Low-cost preparation method and system of high-toughness alloy steel for anti-high overload key components

Abstract

The application discloses a kind of high-toughness alloy steel low-cost preparation method and system for anti-high overload key components, and the method comprises the following steps: based on alloy element content range and performance index requirement, generate optimized alloy composition scheme;Vacuum induction melting and vacuum self-consumption remelting double vacuum melting process is used, alloy steel ingot is prepared according to the optimized alloy composition scheme;After alloy steel ingot is preheated, heat treated and short time heated, upset deformation is carried out, and alloy steel bar is generated;Alloy steel bar is prepared into key component blank by die forging or extrusion forming process, and is toughened by quenching and cyclic deep cryogenic tempering heat treatment system, and high-toughness alloy steel anti-high overload key components are obtained after precision cutting processing.The application can realize low-cost alloy composition design, so that the key components can obtain excellent strength and toughness matching and service stability under high overload working condition.

Description

Technical Field

[0001] This invention belongs to the field of alloy steel manufacturing technology, and in particular, it relates to a low-cost preparation method and system for high-strength and high-toughness alloy steel for critical components resistant to high overload. Background Technology

[0002] High-overload critical components (such as key load-bearing parts operating under high-speed impact or explosive impact environments) have extremely stringent comprehensive performance requirements for high-strength and high-toughness alloy steels. Existing preparation methods typically employ empirical proportioning and conventional melting and forging processes, which have the following significant shortcomings: First, composition design often relies on a "trial and error" approach, failing to incorporate alloy element costs into dynamic optimization models. This results in persistently high alloy costs while meeting performance constraints such as high strength (tensile strength ≥1500MPa), high plasticity (elongation after fracture ≥10%), and high impact energy (≥60J), and it is difficult to simultaneously achieve both material toughness and overload resistance. Second, traditional single-vacuum or electroslag remelting processes are insufficient to effectively remove non-metallic inclusions and gaseous elements from the steel, leading to macroscopic segregation and shrinkage defects in the ingots, directly affecting the fracture stability of critical components under high overload conditions. Third, conventional forging and heat treatment processes have limited control over microstructure uniformity, easily resulting in coarse grains or temper brittleness, failing to fully realize the strength and toughness potential of alloy steels. Summary of the Invention

[0003] The purpose of this invention is to provide a low-cost preparation method and system for high-strength and high-toughness alloy steel for critical components under high overload conditions, so as to overcome the shortcomings of the prior art, realize low-cost alloy composition design, and enable critical components to obtain excellent strength and toughness matching and service stability under high overload conditions.

[0004] One embodiment of this application provides a low-cost method for preparing high-strength and tough alloy steel for critical components resistant to high overload, the method comprising: Based on the range of alloy element content and performance requirements, a multiple regression equation for mechanical properties and chemical composition is constructed by regression analysis. Combined with the dynamic cost model of alloy elements, the lowest cost composition combination is solved under performance constraints using a global optimal algorithm to generate an optimized alloy composition scheme. A dual vacuum melting process, combining vacuum induction melting and vacuum consumable remelting, was employed to prepare high-purity alloy steel ingots with minimal segregation according to the optimized alloy composition scheme. The alloy steel ingot is preheated, homogenized, and briefly heated before being upset and drawn. The initial forging temperature and the final forging temperature are controlled to produce alloy steel bars with uniform structure. The alloy steel bar is prepared into a critical component blank by die forging or extrusion forming process. After being subjected to a heat treatment system of quenching and cyclic deep cold tempering for strengthening and toughening, and then precision machining, a high-strength and high-toughness alloy steel critical component resistant to high overload is obtained, which meets the specified plastic elongation strength, tensile strength, elongation after fracture and impact absorption energy index.

[0005] Another embodiment of this application provides a low-cost intelligent manufacturing system for high-strength and high-toughness alloy steel for critical components resistant to high overload, the system comprising: The solution module is used to construct a multiple regression equation for mechanical properties and chemical composition based on the range of alloy element content and performance requirements through regression analysis. Combined with the dynamic cost model of alloy elements, the global optimal algorithm is used to solve the lowest cost composition combination under performance constraints, and generate an optimized alloy composition scheme. The preparation module is used to prepare high-purity alloy steel ingots with little or no segregation using a dual vacuum melting process of vacuum induction melting and vacuum consumable remelting, according to the optimized alloy composition scheme. The control module is used to upset and draw the alloy steel ingot after preheating, homogenizing and short-time heating, control the initial forging temperature and the final forging temperature, and generate alloy steel bars with uniform structure. The module is used to prepare the alloy steel bar into a critical component blank by die forging or extrusion forming process, and to perform a toughening treatment by quenching and cyclic deep cold tempering. After precision machining, a high-strength and tough alloy steel critical component resistant to high overload is obtained, which meets the specified plastic elongation strength, tensile strength, elongation after fracture and impact absorption energy index.

[0006] Another embodiment of this application provides a storage medium storing a computer program, wherein the computer program is configured to execute the method described in any of the preceding claims when running.

[0007] Another embodiment of this application provides an electronic device including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the method described in any of the preceding claims.

[0008] Compared with existing technologies, this invention enables low-cost alloy composition design, allowing critical components to achieve excellent strength-toughness matching and service stability under high overload conditions. Attached Figure Description

[0009] Figure 1 The hardware structure block diagram of a computer terminal for a low-cost preparation method of high-strength and tough alloy steel for high-overload resistant critical components provided in this embodiment of the invention; Figure 2A schematic flowchart illustrating a low-cost preparation method for high-strength and high-toughness alloy steel for critical components resistant to high overload, provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a low-cost intelligent manufacturing system for high-strength and high-toughness alloy steel for critical components resistant to high overload, provided in an embodiment of the present invention. Detailed Implementation

[0010] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0011] The present invention first provides a low-cost preparation method for high-strength and high-toughness alloy steel for critical components resistant to high overload. This method can be applied to electronic devices, such as computer terminals, specifically ordinary computers.

[0012] The following detailed explanation uses a computer terminal as an example.

[0013] Figure 1 This is a hardware structure block diagram of a computer terminal for a low-cost preparation method of high-strength and tough alloy steel for critical components resistant to high overload, provided as an embodiment of the present invention. Figure 1 As shown, the computer device includes a processor, memory, and network interface connected via a system bus, wherein the memory may include non-volatile storage media and internal memory.

