Creep-resistant main body forge piece of hydrogenation reactor with thick-wall forge welding structure and manufacturing method of creep-resistant main body forge piece

Abstract

The invention relates to a thick-wall forge-welded structure hydrogenation reactor creep-resistant main body forge piece and a manufacturing method, belongs to the technical field of metal materials, and solves the problems of insufficient high-temperature durability and hardenability of hydrogenation reactor main body forge pieces in the prior art. The invention relates to a thick-wall forge welding structure hydrogenation reactor creep-resistant main body forge piece. The forge piece material comprises the following chemical components in percentage by mass: 0.14-0.16% of C, less than or equal to 0.1% of Si, 0.3-0.6% of Mn, less than or equal to 0.005% of P, less than or equal to 0.002% of S, 1.90-2.20% of Cr, 0.9-1.1% of Mo, less than or equal to 0.2% of Ni, less than or equal to 0.2% of Cu, less than or equal to 0.05% of Nb, 0.25-0.35% of V, less than or equal to 0.03% of Ti, less than or equal to 0.04% of Al, 0.0010-0.0025% of B, less than or equal to 0.004% of Sb, less than or equal to 0.01% of Sn, less than or equal to 0.01% of As And the high-temperature creep durability and hardenability of the thick-wall forge piece are improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal materials, and in particular to a thick-wall forged-welded structure hydrogenation reactor creep-resistant main body forging and a manufacturing method thereof. Background Art

[0002] As the main reaction device in oil refining, the hydrogenation reactor is a key component of oil refining equipment. The quality of its manufacturing process determines the technical level of the petrochemical industry and its international status.

[0003] At present, hydrogenation reactor vanadium steel with 2.25Cr-1Mo-0.25V as the base material has been widely used at home and abroad. ASME standards and technical documents have included high temperature performance research into mandatory clauses, requiring that the welded joints should have a sustained fracture time of not less than 900 hours under 540℃ and 210MPa conditions after simulated post-weld heat treatment at 705℃×8h. In recent years, petrochemical containers have developed towards large-scale, harsh media, and extreme service temperatures, which has put forward higher requirements on the hardenability, durability, and sustained fracture time of petrochemical container materials at high temperatures.

[0004] At present, most domestic manufacturers increase the wall thickness to improve the high-temperature durability and safety redundancy of the main material of the hydrogenation reactor 2.25Cr-1Mo-0.25V, but this can easily lead to insufficient hardenability, increase production costs, and bring difficulties to manufacturing. Summary of the invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide a thick-walled forged-welded structure hydrogenation reactor creep-resistant main forging and a manufacturing method, so as to solve the problems of insufficient high-temperature durability and hardenability of the existing hydrogenation reactor main forgings.

[0006] On the one hand, an embodiment of the present invention provides a creep-resistant main forging of a thick-walled forged welded structure hydrogenation reactor, wherein the chemical composition and mass percentage of the forging material are: C: 0.14% to 0.16%, Si: ≤0.1%, Mn: 0.3% to 0.6%, P≤0.005%, S≤0.002%, Cr: 1.90% to 2.20%, Mo: 0.9% to 1.1%, Ni: ≤0.2%, Cu: ≤0.2%, Nb: ≤0.05%, V: 0.25% to 0.35%, Ti≤0.03%, Al≤0.04%, B: 0.0010% to 0.0025%, Sb≤0.004%, Sn≤0.01%, As≤0.01%, O≤0.003%, N≤0.007%, H≤0.0001%, and the remaining components are Fe and unavoidable impurities.

[0007] Preferably, the chemical composition and mass percentage of the forging material are: C: 0.14% to 0.16%, Si: ≤0.1%, Mn: 0.3% to 0.6%, P≤0.005%, S≤0.002%, Cr: 1.90% to 2.20%, Mo: 0.9% to 1.1%, Ni: ≤0.2%, Cu: ≤0.2%, Nb: ≤0.05%, V: 0.25% to 0.32%, Ti≤0.03%, Al≤0.04%, B: 0.0015% to 0.0025%, Sb≤0.004%, Sn≤0.01%, As≤0.01%, O≤0.003%, N≤0.007%, H≤0.0001%, and the remaining components are Fe and unavoidable impurities.

[0008] On the other hand, an embodiment of the present invention provides a method for preparing a creep-resistant main forging of a thick-walled forged-welded structure hydrogenation reactor, which is used to prepare the forging, including steel ingot smelting-forging-post-forging heat treatment-performance heat treatment.

