Production method for inhibiting straightening cracking of thin NM550 wear-resistant steel plate

Abstract

The invention discloses a production method for inhibiting straightening cracking of a thin NM550 wear-resistant steel plate, and belongs to the field of production of low-alloy high-strength steel. The problem of straightening cracking caused by air holes, inclusions and quenching internal stress is solved. The method comprises the following steps: casting molten steel into a plate blank with the thickness of 150-220mm, carrying out hydrogen diffusion in a heat preservation pit with the temperature of 650 + / -20 DEG C for 48 hours, and heating to 1150-1230 DEG C; the initial rough rolling temperature is 1100-1150 DEG C, the final rolling temperature is greater than or equal to 1040 DEG C, and the temperature holding thickness of an intermediate billet is 2.0-4.0 times that of a finished product; aCC cooling is carried out for 20-30 s to 860-880 DEG C, and then temperature equalization is carried out; initial rolling of finish rolling is less than or equal to 880 DEG C, final rolling is less than or equal to 830 DEG C, and controlled cooling is performed at the cooling speed of 8-15 DEG C / The self-tempering temperature is 450-600 DEG C, the quenching temperature is 850-950 DEG C, and the tempering temperature is 150-250 DEG C. According to the method, the hydrogen content of the steel plate is smaller than or equal to 2 ppm, the residual stress is smaller than or equal to 180 MPa, and straightening cracking is effectively inhibited.

Description

Technical Field

[0001] This invention belongs to the field of low-alloy high-strength steel production, and particularly relates to a production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates. Background Technology

[0002] NM550 steel plates, with their superior high strength and wear resistance, occupy a core position in fields with stringent requirements for material wear resistance, such as mining and heavy-duty loading and unloading machinery. They are a key basic material for ensuring the efficient and stable operation of equipment in these industries. However, a thorny problem has consistently plagued the industry during the production and processing of thin-gauge NM550 steel plates. After quenching, thin-gauge NM550 steel plates are prone to developing wavy defects on their edges. If these wavy defects are not addressed, they will seriously affect the accuracy of the steel plate in subsequent processing and assembly, and may even lead to equipment malfunctions. Therefore, straightening treatment is necessary to eliminate these defects.

[0003] However, new challenges arise. Thin-gauge NM550 steel plates are highly susceptible to cracking during straightening at room temperature, resulting in evenly spaced straightening cracks. This problem significantly restricts the quality and application of thin-gauge NM550 steel plates. In-depth research reveals that porosity, inclusions, and quenching internal stress are the main technical bottlenecks causing this cracking issue. The presence of porosity is a significant hidden danger leading to cracking. Porosity inside the steel plate acts like weak voids, disrupting the continuity and integrity of the material structure. During straightening, when the steel plate is subjected to external forces, stress concentration areas form around the pores, significantly reducing the material's load-bearing capacity in these areas. These areas are highly susceptible to fracture under stress, subsequently triggering crack propagation. Inclusions also severely affect the straightening performance of the steel plate. The properties of inclusions in the steel plate differ significantly from those of the matrix material. Under straightening stress, stress concentration easily occurs at the interface between the inclusions and the matrix. When stress reaches a certain level, the interface between inclusions and the matrix will separate, forming microcracks. These microcracks, as they propagate, will eventually lead to overall cracking of the steel plate. Quenching internal stress is another key factor causing straightening cracking. During the quenching process of thin-gauge NM550 steel plates, the rapid temperature change generates significant internal stress within the material. During room temperature straightening, the externally applied straightening force and the internal quenching stress of the steel plate are superimposed. When the superimposed stress exceeds the material's inherent strength limit, the steel plate will crack.

[0004] The straightening cracking problems caused by these technical pain points not only result in a large amount of scrap steel plates, increasing production costs and reducing production efficiency, but also pose significant hidden dangers for subsequent applications. If cracked steel plates are mistakenly used in mining, loading and unloading machinery, etc., they may suddenly break during equipment operation due to crack propagation, causing serious safety accidents, resulting in huge economic losses and casualties. Therefore, solving the straightening cracking problem of thin-gauge NM550 steel plates caused by porosity, inclusions, and quenching internal stress has become a key technical bottleneck that the industry urgently needs to overcome. Summary of the Invention

[0005] To solve the problem of cracking during straightening of wear-resistant steel plates caused by porosity, inclusions, and quenching internal stress.

