CN116145017B - Production method of high-toughness wear-resistant steel plate with uniform hardness in thickness direction - Google Patents

Production method of high-toughness wear-resistant steel plate with uniform hardness in thickness direction Download PDF

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CN116145017B
CN116145017B CN202310160407.XA CN202310160407A CN116145017B CN 116145017 B CN116145017 B CN 116145017B CN 202310160407 A CN202310160407 A CN 202310160407A CN 116145017 B CN116145017 B CN 116145017B
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hardness
steel plate
temperature
rolling
casting blank
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CN116145017A (en
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童明伟
鲍海燕
卜勇
刘丰恺
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Baowu Group Echeng Iron and Steel Co Ltd
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Baowu Group Echeng Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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Abstract

The invention relates to a production method of a high-toughness wear-resistant steel plate with uniform hardness in the thickness direction, which comprises the following steps: the method comprises the steps of (1) refining and purifying steel outside a furnace, (2) continuous casting, protecting and casting in a whole process, (3) heating casting blanks, (4) rolling in two stages to ensure uniform performance of different parts of a product, (5) cooling and heat treatment to further ensure the uniformity of the performance of the different parts of the product; the casting blank comprises the following chemical components in percentage by weight C：0.27～0.32%,Si：0.20～0.50%,Mn：0.85～1.20%,P≤0.002%,S≤0.0005%,Cr：0.52～0.76%,Mo：0.24～0.43%,Nb：0.026～0.048%,Ti：0.012～0.023%,B：0.0015～0.0027%,Ca：0.0012～0.0030%,O≤20×10‑4%,N≤22×10‑4%,H≤0.5×10‑4%,As≤0.0003%,Sn≤0.0003%,, and the balance of Fe and unavoidable impurities, wherein the chemical components also have to satisfy the formula: ca/S=5.0-6.0,0.64.ltoreq.C+Mn/6+ (Cr+Mo)/5.ltoreq.0.67; the thickness of the finished steel plate produced by the invention is 50-80 mm, the surface hardness HBW10/3000 is 530-550, the core hardness is more than 95% of the surface hardness, and the KV 2 at minus 40 ℃ is more than or equal to 100J.

Description

Production method of high-toughness wear-resistant steel plate with uniform hardness in thickness direction
Technical Field
The invention relates to the technical field of manufacturing of high-strength wear-resistant steel for engineering machinery, in particular to a production method of a high-toughness wear-resistant steel plate with uniform hardness in the thickness direction.
Background
With the high-speed development of industrial technology in China, large-scale mechanical equipment applied to severe environments such as agriculture, engineering, mining, ports, metallurgy, electric power and the like is increasingly large and complex, and the technical requirements on high-strength wear-resistant steel used for manufacturing the mechanical equipment are also increasingly high. At present, high-strength wear-resistant steel is generally manufactured by a quenching and tempering process, contains a large amount of chromium-molybdenum alloy besides higher carbon content, and has the defects of low-temperature toughness, poor welding performance, poor machining performance and the like, meanwhile, the hardness of the central part of a thick steel plate is only about 60-75% of the hardness of the surface layer, the service life of mechanical equipment is seriously influenced, and even the national requirements are completely met by depending on foreign imports.
Before the invention, the Chinese patent application of application number 201910984149.0 discloses a 60-80 mm extra-thick wear-resistant steel plate and a production method thereof, and the patent effectively improves the core quality of the wear-resistant steel plate through reasonable component improvement, special rolling process and tempering heat treatment, so that the core hardness of the steel plate reaches more than 85% of the surface hardness, and the defects are that the forced cooling and rough rolling process are repeated for many times in the rough rolling process, the rolling efficiency is seriously affected, the equipment requirement is high, the implementation difficulty is high, and the surface hardness HBW10/3000 of the steel plate is only 390-430.
The Chinese patent application of application number 201910236142.0 discloses an easy-welding high-strength high-toughness wear-resistant steel and a manufacturing method thereof, and the finished product of the patent is low in cost, simple in process, high in strength and hardness, good in low-temperature toughness, excellent in mechanical processing performance and easy-welding wear-resistant steel plate by controlling the content of carbon and alloy elements and each technological parameter, and the defects that the microstructure of the steel plate is too complex, the ratio of the residual austenite to the lower bainite is narrow, the implementation difficulty is high, the hardness of the steel plate is only 420-480HB, and the Brinell hardness uniformity in the thickness direction cannot be ensured.
