High-toughness thick anti-crack wear-resistant steel plate and production method thereof

Abstract

The invention relates to the technical field of high-toughness thick-specification wear-resistant steel plates, in particular to a high-toughness thick-specification crack-resistant wear-resistant steel plate and a production method thereof. The high-strength steel is composed of the following chemical components in percentage by weight: 0.12%-0.16% of C, 1.15%-1.30% of Si, 1.0%-1.2% of Mn, 0.015%-0.03% of Nb, 0.30%-0.40% of Mo, 0.06%-0.09% of Al, 0.0005%-0.0020% of B, more than or equal to 1.4% and less than or equal to 1.6% of Mn and Mo, and the balance of Fe and inevitable impurities. The production process flow comprises the steps of smelting, refining, slab continuous casting, casting blank heating and slow cooling, slab heating, controlled rolling, stacking and slow cooling (tempering), quenching and tempering heat treatment, flame temperature cutting and hot water slow cooling. And during flame cutting, thermal stress and structural stress formed in the cutting process of the thick steel plate are reduced through the cutting process of cutting with temperature and slow cooling with hot water after cutting, and the effect of no delayed crack after cutting is achieved. And the flame cutting delayed crack-free wear-resistant steel plate with the thickness of 40-80 mm and the surface Brinell hardness of 400 HB can be produced.

Description

Technical Field

[0001] The present invention relates to the technical field of high-toughness thick-specification wear-resistant steel plates, and particularly to a high-toughness thick-specification crack-resistant wear-resistant steel plate and a production method thereof. Background Art

[0002] The low-alloy wear-resistant steel of HB400 grade belongs to medium-high hardness, has good wear resistance and high toughness, and can withstand higher impact loads. It is applicable to dynamic load scenarios, such as the bucket of an excavator, the cutting edge plate of a loader, the blade of a bulldozer, the lining plate of a concrete mixer, etc. in construction machinery; the lining plate of a crusher, the chute of a conveyor, screening equipment, the car body of a mine car, etc. in mining equipment; the crushing roller of a cement plant, the blade of a straw crusher, a plowshare, the threshing parts of a harvester, etc. in building materials and agricultural machinery; the lining plate of the car body of a dump truck, a hopper, a conveying pipeline, etc. in transportation equipment; the guide guard plate of a rolling mill, the slide rail of a cooling bed, steel slag treatment equipment, etc. in the metallurgical industry. The structure of the wear-resistant steel is mainly martensitic steel, which is produced by a heat treatment process of quenching followed by low-temperature tempering.

[0003] Flame cutting is a common blanking method for wear-resistant steel plates, with low cost, high efficiency and wide application range. At present, the phenomenon of delayed cracking often occurs after the flame cutting of HB400 wear-resistant steel plates with a thickness specification of 40 - 80 mm, bringing potential safety hazards to production and use. The delayed crack in the wear-resistant steel plate cutting is the result of embrittlement under the interaction of the internal defects of the steel plate, hydrogen and cutting stress. The occurrence time of the delayed crack is uncertain. Usually, the steel plate will undergo brittle failure statically several hours or days after flame cutting, which is one of the common quality defects of wear-resistant steel plates and is extremely harmful. How to reduce the delayed fracture resistance after the flame cutting of high-hardness thick-specification wear-resistant plates has become an urgent problem to be solved by domestic and foreign steel mills and users.

