present application, the method for manufacturing the bidirectional wear-resistant steel plate of the present application includes an online two-stage cooling, specifically including the following steps:

[0048] 1) Smelting and casting

[0049] Based on the above-mentioned components, the slab is smelted and cast;

[0050] 2) Heating

[0051] Preferably, in the heating step, the heating temperature is 1200-1250℃, and after the surface temperature of the slab reaches 1200-1250℃, the temperature is maintained for >1.5h, preferably ≤3.0h;

[0052] 3) Rolling

[0053] Preferably, in the rolling step, the finish rolling temperature is 840-930℃, and a steel strip is obtained;

[0054] 4) Cooling and coiling

[0055] Preferably, in the cooling and coiling step, the strip is subjected to a segmented controlled cooling, cooled to a stop cooling temperature of 600-700℃ at a first cooling rate of ≥50℃ / s, preferably ≤150℃ / s, and then air-cooled for 3-10s; and then cooled to a final cooling temperature of <200℃ at a second cooling rate of ≥50℃ / s, preferably ≤150℃ / s, and then the strip enters the coiler for coiling.

[0056] 5) Heat treatment

[0057] Preferably, the heat treatment comprises a tempering treatment, wherein the tempering temperature is 180-240℃, and the tempering holding time is ≥5min, preferably ≤30min.

[0058] In the above method of the present application:

[0059] In the slab heating process, the heating temperature is above 1200℃, and the holding time is >1.5h, in order to ensure that the alloying elements are fully solid-solved; when the heating temperature exceeds 1250℃, the solid solubility of Ti increases with the increase of the heating temperature, and the micron-sized TiC particles produced during continuous casting are re-solid-solved, so that the TiC particles are reduced, which is not conducive to the improvement of wear resistance.

[0060] The finish rolling temperature is controlled at 840-930℃, in order to refine the austenite grains.

[0061] The present application adds a relatively high Ti content in the composition, which is not conducive to the formation of ferrite; therefore, a relatively low base carbon content (C-Ti / 3.98≤0.25%) is designed, and the addition of Si element is combined to promote the formation of ferrite during cooling, and the strip is subjected to controlled cooling after rolling, i.e. the cooling mode is specified and the stable cooling rate is controlled. Specifically, the strip is cooled to a stop cooling temperature of 600-700℃ at a first cooling rate of ≥50℃ / s, and then air-cooled for 3-10s. The stop cooling temperature is controlled at 600-700℃, and then air-cooled for 3-10s, in order to generate a certain amount of ferrite, improve the elongation and forming property of the strip, and at the same time ensure the Brinell hardness of the steel. If the air-cooling time is <3s, the ferrite content is less than 20%, which cannot achieve the purpose of improving the formability; if the air-cooling time is >10s, the ferrite content exceeds 60%, and the Brinell hardness of the steel grade is insufficient, which will also weaken the wear resistance of the steel. The strip is cooled to a final cooling temperature at a second cooling rate of ≥50℃ / s, and the final cooling temperature is controlled at <200℃, in order to convert all the austenite into martensite, and ensure the Brinell hardness of the steel.

[0062] In the tempering process, the tempering temperature is higher than 180℃ and the surface temperature of the strip or steel plate is kept at the furnace temperature for more than 5 minutes, so that the supersaturated C atoms in the steel are precipitated from the martensite, the carbon content in the martensite is ensured to be less than 0.5%, the brittleness of the martensite is reduced, the plasticity and toughness of the steel are improved, and the internal stress of the steel is reduced. If the tempering temperature is higher than 240℃, the steel will be obviously softened, the Brinell hardness will be significantly reduced, and the first type of tempering brittleness will occur, which will deteriorate the performance of the strip.

[0063] According to another embodiment of the present application, the method for manufacturing the dual-phase wear-resistant steel plate of the present application includes offline heat treatment, specifically including the following steps:

[0064] 1) Smelting and casting

[0065] The slab is smelted and cast based on the above-mentioned composition;

[0066] 2) Heating

[0067] Preferably, the heating temperature is 1200-1250℃, and the slab surface temperature is kept at 1200-1250℃ after the slab surface temperature reaches 1200-1250℃, and the holding time is >1.5h. In consideration of the comprehensive factors such as manufacturing cost, the holding time is usually below 3.0h;

[0068] 3) Rolling

[0069] Preferably, the final rolling temperature is 840-930℃;

