Manufacturing process of corrosion-resistant high-temperature alloy forge piece

Abstract

The invention discloses a manufacturing process of a corrosion-resistant high-temperature alloy forge piece. The forge piece is composed of the following chemical components in percentage by weight: 0.03-0.08% of C; 0.15% to 0.50% of Si; 0.50 to 0.90 percent of Mn; less than or equal to 0.025% of P; s < = 0.008%; cr: 24.0 to 25.5%; ni: 37.5% to 38.50%; 0.30% or less of Cu; 0.50% to 0.70% of Nb; 0.10 to 1.0 part of Mo; a residual element W < = 2.5%; less than or equal to 0.010% of B; al < = 0.25%; 0.10% or less of Ti; 0.15% to 0.60% of [N]; the average grain size of the steel plate is grade 3, the room-temperature yield strength is 406 MPa, the tensile strength is 741 MPa, the high-temperature yield strength is 177 MPa, the tensile strength is 507 MPa, and the average corrosion rate is 0.035 mm / year. The manufacturing method comprises the following steps of material inspection, surface machining, blanking, primary heating, primary forging, secondary heating, forging forming, water cooling after forging and solid solution heat treatment. The initial shape of a blanked blank is square, one-time forging is two-time upsetting and two-time drawing, and the upsetting deformation is 30-50%; the solid solution heat treatment temperature is 1220-1260 DEG C, and the solid solution time is 300-600 minutes. On the basis of optimizing the components, the forging with excellent comprehensive performance is obtained by formulating reasonable forging and heat treatment processes.

Description

Technical Field

[0001] The invention belongs to the technical field of steel material processing technology, and specifically relates to the manufacture of corrosion-resistant high-temperature alloy forgings. Background Art

[0002] As petrochemical and coal resources are increasingly depleted, the world is paying more and more attention to the development of the new energy industry. Solar energy is a new energy product that countries around the world are competing to develop, and it is an effective way to achieve the "dual carbon goal". High-purity polysilicon is the basic raw material for solar photovoltaic and electronic industries, and is the main raw material for the development of 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. Usually, solid solution-strengthened corrosion-resistant high-temperature alloys are used. 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, the products involve rods, flange forgings, pipes, plates, etc., which are 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 design structure strength. However, due to the late start of manufacturing in China, it is difficult to produce forgings with excellent comprehensive performance. Summary of the invention

[0003] In order to overcome the defects of the prior art, the present invention obtains forgings with excellent comprehensive performance by formulating reasonable forging and heat treatment processes on the basis of optimizing the components. The average grain size is level 3, the room temperature yield strength is 406MPa, the tensile strength is 741Mpa, the high temperature yield strength is 177MPa, the tensile strength is 507Mpa, and the average corrosion rate is 0.035mm / year.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: The present invention provides a manufacturing process of a corrosion-resistant high-temperature alloy forging. The chemical composition of the corrosion-resistant high-temperature alloy is within the standard range of alloy steel. The composition is screened according to the performance requirements of the reactor and comprises the following components in weight percentage: C:0.03-0.08%;Si:0.15-0.50%;Mn:0.50-0.90%;P≤0.025%;S≤0.008%; Cr:24.0-25.5%;Ni:37.5-38.50%;Cu≤0.30%;Nb:0.50-0.70%;Mo:0.10-1.0;Residual elements W≤2.5%;B≤0.010%;Al≤0.25%;Ti≤0.10%;[N]0.15-0.60%;The balance is Fe and unavoidable impurities.

[0005] The forgings of the present invention adopt the optimized raw material composition to make the manufactured forgings have excellent comprehensive performance. The raw materials contain 0.40-0.90% 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 of grain boundaries is avoided, the intergranular corrosion resistance is enhanced, and intergranular corrosion is prevented. At the same time, Ni3Nb has the effect of pinning the grain boundaries below 1155°C, and has a better solid solution effect above 1220°C; Cr: 24.0-25.5% increases the anti-intergranular corrosion time in the high sensitization range; Cu≤0.30% can improve strength and toughness, especially atmospheric corrosion performance, and has a solid solution strengthening effect, improving the strength of high chromium and high chromium nickel steel without reducing plasticity; aluminum≤0.25% ensures sufficient deoxidation, and can refine the grains and improve impact toughness, but it will affect the hot processing performance, welding performance and cutting performance of steel, and its content needs to be strictly controlled.

