High-performance low-cost wear-resistant steel plate and manufacturing method thereof

Abstract

The invention relates to a high-performance low-cost wear-resistant steel plate and a manufacturing method thereof, the high-performance low-cost wear-resistant steel plate comprises the following chemical components in percentage by mass: 0.10-0.25% of C, 0.10-0.90% of Si, 0.60-1.60% of Mn, less than or equal to 0.015% of P, less than or equal to 0.003% of S, 0.20-0.90% of Cr, 0.0005-0.0040% of B, 0.005-0.015% of Ti, less than or equal to 0.0050% of N and the balance of Fe and inevitable impurities, Ti / N is greater than or equal to 3, DI / t is equal to 0.23-0.30, and the high-performance low-cost wear-resistant steel plate can also contain one or two of Nb and Al elements. According to the method, online quenching (DQ) is combined with a two-stage controlled rolling process, and the rolling waste heat is directly utilized for quenching, so that an offline quenching link is omitted, and the energy consumption and the equipment cost are remarkably reduced. By controlling the water inlet temperature (780-880 DEG C), the cooling speed (larger than or equal to 16 DEG C / s) and the self-tempering temperature (150-250 DEG C), a self-tempering martensite structure is achieved, additional tempering is not needed, and the high hardness (330-480 HB) and the good low-temperature toughness (the impact toughness at the temperature of-40 DEG C is larger than or equal to 47 J) are achieved at the same time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of special steel smelting, and particularly relates to a high-performance low-cost wear-resistant steel plate and a manufacturing method thereof. BACKGROUND

[0002] The domestic market competition of wear-resistant steel plates is very fierce. On the one hand, more and more domestic steel enterprises complete the transformation of plate mill technical equipment, increase the improvement and development of high-quality and high-value wear-resistant steel plate products. The gap between the actual quality of domestic wear-resistant steel plates and foreign products is gradually narrowing, and the domestic market competition is more fierce. On the other hand, the downstream demand industries of wear-resistant steel plates include engineering machinery, coal, power, metallurgy and the like. The development of these industries is relatively rapid, and the demand for wear-resistant steel products is large, but the market competition is also relatively fierce. In addition, the wear-resistant steel products have a high degree of homogeneity, and the price competition is also relatively fierce.

[0003] In order to obtain an advantage in the fierce market competition, enterprises need to continuously strengthen technical innovation and produce more market-competitive products. Therefore, how to develop a low-cost wear-resistant steel plate while still maintaining a high performance quality level has become an urgent industry technical problem to be solved.

[0004] Online quenching refers to a new process of configuring a quenching device on a steel plate production line and quenching the steel plate after finish rolling. Compared with the traditional offline quenching process, online quenching has the following advantages: short production cycle, direct quenching after finish rolling without re-quenching heating, thereby shortening the production cycle; low emission, direct quenching on the main rolling line without offline heating, thereby reducing energy consumption and carbon emission; low cost, saving the equipment cost and energy consumption cost of offline quenching, and also saving the factory floor area and production time.

[0005] Online quenching has high requirements for the thickness, composition and production process of wear-resistant steel plates, and needs to match the online quenching process parameters. Otherwise, it is difficult to produce high-performance wear-resistant steel plates. SUMMARY

[0006] The application provides a high-performance low-cost wear-resistant steel plate and a manufacturing method thereof, and solves the technical problem of the prior art. The high-performance low-cost wear-resistant steel plate is manufactured by using a continuously cast billet produced by low-superheat protection casting with optimized composition design and high-purity molten steel as raw material, and adopting a two-stage controlled rolling + online quenching + self-tempering method.

[0007] The technical scheme adopted by the present application to solve the above problems is: a high-performance low-cost wear-resistant steel plate, the chemical component composition and weight percentage of which are as follows: C: 0.10-0.25%, Si: 0.10-0.90%, Mn: 0.60-1.60%, P≤0.015%, S≤0.003%, Cr: 0.20-0.90%, B: 0.0005-0.0040%, Ti: 0.005-0.015%, N≤0.0050%, the balance being Fe and inevitable impurities, and meeting the conditions of Ti / N≥3 and DI / t=0.23-0.30, and the steel plate can not contain Nb and Al elements or can contain one or two of Nb and Al elements. The steel plate has a tempered martensite structure and a surface hardness of 330-480 HBW.