[0006] A production method for suppressing cracking during straightening of thin-gauge NM550 wear-resistant steel plates includes the following steps:

[0007] S1: The molten steel that meets the chemical composition requirements is cast into a thick slab, then hydrogen is diffused in the heat preservation pit, and the furnace is heated before rolling. The furnace tapping temperature and heating time are set.

[0008] S2: In the roughing process, the initial rolling temperature, the final roughing rolling temperature, and the thickness of the intermediate billet to be heated are set.

[0009] S3: The intermediate billet in the waiting-to-heat state is cooled by an ACC cooling device, so that its surface temperature is rapidly cooled within 20-30 seconds, and then the temperature is uniformized.

[0010] S4: Set the finishing mill start temperature and finishing mill finish temperature, and then quickly put them into ACC controlled cooling;

[0011] S5: Set the red-heating temperature. In the heat treatment process, set the quenching temperature and tempering temperature.

[0012] Preferably, the thickness of the slab cast in S1 is 150-220 mm.

[0013] Preferably, the temperature for hydrogen diffusion in the insulation pit in S1 is 650±20℃, and the duration is 48h.

[0014] Preferably, the tapping temperature of the heating furnace in S1 is 1150-1230℃, and the heating time is 10-13 min / cm × slab thickness cm.

[0015] Preferably, the initial rolling temperature in S2 is 1100-1150℃, and the final rolling temperature of the roughing rolling is set to ≥1040℃.

[0016] Preferably, the thickness of the S2 intermediate billet before heating is 2.0-4.0 times the thickness of the finished product.

[0017] Preferably, in step S3, the temperature is rapidly cooled to 860-880°C within 20-30 seconds.

[0018] Preferably, in step S4, the initial rolling temperature is set to ≤880℃ and the finishing rolling temperature is set to ≤830℃.

[0019] Preferably, in step S4, the ACC cooling system is rapidly activated, with a cooling rate of 8-15℃ / s.

[0020] Preferably, the red-heating temperature in S5 is set to 450-600℃, and the temperature is adjusted in real time according to the quenching temperature. The quenching temperature range is 850-950℃, and the tempering temperature is 150-250℃.

[0021] The effects and advantages of the production method for suppressing cracking during straightening of thin-gauge NM550 wear-resistant steel plates according to the present invention:

[0022] 1. This patent suppresses bainite phase transformation by rapidly cooling intermediate billets, providing a uniform austenite matrix for subsequent low-temperature finishing rolling.

[0023] 2. According to this patent, the residual stress of the steel plate after straightening is ≤180MPa.

[0024] 3. In this patent, the ACC device includes upper and lower manifolds with a nozzle spacing of 100-150mm and a pressure of 0.8-1.2MPa. The cooling of the ACC is controlled in stages, with the front end being a high-pressure zone and the rear end being a low-pressure zone.

[0025] 4. This patent allows the hydrogen content to reach ≤2ppm after hydrogen expansion.

[0026] 5. The wear-resistant steel plate used in this patent has the following chemical composition: C: 0.33-0.36%, Si: 0.10-0.55%, Mn: 0.6-1.6%, Als: 0.020-0.060%, Nb+V+Ti: 0.020-0.030%, Cr+Ni+Mo: 0.4-1.00%, with the balance being Fe and trace impurities. Attached Figure Description

[0027] Figure 1 This is a flowchart of a production method for suppressing cracking during straightening of thin-gauge NM550 wear-resistant steel plates according to the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0030] Example 1

[0031] This embodiment provides a production method for suppressing cracking during straightening of thin-gauge NM550 wear-resistant steel plates, applicable to suppressing cracking during straightening of wear-resistant steel plates, including the following implementation details:

[0032] Experimental objective:

[0033] The aim is to suppress straightening cracks in thin-gauge NM550 wear-resistant steel plates.

[0034] Experimental materials:

[0035] Ultra-high strength ship plate steel (by weight): C: 0.34%, Si: 0.31%, Mn: 0.78%, P: 0.006%, S: 0.0007%, Als: 0.035%, Cr+Ni+Mo: 0.82%, Nb+V+Ti: 0.022%, with the remainder being Fe and unavoidable impurities.