[0004] The Chinese patent document with publication number CN115369303A discloses "A kind of HB400 grade crack-resistant high-strength martensitic wear-resistant steel and production method", which is a non-quenched and tempered steel. The hardness of the steel plate is unevenly distributed due to the influence of cooling rate, the plastic toughness is low, thick-specification wear-resistant steel plates cannot be produced, and there is no special cutting method. The Chinese patent document with publication number CN109072367A discloses "Wear-resistant steel plate and manufacturing method thereof". The alloy composition of this steel plate is complex, the cost is high, and it has no ability to resist delayed cracking. The Chinese patent document with publication number CN114850618A discloses "Cutting method for reducing edge cracks of steel plates", which is a cutting method for wear-resistant steel. It is necessary to use a double-flame gun for preheating and heat preservation. The heat-affected zone is wide, and the hardness of the flame-cut edge drops greatly. The Chinese patent document with publication number CN111270042A discloses "A method for controlling hydrogen-induced cracks in high carbon equivalent steel plates". The cutting process of this steel plate is only applicable to hot-rolled steel plates with high carbon equivalent, not applicable to wear-resistant steel plates delivered in the heat-treated state. Moreover, there is no effective slow cooling after cutting, the internal stress of the steel plate is large, and it is easy to crack. The Chinese patent document with publication number CN114147434A discloses "A method for improving the cutting quality of medium and high carbon steel in ultra-thick plates". This method can cut thick-specification steel plates, but if the stress-relieving annealing heating temperature is too high, the hardness of the wear-resistant steel will decrease, affecting the wear resistance. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a high-toughness thick-specification crack-resistant wear-resistant steel plate and its production method, which can produce a wear-resistant steel plate with a thickness specification of 40-80 mm and a surface Brinell hardness of 400 HB grade without post-flame-cutting delayed cracks.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A high-toughness thick-specification crack-resistant wear-resistant steel plate, without post-flame-cutting delayed cracks, surface hardness ≥ HB400, thickness 40-80 mm, tensile strength ≥ 1200 MPa, cut-edge hardness ≥ HB370, -40 °C AKV ≥ 50 J, A ≥ 13%.

[0008] It is composed of chemical components with the following weight percentages: C: 0.12% - 0.16%, Si: 1.15% - 1.30%, Mn: 1.0% - 1.2%, Nb: 0.015% - 0.03%, Mo: 0.30% - 0.40%, Al: 0.06% - 0.09%, B: 0.0005% - 0.0020%, 1.4% ≤ Mn + Mo ≤ 1.6%, and the balance is Fe and unavoidable impurities.

[0009] Control of impurity elements in wear-resistant steel plates: P ≤ 0.012%, S ≤ 0.002%, [N] ≤ 0.0040%, [H] ≤ 0.00010%, [O] ≤ 0.0010%, and the retained austenite content is 6.1% - 8.0%.

[0010] In the design of the steel plate composition of the present invention:

[0011] C: To ensure that the surface of the steel plate has a hardness of HB400 after quenching, it can also improve the hardenability of thick-specification steel plates and ensure uniform wear resistance along the thickness direction of the steel plate. At the same time, carbon can form carbides with Mo and precipitate, increasing wear resistance. When the carbon content is too high, the crack sensitivity after cutting increases. To ensure that the steel plate has high wear resistance and good resistance to delayed cracking, the C content in the present invention is controlled at 0.12% - 0.16%.

[0012] Si: The key element added in the present invention, a non-carbide-forming element, mainly functions to inhibit the precipitation of carbides, stabilize the retained austenite content in the steel, and the retained austenite can act as a hydrogen trap during flame cutting to inhibit the formation and propagation of delayed cracks. A certain amount of retained austenite is also beneficial to improving the toughness of the steel plate. However, when Si is excessive, the surface quality and welding performance will decline. Therefore, the Si content in the present invention is controlled at 1.15% - 1.30%;

[0013] Mn: It has the effect of delaying the transformation of austenite to ferrite, promoting martensite transformation, and improving hardenability. However, it is prone to form center segregation, and there is a tendency to easily generate delayed cracks in the center of the steel plate thickness during flame cutting; therefore, the Mn content in the present invention is controlled at 1.0% - 1.2%;

[0014] Nb: The most effective element for controlled rolling. During the two-stage rolling process, its carbon and nitrogen compounds inhibit austenite recrystallization, refine austenite grains, and after quenching, refined martensite lath bundles can be formed, and the refined martensite can effectively prevent the occurrence of delayed cracks in the steel plate cutting. However, if the Nb content is too high, excessive precipitation of carbon and nitrogen compounds will affect the steel plate's resistance to delayed cracking. Therefore, the addition amount of Nb in the present invention is 0.015% - 0.03%.

