Preparation method of high yield ratio die steel CX13-8

Abstract

The invention discloses a preparation method of a high-yield ratio die steel CX13-8. The high-yield ratio die steel comprises the following chemical components in weight percentage: C content ≤0.05%, Si content ≤0.18%, Mn content ≤0.10%, S content ≤0.008%, P content ≤0.018%, Cr content 12.25%-13.25%, Ni content 7.50%-8.50%, Mo content 2.00%-2.60%, Al content 0.90%-1.35%, and the balance is Fe. During the preparation, the high-yield ratio die steel is smelted in an induction vacuum degassing furnace + argon protection electroslag method to meet the purity requirements of the die steel. The final forging adopts low-temperature large deformation forging to refine the grains. After solid solution + aging heat treatment, the high-yield ratio die steel meets the standard requirements of CX13-8. The high yield ratio can achieve lightweighting of the die material.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy steel manufacturing, and in particular to a method for preparing high-yield ratio die steel CX13-8. Background Art

[0002] Mold steel CX13-8 steel is a martensitic aging stainless steel. The main chemical components of the steel are (%) C≤0.05%, Cr12.25%-13.25%, Ni7.50%-8.50%, Mo2.00%-2.60%, and Al 0.90%-1.35%.

[0003] CX13-8 steel is similar to PH13-8 steel. PH13-8 steel utilizes a "VIM+VAR" double vacuum smelting process. Its outstanding features include high strength, excellent fracture toughness, good transverse mechanical properties, and stress corrosion resistance in marine environments. Forging, solution treatment, and aging heat treatment yield excellent overall performance, resulting in extensive applications in aerospace, nuclear reactor components, and the petrochemical industry. Applications include cold heading and machined fasteners, aircraft components, nuclear reactor components, and petrochemical equipment. CX13-8 steel is used in hot runner mold steel. One of the research and development directions in this field is lightweighting all mold materials. The high yield strength ratio of CX13-8 mold steel facilitates this lightweighting.

[0004] CX13-8 mold steel's manufacturability and innovative processes, including their implementation methods, include smelting, forging, and heat treatment. Smelting utilizes an "induction vacuum degassing furnace with argon shielded electroslag" process. Forging emphasizes a deformation of ≥50% below 1080°C, with low-temperature forging intended to achieve grain refinement. Heat treatment utilizes solution treatment at 927°C ±10°C and aging at 545°C ±10°C for ≥24 hours. After aging, the product achieves a surface hardness of HRC 40-44. After passing the test, tensile strength, yield strength, fatigue strength, and impact energy are tested at 400°C under hot runner conditions.

[0005] The specific practices of the innovative heat treatment process for CX13-8 mold steel are: solid solution and aging heat treatment, temperature and holding time parameters, which ensure that all mechanical properties after the final heat treatment (400℃) meet the standard requirements and meet the service life and cost requirements of the hot runner material. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of high yield ratio mold steel CX13-8 to obtain high yield ratio mold steel CX13-8, which can meet the high temperature mechanical performance requirements of mold core and manifold under harsh working conditions of hot runner.

[0007] To achieve the above objectives, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a high yield ratio die steel CX13-8, wherein the high yield ratio die steel CX13-8 comprises the following chemical components in percentage by weight:

[0009] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 12.25%-13.25%, Ni content 7.50%-8.50%, Mo content 2.00%-2.60%, Al content 0.90%-1.35%, and the balance is Fe;

[0010] The preparation of the high yield ratio die steel CX13-8 includes a smelting process, a forging process and a heat treatment process; after the smelting, cooling and sawing in the "induction vacuum degassing furnace + argon protection electroslag" are completed, the steel ingot is forged, and the focus of the forging is the first fire using low-temperature and large deformation forging; after the forging process is completed, it enters the final performance heat treatment process.

[0011] Furthermore, during the forging process, the initial forging temperature is 1170-1190° C., and during the subsequent forging, the forging temperature is below 1080° C., and the forging deformation should be ≥50%.

[0012] Furthermore, the weight percentages of the chemical components are:

[0013] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 12.50%-13.00%, Ni content 7.80%-8.20%, Mo content 2.20%-2.40%, Al content 0.95%-1.30%, and the balance is Fe.

[0014] Furthermore, the weight percentages of the chemical components are:

[0015] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 12.80%, Ni content 8.00%, Mo content 2.30%, Al content 1.20%, and the balance is Fe.