[0070] 4) Cooling and coiling

[0071] Preferably, the strip is cooled to 500-700℃ at a cooling rate of ≥60℃ / s after rolling, and then coiled, and then air-cooled to room temperature to obtain a steel coil. In consideration of the comprehensive factors such as manufacturing cost and performance of the steel plate, the cooling rate after rolling is usually within 150℃ / s;

[0072] 5) Heat treatment, including quenching treatment and tempering treatment, wherein,

[0073] Preferably, the quenching temperature in the quenching treatment is 760-840℃, the steel coil surface temperature is kept at 760-840℃ after the steel coil surface temperature reaches 760-840℃, the quenching holding time is 5-40min, and the cooling rate is ≥20℃ / s to room temperature. In consideration of the comprehensive factors such as performance and manufacturing cost of the steel plate, the cooling rate in the quenching treatment is usually within 250℃ / s;

[0074] Preferably, the tempering temperature in the tempering treatment is 180-240℃, the steel coil surface temperature is kept at 180-240℃ after the steel coil surface temperature reaches 180-240℃, the tempering holding time is ≥5min, and in consideration of the comprehensive factors such as performance and manufacturing cost of the steel plate, the tempering holding time is usually within 30min, and finally cooled to room temperature, and the cooling mode is preferably air cooling.

[0075] In the above method of the present application:

[0076] In the slab heating process, the heating temperature is above 1200℃ and the holding time is >1.5h, so as to ensure that the alloy elements are fully solid-solved. When the heating temperature exceeds 1250℃, the austenite grains excessively grow, which causes the intergranular binding force to be weakened and cracks to be easily generated during rolling. In addition, when the heating temperature exceeds 1250℃, the surface of the slab is easily decarburized, which affects the mechanical properties of the finished product.

[0077] In the rolling process, the finish rolling temperature is controlled to be 840-930℃, so as to refine the austenite grains. After rolling, the steel plate is cooled to 500-700℃ at a cooling speed of ≥60℃ / s and then coiled, so as to obtain fine bainite or ferrite+pearlite structure and make the carbides be dispersedly distributed, thereby shortening the dissolution time of the carbides in the subsequent quenching and heating process.

[0078] In the quenching process, the A1 and A3 temperatures of the steel grade can be calculated according to the C content and other alloy components in the steel matrix, and the quenching and heating temperature is controlled to be 760-840℃, so as to ensure that 20-60% of ferrite can be formed in the steel plate. If the quenching and heating temperature is too low, the ferrite content is greater than 60%, the Brinell hardness of the steel is insufficient, the HBW300 level cannot be reached, and the wear resistance of the steel is weakened. If the quenching and heating temperature is too high, the ferrite content is less than 20%, the yield strength cannot be reduced and the elongation cannot be improved. The steel plate is cooled to room temperature at a cooling speed of ≥20℃ / s, so as to make the austenite be fully transformed into martensite and ensure the hardness of the steel.

[0079] In the tempering process, the tempering temperature is controlled to be 180-240℃ and the surface temperature of the steel plate reaches the furnace temperature (180-240℃) and is held for more than 5min, so as to make the supersaturated C atoms be precipitated from the martensite, ensure that the carbon content in the martensite is less than 0.5%, reduce the brittleness of the martensite, improve the plasticity and toughness of the steel plate, and reduce the internal stress of the steel plate. If the tempering temperature exceeds 240℃, the steel plate is obviously softened, the hardness is significantly reduced, and the first type of tempering brittleness is caused, which deteriorates the performance of the steel plate.

[0080] The beneficial effects of the present application are as follows:

[0081] In the prior art, micron-sized TiC particles are introduced into the microstructure of the wear-resistant steel plate, which can obviously improve the wear resistance under the condition of the same Brinell hardness, but further deteriorates the plasticity and toughness of the martensitic wear-resistant steel. Alternatively, the yield strength of the wear-resistant steel is reduced and the plasticity of the wear-resistant steel is improved by changing the matrix structure, but it is difficult for the existing steel plate to have both good processing formability (low yield strength and high elongation) and high wear resistance.

[0082] The present application adopts high Ti design in component design, controls 0.06%≤C-Ti / 3.98≤0.25%, forms a certain amount of 0.5-10 μm TiC particles in the steel plate, ensures the carbon content in the matrix to control the Brinell hardness of the steel at about 300 HBW, suppresses the depression and peeling of TiC particles in the wear process, fully plays the effect of TiC particles in improving the wear resistance of the steel, and improves the wear resistance of the steel. Meanwhile, the design of higher Ti content, combined with the control of the carbon content and the silicon content in the matrix, obtains ferrite + martensite dual-phase structure, preferably the carbon content in the martensite is <0.5%, weakens the strength difference between the ferrite and the martensite, ensures the good toughness of the steel, reduces the yield strength of the steel plate, and improves the formability, so that the steel plate simultaneously obtains good forming performance and wear resistance.

