Production method of preheating-free cutting of large-thickness wear-resistant steel plate
By optimizing the chemical composition and heat treatment process of wear-resistant steel, the problems of easy cracking during cutting of thick wear-resistant steel and the complexity of the preheating process were solved, enabling preheating-free cutting at room temperature, improving cutting quality and efficiency, and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUNAN VALIN XIANGTAN IRON & STEEL CO LTD
- Filing Date
- 2026-01-27
- Publication Date
- 2026-06-05
AI Technical Summary
Thick-walled wear-resistant steel is prone to cracking during the cutting process. Traditional preheating processes are energy-intensive, costly, and have unstable quality. They are also harmful to the health of operators and cannot meet the needs of precision parts.
By rationally designing the C, Mn, Cr, and Ni alloy content, eliminating Nb, strictly controlling P and S content, and combining rare earth and calcification treatment, the billet is stacked and slowly cooled and then annealed at high temperature to achieve high strength and uniformity of the steel plate. Preheating-free cutting is then performed using quenching and tempering heat treatment.
The produced steel plates can be flame-cut at room temperature without preheating. The surface hardness is 400~440HB, the core hardness is ≥340HB, the yield strength is 900~1150MPa, the tensile strength is ≥1200MPa, the elongation is ≥14%, the impact energy absorbed at -40℃ is ≥45J, and there are no cracks when the cutting speed is 150~250mm/min.
Smart Images
Figure CN122147207A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of metallurgical technology and relates to a method for producing thick wear-resistant steel without preheating. Background Technology
[0002] Wear-resistant steel, a special steel with high hardness and wear resistance, is widely used in mining machinery, engineering machinery, and metallurgical equipment. Its core value lies in extending equipment life and reducing maintenance costs through excellent wear resistance. With the increasing trend towards larger industrial equipment, downstream manufacturers are continuously growing their demand for thicker wear-resistant steel (typically ≥60mm thick). The susceptibility to cracking in thicker wear-resistant steel is currently a core technological bottleneck. Its high carbon content (0.15~0.3%) and the addition of alloying elements such as chromium, molybdenum, and vanadium to enhance hardness result in high hardenability and high thermal sensitivity. During cutting, localized high temperatures cause rapid heating and cooling of the material, leading to a martensitic phase transformation and generating enormous internal stress. When the stress exceeds the material's strength limit, cold cracks easily appear on the cut surface, sometimes penetrating the entire plate and causing product scrap.
[0003] Traditional cutting processes require preheating thick wear-resistant steel to 150-200℃ to relieve stress, but this has several drawbacks: First, it is energy and time-consuming, with thick plates requiring several hours to preheat, and energy consumption accounting for more than 30% of the total cutting cost. Second, there are limitations in equipment and operation; large preheating furnaces require significant investment and occupy a large area, making them unaffordable for small and medium-sized enterprises, while localized preheating (such as flame gun heating) can easily lead to uneven temperature distribution, exacerbating the risk of cracking. Third, the process is complex, requiring strict control of the preheating temperature (too high a temperature softens the material, too low a temperature fails to relieve stress), demanding extremely high operator skills. Furthermore, the quality stability of the manufacturing process is difficult to guarantee. Even with preheating, cutting quality is still affected by environmental factors (temperature, humidity) and manual operation: uneven preheating can lead to serrated defects or microcracks on the cut surface, requiring additional grinding; significant batch-to-batch quality differences make it difficult to meet the requirements of downstream enterprises for precision components; high-temperature preheating can also thicken the oxide layer of the material, generating harmful fumes during cutting, endangering the health of operators.
