27mntyb high-strength wear-resistant steel plate and production method thereof

Abstract

The application discloses a 27MnTiB high-strength wear-resistant steel plate and a production method thereof. By adopting a reasonable controlled rolling and controlled cooling process, cooperating with on-line quenching, stacking slow cooling and rapid low-temperature tempering, the 27MnTiB steel plate can not only obtain relatively high hardness and strength, but also obtain relatively high impact toughness, directly meeting the requirements of high-strength wear-resistant steel, with the yield strength being greater than or equal to 1500MPa, the tensile strength being greater than or equal to 1650MPa, the elongation being greater than or equal to 9%, the impact energy being greater than or equal to 60J, and the hardness being greater than or equal to 450HB. Meanwhile, the processing and manufacturing process is simplified, and the processing cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of steel plate production, and more specifically, to 27MnTiB high-strength wear-resistant steel plate and its production method. Background Technology

[0002] Wear is one of the main forms of workpiece failure, and a major cause of the massive consumption of energy and raw materials. According to incomplete statistics, one-third to one-half of energy consumption is due to friction and wear, and the economic losses caused by the wear of machinery and its parts account for approximately 6% of the gross national product. Wear-resistant steel plates are widely used in various fields such as coal, metallurgy, mining, building materials, power, railways, and the military. Examples include excavator buckets, mill liners, crusher jaw plates, carriage plates, track plates, silo plates, and railway turnouts.

[0003] Currently, 27MnTiB wear-resistant steel is considered a relatively high-grade wear-resistant steel, but its tensile strength ≥980MPa, yield strength ≥835MPa, impact energy ≥39J, and hardness HB≥270 are only suitable as the base material for wear-resistant steel. To use it as wear-resistant steel, a layer of more wear-resistant high-alloy material needs to be deposited on the surface; this is time-consuming, labor-intensive, and costly.

[0004] Therefore, this invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a 27MnTiB high-strength wear-resistant steel plate and its production method, thereby improving the strength and hardness of 27MnTiB wear-resistant steel.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a 27MnTiB high-strength wear-resistant steel plate, comprising the following chemical composition by mass percentage: C 0.26-0.31%, Si 0.15-0.36%, Mn 1.10-1.45%, P≤0.02%, S≤0.01%, Ti 0.018-0.05%, Cr 0.3-0.6%, Als 0.015-0.045%, Cu≤0.3%, B 0.0005-0.0035%, and N≤80ppm, with the remainder being Fe and residual elements, and a carbon equivalent Ceq≤0.66%.

[0008] In an optional implementation, the delivery condition is that the steel plate is subjected to online quenching and low-temperature tempering treatment.

[0009] In an optional embodiment, the thickness of the steel plate is 20-80mm, the metallographic structure is low-temperature tempered martensite, the yield strength is ≥1500MPa, the tensile strength is ≥1650MPa, the elongation is ≥9%, the impact energy is ≥60J, and the hardness HB is ≥450.

[0010] Secondly, the present invention provides a method for producing the 27MnTiB high-strength wear-resistant steel plate described in the foregoing embodiments, comprising the following steps:

[0011] Rolling: The initial rolling temperature of the roughing stage is ≥1000℃, and the single-pass reduction of no less than 35mm is not less than 3 passes. The thickness of the billet after roughing is 1.5-2 times the thickness of the target steel plate. The finishing temperature of roughing is 930-950℃. The billet after roughing is cooled and reheated to obtain a billet with a surface temperature of 860-880℃, which then enters the finishing rolling stage. The reduction rate of the finishing rolling stage is ≥15%. The final rolling temperature is 830-860℃.

[0012] Online quenching; the rolled steel plate is placed in water to cool to 300-400℃, wherein the water immersion temperature of the steel plate is ≥800℃;

[0013] Stacking and slow cooling, stacking temperature ≥250℃, slow cooling time ≥24h;

[0014] Low-temperature tempering: temperature is 300-350℃, holding time is 2-3 min / mm.

[0015] In an optional implementation, the rolling step employs a controlled rolling and cooling process using HY-TMCP equipment, where "HY-TMCP" represents the Hanye controlled rolling and cooling process.