The Chinese patent application No. 201210270193.3 discloses a high-hardness high-toughness wear-resistant steel plate and a manufacturing method thereof, and the wear-resistant steel plate obtained according to the components and the process of the patent has high hardness and excellent wear resistance, is suitable for very easy wear equipment in engineering machinery, but in the embodiment of the patent product, the thickness specification is only 12-28mm, the impact power at minus 40 ℃ is lower than 100J, and the uniformity of Brinell hardness in the thickness direction cannot be ensured. The Chinese patent application product of application number 201210269896.4 is easy to weld, high in strength and hardness, good in low-temperature toughness and excellent in mechanical processing performance, but the Brinell hardness of the product is only 390-470HBW, and the uniformity of the Brinell hardness in the thickness direction cannot be ensured.
The Chinese patent application No. 2015123226. X discloses a high-toughness ultra-thick wear-resistant steel with stable Brinell hardness and a preparation method thereof, and the patent has the advantages of excellent comprehensive mechanical property, good impact toughness and stable Brinell hardness of a steel plate through reasonable component design and process improvement, but the Brinell hardness of the surface of the patent is lower than 500HBW, the Brinell hardness of the 1/2 part of the thickness of the steel plate is lower than 95% of the surface, and the impact energy at minus 40 ℃ is also lower than 100J.
The Chinese invention patent application with the application number 201210270605.3 has the advantages that the wear-resistant steel plate obtained according to the components and the process has high strength and hardness, good low-temperature toughness and excellent mechanical processing performance, but the impact energy at the temperature of minus 40 ℃ is only 50-80J, and the uniformity of the hardness in the thickness direction cannot be ensured; the Chinese patent application with the application number 200980162490.2 has high-toughness wear-resistant steel which can be used in cold areas, has good toughness and processability and is not easy to influence the characteristics under the manufacturing conditions, but the Brinell hardness of the patent is lower than 500HBW, the impact energy at-40 ℃ is 29-72J, and the uniformity of the hardness in the thickness direction cannot be ensured.
Therefore, developing a high-toughness wear-resistant steel plate with high hardness level and uniform section hardness to meet the requirement of the current large-scale mechanical steel becomes a problem to be solved in the industry.
Disclosure of Invention
The invention aims to provide a production method of a high-toughness wear-resistant steel plate with uniform hardness in the thickness direction, aiming at the problems that the existing wear-resistant steel plate has larger difference between surface hardness and core hardness, or has too low hardness level, or has insufficient low-temperature toughness, or has too thin thickness and can not meet the use requirement of large machinery. The thickness of the finished product of the steel plate is 50-80 mm, the surface hardness HBW is 530-550, the core hardness is more than 95% of the surface layer, the KV 2 at minus 40 ℃ is more than or equal to 100J, the hardness of the steel plate in the thickness direction is uniform, and the steel plate has excellent low-temperature toughness.
The invention relates to a production method of a high-toughness wear-resistant steel plate with uniform hardness in the thickness direction, which comprises the following steps:
(1) Refining outside a furnace: LF treatment time is 42-45 min, and outbound S is less than or equal to 0.001; RH extreme vacuum degree is less than 67Pa, the time of the extreme vacuum treatment is 16-20 min, and argon is continuously blown for 8-10 min after calcium wire feeding;
(2) Continuous casting: the whole process is protected and poured, the superheat degree is 5-10 ℃, and the slow cooling time of a casting blank slow cooling pit is more than 72 hours;
(3) Heating: heating temperature is 1280-1310 ℃, soaking temperature is 1250-1260 ℃, and soaking time is more than or equal to 72min;
(4) Rolling: two-stage rolling is adopted, and I-stage rough rolling is adopted: firstly removing phosphorus from the casting blank by high-pressure water after the casting blank is discharged, enabling the surface and the core of the casting blank to have a temperature difference of 100-300 ℃, then immediately rough rolling for 3-5 times, and enabling the single rolling reduction to be 35-45 mm until the thickness of a rolled piece is 2.5 times that of a finished product; and II, finish rolling: water-cooling the surface of a rolled piece to 950-980 ℃, then finish rolling for 4-5 times, wherein the single rolling reduction is 25-35 mm, and the final rolling temperature is 890-910 ℃;
(5) And (3) cooling: the water cooling start temperature of the steel plate is more than or equal to 860 ℃, the cooling speed is more than 50 ℃/s, and the redback temperature is less than or equal to 120 ℃;
(6) And (3) heat treatment: quenching temperature is 900-920 ℃, and the furnace time is 1.8XH+ (20-25) min; tempering the quenched steel plate within 24 hours after cooling to room temperature, wherein the tempering temperature is 150-260 ℃, and the furnace time is 4.8 XH for min; where H is the thickness of the finished steel sheet in mm.
