SX610CF hydroelectric steel for pumped storage power station and manufacturing method of SX610CF hydroelectric steel

Abstract

The invention discloses an SX610CF hydroelectric steel plate for a pumped storage power station. The SX610CF hydroelectric steel plate comprises the following components: 0.04-0.07% of C; 0.25 to 0.35 percent of Si; mn: 1.30 to 1.40%; the content of Als is 0.025 to 0.055 percent; 0.10% to 0.20% of Cr; 0.15% to 0.25% of Mo; 0.20% to 0.30% of Cu; 0.90% to 1.20% of Ni; ti: 0.008% to 0.018%; 0.015% to 0.025% of V; 0.025% to 0.035% of Nb; b: 0.0008% to 0.002% of the total weight of the And the balance of Fe. Wherein Pcm is less than or equal to 0.20%; and Ceq is less than or equal to 0.44%. According to the invention, the strength problem and the 1 / 2 and 1 / 4 thickness impact toughness problem on the premise of low Pcm value are solved, and the stability in the use process can be ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of medium and thick steel plate production, and specifically relates to a SX610CF hydroelectric steel for a pumped storage power station and a manufacturing method thereof. Background Art

[0002] At present, when customers use 490MPa grade steel plates, they tend to design them according to Q / CTG 24-2015 "Technical Conditions for High Strength and Low Welding Crack Sensitivity Steel Plates for Large Hydropower Projects". Compared with GB / T 31946-2015, its composition requirements are stricter in C, but looser in terms of elements such as Cr and Nb. The Pcm requirements are basically the same, but the toughness requirements are higher. Based on the current situation that the market mainly uses Q / CTG24-2015, the research and development work is also mainly carried out on SX610CF, aiming to solve the strength problem under the premise of low Pcm value and the impact toughness problem of 1 / 2 and 1 / 4 thickness.

[0003] According to the current information, publication number CN109972032 A proposes a low welding crack sensitivity extra-thick steel plate 610CF and a production method thereof. Its technical solution includes a series of steps including KR molten iron pretreatment, converter steelmaking, argon blowing treatment, LF refining, VD vacuum, heating, rolling, and heat treatment to complete the production of the steel plate. Its advantage is that it can stably transform the required structure, but the composition setting is broad, the composition is not specifically designed, and the alloy content is not reflected.

[0004] Publication No. CN115717219 B proposes a high-strength steel Q610CF for hydropower engineering and a production method thereof, the process comprising: using a temperature-average rolling + relaxation process, through molten iron pretreatment, converter smelting, LF refining, vacuum refining, casting, heating, rolling, controlled cooling and slow cooling. The performance of the 610CF steel plate described in the document can meet the standard requirements, but the production line uses a temperature-average rolling + relaxation process, which affects the production rhythm and increases costs. The subsequent heat treatment process does not result in the inability to ensure the stability of the steel plate performance.

[0005] Publication No. CN117758146 A discloses a thick SX610CF hydroelectric steel and its production method, including clean steel smelting, involving converter smelting, LF refining and VD refining. The use of the present invention to manufacture SX610CF steel plates can reduce the total oxygenation of molten steel and eliminate large and medium-sized inclusions in the steel. However, the production of steel plates is only suitable for 220-250mm thick steel plates. Summary of the invention

[0006] The purpose of the present invention is to provide a SX610CF hydroelectric steel for pumped storage power stations and a manufacturing method thereof. Through reasonable component composition, smelting control and rolling process coordination, SX610CF hydroelectric steel with a thickness greater than 50 mm and less than 80 mm is produced. The strength problem under the premise of low Pcm value and the impact toughness problem of 1 / 2 and 1 / 4 thickness are mainly solved, so that it has good uniformity of cross-sectional performance in the thickness direction and ensures the performance stability of the steel plate in the environment in which it is used.

[0007] The present invention is realized by the following technical scheme: a SX610CF hydroelectric steel plate for a pumped storage power station, characterized in that it comprises the following components by mass content: steel plate thickness>50-80mm: C: 0.04-0.07%; Si: 0.25-0.35%; Mn: 1.30-1.40%; P: ≤0.012%; S: ≤0.003%; Als: 0.025-0.055%; Cr :0.10-0.20%;Mo:0.15-0.25%;Cu:0.20-0.30%;Ni:0.90-1.20%;Ti:0.008-0.018%;V:0.015-0.025%;Nb:0.025-0.035%;B:0.0008-0.002%;Pcm:≤0.20%;Ceq:≤0.44%, the rest are Fe and residual elements. Among them: Ceq=C+Mn / 6+Si / 24+Ni / 40+Cr / 5+Mo / 4+V / 14; Pcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B.