[0016] In an optional implementation, the steel billet after rough rolling undergoes intermediate cooling, with at least three sets of cooling water manifolds, a roll speed of 0.5-4.0 m / s, and a single set of water volume > 100 m³ / s. 3 / h, specific water volume >2.0, water temperature controlled within 30℃, billet inlet temperature ≥920℃, billet surface temperature after cooling above 800℃, after 2-3s of temperature uniformization, the steel plate temperature recovers to 860-880℃, and enters the finishing rolling stage.

[0017] In an optional embodiment, the reduction amount is gradually reduced in the last four passes of finishing rolling; preferably, the reduction amount in the last four passes of finishing rolling is gradually reduced from 4-0.5 mm; more preferably, the reduction amounts in the last four passes of finishing rolling are 4 mm, 3 mm, 2 mm and 1 mm, respectively.

[0018] In optional embodiments, the billet is subjected to rapid heat straightening after rolling; and / or, rapid heat leveling is performed after online quenching.

[0019] In an optional embodiment, the rolling step may further include sequential KR desulfurization, converter smelting, LF refining, VD vacuum refining, continuous casting, billet cleaning and heating.

[0020] In an optional implementation, at least one of the following is further included before the rolling step:

[0021] ①In the KR desulfurization process, the sulfur content of the molten iron after KR treatment is below 0.01wt%;

[0022] ② In the converter smelting process, a top-and-bottom combined blowing converter is used for smelting. The tapping temperature is controlled at 1580-1600℃, and the tapping C is ≤0.26wt%, P and S are controlled within 0.02wt%. Argon is blown throughout the tapping process, and 150-200Kg of lime is added to form slag.

[0023] ③ In the LF refining step, when the ladle is placed in the LF position, the Al line is fed in, and a large amount of slag is used to control the slag formation. The white slag is kept for no less than 25 minutes.

[0024] Preferably, after the LF refining is completed, calcium wire is fed until the Ca / S ratio is between 0.3 and 0.6, the feeding speed of the calcium wire is 3.5-4 m / s, and at the same time, inert gas is blown in from the bottom of the ladle for stirring;

[0025] ④ In the VD vacuum refining step, the vacuum degree is ≤67Pa, the holding time is 12-15min, and the H content is ≤1.0ppm;

[0026] ⑤ In the continuous casting process, the superheat is 10-20℃, and the billet is cooled for 12-24 hours after casting.

[0027] ⑥ In the billet cleaning step, heated cleaning is adopted at a temperature of 80-400℃, with a cleaning depth-to-width ratio of 1:3. After the cleaning is qualified, the billet is loaded into the furnace for heating.

[0028] ⑦ The heating process includes a first-stage heating, a second-stage heating, and a uniform heating. The heating temperature of the first-stage heating is ≤950℃, the heating temperature of the second-stage heating is 1220-1240℃, and the heating time is 10±2cm / min. The temperature of the uniform heating section is 1200-1220℃, and the holding time is >30min.

[0029] The present invention has the following beneficial effects:

[0030] The 27MnTiB high-strength wear-resistant steel plate in this application does not contain precious alloys with Mo and Ni elements, but makes full use of C and Cr elements to improve hardenability, strength and hardness.

[0031] The production process of the 27MnTiB high-strength wear-resistant steel plate in this application adopts a reasonable controlled rolling and cooling process, combined with online quenching, slow stacking cooling and rapid low-temperature tempering, so that the steel plate is delivered in the form of online quenching + low-temperature tempering treatment. This not only gives the 27MnTiB steel relatively high hardness and strength, but also relatively high impact toughness, directly meeting the requirements of high-strength wear-resistant steel, with a yield strength ≥1500MPa, tensile strength ≥1650MPa, elongation ≥9%, impact energy ≥60J, and hardness ≥450HB. At the same time, it simplifies the processing and manufacturing process and reduces processing costs. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The microstructure of tempered martensite obtained in Example 1. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0035] This application provides a 27MnTiB high-strength wear-resistant steel plate, comprising the following chemical composition by mass percentage (wt%): C 0.26-0.31%, Si 0.15-0.36%, Mn 1.10-1.45%, P≤0.02%, S≤0.01%, Ti0.018-0.05%, Cr 0.3-0.6%, Als 0.015-0.045%, Cu≤0.3%, B0.0005-0.0035%, and N≤80ppm, with the remainder being Fe and residual elements, and a carbon equivalent Ceq≤0.66%. The steel plate is delivered in a quenched and tempered condition (online quenching + tempering).