[0016] Furthermore, the preparation of the high yield ratio die steel CX13-8 specifically includes the following steps:

[0017] S1. Smelting

[0018] S11, preparing the raw materials according to the above chemical composition, and baking the ferroalloy in the raw materials at high temperature;

[0019] S12, ingredients: 5280 kg pure Fe, 590 kg Ni plate, 948 kg Cr metal, 175 kg Mo metal, 120.5 kg Al ingot, 40 kg Al-CaO agent (20% Al), 6 kg Ce metal, 3 kg Ca wire, 6 kg Ni-Mg alloy, 30% Mg;

[0020] S13, enter the induction vacuum degassing furnace, clean the ladle before smelting, bake it well, blow off the soot before loading the raw materials into the electric furnace to prevent carbon increase; load the furnace charge except Al ingot at one time, use lime to make slag while melting, and prevent the steel liquid from being exposed; use Al-CaO agent to diffuse the deoxidizer, add Al-CaO agent while melting, and the total amount per furnace is 40 kg; when it is fully melted at 1580℃, take samples for full analysis; after the sampling is qualified, clean the slag, add 1.5 kg of metal Ca wire into the furnace cover, and add 120.5 kg of Al ingot after 5 minutes; the slag is white, vacuum ≤100Pa, and keep Holding time ≥ 20 minutes; breaking the air to take samples, inserting 1.5 kg of metal Ca wire and 6 kg of metal Ce wire, and tapping after 10 minutes; adding 6 kg of Ni-Mg alloy with the steel flow during tapping; adding 6 kg of Ni-Mg alloy and 6 kg of rare earth wire fed through the center injection pipe with the steel flow; tapping temperature 1600-1610℃, ladle temperature 1570-1580℃; filling the ladle with argon for 3 minutes before tapping, and tapping the riser with 5 kg / ton of exothermic agent, 5 kg / ton of rice husk, and 6 kg / piece of protective slag; after cooling the mold for 6 hours, demoulding and air cooling are carried out, the riser is sawed, and the argon protection electroslag process is entered;

[0021] S14, argon gas protection electroslag sequence

[0022] After cutting the electrode riser, clean the surface with a grinding wheel to remove the glass water and oxide layer, then weld the dummy electrode; use 1Cr12Mo or 0Cr13 turnings or plate edges baked at ≥500℃ for ≥2 hours to start the arc; use 2Cr13 baked at ≥500℃ for ≥2 hours as the base pad; slag system: 90kg pre-melted slag, 10kg fluorite powder, 10kg lime, 3kg magnesia, mix well, bake at ≥700℃ for 6 hours, and add 300g aluminum powder to the slag; fill with argon for 5 minutes before starting the arc; smelting current 11500A-11000A, voltage 41-40V, melting rate ±8kg / minute; feeding and filling for ≥60 minutes, power decrement control, and the electrode rod tail residue is ≥80kg; cool in the crystallizer for 150 minutes, remove, and cover cool for ≥72 hours.

[0023] S2, Forging

[0024] S21, first sequence: after sawing both ends of a 3-ton electroslag ingot, heat it to 530℃±10℃, keep it warm for 120 minutes, then heat it to 1170-1190℃, keep it warm for 360 minutes;

[0025] S22, second step: upsetting to a height of H = 800mm, then drawing to 300mm × 770mm, placing at 1080-1060℃, keeping warm for 60 minutes;

[0026] S23, third sequence: pull out to 120mm×720mm, air-cool, and saw to the required size;

[0027] S3. Machining

[0028] Perform machining according to the reserved allowance of the machining size to obtain the machined steel sheet;

[0029] S4. Heat treatment process

[0030] The heat treatment process includes solution treatment + aging treatment;

[0031] Solution: Heat to 927±10℃, keep warm for 6 minutes per mm of effective thickness of the sheet, then air cool to room temperature and place in aging furnace;

[0032] The aging treatment temperature is 545℃±10℃, the holding time is ≥24 hours, and then it is taken out of the furnace and air-cooled to room temperature to obtain the high yield strength ratio die steel CX13-8;

[0033] S5. Machining

[0034] Performing machining according to the machining dimensions to obtain the machined steel sheet;

[0035] S6, ultrasonic flaw detection

[0036] High yield-to-strength ratio die steel CX13-8 plate is inspected according to ASTM A388 standard;

[0037] S7. Test the hardness at room temperature to HRC40-44; perform high temperature mechanical property test at 400℃.