[0083] On the basis of the component design, the manufacturing process of the steel plate is further optimized, for example, according to the method of the present application, online two-stage cooling or offline heat treatment can be adopted.

[0084] In the online treatment process, the controlled cooling after rolling is regulated, that is, the cooling mode is specified and the stable cooling speed is controlled, the stop cooling temperature is controlled to be 600-700 ℃, and then air cooling is carried out, so as to regulate the ferrite structure content in the matrix, form the volume fraction of 20-60% ferrite + 40-80% martensite dual-phase structure, reduce the yield strength of the steel plate while improving the elongation, and greatly improve the formability of the steel plate; meanwhile, the Brinell hardness of the steel is ensured, and the improvement of the wear resistance is ensured.

[0085] In the offline heat treatment process, the ferrite structure content in the matrix is regulated by controlling the temperature and time control of quenching and tempering treatment, to form the volume fraction of 20-60% ferrite + 40-80% martensite dual-phase structure, reduce the yield strength of the steel plate while improve the elongation, and greatly improve the formability of the steel plate; meanwhile, the Brinell hardness of the steel is ensured, and the improvement of the wear resistance is ensured. The C atoms are controlled to precipitate from the martensite in the tempering process, to ensure the carbon content in the martensite <0.5%, reduce the yield strength of the steel plate while improve the elongation, and greatly improve the formability of the steel plate.

[0086] The scheme of the present application overcomes the problem that the traditional steel plate cannot simultaneously have formability and wear resistance, so that the steel plate has excellent formability and high wear resistance. The yield strength of the steel plate of the present application is ≤800 MPa, the elongation is ≥18%, the impact energy at -40 ℃ is ≥20 J, the Brinell hardness is 270-330 HBW, and the abrasive wear performance is equivalent to NM450. BRIEF DESCRIPTION OF DRAWINGS

[0087] Fig. 1 is a metallographic structure photo of the steel plate of Example 4 of the present application.

[0088] Fig. 2 is a metallographic structure photograph of the steel plate of Example 12 of the present application. DETAILED DESCRIPTION

[0089] The present application is further described below in conjunction with examples and drawings.

[0090] The steel plate compositions of the examples and comparative examples of the present application are shown in Table 1, and the rest are Fe and other inevitable impurities.

[0091] The specific manufacturing process parameters of the steel plates of the examples and comparative examples of the present application are shown in Tables 2-3. Table 2 lists the specific process parameters including offline heat treatment, and Table 3 lists the specific process parameters including online two-stage cooling.

[0092] As can be seen from Fig. 1, after offline heat treatment, the microstructure of the steel plate of Example 4 is ferrite + martensite + micron-sized TiC particles. The volume fraction of ferrite is about 50%, the volume fraction of martensite is about 48%, and the volume fraction of TiC particles is about 1.8%. As can be seen from Fig. 2, after online two-stage cooling, the microstructure of the steel plate of Example 12 is ferrite + martensite + micron-sized TiC particles, the volume fraction of ferrite is about 30%, the volume fraction of martensite is about 67%, and the volume fraction of TiC particles is about 1.8%.

[0093] The volume fractions of the microstructures in the steel plates were obtained according to GB / T 18876.1-2002 "Standard Test Method for Determining Metallographic Structure, Inclusion Content, and Grade of Steel and Other Metals by Automated Image Analysis, Part 1: Image Analysis and Stereology Determination of Inclusion or Second Phase Structure Content in Steel and Other Metals" and GB / T 15749-2008 "Quantitative Metallography Determination Method".

[0094] The mechanical properties of the steel plates of the examples and comparative examples were tested according to GB / T 228.1-2010 "Metallic Materials Tensile Test Standard", the Brinell hardness of the steel plates of the examples and comparative examples was tested according to GB / T 231.1-2018 "Metallic Materials Brinell Hardness Test", the abrasive wear of the steel plates of the examples and comparative examples was tested according to ASTM G65-2015, and the impact test of the steel plates of the examples and comparative examples was performed according to GB / T 229-2020 "Metallic Materials Charpy Pendulum Impact Test Method". The properties of the steel plates of the examples and comparative examples are shown in Table 3.