[0036] The 27MnTiB high-strength wear-resistant steel plate in this application does not contain precious alloys with Mo or Ni elements, but makes full use of C, Cr, and B elements to improve hardenability, strength, and hardness. Finally, tempered martensite is obtained through online quenching and tempering, ensuring the steel plate's excellent mechanical properties and good wear resistance.

[0037] In this application, the 27MnTiB high-strength wear-resistant steel plate is produced using a process involving converter smelting, LF (Fluid Fluid Refining), VD (Vacuum Distillation), continuous casting, heating furnace, heavy plate mill rolling, SUPIC ultra-dense cooling system online quenching, and low-temperature tempering. The process flow is as follows: Hot metal KR desulfurization → converter smelting → LF refining → VD vacuum refining → continuous casting → billet cleaning → heating → rolling → pre-straightening → online quenching → leveling → stack cooling → low-temperature tempering → flaw detection → performance testing → finishing and warehousing. Specifically, this is achieved through the following steps:

[0038] Desulfurization of molten iron by KR: Slag removal treatment at the KR station, with a slag layer thickness of ≤25mm on the liquid surface, and the sulfur content of the molten iron after KR treatment is below 0.01%, with a temperature drop of ≤25℃ during the desulfurization process.

[0039] Converter smelting process: Use a normal steel ladle with the required age and condition, ensuring the ladle rim is clean; the molten iron entering the furnace must be desulfurized (and preferably selected from heats with low phosphorus and suitable temperature); the scrap steel added to the converter must be dry, high-quality offcuts to ensure that the tapped steel has a carbon content ≤ 0.26 wt% and phosphorus and sulfur content controlled below 0.02 wt%. Argon blowing is performed throughout the tapping process, and 150-200 kg of lime is added for slag formation.

[0040] LF refining: A large slag volume slag-making process is adopted, with 1000-1200 kg of lime added and the alkalinity controlled at 4.0-6.0. It is required that the slag must turn white after the first heating of refining. During the second heating, 10-30 kg of calcium carbide is added each time according to the submerged arc effect. At the same time, 1-3 shovels of aluminum particles are added to the ladle every 2 minutes to ensure that the white slag is maintained throughout the second heating process. During the third heating, the deoxidizer is added according to the slag color to maintain the white slag. The white slag holding time should be ≥25 min. The final slag after refining should be a foamy white slag with good fluidity and suitable viscosity. The number of fine-tuning adjustments to the Al content in the LF refining process should be controlled within 2 times. Sampling and composition analysis can only be performed when the temperature reaches above 1600℃. The plan can only be implemented if the composition meets the requirements (P content ≤0.008%, C content ≤0.25%). Alloys should be prepared in advance. After confirming that the plan can be implemented, the composition should be quickly adjusted and the temperature increased to avoid excessive heating time and excessive C content. The Si content of the molten steel is controlled by using high-basicity refining slag and lime. The deoxidizer is mainly calcium carbide and aluminum granules to ensure that the refining slag system is a calcium aluminate slag system. The slag must have SiO2 ≤8wt% and basicity ≥8. After refining, an appropriate amount of pure calcium wire is added according to the S content. During the wire feeding process, inert gas (argon) is blown in from the bottom of the ladle for stirring. The feeding speed of Ca wire is 3.5-4 m / s to ensure that the Ca / S ratio is between 0.3 and 0.6, so as to modify MnS and avoid the formation of long strips of MnS inclusions after rolling. After feeding Ca wire, no further heating or temperature adjustment or addition of other alloys is allowed. Stir slowly for three minutes and then enter the VD vacuum refining stage.

[0041] VD vacuum refining: VD holding time is controlled at 12-15 min, vacuum degree is 66.7 Pa, the molten steel tumbling effect is good during the holding process, and the H content is required to be ≤1.0 ppm; after breaking the vacuum, add rice husks for soft blowing for 5-8 min in time, and the molten steel must not be exposed during the soft blowing process;

[0042] Continuous casting: Before casting, check the equipment to ensure that the continuous casting machine is in good condition. Protective casting is used throughout the continuous casting process. The superheat is set at 10-20℃. Light pressure and electromagnetic stirring are used during the casting process. The casting speed is reduced by one level compared to the normal casting speed. The secondary cooling water adopts a weak cooling mode. The billet is stacked and cooled for 12-24 hours after casting.