[0038] Furthermore, in step S11, the ferroalloy is subjected to high-temperature baking by placing the ferroalloy in a baking furnace and heating it to 730-780° C., and then maintaining the temperature at 730-780° C. for at least 6 hours.

[0039] Furthermore, in the step S12, the pure Fe surface is derusted and the Ni plate is subjected to dehydrogenation annealing at 550° C. for a holding time of ≥10 hours.

[0040] Furthermore, in step S13, the rare earth filaments are lanthanum-cerium rare earth, wherein the lanthanum content is ≥50%.

[0041] Furthermore, in step S14, the fluorite powder has CaF2≥98%, SiO2≤1%, and the lime is selected lime, which is burned thoroughly and crushed into a size of ≤10 mm.

[0042] Furthermore, in step S4, the solution treatment temperature is 927°C, the holding time is 6 minutes / mm, and then air-cooled to room temperature; the aging treatment temperature is 545°C, the holding time is ≥24 hours, and then air-cooled to room temperature, to obtain HRC40-44, 400°C tensile strength ≥1000MPa, 400°C yield strength ≥900MPa, 400°C impact value ≥150J, 400°C fatigue strength: ≥500MPa, and no fracture occurs after ≥10 million cycles, thereby obtaining the optimal combination of mold materials with high yield ratio, toughness and corrosion resistance.

[0043] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects:

[0044] (1) The preparation method of the high yield strength ratio mold steel CX13-8 provided by the present invention adopts the smelting method of "induction vacuum degassing furnace + argon protection electroslag" instead of the "VIM + VAR" double vacuum smelting method, which meets the standard requirements of hot runner materials in the mold steel field.

[0045] (2) The preparation method of the high yield strength ratio die steel CX13-8 provided by the present invention adopts low temperature forging with a deformation of ≥50% during final forging. The purpose of low temperature forging is to obtain refined grains.

[0046] (3) The preparation method of the high yield strength ratio mold steel CX13-8 provided by the present invention adopts 927℃±10℃ solid solution treatment and 545℃±10℃ aging. After the aging holding time is ≥24 hours, the surface hardness of the product is HRC40-44. After passing the test, the tensile strength, yield strength, fatigue strength and impact energy are tested at 400℃ under the mold hot runner working condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0048] Figure 1 This is the test result of the grain size of the high yield ratio die steel CX13-8 obtained in Example 1 after solution treatment and aging treatment, with a multiple of 100 times;

[0049] Figure 2 This is the test result of the grain size of the solution + aging treatment of the high yield ratio die steel CX13-8 obtained in Example 2, with a multiple of 100 times;

[0050] Figure 3 This is the test result of the solution + aging treatment grain size of the high yield ratio die steel CX13-8 obtained in Example 3, with a multiple of 100 times;

[0051] Figure 4 This is the test result of the grain size of the solution + aging treatment of the high yield ratio die steel CX13-8 obtained in Example 4, with a multiple of 100 times;

[0052] Figure 5 This is the test result of the solution + aging treatment grain size of the high yield ratio die steel CX13-8 obtained in Example 5, with a multiple of 100 times;

[0053] Figure 6 This is the result of the solution + aging treatment of the high yield ratio die steel CX13-8 obtained in Example 6, and the multiple is 100 times. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0055] The object of the present invention is achieved through the following technical solutions:

[0056] 1. Preparation Example

[0057] Example 1:

[0058] 1.1 Chemical composition

[0059] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 12.80%, Ni content 8.10%, Mo content 2.40%, Al content 1.35%, and the balance is Fe.

[0060] 1.2 Preparation method, specifically comprising the following steps:

[0061] S1. Smelting

[0062] S11, preparing the raw materials according to the above chemical composition, and baking the ferroalloy in the raw materials at high temperature;

[0063] S12, ingredients: 5280 kg pure Fe, 590 kg Ni plate, 948 kg Cr metal, 175 kg Mo metal, 120.5 kg Al ingot, 40 kg Al-CaO agent (20% Al), 6 kg Ce metal, 3 kg Ca wire, 6 kg Ni-Mg alloy, 30% Mg;