[0009] Specifically, the smelting process includes basic electric furnace rough refining+vacuum carbon deoxidation refining+vacuum pouring ingot casting.

[0010] It should be noted that after the alkaline electric furnace rough refining, the residual elements are required to meet P≤0.001%, S≤0.01% when tapping, and the temper embrittlement sensitivity coefficient J=(Si+Mn)×(P+Sn)×10 4 ≤60, P+Sn≤0.012%, elements are introduced in mass percentage.

[0011] Furthermore, the forging process adopts a forging process combining upsetting, drawing and hole expansion.

[0012] Preferably, the ratio of the upsetting ratio to the drawing ratio in the forging process is in the range of 0.92 to 1.08, and the main section forging ratio is greater than 3.5.

[0013] It should be noted that the initial forging temperature is strictly controlled in the forging process, which is controlled at 1200-1250°C, and the final forging temperature is not lower than 850°C.

[0014] Furthermore, the post-forging heat treatment adopts annealing at 920-960°C.

[0015] Furthermore, the performance heat treatment adopts quenching at 960-980°C and tempering at 680-720°C.

[0016] Specifically, the quenching in the performance heat treatment process adopts water quenching, and the water temperature is not higher than 18°C.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0018] 1. The present invention optimizes the material composition of the creep-resistant main forging. While keeping the carbon content unchanged, the V content is increased, the number of MX carbides is increased, the "pinning" effect on dislocations is increased, and the long-term creep endurance performance is maintained without degradation; the Cr content is appropriately reduced within the technical specifications, the number of large-particle carbides is reduced, and the damage to the creep endurance performance is reduced; after optimizing the Cr and V element contents, the B element is added and a relatively high B element content is maintained, so as to achieve a significant improvement in the creep endurance performance of the forging and enhance the hardenability of the thick-walled forging, while almost not affecting the conventional mechanical properties of the forging.

[0019] 2. The present invention adopts a smelting process of alkaline electric furnace smelting + vacuum carbon deoxidation refining + vacuum pouring for the steel ingot; the composition of the charge is strictly controlled during the smelting process, and high-quality pig iron and scrap steel containing harmful elements such as S and P and low levels of As, Sn, Sb are used as smelting materials to control the content of impurity elements and reduce the temper brittleness sensitivity coefficient; high-basicity slag is used to remove P and S during the rough smelting process in the alkaline electric furnace to ensure that J = (Si + Mn) × (P + Sn) × 10 4 ≤60, P+Sn≤0.012%, effectively preventing the segregation of harmful elements at the grain boundaries and the formation of low-melting point compounds during long-term creep and durability; through vacuum carbon deoxidation refining, using carbon-oxygen reaction, further reducing the O, N, H content in the steel, using good reducing slag, reducing the S content to a minimum, and further removing P; using vacuum pouring, through oxygen-carbon reaction under vacuum, further reducing the oxygen content, hydrogen content and inclusions in the molten steel, further purifying the molten steel, effectively reducing the gas content, reducing the number of inclusions, reducing the formation of defects such as pores and inclusions, eliminating the source of stress concentration at high temperature, which is beneficial to improving the high-temperature creep and durability performance.

[0020] 3. The present invention adopts a forging process combining upsetting, drawing and hole expansion to remove the central segregation and enriched inclusions of large steel ingots by hole expansion; controls the main section forging ratio to be greater than 3.5, adopts a large deformation amount and strict initial and final forging temperature control to obtain a uniform and fine structure, and effectively improves the creep durability of the main forging.

[0021] 4. The present invention adopts a process combining post-forging heat treatment with performance heat treatment, wherein the post-forging heat treatment adopts annealing process for slow cooling, which is beneficial to the full transformation of austenite structure, thereby refining the grains; the performance heat treatment determines a reasonable heating temperature, increases the cooling rate, improves the hardenability, obtains more upper bainite, and is beneficial to improving the creep endurance performance.

[0022] 5. After the forgings obtained by using the alloy chemical composition and preparation method of the present invention are subjected to simulated post-weld heat treatment at 705°C×32h, the sustained fracture time under the conditions of 540°C and 210MPa is ≥900hr.