[0043] Billet cleaning: Heated cleaning is adopted, with the temperature controlled between 80-400℃, usually between 80-200℃. The reason is that cleaning is usually done manually with flame, and the temperature is too high for the on-site operators. Cracks in the billet are difficult to see at high temperatures. When cleaning surface cracks that may have already appeared, the depth-to-width ratio of the area cleaned is 1:3. This can prevent the recurrence of cracks after cleaning. After the cleaning is qualified, the billet is loaded into the furnace while still warm.

[0044] Heating: A heating furnace is used for heating at a rate of 10±2 cm / min. A staged heating-holding process is employed to prevent the billet from cracking due to excessively rapid heating. The first heating temperature is ≤950℃, the second heating temperature is 1220-1240℃, the soaking temperature is 1200-1220℃, and the holding time is >30min. Controlling the heating temperature and time ensures the billet is thoroughly heated.

[0045] Rolling: The HY-TMCP process is used for rolling. In the roughing stage, the initial rolling temperature is ≥1000℃, employing a high-temperature, low-speed, high-reduction process. The single-pass reduction in at least three rolling mills is controlled to be above 35mm. The roughing end temperature is 930-950℃. The billet rapidly enters the intermediate cooling (IC) stage, with at least three sets of cooling water manifolds. The roll speed is 0.5-4.0m / s, and the water flow rate per set is >100m³. 3 The water flow rate is ≥2.0, the water temperature is controlled below 30℃, the inlet water temperature is ≥920℃, and the surface temperature of the steel plate after cooling is above 800℃. After 2-3 seconds of temperature uniformization, it quickly enters the finishing rolling stage. During the finishing rolling stage, attention should be paid to the control of plate shape and reduction amount, and the final rolling temperature is 830-860℃; small reduction amounts are used in the last four rolling passes to ensure plate shape.

[0046] After rolling, the steel plate undergoes a rapid cooling and leveling process to further ensure its straightness.

[0047] After leveling, the steel plate is directly subjected to online quenching. The water immersion temperature of the steel plate is ≥800℃, and the steel plate is cooled to 300-400℃ in the SUPICC ultra-density cooling device.

[0048] After online quenching, rapid temperature leveling is performed, with 1-3 passes. The purpose of rapid temperature leveling is to level the steel plate while it is still at a relatively high temperature, as its yield strength is slightly lower and it is easier to level. The higher the temperature, the easier it is to level. Waiting for the steel plate to cool completely before leveling makes the process much more difficult. If the plate is heated again after cooling for leveling, it will inevitably increase labor and energy costs, which is obviously uneconomical.

[0049] Stacking and slow cooling: After leveling, the steel plates are stacked and slow cooled for a period of not less than 24 hours, with a stacking temperature of ≥250℃. After stacking, hot steel plates are piled on the surface of the steel plates, with a height of more than 300mm, to promote the release of internal stress and hydrogen diffusion in the online quenched 27MnTiB steel plates.

[0050] Tempering: After the steel plates are unstacking, due to the different cooling intensities between the head and the body during online quenching, a series of tempering tests were conducted on samples from the head and body of the steel plates. The tempering temperature range was ultimately determined to be 300-350℃. After determining the tempering temperature range, the tempering holding time was then determined, ultimately achieving a relatively high tempering temperature with a holding coefficient of 2-3 min / mm, and a holding time shorter than the commonly used 4 min / mm. The shorter holding coefficient is beneficial in two ways: firstly, it improves the production efficiency of the steel plates; secondly, it helps reduce the hardness difference across the entire cross-section, meaning the surface layer reaches the set temperature before the center, and the surface layer's holding time is longer than the core's. This longer holding time solves the problem of high surface tempering resistance caused by the fine grain size, large deformation, and high cooling rate during online quenching. After tempering, external inspection, flaw detection, finishing, sampling, and microstructure and property testing are performed before warehousing.