[0095] From the mechanical properties, the steel plate has low yield strength and higher elongation, the yield strength is less than or equal to 800 MPa, and the elongation is greater than or equal to 18%. Meanwhile, the steel plate also has very high wear resistance, under the condition that the Brinell hardness is about 300HBW, the wear resistance and hardness of 450HBW level NM450 are realized. This is due to the fact that the steel plate of the embodiment has a high Ti content and a specific element composition, especially a specific C and Ti element combination (satisfying the required C and Ti content relationship), so that a large number of TiC particles that improve wear resistance are formed in the steel plate. In addition, the manufacturing process of the steel plate of the embodiment adopts a suitable quenching heating temperature or a suitable cooling process after rolling, so that a suitable volume fraction of ferrite is formed in the steel plate, the yield strength is reduced and the elongation is improved, and a good combination of formability and wear resistance is realized.

[0096] In Comparative Examples 1 and 9, the Ti element content of the steel plate is too low, and the wear resistance is not enough.

[0097] In Comparative Examples 2 and 10, the Ti element content of the steel plate is too high, the plasticity and toughness are deteriorated, and the ideal mechanical properties cannot be achieved.

[0098] In Comparative Examples 3 and 11, the C and Ti element combination C-Ti / 3.98 combination value of the steel plate is too low, the Brinell hardness of the steel is too low, and the wear resistance is reduced.

[0099] In Comparative Example 4, the C and Ti element combination C-Ti / 3.98 combination value of the steel plate is too high, that is, the C content in the matrix is too high, the Brinell hardness of the steel plate is too high, and the plasticity is deteriorated.

[0100] In Comparative Example 5, although the composition can meet the requirements of the present application, the quenching temperature is too low, the ferrite volume fraction in the steel plate is too high, the Brinell hardness of the steel plate is too low, and the wear resistance is significantly reduced.

[0101] In Comparative Example 6, although the composition can meet the requirements of the present application, the quenching temperature is too low, the ferrite volume fraction in the steel plate is too low, the yield strength of the steel plate is too high, and the elongation is deteriorated.

[0102] In Comparative Examples 7 and 14, although the composition can meet the requirements of the present application, the tempering temperature is too low, the Brinell hardness of the steel plate is high, and the toughness is poor.

[0103] In Comparative Examples 8 and 15, although the composition can meet the requirements of the present application, the tempering temperature is too high, the Brinell hardness of the steel plate is significantly reduced, the wear resistance is reduced, and the temper brittleness is deteriorated.

[0104] In Comparative Example 12, although the composition can meet the requirements of the present application, the air cooling time is too long, the ferrite volume fraction is too high, the Brinell hardness of the steel is too low, and the wear resistance is significantly reduced.

[0105] In Comparative Example 13, although the components satisfy the requirements of the present application, the air cooling time is too short, the ferrite volume fraction is too low, the yield strength of the steel grade is too high, and the elongation is deteriorated.

[0106] The dual-phase wear-resistant steel plate described in the present application can be used in various fields requiring the use of wear-resistant steel, especially the use of concrete mixer truck and dump truck carriage steel plates which require both easy processing and high wear resistance.

Claims

1. A duplex wear-resistant steel plate, wherein, in addition to Fe and unavoidable impurities, the steel plate contains the following components by weight percentage: C: 0.16–0.50%, Si: 0.05–1.5%, Mn: 0.40–2.0%, Cr: 0.2–0.8%, Ti: 0.4–1.0%, N ≤ 0.005%, P ≤ 0.030%, S ≤ 0.005%, O ≤ 0.004%; and the contents of the above elements simultaneously satisfy the following relationship: 0.06% ≤ C - Ti / 3.98 ≤ 0.25%, wherein, in the calculation, the element symbols are substituted with the corresponding weight percentage of the element in the steel plate.

2. The duplex wear-resistant steel plate as described in claim 1, wherein the steel plate, in addition to Fe and unavoidable impurities, also contains the following components by weight percentage: C: 0.25-0.45%, Si: 0.05-0.5%, Mn: 0.40-2.0%, Cr: 0.2-0.8%, Ti: 0.4-1.0%, N≤0.005%, P≤0.030%, S≤0.005%, O≤0.004%; and the contents of the above elements simultaneously satisfy the following relationship: 0.14%≤C-Ti / 3.98≤0.21%, and in the calculation, the element symbols in the formula are substituted with the corresponding weight percentage of the element in the steel plate.

3. The duplex wear-resistant steel plate as described in claim 1 or 2, characterized in that, The steel plate further comprises one or a combination thereof selected from Mo, V, Nb, Cu, Ni, B, Al, Ca, and RE, wherein Mo ≤ 0.5%, V ≤ 0.06%, Nb ≤ 0.050%, Cu ≤ 0.5%, Ni ≤ 0.5%, B ≤ 0.003%, Al ≤ 0.06%, Ca ≤ 0.004%, and RE ≤ 0.005%.

