Carbon-manganese-silicon steel plate for ultra-heavy thickness pressure vessels and method for producing the same

Abstract

This invention discloses a carbon-manganese-silicon steel plate for ultra-thick pressure vessels and its production method. The chemical composition and mass percentage of the steel plate are as follows: C ≤ 0.12%, C+Mn / 6+Cr / 5: 0.42~0.43%, Si: 0.40~0.50%, Ni: 0.60~0.65%, Ti ≤ 0.002%, Nb ≤ 0.002%, V: 0.060~0.070%, N: 0.0070-0.0080%, Alt≥0.020%, with the remainder being Fe and unavoidable impurities. The production method of the steel plate includes smelting, rolling, and heat treatment processes. The steel plate provided by this invention has a thickness of 250~300mm, excellent comprehensive performance, fully meets the requirements of modern large-scale pressure vessel manufacturing, has stable quality, and is suitable for mass production.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a carbon manganese silicon steel plate for ultra-thick pressure vessels and its production method. Background Technology

[0002] Carbon manganese silicon steel plates for pressure vessels are widely used in the manufacture of key equipment such as oil and gas tanks, cryogenic spherical tanks, nuclear reactor pressure vessels, heat exchangers, and medium- and high-temperature boiler drums due to their low production cost and excellent overall performance. However, in recent years, with the increasing size of equipment and the ever-higher safety requirements of pressure vessels, ultra-thickness and ultra-high performance have become increasingly common in the design of pressure vessel materials.

[0003] However, there are very few production records of such steel plates with a thickness exceeding 250mm in the current market, and those that exist generally suffer from unsatisfactory performance and high production costs, failing to meet the growing market demand. This invention innovates the steel plate composition, smelting, rolling, and heat treatment processes, and utilizes steel ingots for production. While balancing cost control, steel plate thickness, strength, and low-temperature toughness, it provides an ultra-thick carbon manganese silicon steel plate for pressure vessels and its production method. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon manganese silicon steel plate for ultra-thick pressure vessels and its production method. The steel plate provided has a thickness of 250-300 mm and its performance meets the technical requirements for ultra-thick steel plates for pressure vessels.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0006] A carbon-manganese-silicon steel plate for ultra-thick pressure vessels has the following chemical composition and mass percentage: C≤0.12%, C+Mn / 6+Cr / 5: 0.42~0.43%, Si: 0.40~0.50%, Ni: 0.60~0.65%, Ti≤0.002%, Nb≤0.002%, V: 0.060~0.070%, N: 0.0070-0.0080%, Alt≥0.020%, with the remainder being Fe and unavoidable impurities.

[0007] The thickness of the steel plate described in this invention is 250-300 mm.

[0008] The production method of the ultra-thick carbon manganese silicon steel plate for pressure vessels described in this invention includes smelting, rolling and heat treatment processes.

[0009] The smelting process described in this invention is as follows: an ultra-pure steel smelting process is adopted, which includes pre-desulfurization of molten iron, primary smelting in an electric furnace, LF refining, and VD vacuum degassing. The LF process uses deep deoxidation of aluminum wire, and the VD process incorporates vanadium-nitrogen alloy. Flat steel ingots are used for casting, with an ingot thickness of 700-870mm. The ingot capping time is ≥12h, and the ingot removal time is ≥14h.

[0010] The rolling process described in this invention adopts a high-temperature, high-reduction process, with a reduction of ≥30mm per pass and a final rolling temperature of ≥920℃; after rolling, the MULPIC water-cooling equipment is used for repeated water immersion until the temperature reaches ≤600℃.

[0011] The heat treatment process described in this invention adopts a quenching + tempering process; the quenching adopts a car bottom roller hearth furnace, the holding temperature is 910-915℃, the holding time is 2.5-3min / mm, and after taking it out of the furnace, it is put into a water tank for accelerated cooling, the water temperature is ≤20℃, and the red temperature is ≤100℃.