[0006] The manufacturing process of the above-mentioned corrosion-resistant high-temperature alloy forgings includes the following steps: material inspection → surface processing → blanking → primary heating → primary forging → secondary heating → forging → water cooling after forging → solution heat treatment; the initial shape of the blank is square, the primary forging is two upsetting and two drawing, the upsetting deformation is 30-50%, and the forging method is drawing.

[0007] The electroslag blank is purchased according to the composition, and the material is inspected, and the surface defects are removed by grinding and then the blank is sawed; the obtained square blank is heated and forged to obtain a corrosion-resistant high-temperature alloy forging; the forging blank is subjected to solution heat treatment to obtain a finished corrosion-resistant high-temperature alloy forging.

[0008] Since 450℃~850℃ is the sensitization temperature range of austenitic stainless steel, staying in this temperature range for a long time will cause chromium carbide to precipitate from the intergranular space, resulting in intergranular chromium deficiency and increasing the intergranular corrosion tendency of the material. Among the sensitization temperatures, 650℃ is the most dangerous, so during the solution treatment cooling stage, the speed should be fast and the sensitization temperature zone should be avoided as much as possible. During the heating or cooling process, the shorter the stay time in the sensitization temperature zone, the smaller the chance of intergranular corrosion. Therefore, in the heating and cooling stages of solution treatment, increasing the heating temperature and cooling rate is an effective measure to improve the intergranular corrosion resistance.

[0009] The solution heat treatment temperature is 1220-1260° C., the solution time is 300-600 minutes, and the solution is cooled to room temperature by water.

[0010] The primary heating temperature is 1220° C., the heating time is 150 to 180 minutes, and the secondary heating temperature is 1200° C., the heating time is 120 to 150 minutes.

[0011] Furthermore, the forging forming includes heating before forging, two upsetting and two drawing, forging forming, and water cooling treatment after forging.

[0012] Preferably, the heating before forging is to heat the billet in a furnace at high temperature, with a holding temperature of 1220°C and a holding time of 150 to 180 minutes, so that the billet is axially upset in a hot state, and the cast structure is broken by utilizing sufficient upsetting deformation; the tooling is preheated to 300°C before forging to prevent the high-temperature billet from directly contacting and transferring heat with the cold tooling, resulting in rapid cooling of the billet, and the risk of cracking during the forging process.

[0013] The two-upsetting and two-drawing process is to subject the blank to two axial upsetting and radial drawing processes, and to subject the blank to sufficient plastic deformation in the longitudinal and axial directions in the main deformation forging stage to break the cast grains to obtain good mechanical properties. There are two fires in total, the forging temperature of the first fire is 950-1220°C, the temperature of the forging molding fire is 950-1200°C, the chamfering is performed in time during the forging process to prevent cracking, and the forging ratio is greater than 5; and a corrosion-resistant high-temperature alloy forging blank is obtained.

[0014] Furthermore, the forging heating time is: t=X×(0.6~0.8)+90 min, where t is the heating time, unit: min; X is the effective thickness of the billet, unit: mm; 0.6~0.8 is the material heating experience coefficient, unit min / mm.

[0015] The post-forging water cooling treatment is to water cool the forging blank after forging to room temperature.

[0016] The technical solution of the present invention has the following advantages: The forging production method adopted by the present invention can effectively control the mechanical properties of the corrosion-resistant high-temperature alloy designed by the present invention. After two upsetting and two drawing, the billet is sufficiently deformed to break the coarse cast dendrites, improve the compactness of the organization, and facilitate the effect of high-temperature diffusion, improve the unevenness of the chemical composition of the billet 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, and obtain excellent mechanical properties through fine grain strengthening.