[0014] See Figure 2 The present invention provides a low-cost method for preparing high-strength and high-toughness alloy steel for critical components resistant to high overload, which may include the following steps: S201, based on the range of alloy element content and performance index requirements, constructs a multiple regression equation for mechanical properties and chemical composition through regression analysis, combines the dynamic cost model of alloy elements, and uses a global optimal algorithm to solve the lowest cost composition combination under performance constraints to generate an optimized alloy composition scheme; Specifically, the range of alloy element content and performance index requirements can be determined, each chemical element can be used as an input factor, and the four mechanical properties of plastic extension strength, tensile strength, elongation after fracture and impact absorption energy can be used as the output response to generate factor and response datasets. The core of this step is to clarify the input factors and output response for preparing high-strength and high-toughness alloy steel, define the reasonable range of element content and performance indicators, collect and integrate experimental data to generate a basic dataset for subsequent construction of regression equations, and provide accurate data support for mechanical property prediction and cost optimization. The specific implementation method is as follows: First, the core alloying elements of high-strength and high-toughness alloy steel for critical components resistant to high overloads were identified. Based on the requirements for strengthening and toughening, the main input factors were determined to be eight chemical elements: chromium (Cr), cobalt (Co), molybdenum (Mo), vanadium (V), manganese (Mn), niobium (Nb), boron (B), and nickel (Ni). These elements directly affect the hardenability, strength, toughness, and hardness of the alloy steel, and are the core factors determining its mechanical properties. The content range of each element was determined through preliminary experiments and industry standard optimization, using mass percentage (%) as the unit, with an accuracy controlled within 0.01% to ensure the accuracy and controllability of the element content. Specific content ranges are as follows: Chromium (Cr) 10.0%-12.0%, mainly to improve the corrosion resistance and strength of the alloy steel; Cobalt (Co) 8.0%-10.0%, which can improve the high-temperature strength and toughness of the alloy steel; Molybdenum (Mo) 2.5%-3.5%, which can refine the alloy steel... Vanadium (V) 0.8%-1.2% can form carbides, enhancing wear resistance and strength; Manganese (Mn) 1.0%-1.5% improves the toughness and forgeability of steel; Niobium (Nb) 0.15%-0.25% refines the grains, improving strength and toughness; Boron (B) 0.002%-0.005% improves hardenability and reduces the dependence of hardenability on carbon content; Nickel (Ni) 3.0%-5.0% improves the low-temperature toughness and plasticity of alloy steel.

[0015] Secondly, the requirements for the output response of four mechanical properties are clearly defined. In combination with the usage requirements of critical components that can withstand high overloads, it is stipulated that the plastic extension strength shall not be less than 1750 MPa, the tensile strength shall not be less than 2000 MPa, the elongation after fracture shall not be less than 20%, and the impact absorption energy shall not be less than 75 joules (J). These indicators are the core requirements to ensure that critical components can withstand high overloads and avoid fracture failure. The units are clearly marked, and the accuracy is controlled as follows: the accuracy of plastic extension strength and tensile strength is 1 MPa, the accuracy of elongation after fracture is 0.1%, and the accuracy of impact absorption energy is 1 J.

[0016] To generate the factor and response dataset, a combination of single-factor variable method and orthogonal experimental design was used. A total of 50 experimental samples with different element content combinations were designed. Each sample was prepared, melted, forged, and heat-treated strictly according to the set element content range to ensure consistency in sample preparation. After the experiment, the mechanical properties of each sample were tested. Tensile tests were used to measure the specified plastic extension strength, tensile strength, and elongation after fracture, and impact tests were used to measure the impact absorption energy. The actual contents of eight elements (input factors) and the test results of four mechanical properties (output response) for each sample were recorded to form the raw experimental data.

[0017] The original experimental data were cleaned and verified, and outlier data (such as samples whose performance data deviated from the reasonable range due to smelting defects or testing errors) were removed. Finally, 45 sets of valid data were retained and integrated to generate factor and response datasets. Each sample in the dataset corresponds to one data record, labeled with the sample number, the actual content of the eight elements (unit: %), the specified plastic extension strength (unit: MPa), the tensile strength (unit: MPa), the elongation after fracture (unit: %), and the impact energy (unit: J). The format was standardized to ensure accurate retrieval for subsequent multiple regression analysis. For example, a data record might be: Sample number-001, Cr-11.0%, Co-9.0%, Mo-3.0%, V-1.0%, Mn-1.2%, Nb-0.2%, B-0.003%, Ni-4.0%, specified plastic extension strength-1780MPa, tensile strength-2050MPa, elongation after fracture-22%, impact energy-80J.

[0018] Based on the factor and response dataset, the regression equations of four mechanical properties and chemical composition were fitted by the multivariate regression analysis method to obtain the regression equations of specified plastic extension strength, tensile strength, elongation after fracture and impact absorption energy, and to generate a set of mechanical property prediction models. The core of this step is to establish a quantitative relationship between the content of alloying elements and four mechanical properties through multiple regression analysis, generate regression equations that can accurately predict mechanical properties, and form a set of mechanical property prediction models. This provides a basis for performance constraints in subsequent cost optimization. The specific implementation method is as follows: Multiple regression analysis is a statistical analysis method used to analyze the linear or nonlinear relationship between multiple input variables and one output variable. Its core logic is to fit a regression equation between the input factors (alloy element content) and the output response (mechanical properties) using the least squares method, minimizing the error between the predicted value and the experimentally measured value, thus ensuring the accuracy of the regression equation's prediction. This study uses linear multiple regression analysis because experimental data show a significant linear correlation between alloy element content and mechanical properties, with correlation coefficients (R²) all greater than 0.9, which meets the prediction requirements.

[0019] During the fitting process, the content (mass percentage) of eight alloying elements was used as the independent variable, and the specified plastic extension strength, tensile strength, elongation after fracture, and impact absorption energy were used as the dependent variables. Based on 45 sets of valid data in the factor and response dataset, the least squares method was used to fit the multiple regression equations of the four mechanical properties. Each equation includes a constant term and a coefficient term for the content of each element. The coefficient term represents the degree of influence of the corresponding element on the mechanical property. A positive coefficient indicates that an increase in the element content will improve the property, and a negative coefficient indicates that an increase in the element content will decrease the property.

[0020] The regression equations in the example are as follows: The regression equation for plastic elongation strength is specified as follows: σ_s = 1200 + 35 × Cr + 28 × Co + 42 × Mo + 55 × V + 15 × Mn + 80 × Nb + 1200 × B + 22 × Ni, where σ_s represents the specified plastic elongation strength (unit: MPa), Cr, Co, etc. represent the mass percentage of the corresponding elements, the constant term 1200 is the basic strength value, and the coefficients of each element represent the numerical increase in plastic elongation strength for every 1% increase in the content of that element. For example, the coefficient for Nb is 80, meaning that for every 1% increase in Nb content, the specified plastic elongation strength increases by 80 MPa. The tensile strength regression equation is... σ_b = 1450 + 40 × Cr + 32 × Co + 48 × Mo + 60 × V + 18 × Mn + 90 × Nb + 1500 × B + 25 × Ni, where σ_b represents tensile strength (unit: MPa). The regression equation for elongation after fracture is: δ=12+0.8×Cr+1.2×Co+0.5×Mo+0.3×V+1.5×Mn+0.6×Nb+5×B+1.0×Ni, Where δ represents elongation after fracture (unit: %); the regression equation for impact absorption energy is: A_k = 45 + 2.5 × Cr + 3.0 × Co + 2.0 × Mo + 1.8 × V + 2.2 × Mn + 4.0 × Nb + 30 × B + 2.8 × Ni, where A_k represents the impact absorption energy (unit: J).

[0021] After fitting, the accuracy of each regression equation was verified by calculating the coefficient of determination (R²) and root mean square error (RMSE). R² measures the goodness of fit, while RMSE measures the deviation between predicted and measured values. Verification showed that the R² of all four mechanical property regression equations was greater than 0.92, and the RMSE values ​​were as follows: plastic extension strength ≤ 15 MPa, tensile strength ≤ 18 MPa, elongation after fracture ≤ 0.8%, and impact absorption energy ≤ 3 J. The fitting accuracy met the requirements and can be used for subsequent mechanical property prediction. These four regression equations were integrated to generate a mechanical property prediction model set. The model set clearly defines the expression, independent variables, dependent variables, coefficient meanings, and fitting accuracy of each regression equation, providing a clear basis for the performance constraints of subsequent cost optimization.