[0012] The beneficial effects of adopting the above technical solution are that the steel plate provided by the present invention meets the technical requirements for ultra-thick steel plates for pressure vessels.

[0013] (1) Innovative low-carbon composition, designing a Si+Ni+V combined system. Silicon is not only a good deoxidizer, but also, when combined with aluminum in LF (sulfuric acid) treatment, it can significantly improve the deoxidation ability of aluminum; secondly, silicon has a strong strengthening effect, and can dissolve in ferrite and austenite to improve the hardness and strength of steel. Ni can significantly improve the toughness of the steel matrix and is a key element to ensure the toughness at -46℃ ultra-low temperature. V is also an excellent deoxidizer, and most importantly, V is an element that effectively obtains fine-grained martensite. Because V has a strong binding force with N, adding a certain amount of nitrogen to vanadium-containing steel can increase the driving force for the precipitation of the second phase of V, so that all the N in solid solution precipitates out, maximizing the grain-refining effect and precipitation strengthening effect of V.

[0014] (2) Flat steel ingots are used to ensure a certain compression ratio. At the same time, the demolding time is extended to improve the internal quality of the ingot. Addressing the difficulty of core transfer in thick plates and the poor effect of two-stage controlled rolling, this application adopts a large reduction in one-time rolling, followed by rapid cooling to the bainitic transformation region. This results in a higher number of substructures, creating more nucleation points for subsequent heat treatment. Quenching is performed in a car-bottom furnace to ensure sufficient heating, followed by timely immersion in water to obtain a refined martensitic structure.

[0015] (3) The steel plate obtained by the method of this invention has excellent comprehensive performance, with a tensile strength ReH of ≥460MPa and a tensile strength Rm of 590~690MPa at room temperature; an average impact energy of ≥200J at -46℃; a tensile strength Z of ≥35% in the thickness direction; good internal quality; and ultrasonic testing meets ASTM A578 / A578M grade C. It is suitable for mass production and has strong market competitiveness. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments.

[0017] Examples 1-6

[0018] (1) The chemical composition and mass percentage of carbon manganese silicon steel plates for ultra-thickness pressure vessels in each embodiment are shown in Table 1.

[0019] Table 1 Chemical composition and mass percentage of each embodiment

[0020] Example thickness C C+Mn / 6+Cr / 5 Si Ni Ti V Nb N Al 1 260 0.09 0.42 0.41 0.60 0.001 0.064 0.002 0.0076 0.029 2 300 0.11 0.423 0.44 0.63 0.002 0.070 0.002 0.0074 0.031 3 275 0.10 0.43 0.47 0.65 0.0009 0.061 0.001 0.0079 0.020 4 250 0.12 0.425 0.50 0.61 0.002 0.067 0.0014 0.0070 0.045 5 290 0.105 0.421 0.43 0.64 0.001 0.060 0.001 0.0072 0.053 6 280 0.097 0.428 0.49 0.62 0.0005 0.065 0.001 0.0080 0.044

[0021] In Table 1, the balance of chemical composition is Fe and unavoidable impurities.

[0022] (2) The production methods of carbon manganese silicon steel plates for ultra-thickness pressure vessels in each embodiment include smelting, rolling and heat treatment processes, specifically:

[0023] Smelting process: The process adopts an ultra-pure steel smelting process of hot metal pre-desulfurization + electric furnace primary smelting + LF refining + VD vacuum degassing. The LF process uses aluminum wire deep deoxidation, and the VD process introduces vanadium-nitrogen alloy. Flat steel ingots are used for casting, with an ingot thickness of 700-870mm. The ingot capping time is ≥12h, and the ingot removal time is ≥14h.

[0024] Rolling process: High temperature and large reduction process is adopted, with a reduction of ≥30mm per pass and a final rolling temperature of ≥920℃; after rolling, water is poured back and forth using MULPIC water cooling equipment until the temperature turns red ≤600℃.

