A production method for low alloy steel castings

Abstract

The present invention relates to the technical field of metal smelting, and in particular to a production method for a low-alloy steel casting. The low-alloy steel casting comprises the following raw materials in parts by weight: 95-98 parts of iron, 0.2-0.5 parts of carbon, 0.5-1.2 parts of silicon, 0.8-1.5 parts of manganese, 0.3-0.8 parts of chromium, and 0.2-0.6 parts of nickel. The present invention innovates a conventional heat treatment process for the steel casting by adding a hot isostatic pressing process and adopting a heat treatment process combining normalizing and tempering, thereby effectively eliminating tiny defects inside the casting and improving the density and mechanical properties of the casting. The hot isostatic pressing process heals pores and defects inside the casting under high temperature and high pressure, normalizing refines grains and improves strength and toughness, and tempering eliminates internal stress, stabilizes structure, and improves plasticity and toughness, thereby giving full play to the performance advantages of the low-alloy steel casting and meeting the high-performance requirements of steel castings in different fields.

Description

Technical Field

[0001] The invention relates to the technical field of metal smelting, in particular to a production method of low-alloy steel castings. Background Art

[0002] With the rapid development of industry, engineering machinery is developing towards the high-end frontier, which puts higher requirements on the performance of materials. Low alloy cast steel has the characteristics of low alloy content (total amount of alloy elements ≤5%), wide source, good comprehensive mechanical properties, simple manufacturing process and low cost. It is an engineering material with good application prospects. Ultra-high strength low alloy cast steel not only has high strength and high hardness, but also has good toughness and impact resistance.

[0003] Prior art, such as Chinese Patent Publication No. CN107760983A, discloses a method for producing low-alloy ultra-high-strength steel and its castings. The low-alloy cast steel utilizes a low carbon ratio with various alloying elements, and incorporates a relatively high trace amount of niobium to refine the grains and homogenize the structure. After heat treatment, its hardness and wear resistance are significantly improved, while its strength and toughness are rationally balanced, resulting in excellent comprehensive mechanical properties and processability. The mechanical properties of the low-carbon alloy cast steel described in the present invention are as follows: tensile strength of 1300 to 1500 MPa, yield strength of 900 to 1200 MPa, elongation ≥10%, impact energy Ak ≥40 J in a room temperature V-notch Charpy impact test, and Brinell hardness of 390-460 HBW.

[0004] In the traditional production process of low-alloy steel castings, molten steel is poured into the sand mold, and the compactness of each part of the sand mold is inconsistent, which not only affects the cooling rate of the steel casting and causes uneven shrinkage, but also the parts with low compactness are easily deformed under the pressure of the molten steel, resulting in internal gaps and defects, thus affecting the performance of the low-alloy steel casting.

[0005] Based on this, the present invention provides a method for producing low-alloy steel castings. Summary of the Invention

[0006] The object of the present invention is to provide a production method for low alloy steel castings, which can effectively improve the hardness, tensile strength and impact toughness of low alloy steel castings, thereby improving product quality.

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

[0008] A method for producing a low-alloy steel casting, comprising the following raw materials in parts by weight: 95-98 parts of iron, 0.2-0.5 parts of carbon, 0.5-1.2 parts of silicon, 0.8-1.5 parts of manganese, 0.3-0.8 parts of chromium, and 0.2-0.6 parts of nickel;

[0009] The carbon may be any one or more combinations of graphite, coke and iron carbide;

[0010] The silicon may be any one or more combinations of ferrosilicon, silicon carbide and silicon-calcium alloy;

[0011] The manganese may be any one or more combinations of ferromanganese, electrolytic metallic manganese and nitride ferromanganese;

[0012] The chromium may be any one or more combinations of ferrochrome, ferrochrome nitride and metallic chromium;

[0013] The nickel can be selected from any one or more combinations of electrolytic nickel, nickel iron and carbonyl nickel powder.