[0022] Based on the correspondence between the unit price of alloy materials and the percentage parameters of element content, a dynamic cost equation for alloy elements is constructed. The percentage parameters of each element are substituted into the material alloy cost formula and summed to generate a dynamic cost objective function. The core of this step is to establish a quantitative relationship between the content of alloying elements and the preparation cost, construct a dynamic cost equation and objective function, clarify the goal of cost optimization, and provide optimization direction for subsequent global optimization. The specific implementation method is as follows: The construction of the dynamic cost equation for alloy elements is based on the real-time unit price of alloy materials and the percentage content of each element. The core logic is to multiply the amount of each alloy element by its corresponding unit price, and then add up the costs of all elements to obtain the production cost of alloy steel per unit mass. The unit price of alloy materials adopts the real-time market price, in kilograms (kg), with an accuracy controlled at 0.1 yuan / kg. It can be dynamically updated according to market price fluctuations to ensure the accuracy of cost calculation.

[0023] First, let's clarify the unit price examples for the eight alloying elements. Based on the current market conditions, the unit prices for each material are as follows: Ferrochrome alloy (containing 70% Cr) is 8500 yuan / kg, Cobalt plate (containing 99.9% Co) is 68000 yuan / kg, Ferromolybdenum alloy (containing 60% Mo) is 32000 yuan / kg, Ferrovanadium alloy (containing 50% V) is 45000 yuan / kg, Metallic manganese (containing 99.5% Mn) is 1800 yuan / kg, Ferroniobium alloy (containing 60% Nb) is 52000 yuan / kg, Ferroboron alloy (containing 10% B) is 12000 yuan / kg, and Electrolytic nickel plate (containing 99.9% Ni) is 18000 yuan / kg. Based on the purity of the material, calculate the actual unit price of each element. For example, the actual unit price of chromium = unit price of ferrochrome alloy ÷ purity = 8500 ÷ 70% ≈ 12142.86 yuan / kg. The other elements are calculated in the same way to obtain the actual unit price of each element.

[0024] Subsequently, a dynamic cost equation for alloying elements is constructed. Let the mass percentages of each element in a unit mass (1 kg) of alloy steel be x1 (Cr), x2 (Co), x3 (Mo), x4 (V), x5 (Mn), x6 (Nb), x7 (B), and x8 (Ni), and the actual unit prices of each element be p1, p2, p3, p4, p5, p6, p7, and p8 (unit: yuan / kg). Then, the dynamic cost equation is C = x1×p1 + x2×p2 + x3×p3 + x4×p4 + x5×p5 + x6×p6 + x7×p7 + x8×p8, where C represents the preparation cost of a unit mass of alloy steel (unit: yuan / kg), and x1 to x8 are all decimals between 0 and 1 (corresponding to mass percentages), and satisfy x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 ≤ 100% (the rest are iron elements, and the unit price of iron elements is low and can be ignored).

[0025] Substituting the actual unit price of each element into the dynamic cost equation generates a specific cost expression. In the example, the cost equation is: C = 12142.86x1 + 68000x2 + 53333.33x3 + 90000x4 + 1809.02x5 + 86666.67x6 + 120000x7 + 18000x8, where x1 to x8 correspond to the mass percentages of Cr, Co, Mo, V, Mn, Nb, B, and Ni, respectively (e.g., x1 = 0.11 indicates that the Cr content is 11%).

[0026] Using this dynamic cost equation as the objective function for cost optimization, the optimization objective is to minimize the production cost C per unit mass of alloy steel, i.e., the objective function is: minC = 12142.86x1 + 68000x2 + 53333.33x3 + 90000x4 + 1809.02x5 + 86666.67x6 + 120000x7 + 18000x8. This objective function clearly defines the relationship between cost and the content of each element, providing a clear optimization direction for subsequent global optimization under performance constraints.

[0027] Using the set of mechanical property prediction models as performance constraints and the dynamic cost objective function as the optimization objective, the Globalsearch global optimal algorithm is used to perform global optimization within the upper and lower limits of the composition variables, and outputs the alloy composition optimization scheme that meets the performance requirements and has the lowest cost.

[0028] The core of this step is to use the Globalsearch global optimal algorithm to find the alloy composition combination with the lowest cost under the dual constraints of upper and lower limits of alloy element content and mechanical performance indicators, thereby achieving the optimal balance between performance and cost and generating the final optimized alloy composition scheme. The specific implementation method is as follows: Globalsearch is an optimization algorithm based on a global search strategy. Its core logic is to find the global optimum of the objective function within a predefined range of variables by combining traversal and local optimization, avoiding getting trapped in local optima and ensuring the rationality and optimality of the optimization results. This algorithm is suitable for optimization problems with multiple variables and constraints. In this study, it was used to solve for the lowest-cost alloy composition combination under mechanical performance constraints. The algorithm's convergence accuracy was controlled at 0.01% (elemental content accuracy) and 1 yuan / kg (cost accuracy) to ensure the accuracy of the optimization results.

[0029] First, clarify the constraints for optimization, including compositional variable constraints and mechanical property constraints. Compositional variable constraints refer to the content range of each alloying element, which is the mass percentage range of the eight elements determined in step one, namely x1∈[0.10,0.12], x2∈[0.08,0.10], x3∈[0.025,0.035], x4∈[0.008,0.012], x5∈[0.01,0.015], x6∈[0.0015,0.0025], x7∈[0.00002,0.00005], x8∈[…]. [0.03, 0.05], while satisfying x1+x2+x3+x4+x5+x6+x7+x8≤0.25 (the rest are iron elements); the mechanical property constraints are the mechanical property prediction model set generated in step two, which requires the predicted specified plastic extension strength σ_s≥1750MPa, tensile strength σ_b≥2000MPa, elongation after fracture δ≥20%, and impact absorption energy A_k≥75J. Substituting the four regression equations into the constraint conditions forms specific inequality constraints.

[0030] During the optimization process, the dynamic cost objective function minC is used as the optimization objective, and the composition variable constraints and mechanical property constraints are used as constraints. The optimization parameters of the algorithm are set as follows: 1000 iterations, a search step size of 0.001 (element content step size), and a convergence threshold of 0.01%, ensuring that the algorithm can fully search the entire variable space and find the global optimum. The algorithm first randomly generates several initial solutions within the range of composition variables, calculates the cost and mechanical property prediction values ​​corresponding to each initial solution, and selects feasible solutions that meet the mechanical property constraints. Then, it performs local optimization on the feasible solutions, iteratively adjusting the content of each element to reduce the cost while ensuring that the mechanical property constraints are always met. After iterating to the convergence threshold, the feasible solution with the lowest cost is output, which is the optimal alloy composition combination.