Preferably, the thickness of the casting blank is 300-320 mm.
The thickness of the finished steel plate produced by the method is 50-80 mm, the surface hardness HBW10/3000 is 530-550, the core hardness is more than 95% of the surface hardness, and the KV 2 at minus 40 ℃ is more than or equal to 100J.
The casting blank disclosed by the invention contains the following chemical components ：C：0.27～0.32%,Si：0.20～0.50%,Mn：0.85～1.20%,P≤0.002%,S≤0.0005%,Cr：0.52～0.76%,Mo：0.24～0.43%,Nb：0.026～0.048%,Ti：0.012～0.023%,B：0.0015～0.0027%,Ca：0.0012～0.0030%,O≤20×10-4%,N≤22×10-4%,H≤0.5×10-4%,As≤0.0003%,Sn≤0.0003%, in percentage by weight, the balance being Fe and unavoidable impurities, and the chemical components also have to satisfy the formula: ca/S=5.0-6.0,0.64.ltoreq.C+Mn/6+ (Cr+Mo)/5.ltoreq.0.67.
Preferably, the casting blank contains the following chemical components ：C：0.27～0.32%,Si：0.25～0.45%,Mn：0.88～1.12%,P≤0.002%,S≤0.0005%,Cr：0.55～0.72%,Mo：0.27～0.41%,Nb：0.029～0.045%,Ti：0.014～0.021%,B：0.0017～0.0025%,Ca：0.0014～0.0026%,O≤20×10-4%,N≤22×10-4%,H≤0.5×10-4%,As≤0.0003%,Sn≤0.0003%, in percentage by weight, the balance being Fe and unavoidable impurities, and the chemical components also have to satisfy the formula: ca/s=5.0 to 6.0; C+Mn/6+ (Cr+Mo)/5.ltoreq.0.64.ltoreq.0.67.
The finished steel plate produced by the invention has excellent low-temperature toughness and excellent thickness-direction hardness uniformity, the production process is simple and feasible, and the method can be implemented in various metallurgical enterprises, and the innovation point of the invention is that the precise control of various process parameters is realized, and the specific process parameters are selected by the following reasons:
(1) The external refining aims at mainly degassing and desulfurizing, fully homogenizing the temperature and the components of molten steel, modifying the morphology of spheroidized inclusions, fully floating the inclusions, improving the inclusion removal proportion, purifying the molten steel to improve the metallurgical quality in a casting blank, and facilitating the acquisition of the mechanical properties required by the invention, so that the technological parameters of the external refining are strictly limited;
(2) The continuous casting adopts full-flow protection casting, limits the superheat degree and the slow cooling time of a slow cooling pit, aims to prevent secondary oxidation of molten steel, improve center segregation, promote H to sufficiently escape so as to prevent defects such as white spots, hydrogen embrittlement, micropores and the like, and further obtain high-quality casting blanks, high low-temperature toughness and uniformity of hardness in the thickness direction;
(3) Limiting the heating temperature, soaking temperature and soaking time of the casting blank, promoting the complete austenitization of the casting blank, and relieving center segregation so as to obtain high low-temperature toughness and uniformity of hardness in the thickness direction;
(4) The rolling adopts two-stage rolling: firstly removing phosphorus from the casting blank by high-pressure water after the casting blank is discharged, enabling the surface and the core of the casting blank to have a temperature difference of 100-300 ℃, then immediately rough rolling for 3-5 times, and ensuring single rolling reduction of 35-45 mm, wherein the aim is to remove oxidized iron scales on the surface of the casting blank, improve the surface quality, promote the casting blank to deform and permeate into the core under large rolling reduction, ensure that core grains are fully crushed and refined, enable the core structure and the surface grains of a finished steel plate to be consistent, and ensure the uniformity of the performance of different parts of the product; in order to reduce the waiting time of the intermediate billet and prevent the excessive growth of grains at high temperature, the surface laminar flow of the rough rolling piece is cooled to 950-980 ℃ by water, the rough rolling piece is immediately finish rolled for 4-5 times, the single rolling reduction is 25-35 mm, the deformation is promoted to permeate into the core part, and the uniformity of the properties of different parts of the product is ensured; the water cooling starting temperature, the cooling speed and the reddening temperature are limited to ensure that the steel plate is completely in an austenite state before water cooling, after rapid water cooling, the martensite phase ratio in the microstructure of each part of the steel plate is more than 98%, and the uniformity of the microstructure and the performance of each part of the steel plate is ensured;
(5) The heat treatment is performed with off-line quenching and tempering treatment, so that finer tissues can be obtained, the uniformity of the properties of different parts of the product is further ensured, and the low-temperature toughness and the machining property are improved.