[0036] Experimental steps:

[0037] S1: The molten steel that meets the chemical composition requirements is cast into a 150mm thick slab and hydrogen-expanded in a 650℃ heat preservation pit for 50 hours. Before rolling, it is heated in the furnace. The steel tapping temperature of the heating furnace is 1180℃ and the heating time is 180 minutes.

[0038] S2: In the roughing process, the initial rolling temperature is 1120℃, the final roughing rolling temperature is 1050℃, and the thickness of the intermediate billet waiting to be heated is 30mm.

[0039] S3: The intermediate billet in the waiting-to-warm state is cooled by an ACC cooling device, so that its surface temperature is rapidly cooled to 868℃ within 28s, and then left to warm up to make its temperature uniform.

[0040] S4: Finishing rolling start temperature 870℃, finishing rolling finish temperature 825℃, then it is quickly put into ACC controlled cooling with a cooling rate of 12℃ / s.

[0041] S5: Set the reddening temperature to 500℃, and set the quenching temperature to 910℃ and the tempering temperature to 220℃ in the heat treatment process.

[0042] Experimental results: See Table 1 for details.

[0043] Table 1: Test Results of Example 1

[0044] Mechanical properties <![CDATA[R m ]]> Lateral elongation Charpy shock absorption energy at -20℃ (transverse and longitudinal values) cold bending properties Example 1 <![CDATA[R P0.2 >1450MPa]]> <![CDATA[R m >1800MPa]]> A＞14% ＞27J good

[0045] The product produced in Example 1 has good overall performance: mechanical property R p0.2 >1450MPa, R m With a strength >1800MPa, transverse elongation A >14%, and Charpy impact absorption energy >27J in both the transverse and longitudinal directions at -20℃, the material exhibits good cold bending performance. Example 1 investigated the microstructure and alloy element distribution of straightened cracked NM550 thin plate samples and healthy NM550 samples without cracking. The fracture surface was analyzed in conjunction with crack propagation in the fractured samples. The results showed that porosity, inclusions, and quenching internal stress were the main causes of straightening cracking. Through optimization of the billet hydrogen diffusion, rolling, and heat treatment processes, qualified NM550 wear-resistant steel plates were successfully produced.

[0046] Example 2

[0047] This embodiment provides a production method for straightening and cracking thin-gauge NM550 wear-resistant steel plates by transferring steel plates with different element contents, including the following implementation details:

[0048] Experimental objective:

[0049] A production method is provided to suppress straightening cracking of thin-gauge NM550 wear-resistant steel plates with different element contents.

[0050] Experimental materials:

[0051] Ultra-high strength ship plate steel (by weight): C: 0.36%, Si: 0.55%, Mn: 1.6%, Als: 0.060%, Nb+V+Ti: 0.030%, Cr+Ni+Mo: 1.00%, with the balance being Fe and trace impurities.

[0052] Experimental steps:

[0053] S1: The molten steel that meets the chemical composition requirements is cast into a 150mm thick slab and hydrogen-expanded in a 650℃ heat preservation pit for 50 hours. Before rolling, it is heated in the furnace. The steel tapping temperature of the heating furnace is 1180℃ and the heating time is 180 minutes.

[0054] S2: In the roughing process, the initial rolling temperature is 1120℃, the final roughing rolling temperature is 1050℃, and the thickness of the intermediate billet waiting to be heated is 30mm.

[0055] S3: The intermediate billet in the waiting-to-warm state is cooled by an ACC cooling device, so that its surface temperature is rapidly cooled to 868℃ within 28s, and then left to warm up to make its temperature uniform.

[0056] S4: Finishing rolling start temperature 870℃, finishing rolling finish temperature 825℃, then it is quickly put into ACC controlled cooling with a cooling rate of 12℃ / s.

[0057] S5: Set the reddening temperature to 500℃, and set the quenching temperature to 910℃ and the tempering temperature to 220℃ in the heat treatment process.

[0058] Experimental results: See Table 2 for details.