[0004] To resolve the triple contradiction of "efficiency, cost, and quality" in traditional processes and to promote the application of wear-resistant steel to larger and more precise fields, the development of thick wear-resistant steel that can be cut without preheating has significant industry value and market potential. Summary of the Invention
[0005] The purpose of this invention is to provide a method for producing thick wear-resistant steel without preheating. By rationally designing the C, Mn, Cr, and Ni alloy content, the method ensures excellent strength, toughness, and uniform cross-sectional hardness of the thick wear-resistant steel. Simultaneously, it eliminates Nb and strictly controls P and S content to reduce center segregation and large microalloy precipitates in the billet. Rare earth and calcification treatments improve steel purity. Combined with slow cooling of the billet stacking, high-temperature annealing and hydrogen diffusion of the steel plate, and tempering heat treatment, the method achieves the goal of producing thick wear-resistant steel without preheating. The produced 60-100mm thick wear-resistant steel plates have a surface hardness of 400-440HB, a core hardness ≥340HB, a yield strength of 900-1150MPa, a tensile strength ≥1200MPa, an elongation ≥14%, and an impact absorption energy ≥45J at -40℃. Under normal temperature conditions (0-30℃), flame cutting (cutting speed 150-250mm / min) without preheating results in no cracks.
[0006] The technical solution of this invention: A method for producing thick wear-resistant steel plates without preheating cutting, wherein the chemical composition of the steel (mass percentage) is C=0.15~0.17, Si=0.20~0.30, Mn=0.90~1.00, P≤0.010, S≤0.002, Cr=0.6~0.65, Mo=0.50~0.55, Ni=0.6~0.7, Ti=0.014~0.020, Nb≤0.005, Alt=0.030~0.060, B=0.0014~0.0020, H≤0.00012 for voids, H≤0.00015 for intermediate ladles, N≤0.0040, O≤0.0010, with the remainder being Fe and unavoidable impurities; the key process steps include: (1) Smelting: The KR-BOF-LF-RH-CC smelting process is adopted. The molten iron is treated with deep desaturation and dephosphorization. The vacuum degree of the RH furnace is ≤67Pa and the holding time is ≥18min. When the vacuum is maintained for 12~15min, 30%Ce rare earth alloy 30~50kg and 40~60kg silicon-calcium-barium alloy are added. After breaking the vacuum, soft blowing is performed for 20~25min. The gas content of the molten steel in the tundish is measured as H≤0.00015, N≤0.0040, O≤0.0010. The continuous casting process adopts measures such as full-process protective casting, controlling the moisture of protective slag and covering agent, and tundish baking to reduce the H content. The tundish superheat is controlled at 6~13℃. At the same time, dynamic light reduction technology is adopted to improve the internal quality of the continuous casting billet. The billet size is thickness×width×length=300mm×2270mm×bill length mm. After the billet is produced, it is stacked for slow cooling and hydrogen expansion. The stacking cooling time is ≥48h and the stacking temperature is ≤100℃.
[0007] (2) Billet heating: furnace temperature ≤1250℃, heating temperature 1180~1200℃, total furnace time 1.0~1.2min / mm×slab thickness mm, rolling compression ratio ≥3.
[0008] (3) First stage rolling: the initial rolling temperature is ≥1050℃, the single pass reduction is 35~45mm; the final rolling temperature is ≥950℃, and the intermediate rolling thickness is the target rolling thickness +40~60mm.
[0009] (4) Second stage rolling: the initial rolling temperature is 860~890℃, the final rolling temperature is 780~820℃, the stacking is slow cooling within 2 hours after rolling, the stacking cooling time is ≥72h, and the stacking temperature is ≤100℃.
[0010] (5) Annealing: The rolled steel plate is tempered at 640~660℃ for 60±2h, then cooled to 200℃ in the furnace and then air-cooled to room temperature.
[0011] (6) Heat treatment: The quenching and tempering process is adopted. The quenching temperature is 890~910℃ and the time is the thickness of the steel plate mm × (1.8~2.1) min / mm; the tempering temperature is 200~220℃ and the tempering time is the thickness of the steel plate mm × (5.5~6.0) min / mm.
[0012] (7) Post-furnace cutting: The steel plate after heat treatment is cut without preheating at an ambient temperature of 0~30℃. The cutting speed is 150~250mm / min. After cutting, the cutting edge is ground and colored or magnetic particle testing is performed after ≥48h. There are no delayed crack defects.