4. The duplex wear-resistant steel plate as described in any one of claims 1-3, characterized in that, The steel plate comprises the following components by weight percentage: C: 0.16-0.50%, preferably 0.25-0.45%, Si: 0.05-1.5%, preferably 0.05-0.5%, Mn: 0.40-2.0%, Cr: 0.2-0.8%, Ti: 0.4-1%, N≤0.005%, P≤0.030%, S≤0.005%, O≤0.004%, with the balance being Fe and unavoidable impurities.

5. The duplex wear-resistant steel plate as described in any one of claims 1-4, characterized in that, The microstructure of the steel plate comprises 20-60% ferrite + 40-80% martensite + 0.4-2.0% TiC particles by volume; preferably, the average particle size of the TiC particles is 0.5-10 μm or the volume fraction of TiC particles with a particle size of 0.5-10 μm in the steel plate accounts for more than 95% of the total volume fraction of TiC particles; more preferably, the carbon content in the martensite is <0.5%; preferably, the microstructure of the steel plate comprises 20-60% ferrite + 40-80% martensite + 0.4-2.0% TiC particles by volume, with the balance being other carbides.

6. The duplex wear-resistant steel plate according to any one of claims 1-5, characterized in that, The steel plate has a yield strength ≤800MPa, elongation ≥18%, impact energy ≥20J at -40℃, Brinell hardness of 270~330HBW, and abrasive wear performance comparable to NM450.

7. The duplex wear-resistant steel plate according to any one of claims 1-6, characterized in that, The steel plate has the following properties: yield strength of 600-800 MPa, preferably 620-800 MPa; elongation of 18.0%-22.0%, preferably 19.0-22.0%; impact energy at -40℃ of 20-50 J, preferably 30-50 J; Brinell hardness of 270-330 HBW, preferably 295-330 HBW; and abrasive wear performance of the steel plate is 0.95-1.25 times, preferably 1.06-1.25 times, of NM450, based on the abrasive wear performance of NM450.

8. A method for manufacturing a duplex wear-resistant steel plate as described in any one of claims 1 to 7, characterized in that, The method includes the following steps performed sequentially: 1) Smelting and casting: The smelting and casting of the slab is based on the composition of any one of claims 1-4; 2) Heating; 3) Rolling; 4) Cooling and winding; 5) Heat treatment.

9. The method as described in claim 8, characterized in that, The method satisfies at least one of the following: In the heating step, the heating temperature is 1200-1250℃. After the surface temperature of the slab reaches 1200-1250℃, the heat preservation begins, and the heat preservation time is >1.5h, preferably ≤3.0h. In the rolling step, the final rolling temperature is 840–930°C; In the cooling and coiling steps, after rolling, the steel coil is cooled to 500-700°C at a cooling rate of ≥60°C / s, preferably ≤150°C / s, and then air-cooled to room temperature to obtain a steel coil. The heat treatment includes quenching and tempering. The quenching temperature for the quenching treatment is 760–840°C. After the surface temperature of the steel coil reaches 760–840°C, it is held at this temperature for 5–40 minutes. The coil is then cooled to room temperature at a rate of ≥20°C / s, preferably ≤250°C / s. The tempering temperature for the tempering treatment is 180–240°C. After the surface temperature of the steel coil reaches 180–240°C, it is held at this temperature for ≥5 minutes, preferably ≤30 minutes. The coil is then cooled to room temperature, preferably by air cooling.

10. The method as described in claim 8, characterized in that, The method satisfies at least one of the following: In the heating step, the heating temperature is 1200-1250℃. After the surface temperature of the slab reaches 1200-1250℃, the heat preservation begins, and the heat preservation time is >1.5h, preferably ≤3.0h. In the rolling step, the final rolling temperature is 840–930°C to obtain strip steel; In the cooling and coiling steps, the strip steel is subjected to segmented controlled cooling at a first cooling rate of ≥50℃ / s, preferably ≤150℃ / s, to the stop cooling temperature, which is 600~700℃, followed by air cooling for 3~10s. The strip is then cooled to the final cooling temperature at a second cooling rate of ≥50℃ / s, preferably ≤150℃ / s, where the final cooling temperature is <200℃, and then the strip enters the coiler for coiling. The heat treatment includes tempering, wherein the tempering temperature is 180–240°C and the tempering holding time is ≥5 min, preferably ≤30 min.

Images