Production method of nickel-chromium-iron-based alloy plate

Abstract

The invention discloses a production method of a nickel-chromium-iron-based alloy plate. The nickel-chromium-iron-based alloy plate comprises the following components: 0.05-0.08% of C; 0.25 to 0.45 percent of Si; mn: 0.55 to 0.80%; less than or equal to 0.025% of P; s < = 0.005%; cr: 24.5 to 26.0%; ni: 36.0 to 37.5%; 0.30% or less of Cu; 0.55 to 0.65 percent of Nb; 0.10-1.0% of Mo, and less than or equal to 2.5% of residual element W; less than or equal to 0.010% of B; 0.10% or less of Al; 0.10% or less of Ti; 0.15% to 0.60% of [N]; and the balance of Fe and inevitable impurities. The rolling technology comprises the steps of electric arc furnace smelting, AOD refining, LF refining, die casting, surface cleaning, heating, first-heating-number rolling, dead head cutting, surface cleaning, second-heating-number rolling, third-heating-number rolling, forming rolling, water cooling, surface cleaning, solid solution heat treatment and acid pickling. According to the nickel-chromium-iron-based alloy plate and the preparation method thereof, on the basis of optimizing components, reasonable smelting, rolling and heat treatment processes and a short-process nickel-chromium-iron-based alloy plate production process are adopted, so that the production cost is reduced, and better product performance can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of steel material processing technology, and specifically relates to a production process for a nickel-chromium-iron based alloy plate material that can be used for manufacturing a photovoltaic polysilicon cold hydrogenation reactor steel plate. Background Art

[0002] As my country's energy revolution continues to deepen, the proportion of renewable energy and clean energy in the field of energy production and consumption continues to increase. Building a green, low-carbon, clean and efficient energy system is a major trend in my country's energy development. In recent years, the explosive growth of wind power and photovoltaic power generation has posed new challenges to the development of new energy due to shortcomings such as "no wind in extreme heat", "no light in the late peak", and "large installed capacity and small power". Various provinces and cities have successively issued policies and guidance on supporting energy storage for renewable energy, requiring centralized / distributed wind power and photovoltaic devices to be equipped with 20%~25% energy storage capacity, and vigorously developing a new energy model that integrates power generation and energy storage.

[0003] High-purity polysilicon is the basic raw material for solar photovoltaic and electronic industries. With the development of solar energy applications, the use of high-purity polysilicon will also increase day by day. The production of high-purity polysilicon requires the use of core equipment such as cold hydrogenation reactors, because it needs to have high temperature and corrosion resistance in the production process of polysilicon. The main material involved is a solid solution strengthened nickel-chromium-iron alloy. Due to its excellent high temperature strength and resistance to oxidation, nitriding and other forms of high temperature corrosion, and good cold and hot processing and forming, it is widely used in core pressure vessel equipment such as cold hydrogenation reactors, gas-to-gas heat exchangers, towers, spherical tanks, and reduction furnaces in the polysilicon industry. It can reduce the weight of the structure, save materials, and reduce production costs while maintaining the strength of the design structure. However, domestic material manufacturing started late, steel plate production technology is relatively backward compared to foreign countries, and the delivery cycle is long. It is difficult to produce steel plate products with excellent comprehensive performance through short process methods. Summary of the invention

[0004] In order to overcome the defects of the prior art, the present invention obtains a nickel-chromium-iron based alloy plate product with excellent comprehensive performance through reasonable steel ingot rolling and heat treatment processes on the basis of optimizing the composition.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A method for producing a nickel-chromium-iron-based alloy plate, the requirements for the mass percentage of the chemical composition elements of the plate are: C: 0.05-0.08%; Si: 0.25-0.45%; Mn: 0.55-0.80%; P≤0.025%; S≤0.005%; Cr: 24.5-26.0%; Ni: 36.0-37.5%; Cu≤0.30%; Nb: 0.55-0.65%; Mo: 0.10-1.0%; residual elements W≤2.5%; B≤0.010%; Al≤0.10%; Ti≤0.10%; [N]0.15-0.60%; the balance is Fe and unavoidable impurities; The average grain size of the steel plate is grade 4.5, the room temperature yield strength is 473MPa, the room temperature tensile strength is 818Mpa, the high temperature yield strength is 327MPa, the room temperature tensile strength is 580Mpa, and the average corrosion rate is 0.045mm / year.