[0031] In the example, after optimization using the Globalsearch global optimization algorithm, the output alloy composition optimization scheme is as follows: Cr-10.5%, Co-8.0%, Mo-2.5%, V-0.8%, Mn-1.5%, Nb-0.15%, B-0.002%, Ni-3.0%. The production cost per unit mass of alloy steel at this point is... C≈12142.86×0.105+68000×0.08+53333.33×0.025+90000×0.008+1809.02×0.015+86666.67×0.0015+120000×0.00002+18000×0.03≈9467.87 yuan / kg.

[0032] Predicting the mechanical properties of this optimal component combination and substituting it into the regression equation from step two yields the specified plastic elongation strength. σ_s = 1200 + 35 × 10.5 + 28 × 8.0 + 42 × 2.5 + 55 × 0.8 + 15 × 1.5 + 80 × 0.15 + 1200 × 0.002 + 22 × 3.0 = 1743.4 MPa, close to 1750 MPa. After adjusting the Co content to 8.2% and recalculating, σ_s = 1750.8 MPa, which meets the constraint requirements; tensile strength σ_b = 1450 + 40 × 10.5 + 32 × 8.2 + 48 × 2.5 + 60 × 0.8 + 18 × 1.5 + 90 × 0.15 + 1500 × 0.002 + 25 × 3.0 = 2018.9 MPa ≥ 2000 MPa; Elongation after fracture δ=12+0.8×10.5+1.2×8.2+0.5×2.5+0.3×0.8+1.5×1.5+0.6×0.15+5×0.002+1.0×3.0=36.88%≥20%; Impact Absorption Energy A_k = 45 + 2.5 × 10.5 + 3.0 × 8.2 + 2.0 × 2.5 + 1.8 × 0.8 + 2.2 × 1.5 + 4.0 × 0.15 + 30 × 0.002 + 2.8 × 3.0 = 94.65 J ≥ 75 J. All mechanical properties meet the requirements, and the cost is minimized. Finally, this composition combination is compiled into an optimized alloy composition scheme, clarifying the mass percentage of each element, the corresponding predicted mechanical properties, and the unit cost, ensuring that the scheme can be directly used in subsequent smelting processes.

[0033] S202, using a dual vacuum melting process of vacuum induction melting and vacuum consumable remelting, high-purity alloy steel ingots with little or no segregation are prepared according to the optimized alloy composition scheme. Specifically, the proportions of each alloy material can be calculated based on the optimized alloy composition scheme, including ferrochrome alloy, cobalt plate, ferromolybdenum alloy, ferrovanadium alloy, metallic manganese, ferroniobium alloy, ferroboron alloy, electrolytic nickel plate, and carbon raiser, to generate a material proportion list. The core of this step is to convert the optimized alloy composition scheme into a material ratio that can be directly used for smelting. Based on the purity and elemental content of each material, the weighing amount of each material is accurately calculated to ensure that the composition of the alloy steel after smelting meets the optimization requirements, while taking into account cost control and smelting feasibility. The specific implementation method is as follows: The optimized alloy composition scheme is the core basis for the proportioning calculation. It clarifies the target mass percentage of each alloying element. Combined with the previous global optimization results, the optimized alloy composition (mass percentage) in the example is: Cr-10.5%, Co-8.2%, Mo-2.5%, V-0.8%, Mn-1.5%, Nb-0.15%, B-0.002%, Ni-3.0%. The carbon (C) content is controlled at 0.35%-0.45% (adjusted by a carbon raiser), and the remainder is iron (Fe). This composition scheme can meet the mechanical performance requirements and has the lowest cost.

[0034] The core logic of the proportioning calculation is to calculate the required mass of materials based on the effective element purity of each material, ensuring that the actual amount of each element added is consistent with the target content. The calculation formula is: Material weighing amount = (target element content × total smelting mass) ÷ (purity of the element in the material). The total smelting mass is set according to production needs. In the example, the total smelting mass for a single batch is set to 500 kg, with an accuracy control of 0.1 kg to ensure weighing accuracy.

[0035] The following is an example of calculating the purity and proportion of each material: For the ferrochrome alloy, a material containing 70% Cr is selected, with a purity of 70% (i.e., 0.7%). The target Cr content is 10.5%. Therefore, the weight of the ferrochrome alloy is (500kg × 10.5%) ÷ 70% = (52.5kg) ÷ 0.7 = 75kg. This calculation ensures that the added Cr element mass is 52.5kg, which meets the target content. For the cobalt plate, a material containing 99.9% Co is selected, with a purity of 99.9% (i.e., 0.999%). The target Co content is 8.2%. Therefore, the weight of the cobalt plate is (500kg × 8.2%) ÷ 99.9% ≈ 41kg. g ÷ 0.999 ≈ 41.04 kg; The ferromolybdenum alloy uses material containing 60% Mo with a purity of 60% (i.e., 0.6%), and the target Mo content is 2.5%. Therefore, the weight of the ferromolybdenum alloy is (500 kg × 2.5%) ÷ 60% = 12.5 kg ÷ 0.6 ≈ 20.83 kg; The ferrovanadium alloy uses material containing 50% V with a purity of 50% (i.e., 0.5%), and the target V content is 0.8%. Therefore, the weight of the ferrovanadium alloy is (500 kg × 0.8%) ÷ 50% = 4 kg ÷ 0.5 = 8 kg; The metallic manganese uses material containing 99.5% Mn with a purity of 99.5% (i.e., g ÷ 0.999 ≈ 41.04 kg). For the ferroniobium alloy, the target Mn content is 1.5%, so the amount of manganese metal weighed is (500kg × 1.5%) ÷ 99.5% = 7.5kg ÷ 0.995 ≈ 7.54kg; For the ferroniobium alloy, the material containing 60% Nb is selected, with a purity of 60% (i.e., 0.6%), and the target Nb content is 0.15%, so the amount of ferroniobium alloy weighed is (500kg × 0.15%) ÷ 60% = 0.75kg ÷ 0.6 = 1.25kg; For the ferroboron alloy, the material containing 10% B is selected, with a purity of 10% (i.e., 0.1%), and the target B content is 0.002%, so the amount of ferroboron alloy weighed is (500kg × 1.5%) ÷ 99.5% = 7.5kg ÷ 0.995 ≈ 7.54kg. (500kg × 0.002%) ÷ 10% = 0.01kg ÷ 0.1 = 0.1kg; The electrolytic nickel plate uses material containing 99.9% Ni, with a purity of 99.9% (i.e., 0.999), and a target Ni content of 3.0%. Therefore, the weight of the electrolytic nickel plate is (500kg × 3.0%) ÷ 99.9% = 15kg ÷ 0.999 ≈ 15.02kg; The carbon recarburizer uses material containing 98% C, with a purity of 98% (i.e., 0.98), and a target C content of 0.4%. Therefore, the weight of the carbon recarburizer is (500kg × 0.4%) ÷ 98% = 2kg ÷ 0.98 ≈ 2.04kg.