[0008] The following specifically describes the functions and amounts of the components contained in the present application and the implementation method.

[0009] C: is the main element for ensuring the strength and hardness of the wear-resistant steel plate, but too high carbon content can reduce the toughness, welding performance and other processing performance of the wear-resistant steel plate, and in addition, if the C content is lower than 0.10%, the surface hardness of the steel plate will be lower than 330 HB, and the significant wear resistance will not be reflected. Therefore, the carbon content is controlled to be 0.10-0.25% in the present application, and the carbon content in this range makes the hardness of the steel plate after on-line quenching treatment to be between 330 and 480 HB.

[0010] Si: is a deoxidizing element in the steelmaking refining process, has a certain solid solution strengthening effect in steel, and can increase the tempering stability of the steel, so that the wear-resistant plate can reduce the internal stress of the steel plate and maintain the hardness when tempered at a lower temperature. If the Si content is too low, the deoxidizing effect cannot be achieved, and if the Si content is too high, the surface quality of the steel will be seriously affected. Therefore, the Si content is controlled to be 0.10-0.90% in the present application.

[0011] Mn: mainly exists in the form of solid solution in alloy steel. The solid-solution manganese will produce a certain solid-solution strengthening effect. Manganese can significantly refine the ferrite grain size after the γ→α phase transition in low-carbon steel without manganese. Manganese almost does not form carbides in ordinary low-alloy high-strength steel, but it can combine with the residual sulfur in the steel to form MnS. Generally, MnS is a harmful inclusion to the performance of the steel, but after proper control and modification, the degree of harm to the performance of the steel can be significantly reduced. The Mn content in the present application is in the range of 0.60-1.60%.

[0012] Al: has strong chemical affinity with oxygen, can be used as deoxidizer. At the same time, acid soluble aluminum can form AlN, which can play a role in refining grains during rolling process, improving material strength and toughness. The aluminum content in the application is between 0.015~0.085%. Since Nb element also plays a role in refining grains, Al element can also not be added.

[0013] Ti: can be unlimitedly soluble with C and N elements, but the solid solubility product of TiC and TiN in austenite is very different, so TiN can be mainly formed at high temperature, which can well play a role in fixing N in steel. N in steel is very easy to interact with active B atoms to form NB, thereby greatly reducing the quenching effect of B. Therefore, the use of Ti to fix N atoms to form TiN can ensure the play of B quenching. TiN usually precipitates in the form of 1~20μm inclusions, if the amount of TiN is relatively large, it will damage the toughness and crack resistance of the wear-resistant steel plate. Therefore, the Ti content should not be too high, and the upper limit is controlled to be 0.015%. The Ti content in the application is between 0.005~0.015%, and Ti / N≥3, which ensures that Ti can fully dissolve N elements. It is one of the key control points to improve the performance of wear-resistant steel plate.

[0014] Cr: significantly improves the hardenability of steel, and more martensite structure can be obtained during quenching, thereby enhancing the hardness and wear resistance of the steel plate. If excessive, it will significantly increase the carbon equivalent, thereby reducing the welding performance of the steel. At the same time, excessive increase of Cr is also not conducive to the toughness of the steel. The Cr content in the application is controlled to be 0.20~0.90%.

[0015] Nb: is an element that has a significant effect on grain refinement during rolling. In the recrystallization rolling stage, Nb hinders the recovery and recrystallization of deformed austenite through strain-induced precipitation, thereby refining the grains. This provides a basis for large-thickness steel plates to still have fine grain structure after heat treatment, which is beneficial to improve toughness. However, excessive Nb is difficult to completely dissolve due to the influence of heating temperature and other factors, and thus cannot play a role. Therefore, the application proposes that the Nb content range is 0.010~0.050%. Since AlN also plays a role in refining grains, Nb element can also not be added.