[0014] Preferably, a method for producing a low alloy steel casting comprises the following steps:

[0015] S1: Melting: Iron, carbon, silicon, manganese, chromium and nickel are weighed as needed and added to a medium frequency induction furnace. The melting temperature is set at 1500-1600°C. Deoxidation and desulfurization are performed during the melting process to obtain molten steel.

[0016] S2: Casting: Pour the molten steel into a mold with the mold temperature controlled at 1350-1450°C. After cooling and molding, a steel blank is obtained.

[0017] S3: Heat treatment: The steel blank is normalized and tempered. The normalizing temperature is set at 800-900°C and the holding time is 2-4 hours. The tempering temperature is set at 550-650°C and the holding time is 3-5 hours to obtain a steel casting.

[0018] Preferably, in the S1 smelting, boron and niobium are weighed and added to a medium frequency induction furnace, and the mass ratio of boron and niobium to iron is 0.003:0.003:1. The boron can be selected from any one or more combinations of ferroboron, borax and boron carbide, and the niobium can be selected from any one or more combinations of ferroniobium, niobium carbide and niobium nitride.

[0019] Preferably, in S1, nano-ceramic particles, graphene and carbon fibers are weighed and added to a medium-frequency induction furnace in the middle stage of smelting. The nano-ceramic particles can be selected from any one or more combinations of silicon carbide nanoparticles, aluminum oxide nanoparticles and boron nitride nanoparticles. The mass ratio of the nano-ceramic particles, graphene and carbon fibers to iron is 0.001:0.001:0.0015:1.

[0020] Preferably, in the later stage of S1 smelting, an ultrasonic oscillation device is introduced, the transducer is immersed under the surface of the molten steel and started, and the ultrasonic frequency is set to 20-40kHz and the power is 500-1000W.

[0021] Preferably, the steel piece obtained after the S2 casting is subjected to hot isostatic pressing treatment in a static pressing furnace, with the treatment temperature set at 1000-1100° C., the pressure at 100-150 MPa, and the heat and pressure are maintained for 1-2 hours.

[0022] Preferably, in the S1 smelting, aluminum deoxidizer is used for deoxidation treatment, and the amount of aluminum deoxidizer added is (0.03-0.05)% of the weight of the molten steel. A mixture of calcium carbide and limestone is used as a desulfurizer for desulfurization treatment, and the mass ratio of calcium carbide to limestone is 1:(2-3), and the amount of desulfurizer added is (0.5-1)% of the weight of the molten steel.

[0023] Preferably, during the S1 smelting process, a rotating magnetic field electromagnetic stirrer is used to stir the molten steel, and the stirring intensity is (50-100) A / ㎡.

[0024] Preferably, in the S2 casting process, a sand mold is used as the casting mold, the sand mold is resin sand, and the amount of the resin added is (1.5-2.5)% of the weight of the sand.

[0025] Preferably, the further processing method of the steel casting includes the following steps: introducing a shot peening machine to perform shot peening on the steel casting, the shot peening material is cast steel shot, the diameter of the cast steel shot is 0.5-1.5mm, the shot peening intensity is set to 0.2-0.4mmA, and a low alloy steel casting is obtained after treatment.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. In the present invention, the traditional heat treatment process of steel castings is innovated by adding a hot isostatic pressing process and adopting a heat treatment process combining normalizing and tempering, which effectively eliminates tiny defects inside the castings and improves the density and mechanical properties of the castings. The hot isostatic pressing process heals the pores and defects inside the castings under high temperature and high pressure, normalizing refines the grains, improves strength and toughness, and tempering eliminates internal stress, stabilizes the structure, and improves plasticity and toughness, fully leveraging the performance advantages of low-alloy steel castings and meeting the high-performance requirements of steel castings in different fields.