[0036] After the calculation is completed, the weight of each material is checked to verify whether the total mass of all materials is close to 500 kg. At the same time, the actual amount of each element added is checked to ensure that the deviation from the target content is within ±0.05%, thus ensuring accurate proportioning. In the example, the total mass of all materials is approximately 75 + 41.04 + 20.83 + 8 + 7.54 + 1.25 + 0.1 + 15.02 + 2.04 ≈ 170.78 kg. The remainder is iron, with a mass of approximately 500 - 170.78 ≈ 329.22 kg. The iron used is pure iron (containing 99.9% Fe), and after replenishment, the total mass is exactly 500 kg. All material names, purity, target element content, and weighing volume (unit: kg) are compiled and integrated to generate a material ratio list. The list clearly indicates the order of use and precautions for each material (e.g., ferroborone alloy is easily oxidized and should be added last) to ensure that subsequent weighing and smelting operations are carried out in an orderly manner. The material ratio list in the example contains the following: ferrochrome alloy (70%Cr) 75.00kg, cobalt plate (99.9%Co) 41.04kg, ferromolybdenum alloy (60%Mo) 20.83kg, ferrovanadium alloy (50%V) 8.00kg, metallic manganese (99.5%Mn) 7.54kg, ferroniobium alloy (60%Nb) 1.25kg, ferroborone alloy (10%B) 0.10kg, electrolytic nickel plate (99.9%Ni) 15.02kg, carbon raiser (98%C) 2.04kg, and pure iron (99.9%Fe) 329.22kg.

[0037] The furnace charge weighed according to the material ratio list is loaded into the vacuum induction melting furnace and induction melting is carried out under vacuum conditions. The alloy elements are evenly distributed by electromagnetic stirring, and harmful impurities and gases are removed by slag making and vacuum degassing processes to generate vacuum induction melting ingots. The core of this step is to melt the proportioned furnace charge into a liquid alloy using a vacuum induction melting process, while simultaneously removing harmful impurities and gases to ensure the purity of the liquid alloy. Electromagnetic stirring ensures uniform element distribution, laying the foundation for subsequent vacuum arc remelting. The specific implementation method is as follows: Vacuum induction melting furnaces are core equipment for melting and preliminary purification of furnace charge. Their core principle is to use eddy currents generated by electromagnetic induction to heat the charge, causing it to melt rapidly. Simultaneously, the vacuum environment reduces gas and impurity contamination. The vacuum level can be precisely controlled during the melting process to ensure optimal melting results. Before operation, the vacuum induction melting furnace must be pre-treated, checking the furnace body's sealing, the integrity of the induction coil, and the stability of the cooling system to prevent leaks, coil damage, and other problems that could affect the melting quality.

[0038] The weighing of the furnace charge must be strictly carried out according to the material proportioning list, using an electronic balance with an accuracy of 0.01 kg. The entire weighing process must be conducted in a clean environment to avoid contamination of the furnace charge with dust, oil, or other impurities. After weighing, the charge is loaded into the crucible of the vacuum induction melting furnace in the order of "heaviest first, then lightest; most refractory first, then most fusible," specifically: pure iron → ferrochrome alloy → ferromolybdenum alloy → ferrovanadium alloy → ferroniobium alloy → electrolytic nickel plate → cobalt plate → metallic manganese → carbon raiser → ferroboron alloy. Ferroboron alloy and carbon raiser are easily oxidized and volatile, and should be added after most of the furnace charge has melted to avoid element loss.

[0039] After the furnace charge is loaded, the furnace body is closed, and the vacuum system is activated to evacuate the furnace to a vacuum level of 1.0 × 10⁻³ Pa. This vacuum level effectively reduces the content of gases such as oxygen, nitrogen, and hydrogen in the furnace, preventing reactions between the gases and the molten alloy that could cause defects such as porosity. The vacuum level is precisely controlled at 1.0 × 10⁻⁴ Pa to ensure a stable vacuum environment. Subsequently, the induction heating system is activated, and the power is gradually increased, with the heating rate controlled at 50 °C / min. This prevents excessively rapid heating that could lead to localized overheating of the furnace charge and damage to the crucible, while also preventing excessive element volatilization.

[0040] When the furnace charge temperature reaches 1500-1550℃, the charge is completely melted into a liquid alloy. At this point, the electromagnetic stirring system is activated. The principle of electromagnetic stirring is to use the alternating magnetic field generated by the induction coil to drive the liquid alloy to rotate and flow, ensuring a uniform distribution of alloying elements and preventing compositional segregation. The stirring speed is controlled at 300 r / min, and the stirring time is 20 min. During the stirring process, the temperature of the liquid alloy is monitored in real time and kept stable at around 1520℃ to ensure effective stirring while preventing excessive temperature from causing element volatilization.

[0041] To remove harmful impurities (such as sulfur, phosphorus, and oxides) from the molten alloy, a slag-forming process is employed. A slag-forming agent is added to the molten alloy. The agent is a mixture of calcium carbonate (CaCO3) and calcium fluoride (CaF2) in a 3:1 ratio, and the amount added is 0.8% of the total mass of the molten alloy, i.e., 500kg × 0.8% = 4kg. After the slag-forming agent is added, it reacts chemically with the harmful impurities in the molten alloy to generate slag with a density less than the molten alloy. This slag floats on the surface of the molten alloy and is then removed using a slag-skimming device, ensuring the purity of the molten alloy.

[0042] Vacuum degassing is performed simultaneously. During induction melting and electromagnetic stirring, gases such as hydrogen and nitrogen in the molten alloy gradually precipitate out under vacuum and are discharged from the furnace through the vacuum system. The degassing time is 30 minutes. During degassing, the temperature of the molten alloy is controlled at 1520-1530℃. Too high a temperature will cause the molten alloy to volatilize, while too low a temperature will affect the gas precipitation efficiency. After degassing, the composition of the molten alloy is analyzed using a spectrometer to detect the content of each element, ensuring that the element content meets the requirements of the optimized scheme. If the content of a certain element deviates beyond the allowable range, the corresponding material is added to adjust it.

[0043] After the composition test is passed, the molten alloy is poured into a mold preheated to 800℃. Preheating is to prevent the molten alloy from cooling too quickly due to a low mold temperature, which could cause defects such as cracks and shrinkage cavities. The mold is made of graphite, which is characterized by high temperature resistance and good thermal conductivity. After the molten alloy is poured in, it is allowed to cool naturally to room temperature. Upon demolding, a vacuum induction melting ingot is obtained. The ingot has a diameter of 300mm, a length of 1200mm, and a weight of approximately 500kg. The ingot surface is free of obvious cracks, pores, inclusions, and other defects, and the internal composition is uniform, preparing it for subsequent vacuum arc remelting.

[0044] Vacuum induction melting ingots are used as consumable electrodes and loaded into a vacuum consumable remelting furnace. Under vacuum conditions, the electrodes are gradually melted by electric arc heating and dripped into a water-cooled crystallizer for rapid solidification, which further reduces the content of oxygen, nitrogen, and hydrogen gases as well as harmful impurities such as sulfur and phosphorus, thus generating vacuum consumable remelting ingots. The core of this step is to use a vacuum arc remelting process to perform secondary purification and solidification on the vacuum induction melting ingot, further reducing the content of gases and harmful impurities, refining the grains, reducing component segregation, and obtaining an alloy ingot with higher purity. The specific implementation method is as follows: The core function of a vacuum arc remelting furnace is to gradually melt the consumable electrode (vacuum induction melting ingot) through arc heating. The molten alloy droplets then drip into a water-cooled crystallizer under vacuum and solidify rapidly, achieving secondary purification and uniform solidification. Its key advantages are that the vacuum environment can further remove gaseous impurities, and rapid solidification can refine grains and reduce segregation. Before operation, a comprehensive inspection of the vacuum arc remelting furnace is required, including the integrity of the electrode clamping device, arc generator, water cooling system, and vacuum system, to ensure a smooth remelting process.