[0051] Specifically, the features and performance of the present invention will be further described in detail below with reference to embodiments.

[0052] Example

[0053] This embodiment provides a processing method for 27MnTiB high-strength wear-resistant steel, including:

[0054] Desulfurization of molten iron by KR: Slag removal treatment at the KR station. After KR treatment, the sulfur content of molten iron is below 0.01%, and the temperature drop during the desulfurization process is ≤25℃.

[0055] Converter smelting process: Top and bottom blowing converter is used for smelting. The tapping temperature is controlled at 1580-1600℃. The tapping C is ≤0.26wt%, and P and S are controlled within 0.02wt%. Argon is blown through the ladle throughout the tapping process, and 150-200Kg of lime is added to form slag.

[0056] LF refining: Add 1000-1200 kg of lime, control the alkalinity at 4.0-6.0. After the first heating of refining, the slag must turn white. During the second heating, add 10-30 kg of calcium carbide each time according to the submerged arc effect. At the same time, add 1-3 shovels of aluminum particles to the ladle every 2 minutes for deoxidation to ensure that the white slag is maintained throughout the second heating process. During the third heating, add an appropriate amount of deoxidizer to maintain the white slag. The white slag holding time should be ≥25 min. The final slag after refining should be a foamy white slag with good fluidity and suitable viscosity. The number of fine-tuning adjustments to the Al content in the LF refining process should be controlled within 2 times. Alloys should be prepared in advance, and samples should only be taken for composition analysis when the temperature reaches above 1600℃. When the composition meets the requirements (P content ≤0.008%, C content ≤0.25%), alloys should be added quickly, the composition adjusted, and the temperature increased to control the weight percentage of molten steel at C 0.26-0.31%, Si 0.15-0.36%, Mn 1.10-1.45%, P≤0.02%, S≤0.01%, Ti 0.018-0.05%, Cr 0.3-0.6%, and Al content ≤0.25%. 0.015-0.045%, Cu≤0.3%, B0.0005-0.0035%; After refining, an appropriate amount of pure calcium wire is fed in according to the S content. During the wire feeding process, inert gas (argon) is blown in from the bottom of the ladle for stirring. The feeding speed of Ca wire is 3.5-4 m / s to ensure that the Ca / S ratio is between 0.3-0.6, so as to modify MnS and avoid the formation of long strips of MnS inclusions after rolling. After feeding Ca wire, no further heating or temperature adjustment or addition of other alloys is allowed. Stir slowly for three minutes and then enter the VD vacuum refining stage.

[0057] Vacuum Deposition (VD) refining: The VD holding time is controlled at 12-15 min, the vacuum degree is 66.7 Pa, the molten steel tumbling effect is good during the holding process, and the H content is required to be ≤1.0 ppm; after breaking the vacuum, add rice husks for soft blowing for 5-8 min in time, and the molten steel must not be exposed during the soft blowing process; at the end of refining, the chemical composition of the molten steel meets the following requirements: C 0.26-0.31%, Si 0.15-0.36%, Mn 1.10-1.45%, P≤0.02%, S≤0.01%, Ti0.018-0.05%, Cr 0.3-0.6%, Als 0.015-0.045%, Cu≤0.3%, B0.0005-0.0035%, and N≤80 ppm.

[0058] Continuous casting: Before casting, carefully inspect the equipment to ensure the continuous casting machine is in good condition. Protective casting should be used throughout the process, with superheat maintained at 10-20℃. Light pressure and electromagnetic stirring should be used during casting. The casting speed should be reduced by one level from the normal speed. The secondary cooling water should be in a weak cooling mode. The billet should be cooled for 12-24 hours after casting. For steel plates with a thickness of 20-50mm, a 250mm section continuous casting machine is preferred; for steel plates with a thickness of 50-80mm, a 300mm section continuous casting machine is recommended.

[0059] Steel billet cleaning: heated cleaning is adopted, with the temperature controlled between 80-400℃, usually between 80-200℃. The depth-to-width ratio of the cleaning area is 1:3. After the cleaning is qualified, the billet is loaded into the furnace while still heated.