[0015] AL: An effective element for deoxidation and nitrogen fixation. Deoxidation can reduce oxide inclusions in the steel and purify the steel quality, and nitrogen fixation after deoxidation can ensure that element B does not combine with N and play the role of B in improving hardenability. Excessive content will cause casting difficulties and also form a large amount of Al2O3 inclusions in the steel, which are likely to become the initiation source of delayed cracks after cutting. Therefore, in the present invention, Al is 0.06% - 0.09%,

[0016] Mo: It has the effect of reducing the critical cooling rate, promoting the transformation of martensite, and improving the hardenability of the steel plate. In addition, Mo is a strong carbide-forming element and can form various carbides in the steel to ensure the wear resistance of the steel plate. However, excessive addition of Mo will increase the crack sensitivity after thermal cutting. Therefore, in the present invention, the content of Mo is controlled at 0.30% - 0.40%. Since both Mn and Mo can improve the hardenability, excessive addition will increase the risk of cracking after thermal cutting. To ensure that no delayed fracture occurs during the cutting of the steel plate, in the present invention, 1.4% ≤ Mn + Mo ≤ 1.6%.

[0017] B: Trace amounts of boron (when greater than 0.0005%) can inhibit the formation of proeutectoid ferrite and greatly improve the hardenability. When the content of B is too high (≥0.0025%), the cooling rate in the heat-affected zone after thermal cutting is slow, and B is easily enriched at the grain boundaries, which will reduce the grain boundary binding energy and cause the heat-affected zone after thermal cutting to easily form intergranular fractures under the action of residual stress. Therefore, in the present invention, the addition amount of B is 0.0005% - 0.0020%.

[0018] Retained austenite and impurity elements: 6.1 - 8.0% of retained austenite in the cutting edge and heat-affected zone during flame cutting can act as hydrogen traps to inhibit the propagation of delayed cracks and ensure that the steel plate has good crack arrest ability after cutting. Excessive content of retained austenite will reduce the hardness and wear resistance of the steel plate. The aggregation of impurity elements P, S, O, N, especially H in the steel plate will act as crack initiation sources, significantly reducing the crack arrest ability of the steel plate and increasing the risk of forming delayed cracks after thermal cutting. Therefore, in the present invention, to ensure good anti-delayed fracture performance, the content of impurity element P is controlled at ≤0.012%, S ≤0.002%, [H] ≤0.00010%, [O] ≤0.0010%, and [N] ≤0.0040%.

[0019] The production method of the above-mentioned high-toughness thick-specification crack-resistant wear-resistant steel plate has a production process flow as follows: smelting → refining → slab continuous casting → casting blank heating and slow cooling → slab heating → controlled rolling → stacking and slow cooling (tempering) → quenching + tempering heat treatment → flame cutting with temperature maintained → hot water slow cooling.

[0020] This production method specifically includes the following steps:

[0021] 1) Refining:

[0022] Control the RH degassing time, and the RH vacuum circulation time ≥ 18 min;

[0023] 2) Slab continuous casting:

[0024] The target superheat of the tundish ≤ 20°C; the center segregation of the casting blank is controlled below C1.0, and the inclusions A + B + C + D ≤ 3.5;

[0025] 3) Casting blank heating and slow cooling:

[0026] The slow cooling start temperature is ≥400°C, heated at a heating rate of ≤50°C / second to 600 - 650°C, held for 13 - 18 hours, then slowly cooled in the furnace to less than 400°C, and taken out of the furnace and air-cooled to room temperature;

[0027] 4) Slab heating:

[0028] The temperature of the heating and soaking section is 1200 - 1250°C, and the soaking time is greater than 2.5 hours;

[0029] 5) Controlled rolling:

[0030] Two-stage controlled rolling of rough rolling and finish rolling is adopted. In the rough rolling stage, the rolling start temperature is ≥1020°C, and the finish rolling temperature is controlled at ≥980°C; the finish rolling start temperature is 870 - 900°C, the finish rolling reduction ratio is ≥50%, and the finish rolling temperature is 820 - 860°C;

[0031] 6) Stacking slow cooling:

[0032] If the off-line temperature of the hot-rolled steel plate is ≥500°C, then stacking slow cooling is carried out, the holding time is greater than or equal to 32 hours, and after cooling to 350 - 400°C, it is air-cooled to room temperature;

[0033] If the off-line temperature of the hot-rolled steel plate is <450°C, then high-temperature tempering is carried out. The tempering heating temperature is 650 - 700°C, the holding time is 120 - 150 min. After tempering, the steel plate is stacked and slowly cooled, the stacking time is greater than or equal to 24 hours, and after the unstacking temperature is 350 - 400°C, it is air-cooled to room temperature;