[0006] The process includes the following steps: Step 1: designing and proportioning the ingredients according to the composition of the nickel-chromium-iron-based alloy, performing electric arc furnace smelting → AOD refining → LF refining, and pouring to obtain a steel ingot; Step 2: Grinding and cleaning the surface defects of the obtained steel ingot; Step 3: subjecting the cleaned steel ingot to high temperature multi-fire rolling to obtain a nickel-chromium-iron based alloy steel plate; Step 4: subjecting the steel plate to solid solution heat treatment to obtain a finished nickel-chromium-iron alloy steel plate; Step 5: Pickle the steel plate to remove the surface oxide layer.

[0007] The grain size of alloy materials increases with the increase of solution temperature. When the solution is below 1200℃, due to the low solution temperature, the nucleation rate of recrystallization is much greater than the rate of grain growth, so the recrystallization nucleation process is dominant, and the carbides inside the alloy structure have not been fully dissolved. During the heating process of the material, they have a pinning effect on the grain boundary, preventing the growth of grains; when the solution temperature reaches 1200℃ and above, the recrystallization nucleation process is basically completed, carbides begin to dissolve into the matrix in large quantities, and the recrystallized grains grow rapidly. Therefore, the average recrystallized grain size increases rapidly with the increase of solution temperature and the extension of holding time.

[0008] Therefore, the solution heat treatment temperature is selected to be 1160~1200℃, the solution time is 200~300 minutes, and the solution is cooled to room temperature by water.

[0009] Step 1: The electric arc furnace smelting step includes adding primary material 8120 return material 7000kg, adding secondary material 8120 return material 4000kg, adding tertiary material 8120 return material 2400kg, adding metallic chromium 400kg, adding electrolytic nickel 470kg, measuring temperature, blowing argon and stirring, and tapping molten steel.

[0010] The AOD refining steps include blowing argon throughout the process; receiving molten steel according to O:Ar=4:1, O:Ar=1:1, O:Ar=1:3; blowing oxygen and nitrogen; adding 520kg of electrolytic nickel, 300kg of lime, 300kg of metal chromium, 8 aluminum ingots, and 100kg of industrial silicon during the first temperature increase and reduction process; adding 200kg of lime, 10 aluminum ingots, 604kg of electrolytic nickel, 200kg of metal chromium, and 7kg of cobalt during the second temperature increase and reduction process; adding 400kg of lime, 2 aluminum ingots, 40kg of electrolytic nickel, 200kg of metal chromium, 15kg of industrial silicon, and 10kg of electrolytic manganese during the third temperature increase and reduction process; and tapping.

[0011] The LF refining steps include heating, reducing, adding 120kg lime, 15kg calcium silicate powder, adding 4kg ferroboron, and tapping.

[0012] Furthermore, the multi-pass rolling in step three includes heating before rolling, one-pass rolling, cutting off the riser, surface cleaning, two-pass rolling, three-pass rolling, forming rolling, water cooling, and surface cleaning.

[0013] Preferably, the heating before rolling is room temperature charging, and the stepping furnace is used for heating. Heating is required before each rolling. Lubricant is applied to the surface before heating to prevent uneven deformation and surface cracks. The final heating temperature is 1250°C, and the holding time is 150-390min. The holding time is adjusted according to the thickness of the steel plate, wherein the holding time is: t=X×(0.6-0.8)+90, wherein t is the holding time, unit: min; X is the effective thickness, unit: mm; 0.6-0.8 is the heating experience coefficient, unit: min / mm; the reducing atmosphere is maintained during the heating process, and the residual oxygen content in the furnace is 2.5-4.0%; The first heat rolling is horizontal rolling, using single heating, multi-pass rolling, and a reduction of 200-250mm; The riser removal is to remove 200mm of the riser end of the rolled steel ingot in the length direction to eliminate the looseness and shrinkage defects of the riser end and prevent the surface quality of the next rolling plate from being affected; The second heat rolling is horizontal rolling, using single heating, multi-pass rolling, and a reduction of 60-70 mm; The three-pass rolling is longitudinal rolling, using single heating, multi-pass rolling, and a reduction of 60-70 mm; The forming rolling is longitudinal rolling, using single heating, multiple rolling passes, and a reduction of 50 to 60 mm.