[0060] Heating: A heating furnace is used for heating at a rate of 10±2 cm / min. A staged heating-holding process is employed to prevent the billet from cracking due to excessively rapid heating. The first heating temperature is ≤950℃, the second heating temperature is 1220-1240℃, the soaking temperature is 1200-1220℃, and the holding time is >30min. Controlling the heating temperature and time ensures the billet is thoroughly heated.

[0061] Rolling:

[0062] Example 1 (20mm steel plate) rolling process: After heating the 250mm continuous casting billet, the initial rolling temperature is about 1000-1020℃. In the first three passes of rolling, the reduction should be increased as much as possible while ensuring the safety of the rolling mill. The reduction is designed according to 40mm-40mm-35mm. The final rolling temperature of roughing is between 940-950℃. The target thickness of the intermediate billet after rolling is 40mm, generally between 40-60mm. The intermediate billet is quickly sent to IC for cooling. The water temperature is ≥920℃. 3-4 sets of manifolds are opened for cooling. After cooling, the surface temperature is 800-820℃. After 2-3 seconds of uniform temperature return to red, the red temperature is 820-840℃. Then it enters the finishing rolling. The reduction of the last four passes of finishing rolling is controlled according to 4mm, 3mm, 2mm and 1mm. The final rolling temperature of finishing rolling is 830-840℃.

[0063] Example 2 (30mm steel plate) rolling process: After heating the 250mm continuous casting billet, the initial rolling temperature is about 1000-1020℃. The reduction in the first three passes is 40mm-40mm-35mm. The final rolling temperature is between 940-950℃. The target thickness of the intermediate billet after rolling is 60mm, generally between 60-65mm. The intermediate billet is quickly cooled in IC, with a water temperature ≥920℃. 4-6 sets of cooling manifolds are opened. After cooling, the surface temperature is 800-820℃. After 2-3 seconds of uniform temperature return to red, the red temperature is 820-840℃ before entering the finishing mill. The reduction in the last four passes of finishing mill is controlled at 4mm, 3mm, 2mm and 1mm. The final rolling temperature of finishing mill is 830-840℃.

[0064] Example 3 (60mm steel plate) rolling process: After heating the 300mm continuous casting billet, the initial rolling temperature is approximately 1010-1040℃. In the first three passes of rolling, the reduction should be maximized while ensuring the safety of the rolling mill. The reduction is designed according to 40mm-40mm-35mm. The final rolling temperature of roughing is between 940-950℃. The target thickness of the intermediate billet after rolling is 100mm, generally between 100-120mm. The intermediate billet is quickly sent to IC for cooling. The water temperature is ≥920℃. 4-6 sets of manifolds are opened for cooling. After cooling, the surface temperature is 800-820℃. After 2-3 seconds of uniform temperature return to red, the red temperature is 830-850℃ before entering the finishing mill. The reduction of the last four passes of finishing mill is controlled according to 4mm, 3mm, 2mm and 1mm. The final rolling temperature of finishing mill is 840-850℃.

[0065] Example 4 (80mm steel plate) rolling process: After heating the 250mm continuous casting billet, the initial rolling temperature is about 1000-1020℃. In the first three passes of rolling, the reduction should be increased as much as possible while ensuring the safety of the rolling mill. The reduction is designed according to 40mm-40mm-35mm. The final rolling temperature of roughing is between 940-950℃. The target thickness of the intermediate billet after rolling is 120mm, generally between 120-130mm. The intermediate billet is quickly sent to IC for cooling. The water temperature is ≥920℃. 5-7 sets of manifolds are opened for cooling. After cooling, the surface temperature is 800-820℃. After 2-3 seconds of uniform temperature return to red, the red temperature is 830-850℃ before entering the finishing mill. The reduction of the last four passes of finishing mill is controlled according to 4mm, 3mm, 2mm and 1mm. The final rolling temperature of finishing mill is 840-850℃.

[0066] After rolling, the steel plate undergoes a rapid cooling and leveling process to further ensure its straightness.

[0067] After leveling, perform online quenching directly:

[0068] Example 1 (20mm steel plate): The steel plate was immersed in water at a temperature of 800-810℃, the final cooling temperature was 300-320℃, and the maximum temperature for re-heating was 350℃.