[0016] B: used to improve the hardenability of quenched and tempered steel, usually, a small amount of B can significantly improve the hardenability, and the combination of boron and nitrogen will make the above effect disappear. At the same time, with the increase of carbon content in the steel, the hardening effect of B will gradually weaken. Therefore, the B content in the application is controlled to be in the range of 0.0005~0.0040%.

[0017] S and P in steel are harmful impurity elements, and the lower the content of P and S in steel, the better. When the content of S in steel is relatively high, hot brittleness and other problems are prone to occur during hot rolling; when the content of P in steel is relatively high, the steel is prone to cold brittleness, in addition, phosphorus is prone to segregation, which is not conducive to the performance of the core of the steel plate. The content of P is controlled to be ≤0.015%, and the content of S is controlled to be ≤0.003% in the application. Preferably, the content of S should be ≤0.001%, which can significantly reduce the precipitation of MnS inclusions, and further improve the mechanical properties and crack resistance of the steel plate. It is one of the key control points for improving the performance of the wear-resistant steel plate.

[0018] Through repeated tests and comparison, it is found that when DI / t < 0.23, the ratio of martensite structure after heat treatment of the steel plate is <70%, which can cause a significant decrease in the hardness of the steel plate, so that effective wear resistance cannot be obtained; when DI / t > 0.30, the alloy content is too high, which can cause a decrease in the low-temperature toughness and welding performance of the steel plate, and at the same time, can greatly increase the cracking sensitivity of the steel plate, thereby greatly reducing the use performance of the steel plate. When the composition and thickness satisfy DI / t = 0.06 ~ 0.12, and the content of C in the steel plate is 0.10 ~ 0.25%, the wear-resistant steel plate with a ratio of martensite structure of more than 70% and a surface hardness of 330 ~ 480 HB can be obtained through the manufacturing method of the application. It is one of the key control points for improving the performance of the wear-resistant steel plate.

[0019] The manufacturing method of the high-performance and low-cost wear-resistant steel plate is as follows: Step 1: sequentially passing through KR hot metal pretreatment, converter smelting, LF refining, RH refining, and continuous casting, the molten steel with O ≤0.0015%, H ≤0.0002%, and N ≤0.0050% is produced. In the continuous casting process, low superheat (≤30℃) and protective slag are used to produce continuous casting slabs.

[0020] Step 2: heating the slab to 1160 ~ 1240℃, the holding time is 2.0 ~ 3.5h, after discharging, two-stage rolling is used, the first stage rolling temperature is 1050 ~ 1150℃, the total pass reduction rate is ≥30%; the second stage rolling temperature is 870 ~ 930℃, the total pass reduction rate is ≥20%, the finish rolling temperature is 830 ~ 900℃, and the rolling is performed to the finished thickness.

[0021] Step 3: The finished steel plate is subjected to online quenching (DQ) treatment. The online quenching water inlet temperature is 780-880 DEG C, the cooling rate is greater than or equal to 16 DEG C / s, and the water outlet red temperature is 150-250 DEG C. After completion, the steel plate is cooled to room temperature on a cooling bed to obtain a finished steel plate. Through repeated tests and comparison, it is found that: (1) the online quenching cooling rate is greater than or equal to 16 DEG C / s, which can greatly reduce the generation of other non-martensitic structures except for part of the residual austenite, so that the steel plate can obtain sufficient martensitic structure, and the wear resistance and service life of the steel plate are improved; (2) the water outlet red temperature is between 150-250 DEG C, so that the steel plate can be sufficiently self-tempered, and part of the supersaturated carbon in the martensitic matrix can be precipitated as fine carbides, which is very beneficial to reducing the quenching stress in the steel plate, improving the brittleness of the steel plate, and improving the crack resistance and fracture resistance of the steel plate. When the red temperature is lower than 150 DEG C, the self-tempering effect of the steel plate is insufficient; when the red temperature is higher than 250 DEG C, a large amount of supersaturated carbon in the martensite will be precipitated, thereby reducing the hardness of the martensitic matrix, and further reducing the strength and hardness of the steel plate, and damaging the wear resistance of the steel plate. At the same time, due to the high red temperature, the amount of precipitated carbides will increase, and the size of the carbides will increase, which will reduce the impact performance of the steel plate. Therefore, the red temperature is at most 250 DEG C and at least 150 DEG C. Within this range, the steel plate does not need to be additionally tempered after online quenching, and the mechanical properties of the steel plate can be optimally matched, so that good comprehensive mechanical properties can be obtained.