[0023] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0025] Figure 1 This is a process diagram of heat treatment after forging of the present invention;

[0026] Figure 2 This is the performance heat treatment process diagram of the present invention;

[0027] Figure 3 1 and 2 are CCT curves of Example 1 and Comparative Example 1 of the present invention; wherein (a) is the CCT curve of Comparative Example 1, and (b) is the CCT curve of Example 1. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0029] On the one hand, a specific embodiment of the present invention discloses a creep-resistant main forging of a thick-walled forged-welded structure hydrogenation reactor, wherein the chemical composition and mass percentage of the forging material are: C: 0.14% to 0.16%, Si: ≤0.1%, Mn: 0.3% to 0.6%, P≤0.005%, S≤0.002%, Cr: 1.90% to 2.20%, Mo: 0.9% to 1.1%, Ni: ≤0.2%, Cu: ≤0.2%, Nb: ≤0.05%, V: 0.25% to 0.35%, Ti≤0.03%, Al≤0.04%, B: 0.0010% to 0.0025%, Sb≤0.004%, Sn≤0.01%, As≤0.01%, O≤0.003%, N≤0.007%, H≤0.0001%, and the remaining components are Fe and unavoidable impurities.

[0030] The present invention improves the creep durability of forgings and enhances the hardenability of thick-wall forgings by optimizing the chemical composition of the material. The reasons for limiting the composition are explained below:

[0031] C: C is to ensure that there is a sufficient amount of carbides combined with alloy elements in the metal material structure. The C content determines the total amount of carbides to a certain extent, thereby ensuring the room temperature and high temperature strength, creep rupture strength and toughness of the material. The C content in the material of the present invention is 0.14-0.16%.

[0032] Si: Si has a strong effect in steelmaking, but Si can increase embrittlement sensitivity and is a strong element that promotes temper brittleness. Therefore, the Si content should be as low as possible, generally controlled below 0.1%.

[0033] Mn: Mn plays a deoxidizing role in steelmaking and has a solid solution strengthening effect in the structure. However, Mn promotes the segregation of P at the original austenite grain boundary, reducing the bonding strength of the grain boundary. Due to the interaction between Mn and P, Sb, As, and Sn, the increase of Mn content in steel will aggravate the temper embrittlement of steel. The Mn content in the material of the present invention is controlled at 0.3-0.6%.

[0034] Mo: Mo is a strengthening element that can improve the room temperature strength and creep rupture strength of the material. In addition, Mo can delay the segregation of impurity elements and reduce the occurrence of temper brittleness. In the present invention, the Mo content is controlled at 0.9% to 1.1%.

[0035] Ni: Ni is not easy to form carbides, which can improve the low-temperature toughness of the material, but also reduce the creep rupture strength. The Ni content is controlled below 0.2%.

[0036] Nb: It is a strong carbide-forming element. It can refine the structure and combine with V and Ti to form composite carbides, thus improving the room and high temperature strength and endurance strength. The Nb content is controlled below 0.05%.

[0037] Ti: Ti can reduce the content of N and O in steel, but excessive Ti is detrimental to toughness. The Ti content in the material is controlled below 0.03%.

[0038] V: V and C form fine, dispersed MX carbides, which are not easy to grow during the durability process, and can effectively "pin" dislocations to maintain durability. In addition, there is P element at the junction of MX carbides and the matrix, so V can change the distribution of P element, thereby affecting temper brittleness; the V content of the present invention is controlled at 0.25% to 0.35%.

[0039] Al: Al plays a deoxidizing role in steelmaking. In addition, Al and N form AlN, which can refine the grains. However, excessive Al content is prone to form inclusions. The Al content is controlled below 0.04%.

[0040] Cu: A certain amount of Cu can improve the strength and corrosion resistance of the matrix, but too high a Cu content is not good for impact resistance. In addition, as the Cu content increases, the embrittlement sensitivity increases. Therefore, the Cu content is controlled below 0.2%.

[0041] As, Sb, Sn: low melting point elements are harmful elements that tend to segregate at grain boundaries, reduce the binding energy of grain boundaries, thereby reducing the strength of grain boundaries and increasing temper brittleness. Therefore, the present invention controls Sn≤0.01%, As≤0.01%, and Sb≤0.004%.

[0042] Cr: Cr can improve the oxidation resistance and corrosion resistance of steel, and can improve the high temperature performance of steel. Cr-containing steel can have higher strength and comprehensive mechanical properties through heat treatment. However, Cr carbides tend to coarsen during the durability process, and a high content is not conducive to improving the durability of forgings. The Cr content is controlled at the lower limit of 1.90% to 2.20%.