[0069] Example 2 (30mm steel plate): The steel plate was immersed in water at a temperature of 800-810℃, the final cooling temperature was 310-330℃, and the maximum temperature for re-heating was 355℃.

[0070] Example 3 (60mm steel plate): The steel plate was immersed in water at a temperature of 800-810℃, the final cooling temperature was 300-320℃, and the maximum temperature for re-heating was 360℃.

[0071] Example 4 (80mm steel plate): The steel plate was immersed in water at a temperature of 800-810℃, the final cooling temperature was 300-310℃, and the maximum temperature for re-heating was 370℃.

[0072] After online quenching, the plate is leveled by rapid heating 1-3 times. After the plate is straight, it is stacked and cooled slowly.

[0073] Tempering of steel plates:

[0074] Example 1 (20mm steel plate): The tempering temperature of the steel plate is 390-400℃, and the tempering holding coefficient is 2.0min / mm.

[0075] Example 2 (30mm steel plate): The tempering temperature of the steel plate is 380-390℃, and the tempering holding coefficient is 2.2min / mm.

[0076] Example 3 (60mm steel plate): The tempering temperature of the steel plate is 370-380℃, and the tempering holding coefficient is 2.2min / mm.

[0077] Example 4 (80mm steel plate): The tempering temperature of the steel plate is 360-370℃, and the tempering holding coefficient is 2.2min / mm.

[0078] After tempering, the products undergo external inspection, flaw detection, finishing, sampling, and microstructure testing before being put into storage.

[0079] The composition and thickness of the 27MnTiB high-strength wear-resistant steel in each embodiment of this application are shown in Table 1, and the performance results are shown in Table 2.

[0080] Table 1. Composition (Wt%) of 20-80mm high-strength wear-resistant steel 27MnTiB

[0081]

[0082] Table 2. Quenching and tempering performance data of 10-80mm low-cost, high-strength wear-resistant steel 27MnTiB

[0083]

[0084] Inclusions were detected according to GB / T10561-2005 "Standard Rating Chart Microscopic Examination Method for Determination of Non-metallic Inclusion Content in Steel". The morphology, width and length of inclusions in the steel in Examples 1-4 were observed and recorded under a metallographic microscope. Then, they were rated according to the standard. The lower the inclusion level, the less inclusion content and the higher the purity of the molten steel. The specific rating results are shown in Table 3.

[0085] Table 3. Inclusion analysis of 27MnTiB after quenching and tempering

[0086]

[0087] This invention, through the above-described process flow and with reasonable chemical composition design and production process control, successfully developed a 20-80mm thick 27MnTiB high-strength wear-resistant steel plate. Its yield strength is controlled at 1528-1676MPa, tensile strength at 1693-1763MPa, elongation at 9%-11%, 20℃ U-shaped impact energy at 60-80J, surface hardness at 460-510HB, and core hardness at 438-469HB. Figure 1 SEM analysis revealed that the tempered martensite structure obtained in Example 1 was uniform, consisting mainly of fine tempered martensite, with a small amount of precipitates at the grain boundaries.

[0088] The steel plates developed in this embodiment of the invention underwent external inspection, and the pass rate was 100%. Flaw detection was performed according to JB / T 47030, and the pass rate for Grade I was 99%, while the pass rate for Grade III was 100%, achieving the expected results.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A 27MnTiB high-strength wear-resistant steel plate, characterized in that, The chemical composition includes the following percentages by mass: C 0.26-0.31%, Si 0.15-0.36%, Mn 1.10-1.45%, P≤0.02%, S≤0.01%, Ti 0.018-0.05%, Cr 0.3-0.6%, Als 0.015-0.045%, Cu≤0.3%, B 0.0005-0.0035%, and N≤80ppm, with the remainder being Fe and residual elements. The carbon equivalent Ceq≤0.66%, the metallographic structure is low-temperature tempered martensite, the yield strength ≥1500MPa, the tensile strength ≥1650MPa, the elongation ≥9%, the impact energy ≥60J, and the hardness HB≥450. The production method of the 27MnTiB high-strength wear-resistant steel plate includes the following steps: Rolling: The initial rolling temperature of the roughing stage is ≥1000℃, and the single-pass reduction of no less than 35mm is not less than 3 passes. The thickness of the billet after roughing is 1.5-2 times the thickness of the target steel plate. The finishing temperature of roughing is 930-950℃. The billet after roughing is cooled and reheated to obtain a billet with a surface temperature of 860-880℃ and then enters the finishing rolling stage. The reduction rate of the finishing rolling stage is ≥15%. The final rolling temperature is 830-860℃. Online quenching; the rolled steel plate is placed in water to cool to 300-400℃, wherein the water immersion temperature of the steel plate is ≥800℃; Stacking and slow cooling, stacking temperature ≥250℃, slow cooling time ≥24h; Low-temperature tempering, at a temperature of 300-350℃, with a holding time of 2-3 min / mm; The process involves intermediate cooling of the billet after rough rolling, with at least three sets of cooling water manifolds, a roll speed of 0.5-4.0 m / s, a single set of water volume > 100 m³ / h, a specific water volume > 2.0, and a water temperature controlled below 30℃. The billet's initial water temperature is ≥ 920℃, and the surface temperature of the billet after cooling is above 800℃. After 2-3 seconds of temperature equalization, the steel plate temperature recovers to 860-880℃, and the billet enters the finishing rolling stage. The reduction in the last four passes of finishing rolling gradually decreases from 4-0.5 mm.