[0022] Compared with the prior art, the present application has the following advantages: 1) The present application forms a low alloying and high hardenability composition system by controlling the specific range of C (0.10-0.25%), Si, Mn, Cr, B, Ti and other elements, combining Ti / N≥3 and the ratio of DI / t=0.23-0.30. Among them, the design of Ti / N≥3 releases the hardenability of B by fixing N element, which is the key innovation point to solve the failure problem of B and N combination in traditional wear-resistant steel plate. The introduction of DI / t dynamically matches the hardenability index and the thickness, optimizes the proportion of martensitic structure (≥70%), and balances the hardness and toughness.

[0023] 2) The online quenching (DQ) combined with the two-stage controlled rolling process directly utilizes the rolling residual heat for quenching, which saves the offline quenching link, significantly reduces the energy consumption and equipment cost. By controlling the water inlet temperature (780-880 DEG C), the cooling rate (≥16 DEG C / s) and the red temperature (150-250 DEG C), the self-tempered martensitic structure is realized, and additional tempering is not needed, which has high hardness (330-480 HB) and good low-temperature toughness (-40 DEG C impact toughness≥47 J).

[0024] 3) Low cost: By reducing the addition of noble metals (such as Ni, Mo) and utilizing online quenching to simplify the process, production costs are reduced.

[0025] High performance: Through the synergistic control of Ti / N and DI / t, the contradiction between hardenability and toughness under low alloying is solved, and the balance between surface hardness and impact toughness is achieved.

[0026] Process efficiency: Online quenching technology shortens the production cycle, reduces carbon emissions, and meets the green manufacturing trend. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be described in more detail in conjunction with the preferred embodiments of the present application. However, these embodiments are only a description of the preferred embodiments of the present application, and cannot impose any limitation on the scope of the present application. Example 1

[0028] The thickness of the wear-resistant steel plate of this embodiment is 10 mm, and the chemical composition in terms of mass percentage is: C: 0.15%, Mn: 0.80%, Si: 0.30%, S: 0.002%, P: 0.012%, Nb: 0.015%, Cr: 0.45%, B: 0.0020%, Ti: 0.012%, Al: 0.035%, N: 0.0035%, the balance being Fe and unavoidable impurity elements, DI / t = 0.231.

[0029] After KR hot metal pretreatment, converter smelting, LF refining, RH refining, and continuous casting, a molten steel with O of 0.0009%, H of 0.00016%, and N of 0.0035% is produced. During continuous casting, low superheat (23°C) and protective slag are used to produce continuous casting slabs. The slab is heated to 1230°C, and the holding time is 2.5h. After tapping, two-stage rolling is used, with the first stage rolling temperature being 1100°C and the total pass reduction rate being 40%; the second stage rolling temperature is 920°C, and the total pass reduction rate is 25%, with the finish rolling temperature being 880°C, and the rolling is stopped at the finished thickness. The rolled steel plate is then subjected to online quenching (DQ) treatment. The online quenching water inlet temperature is 850°C, the cooling rate is 35°C / s, and the water outlet red temperature is 220°C. After completion, the steel plate is cooled to room temperature on a cooling bed, and the finished steel plate is obtained.

[0030] The 10mm wear-resistant steel plate produced by the above manufacturing process has an average surface hardness of 362HB, a tensile strength of 1183MPa, and a -40°C impact toughness of 83J. Example 2

[0031] The wear-resistant steel plate of this embodiment has a thickness of 20 mm, and its chemical components in terms of mass percentage are: C: 0.16%, Mn: 1.0%, Si: 0.30%, S: 0.002%, P: 0.011%, Nb: 0.025%, Cr: 0.40%, B: 0.0020%, Ti: 0.012%, Al: 0.040%, N: 0.0040%, and the balance of Fe and inevitable impurity elements, DI / t = 0.238.