[0028] 2. In the present invention, the carbon in the basic raw materials of low-alloy steel castings can form interstitial solid solutions, hindering dislocation movement, manganese can strengthen ferrite, and enhance the strength and hardness of steel, chromium can improve the hardenability of steel, so that the steel obtains a high-hardness martensitic structure after quenching, and nickel can refine the grains, improving the toughness and hardness of steel. At the same time, compared with traditional processes, boron and niobium are added during smelting, boron improves hardenability, niobium refines the grains and precipitation strengthens, further improving the hardness, and ultrasonic vibration is introduced to refine the grains, reduce component segregation, and make the structure more uniform and dense, which is conducive to improving the hardness. The hot isostatic pressing treatment after casting eliminates internal defects, optimizes the structure, and also provides support for hardness improvement, thereby ensuring the hardness requirements of low-alloy steel castings.

[0029] 3. In the present invention, boron and niobium are added during the smelting process of the steel casting. Boron improves the hardenability of the steel, allowing the steel to be more fully transformed into a martensite structure during the quenching process. Martensite has high hardness and high strength, thereby significantly improving the hardness and tensile strength of the steel casting. Niobium works through grain refinement and precipitation strengthening mechanisms. The refined grains not only increase the strength but also improve the toughness. The precipitation of the precipitated phase further strengthens the matrix and enhances the ability of the steel casting to resist deformation and fracture. In terms of impact toughness, the combined action of boron and niobium enables the steel casting to better absorb energy when subjected to impact loads, reduces the risk of brittle fracture, and improves the comprehensive mechanical properties of the steel casting.

[0030] 4. In the present invention, nano-reinforcement phases such as nano-ceramic particles, graphene and carbon fibers are added during the smelting process of steel castings. The nano-ceramic particles are evenly distributed in the steel matrix due to their own high hardness, playing a role of dispersion strengthening, significantly improving the hardness of the steel castings. The excellent mechanical properties and high conductivity of graphene can not only enhance the tensile strength of the steel castings, but also improve their physical properties such as conductivity. The high specific strength and high modulus of carbon fibers effectively enhance the bearing capacity of the steel castings and improve the tensile strength. These nano-reinforcement phases work together to improve the impact toughness of the steel castings, enabling them to consume energy through various mechanisms when subjected to impact, reducing the generation and expansion of cracks, and comprehensively improving the performance of the steel castings. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 efforts are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for producing a low alloy steel casting, comprising the following raw materials in parts by weight: 95 parts of iron, 0.2 parts of carbon, 0.5 parts of silicon, 0.8 parts of manganese, 0.3 parts of chromium, and 0.2 parts of nickel;

[0034] Carbon selected graphite;

[0035] Silicon is selected from ferrosilicon;

[0036] Manganese selects ferromanganese;

[0037] Chromium selects ferrochrome;

[0038] The nickel selected is electrolytic nickel.

[0039] Among them, a production method of low alloy steel castings includes the following steps:

[0040] S1: Melting: Iron, carbon, silicon, manganese, chromium and nickel are weighed as needed and added to a medium frequency induction furnace. The melting temperature is set at 1500°C. Deoxidation and desulfurization are performed during the melting process to obtain molten steel.

[0041] S2: Casting: Pour the molten steel into a casting mold with the mold temperature controlled at 1350°C. After cooling and forming, a steel blank is obtained.

[0042] S3: Heat treatment: The steel blank is subjected to normalizing and tempering treatments, with the normalizing temperature set at 800°C and the holding time at temperature for 2 hours, and the tempering temperature set at 550°C and the holding time at temperature for 3 hours to obtain a steel casting.

[0043] In some embodiments, during S1 smelting, boron and niobium are weighed and added to a medium frequency induction furnace, with a mass ratio of boron to niobium to iron of 0.003:0.003:1, and boron is selected from ferroboron and niobium is selected from ferroniobium.

[0044] In some embodiments, in S1, nano-ceramic particles, graphene and carbon fibers are weighed and added to a medium-frequency induction furnace in the middle stage of smelting, the nano-ceramic particles are selected from silicon carbide nano-particles, and the mass ratio of the nano-ceramic particles, graphene and carbon fibers to iron is 0.001:0.001:0.0015:1.