[0043] B: B can be concentrated at the grain boundary, strengthen the grain boundary, improve the material hardenability and creep resistance at high temperature. The B content is controlled at 0.0010% to 0.0025%.

[0044] Preferably, the chemical composition and mass percentage of the forging material are: C: 0.14% to 0.16%, Si: ≤0.1%, Mn: 0.3% to 0.6%, P≤0.005%, S≤0.002%, Cr: 1.90% to 2.20%, Mo: 0.9% to 1.1%, Ni: ≤0.2%, Cu: ≤0.2%, Nb: ≤0.05%, V: 0.25% to 0.32%, Ti≤0.03%, Al≤0.04%, B: 0.0015% to 0.0025%, Sb≤0.004%, Sn≤0.01%, As≤0.01%, O≤0.003%, N≤0.007%, H≤0.0001%, and the remaining components are Fe and unavoidable impurities.

[0045] Specifically, after the forging is subjected to simulated post-weld heat treatment at 705° C.×32 h, the sustained fracture time of the forging is ≥900 hr under the conditions of 540° C. and 210 MPa.

[0046] On the other hand, a specific embodiment of the present invention discloses a method for preparing a thick-walled forged-welded structure hydrogenation reactor creep-resistant main forging, which is used to prepare the forging, including steel ingot smelting-forging-post-forging heat treatment-performance heat treatment.

[0047] Specifically, the smelting process includes basic electric furnace rough refining+vacuum carbon deoxidation refining+vacuum pouring ingot casting.

[0048] The composition of the charge must be strictly controlled during the smelting process. High-quality pig iron and scrap steel containing harmful elements such as S and P and low levels of As, Sn, and Sb should be used as smelting materials to control the content of impurity elements and reduce the temper brittleness sensitivity coefficient.

[0049] In a possible design, the smelting charge is 20% high-quality pig iron, 30% light scrap steel, and the rest is heavy scrap steel + steel chips to ensure that the temper brittleness sensitivity coefficient J factor and P+Sn can be controlled at a lower value.

[0050] It should be noted that after the alkaline electric furnace rough refining, the residual elements are required to meet P≤0.001%, S≤0.01% when tapping, and the temper embrittlement sensitivity coefficient J=(Si+Mn)×(P+Sn)×10 4 ≤60, P+Sn≤0.012%; the content of residual harmful elements such as S, P, Sn, Si in the steel is required to be low, otherwise the harmful elements are easy to form low-melting point compounds, reduce the high-temperature durability of the alloy and increase the sensitivity of temper embrittlement;

[0051] The alkaline electric furnace rough refining process uses high-basicity slag to remove P and S. The P content is reduced through large amounts of slag and multiple slag replacement operations. The rough steel liquid must be strictly slag-controlled before entering the refining process.

[0052] Furthermore, in the vacuum refining + vacuum pouring ingot casting process, the carbon-oxygen reaction is used under vacuum in the refining furnace to further reduce the O, N, and H contents in the steel, and the S content is reduced to a minimum by using good reducing slag, and P is further removed; during vacuum refining, diffusion deoxidation is used, C powder + Al powder, with C powder as the main component, to reduce inclusions after Al deoxidation, and argon blowing and stirring are performed during refining, and the soft blowing time for steel tapping is 20 to 40 minutes to promote the floating of inclusions and achieve the purpose of pure molten steel;

[0053] Vacuum pouring is used to further reduce the oxygen content, hydrogen content and inclusions in the molten steel through oxygen-carbon reaction under vacuum, and further purify the molten steel; during the pouring process, argon injection protection and argon replacement in the tundish are used to prevent secondary oxidation of the molten steel, reduce inclusions, and reduce damage to long-term performance.

[0054] Furthermore, the forging process adopts a forging process combining upsetting, drawing and hole expansion.

[0055] Specifically, the holding time of the heating section is increased to 48 hours before forging, and the alloy composition of the forging is made uniform through high-temperature diffusion; the water inlet and riser are gas-cut before forging, and the ingot is returned to the furnace after gas cutting to remove defective areas and ensure that the material is at an appropriate temperature before forging; punching is performed after upsetting, and the punch must be centered during punching to fully remove segregation and enriched inclusions in the center of the ingot, and the hole is expanded using a horse bar, and the finished product is rolled out on a barrel mill after expansion.