[0017] The heat treatment method adopted by the present invention consists of two parts: water cooling after forging and solution treatment. The corrosion-resistant high-temperature alloy designed by the present invention is 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 cooling speed should be fast during the solution treatment 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 solution treatment, increasing the heating and cooling speeds is an effective measure to improve resistance to intergranular corrosion. By water cooling after forging, the cooling rate is increased, the grains are effectively refined, the uniformity of the structure is ensured, and the material sensitization interval is avoided, thereby improving production efficiency. The water-cooled structure after forging is rapidly heated to high-temperature solid solution at 1220~1260℃. 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, and the intergranular corrosion resistance is enhanced. At the same time, Ni3Nb has the effect of pinning grain boundaries below 1155℃, and has a better solid solution effect above 1220℃. Rapid water cooling after the insulation is completed can obtain excellent mechanical properties.

[0018] By using the technical solution of the present invention, the corrosion-resistant high-temperature alloy forgings manufactured are tested according to the ASTM E112 standard with an average grain size of 3 to 4, and the microstructure is austenite. According to the standard test, the mechanical properties meet the room temperature yield strength>406MPa, tensile strength>741Mpa, high temperature yield strength>177MPa, tensile strength>507Mpa, elongation (A)>52%, section shrinkage>63%, and average corrosion rate of 0.035mm / year, meeting the product technical requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the process roadmap for the implementation of the corrosion-resistant high-temperature alloy forging forming process; Figure 2 This is a microstructure photograph of the corrosion-resistant high-temperature alloy forgings used 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 1 As shown in the figure, the square billet is taken out of the furnace for forging after the high-temperature insulation is completed. The deformation method is two upsetting and two drawing. The upsetting deformation is 30~50%, and the single-side pressing amount is 20mm. Through the main deformation forging stage, sufficient plastic deformation is carried out in the longitudinal and axial directions to obtain good mechanical properties. Chamfering is performed in time during the forging process to prevent cracking.

[0022] A method for manufacturing a corrosion-resistant high-temperature alloy forging: The forging size is: Φ150×780mm, such as Figure 2 As shown. Material inspection → surface processing → blanking → primary heating → primary forging → secondary heating → forging → water cooling after forging → solution heat treatment; the blank blank has a square initial shape, the primary forging is two upsetting and two drawing, the upsetting deformation is 30~50%, and the forging method is drawing; the solution heat treatment temperature is 1220~1260℃, and the solution time is 300~600 minutes. The specific steps are as follows: The first step is material selection. The electroslag blank is selected according to the following alloy chemical composition. The method for preparing corrosion-resistant high-temperature alloy forgings is characterized in that the material inspection must meet the following element requirements in mass percentage: C:0.03-0.08%;Si:0.15-0.50%;Mn:0.50-0.90%;P≤0.025%;S≤0.008%; Cr:24.0-25.5%;Ni:37.5-38.50%;Cu≤0.30%;Nb:0.50-0.70%;Mo:0.10-1.0;Residual elements W≤2.5%;B≤0.010%;Al≤0.25%;Ti≤0.10%;[N]0.15-0.60%;The balance is Fe and unavoidable impurities.

[0023] The second step is material inspection and surface processing, which checks whether the material meets the requirements of SB-564 standard and processes the surface defects.

[0024] The third step is sawing and cutting. According to the product size, choose 220*220*430mm sawing square ingot.

[0025] The fourth step is one-time heating. The blank ingot is charged into the furnace for high-temperature heating. The furnace temperature is above 900℃. The one-time heating temperature is 1220℃. The heating time is 150~180 minutes. The heating time is: t=X×(0.6~0.8)+90 min, where t is the heating time, unit: min; X is the effective thickness of the billet, unit: mm; 0.6~0.8 is the material heating experience coefficient, unit is min / mm; the tooling is baked to 300℃ before forging.

[0026] The fifth step is one-time forging, such as Figure 1, one forging is two upsetting and two drawing, two axial upsetting and radial drawing are performed, and sufficient plastic deformation is performed in the longitudinal and axial directions through the main deformation forging stage to obtain good mechanical properties. There are 2 fires in total, the forging temperature of the first fire is 1220-950℃, and the forging temperature of the second fire is 1200-950℃. The chamfering is timely during the forging process, the upsetting deformation is 30~50%, the forging ratio is greater than 5, and the relationship between the final cross-sectional thickness H and the width B satisfies 1.1≤B / H≤2.0. The corrosion-resistant high-temperature alloy forging billet is obtained.