[0034] 7) Quenching + tempering heat treatment:

[0035] The quenching temperature is 880 - 920°C, and the holding time is 2 - 2.5 min / mm;

[0036] The tempering temperature is 220 - 250°C, and the low-temperature tempering holding time is 8 - 10 min / mm;

[0037] 8) Flame cutting with temperature maintained:

[0038] The temperature of the steel plate at the flame cutting position is ≥80°C;

[0039] If the temperature is lower than 80°C, then the cutting position is preheated, the preheating temperature is 100 - 150°C, and the preheating width is 100 mm on both sides of the cutting edge;

[0040] During flame cutting, slow cutting is carried out, and the cutting speed is ≤180 mm / min;

[0041] 9) Slow cooling in hot water

[0042] After the steel plate is cut, it is slowly cooled in a hot water pool, and the cut steel plate is held in water at a high temperature of 80 - 100°C for more than 2 hours.

[0043] Further, in step 2), during continuous casting, the whole pouring process is carried out under protective casting to prevent hydrogen from entering the tundish.

[0044] Further, in step 2), electromagnetic stirring or soft reduction is adopted during continuous casting to reduce central segregation.

[0045] Further, in step 4), the thickness of the slab is 250 - 300 mm to ensure the compression ratio.

[0046] Further, in step 6), it is stacked and slowly cooled in a slow cooling pit and covered for heat preservation.

[0047] Further, in step 8), a flame burning torch or an electronic heating pad is used to preheat the cutting position.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] 1. The present invention adopts a new composition and process design for preventing delayed cracks in flame cutting. The chemical composition of the steel plate is mainly characterized by medium carbon, high silicon, and niobium microalloying. After refining, continuous casting, controlled rolling, and heat treatment, a wear-resistant steel plate with low impurity content, uniform, fine martensite, and a certain amount of retained austenite structure is obtained, which can inhibit the formation and propagation of delayed cracks during flame cutting. During flame cutting, through the cutting process of cutting with temperature and hot water slow cooling after cutting, the thermal stress and tissue stress formed during the cutting of thick - specification steel plates are reduced, achieving the effect of no delayed cracks after cutting.

[0050] 2. The present invention uses Si to inhibit the precipitation of carbides. Si is a non - carbide - forming element, and its main function is to inhibit the precipitation of carbides and stabilize the content of retained austenite in the steel. During flame cutting, the retained austenite can act as a hydrogen trap to inhibit the formation and propagation of delayed cracks, and a certain amount of retained austenite is also beneficial to improving the toughness of the steel plate. At the same time, the contents of C, Mn, Nb, AL, Mo, and B are controlled to ensure that the steel plate has high wear resistance and good resistance to delayed cracks. During flame cutting, 6.1 - 8.0% of the retained austenite near the cutting edge can act as a hydrogen trap to inhibit the propagation of delayed cracks, ensuring that the cutting edge of the steel plate has good crack - stopping ability. Excessive content of retained austenite will reduce the hardness and wear resistance of the steel plate. Impurity elements, especially H, will act as crack initiation sources in the steel plate, significantly reducing the crack - stopping ability of the steel plate and increasing the risk of forming delayed cracks after flame cutting. To ensure good anti - delayed fracture performance, the present invention controls the impurity elements P≤0.012%, S≤0.002%, [H]≤0.00010%, [O]≤0.0010%, [N]≤0.0040%.

[0051] 3. During the refining process of the present invention, the RH degassing time is controlled. Through long-term vacuum treatment, the content of [N] in the molten steel can be controlled to ≤0.0040%, [O] to ≤0.0010%, and [H] to ≤0.00010%. The center segregation of the continuous casting billet is controlled below C1.0, and the inclusions A + B + C + D ≤ 3.5, thereby reducing the segregation and inclusions from becoming the initiation points of delayed cracks. The hydrogen content and the internal stress during casting in the steel billet are removed by heating and slow cooling.

[0052] 4. In the present invention, through long-term high-temperature heating, the carbon and alloying elements in the core of the steel plate are fully diffused, further improving the center segregation. During rolling, two-stage controlled rolling of rough rolling and finish rolling is adopted to fully refine and homogenize the hot-rolled structure.