[0045] In some embodiments, in the later stage of S1 smelting, an ultrasonic oscillation device is introduced, the transducer is immersed under the surface of the molten steel and started, and the ultrasonic frequency is set to 20kHz and the power is 500W.

[0046] In some embodiments, the steel piece obtained after S2 casting is subjected to hot isostatic pressing in a static pressing furnace, with the processing temperature set at 1000° C., the pressure at 100 MPa, and the heat and pressure are maintained for 1 hour.

[0047] Among them, in S1 smelting, aluminum deoxidizer is used for deoxidation treatment, and the addition amount of aluminum deoxidizer is 0.03% of the weight of molten steel. Desulfurization treatment uses a mixture of calcium carbide and limestone as a desulfurizer, the mass ratio of calcium carbide to limestone is 1:2, and the addition amount of desulfurizer is 0.5% of the weight of molten steel.

[0048] During the S1 smelting process, a rotating magnetic field electromagnetic stirrer was used to stir the molten steel with a stirring intensity of 50A / ㎡.

[0049] In the S2 casting process, a sand mold is used as the casting mold, and the sand mold is made of resin sand, and the amount of resin added is 1.5% of the weight of the sand.

[0050] In some embodiments, the further processing method of the steel casting includes the following steps: introducing a shot peening machine to shot peen the steel casting, the shot peening material is cast steel shot, the diameter of the cast steel shot is 0.5 mm, the shot peening intensity is set to 0.2 mmA, and a low alloy steel casting is obtained after treatment.

[0051] Example 2

[0052] A method for producing a low alloy steel casting, comprising the following raw materials in parts by weight: 98 parts of iron, 0.5 parts of carbon, 1.2 parts of silicon, 1.5 parts of manganese, 0.8 parts of chromium, and 0.6 parts of nickel;

[0053] Carbon selection of iron carbide;

[0054] Silicon selected from silicon calcium alloy;

[0055] Manganese-selected nitrided ferromanganese;

[0056] Chromium: metallic chromium;

[0057] The nickel selected is carbonyl nickel powder.

[0058] Among them, a production method of low alloy steel castings includes the following steps:

[0059] S1: Melting: Iron, carbon, silicon, manganese, chromium and nickel are weighed as needed and added to a medium frequency induction furnace. The melting temperature is set at 1600°C. Deoxidation and desulfurization are performed during the melting process to obtain molten steel.

[0060] S2: Casting: Pour the molten steel into a casting mold with the mold temperature controlled at 1450°C. After cooling and molding, a steel blank is obtained.

[0061] S3: Heat treatment: The steel blank is subjected to normalizing and tempering treatments, with the normalizing temperature set at 900°C and the holding time being 4 hours, and the tempering temperature set at 650°C and the holding time being 5 hours, to obtain a steel casting.

[0062] In some embodiments, during S1 smelting, boron and niobium are weighed and added to a medium frequency induction furnace, with a mass ratio of boron and niobium to iron being 0.003:0.003:1, boron is selected as boron carbide, and niobium is selected as niobium nitride.

[0063] In some embodiments, in S1, nano-ceramic particles, graphene and carbon fibers are weighed and added to a medium-frequency induction furnace in the middle stage of smelting, the nano-ceramic particles are selected from boron nitride nano-particles, and the mass ratio of nano-ceramic particles, graphene and carbon fibers to iron is 0.001:0.001:0.0015:1.

[0064] In some embodiments, in the later stage of S1 smelting, an ultrasonic oscillation device is introduced, the transducer is immersed under the surface of the molten steel and started, and the ultrasonic frequency is set to 40kHz and the power is 1000W.

[0065] In some embodiments, the steel piece obtained after S2 casting is subjected to hot isostatic pressing in a static pressing furnace, with the processing temperature set at 1100° C. and the pressure at 150 MPa, and the heat and pressure are maintained for 2 hours.