The reason for the limitation of the chemical components in the present invention is described in detail below:
The C content of the invention is selected to be 0.27-0.32%, the carbon mainly improves the steel plate strong hardness through the clearance solid solution strengthening effect, and forms fine carbide substance point refinement structure with carbide forming elements, thereby preventing grain boundary sliding and dislocation movement and improving the strong hardness and low-temperature toughness. In addition, the carbon can also improve the hardenability and the uniformity of the strength and the hardness of the steel plate in the thickness direction. When the carbon content is less than 0.27%, the strength and hardness of the steel sheet cannot be ensured, and when the carbon content is more than 0.32%, the low temperature toughness, plasticity, machinability and weldability are adversely affected. Therefore, the carbon content is limited to 0.27 to 0.32%.
The Si content of the invention is selected to be 0.20-0.50%, and the Si is generally used as a deoxidizer in the steelmaking process to play a role in purifying steel, and the solid solution strengthening mode is used for improving the strong hardness, but is not beneficial to the low-temperature toughness, the machining performance and the welding performance. Therefore, the silicon content is limited to 0.20 to 0.50%.
The Mn content of the invention is selected to be 0.85-1.20%, and a proper amount of manganese has the function of refining grains, so that the high hardness and the low-temperature toughness are improved, and meanwhile, the combination of manganese and sulfur plays the role of desulfurizing agent to purify the steel, thereby being beneficial to the low-temperature toughness. However, excessive manganese is liable to cause segregation and form large-sized inclusions containing manganese sulfide, which is unfavorable for low-temperature toughness. Therefore, the manganese content is limited to 0.85-1.20%.
The P is less than or equal to 0.002 percent, the S is less than or equal to 0.0005 percent, phosphorus and sulfur are extremely easy to gather in grain boundaries, and large-scale inclusion containing manganese sulfide is formed, so that the low-temperature toughness is reduced sharply, and the content of the large-scale inclusion should be reduced as much as possible.
The Cr content of the invention is selected to be 0.52-0.76%, and the Cr plays a solid solution strengthening role to form various forms of carbide in the steel, so that the Cr obviously improves the strength and the hardness of the steel; chromium is also a hardenability element, improving the strong hardness uniformity in the thickness direction; chromium may also improve the tempering stability of the steel, but excessive chromium deteriorates low temperature toughness and weldability. When the chromium content is less than 0.52%, the technical requirements cannot be met, and when the chromium content is more than 0.76%, the performance requirements of the product of the invention are adversely affected.
The Mo content of the invention is selected to be 0.24-0.43%, the molybdenum has strong solid solution strengthening effect, forms various carbides such as MoC and the like in steel, and obviously improves the strong hardness; molybdenum has very strong hardenability, and can improve the uniformity of the strength and the hardness in the thickness direction; molybdenum can also increase tempering stability and improve tempering brittleness, but excessive molybdenum deteriorates low temperature toughness and weldability. When the molybdenum content is lower than 0.24%, the technical requirements cannot be met, and when the molybdenum content is higher than 0.43%, the performance requirements of the product are adversely affected.
The Nb content is selected to be 0.026-0.048%, and refined grains of carbon nitride particles are formed by niobium in the steel, so that the high hardness and the low-temperature toughness are improved; when niobium and molybdenum are added in a combined way, molybdenum promotes NbC particles to be evenly separated out and prevents the NbC particles from aggregation and growth, so that the high hardness and the low-temperature toughness are further improved; the niobium can also improve the recrystallization temperature, so that the product can be rolled at high temperature and high pressure, and the toughness and the uniformity of performance are ensured. When the niobium content is less than 0.026%, the above technical requirements cannot be satisfied, and when the niobium content is more than 0.048%, the performance requirements of the product of the invention are adversely affected.