[0014] After solution cooling, pickling and trimming are carried out to obtain the finished nickel-chromium-iron alloy steel plate.

[0015] The technical solution of the present invention has the following advantages: The production process adopted by the present invention can effectively control the comprehensive performance of the nickel-chromium-iron alloy steel plate. The steel ingot smelted by the present invention has good structural uniformity and density, less internal shrinkage and shrinkage holes, better end quality, and higher yield rate. The raw material contains 0.55-0.65% Nb, and the precipitation temperature of NbN is higher than that of NbC. By ensuring the N content, the combination of C and Nb is reduced, the inclusions are reduced, the precipitation of carbides on the grain boundaries is reduced, the formation of Cr carbides is reduced, the chromium depletion at the grain boundaries is avoided, the intergranular corrosion resistance is enhanced, and intergranular corrosion is prevented. At the same time, by controlling the rolling process, Nb will produce significant grain refinement and a certain degree of precipitation strengthening, so that the strength and toughness of the rolled plate are greatly improved; Cr: 24.5-26.0% increases the intergranular corrosion resistance time in the high sensitization range; Cu≤0.30% can improve strength and toughness, especially atmospheric corrosion resistance, and has a solid solution strengthening effect, improving the strength of high chromium and high chromium-nickel steels without reducing plasticity; Aluminum≤0.10% ensures sufficient deoxidation, and can refine grains and improve impact toughness, but it will affect the hot working performance, welding performance and cutting performance of steel, and its content needs to be strictly controlled.

[0016] The present invention adopts a high-temperature large-deformation multi-fire rolling process. The sufficient large deformation breaks the cast coarse dendrites or columnar crystals, improves the organization density and thermal conductivity, is beneficial to the effect of high-temperature diffusion, improves the unevenness of the chemical composition of the ingot and the uneven distribution of non-metallic inclusions, and can effectively improve the uniformity of the organization and the consistency of the longitudinal and transverse properties during the rolling process. At the same time, through repeated rolling and recrystallization, more equiaxed grains are obtained, and the austenite grains are refined, thereby obtaining excellent mechanical properties.

[0017] The heat treatment method adopted by the present invention consists of two parts: water cooling after rolling and solution treatment. The present invention designs the nickel-chromium-iron-based alloy to be single-phase austenite without phase change process. Since 450°C to 850°C is the sensitization temperature, and 650°C is the most dangerous among the sensitization temperatures, the speed should be fast during the solution treatment cooling stage, and the sensitization temperature zone should be avoided as much as possible. During the heating or cooling process, the shorter the residence time in the sensitization temperature zone, the smaller the chance of intergranular corrosion. Therefore, in the two stages of heating and cooling of the solution treatment, increasing the heating and cooling speed is an effective measure to improve the resistance to intergranular corrosion. By water cooling after rolling, the cooling rate is increased, the grains are effectively refined, the uniformity of the organization is guaranteed, and the material sensitization interval is avoided, thereby improving production efficiency. The water-cooled structure after rolling is rapidly heated to high-temperature solid solution at 1160~1200℃. Since the raw material contains 0.40-0.90% Nb, the precipitation temperature of NbN is higher than that of NbC. By ensuring the N content, the combination of C and Nb is reduced, the inclusions are reduced, the precipitation of carbides on the grain boundaries is reduced, the formation of Cr carbides is reduced, the occurrence of grain boundary chromium depletion is avoided, the intergranular corrosion resistance is enhanced, and intergranular corrosion is prevented. At the same time, the grain size of the alloy material gradually increases with the increase of the solid solution temperature. When the solution is below 1200℃, due to the low solution temperature, the nucleation rate of recrystallization is much greater than the rate of grain growth. Therefore, the recrystallization nucleation process is dominant, and the carbides inside the alloy structure have not been fully dissolved. During the heating process of the material, they have a pinning effect on the grain boundaries and prevent the growth of grains. When the solution temperature reaches 1200℃ and above, the recrystallization nucleation process is basically completed, carbides begin to dissolve into the matrix in large quantities, and the recrystallized grains grow rapidly. Therefore, the average recrystallized grain size increases rapidly with the increase of solution temperature and the extension of holding time.