[0066] Among them, in S1 smelting, aluminum deoxidizer is used for deoxidation treatment, and the addition amount of aluminum deoxidizer is 0.05% of the weight of molten steel. The desulfurization treatment uses a mixture of calcium carbide and limestone as a desulfurizer, and the mass ratio of calcium carbide to limestone is 1:3. The addition amount of desulfurizer is 1% of the weight of molten steel.

[0067] During the S1 smelting process, a rotating magnetic field electromagnetic stirrer was used to stir the molten steel with a stirring intensity of 100A / ㎡.

[0068] In the S2 casting process, a sand mold is used as the casting mold, and the sand mold is made of resin sand, and the amount of resin added is 2.5% of the weight of the sand.

[0069] In some embodiments, the further processing method of the steel casting includes the following steps: introducing a shot peening machine to shot peen the steel casting, the shot peening material is cast steel shot, the diameter of the cast steel shot is 1.5 mm, the shot peening intensity is set to 0.4 mmA, and a low alloy steel casting is obtained after treatment.

[0070] Example 3

[0071] A method for producing a low alloy steel casting, comprising the following raw materials in parts by weight: 97 parts of iron, 0.4 parts of carbon, 0.8 parts of silicon, 1.2 parts of manganese, 0.5 parts of chromium, and 0.5 parts of nickel;

[0072] Carbon selection coke;

[0073] Silicon is selected from silicon carbide;

[0074] Manganese selection electrolytic manganese metal;

[0075] Chromium nitride ferrochrome;

[0076] Nickel is selected from nickel iron.

[0077] Among them, a production method of low alloy steel castings includes the following steps:

[0078] S1: Melting: Iron, carbon, silicon, manganese, chromium and nickel are weighed as needed and added into a medium frequency induction furnace. The melting temperature is set at 1550°C. Deoxidation and desulfurization are performed during the melting process to obtain molten steel.

[0079] S2: Casting: Pour the molten steel into a casting mold with the mold temperature controlled at 1400°C. After cooling and molding, a steel blank is obtained.

[0080] S3: Heat treatment: The steel blank is normalized and tempered. The normalizing temperature is set at 850℃ and the holding time is 3h. The tempering temperature is set at 600℃ and the holding time is 4h to obtain the steel casting.

[0081] In some embodiments, during S1 smelting, boron and niobium are weighed and added to a medium frequency induction furnace, with a mass ratio of boron to niobium to iron of 0.003:0.003:1, with borax being the preferred material for boron and niobium being the preferred material for niobium carbide.

[0082] In some embodiments, in S1, nano-ceramic particles, graphene and carbon fibers are weighed and added to a medium-frequency induction furnace in the middle stage of smelting, the nano-ceramic particles are selected from alumina nano-particles, and the mass ratio of the nano-ceramic particles, graphene and carbon fibers to iron is 0.001:0.001:0.0015:1.

[0083] In some embodiments, in the later stage of S1 smelting, an ultrasonic oscillation device is introduced, the transducer is immersed under the surface of the molten steel and started, and the ultrasonic frequency is set to 30kHz and the power is 800W.

[0084] In some embodiments, the steel piece obtained after S2 casting is subjected to hot isostatic pressing in a static pressing furnace, with the processing temperature set at 1050° C., the pressure at 120 MPa, and the heat and pressure are maintained for 1.5 hours.

[0085] Among them, in S1 smelting, aluminum deoxidizer is used for deoxidation treatment, and the addition amount of aluminum deoxidizer is 0.04% of the weight of molten steel. Desulfurization treatment uses a mixture of calcium carbide and limestone as a desulfurizer, and the mass ratio of calcium carbide to limestone is 1:2.5. The addition amount of desulfurizer is 0.8% of the weight of molten steel.

[0086] During the S1 smelting process, a rotating magnetic field electromagnetic stirrer was used to stir the molten steel with a stirring intensity of 80A / ㎡.