[0059] Table 2: Test Results of Example 2

[0060] Mechanical properties <![CDATA[R m ]]> Lateral elongation Charpy shock absorption energy at -20℃ (transverse and longitudinal values) cold bending properties Example 2 <![CDATA[R P0.2 >1400MPa]]> <![CDATA[R m >1600MPa]]> A＞8% ＞25J 180° cold bending without cracks

[0061] The product produced in Example 2 has good overall performance: mechanical property R P0.2 >1400MPa, R m With a strength >1600MPa, transverse elongation A >8%, and Charpy impact absorption energy >25J in both the transverse and longitudinal directions at -20℃, the steel exhibits good cold bending performance. Example 2 investigated the microstructure and alloy element distribution of straightened cracked samples and uncracked healthy samples in thin-gauge NM550 wear-resistant steel plates with different elemental contents. The fracture surface was analyzed in conjunction with crack propagation in the fractured samples. The results showed that porosity, inclusions, and quenching internal stress are still the main causes of straightening cracking in this type of steel plate. Through optimization of the billet hydrogen diffusion process and the rolling and heat treatment processes, qualified NM550 wear-resistant steel plates were successfully produced.

[0062] Example 3

[0063] A different production method is provided for straightening and cracking thin-gauge NM550 wear-resistant steel plates transferred from steel plates with the same element content, including the following implementation details:

[0064] Experimental materials:

[0065] Ultra-high strength ship plate steel (by weight): C: 0.36%, Si: 0.55%, Mn: 1.6%, Als: 0.060%, Nb+V+Ti: 0.030%, Cr+Ni+Mo: 1.00%, with the balance being Fe and trace impurities.

[0066] Experimental objective:

[0067] A solution is provided for suppressing straightening cracking in thin-gauge NM550 wear-resistant steel plates with the same element content by adjusting the production method.

[0068] Experimental steps:

[0069] S1: The molten steel that meets the chemical composition requirements is cast into a 220mm thick slab and hydrogen-expanded in a 670℃ heat preservation pit for 50 hours. Before rolling, it is heated in the furnace. The steel tapping temperature of the heating furnace is 1230℃ and the heating time is 180 minutes.

[0070] S2: In the roughing process, the initial rolling temperature is 1150℃, the final roughing rolling temperature is 1060℃, and the thickness of the intermediate billet waiting to be heated is 30mm.

[0071] S3: The intermediate billet in the waiting-to-warm state is cooled by an ACC cooling device, so that its surface temperature is rapidly cooled to 880°C within 30 seconds, and then allowed to warm up to make its temperature uniform.

[0072] S4: The initial rolling temperature of the finishing mill is 880℃, the final rolling temperature of the finishing mill is 830℃, and then it is quickly put into ACC controlled cooling with a cooling rate of 15℃ / s.

[0073] S5: Set the reddening temperature to 600℃, and set the quenching temperature to 950℃ and the tempering temperature to 250℃ in the heat treatment process.

[0074] Experimental results: See Table 3 for details.

[0075] Table 3: Test Results of Example 3

[0076] Mechanical properties <![CDATA[R m ]]> Lateral elongation Charpy shock absorption energy at -20℃ (transverse and longitudinal values) cold bending properties Example 3 <![CDATA[R P0.2 >1400MPa]]> <![CDATA[R m >1590MPa]]> A＞9% ＞26J 180° cold bending without cracks

[0077] Example 3 focuses on thin-gauge NM550 wear-resistant steel plates with the same elemental content as in Example 2, adjusting production process parameters to suppress straightening cracking. The experiment used a 220mm thick slab, which was hydrogen-expanded in a 670℃ incubator for 50 hours, then heated to 1230℃ and held for 180 minutes. Rough rolling was performed at 1150℃ and final rolling at 1060℃, with an intermediate slab thickness of 30mm awaiting heating. The intermediate slab was cooled to 880℃ and homogenized within 30 seconds using an ACC cooling device. Finish rolling was performed at 880℃ and final rolling at 830℃, followed by ACC controlled cooling at a rate of 15℃ / s. The red-heating temperature was set at 600℃, quenching at 950℃, and tempering at 250℃. The results showed that the product's mechanical properties reached R... P0. 2 > 1400 MPa, R mWith an energy density >1590MPa, transverse elongation >9%, Charpy impact absorption energy >26J at -20℃, and no cracks after 180° cold bending, this method effectively suppresses straightening cracking of thin-gauge NM550 wear-resistant steel plates by optimizing process parameters such as slab thickness, heating temperature, and cooling rate under the same element content, thus achieving the production of qualified products.

[0078] Comparative Example 1

[0079] A production method for straightening and cracking conventional NM550 wear-resistant steel plates is provided, including the following implementation details:

[0080] Experimental materials:

[0081] Steel plate (C: 0.2%, Mn: 1.0%, Cr: 1.0%, Mo: 0.2%, S: 0.01%, P: 0.02%, the remainder is Fe)

[0082] Experimental objective:

[0083] Preparation method for straightening and cracking of traditional NM550 wear-resistant steel plates.