[0045] First, the vacuum induction melting ingot is pretreated to remove oxide scale, inclusions, and surface defects from the ingot surface. Mechanical grinding is used to control the surface roughness to Ra≤1.6μm after grinding, preventing surface defects from affecting the ingot quality during remelting. Then, the pretreated vacuum induction melting ingot is used as a consumable electrode and fixed to the top of the vacuum consumable remelting furnace using an electrode clamping device. The electrode axis is adjusted to coincide with the axis of the water-cooled crystallizer, with a deviation not exceeding 0.5mm, ensuring that the alloy droplets accurately drip to the center of the crystallizer.

[0046] The furnace body is closed, and the vacuum system is activated to evacuate the furnace to a vacuum level of 5.0×10^-4 Pa. This vacuum level is higher than that of vacuum induction melting, which can more effectively remove gaseous impurities (oxygen, nitrogen, hydrogen) from the alloy liquid, especially hydrogen, ensuring that there are no porosity defects inside the ingot. The vacuum level remains stable throughout the process, with fluctuations not exceeding ±1.0×10^-4 Pa.

[0047] The arc generator is started, and the arc voltage is adjusted to 35V and the current to 8000A. The high temperature generated by the arc heats the bottom of the consumable electrode, causing the electrode to gradually melt. The melting rate is controlled at 2.5kg / min. If the melting rate is too fast, the alloy droplets will not have enough time to degas, and impurities cannot be effectively removed; if the melting rate is too slow, production efficiency will be reduced and energy consumption will be increased. After the consumable electrode melts, the alloy droplets fall under the action of gravity. During the dripping process, further degassing occurs in a vacuum environment, and at the same time, it reacts with the trace amounts of oxygen remaining in the furnace. The resulting oxide impurities float on the surface of the alloy liquid, forming secondary slag.

[0048] The water-cooled crystallizer is the core component for achieving rapid solidification of the alloy liquid. The crystallizer is made of copper and has internal cooling water channels. The cooling water flow rate is controlled at 15m / s and the cooling water temperature is controlled at 25-30℃. Through continuous cooling, the dripping alloy liquid is rapidly solidified at a solidification rate of 10mm / min. Rapid solidification can refine the grains, keeping the grain size below 50μm, while reducing component segregation and ensuring uniform internal structure of the ingot.

[0049] During the remelting process, parameters such as arc voltage, current, vacuum level, and cooling water temperature are monitored in real time to ensure stability. Simultaneously, the dripping state of the molten alloy and the solidification of the ingot within the crystallizer are observed periodically to prevent issues such as arc interruption and leakage. The remelting process lasts approximately 200 minutes. When the consumable electrode is completely melted and the ingot in the crystallizer reaches the preset dimensions (320mm diameter, 1300mm length), arc heating is stopped. The vacuum environment is maintained, allowing the ingot to cool to below 500℃ under vacuum conditions to prevent rapid cooling that could generate thermal stress and cause cracking.

[0050] After cooling, the furnace body is opened, and the vacuum self-consumable remelting ingot is taken out. The ingot is then inspected for surface and composition. The surface is free of defects such as cracks, pores, and inclusions. The internal gas content is controlled at: oxygen ≤20ppm, nitrogen ≤30ppm, hydrogen ≤2ppm, sulfur ≤0.005%, and phosphorus ≤0.003%. Compared with the vacuum induction melting ingot, the gas and impurity content is significantly reduced, and the purity is significantly improved, meeting the requirements for high-purity alloy steel ingots.

[0051] By implementing fine-grain solidification process control on vacuum consumable remelting ingots and adjusting the droplet rate and the cooling intensity of the crystallizer to reduce the temperature gradient between the edge and the core, high-purity alloy steel ingots with little segregation and uniform fine grains are obtained, which are secondary hardened high-strength steel base materials.

[0052] The core of this step is to further optimize the grain size and compositional uniformity of the vacuum arc remelting ingot through fine-grain solidification process control, reduce the temperature gradient between the edge and the core, reduce segregation, and obtain a fine-grained, uniform, and high-purity alloy steel ingot as the base material for subsequent forging. The specific implementation method is as follows: The core principle of fine-grained solidification process control is to adjust the droplet rate and the cooling intensity of the crystallizer to control the solidification rate and temperature gradient of the alloy liquid, thereby avoiding grain growth and compositional segregation and achieving fine-grained uniform solidification. The temperature gradient is the main cause of compositional segregation and grain size differences between the ingot's edge and core. Faster cooling at the edges results in finer grains, while slower cooling at the core leads to coarser grains. By optimizing process parameters, the temperature gradient can be reduced, making the grain size and composition of the ingot's edge and core more consistent.

[0053] First, the droplet rate is adjusted. The droplet rate is directly related to the melting speed of the consumable electrode. By adjusting the arc current and voltage, the droplet rate is controlled at 2.0-2.2 kg / min, slightly lower than the melting speed in step three. A slower droplet rate allows for sufficient degassing of the alloy droplets during the droplet's descent, while also ensuring uniform spreading of the alloy liquid within the crystallizer, preventing excessively high temperatures caused by localized accumulation and reducing grain growth. The droplet rate is adjusted with a precision of 0.1 kg / min, monitored and adjusted in real time to ensure rate stability.

[0054] Secondly, adjust the cooling intensity of the crystallizer. Cooling intensity is achieved by adjusting the cooling water flow rate and temperature. Increase the cooling water flow rate from 15 m / s to 18 m / s, and control the cooling water temperature at 22-25℃. This increases the cooling intensity and accelerates the cooling rate at the edges of the ingot. Simultaneously, guide channels are installed on the inner wall of the crystallizer to ensure uniform cooling water distribution and avoid excessive temperature gradients caused by uneven cooling in certain areas. The adjustment of cooling intensity must be gradual to avoid sudden changes that could lead to cracks in the ingot.

[0055] To further reduce the temperature gradient, a heat-insulating jacket is used simultaneously for temperature control during the vacuum arc remelting process. The heat-insulating jacket is placed on the outside of the crystallizer, 50mm away from the crystallizer wall. The heat-insulating jacket is made of high-temperature resistant insulation material, which can reduce heat loss from the edge of the ingot and keep the temperature difference between the edge and the core of the ingot within 50℃, with a temperature difference accuracy of ±5℃. The temperature of the edge and core of the ingot is monitored in real time by temperature sensors, and the cooling intensity and droplet rate are adjusted in real time to ensure that the temperature gradient is stable within a reasonable range.

[0056] During the fine-grain solidification process control, the solidification state of the ingot is monitored simultaneously. Ultrasonic testing technology is used to detect the grain size and composition distribution inside the ingot in real time. The grain size is controlled within 30-50 μm, the uniformity deviation does not exceed 10%, and the compositional segregation is controlled within ±0.03%, ensuring that the internal structure of the ingot is uniform and the composition is consistent. If the grain size is found to be too large or the compositional segregation exceeds the allowable range, the droplet rate and cooling intensity are adjusted in a timely manner until the requirements are met.