The Ti is selected to be 0.012-0.023%, and the carbonitride formed by the Ti in the steel can effectively inhibit the growth of high-temperature austenite grains and improve the strong hardness and the low-temperature toughness; the combined addition of titanium and niobium can significantly increase the recrystallization temperature, which is beneficial to rolling at high temperature and high pressure. When the titanium content is less than 0.012%, the above effect is not obvious, and when the titanium content is more than 0.023%, tiN inclusions which are unfavorable for low temperature toughness are easily formed.
The B content of the invention is selected to be 0.0015-0.0027%, the hardenability of the boron is obviously improved, and the strong hardness and the thickness direction strong hardness uniformity of the steel are ensured, but the boron is extremely easy to gather grain boundaries, induce grain boundary cracks, deteriorate the low-temperature toughness and cause a thermal embrittlement phenomenon, so the boron content is limited to be 0.0015-0.0027%.
The Ca content is selected to be 0.0012-0.0030 percent, and the calcium in the steel is modified to spheroidize MnS inclusion, so that the low-temperature toughness is improved; calcium oxide can be formed with oxygen to play a role in deoxidization, so that the steel is purified and the metallurgical quality of casting blanks is improved; however, when the content of calcium is too high, the grain boundary is easily biased, and large-scale composite inclusions of oxysulfide of calcium are easily formed, which is not favorable for low-temperature toughness. Therefore, the content of calcium is limited to 0.0015 to 0.0030%.
The O content of the invention is selected to be less than or equal to 20 multiplied by 10 -4%, oxygen generally belongs to harmful gas, the oxygen exists in the form of FeO, mnO, siO 2、Al2O3 and other inclusions in steel, and excessive oxygen can cause casting blank pores and seriously affect the low-temperature toughness, so that the oxygen is strictly limited to be less than or equal to 20 multiplied by 10 -4%.
The N content of the invention is not more than 22 multiplied by 10 -4%, nitrogen in the steel can form large-size TiN inclusion with titanium, cold working cracks are easy to cause, and solid solution nitrogen in the steel is easy to cause strain aging and is unfavorable for low-temperature toughness, so that the nitrogen is strictly limited to not more than 22 multiplied by 10 -4%.
The H content of the invention is less than or equal to 0.5X10 -4%, hydrogen belongs to harmful elements in steel, which is easy to cause defects of hydrogen embrittlement, white spots, micropores and the like, and seriously worsens the low-temperature toughness, so the hydrogen must be strictly limited to less than or equal to 0.5X10 -4%.
As is less than or equal to 0.0003%, sn is less than or equal to 0.0003%, arsenic and tin are easy to be biased to grain boundaries, the cold brittleness of the grain boundaries is increased, and the strength and the low-temperature toughness of the grain boundaries are deteriorated, so that the arsenic and the tin are strictly limited to be less than or equal to 0.0003%.
Meanwhile, the chemical components also have to satisfy the formula: ca/S=5.0-6.0,0.64.ltoreq.C+Mn/6+ (Cr+Mo)/5.ltoreq.0.67. The calcium of the invention changes the spheroidized MnS inclusion, improves the low-temperature toughness, and can also form calcium oxide with oxygen to play a deoxidization role, thereby purifying the steel and improving the metallurgical quality of casting blanks, when Ca/S is less than 5.0, the calcium can not play the role, and when Ca/S is more than 6.0, the calcium-containing large-scale oxide sulfide compound inclusion is easy to form, which is not beneficial to the low-temperature toughness; when C+Mn/6+ (Cr+Mo)/5 < 0.64, the steel is not ensured to be strong in hardness, and also is disadvantageous in strong in uniformity of hardness in the thickness direction, and when C+Mn/6+ (Cr+Mo)/5 > 0.67, the low-temperature toughness is drastically deteriorated.
The steel of the invention contains the chemical components, and the balance of Fe and unavoidable impurities.
The thickness of the finished steel plate prepared by the method and the casting blank component is 50-80 mm, the surface hardness HBW10/3000 is 530-550, the core hardness is more than 95% of the surface hardness, and the KV 2 at-40 ℃ is more than or equal to 100J.
Compared with the prior art, the invention has the advantages of no need of adding Ni noble metal, low alloy cost, simple and easy production process, large-scale implementation in various metallurgical enterprises, and high low-temperature toughness and good thickness-direction hardness uniformity of the finished steel plate produced by the method.