[0084] Experimental steps:

[0085] S1: LF furnace refining + RH vacuum degassing is adopted to ensure H≤2ppm and total inclusions≤20ppm. Low superheat casting is then used, combined with electromagnetic stirring in the crystallizer and electromagnetic stirring at the end of solidification. The billet is slowly cooled.

[0086] S2: Heat the billet to 1150-1200℃ and hold for 2-3 hours to ensure complete dissolution of carbides. Use two-stage rolling: rough rolling temperature 950-1050℃, single pass reduction 15-20% to break austenite grains, followed by finish rolling temperature 850-900℃, and final rolling thickness controlled at finished product thickness + 3-5mm.

[0087] S3: The finished product is cooled after rolling, and segmented controlled cooling is adopted. The cooling rate is 5-10℃ / s. After the temperature drops to 600-650℃, the cooling rate is controlled to be reduced to 2-3℃ / s. The product is then slowly cooled to below 300℃ to reduce thermal stress.

[0088] S4: Control the heating temperature at 880-920℃ and hold it for 1.5-2 minutes. Then, use water quenching + air cooling in stages to control the cooling. Set the initial cooling rate to ≥30℃ / s. When the temperature drops to 200-250℃, stop water cooling and switch to air cooling.

[0089] S5: Control the tempering temperature at 200-250℃, hold for 2-3 minutes to ensure that more than 50% of the quenching stress is eliminated, and after tempering, slowly cool with the furnace to below 100℃ before taking it out of the furnace.

[0090] S6: Straighten within 4 hours after tempering, then use low temperature straightening. Heat the steel plate to 150-200℃ and use a 20-roll precision straightener. Use a small reduction and multiple passes mode. The initial reduction is ≤0.5mm, and the reduction decreases in each subsequent pass. Finally, perform low temperature stress relief treatment immediately after straightening.

[0091] Experimental results: See Table 4 for details.

[0092] Table 4: Test Results of Comparative Example 1

[0093] Mechanical properties <![CDATA[R m ]]> Lateral elongation Charpy shock absorption energy at -20℃ (transverse and longitudinal values) cold bending properties Comparative Example 1 <![CDATA[R P0.2 >1350MPa]]> <![CDATA[R m >1550MPa]]> A＞5.5% ＞23J 180° cold bending micro-cracks

[0094] This article focuses on the straightening cracking problem of thin-gauge NM550 wear-resistant steel plates caused by porosity, inclusions, and quenching internal stress. It proposes a production method that includes optimization of hydrogen diffusion, rolling, and heat treatment processes: after casting molten steel of specific composition into thick slabs, hydrogen diffusion is carried out in a heat preservation pit, and the temperature and thickness parameters of heating, rough rolling, and finish rolling are precisely controlled. Combined with the ACC cooling device for segmented controlled cooling, the quenching and tempering temperatures are optimized.

[0095] Example 1 addresses the straightening cracking problem of thin-gauge NM550 wear-resistant steel plates. A 150mm thick slab was cast from molten steel with a specific composition, subjected to hydrogen diffusion in a 650℃ incubator for 50 hours, and heated to 1180℃ for 180 minutes. Rough rolling was performed at 1120℃, and final rolling at 1050℃. Combined with ACC cooling, finish rolling, 910℃ quenching, and 220℃ tempering, a steel plate with excellent comprehensive performance was successfully produced. P0.2 >1450MPa, R m >1800MPa, transverse elongation >14%, impact energy at -20℃ >27J, good cold bending properties, effectively solving the straightening cracking problem caused by porosity, inclusions and quenching internal stress.

[0096] Example 2 uses steel with different elemental contents and adopts the core process concept of Example 1. Its 150mm slab is hydrogen-expanded at 650℃ for 50 hours. The heating, rough rolling, finish rolling, and cooling parameters are the same as in Example 1, with quenching at 910℃ and tempering at 220℃. The final product's mechanical properties reach R... P0.2 >1400MPa, R m With a strength of >1600MPa, transverse elongation >8%, impact energy at -20℃ >25J, and no cracks after 180° cold bending, the straightening cracking problem of steel plates with different compositions was also solved through process optimization, and the performance meets the requirements.