[0053] 5. After hot rolling, the steel plate of the present invention is taken offline and stacked in a slow-cooling pit for slow cooling or subjected to high-temperature tempering. By utilizing the different solubility of hydrogen in steel at different temperatures, the hydrogen inside the thick-specification steel plate is removed by diffusion. At the same time, by balancing the temperature of the steel plate, the internal stress of the steel plate is removed.

[0054] 6. The present invention reduces the temperature difference between the surface and the core of the cutting edge by cutting with temperature and preheating, reduces the thermal stress during cutting, and at the same time can prevent the condensed water formed on the surface of the steel plate during cutting from entering the gas-cutting surface in an atomic state to form hydrogen-induced cracks.

[0055] During oxygen cutting, slow cutting is adopted to reduce the cutting thermal stress. After the steel plate is cut, it is slowly cooled in a hot water pool. Cooling in hot water can quickly make the temperature of the surface and the core of the cutting-edge steel plate reach the same, reducing the thermal stress and tissue stress formed after cutting. At the same time, the rapid cooling of the cutting surface in hot water can also reduce the decrease in the surface hardness of the cutting surface and improve the wear resistance of the steel plate. After cutting, the steel plate is kept warm in water at a high temperature of 80 - 100°C for more than 2 hours, which can fully homogenize the overall temperature of the steel plate, further reduce the cutting residual stress, and avoid the occurrence of delayed cracks.

[0056] In summary, for the steel plate of the present invention, the surface hardness ≥ HB400, the thickness is 40 - 80 mm, the tensile strength ≥ 1200 MPa, the retained austenite content is 6.1% - 8.0%, there are no delayed cracks after oxygen cutting, the hardness of the cut edge ≥ HB370, -40°C AKV ≥ 50 J, and A ≥ 13%. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is the coloring flaw detection diagram of the cutting surface of the 80-mm-thick steel plate of the present invention 48 hours after oxygen cutting. DETAILED DESCRIPTION OF THE INVENTION

[0058] The present invention discloses a high-toughness thick-specification crack-resistant wear-resistant steel plate and a production method thereof. Those skilled in the art can draw on the content of this article and appropriately improve the process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the present invention. The method and application of the present invention have been described through preferred embodiments. Relevant personnel can obviously make changes or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention.

[0059] A high-toughness thick-specification crack-resistant wear-resistant steel plate is composed of chemical components with the following weight percentages: C: 0.12% - 0.16%, Si: 1.15% - 1.30%, Mn: 1.0% - 1.2%, Nb: 0.015% - 0.03%, Mo: 0.30% - 0.40%, Al: 0.06% - 0.09%, B: 0.0005% - 0.0020%, 1.4% ≤ Mn + Mo ≤ 1.6%, and the balance is Fe and inevitable impurities.

[0060] Control of impurity elements in the wear-resistant steel plate: P ≤ 0.012%, S ≤ 0.002%, [N] ≤ 0.0040%, [H] ≤ 0.00010%, [O] ≤ 0.0010%, and the retained austenite content is 6.1% - 8.0%.

[0061] The production method of the above-mentioned high-toughness thick-specification crack-resistant wear-resistant steel plate has a production process flow: smelting → refining → slab continuous casting → casting blank heating and slow cooling → slab heating → controlled rolling → stacking slow cooling (tempering) → quenching + tempering heat treatment → flame cutting → hot water slow cooling.

[0062] Specifically as follows:

[0063] The production process flow of the present invention is: smelting → refining → slab continuous casting → casting blank heating and slow cooling → slab heating → controlled rolling → stacking slow cooling (tempering) → quenching + tempering heat treatment → flame cutting with temperature → hot water slow cooling

[0064] 1. Smelting process:

[0065] During the refining of the present invention, the RH degassing time is controlled, and the RH vacuum circulation time ≥ 18 min. Through long-term vacuum treatment, the molten steel [N] ≤ 0.0040%, [O] ≤ 0.0010%, and [H] ≤ 0.00010% can be controlled.

[0066] The characteristics of the continuous casting of the present invention are: the target superheat of the tundish is controlled at ≤ 20°C; the whole process is protected by pouring to prevent hydrogen from entering the tundish; electromagnetic stirring or soft reduction is used during continuous casting to reduce central segregation.