[0008] The present invention also discloses a method for manufacturing the steel plate, which includes a molten iron pretreatment step, a converter smelting step, a LF treatment step, a RH vacuum treatment step, a continuous casting step, a steel plate stacking step, a heating step, a rolling step, and a cooling step, and is characterized in that: The smelting steps: The molten iron arriving at the station must be stripped of the front slag and the rear slag. After the molten iron is stirred by KR to remove S, the S content of the molten iron must be ≤0.005%. Dry scraps must be used to add scrap steel to the converter. The tapping temperature is ≥1590℃, and the tapping C is ≤0.04%. The converter oxygen lance and smoke hood are tightly sealed without any leakage. A slag cone is used to block the slag at the end of tapping to avoid slag during tapping. If the slag blocking fails, the furnace must be lifted in advance to avoid the slag returning to P. The ladle must be kept clean without residual steel or slag, and the steel must be tapped from the red tank. The LF refining process adopts a large slag volume operation, and the final slag at the end of refining is required to be a foamy white slag with good fluidity and appropriate viscosity. The vacuum holding time is greater than 15 minutes. At the same time, the ladle is fed with Ca wire to calcify and denature the inclusions. The static argon blowing time after wire feeding is ≥10 minutes, and the target is 15 minutes.

[0009] The continuous casting steps include: implementing full-process protection pouring, the casting machine adopts secondary cooling electromagnetic stirring and light pressure reduction at the end of solidification; the target superheat of the tundish is ≤25°C; the target pulling speed of continuous casting is maintained at a constant pulling speed, and the liquid level fluctuation is controlled within ±3mm.

[0010] The rolling steps: The cross section of the ingot is 453mm×2000mm, the uniform heating system is 1220℃×500min; the reduction in at least 2 passes is greater than 40mm; the thickness of the intermediate ingot is set to ≥135mm; the finishing rolling system is 780℃-810℃; the final cooling and returning to red is 620℃-680℃.

[0011] The cooling step is as follows: the steel plates are stacked together, the stacking temperature is controlled within the range of 500-650°C, there is a pad at the bottom and a cover at the top, and an insulation cloth or insulation cover is added, and the air outlet is avoided. The insulation cloth or insulation cover can be removed and the steel plates can be unstacking after being stacked for ≥36 hours, so that the steel plates can obtain an ideal tissue type.

[0012] The heat treatment step: Steel plate quenching system: 900℃×200min; tempering system: 580-620℃×240min. After leaving the furnace, air cool to room temperature.

[0013] Furthermore: the prepared steel plate has a thickness of 50 mm to 80 mm, and the steel plate is mainly a tempered bainite structure, and the performance meets the requirements of GB / T 31946-2015 and Q / CTG 24-2015.

[0014] The advantages of the present invention are as follows: the SX610CF steel plate for pumped storage power stations of the present invention solves the strength problem under the premise of low Pcm value and the impact toughness problem of 1 / 2 and 1 / 4 thickness, so that it has good uniformity of cross-sectional performance in the thickness direction, especially the improvement of performance at the 1 / 2 thickness position, which can ensure stability during use. The method of the present invention can enable the rolling force to effectively penetrate into the core position, so that defects such as microcracks and looseness in the core can be welded and eliminated. A reasonable heat treatment system enables the steel plate to obtain a stable tempered bainite structure to enhance its strength and toughness. In particular, the specific tempering system can make the obtained structure stable and refined, and the grains are evenly arranged. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the result of a series of impact tests on a steel plate with a thickness of 80 mm and at a 1 / 4 thickness position of the present invention; Figure 2 It is the metallographic structure of the SX610CF 60mm thick steel plate of the present invention; Figure 3The metallographic structure of the SX610CF 80 mm thick steel plate of the present invention. DETAILED DESCRIPTION

[0016] The invention discloses a SX610CF hydroelectric steel plate for a pumped storage power station, which comprises the following components by mass content: C: 0.04-0.07%; Si: 0.25-0.35%; Mn: 1.30-1.40%; P: ≤0.012%; S: ≤0.003%; Als: 0.025-0.055%; Cr: 0.10-0.20%; Mo: 0.15-0.25%; Cu: 0.20-0.30%; Ni: 0.90-1.20%; Ti: 0.008-0.018%; V: 0.015-0.025%; Nb: 0.025-0.035%; B: 0.0008-0.002%; Pcm: ≤0.20%; Ceq: ≤0.44%, and the rest are Fe and residual elements. Among them: Ceq=C+Mn / 6+Si / 24+Ni / 40+Cr / 5+Mo / 4+V / 14; Pcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B.