Detailed Description
In order to better explain the technical solution of the present invention, the following description of the technical solution of the present invention is given by way of example only and not by way of limitation in any way, in conjunction with specific examples. All changes and equivalents that do not depart from the gist of the invention are intended to be within the scope of the invention.
Table 1 below shows the weight percentage content value list of chemical components in each example and comparative example of the present invention;
Table 2 below is a list of values of the main process parameters for each example of the present invention and comparative example;
Table 3 below shows the results of mechanical property measurements (average of three measured data) for each of the examples and comparative examples of the present invention.
The respective thicknesses of the finished steel sheets in examples 1 to 8 were 50mm, 55mm, 60mm, 65mm, 70mm, 75mm and 80mm, respectively, and the respective thicknesses of the finished steel sheets in comparative examples 1 to 3 were 60mm, 70mm and 80mm, respectively.
The invention relates to a production method of a high-toughness wear-resistant steel plate with uniform hardness in the thickness direction, which comprises the following steps:
(1) Refining outside a furnace: LF treatment time is 42-45 min, and outbound S is less than or equal to 0.001; RH extreme vacuum degree is less than 67Pa, the time of the extreme vacuum treatment is 16-20 min, and argon is continuously blown for 8-10 min after calcium wire feeding;
(2) Continuous casting: the whole process is protected and poured, the superheat degree is 5-10 ℃, and the slow cooling time of a casting blank slow cooling pit is more than 72 hours;
(3) Heating: heating temperature is 1280-1310 ℃, soaking temperature is 1250-1260 ℃, and soaking time is more than or equal to 72min;
(4) Rolling: two-stage rolling is adopted, and I-stage rough rolling is adopted: firstly removing phosphorus from the casting blank by high-pressure water after the casting blank is discharged, enabling the surface and the core of the casting blank to have a temperature difference of 100-300 ℃, then immediately rough rolling for 3-5 times, and enabling the single rolling reduction to be 35-45 mm until the thickness of a rolled piece is 2.5 times that of a finished product; and II, finish rolling: water-cooling the surface of a rolled piece to 950-980 ℃, then finish rolling for 4-5 times, wherein the single rolling reduction is 25-35 mm, and the final rolling temperature is 890-910 ℃;
(5) And (3) cooling: the water cooling start temperature of the steel plate is more than or equal to 860 ℃, the cooling speed is more than 50 ℃/s, and the redback temperature is less than or equal to 120 ℃;
(6) And (3) heat treatment: quenching temperature is 900-920 ℃, and the furnace time is 1.8XH+ (20-25) min; tempering the quenched steel plate within 24 hours after cooling to room temperature, wherein the tempering temperature is 150-260 ℃, and the furnace time is 4.8 XH for min; where H is the thickness of the finished steel sheet in mm.
The thickness of the casting blank is 300-320 mm.
The casting blank contains the following chemical components ：C：0.27～0.32%,Si：0.20～0.50%,Mn：0.85～1.20%,P≤0.002%,S≤0.0005%,Cr：0.52～0.76%,Mo：0.24～0.43%,Nb：0.026～0.048%,Ti：0.012～0.023%,B：0.0015～0.0027%,Ca：0.0012～0.0030%,O≤20×10-4%,N≤22×10-4%,H≤0.5×10-4%,As≤0.0003%,Sn≤0.0003%, in percentage by weight, the balance being Fe and unavoidable impurities, and the chemical components also have to satisfy the formula: ca/S=5.0-6.0,0.64.ltoreq.C+Mn/6+ (Cr+Mo)/5.ltoreq.0.67.
Table 1 list of chemical component weight percent content values for each example and comparative example of the present invention
Table 2 list of values of the main process parameters of the examples and comparative examples of the present invention
TABLE 3 mechanical property test results for various examples and comparative examples of the present invention
As can be seen from the test performance results in Table 3, the ratio of the core hardness to the surface hardness of examples 1 to 8 is 95% or more at the 1/4 or 1/2 plate width, the impact energy at-40℃is 102 to 137J, the ratio of the core hardness to the surface hardness of comparative examples 1 to 3 is less than 75%, and the impact energy at-40℃is only 39 to 51J, so that the steel sheet of the present invention has more excellent low-temperature toughness and thickness-direction hardness uniformity. Compared with the prior art, the invention has the advantages of no need of adding Ni noble metal, low alloy cost, simple and easy production process, large-scale implementation in various metallurgical enterprises, high-low temperature toughness and good thickness-direction hardness uniformity of the finished steel plate produced by the method, and can be widely applied to large-scale mechanical equipment in severe environments such as agriculture, engineering, mining, ports, metallurgy, electric power and the like.