[0067] The center segregation of the continuous casting billet is required to be controlled below C1.0, and the sum of inclusions A+B+C+D ≤ 3.5, aiming to reduce the segregation and inclusions from becoming the initiation points of delayed cracks.

[0068] After the slab continuous casting is taken offline, it needs to enter the slow cooling pit for heating and slow cooling. The starting temperature of slow cooling is required to be ≥ 400°C, heated at a heating rate of ≤ 50°C / second to 600 - 650°C, held for 13 - 18 hours, and then slow cooled with the furnace to below 400°C and taken out of the furnace for air cooling to room temperature. The purpose of heating and slow cooling is to remove the hydrogen content and casting internal stress in the steel billet.

[0069] 2. Rolling process:

[0070] The temperature of the heating and soaking section is 1200 - 1250°C, the thickness of the continuous casting billet is 250 - 300 mm, and the soaking time is more than 2.5 hours.

[0071] Purpose: Through long-time high-temperature heating, the carbon and alloy in the center of the steel plate are fully diffused to further improve the center segregation.

[0072] Two-stage controlled rolling is adopted during rolling, aiming to fully refine and homogenize the hot-rolled structure. In the rough rolling stage, the starting rolling temperature is ≥ 1020°C, and the finishing rolling temperature is controlled at ≥ 980°C; the starting rolling temperature of the finishing rolling is 870 - 900°C, the reduction rate of the finishing rolling is ≥ 50%, aiming to refine the original austenite structure, and the finishing rolling temperature is 820 - 860°C.

[0073] 3. Post-rolling dehydrogenation process:

[0074] After the hot-rolled steel plate is taken offline, it enters the slow cooling pit for stacking and slow cooling or undergoes high-temperature tempering. If the offline temperature of the hot-rolled steel plate is ≥ 500°C, then stacking and slow cooling are carried out, and the holding time is greater than or equal to 32 hours, and then air cooled to room temperature after reaching 350 - 400°C. If the offline temperature of the hot-rolled steel plate is < 450°C, then high-temperature tempering is carried out, the tempering heating temperature is 650 - 700°C, the holding time is 120 - 150 min, and after tempering, the steel plate is stacked and slow cooled, the stacking time is greater than or equal to 24 hours, and air cooled to room temperature after the unstacking temperature reaches 350 - 400°C.

[0075] The purpose of slow cooling in the slow cooling pit by stacking and slow cooling after high-temperature tempering is to utilize the different solubilities of hydrogen in steel at different temperatures, remove the hydrogen inside the thick-specification steel plate through diffusion, and at the same time remove the internal stress of the steel plate by equalizing the steel plate temperature.

[0076] 4. Heat treatment process:

[0077] The quenching temperature is 880 - 920°C, the holding time is 2 - 2.5 min / mm, and the purpose of quenching is to obtain a hardness of HB400. The tempering temperature is 220 - 250°C, and the holding time of low-temperature tempering is 8 - 10 min / mm, aiming to remove the internal stress formed during the quenching of the steel plate.

[0078] 5. Flame cutting process:

[0079] After low-temperature tempering heat treatment, the steel plate is cut to size and sampled with warm flame cutting. It is required that the temperature of the steel plate at the flame cutting position is ≥80°C. If the cutting temperature is lower than 80°C, the cutting position is preheated. The preheating temperature is required to be 100°C - 150°C, and the preheating width is 100 mm on both sides of the cutting edge. A flame torch or an electronic heating pad can be used. The purpose of warm and preheated cutting is to reduce the temperature difference between the surface and the core of the cutting edge, reduce the thermal stress during cutting, and at the same time prevent the condensed water formed on the surface of the steel plate during cutting from entering the gas cutting surface in an atomic state to form hydrogen-induced cracks.

[0080] During flame cutting, slow cutting should be carried out, and the cutting speed ≤180 mm / min. The purpose of slow cutting is to reduce the cutting thermal stress. After the steel plate is cut, it is lifted into a hot water pool by a crane for slow cooling. The temperature of the slow cooling water is 80 - 100°C, and the insulation time in the water is more than 2 hours. Cooling in hot water can quickly make the temperature of the surface and the core of the cutting edge steel plate reach the same, reduce the thermal stress and tissue stress formed after cutting. At the same time, the rapid cooling of the cutting surface in hot water can also reduce the decrease in the surface hardness of the cutting surface and improve the wear resistance of the steel plate.