[0017] The present invention also discloses a method for manufacturing the steel plate, which includes a molten iron pretreatment step, a converter smelting step, a LF treatment step, a RH vacuum treatment step, a continuous casting step, a steel plate stacking step, a heating step, a rolling step, and a cooling step; wherein: The smelting steps are as follows: the molten iron at the station must be stripped of the front slag and the rear slag to ensure that the thickness of the slag layer on the liquid surface is ≤20mm; the molten iron must be stirred by KR to remove sulfur to ensure that the molten iron S is ≤0.005%; the desulfurization cycle is ≤25min, the desulfurization temperature drop is ≤25°C, the scrap steel added to the converter must be dry scraps, the tapping temperature is ≥1590°C, the tapping C is ≤0.04%, the converter oxygen lance and the smoke hood are tightly sealed without leakage points; the slag is blocked by a slag cone at the end of tapping to avoid slag during tapping. If the slag blocking fails, the furnace must be lifted in advance to avoid the slag returning to P; the vacuum holding time is greater than 15min; the ladle is ensured to be clean, without residual steel and residue, and the steel is tapped from the red tank; the LF refining process adopts a large slag volume operation, and the final slag at the end of refining is required to be a foamy white slag with good fluidity and appropriate viscosity. At the same time, the ladle is fed with Ca wire to perform calcification and denaturation treatment on the inclusions. The static argon blowing time after wire feeding is ≥10min, and the target is 15min.

[0018] The continuous casting steps include: implementing full-process protection pouring, the casting machine adopts secondary cooling electromagnetic stirring and light pressure reduction at the end of solidification; the target superheat of the tundish is ≤25°C; the target pulling speed of continuous casting is maintained at a constant pulling speed, and the liquid level fluctuation is controlled within ±3mm.

[0019] The rolling steps are as follows: the cross section of the ingot is 453mm×2000mm, the soaking heating system is 1220℃×500min; the reduction amount of at least 2 passes is greater than 40mm; the thickness of the intermediate ingot is set to ≥135mm; the finishing rolling system is 780℃-810℃; and the final cooling and returning to red is 620℃-680℃.

[0020] The cooling step is as follows: the steel plates are stacked together, the stacking temperature is controlled within the range of 500-650°C, there is a pad at the bottom and a cover at the top, and an insulation cloth or insulation cover is added, and the air outlet is avoided. The insulation cloth or insulation cover can be removed and the steel plates can be unstacking after being stacked for ≥36 hours, so that the steel plates can obtain an ideal tissue type.

[0021] The heat treatment steps are as follows: steel plate quenching system: 900℃×200min; tempering system: 580-620℃×240min. After being taken out of the furnace, the steel plate is air-cooled to room temperature. After being taken out of the furnace, the steel plate is air-cooled to room temperature. After being taken out of the furnace, the steel plate is air-cooled to room temperature.

[0022] Embodiment: The Ni content of SX610CF hydroelectric steel with a thickness of 50mm-80mm is increased, and micro-B alloying treatment is carried out, and the tempering temperature is appropriately reduced, while Pcm, strength, and core toughness indicators are guaranteed, Mo and Cu components are increased, and Mn content is reduced, while Pcm is guaranteed and tempering stability is increased.

[0023] Example 1 selected 60mm, Example 2 selected 80mm thickness specifications, the ingot section was 453mm×2000mm, two-stage controlled rolling was used to produce hot rolled materials, 900℃ quenching and 580-620℃ tempering were selected in a roller bottom non-oxidation heat treatment furnace, and the strength and toughness of the steel plate stably met the standard requirements. The smelting components of Example 1 and Example 2 are shown in Table 1. The target specifications of steel plate rolling are 60mm×2500mm×12000+mm and 80mm×2500mm×10000+mm, and the hot rolling process parameters are shown in Table 2.

[0024]

[0025] The test steel plates were quenched and tempered, and then subjected to tensile, cold bending and impact toughness tests. The tensile and cold bending test results are shown in Table 3. As can be seen from the table, the performance of the head, middle and tail of the 60mm and 80mm thick steel plates is stable, the surface rolled steel plates have good uniformity in the length direction, there is no large performance difference, and they have good consistency.