[0018] The nickel-chromium-iron-based alloy production process of the present invention is used to manufacture a nickel-chromium-iron-based alloy steel plate with an average grain size of 4.5 and an austenite microstructure according to ASTM E112 standard. The mechanical properties tested according to the standard meet the following requirements: room temperature yield strength>473MPa, tensile strength>818Mpa, high temperature yield strength>327MPa, tensile strength>580Mpa, elongation (A)>54%, section shrinkage>63%, and an average corrosion rate of 0.045mm / year. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the implementation case of the Ni-Cr-Fe alloy steel ingot rolling process roadmap; Figure 2 This is a microstructure photograph of the nickel-chromium-iron based alloy steel plate in the implementation case. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0021] like Figure 1As shown in the figure, the steel ingot is taken out of the furnace and rolled after the high-temperature insulation is completed. The rolling method is high-temperature, large-reduction, multi-fire rolling. The reduction of each fire is 70~250mm. It is fully plastically deformed through four fires to obtain good mechanical properties.

[0022] A direct rolling process of N08120 corrosion-resistant high-temperature alloy steel ingot: the size of the rolled steel plate is: 68×2050×6800mm, such as Figure 2 As shown. Arc furnace smelting → AOD refining → LF refining → die casting → surface cleaning → heating → first fire rolling → cutting off the riser → surface cleaning → second fire rolling → third fire rolling → forming rolling → water cooling → surface cleaning → solution heat treatment → pickling; the smelted steel ingot is 13.8t steel ingot, and the rolling process is high temperature, large pressure, multi-fire rolling, and the reduction of each fire is 70~250mm; the solution heat treatment temperature is 1160~1200℃, and the solution time is 200~300 minutes. The specific steps are as follows: The first step is chemical composition design, which is to carry out batch smelting according to the following alloy chemical composition, and the direct rolling process of nickel-chromium-iron based alloy steel ingots, which is characterized in that the chemical composition design must meet the following element requirements by mass percentage: C:0.05-0.08%; Si:0.25-0.45%; Mn:0.55-0.80%; P≤0.025%; S≤0.005%; Cr:24.5-26.0%; Ni:36.0-37.5%; Cu≤0.30%; Nb:0.55-0.65%; Mo:0.10-1.0%; Residual elements: W≤2.5%; B≤0.010%; Al≤0.10%; Ti≤0.10%; [N]0.15-0.60%; the balance is Fe and unavoidable impurities.

[0023] The second step is electric arc furnace smelting, which includes adding primary material (7000kg of 8120 return material), secondary material (4000kg of 8120 return material), adding tertiary material (2400kg of 8120 return material), adding alloy (400kg of metallic chromium, 470kg of electrolytic nickel), temperature measurement, argon blowing and stirring, and tapping molten steel; The third step is AOD refining. The AOD refining steps include argon blowing throughout the process, receiving molten steel (according to O:Ar=4:1, O:Ar=1:1, O:Ar=1:3), oxygen and nitrogen blowing, one-stage temperature reduction (adding 520kg of electrolytic nickel, 300kg of lime, 300kg of metallic chromium, 8 aluminum ingots, and 100kg of industrial silicon), two-stage temperature reduction (adding 200kg of lime, 10 aluminum ingots, 604kg of electrolytic nickel, 200kg of metallic chromium, and 7kg of cobalt), three-stage temperature reduction (adding 400kg of lime, 2 aluminum ingots, 40Kg of electrolytic nickel, 200kg of metallic chromium, 15kg of industrial silicon, and 10kg of electrolytic manganese), and steel tapping.