[0081] After cutting, the steel plate is insulated in water at a high temperature of 80 - 100°C for more than 2 hours, which can make the overall temperature of the steel plate fully uniform, further reduce the cutting residual stress, and avoid the occurrence of delayed cracks.

[0082] For the steel plate produced by the above production method, there are no delayed cracks after flame cutting, the hardness of the cut edge ≥HB370, the surface hardness ≥HB400, the thickness is 40 - 80 mm, the tensile strength ≥1200 MPa, -40°C AKV ≥50 J, and A ≥13%.

[0083]

Example

[0084] According to the chemical composition and production process of the present invention, the actual chemical composition of the steel grade of the present invention during smelting is shown in Table 1, the smelting process is shown in Table 2, the actual rolling process parameters of the steel examples of the present invention are shown in Table 3, the post-rolling dehydrogenation process parameters are shown in Table 4, the heat treatment process parameters are shown in Table 5, the physical property test results of the present invention are shown in Table 6, and the cutting process and delayed crack test results are shown in Table 7.

[0085] Table 1 Examples of the smelting composition of the steel grade of the present invention, Wt%

[0086]

[0087] Table 2 The smelting process of the steel grade of the present invention

[0088]

[0089] Table 3 The actual rolling process parameters of the steel examples of the present invention

[0090]

[0091] Table 4 Post-rolling dehydrogenation process parameters of the steel of the present invention

[0092]

[0093] Table 5 Heat treatment process of the steel examples of the present invention

[0094]

[0095] Table 6 Mechanical properties of the steel embodiments of the present invention

[0096]

[0097] Table 7 Flame cutting process and crack inspection of the steel examples of the present invention

[0098]

[0099] Figure 1 is the coloring flaw detection diagram of the cutting surface of the 80-mm-thick steel plate of the present invention after 48 hours of flame cutting, as Figure 1 shown. After 48 hours of slow cooling, the coloring flaw detection method is used to check the delayed crack situation on the flame cutting surface of the steel plate of the present invention, and no delayed crack is found. It can be seen that the steel plate of the present invention has good resistance to delayed cracks.

[0100] The present invention adopts a new composition and process design for preventing flame cutting delayed cracks. The chemical composition of the steel plate is mainly characterized by medium carbon, high silicon, and niobium microalloying. After refining, continuous casting, controlled rolling, and heat treatment, a wear-resistant steel plate with low impurity content, uniform, fine martensite, and a certain amount of retained austenite structure can be obtained, which can inhibit the formation and propagation of delayed cracks during flame cutting. During flame cutting, through the cutting process of cutting with temperature and hot water slow cooling after cutting, the thermal stress and tissue stress formed during the cutting process of thick-specification steel plates are reduced, and the effect of no delayed cracks after cutting is achieved.

[0101] The surface hardness of the present invention is ≥HB400, the thickness is 40 - 80 mm, the tensile strength is ≥1200 MPa, the retained austenite content is 6.1% - 8.0%, there are no delayed cracks after flame cutting, the hardness of the cut edge is ≥HB370, AKV at -40°C ≥50 J, and A ≥13%.

[0102] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. High-toughness thick-specification crack-resistant wear-resistant steel plate, characterized in that, The wear-resistant steel plate has no post-flame-cutting delayed crack, its surface hardness ≥ HB400, thickness 40 - 80 mm, and is composed of chemical components with the following weight percentages as follows: C: 0.12% - 0.16%, Si: 1.15% - 1.30%, Mn: 1.0% - 1.2%, Nb: 0.015% - 0.03%, Mo: 0.30% - 0.40%, Al: 0.06% - 0.09%, B: 0.0005% - 0.0020%, 1.4% ≤ Mn + Mo ≤ 1.6%, and the balance is Fe and inevitable impurities.

2. The high-toughness thick-specification crack-resistant wear-resistant steel plate according to claim 1, characterized in that for the control of impurity elements in the wear-resistant steel plate: P ≤ 0.012%, S ≤ 0.002%, [N] ≤ 0.0040%, [H] ≤ 0.00010%, [O] ≤ 0.0010%, and the retained austenite content is 6.1% - 8.0%.