[0056] Preferably, the ratio of the upsetting ratio to the drawing ratio in the forging process is in the range of 0.92 to 1.08, such as 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, and the upsetting ratio is close to the drawing ratio, so that the anisotropy of the forging is minimized; to ensure the deformation degree of the forging, the main section forging ratio is greater than 3.5, which can ensure sufficient recrystallization of the forging.

[0057] In one possible design, the upset ratio is 2.5 and the draw ratio is 2.3.

[0058] It should be noted that the initial forging temperature is strictly controlled during the forging process, and the initial forging temperature is controlled at 1200-1250°C to prevent grain growth; the final forging temperature is not lower than 850°C to ensure that the forging obtains a uniform and fine grain structure, creating a good internal original structure for the subsequent heat treatment process.

[0059] Heat treatment is the last key process that determines the quality of forgings, including post-forging heat treatment and performance heat treatment. After forging, the forgings are air-cooled to 100-150°C and put into the furnace for annealing heat treatment. The purpose of annealing is to make the austenite structure uniform, refine the grains, further reduce the hydrogen content, reduce the forging stress, facilitate rough processing, and prepare for performance heat treatment. Performance heat treatment includes quenching and tempering, which mainly aims to obtain good comprehensive mechanical properties of forgings by reasonably selecting heating temperature, holding time, cooling rate and tempering parameters. Increasing the heating temperature is conducive to the full dissolution of carbides and the uniformity of alloy elements, which is conducive to improving the hardenability of thick-walled forgings. After heat treatment, the bainite in the metallographic structure must reach more than 90%.

[0060] Furthermore, the post-forging heat treatment adopts annealing at 920-960°C;

[0061] Specifically, the post-forging heat treatment process includes: air cooling the forgings to 100-150°C after forging and then putting them into the furnace, heating them to 300-350°C and keeping them warm, heating them to 920-960°C at a rate of ≤60°C / hr, keeping them warm for ≥1hr / 50mm, cooling them to 650°C at a rate of ≤10°C / hr and then sealing the furnace for cooling, and the forgings are cooled to below 450°C before being taken out of the furnace.

[0062] Furthermore, the performance heat treatment adopts quenching at 960-980°C and tempering at 680-720°C.

[0063] Specifically, the performance heat treatment process includes: after the forging is annealed, it is heated to 960-980℃ and kept at a temperature of ≥1hr / 50mm, then water quenched to 300-350℃, and then heated to 680-720℃ at a rate of ≤70℃ / hr and kept at a temperature of ≥1hr / 50mm, and then air-cooled.

[0064] Specifically, the performance heat treatment process adopts water quenching, the water temperature is not higher than 18°C, and the quenching water tank flow rate (≥6000 cubic meters / hour) must meet the requirements to ensure the hardenability of the forging.

[0065] It should be noted that during heat treatment, the uniformity of the furnace temperature of the heat treatment furnace must be ensured, the temperatures in each temperature zone of the electric furnace must be consistent, the gas furnace must be well sealed, and the furnace must be slightly positively pressurized during the high temperature stage to ensure uniform furnace temperature.

[0066] The present invention optimizes the material composition design, determines reasonable smelting process, forging and heat treatment process, controls the material structure, reduces harmful elements and oxide inclusions, ensures the material's durable performance, and thus meets various requirements of the service environment for hydrogenation main materials; the forgings obtained by using the alloy chemical composition and preparation method of the present invention have a durable fracture time of ≥900 hr under the conditions of 540°C and 210MPa after simulated post-weld heat treatment at 705°C×32h.

[0067] The chemical composition and preparation method of the creep resistant main forging material of the present invention are described below in conjunction with specific embodiments.

[0068] Embodiments 1 to 4

[0069] This embodiment discloses 1-4# thick-wall forged welded structure hydrogenation reactor creep resistant main forgings and a preparation method thereof. The main chemical components of the forgings are shown in Table 1, and the preparation method is as follows:

[0070] Step 1, smelting: adopting the steel ingot smelting process of basic electric furnace rough smelting + vacuum carbon deoxidation (VCD) refining + vacuum pouring;

[0071] (1) Selected charge: Use 20% high-quality pig iron, 30% light scrap steel, and the rest heavy scrap steel + steel chips as charge to ensure that the temper brittleness sensitivity coefficient J factor and P+Sn can be controlled at a lower value;