[0032] The slab is heated to 1205℃, and the holding time is 2.5h. After being discharged, two-stage rolling is adopted, the first-stage rolling temperature is 1100℃, and the total pass reduction is 35%; the second-stage rolling temperature is 910℃, and the total pass reduction is 23%, and the finish rolling temperature is 880℃, and the rolling is performed to the finished thickness. The finished steel plate is immediately subjected to on-line quenching (DQ) treatment. The on-line quenching water entry temperature is 860℃, the cooling rate is 35℃ / s, and the water exit re-red temperature is 210℃. After completion, the steel plate enters the cooling bed to cool to room temperature to obtain the finished steel plate.

[0033] The 20mm wear-resistant steel plate prepared through the above manufacturing process has an average surface hardness of 418HB, a tensile strength of 1309MPa, and a-40℃ impact toughness of 62J. Example 3

[0034] The wear-resistant steel plate of this embodiment has a thickness of 30 mm, and its chemical components in terms of mass percentage are: C: 0.18%, Mn: 1.30%, Si: 0.30%, S: 0.002%, P: 0.012%, no special addition of Nb, Cr: 0.50%, B: 0.0025%, Ti: 0.012%, Al: 0.050%, N: 0.0030%, and the balance of Fe and inevitable impurity elements, DI / t = 0.247.

[0035] The slab is heated to 1220℃, and the holding time is 2.5h. After being discharged, two-stage rolling is adopted, the first-stage rolling temperature is 1090℃, and the total pass reduction is 35%; the second-stage rolling temperature is 890℃, and the total pass reduction is 22%, and the finish rolling temperature is 860℃, and the rolling is performed to the finished thickness. The finished steel plate is immediately subjected to on-line quenching (DQ) treatment. The on-line quenching water entry temperature is 820℃, the cooling rate is 26℃ / s, and the water exit re-red temperature is 180℃. After completion, the steel plate enters the cooling bed to cool to room temperature to obtain the finished steel plate.

[0036] The 30mm wear-resistant steel plate prepared through the above manufacturing process has an average surface hardness of 433HB, a tensile strength of 1421MPa, and a-40℃ impact toughness of 61J. Example 4

[0037] The wear-resistant steel plate of this embodiment has a thickness of 40 mm, and its chemical components in terms of mass percentage are: C: 0.20%, Mn: 0.85%, Si: 0.85%, S: 0.001%, P: 0.010%, Nb: 0.040%, Cr: 0.65%, B: 0.0025%, Ti: 0.015%, Al: 0.065%, N: 0.0030%, and the balance of Fe and inevitable impurity elements, DI / t = 0.24.

[0038] The slab is heated to 1225℃, and the holding time is 2.5h. After being discharged, two-stage rolling is adopted, the first-stage rolling temperature is 1080℃, and the total pass reduction is 35%; the second-stage rolling temperature is 890℃, and the total pass reduction is 25%, and the finish rolling temperature is 850℃, and the rolling is performed to the finished thickness. The finished steel plate is immediately subjected to on-line quenching (DQ) treatment. The on-line quenching water entry temperature is 860℃, the cooling speed is 28℃ / s, and the water exit re-red temperature is 220℃. After completion, the steel plate enters the cooling bed to cool to room temperature to obtain the finished steel plate.

[0039] The 40mm wear-resistant steel plate prepared through the above manufacturing process has an average surface hardness of 449HB, a tensile strength of 1498MPa, and a-40℃ impact toughness of 49J. Example 5

[0040] The wear-resistant steel plate of this embodiment has a thickness of 50 mm, and its chemical components in terms of mass percentage are: C: 0.26%, Mn: 1.51%, Si: 0.30%, S: 0.001%, P: 0.010%, Nb: 0.050%, Cr: 0.90%, B: 0.0025%, Ti: 0.015%, Al: 0.085%, N: 0.0030%, and the balance of Fe and inevitable impurity elements, DI / t = 0.3.