3. The high-toughness thick-specification crack-resistant wear-resistant steel plate according to claim 1, characterized in that the tensile strength of the wear-resistant steel plate ≥ 1200 MPa; the trimmed-edge hardness ≥ HB370.

4. The high-toughness thick-specification crack-resistant wear-resistant steel plate according to claim 1, characterized in that the wear-resistant steel plate has -40°C AKV ≥ 50 J; A ≥ 13%.

5. A production method of a high-toughness thick-specification crack-resistant wear-resistant steel plate as described in any one of claims 1-4, characterized in that, The production process flow is: smelting → refining → slab continuous casting → casting blank heating and slow cooling → slab heating → controlled rolling → stacking and slow cooling → quenching + tempering heat treatment → flame cutting with temperature maintained → hot water slow cooling; This production method specifically includes the following steps: 1) Refining: Controlling the RH degassing time, RH vacuum circulation time ≥ 18 min; 2) Slab continuous casting: The target superheat of the tundish ≤ 20°C; the center segregation of the casting blank is controlled below C1.0, and the inclusions A + B + C + D ≤ 3.5; 3) Casting blank heating and slow cooling: The slow cooling start temperature ≥ 400°C, heated to 600 - 650°C at a heating rate ≤ 50°C / second, held for 13 - 18 hours, then slowly cooled in the furnace to less than 400°C, and taken out of the furnace and air-cooled to room temperature; 4) Slab heating: The heating soaking section temperature is 1200 - 1250°C, and the soaking time is greater than 2.5 hours; 5) Controlled rolling: Two-stage controlled rolling of rough rolling and finish rolling is adopted. In the rough rolling stage, the rolling start temperature ≥ 1020°C, and the finish rolling temperature is controlled at ≥ 980°C; the finish rolling start temperature is 870 - 900°C, the finish rolling reduction rate ≥ 50%, and the finish rolling temperature is 820 - 860°C; 6) Stacking and slow cooling: If the off-line temperature of the hot-rolled steel plate ≥ 500°C, then stacking and slow cooling is carried out, the heat preservation time is greater than or equal to 32 hours, and after cooling to 350 - 400°C, it is air-cooled to room temperature; If the off-line temperature of the hot-rolled steel plate < 450°C, then high-temperature tempering is carried out, the tempering heating temperature is 650 - 700°C, the heat preservation time is 120 - 150 min, after tempering, the steel plate is stacked and slowly cooled, the stacking time is greater than or equal to 24 hours, and after the unstacking temperature is 350 - 400°C, it is air-cooled to room temperature; 7) Quenching + tempering heat treatment: The quenching temperature is 880 - 920°C, and the heat preservation time is 2 - 2.5 min / mm; The tempering temperature is 220 - 250°C, and the holding time for low-temperature tempering is 8 - 10 min / mm; 8) Flame cutting with temperature retention: The temperature of the steel plate at the flame cutting position is ≥80°C; If the temperature is lower than 80°C, preheat the cutting position. The preheating temperature is 100 - 150°C, and the preheating width is 100 mm on both sides of the cutting edge; During flame cutting, perform slow cutting, and the cutting speed ≤180 mm / min; 9) Slow cooling in hot water: After the steel plate is cut, it is slowly cooled in a hot water pool. The cut steel plate is held in water at a high temperature of 80 - 100°C for more than 2 hours.

6. The production method of the high-toughness thick-specification crack-resistant wear-resistant steel plate according to claim 5, characterized in that In step 2), during continuous casting, carry out whole-process protected casting to prevent hydrogen from entering the tundish.

7. The production method of the high-toughness thick-specification crack-resistant wear-resistant steel plate according to claim 5, characterized in that In step 2), during continuous casting, use electromagnetic stirring or soft reduction to reduce central segregation.

8. The production method of the high-toughness thick-specification crack-resistant wear-resistant steel plate according to claim 5, characterized in that In step 4), the thickness of the slab is 250 - 300 mm.

9. The production method of the high-toughness thick-specification crack-resistant wear-resistant steel plate according to claim 5, characterized in that In step 6), stack and slowly cool in a slow-cooling pit, and cover it for heat preservation.

10. The production method of the high-toughness thick-specification crack-resistant wear-resistant steel plate according to claim 5, characterized in that In step 8), use a flame torch or an electric heating pad to preheat the cutting position.

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