[0072] (2) Alkaline electric furnace smelting is used, and high basicity slag is used for P and S removal. A large amount of slag and multiple slag replacement operations are performed to reduce the P content. When tapping the steel in the electric furnace, P is required to be ≤ 0.001% and S is reduced to 0.01%. J = (Si + Mn) × (P + Sn) × 10 4 ≤60, P+Sn=0.009%, the contents of chemical elements of steel tapped from an electric furnace are shown in Table 2; the slag is strictly blocked before the crude steel enters the refining process;

[0073] (3) Vacuum refining + vacuum ingot casting: The carbon-oxygen reaction is used under vacuum in the refining furnace to further reduce the O in the steel, and the S content is minimized by using good reducing slag;

[0074] During refining, diffusion deoxidation is used, C powder + Al powder, with C powder as the main, to reduce inclusions after Al deoxidation. Argon blowing and stirring are carried out during refining, and the soft blowing time for steel tapping is 20 to 40 minutes to promote the floating of inclusions and achieve the purpose of pure molten steel;

[0075] Vacuum pouring is used to further reduce the oxygen content, hydrogen content and inclusions in the molten steel through oxygen-carbon reaction under vacuum, and the molten steel is further purified. During the pouring process, argon injection protection and argon replacement in the tundish are used to prevent secondary oxidation of the molten steel.

[0076] Step 2, forging: using upsetting, punching, drawing and expanding forging processes;

[0077] Before forging, the holding time of the heating section is increased, and the temperature is kept at 1250℃ for 48h. The specific temperature parameters of forging and heat treatment are shown in Table 3. The alloy composition of the forging is made uniform by high-temperature diffusion; the nozzle and riser are gas-cut before forging, and the steel is returned to the furnace after gas cutting; punching is performed after upsetting, and the punch should be centered during punching, so as to remove the segregation and enriched inclusions in the center of the ingot; during upsetting and drawing, the upsetting ratio is close to the drawing ratio, the upsetting ratio is 2.5, the drawing ratio is 2.3, and the main section forging ratio is greater than 3.5, so that the anisotropy of the forging is minimized;

[0078] The hole is expanded by a horse bar, and then the finished product is rolled out on a barrel rolling mill.

[0079] The initial forging temperature is strictly controlled during the forging process, which is controlled at 1200-1250℃ and the final forging temperature is not lower than 850℃, to ensure that the forgings obtain uniform and fine grain structure and create a good internal original structure for subsequent heat treatment process.

[0080] Step 3, heat treatment: including post-forging heat treatment and performance heat treatment. The specific temperature parameters of the heat treatment are shown in Table 3;

[0081] After forging, the forging is air-cooled to 100-150℃ and then put into the furnace for annealing heat treatment. The purpose of annealing is to make the austenite structure uniform, refine the grains, further reduce the hydrogen content, reduce the forging stress, facilitate rough machining, and prepare for performance heat treatment. The post-forging heat treatment process is as follows: Figure 1 ;

[0082] Performance heat treatment includes quenching and tempering. Performance heat treatment processes such as Figure 2 , CCT curve is as follows Figure 3 As shown in the figure, by reasonably selecting the holding temperature, holding time, cooling rate and tempering parameters, the forgings can obtain good comprehensive mechanical properties; in order to ensure the cooling rate and improve the hardenability, the water circulation flow rate of the water tank should be increased to 6000m 3 / h or more, and the water temperature shall not exceed 18℃.

[0083] Performance test: before tensile and endurance tests, the steel was subjected to 705℃×32hr post-weld heat treatment; before impact test, it was subjected to 705℃×8hr simulated post-weld heat treatment; tensile test was carried out at room temperature; impact test was -30℃ Charpy V-notch; endurance test was carried out at 540℃ and stress 210MPa.

[0084] The room temperature tensile properties of the forgings are shown in Table 4, and the high temperature endurance properties of the forgings are shown in Table 5.

[0085] Table 1. Composition of creep-resistant main forgings of hydrogenation reactor (Wt%)

[0086]

[0087]

[0088] Table 2. Chemical element content of steel tapped from an electric furnace (Wt%)

[0089] C S P As Sn Sb Wt% 0.04 0.008 0.001 0.005 0.005 0.003

[0090] Table 3. Forging and heat treatment temperature parameters

[0091]

[0092] Table 4. Room temperature tensile properties of high strength creep resistant hydrogenated forgings

[0093]

[0094]

[0095] Table 5. High temperature durability properties of forgings

[0096]

[0097] It can be seen from Table 2 that the S and P elements in the steel after smelting in the alkaline electric furnace are very low, and the J coefficient and P+Sn both meet the requirements of the present invention.