[0041] The slab is heated to 1235℃, and the holding time is 2.5h. After being discharged, two-stage rolling is adopted, the first-stage rolling temperature is 1120℃, and the total pass reduction is 36%; the second-stage rolling temperature is 900℃, and the total pass reduction is 20%, and the finish rolling temperature is 850℃, and the rolling is performed to the finished thickness. The finished steel plate is immediately subjected to on-line quenching (DQ) treatment. The on-line quenching water entry temperature is 870℃, the cooling speed is 22℃ / s, and the water exit re-red temperature is 210℃. After completion, the steel plate enters the cooling bed to cool to room temperature to obtain the finished steel plate The 50mm wear-resistant steel plate prepared through the above manufacturing process has an average surface hardness of 478HB, a tensile strength of 1562MPa, and a-40℃ impact toughness of 47J.

[0042]

[0043] While the preferred embodiments of the application have been described above in detail, it is to be understood that various modifications and alterations to the preferred embodiments will occur to persons skilled in the art. Any such modifications or alterations are intended to fall within the scope of the application.

Claims

1. A high-performance, low-cost wear-resistant steel plate, characterized by: The chemical composition and weight percentage of the steel plate are: C: 0.10-0.25%, Si: 0.10-0.90%, Mn: 0.60-1.60%, P ≤ 0.015%, S ≤ 0.003%, Cr: 0.20-0.90%, B: 0.0005-0.0040%, Ti: 0.005-0.015%, N ≤0.0050%, and Ti / N ≥ 3, and the balance is Fe and unavoidable impurities.

2. The high-performance, low-cost wear-resistant steel plate according to claim 1, characterized in that: The chemical composition of the steel plate satisfies: DI / t = 0.23 ~ 0.30 (1) Formula DI = [6.9*Mn*Mn+3.2*Si+22.6*Cr*Cr+23.1*Mo+(13*Cr+2.5*Mo+9.7)*Ni +8*Cu+7.9*B*1000+2.5]*C (2) formula Where DI is the hardenability index, t is the thickness of the steel plate in mm, and the elements in formula (2) represent the mass percentage content of each element in the steel.

3. The high-performance, low-cost wear-resistant steel plate according to claim 2, characterized in that: The Ti and N elements of the steel plate satisfy Ti / N≥3.

4. The high-performance, low-cost wear-resistant steel plate according to claim 1, characterized in that: The S content in the steel plate is ≤0.001%.

5. The high-performance, low-cost wear-resistant steel plate according to claim 1, characterized in that: The steel plate contains one or two of the following elements: Al ≤ 0.085% and Nb ≤ 0.050% by mass.

6. The high-performance, low-cost wear-resistant steel plate according to claim 1, characterized in that: The steel plate contains one, two or three of the following elements: Ni ≤ 1.0%, Mo ≤ 0.80%, and Cu ≤ 0.30% in mass percentage.

7. The high-performance, low-cost wear-resistant steel plate according to claim 1, characterized in that: The steel plate has a structure of tempered martensite, a surface hardness of 330-480 HBW, and an impact toughness of ≥47J at -40°C.

8. A method for manufacturing a high-performance, low-cost wear-resistant steel plate according to claim 1, characterized in that: The method mainly includes: Step 1: After KR hot metal pretreatment, converter smelting, LF refining, RH refining, and continuous casting, molten steel with O≤0.0015%, H≤0.0002%, and N≤0.0050% is produced. During the continuous casting process, low superheat ≤30℃ and mold slag are used to produce continuous casting slabs; Step 2: Heat the slab to 1160-1240°C and hold it for 2.0-3.5 hours. After it comes out of the furnace, it is rolled in two stages. The first stage rolling temperature is 1050-1150°C, and the total pass reduction rate is ≥30%. The second stage rolling temperature is 870-930°C, and the total pass reduction rate is ≥20%. The final rolling temperature is 830-900°C, and the slab is rolled to the finished thickness. Step 3: The rolled steel plate is then subjected to online quenching (DQ) treatment. The online quenching water temperature is 780-880°C, the cooling rate is ≥16°C / s, and the water outlet temperature is 150-250°C. After completion, the steel plate enters the cooling bed and cools to room temperature to obtain the finished steel plate.

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