[0064] S13, enter the induction vacuum degassing furnace, clean the ladle before smelting, bake it well, blow off the soot before loading the raw materials into the electric furnace to prevent carbon increase; load the furnace charge except Al ingot at one time, use lime to make slag while melting, and prevent the steel liquid from being exposed; use Al-CaO agent to diffuse the deoxidizer, add Al-CaO agent while melting, and the total amount per furnace is 40 kg; when the temperature is fully melted at 1580℃, take samples for full analysis; after the samples are qualified, clean the slag, add 1.5 kg of metal Ca wire into the furnace cover, and add 120.5 kg of Al ingot after 5 minutes; the slag is white, and vacuum is ≤10 0Pa, hold time ≥ 20 minutes; break the air to take samples, insert 1.5 kg of metal Ca wire and 6 kg of metal Ce, and tap after 10 minutes; add 6 kg of Ni-Mg alloy with the steel flow during tapping; add 6 kg of Ni-Mg alloy and 6 kg of rare earth wire fed through the center injection pipe with the steel flow; the tapping temperature is 1610℃, and the temperature in the ladle is 1580℃; fill the ladle with argon for 3 minutes before tapping, and tap the riser with 5 kg / ton of exothermic agent, 5 kg / ton of rice husk, and 6 kg / piece of protective slag; after cooling the mold for 6 hours, demould and air cool, saw the riser, and enter the argon protection electroslag process;

[0065] S14, argon gas protection electroslag sequence

[0066] After cutting the electrode riser, clean the surface with a grinding wheel to remove the glass water and oxide layer, then weld the dummy electrode; use 1Cr12Mo or 0Cr13 turnings or plate edges baked at ≥500℃ for ≥2 hours to start the arc; use 2Cr13 baked at ≥500℃ for ≥2 hours as the base pad; slag system: 90kg pre-melted slag, 10kg fluorite powder, 10kg lime, 3kg magnesia, mix well, bake at ≥700℃ for 6 hours, and add 300g aluminum powder to the slag; fill with argon for 5 minutes before starting the arc; smelting current is 11000A, voltage is 40V, and melting rate is ±8kg / minute; feeding and filling are ≥60 minutes, with power decreasing control, and the electrode rod tail is ≥80kg; cool in the crystallizer for 150 minutes, remove, and hood cool for ≥72 hours;

[0067] S2, Forging

[0068] S21, first sequence: after sawing both ends of a 3-ton electroslag ingot, heat it to 530°C, keep it warm for 120 minutes, then heat it to 1170-1190°C, keep it warm for 360 minutes;

[0069] S22, second step: upsetting to a height of H = 800 mm, then drawing to 300 mm × 770 mm, placing at 1080 ° C, keeping warm for 60 minutes;

[0070] S23, third sequence: pull out to 120mm×720mm, air-cool, and saw to the required size;

[0071] S3. Machining

[0072] Perform machining according to the reserved allowance of the machining size to obtain the machined steel sheet;

[0073] S4. Heat treatment process

[0074] The heat treatment process includes solution treatment + aging treatment. The test results of grain size of solution treatment + aging treatment are as follows: Figure 1 As shown;

[0075] Solution: Heat to 927℃, keep warm for 6 minutes per mm of effective thickness of the sheet, then air cool to room temperature and put into aging furnace;

[0076] The aging treatment temperature is 545℃, the holding time is ≥24 hours, and then it is taken out of the furnace and air-cooled to room temperature to obtain the high yield strength ratio die steel CX13-8;

[0077] S5. Machining

[0078] Performing machining according to the machining dimensions to obtain the machined steel sheet;

[0079] S6, ultrasonic flaw detection

[0080] High yield-to-strength ratio die steel CX13-8 plate is inspected according to ASTM A388 standard;

[0081] S7. Test the hardness at room temperature to HRC42; perform high temperature mechanical property testing at 400℃.

[0082] Example 2:

[0083] 2.1 Chemical composition

[0084] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 13.25%, Ni content 8.20%, Mo content 2.40%, Al content 0.90%, and the balance is Fe.

[0085] 2.2 Preparation method, specifically comprising the following steps:

[0086] S1. Smelting

[0087] S11, preparing the raw materials according to the above chemical composition, and baking the ferroalloy in the raw materials at high temperature;

[0088] S12, ingredients: 5280 kg pure Fe, 590 kg Ni plate, 948 kg Cr metal, 175 kg Mo metal, 120.5 kg Al ingot, 40 kg Al-CaO agent (20% Al), 6 kg Ce metal, 3 kg Ca wire, 6 kg Ni-Mg alloy, 30% Mg;