[0025] Heat treatment process: Quenching + tempering process is adopted; the quenching adopts a car bottom roller hearth furnace, the holding temperature is 910-915℃, the holding time is 2.5-3min / mm, and after taking it out of the furnace, it is put into a water tank for accelerated cooling, the water temperature is ≤20℃, and the red temperature is ≤100℃.

[0026] The specific parameters for the smelting and rolling processes in each embodiment are shown in Table 2, and the specific parameters for the heat treatment process of the steel plate are shown in Table 3.

[0027] Table 2 shows the specific parameters of the smelting and rolling processes in each embodiment.

[0028]

[0029]

[0030] Table 3 shows the specific parameters of the heat treatment process in each embodiment.

[0031]

[0032] (3) The product standard for carbon manganese silicon steel plates for ultra-thickness pressure vessels is ASME A537 / A537M. The steel plates obtained in each embodiment have good internal quality, and the ultrasonic testing meets ASTM A578 / A578M grade C. The mechanical property test results are shown in Table 4.

[0033] Table 4. Test results of mechanical properties of steel plates obtained in each embodiment.

[0034]

[0035] As can be seen from Table 4, the thick steel plate provided by this invention has stable quality and is suitable for mass production.

Claims

1. A carbon-manganese-silicon steel plate for ultra-heavy thickness pressure vessels, characterized in that, The chemical composition and mass percentage of the steel plate are as follows: C≤0.12%, C+Mn / 6+Cr / 5: 0.42~0.43%, Si: 0.40~0.50%, Ni: 0.60~0.65%, Ti≤0.002%, Nb≤0.002%, V: 0.060~0.070%, N: 0.0070-0.0080%, Alt≥0.020%, with the remainder being Fe and unavoidable impurities; The thickness of the steel plate is 250-300 mm; The steel plate has good internal quality, and ultrasonic testing meets ASTM A578 / A578M grade C. The mechanical properties of the steel plate in the delivery state meet the following requirements: room temperature tensile strength ReH≥460MPa, Rm:590~690MPa; -46℃ impact energy≥200J; The mechanical properties of the steel plate in the delivery state meet the following requirements: tensile strength in the thickness direction, reduction of area Z ≥ 35%; The steel plate production method includes smelting, rolling and heat treatment processes; The smelting process uses flat steel ingots for casting, with an ingot thickness of 700-870mm; the ingot cap removal time is ≥12h, and the ingot removal time is ≥14h. The rolling process adopts a high-temperature, high-reduction process, with a reduction of ≥30mm per pass and a final rolling temperature of ≥920℃; after rolling, the steel plate is repeatedly immersed in water using a MULPIC water-cooling device until it turns red at ≤600℃.

2. The method for producing carbon manganese silicon steel plates for ultra-thickness pressure vessels according to claim 1, characterized in that, The production method includes smelting, rolling and heat treatment processes; The smelting process uses flat steel ingots for casting, with an ingot thickness of 700-870mm; the ingot cap removal time is ≥12h, and the ingot removal time is ≥14h. The rolling process adopts a high-temperature, high-reduction process, with a reduction of ≥30mm per pass and a final rolling temperature of ≥920℃; after rolling, the steel plate is repeatedly immersed in water using a MULPIC water-cooling device until it turns red at ≤600℃.

3. The method of producing a carbon-manganese-silicon steel plate for ultra-heavy thickness pressure vessels according to claim 2, characterized in that, The smelting process adopts an ultra-pure steel smelting process of hot metal pre-desulfurization + electric furnace primary smelting + LF refining + VD vacuum degassing, wherein the LF process adopts aluminum wire deep deoxidation, and the VD process incorporates vanadium-nitrogen alloy.

4. The method for producing carbon manganese silicon steel plates for ultra-thick pressure vessels according to claim 2, characterized in that, The heat treatment process of the steel plate adopts a quenching + tempering process; the quenching adopts a car bottom roller hearth furnace, the holding temperature is 910-915℃, the holding time is 2.5-3min / mm, and the plate is placed in a water tank for accelerated cooling after being taken out of the furnace, with the water temperature ≤20℃, and the red temperature is ≤100℃.

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