[0087] In the S2 casting process, a sand mold is used as the casting mold, and the sand mold is made of resin sand, and the amount of resin added is 2% of the weight of the sand.

[0088] In some embodiments, the further processing method of the steel casting includes the following steps: introducing a shot peening machine to shot peen the steel casting, the shot peening material is cast steel shot, the diameter of the cast steel shot is 1.2 mm, the shot peening intensity is set to 0.3 mmA, and a low alloy steel casting is obtained after treatment.

[0089] Comparative Example 1: The difference between this comparative example and Example 1 is that in this comparative example, no ultrasonic oscillation device is introduced for treatment in the later stage of smelting.

[0090] Comparative Example 2: This comparative example differs from Example 1 in that boron and niobium are not added in this comparative example.

[0091] Comparative Example 3: The difference between this comparative example and Example 1 is that nano-ceramic particles, graphene and carbon fiber are not added in this comparative example.

[0092] Comparative Example 4: The difference between this comparative example and Example 1 is that the steel piece before heat treatment in this comparative example is not subjected to hot isostatic pressing treatment.

[0093] Test: The relevant performance of the products of the production methods of the low alloy steel castings of Examples 1-3 and Comparative Examples 1-4 were tested respectively.

[0094] Hardness test method: Based on GB / T230.1-2018 "Rockwell hardness test for metallic materials - Part 1: Test method", the test is carried out using a Rockwell hardness tester. The steel casting is placed on the hardness tester workbench, and the appropriate indenter and load are selected. The initial test force and the main test force are applied, and the indentation depth is measured to calculate the Rockwell hardness value.

[0095] Test location: Select 5 different locations evenly on the surface of the steel casting for testing, and take the average value as the hardness value of the steel casting.

[0096] Tensile strength test method: In accordance with GB / T228.1-2021 "Metallic Materials Tensile Tests Part 1: Room Temperature Test Methods", a universal material testing machine is used for testing. The steel casting is processed into a standard tensile specimen with a gauge length of 50 mm and a diameter of 10 mm. The specimen is clamped in the testing machine fixture and a tensile load is applied at a specified rate until the specimen breaks. The maximum load at fracture is recorded and the tensile strength is calculated.

[0097] Calculation formula: Tensile strength = maximum load ÷ original cross-sectional area of ​​the specimen

[0098] Impact toughness test method: According to GB / T229-2020 "Charpy Pendulum Impact Test Method for Metallic Materials", a Charpy impact testing machine is used for testing. The steel casting is processed into a standard impact specimen with a size of 10mm×10mm×55mm, and a V-notch is opened. The specimen is placed on the support of the impact testing machine and a pendulum with a specified energy is used to break the specimen once. The energy absorbed when the specimen breaks is measured, which is the impact toughness value.

[0099] Test temperature: room temperature (23±5)℃;

[0100] Metallographic structure analysis and testing method: According to GB / T13298-2021 "Methods for Examination of Metal Microstructures", metallographic samples of steel castings are taken. After grinding, polishing, corrosion and other treatments, the metallographic structure is observed under a metallographic microscope to analyze the grain size, morphology and distribution of various phases.

[0101] Rating standards: Rating the metallographic structure according to the relevant standard atlas, and record the test results in Table 1.

[0102] Table 1:

[0103]

[0104] By comparing and analyzing the relevant data in Table 1, it can be seen that the low-alloy steel castings produced in the present invention have high hardness, tensile strength, and impact toughness, which fully demonstrates that the product quality produced by the production method of low-alloy steel castings adopted in the present invention is good. In addition, it can be found from the data in Table 1 that the metallographic structure ratings in Examples 1-3 are all lower than those in Comparative Examples 1-4, indicating that the products produced by the production method of low-alloy steel castings adopted in the present invention have more uniform internal structure, fine grains, better material properties, fewer defects, and overall performance that is significantly better than that of traditional production methods.