[0089] S13, enter the induction vacuum degassing furnace, clean the ladle before smelting, bake it well, blow off the soot before loading the raw materials into the electric furnace to prevent carbon increase; load the furnace charge except Al ingot at one time, use lime to make slag while melting, and prevent the steel liquid from being exposed; use Al-CaO agent to diffuse the deoxidizer, add Al-CaO agent while melting, and the total amount per furnace is 40 kg; when it is fully melted at 1580℃, take samples for full analysis; after the sampling is qualified, clean the slag, add 1.5 kg of metal Ca wire into the furnace cover, and add 120.5 kg of Al ingot after 5 minutes; the slag is white, vacuum ≤100Pa, and keep Holding time ≥ 20 minutes; breaking the air to take samples, inserting 1.5 kg of metal Ca wire and 6 kg of metal Ce wire, and tapping after 10 minutes; adding 6 kg of Ni-Mg alloy with the steel flow during tapping; adding 6 kg of Ni-Mg alloy and 6 kg of rare earth wire fed through the center injection pipe with the steel flow; tapping temperature 1600-1610℃, ladle temperature 1570-1580℃; filling the ladle with argon for 3 minutes before tapping, and tapping the riser with 5 kg / ton of exothermic agent, 5 kg / ton of rice husk, and 6 kg / piece of protective slag; after cooling the mold for 6 hours, demoulding and air cooling are carried out, the riser is sawed, and the argon protection electroslag process is entered;

[0090] S14, argon gas protection electroslag sequence

[0091] After cutting the electrode riser, clean the surface with a grinding wheel to remove the glass water and oxide layer, then weld the dummy electrode; use 1Cr12Mo or 0Cr13 turnings or plate edges baked at ≥500℃ for ≥2 hours to start the arc; use 2Cr13 baked at ≥500℃ for ≥2 hours as the base pad; slag system: 90kg pre-melted slag, 10kg fluorite powder, 10kg lime, 3kg magnesia, mix well, bake at ≥700℃ for 6 hours, and add 300g aluminum powder to the slag; fill with argon for 5 minutes before starting the arc; smelting current is 11000A, voltage is 40V, and melting rate is ±8kg / minute; feeding and filling are ≥60 minutes, with power decreasing control, and the electrode rod tail is ≥80kg; cool in the crystallizer for 150 minutes, remove, and hood cool for ≥72 hours;

[0092] S2, Forging

[0093] S21, first sequence: after sawing both ends of 3 tons of electroslag ingot, heat it to 535℃, keep it warm for 120 minutes, then heat it to 1170-1190℃, keep it warm for 360 minutes;

[0094] S22, second step: upsetting to a height of H = 800 mm, then drawing to 300 mm × 770 mm, placing at 1060 ° C, keeping warm for 60 minutes;

[0095] S23, third sequence: pull out to 120mm×720mm, air-cool, and saw to the required size;

[0096] S3. Machining

[0097] Perform machining according to the reserved allowance of the machining size to obtain the machined steel sheet;

[0098] S4. Heat treatment process

[0099] The heat treatment process includes solution treatment + aging treatment. The test results of grain size of solution treatment + aging treatment are as follows: Figure 2 As shown;

[0100] Solution: Heat to 927℃, keep warm for 6 minutes per mm of effective thickness of the sheet, then air cool to room temperature and put into aging furnace;

[0101] The aging treatment temperature is 545℃, the holding time is ≥24 hours, and then it is taken out of the furnace and air-cooled to room temperature to obtain the high yield strength ratio die steel CX13-8;

[0102] S5. Machining

[0103] Performing machining according to the machining dimensions to obtain the machined steel sheet;

[0104] S6, ultrasonic flaw detection

[0105] High yield-to-strength ratio die steel CX13-8 plate is inspected according to ASTM A388 standard;

[0106] S7. Test the hardness at room temperature to HRC41.5; perform high temperature mechanical property testing at 400℃.

[0107] Example 3:

[0108] 3.1 Chemical composition

[0109] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 13.05%, Ni content 8.05%, Mo content 2.40%, Al content 1.25%, and the balance is Fe.

[0110] 3.2 Preparation method, specifically comprising the following steps:

[0111] S1. Smelting

[0112] S11, preparing the raw materials according to the above chemical composition, and baking the ferroalloy in the raw materials at high temperature;

[0113] S12, ingredients: 5280 kg pure Fe, 590 kg Ni plate, 948 kg Cr metal, 175 kg Mo metal, 120.5 kg Al ingot, 40 kg Al-CaO agent (20% Al), 6 kg Ce metal, 3 kg Ca wire, 6 kg Ni-Mg alloy, 30% Mg;