[0027] The sixth step is secondary heating, the secondary heating temperature is 1200℃, and the heating time is 120~150 minutes, to ensure that the forging is carried out in accordance with the final corrosion-resistant high-temperature alloy forging size requirements in the hot state.

[0028] The seventh step is water cooling after forging. Water cooling is carried out in time after forging. By increasing the cooling rate, the grains are effectively refined, the uniformity of the organization is ensured, and the sensitization zone of the material is avoided.

[0029] The eighth step is solution heat treatment, the solution temperature is 1220-1260°C, and the solution time is 300-600 minutes. In order to make all the alloy elements in the corrosion-resistant high-temperature alloy further fully dissolved, the forging blank is loaded into the furnace at room temperature before solution treatment. After loading into the furnace, it is heated to 1220-1260°C at a rate of ≤100°C / h for solution heat treatment. After the insulation is completed, it is cooled to room temperature.

[0030] The corrosion-resistant high-temperature alloy forgings obtained in the example were tested for performance, and the results showed that the average grain size was grade 3, and the room temperature structure was austenite. Figure 2 The room temperature yield strength is 406MPa, the tensile strength is 741Mpa, the high temperature yield strength is 177MPa, and the tensile strength is 507Mpa, as shown in Table 1; the average corrosion rate is 0.035mm / year, as shown in Table 2, all of which meet the standard requirements.

[0031] Table 1 Mechanical properties test results of corrosion-resistant high-temperature alloy forgings in the implementation case

[0032] Table 2 Corrosion test results of corrosion-resistant high-temperature alloy forgings in the implementation case .

[0033] 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 manufacturing process for corrosion-resistant high-temperature alloy forgings, characterized in that Material inspection must meet the following element requirements in terms of mass percentage: C:0.03-0.08%;Si:0.15-0.50%;Mn:0.50-0.90%;P≤0.025%;S≤0.008%;Cr:24.0-25.5%; Ni: 37.5-38.50%; Cu≤0.30%; Nb: 0.50-0.70%; Mo: 0.10-1.0; Residual element Al≤0.25%; Ti≤0.10%; [N]0.15-0.60%; the balance is Fe and unavoidable impurities; The invention is characterized in that the process flow is as follows: material inspection → surface processing → blanking → primary heating → primary forging → secondary heating → forging → water cooling after forging → solution heat treatment; the initial shape of the blank is square, the primary forging is two upsetting and two drawing, the upsetting deformation is 30-50%, and the forging method is drawing; the solution heat treatment temperature is 1220-1260°C, and the solution time is 300-600 minutes.

2. The manufacturing process of a corrosion-resistant high-temperature alloy forging according to claim 1, characterized in that: Before cutting, the defects on the surface of the raw materials need to be processed and removed by grinding.

3. The manufacturing process of a corrosion-resistant high-temperature alloy forging according to claim 1, characterized in that: The main deformation forging stage of a forging process requires sufficient plastic deformation in the longitudinal and axial directions. The blank is subjected to two axial upsetting and radial drawing. The tooling needs to be preheated at 300°C before forging. There are two fires in total. The forging temperature of the first fire is 950-1220°C, and the forging temperature of the second fire is 950-1200°C. The edges are chamfered in time during the forging process. The relationship between the final cross-sectional thickness H and the width B satisfies 1.1≤B / H≤2.0, and the forging ratio is controlled above 5 to obtain a forging blank.

4. The manufacturing process of a corrosion-resistant high-temperature alloy forging according to claim 1, characterized in that: The primary heating temperature is 1220° C., the heating time is 150 to 180 minutes, and the secondary heating temperature is 1200° C., the heating time is 120 to 150 minutes.

5. The manufacturing process of a corrosion-resistant high-temperature alloy forging according to claim 4, characterized in that: During primary heating, the furnace is directly loaded when the furnace temperature is above 900℃. The heating time is calculated as follows: t=X×(0.6~0.8)+90min, where t is the heating time, unit: min; X is the effective thickness of the billet, unit: mm; 0.6~0.8 is the material heating experience coefficient, unit: min / mm, and the tooling is baked to 300℃ before forging.

6. The manufacturing process of a corrosion-resistant high-temperature alloy forging according to claim 1, characterized in that: After solution treatment, the product is cooled to room temperature with water to obtain a corrosion-resistant high-temperature alloy forging.

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