[0013] The wear-resistant steel plate obtained by the above method has a surface hardness of 400~440HB, a core hardness of ≥340HB, a yield strength of 900~1150MPa, a tensile strength of ≥1200MPa, an elongation of ≥14%, and an impact absorption energy of ≥45J at -40℃.
[0014] The main innovations of this invention are: 1) The Nb content is clearly limited to ≤0.005% in alloying elements to reduce the aggregation of Nb-containing precipitates and improve the quality of the central part of the billet.
[0015] 2) Strictly control the H content (H in the intermediate package ≤ 0.00015) to reduce the amount of diffusible hydrogen and its accumulation, effectively preventing the occurrence of hydrogen-induced delayed cracks.
[0016] 3) Rare earth and calcification treatments are carried out during the smelting process to effectively refine and reduce the size and quantity of inclusions in the molten steel, thereby improving the internal quality.
[0017] 4) The rolled steel plate undergoes high-temperature annealing and hydrogen dilution treatment to further reduce the hydrogen content in the steel.
[0018] 5) Excellent mechanical properties: surface hardness 400~440HB, core hardness ≥340HB, yield strength 900~1150MPa, tensile strength ≥1200MPa, elongation ≥14%, impact absorption energy at -40℃ ≥45J; 6) Achieve crack-free flame cutting without preheating at room temperature (0~30℃) (cutting speed 150~250mm / min).
[0019] The beneficial effects of this invention are as follows: The method of this invention produces thick wear-resistant steel that can be cut without preheating. It employs a process route of KR molten iron pretreatment + converter smelting + LF refining + RH vacuum degassing + continuous casting + billet heating + rolling + annealing + tempering, combined with appropriate composition design, smelting, and heat treatment processes. This process is simple and highly operable. Rare earth and calcification treatments are carried out during smelting, and hydrogen control or diffusion treatment is performed throughout the process. Combined with one-stage rolling with high reduction and dedicated quenching parameters, excellent microstructure and internal quality are achieved, enabling the cutting of thick wear-resistant steel without preheating. This effectively solves the triple contradiction of "efficiency, cost, and quality" in traditional thick wear-resistant steel cutting processes, promoting the expansion of wear-resistant steel applications to larger and more precise fields, and possessing significant industry value and market potential. Attached Figure Description
[0020] Figure 1 Metallographic image of Example 1.
[0021] Figure 2 This is a photograph of inclusion detection in Example 1. Detailed Implementation Example 1
[0022] A method for producing thick wear-resistant steel without preheating and cutting involves smelting one furnace to roll a 100mm thick steel plate. The chemical composition (weight percentage) of the steel is shown in Table 1, with the remainder being Fe and unavoidable impurities. The method includes the following key process steps: (1) Smelting: The KR-BOF-LF-RH-CC production process is adopted. The molten iron is subjected to deep desaturation and dephosphorization treatment. The vacuum degree of the RH furnace is ≤67Pa and the holding time is 20min. When the vacuum is maintained for 14min, 50kg of 30%Ce rare earth alloy and 60kg of silicon-calcium-barium alloy are added. After breaking the vacuum, soft blowing is performed for 22min. The gas content of the molten steel is measured in the tundish: H content is 0.00012%, N content is 0.0035%, and O content is 0.0008%. The superheat of the tundish is controlled at 7~11℃. The billet size is thickness×width×length=260mm×2250mm×bill length mm. After the billet is produced, it is stacked and slowly cooled for hydrogen expansion. The stacking cooling time is 62h and the stacking temperature is 89℃.
[0023] (2) Billet heating: furnace temperature 1243℃, heating temperature 1182℃, total furnace time 320min, rolling compression ratio 3.
[0024] (3) First stage rolling: initial rolling temperature 1072℃, single pass reduction: 39~43mm; final rolling temperature 992℃, intermediate rolling thickness 142mm.