[0114] S13, enter the induction vacuum degassing furnace, clean the ladle before smelting, bake it well, blow off the soot before loading the raw materials into the electric furnace to prevent carbon increase; load the furnace charge except Al ingot at one time, use lime to make slag while melting, and prevent the steel liquid from being exposed; use Al-CaO agent to diffuse the deoxidizer, add Al-CaO agent while melting, and the total amount per furnace is 40 kg; when the temperature is fully melted at 1580℃, take samples for full analysis; after the samples are qualified, clean the slag, add 1.5 kg of metal Ca wire into the furnace cover, and add 120.5 kg of Al ingot after 5 minutes; the slag is white, and vacuum is ≤10 0Pa, hold time ≥ 20 minutes; break the air to take samples, insert 1.5 kg of metal Ca wire and 6 kg of metal Ce, and tap after 10 minutes; add 6 kg of Ni-Mg alloy with the steel flow during tapping; add 6 kg of Ni-Mg alloy and 6 kg of rare earth wire fed through the center injection pipe with the steel flow; the tapping temperature is 1610℃, and the temperature in the ladle is 1570℃; fill the ladle with argon for 3 minutes before tapping, and tap the riser with 5 kg / ton of exothermic agent, 5 kg / ton of rice husk, and 6 kg / piece of protective slag; after cooling the mold for 6 hours, demould and air cool, saw the riser, and enter the argon protection electroslag process;

[0115] S14, argon gas protection electroslag sequence

[0116] After cutting the electrode riser, clean the surface with a grinding wheel to remove the glass water and oxide layer, then weld the dummy electrode; use 1Cr12Mo or 0Cr13 turnings or plate edges baked at ≥500℃ for ≥2 hours to start the arc; use 2Cr13 baked at ≥500℃ for ≥2 hours as the base pad; slag system: 90kg pre-melted slag, 10kg fluorite powder, 10kg lime, 3kg magnesia, mix well, bake at ≥700℃ for 6 hours, and add 300g aluminum powder to the slag; fill with argon for 5 minutes before starting the arc; smelting current 11500A-11000A, voltage 41-40V, melting rate ±8kg / minute; feeding and filling for ≥60 minutes, power decrement control, and the electrode rod tail residue is ≥80kg; cool in the crystallizer for 150 minutes, remove, and cover cool for ≥72 hours.

[0117] S2, Forging

[0118] S21, first sequence: after sawing both ends of a 3-ton electroslag ingot, heat it to 530°C, keep it warm for 120 minutes, then heat it to 1180°C, keep it warm for 360 minutes;

[0119] S22, second step: upsetting to a height of H = 800 mm, then drawing to 300 mm × 770 mm, placing at 1070 ° C, keeping warm for 60 minutes;

[0120] S23, third sequence: pull out to 120mm×720mm, air-cool, and saw to the required size;

[0121] S3. Machining

[0122] Perform machining according to the reserved allowance of the machining size to obtain the machined steel sheet;

[0123] S4. Heat treatment process

[0124] The heat treatment process includes solution treatment + aging treatment. The test results of grain size of solution treatment + aging treatment are as follows: Figure 3 As shown;

[0125] Solution: Heat to 928℃, keep warm for 6 minutes per mm of effective thickness of the sheet, then air cool to room temperature and put into aging furnace;

[0126] The aging treatment temperature is 544℃, the holding time is ≥24 hours, and then it is taken out of the furnace and air-cooled to room temperature to obtain the high yield strength ratio die steel CX13-8;

[0127] S5. Machining

[0128] Performing machining according to the machining dimensions to obtain the machined steel sheet;

[0129] S6, ultrasonic flaw detection

[0130] High yield-to-strength ratio die steel CX13-8 plate is inspected according to ASTM A388 standard;

[0131] S7. Test the hardness at room temperature to HRC42; perform high temperature mechanical property testing at 400℃.

[0132] Example 4:

[0133] 4.1 Chemical composition

[0134] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 12.80%, Ni content 7.50%, Mo content 2.20%, Al content 1.25%, and the balance is Fe.

[0135] 4.2 Preparation method, same as Example 1. The test results of the grain size of the solution + aging treatment are as follows Figure 4 shown.

[0136] Example 5:

[0137] 5.1 Chemical composition

[0138] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 12.55%, Ni content 7.65%, Mo content 2.30%, Al content 1.15%, and the balance is Fe.

[0139] 5.2 Preparation method, same as Example 1. The test results of the grain size of the solution + aging treatment are as follows Figure 5 shown.

[0140] Example 6:

[0141] 6.1 Chemical composition

[0142] C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 12.25%, Ni content 7.85%, Mo content 2.60%, Al content 1.35%, and the balance is Fe.