[0057] After vacuum arc remelting is completed and cooled to room temperature, the ingot undergoes final quality inspection, including visual inspection, composition analysis, mechanical property sampling inspection, and internal defect inspection. Visual inspection ensures the ingot surface is free of defects such as cracks, porosity, inclusions, and shrinkage cavities, with a surface roughness Ra ≤ 1.6 μm. Composition analysis ensures that the content of each element conforms to the optimized alloy composition scheme, with a deviation within ±0.05%. Mechanical property sampling inspection uses tensile testing, with a sampling ratio of 5%. The test results show that the ingot's specified plastic elongation strength ≥ 1600 MPa and tensile strength ≥ 1900 MPa, meeting the requirements for subsequent forging. Internal defect inspection uses ultrasonic testing to ensure the ingot is free of internal cracks, porosity, and other defects. After passing the inspection, the vacuum arc remelted ingot becomes a secondary hardened high-strength steel base material, which can be directly used for subsequent upsetting and drawing processes.

[0058] S203, the alloy steel ingot is preheated, homogenized and heated for a short time and then upsetting and drawing deformation is performed, and the initial forging temperature and the final forging temperature are controlled to generate alloy steel bars with uniform structure. Specifically, the alloy steel ingot can be heated by a process route of low-temperature preheating, near-high-temperature homogenization, and high-temperature short-time heating. First, the ingot is heated to 550 to 600 degrees Celsius for preheating, then heated to 950 to 1000 degrees Celsius for homogenization, and finally held at 1080 to 1100 degrees Celsius for a short time to generate a heated billet that is thoroughly heated and has not coarsened grains. The core of this step is to gradually eliminate thermal stress and microstructure inhomogeneity within the alloy steel ingot through a three-stage gradient heating process, ensuring overall heat penetration of the ingot. Simultaneously, strict control of heating temperature and time prevents grain coarsening, providing high-performance heated blanks for subsequent upsetting and drawing deformation. The specific implementation method is as follows: The core of the three-stage heating process route is to balance heat penetration and grain size control, avoiding problems such as excessive temperature difference between the inside and outside of the ingot, thermal stress concentration, or grain coarsening caused by a single heating method. Low-temperature preheating is used to eliminate residual stress inside the ingot, near-high temperature homogenization is used to achieve uniform temperature inside and outside the ingot, and high-temperature short-time holding is used to meet the forging temperature requirements and avoid grain growth. The three work together to ensure the quality of the heated billet.

[0059] The heating operation utilizes a continuous heating furnace with precise temperature control, achieving an accuracy of ±5℃. It monitors the furnace temperature in real time and automatically adjusts the heating power to ensure the temperature remains stable within the set range during heating. Before heating, the alloy steel ingot undergoes pretreatment to remove oxide scale and oil from its surface. Mechanical grinding is used to control the surface roughness of the ingot to Ra≤1.6μm after grinding, preventing oxidation defects caused by surface impurities during heating and ensuring the quality of subsequent forging.

[0060] In the low-temperature preheating stage, the pretreated ingot is sent into the heating furnace and slowly heated to 550 to 600 degrees Celsius at a rate controlled at 80 degrees Celsius / h. This heating rate avoids excessive temperature difference between the ingot surface and core, which could generate thermal stress and cause ingot cracking. The preheating temperature is set between 550 and 600 degrees Celsius. This temperature range effectively eliminates residual stress generated during ingot solidification and prevents excessive oxidation of the ingot surface due to high temperatures. In this example, a preheating temperature of 580 degrees Celsius is selected, and the preheating holding time is 60 minutes to ensure sufficient release of residual stress. The furnace temperature is monitored in real time during the holding period, with fluctuations not exceeding ±5 degrees Celsius.

[0061] After preheating, the furnace enters a near-high-temperature homogenization stage, gradually raising the furnace temperature to 950-1000 degrees Celsius at a rate of 100 degrees Celsius / h, which is faster than the preheating stage, balancing heating efficiency and temperature uniformity. The homogenization temperature is set between 950 and 1000 degrees Celsius. This temperature range allows for sufficient diffusion of the ingot's internal structure, eliminating component segregation and ensuring uniform temperature between the core and edges of the ingot, with the temperature difference controlled within 30 degrees Celsius. In this example, a homogenization temperature of 980 degrees Celsius is selected, with a holding time of 90 minutes. During the holding period, the furnace's circulating air system ensures uniform temperature distribution, guaranteeing thorough heating of the entire ingot without any unheated areas.

[0062] After homogenization, the furnace enters a high-temperature short-time holding stage, rapidly raising the furnace temperature to 1080-1100 degrees Celsius at a rate controlled at 120°C / h to quickly reach the required forging temperature. The key to this stage is "short-time holding," which prevents prolonged high temperatures from causing grain coarsening in the ingot. The holding time is controlled to 15-20 minutes. In this example, a holding temperature of 1090 degrees Celsius and a holding time of 18 minutes are selected. This ensures that the ingot temperature meets forging requirements while keeping the grain size below 50μm, preventing grain coarsening from affecting subsequent forging performance.

[0063] After the high-temperature short-time heat preservation is completed, the ingot is quickly removed from the heating furnace. At this time, the surface temperature of the ingot is about 1070 to 1090 degrees Celsius, the core temperature is about 1060 to 1080 degrees Celsius, the temperature uniformity is good, there is no obvious temperature difference, the ingot is fully heated, the grains have not coarsened, and there are no obvious oxidation defects on the surface. This is a qualified heated billet that can be directly used for subsequent upsetting and drawing forging processes.

[0064] The heated billet is upset and drawn forged. The drawing process is carried out by wide anvil and large reduction. The matching relationship between feed and reduction is determined by numerical simulation. The initial forging temperature is controlled at 1050 to 1080 degrees Celsius and the final forging temperature is not lower than 960 degrees Celsius to generate a preliminary shaped bar. The core of this step is to change the shape and dimensions of the heated billet through upsetting and drawing forging, gradually bringing the billet closer to the shape of a bar. At the same time, a wide anvil and increased pressing process refine the grains and improve the uniformity of the microstructure. Numerical simulation is used to optimize forging parameters and strictly control the initial and final forging temperatures to ensure that the microstructure and dimensions of the initially formed bar meet the requirements. The specific implementation method is as follows: Upsetting and drawing forging are the core processes in metal plastic deformation. Upsetting reduces the height of the billet, increases its cross-sectional area, eliminates porosity defects inside the ingot, and makes the structure denser. Drawing reduces the cross-sectional area of ​​the billet and increases its length to obtain the required bar shape. The combination of these two processes achieves the initial forming of the billet. Forging is carried out using a hydraulic press, which features adjustable pressure and stable operation, allowing for precise control of forging pressure and deformation, ensuring a stable and controllable forging process.

[0065] Upsetting is performed first. The heated billet (320mm in diameter and 1300mm in length) is placed on the lower anvil of the hydraulic press. The center of the billet is aligned with the center of the lower anvil, with a deviation not exceeding 0.5mm, to avoid uneven stress during forging that could cause deformation and displacement of the billet. During upsetting, the initial forging temperature is controlled between 1050 and 1080 degrees Celsius. In this example, an initial forging temperature of 1060 degrees Celsius is selected. The forging pressure is controlled at 8000kN, and the upsetting deformation is controlled at 25% to 30%. That is, after upsetting, the billet height decreases from 1300mm to 910 to 975mm, and the cross-sectional area increases from 80424.77mm² to 107233.03 to 114891.10mm². The billet temperature is monitored in real time during upsetting to ensure that the temperature does not fall below 1000 degrees Celsius, to avoid excessively low temperatures that could increase deformation resistance and cause cracks.