[0026]

[0027] The impact toughness and aging impact toughness results of the steel plates are shown in Table 4. As can be seen from the table, the performance of the 1 / 4 and 1 / 2 positions of the thickness of the 60mm and 80mm thick steel plates is good and stable, the quality of the surface steel plate thickness section direction is excellent, and there is no difference in the performance in the thickness direction. It can be seen that this rolling process can achieve the stability of the full section thickness performance and ensure stable performance during use.

[0028]

[0029] The steel plate of Example 2 was subjected to a series of temperature impact toughness tests at the 1 / 4 thickness position. The results showed that the SATT temperature at the 1 / 4 thickness position of the steel was around -80°C. Figure 1 A series of impact tests were conducted on 80mm thick steel plates at 1 / 4 thickness, and a group (3) of impact energy tests were conducted every 10°C. The results showed that the impact energy showed a decreasing trend with decreasing temperature, but even at -80°C, the average impact energy was still above 170J, showing good low-temperature toughness characteristics and no obvious brittle transition characteristics, so it can meet the technical requirements under different temperature use environments.

[0030] Refer to the attached Figure 2 , Figure 3 The metallographic structure of Example 1 and Example 2 is tempered bainite. After the quenching structure is homogenized, the tempering makes the structure uniform and stable, with stable grain distribution and size, so that it has good toughness and strength.

[0031] The SX610CF steel plate for pumped storage power station manufactured by the present invention has stable strength and impact toughness at 1 / 2 and 1 / 4 thickness positions under the premise of meeting the low Pcm value, and the 1 / 4 thickness position has stability of impact toughness at low temperature, which can meet different use environment conditions. The present invention also supplements the manufacturing method and technical conditions of SX610CF steel plate for pumped storage power station with a thickness of >50-80mm.

[0032] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A SX610CF hydroelectric steel for a pumped storage power station, characterized in that: The invention comprises the following components in mass percentage: C: 0.04-0.07%; Si: 0.25-0.35%; Mn: 1.30-1.40%; P: ≤0.012%; S: ≤0.003%; Als: 0.025-0.055%; Cr: 0.10-0.20%; Mo: 0.15-0.25%; Cu: 0.20-0.30%; Ni: 0.90-1.20%; Ti: 0.008-0.018%; V: 0.015-0.025%; Nb: 0.025-0.035%; B: 0.0008-0.002%; Pcm: ≤0.20%; Ceq: ≤0.44%, the rest is Fe and residual elements; where: Ceq=C+Mn / 6+Si / 24+Ni / 40+Cr / 5+Mo / 4+V / 14; Pcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B.

2. A method for manufacturing SX610CF hydroelectric steel for pumped storage power stations as claimed in claim 1, comprising a molten iron pretreatment step, a converter smelting step, a LF treatment step, a RH vacuum treatment step, a continuous casting step, a steel plate stacking step, a heating step, a rolling step, and a cooling step; characterized in that: The smelting steps include: using KR to remove sulfur, controlling the sulfur content of the molten iron to ≤ 0.005%, using a large amount of slag in the LF refining process, and using the ladle to feed the Ca wire. The static argon blowing time after feeding the wire is ≥ 10 minutes, and the vacuum pressure holding time is greater than 15 minutes; The continuous casting step: the casting machine adopts secondary cooling electromagnetic stirring and light pressure at the end of solidification to control the superheat of the tundish to ≤25°C; the casting speed is kept constant during the continuous casting process, and the liquid level fluctuation is controlled within ±3mm; The rolling steps are as follows: the cross section of the ingot is 453 mm×2000 mm, the soaking heating system is 1220° C.×500 min; the intermediate ingot thickness is set to ≥135 mm; the finishing rolling system is 780° C.-810° C.; the final cooling and returning to red is 620° C.-680° C.; at least two passes of the rolling reduction are greater than 40 mm; The cooling step comprises water cooling after rolling, stacking the steel plates, unstacking after stacking for ≥36 hours, and controlling the stacking temperature within the range of 500-650°C; The heat treatment steps are as follows: steel plate quenching system: 900°C×200min; tempering system: 580-620°C×240min; air cooling to room temperature after being taken out of the furnace.

3. The method for manufacturing SX610CF hydroelectric steel for pumped storage power station according to claim 2, characterized in that: The thickness of the steel plate is 50mm-80mm; the steel plate is a tempered bainite structure.

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