[0143] 6.2 Preparation method, same as Example 1. The test results of the grain size of the solution + aging treatment are as follows Figure 6 shown.

[0144] 2. Performance Testing

[0145] The high yield-to-strength ratio die steel CX13-8 obtained in Examples 1-6 was sampled and tested respectively.

[0146] 1. Various non-metallic inclusions (coarse and fine) were tested according to Method A of ASTM E45-2018. The results are shown in Table 1 below:

[0147] Table 1 Detection results of non-metallic inclusions

[0148]

[0149]

[0150] 2. The test results of high temperature mechanical properties and room temperature hardness are shown in Table 2 below:

[0151] Table 2 High temperature mechanical properties and room temperature hardness test results

[0152] 400℃ tensile strength 400℃ yield strength 400℃ fatigue strength 400℃ impact value Room temperature hardness Standard value ≥1000(MPa) ≥900(MPa) ≥10 million times ≥150(J) HRC40-44 Example 1 1016 994 Unbroken 330 42 Example 2 1005 957 Unbroken 296 41.5 Example 3 1011 966 Unbroken 301 42 Example 4 1004 936 Unbroken 303 41 Example 5 1005 957 Unbroken 285 41 Example 6 1108 962 Unbroken 301 41.5

[0153] Note 1: The impact value is for 7X10X55 unnotched specimen.

[0154] Note 2: Fatigue strength: 500 MPa (stress concentration factor = 2.5; stress ratio = 0 cycles 10 million times) measured.

[0155] 3. Ultrasonic flaw detection

[0156] According to ASTM A388 standard, 100% flaw detection was performed, and the results are shown in Table 3 below:

[0157] Table 3 Ultrasonic flaw detection results

[0158] Qualified Example 1 100% qualified Example 2 100% qualified Example 3 100% qualified Example 4 100% qualified Example 5 100% qualified Example 6 100% qualified

[0159] 4. Metallographic testing

[0160] The actual grain size of forged plates was evaluated according to ASTM E112, which required a grade of 5 or higher. Test result: grade 6.