The above-described embodiments are merely specific examples of the present invention for illustrating the present invention and are not to be construed as limiting the present invention in any way, and any insubstantial changes made in the above-described embodiments without departing from the scope of the claims of the present invention should be construed as falling within the scope of the claims of the present invention.

Claims (3)

1. The production method of the high-toughness wear-resistant steel plate with uniform hardness in the thickness direction is characterized by comprising the following steps:
(1) Refining outside a furnace: LF treatment time is 42-45 min, and outbound S is less than or equal to 0.001; RH extreme vacuum degree is less than 67Pa, the time of the extreme vacuum treatment is 16-20 min, and argon is continuously blown for 8-10 min after calcium wire feeding;
(2) Continuous casting: the whole process protection casting is carried out, the thickness of a casting blank is 300-320 mm, the superheat degree is 5-10 ℃, and the slow cooling time of a casting blank slow cooling pit is more than 72h;
(3) Heating: heating temperature is 1280-1310 ℃, soaking temperature is 1250-1260 ℃, and soaking time is more than or equal to 72min;
(4) Rolling: two-stage rolling is adopted, and I-stage rough rolling is adopted: firstly removing phosphorus from the casting blank by high-pressure water after the casting blank is discharged, enabling the surface and the core of the casting blank to have a temperature difference of 100-300 ℃, then immediately rough rolling for 3-5 times, and enabling the single rolling reduction to be 35-45 mm until the thickness of a rolled piece is 2.5 times that of a finished product; and II, finish rolling: water-cooling the surface of a rolled piece to 950-980 ℃, then finish rolling for 4-5 times, wherein the single rolling reduction is 25-35 mm, and the final rolling temperature is 890-910 ℃;
(5) And (3) cooling: the water cooling start temperature of the steel plate is more than or equal to 860 ℃, the cooling speed is more than 50 ℃/s, and the redback temperature is less than or equal to 120 ℃;
(6) And (3) heat treatment: quenching temperature is 900-920 ℃, and the furnace time is 1.8XH+ (20-25) min; tempering the quenched steel plate within 24 hours after cooling to room temperature, wherein the tempering temperature is 150-260 ℃, and the furnace time is 4.8 XH for min; wherein H is the thickness of the finished steel plate in mm;
The casting blank contains the following chemical components ：C：0.27～0.32％,Si：0.20～0.50％,Mn：0.85～1.20％,P≤0.002％,S≤0.0005％,Cr：0.52～0.76％,Mo：0.24～0.43％,Nb：0.026～0.048％,Ti：0.012～0.023％,B：0.0015～0.0027％,Ca：0.0012～0.0030％,O≤20×10-4％,N≤22×10-4％,H≤0.5×10-4％,As≤0.0003％,Sn≤0.0003％, in percentage by weight, the balance being Fe and unavoidable impurities, and the chemical components also have to satisfy the formula: ca/S=5.0-6.0,0.64.ltoreq.C+Mn/6+ (Cr+Mo)/5.ltoreq.0.67.
2. The method for producing a high-toughness wear-resistant steel sheet having uniform hardness in the thickness direction according to claim 1, wherein: the thickness of the finished steel plate is 50-80 mm, the surface hardness HBW10/3000 is 530-550, the core hardness is more than 95% of the surface hardness, and the KV 2 at-40 ℃ is more than or equal to 100J.
3. The method for producing a high-toughness wear-resistant steel sheet having uniform hardness in the thickness direction according to claim 1, wherein: the casting blank contains the following chemical components ：C：0.27～0.32％,Si：0.25～0.45％,Mn：0.88～1.12％,P≤0.002％,S≤0.0005％,Cr：0.55～0.72％,Mo：0.27～0.41％,Nb：0.029～0.045％,Ti：0.014～0.021％,B：0.0017～0.0025％,Ca：0.0014～0.0026％,O≤20×10-4％,N≤22×10-4％,H≤0.5×10-4％,As≤0.0003％,Sn≤0.0003％, in percentage by weight, the balance being Fe and unavoidable impurities, and the chemical components also have to satisfy the formula: ca/s=5.0 to 6.0; C+Mn/6+ (Cr+Mo)/5.ltoreq.0.64.ltoreq.0.67.
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