[0098] It can be seen from Table 4 that after optimizing the Cr and V elements and adding the B element, the conventional mechanical properties of the forgings are slightly affected, and the mechanical property results are within the standard range.

[0099] According to the high temperature endurance test results of the new weld in Table 5, it can be seen that the high temperature endurance fracture time of samples 1#-4# after heat treatment at 705℃×32hr all reached more than 900hr, with the lowest being 992hr and the highest being 1352hr; and the higher the B element content, the longer the high temperature endurance fracture time after heat treatment, and the better the high temperature creep endurance performance of the forging.

[0100] Comparative Example 1

[0101] The composition of a vanadium-added steel forging is shown in Table 6. Compared with Example 1, the Cr content is higher, reaching 2.46%, the V content is not low, at 0.30%, and the B content is very low, measured at 2ppm;

[0102] The preparation method is as follows:

[0103] Step 1, smelting: the smelting process adopts the steel ingot smelting process of basic electric furnace roughing + vacuum carbon deoxidation refining + vacuum pouring, and the specific process is the same as that of Example 1;

[0104] Step 2, forging: the forging process is the same as that of Example 1;

[0105] Step 3: Heat treatment: The post-forging heat treatment process is the same as that in Example 1.

[0106] Performance test: before tensile and endurance tests, the forgings were subjected to 705℃×32hr post-weld heat treatment, and before impact test, they were subjected to 705℃×8hr simulated post-weld heat treatment; the tensile test was carried out at room temperature; the impact test was -30℃ Charpy V-notch; the endurance test was carried out at 540℃ and stress 210MPa; the room temperature tensile properties and high temperature endurance properties of the forgings are shown in Table 7.

[0107] Comparative Example 2

[0108] The composition of a vanadium-added steel forging is the same as that of Example 1, and the preparation method is as follows:

[0109] Step 1, smelting: the smelting process adopts alkaline electric furnace rough refining + vacuum carbon deoxidation refining, and the casting process does not use protective gas casting and vacuum;

[0110] Step 2, forging: the forging process is the same as that of Example 1;

[0111] Step 3: Heat treatment: The post-forging heat treatment process is the same as that in Example 1.

[0112] Performance test: before tensile and endurance tests, the forgings were subjected to 705℃×32hr post-weld heat treatment, and before impact test, they were subjected to 705℃×8hr simulated post-weld heat treatment; the tensile test was carried out at room temperature; the impact test was -30℃ Charpy V-notch; the endurance test was carried out at 540℃ and stress 210MPa; the room temperature tensile properties and high temperature endurance properties of the forgings are shown in Table 7.

[0113] Comparative Example 3

[0114] The composition of a vanadium-added steel forging is the same as that of Example 1, and the preparation method is as follows:

[0115] Step 1, smelting: the smelting process adopts the steel ingot smelting process of basic electric furnace roughing + vacuum carbon deoxidation refining + vacuum pouring, and the specific process is the same as that of Example 1;

[0116] Step 2, forging: the forging process is the same as that of Example 1;

[0117] Step 3, heat treatment: the post-forging heat treatment process is annealing at 930℃, the performance heat treatment quenching temperature is 955℃, and the tempering temperature is 680℃.

[0118] Performance test: before tensile and endurance tests, the forgings were subjected to 705℃×32hr post-weld heat treatment, and before impact test, they were subjected to 705℃×8hr simulated post-weld heat treatment; the tensile test was carried out at room temperature; the impact test was -30℃ Charpy V-notch; the endurance test was carried out at 540℃ and stress 210MPa; the room temperature tensile properties and high temperature endurance properties of the forgings are shown in Table 7.

[0119] Table 6 Chemical composition of finished barrel forgings of comparative example (Wt%)

[0120]

[0121]

[0122] Table 7 Comparison of room temperature tensile properties and high temperature endurance properties of forgings of Example 1 and comparative example

[0123]

[0124] It can be seen from Tables 1, 6 and 7 that, compared with Example 1, Comparative Example 1 has a higher Cr content and a higher V content, and the conventional mechanical properties meet the requirements. However, due to the extremely low B content, the high temperature endurance performance of the forging is not high, only 452 hours, which does not meet the standard requirements; this indicates that the higher Cr content and the extremely low B content are not conducive to the creep endurance performance of the forging;

[0125] Comparative Example 2 did not use vacuum, which caused secondary oxidation during the pouring process. The O content in the composition was high, the impact energy fluctuated greatly, and the high-temperature endurance performance was also low, only 335 hr, which did not meet the standard requirements.