[0025] (4) Second stage rolling: initial rolling temperature 882℃, final rolling temperature 813℃, slow cooling after 1.5 stacking, cooling time 76h, and destacking temperature 61℃.
[0026] (5) Annealing: The rolled steel plate is tempered at 650°C for 61 hours, then cooled to 196°C in the furnace and air-cooled to room temperature.
[0027] (6) Heat treatment: The quenching and tempering process is adopted. The quenching temperature is 903℃ and the time is 196min; the tempering temperature is 212℃ and the tempering time is 560min.
[0028] (7) Post-furnace cutting: The steel plate after heat treatment is cut without preheating at an ambient temperature of 17.8℃ (cutting speed 245mm / min). 64 hours after cutting, the cut edge is ground and colored for inspection to find no defects such as cracks.
[0029] The rolling and heat treatment parameters of the steel produced in Example 1 are shown in Tables 2 and 3. Samples of the 100mm thick wear-resistant steel produced according to the above process parameters were taken for metallographic analysis and inclusion observation. The microstructure was low-temperature tempered martensite with a grain size of grade 8 or higher. The inclusion detection grade was D0.5 and DS1.0. The yield strength, tensile strength, elongation, -40℃ impact performance, bending, and hardness of the wear-resistant plate in Example 1 were tested, and the results are shown in Table 4. The metallographic structure is as follows: Figure 1 As shown, inclusion detection is as follows Figure 2 As shown. Example 2
[0030] A method for producing thick wear-resistant steel without preheating involves smelting and rolling one heat of steel to produce 80mm thick steel plates. The chemical composition (weight percentage) of the steel is shown in Table 1, with the remainder being Fe and unavoidable impurities. The method includes the following key process steps: (1) The KR-BOF-LF-RH-CC production process is adopted. The molten iron is subjected to deep desaturation and dephosphorization treatment. The vacuum degree of the RH furnace is ≤67Pa and the holding time is 19min. When the vacuum is maintained for 14min, 40kg of 30%Ce rare earth alloy and 50kg of silicon-calcium-barium alloy are added. After breaking the vacuum, soft blowing is performed for 20min. The gas content of the molten steel is measured in the tundish: H content is 0.00014%, N content is 0.0038%, and O content is 0.0007%. The superheating of the tundish is controlled at 6~11℃. Dynamic light reduction technology is adopted to improve the internal quality of the continuous casting billet. The billet size is thickness × width × length = 300mm × 2270mm × billet length mm. After the billet is produced, it is stacked for slow cooling and hydrogen expansion (stacking time is 56h, and the stacking temperature is 93℃).
[0031] (2) Billet heating: furnace temperature 1248℃, heating temperature 1191℃, total furnace time 340min, rolling compression ratio 3.75.
[0032] (3) First stage rolling: initial rolling temperature 1078℃, single pass reduction: 37~42mm; final rolling temperature 973℃, intermediate rolling thickness 131mm.
[0033] (4) Second stage rolling: the initial rolling temperature is 878℃, the final rolling temperature is 796℃, the stacking is slow cooling within 1.5h after rolling, the stacking cooling time is 81h, and the unstacking temperature is 56℃.
[0034] (5) Annealing: The rolled steel plate is tempered at 650℃ for 59 hours, then cooled to 198℃ in the furnace and then air-cooled to room temperature.
[0035] (6) Heat treatment: The quenching and tempering process is adopted. The quenching temperature is 899℃ and the time is 158 min for the thickness of the steel plate; the tempering temperature is 214℃ and the tempering time is 452 min.
[0036] (7) Post-furnace cutting: The steel plate after heat treatment is cut without preheating at an ambient temperature of 5°C. After cutting, the cutting edge is ground and subjected to colorimetric testing. No delayed crack defects are found.