2. The 27MnTiB high-strength wear-resistant steel plate according to claim 1, characterized in that, The delivery condition is that the steel plate has undergone online quenching and low-temperature tempering treatment.

3. The 27MnTiB high-strength wear-resistant steel plate according to claim 1, characterized in that, The rolling step employs a controlled rolling and cooling process using HY-TMCP equipment, where "HY-TMCP" represents the Hanye controlled rolling and cooling process.

4. The method for producing 27MnTiB high-strength wear-resistant steel plate according to claim 1, characterized in that, The reduction amounts for the last four passes of finishing rolling are 4mm, 3mm, 2mm and 1mm, respectively.

5. The method for producing 27MnTiB high-strength wear-resistant steel plate according to claim 1, characterized in that, After rolling, the steel billet is subjected to rapid heating and straightening; and / or, after online quenching, it is subjected to rapid heating and leveling.

6. The method for producing 27MnTiB high-strength wear-resistant steel plate according to claim 1, characterized in that, The rolling step is preceded by KR desulfurization, converter smelting, LF refining, VD vacuum refining, continuous casting, billet cleaning and heating.

7. The method for producing 27MnTiB high-strength wear-resistant steel plate according to claim 6, characterized in that, The rolling step is preceded by at least one of the following: ①In the KR desulfurization process, the sulfur content of the molten iron after KR treatment is below 0.01 wt%; ② In the converter smelting process, a top-and-bottom combined blowing converter is used for smelting. The tapping temperature is controlled at 1580-1600℃, and the tapping C is ≤0.26 wt%, P and S are controlled within 0.02 wt%. Argon is blown throughout the tapping process, and 150-200Kg of lime is added to form slag. ③ In the LF refining step, when the ladle is placed in the LF position, the Al line is fed in, and a large amount of slag is used to control the slag formation. The white slag is kept for no less than 25 minutes. ④ In the VD vacuum refining step, the vacuum degree is ≤67Pa, the holding time is 12-15min, and the H content is ≤1.0ppm; ⑤ In the continuous casting process, the superheat is 10-20℃, and the billet is cooled for 12-24 hours after casting. ⑥ In the billet cleaning step, heated cleaning is adopted at a temperature of 80-400℃, with a cleaning depth-to-width ratio of 1:

3. After the cleaning is qualified, the billet is loaded into the furnace for heating. ⑦ The heating process includes a first-stage heating, a second-stage heating, and a uniform heating. The heating temperature of the first-stage heating is ≤950℃, the heating temperature of the second-stage heating is 1220-1240℃, and the heating time is 10±2cm / min. The temperature of the uniform heating section is 1200-1220℃, and the holding time is >30min.

8. The method for producing 27MnTiB high-strength wear-resistant steel plate according to claim 7, characterized in that, After the LF refining process is completed, calcium wire is fed until the Ca / S ratio is between 0.3 and 0.

6. The feeding speed of the calcium wire is 3.5-4 m / s, and at the same time, inert gas is blown in from the bottom of the ladle for stirring.

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