[0105] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0106] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for producing low alloy steel castings, characterized in that: The low alloy steel casting is composed of the following raw materials in parts by weight: 95-98 parts of iron, 0.2-0.5 parts of carbon, 0.5-1.2 parts of silicon, 0.8-1.5 parts of manganese, 0.3-0.8 parts of chromium, and 0.2-0.6 parts of nickel; The carbon is any one or more combinations of graphite, coke and iron carbide; The silicon is any one or more combinations of ferrosilicon, silicon carbide and silicon-calcium alloy; The manganese is any one or more combinations of ferromanganese, electrolytic metallic manganese and nitride ferromanganese; The chromium is any one or more combinations of ferrochrome, ferrochrome nitride and metallic chromium; The nickel is any one or more combinations of electrolytic nickel, nickel iron and carbonyl nickel powder; The production method comprises the following steps: S1: Melting: Iron, carbon, silicon, manganese, chromium and nickel are weighed as needed and added to a medium frequency induction furnace. The melting temperature is set at 1500-1600°C. Deoxidation and desulfurization are performed during the melting process to obtain molten steel. S2: Casting: Pour the molten steel into a mold, control the mold temperature at 1350-1450℃, and cool it down to form a steel blank. S3: Heat treatment: The steel blank is subjected to normalizing and tempering treatment. The normalizing temperature is set at 800-900°C and the holding time is 2-4 hours. The tempering temperature is set at 550-650°C and the holding time is 3-5 hours to obtain a steel casting. In the S1 smelting, boron and niobium are weighed and added to a medium frequency induction furnace, wherein the mass ratio of boron to niobium to iron is 0.003:0.003:1, the boron is any one or more combinations of ferroboron, borax and boron carbide, and the niobium is any one or more combinations of ferroniobium, niobium carbide and niobium nitride; In S1, nano-ceramic particles, graphene and carbon fibers are weighed and added to a medium-frequency induction furnace in the middle stage of smelting, wherein the nano-ceramic particles are any one or more combinations of silicon carbide nanoparticles, aluminum oxide nanoparticles and boron nitride nanoparticles, and the mass ratio of the nano-ceramic particles, graphene and carbon fibers to iron is 0.001:0.001:0.0015:1; In the later stage of S1 smelting, an ultrasonic oscillation device is introduced, and the transducer is immersed under the surface of the molten steel and started, and the ultrasonic frequency is set to 20-40kHz and the power is 500-1000W; The steel piece obtained after the S2 casting is subjected to hot isostatic pressing treatment in a static pressing furnace, with the treatment temperature set at 1000-1100° C. and the pressure at 100-150 MPa, and the heat and pressure are maintained for 1-2 hours.

2. The method for producing a low alloy steel casting according to claim 1, wherein: In the S1 smelting, aluminum deoxidizer is used for deoxidation treatment, and the amount of aluminum deoxidizer added is (0.03-0.05)% of the weight of the molten steel. A mixture of calcium carbide and limestone is used as a desulfurizer for desulfurization treatment, and the mass ratio of calcium carbide to limestone is 1:(2-3), and the amount of desulfurizer added is (0.5-1)% of the weight of the molten steel.

3. The method for producing a low alloy steel casting according to claim 1, wherein: During the S1 smelting process, a rotating magnetic field electromagnetic stirrer is used to stir the molten steel, and the stirring intensity is (50-100) A / ㎡.

4. The method for producing a low alloy steel casting according to claim 1, wherein: In the S2 casting process, a sand mold is used as the casting mold, and the sand mold is resin sand, and the amount of the resin added is (1.5-2.5)% of the weight of the sand.

5. The method for producing a low alloy steel casting according to claim 1, wherein: The further processing method of the steel casting comprises the following steps: introducing a shot peening machine to perform shot peening on the steel casting, using cast steel shot as the shot peening material, the diameter of the cast steel shot is 0.5-1.5 mm, and the shot peening intensity is set to 0.2-0.4 mmA, to obtain a low alloy steel casting after treatment.

Images