[0126] Comparative Example 3 Performance During the heat treatment process, the electric furnace was not repaired and the furnace wire was partially broken, resulting in a low furnace temperature and a low quenching temperature. Therefore, although the conventional performance was qualified, the value was near the lower limit. Some ferrite was found in the impact sample, so the impact energy was low and the high temperature endurance performance did not meet the standard requirements.

[0127] It can be seen from Table 7 that for the forgings whose element composition and preparation method do not conform to the present invention, the room temperature tensile properties and -30°C impact energy are lower than those of the forgings conforming to the present invention, and the high temperature endurance performance is significantly lower than that of the forgings of the present invention.

[0128] In summary, the present invention optimizes the material composition design, determines reasonable smelting process, forging and heat treatment process, controls the material structure, reduces harmful elements and oxide inclusions, and ensures the material's durable performance, thereby meeting various requirements of the service environment for the hydrogenation main material; the forgings obtained by the alloy chemical composition and preparation method of the present invention have a durable fracture time of ≥900 hr under the conditions of 540°C and 210 MPa after simulated post-weld heat treatment at 705°C×32h.

[0129] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A thick-walled forged welded structure hydrogenation reactor creep resistant main forging, characterized in that: The chemical composition and mass percentage of the forging material are: C: 0.14%-0.16%, Si: ≤0.1%, Mn: 0.3%-0.6%, P≤0.005%, S≤0.002%, Cr: 1.90%-2.20%, Mo: 0.9%-1.1%, Ni: ≤0.2%, Cu: ≤0.2%, Nb: ≤0.05%, V: 0.25%-0.35%, Ti≤0.03%, Al≤0.04%, B: 0.0010%-0.0025%, Sb≤0.004%, Sn≤0.01%, As≤0.01%, O≤0.003%, N≤0.007%, H≤0.0001%, and the remaining components are Fe and unavoidable impurities.

2. The forging according to claim 1, characterized in that The chemical composition and mass percentage of the forging material are: C: 0.14%-0.16%, Si: ≤0.1%, Mn: 0.3%-0.6%, P≤0.005%, S≤0.002%, Cr: 1.90%-2.20%, Mo: 0.9%-1.1%, Ni: ≤0.2%, Cu: ≤0.2%, Nb: ≤0.05%, V: 0.25%-0.32%, Ti≤0.03%, Al≤0.04%, B: 0.0015%-0.0025%, Sb≤0.004%, Sn≤0.01%, As≤0.01%, O≤0.003%, N≤0.007%, H≤0.0001%, and the remaining components are Fe and unavoidable impurities.

3. A method for preparing a creep-resistant main body forging of a thick-walled forged-welded structure hydrogenation reactor, used for preparing the forging according to claim 1 or 2, characterized in that: Including ingot smelting - forging - post-forging heat treatment - performance heat treatment.

4. The preparation method according to claim 3, characterized in that: The smelting process includes basic electric furnace rough refining+vacuum carbon deoxidation refining+vacuum pouring ingot casting.

5. The preparation method according to claim 4, characterized in that: After the alkaline electric furnace rough refining, the residual elements are required to meet P≤0.001%, S≤0.01% when tapping, and the temper embrittlement sensitivity coefficient J=(Si+Mn)×(P+Sn)×10 4 ≤60, P+Sn≤0.012%, elements are introduced in mass percentage.

6. The preparation method according to claim 3, characterized in that: The forging process adopts a forging process combining upsetting, drawing and hole expansion, the ratio of upsetting ratio to drawing ratio ranges from 0.92 to 1.08, and the main section forging ratio is greater than 3.

5.

7. The preparation method according to claim 6, characterized in that: The initial forging temperature is strictly controlled during the forging process, which is controlled at 1200-1250℃, and the final forging temperature is not lower than 850℃.

8. The preparation method according to claim 3, characterized in that: The post-forging heat treatment adopts annealing at 920-960°C.

9. The preparation method according to claim 3, characterized in that: The performance heat treatment adopts quenching at 960-980°C and tempering at 680-720°C.

10. The preparation method according to claim 9, characterized in that: The performance heat treatment process adopts water quenching for quenching, and the water temperature is not higher than 18°C.

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