[0037] The rolling and heat treatment parameters of the steel produced in Example 2 are shown in Tables 2 and 3. Samples of the 80mm thick wear-resistant steel produced according to the above process parameters were taken for metallographic analysis and inclusion observation. The microstructure was low-temperature tempered martensite with a grain size of grade 8 or higher. The inclusion detection grade was D0.5 and DS1.0. The yield strength, tensile strength, elongation, -40℃ impact performance, bending, and hardness of the wear-resistant plate in Example 2 were tested, and the results are shown in Table 4.
[0038] Table 1. Main chemical composition (wt.%) of wear-resistant steel plates in the examples .
[0039] Table 2 Rolling process parameters of wear-resistant plates in the embodiments .
[0040] Table 3 Heat treatment process parameters for wear-resistant steel plates in the examples .
[0041] Table 4 Mechanical properties of wear-resistant steel plates from the examples .
Claims
1. A method for producing thick wear-resistant steel plates without preheating cutting, wherein the chemical composition of the steel (mass percentage) is C=0.15~0.17, Si=0.20~0.30, Mn=0.90~1.00, P≤0.010, S≤0.002, Cr=0.6~0.65, Mo=0.50~0.55, Ni=0.6~0.7, Ti=0.014~0.020, Nb≤0.005, Alt=0.030~0.060, B=0.0014~0.0020, H≤0.00012 for voids, H≤0.00015 for intermediate ladles, N≤0.0040, O≤0.0010, with the remainder being Fe and unavoidable impurities; the key process steps include: (1) Smelting: The KR-BOF-LF-RH-CC smelting process is adopted. The molten iron is treated with deep desaturation and dephosphorization. The vacuum degree of the RH furnace is ≤67Pa and the holding time is ≥18min. When the vacuum is maintained for 12~15min, 30%Ce rare earth alloy 30~50kg and silicon-calcium-barium alloy 40~60kg are added. After breaking the vacuum, soft blowing is performed for 20~25min. The gas content of the molten steel in the tundish is measured as H≤0.00015, N≤0.0040, and O≤0.0010. The continuous casting process adopts measures such as full-process protective casting, controlling the moisture of protective slag and covering agent, and tundish baking to reduce the H content. The tundish superheat is controlled at 6~13℃. At the same time, dynamic light reduction technology is adopted to improve the internal quality of the continuous casting billet. The billet size is thickness×width×length=300mm×2270mm×bill length mm. After the billet is produced, it is stacked for slow cooling and hydrogen expansion. The stacking cooling time is ≥48h and the stacking temperature is ≤100℃. (2) Billet heating: furnace temperature ≤1250℃, heating temperature 1180~1200℃, total furnace time 1.0~1.2min / mm×slab thickness mm, rolling compression ratio ≥3; (3) First stage rolling: the initial rolling temperature is ≥1050℃, the single pass reduction is 35~45mm; the final rolling temperature is ≥950℃, and the intermediate rolling thickness is the target rolling thickness +40~60mm. (4) Second stage rolling: the initial rolling temperature is 860~890℃, the final rolling temperature is 780~820℃, the stacking is slow cooling within 2 hours after rolling, the stacking cooling time is ≥72h, and the unstacking temperature is ≤100℃. (5) Post-rolling annealing: The rolled steel plate is subjected to hydrogen diffusion and homogenization treatment by high-temperature annealing process; (6) Heat treatment: The quenching and tempering process is adopted. The quenching temperature is 890~910℃ and the time is (1.8~2.1) min / mm (thickness of steel plate in mm); the tempering temperature is 200~220℃ and the tempering time is (5.5~6.0) min / mm (thickness of steel plate in mm). (7) Post-furnace cutting: The heat-treated steel plate is processed by flame cutting to obtain the required size.
2. The method for producing thick wear-resistant steel without preheating cutting according to claim 1, characterized in that: The wear-resistant steel plate has a surface hardness of 400~440HB, a core hardness of ≥340HB, a yield strength of 900~1150MPa, a tensile strength of ≥1200MPa, an elongation of ≥14%, and an impact absorption energy of ≥45J at -40℃.