[0097] Example 3, for steel plates with the same elemental content as Example 2, adjusted the process parameters. A 220mm slab underwent hydrogen diffusion at 670℃ for 50 hours, was tapped at 1230℃, roughed at 1150℃, finished at 1060℃, and cooled to 880℃ within 30 seconds using ACC. The finishing rolling temperature was set at 880℃, the finishing temperature at 830℃, the quenching temperature at 950℃, and the tempering temperature at 250℃. The product performance was R. P0.2 >1400MPa, R m With a strength of >1590MPa, transverse elongation >9%, impact energy at -20℃ >26J, and no cracks after 180° cold bending, qualified steel plates were produced by adjusting process parameters, and straightening cracking was suppressed.

[0098] Comparative Example 1 uses a traditional process to produce NM550 wear-resistant steel plates. The raw material composition is C: 0.2%, Mn: 1.0%, etc. The process involves LF furnace refining and RH vacuum degassing, slow cooling of the cast billet, heating to 1150-1200℃, two-stage rolling, segmented controlled cooling followed by water quenching and air cooling, tempering at 200-250℃, and low-temperature stress relief after straightening. The final product's mechanical properties are R... P0.2 >1350MPa, R m With an impact strength of >1550MPa, a transverse elongation of only >5.5%, an impact energy of >23J at -20℃, and the appearance of micro-cracks during 180° cold bending, the problem of cracking during straightening has not been completely solved, resulting in weak overall performance.

[0099] Comparing Examples 1-3 with Comparative Example 1, it is evident that Example 1 exhibits a particularly significant advantage: its mechanical properties are all superior to those of Examples 2, 3, and Comparative Example 1, especially R. m With a strength >1800MPa and a transverse elongation >14%, far exceeding other methods, its cold bending performance is excellent, with no cracks, thus solving the problem of straightening cracking. In contrast, Comparative Example 1 exhibits micro-cracks during cold bending. Although Examples 2 and 3 meet the performance standards, their overall performance is weaker than Example 1. Therefore, the production method of Example 1 is significantly superior to other methods in suppressing straightening cracking of thin-gauge NM550 wear-resistant steel plates and improving overall performance.

[0100] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0101] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0102] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0103] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included in the protection of the present invention.

Claims

1. A production method for suppressing cracking during straightening of thin-gauge NM550 wear-resistant steel plates, characterized in that, Includes the following steps: S1: The molten steel that meets the chemical composition requirements is cast into a thick slab, then hydrogen is diffused in the heat preservation pit, and the furnace is heated before rolling. The furnace tapping temperature and heating time are set. S2: In the roughing process, the initial rolling temperature, the final roughing rolling temperature, and the thickness of the intermediate billet to be heated are set. S3: The intermediate billet in the waiting-to-heat state is cooled by an ACC cooling device, so that its surface temperature is rapidly cooled within 20-30 seconds, and then the temperature is uniformized. S4: Set the finishing mill start temperature and finishing mill finish temperature, and then quickly put them into ACC controlled cooling; S5: Set the red-heating temperature. In the heat treatment process, set the quenching temperature and tempering temperature.

2. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, The thickness of the slab cast in S1 is 150-220 mm.

3. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, The temperature for hydrogen diffusion in the insulation pit in S1 is 650±20℃, and the duration is 48h.

4. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, The tapping temperature of the heating furnace in S1 is 1150-1230℃, and the heating time lasts for 10-13 min / cm × slab thickness cm.

5. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, The initial rolling temperature in S2 is 1100-1150℃, and the final rolling temperature of the roughing rolling is set to ≥1040℃.

6. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, The thickness of the S2 intermediate billet to be heated is 2.0-4.0 times the thickness of the finished product.

7. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, In step S3, the temperature is rapidly cooled to 860-880°C within 20-30 seconds.

8. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, The initial rolling temperature of S4 is set to ≤880℃, and the finishing rolling temperature is set to ≤830℃.

9. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, The S4 section rapidly enters ACC controlled cooling, with a cooling rate of 8-15℃ / s.

10. The production method for suppressing straightening cracks in thin-gauge NM550 wear-resistant steel plates as described in claim 1, characterized in that, The red-heating temperature in S5 is set to 450-600℃, and the temperature is adjusted in real time according to the quenching temperature. The quenching temperature range is 850-950℃, and the tempering temperature is 150-250℃.

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