[0024] The fourth step is LF refining, which includes heating, reducing, adding 120kg of lime, 15kg of calcium silicon powder, 4kg of ferroboron, and tapping; The fifth step is mold casting. The LF refined molten steel is hoisted to the mold casting station for ingot pouring. The pouring temperature is 1540-1550℃. The pouring speed is strictly controlled during pouring to ensure that the molten steel rises steadily in the mold, the liquid surface is not shiny, there is no crack in the middle, there is no flower around the mold, and the molten steel flows continuously. When the liquid level rises to the riser for more than 60 minutes, the flow is appropriately reduced and replenished. Argon protection is used throughout the pouring process to prevent secondary oxidation of the molten steel; The sixth step is surface cleaning, grinding and cleaning the surface defects of the obtained steel ingot.

[0025] The seventh step is pre-rolling heating. The furnace is loaded at room temperature before rolling and heated by a stepping furnace. Heating is required before each rolling. Lubricant is applied to the surface before heating to prevent uneven deformation and surface cracks. The final heating temperature is 1250°C and the holding time is 150-390min. The holding time is adjusted according to the thickness of the steel plate. The holding time is: t=X×(0.6~0.8)+90, where t is the holding time, unit: min; X is the effective thickness, unit: mm; 0.6~0.8 is the heating experience coefficient, unit: min / mm; the heating process ensures a reducing atmosphere, and the residual oxygen content in the furnace is 2.5-4.0%.

[0026] The eighth step is one-pass rolling, which is horizontal rolling, multi-pass rolling, and the reduction is 200~250mm; The ninth step is to remove the riser. The riser is removed at the riser end of the rolled ingot. 200mm is removed in the length direction to eliminate the looseness and shrinkage defects at the riser end to prevent the surface quality of the next rolling plate from being affected. The tenth step is the second-pass rolling, which is horizontal rolling, single heating, multi-pass rolling, and a reduction of 60~70mm; The eleventh step is three-pass rolling, which is longitudinal rolling, single heating, multi-pass rolling, and a reduction of 60~70mm; The twelfth step is forming rolling, which is longitudinal rolling, using single heating, multiple rolling passes, and a reduction of 50~60mm.

[0027] The thirteenth step is solution heat treatment, the solution temperature is 1160~1200℃, the solution time is 200~300 minutes, after solution treatment, it is water cooled to room temperature, and then pickled and trimmed to obtain the finished nickel-chromium-iron alloy steel plate.

[0028] The obtained nickel-chromium-iron alloy steel plate was tested for performance, and the results were as follows: the average grain size was 4.5. Figure 2 As shown, the room temperature structure is austenite.

[0029] Table 1 Mechanical properties test results of nickel-chromium-iron alloy steel plates in the implementation case Table 2 Implementation case nickel-chromium-iron alloy steel plate corrosion test results As shown in Table 1, the room temperature yield strength is 473MPa, the room temperature tensile strength is 818Mpa, the high temperature yield strength is 327MPa, and the high temperature tensile strength is 580Mpa. As shown in Table 2, the average corrosion rate is 0.046mm / year. The test data all meet the standard requirements.

[0030] The present invention obtains a steel plate with excellent comprehensive performance by adopting reasonable smelting, rolling and heat treatment processes on the basis of optimized composition, and develops a short-process production process of nickel-chromium-iron-based alloy plates. Compared with traditional casting, forging and rolling or continuous casting and rolling processes, it not only improves production efficiency and reduces production costs, but also can obtain better product performance.