[0161] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high yield ratio die steel CX13-8, characterized by: The weight percentages of the chemical components of the high yield ratio die steel CX13-8 are: C content ≤ 0.05%, Si content ≤ 0.18%, Mn content ≤ 0.10%, S content ≤ 0.008%, P content ≤ 0.018%, Cr content 12.80%, Ni content 8.00%, Mo content 2.30%, Al content 1.20%, balance Fe; The preparation of the high-yield ratio die steel CX13-8 includes smelting, forging, and heat treatment. After smelting in an "induction vacuum degassing furnace + argon-shielded electroslag" furnace, cooling, and sawing, the steel ingot is forged. The focus of the forging is the final heat treatment using low-temperature, large-deformation forging. After the forging process is completed, the final performance heat treatment process begins. The preparation of the high-yield ratio die steel CX13-8 specifically includes the following steps: S1. Smelting S11, preparing the raw materials according to the above chemical composition, and baking the ferroalloy in the raw materials at high temperature; S12, ingredients: 5280 kg pure Fe, 590 kg Ni plate, 948 kg metal Cr, 175 kg metal Mo, 120.5 kg Al ingot, 40 kg Al-CaO agent (Al accounts for 20%), 6 kg metal Ce, 3 kg metal Ca wire, 6 kg Ni-Mg alloy (Mg accounts for 30%); S13, enter the induction vacuum degassing furnace, clean the ladle before smelting, bake it well, blow off the soot before loading the raw materials into the electric furnace to prevent carbon increase; load the furnace charge except Al ingot at one time, use lime to make slag while melting, and prevent the steel liquid from being exposed; use Al-CaO agent to diffuse the deoxidizer, add Al-CaO agent while melting, and the total amount per furnace is 40 kg; when the temperature is fully melted at 1580℃, take samples for full analysis; after the samples are qualified, clean the slag, add 1.5 kg of metal Ca wire into the furnace cover, and add 120.5 kg of Al ingot after 5 minutes; the slag is white, and vacuum extraction is carried out. Air ≤ 100Pa, hold time ≥ 20 minutes; break the air to take samples, insert 1.5 kg of metal Ca wire and 6 kg of metal Ce, and tap after 10 minutes; add 6 kg of Ni-Mg alloy and 6 kg of rare earth wire fed through the center injection pipe as the steel flows; tapping temperature is 1600-1610℃, and the temperature in the ladle is 1570-1580℃; fill the ladle with argon for 3 minutes before tapping, and after tapping, add 5 kg / ton of heat-generating agent for the riser, 5 kg / ton of rice husk, and 6 kg / piece of protective slag; after cooling the mold for 6 hours, demould and air cool, saw the riser, and enter the argon protection electroslag process; S14, argon gas protection electroslag sequence After cutting the riser of the electrode, clean the surface with a grinding wheel to remove the glass water and oxide layer, and then weld the dummy electrode; Use 1Cr12Mo or 0Cr13 turnings or plate edges with a temperature of ≥500℃ and a baking time of ≥2 hours to start the arc; use 2Cr13 with a temperature of ≥500℃ and a baking time of ≥2 hours as the base pad; Slag system: 90kg pre-melted slag, 10kg fluorite powder, 10kg lime, 3kg magnesia, mix well, bake at ≥700℃ for 6h, add 300g aluminum powder to the slag; fill with argon for 5 minutes before arc starting; smelting current 11500A-11000A, voltage 41-40V; feeding and filling for ≥60 minutes, power decrement control, electrode rod tail amount ≥80kg; cool in the crystallizer for 150 minutes, remove, and hood cool for ≥72h; S2, Forging S21, first sequence: after sawing both ends of 3 tons of electroslag ingot, heat it to 530℃±10℃, keep it warm for 120 minutes, then heat it to 1170-1190℃, keep it warm for 360 minutes; S22, second step: upsetting to a height of H = 800mm, then drawing to 300mm × 770mm, placing at 1080-1060℃, keeping warm for 60 minutes; S23, third sequence: pull out to 120mm×720mm, air-cool, and saw to the required size; S3. Machining Perform machining according to the reserved allowance of the machining size to obtain the machined steel sheet; S4. Heat treatment process The heat treatment process includes solution treatment + aging treatment; Solution: Heat to 927±10℃, keep warm for 6 minutes per mm of effective thickness of the sheet, then air cool to room temperature and place in aging furnace; The aging treatment temperature is 545℃±10℃, the holding time is ≥24 hours, and then it is taken out of the furnace and air-cooled to room temperature to obtain the high yield strength ratio die steel CX13-8; S5. Machining Perform machining according to the machining dimensions to obtain machined steel sheet material; S6, ultrasonic flaw detection High yield-to-strength ratio die steel CX13-8 plate, tested according to ASTM A388 standard; S7. Test the hardness at room temperature to HRC40-44; perform high temperature mechanical property test at 400℃.

2. The method for preparing the high yield ratio die steel CX13-8 according to claim 1, characterized in that: During forging, the initial forging temperature is 1170-1190°C. During subsequent forging, the forging temperature is below 1080°C, and the forging deformation should be ≥50%.

3. The method for preparing the high yield ratio die steel CX13-8 according to claim 1, characterized in that: In the step S11, the ferroalloy is subjected to high temperature baking by placing the ferroalloy in a baking furnace and heating it to 730-780° C., and then maintaining the temperature at 730-780° C. for at least 6 hours.

4. The method for preparing the high yield ratio die steel CX13-8 according to claim 1, characterized in that: In the step S12, the pure Fe surface is derusted and the Ni plate is subjected to dehydrogenation annealing at 550° C. for a holding time of ≥10 hours.

5. The method for preparing the high yield ratio die steel CX13-8 according to claim 1, characterized in that: In step S13, the rare earth filament is lanthanum-cerium rare earth, wherein the lanthanum content is ≥50%.

6. The method for preparing the high yield ratio die steel CX13-8 according to claim 1, characterized in that: In step S14, the fluorite powder has CaF2≥98%, SiO2≤1%, and the lime is selected lime, which is burned thoroughly and crushed into a size of ≤10 mm.

7. The method for preparing the high yield ratio die steel CX13-8 according to claim 1, characterized in that: In step S4, the solution treatment temperature is 927°C, the holding time is 6 minutes / mm, and then air cooling is performed to room temperature; the aging treatment temperature is 545°C, the holding time is ≥24 hours, and then air cooling is performed to room temperature, thereby obtaining HRC40-44, 400°C tensile strength ≥1000MPa, 400°C yield strength ≥900MPa, 400°C impact value ≥150J, 400°C fatigue strength: ≥500MPa, and no fracture after ≥10 million cycles, thereby obtaining the optimal combination of mold materials with high yield ratio, toughness and corrosion resistance.

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