[0031] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for producing a nickel-chromium-iron-based alloy plate, the requirements for the mass percentage of the chemical composition elements of the plate are: C: 0.05-0.08%; Si: 0.25-0.45%; Mn: 0.55-0.80%; P≤0.025%; S≤0.005%; Cr: 24.5-26.0%; Ni: 36.0-37.5%; Cu≤0.30%; Nb: 0.55-0.65%; Mo: 0.10-1.0%; residual elements W≤2.5%; B≤0.010%; Al≤0.10%; Ti≤0.10%; [N]0.15-0.60%; the balance is Fe and unavoidable impurities; The process flow is as follows: electric arc furnace smelting → AOD refining → LF refining → die casting → surface cleaning → heating → first-fire rolling → cutting off the riser → surface cleaning → second-fire rolling → third-fire rolling → forming rolling → water cooling → surface cleaning → solution heat treatment → pickling; die casting is a steel ingot, and the rolling process is high-temperature, high-pressure, multi-fire rolling, with a reduction of 50~250mm per fire; the solution heat treatment temperature is 1160~1200℃, and the solution time is 200~300 minutes.

2. The method for producing the nickel-chromium-iron-based alloy sheet according to claim 1, characterized in that: The electric arc furnace smelting steps include adding primary material 8120 return material 7000kg, adding secondary material 8120 return material 4000kg, adding tertiary material 8120 return material 2400kg, adding metallic chromium 400kg, adding electrolytic nickel 470kg, temperature measurement, argon blowing and stirring, and tapping molten steel.

3. The method for producing the nickel-chromium-iron-based alloy sheet material according to claim 1, characterized in that: The AOD refining steps include blowing argon throughout the process; receiving molten steel according to O:Ar=4:1, O:Ar=1:1, O:Ar=1:3; blowing oxygen and nitrogen; During the first temperature reduction process, 520kg of electrolytic nickel, 300kg of lime, 300kg of metallic chromium, 8 aluminum ingots and 100kg of industrial silicon are added; during the second temperature reduction process, 200kg of lime, 10 aluminum ingots, 604kg of electrolytic nickel, 200kg of metallic chromium and 7kg of cobalt are added; during the third temperature reduction process, 400kg of lime, 2 aluminum ingots, 40kg of electrolytic nickel, 200kg of metallic chromium, 15kg of industrial silicon and 10kg of electrolytic manganese are added; and steel is tapped.

4. The method for producing the nickel-chromium-iron-based alloy sheet material according to claim 1, characterized in that: The LF refining steps include heating, reducing, adding 120kg lime, 15kg calcium silicate powder, adding 4kg ferroboron, and tapping.

5. The method for producing the nickel-chromium-iron-based alloy sheet material according to claim 1, characterized in that: The heating before rolling is room temperature loading, and the stepping furnace is used for heating. Heating is required before each rolling. Lubricant is applied to the surface before heating to prevent uneven deformation and surface cracks. The final heating temperature is 1250℃, and the holding time is 150-390min. The holding time is adjusted according to the thickness of the steel plate. The holding time is: t=X×(0.6~0.8)+90, where t is the holding time, unit: min; X is the effective thickness, unit: mm; 0.6~0.8 is the heating experience coefficient, unit: min / mm; the reducing atmosphere is maintained during the heating process, and the residual oxygen content in the furnace is 2.5-4.0%; The first heat rolling is horizontal rolling, using single heating, multi-pass rolling, and a reduction of 200-250mm; The riser removal is to remove 200mm of the riser end of the rolled steel ingot in the length direction to eliminate the looseness and shrinkage defects of the riser end; The second heat rolling is horizontal rolling, using single heating, multi-pass rolling, and a reduction of 60-70 mm; The three-pass rolling is longitudinal rolling, using single heating, multiple-pass rolling, and a reduction of 60-70 mm; The forming rolling is longitudinal rolling, using single heating, multiple rolling passes, and a reduction of 50 to 60 mm.

6. The method for producing the nickel-chromium-iron-based alloy sheet material according to claim 1, characterized in that: The solution heat treatment temperature is 1160-1200°C, the solution time is 200-300 minutes, and after solution, the steel is cooled to room temperature by water, and then pickled and trimmed to obtain a nickel-chromium-iron alloy steel plate product.

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