[0066] After upsetting, drawing forging is performed. Drawing employs a wide anvil and increased reduction process. The width of the wide anvil is set to 1.2 to 1.5 times the current diameter of the billet. In the example, the diameter corresponding to the cross-sectional area of ​​the billet after upsetting is approximately 370 mm, and the width of the wide anvil is selected as 444 mm (1.2 times the diameter). The function of the wide anvil is to increase the contact area between the billet and the anvil, allowing the deformation force to be evenly transmitted to the core of the billet, preventing a loose core structure, and refining the grains. Increasing the reduction means that the reduction in each drawing pass is controlled to be 30 to 50 mm, ensuring that the deformation penetrates deep into the core, further eliminating internal defects and improving the uniformity of the microstructure.

[0067] The matching relationship between feed rate and reduction rate was determined through numerical simulation using the finite element method. The core principle is to establish a three-dimensional model of the billet, simulate the deformation process under different combinations of feed rate and reduction rate, analyze the deformation uniformity, grain refinement effect, and stress distribution, and select the optimal parameter matching relationship. During the simulation, the feed rate was set to a range of 50 to 80 mm, and the reduction rate to a range of 30 to 50 mm. Through comparison of multiple simulations, the optimal matching relationship was found to be: feed rate 65 mm and reduction rate 40 mm. This matching relationship ensures uniform billet deformation during the drawing process, eliminates local stress concentration, achieves the best grain refinement effect, and avoids forging defects such as folds and cracks.

[0068] During the drawing process, the initial forging temperature and the final forging temperature must be strictly controlled. The initial forging temperature is consistent with the upsetting initial forging temperature, which is 1050 to 1080 degrees Celsius. The final forging temperature should not be lower than 960 degrees Celsius. If the final forging temperature is too low, the plasticity of the billet will decrease, the deformation resistance will increase, and cracks will easily occur. If the final forging temperature is too high, it will lead to grain coarsening and affect the performance of the bar. During the drawing process, the surface temperature of the billet is monitored in real time using an infrared thermometer. When the temperature drops to 980 degrees Celsius, the drawing speed is appropriately increased to ensure that the temperature of the billet is not lower than 960 degrees Celsius when the drawing is completed.

[0069] The drawing process is carried out in multiple passes. After each drawing pass, the length of the billet increases and the diameter decreases. In the example, after four drawing passes, the billet diameter decreased from 370mm to 180mm, and the length increased from 940mm to 3760mm. The external dimensions meet the requirements for preliminary forming of the bar. The surface of the bar is free of defects such as folds, cracks, and dents. The internal structure is dense, and the grain size is controlled below 40μm, which is the preliminary forming of the bar.

[0070] The pre-formed bar is subjected to multiple upsetting and drawing deformations, with the deformation amount in each pass controlled to be no less than 30%. The temperature difference between the core and the edge of the billet is monitored in real time. When the billet temperature drops below 960 degrees Celsius, it is reheated in the furnace to generate a bar with a refined microstructure. The core of this step is to further refine the internal grains of the bar stock through multiple upsetting and drawing deformations, improve the uniformity of the microstructure, and eliminate microstructural defects generated during the initial forming process. At the same time, the deformation amount and temperature are strictly controlled to ensure that each deformation is sufficient and to avoid forging defects caused by excessively low temperatures, resulting in a bar stock with a refined microstructure and excellent performance. The specific implementation method is as follows: The core function of multi-pass upsetting and drawing deformation is to break down the coarse grains in the initially formed bar through multiple plastic deformations, promoting grain refinement, making the internal structure more uniform, eliminating stress concentration and loose structure generated during upsetting and drawing, and improving the strength and toughness of the bar. Upsetting and drawing deformation refers to alternating upsetting and drawing operations, with each pass first performing upsetting and then drawing, causing the billet to undergo plastic deformation in different directions, further refining the grains.

[0071] The deformation amount in each pass is controlled to be no less than 30%. The deformation amount is calculated as follows: Deformation amount = (Cross-sectional area of ​​billet before deformation - Cross-sectional area of ​​billet after deformation) ÷ Cross-sectional area of ​​billet before deformation × 100%. This deformation amount requirement ensures that each pass of deformation is sufficient, effectively breaking down coarse grains and promoting grain refinement. If the deformation amount is less than 30%, the deformation is insufficient, the grain refinement effect is poor, and the purpose of microstructure optimization cannot be achieved. In the example, the diameter of the initially formed bar is 180mm, and the cross-sectional area is 25446.90mm². After the first pass of upsetting and drawing deformation, the diameter is reduced to 138mm, and the cross-sectional area is 14701.98mm². The deformation amount = (25446.90 - 14701.98) ÷ 25446.90 × 100% ≈ 42.2%, which meets the requirement of no less than 30%.

[0072] The number of passes in multi-pass upsetting is determined based on the final dimensions and microstructure requirements of the bar stock. In this example, three passes are used, with deformation amounts of 42.2%, 38.5%, and 35.1% for each pass, all meeting the requirement of not less than 30%. After each pass, the grain size of the billet gradually decreases. After the first pass, the grain size decreases from 40 μm to 30 μm; after the second pass, it decreases to 25 μm; and after the third pass, it decreases to below 20 μm, significantly improving the uniformity of the microstructure.

[0073] During the deformation process, the temperature difference between the core and edge of the billet is monitored in real time. A dual-point infrared thermometer is used to monitor the temperature of both the core and edge of the billet separately. The temperature difference is controlled within 25℃. If the temperature difference is too large, it will lead to uneven deformation of the billet, stress concentration, and even cracks. The monitoring accuracy is ±3℃, and temperature data is recorded every 10 seconds to monitor temperature changes in real time.

[0074] Strictly control the billet temperature. The initial forging temperature for each deformation pass should be controlled between 1030 and 1050 degrees Celsius, and the final forging temperature should not be lower than 960 degrees Celsius. When the billet temperature drops below 960 degrees Celsius, immediately stop the deformation and return the billet to the heating furnace for reheating. The reheating temperature should be set between 1050 and 1060 degrees Celsius, and the holding time should be 20 to 30 minutes to ensure that the billet temperature rises back to the forging requirements before continuing the next deformation pass. In the example, after the first deformation pass, the billet temperature drops to 950 degrees Celsius, below 960 degrees Celsius. It is then returned to the heating furnace, heated to 1055 degrees Celsius, held for 25 minutes, and the temperature rises again before proceeding to the second deformation pass. This ensures that the deformation process proceeds smoothly without cracking.

[0075] After each deformation pass, the billet undergoes a simple surface cleaning to remove the oxide scale generated during deformation. High-pressure air is used to blow it away to prevent the oxide scale from being pressed into the billet during subsequent deformation processes, thus preventing inclusion defects. After three passes of upsetting and drawing deformation, the billet diameter is reduced to 100mm and the length is increased to 8200mm. The internal grain size is uniform, controlled below 20μm, and the microstructure is dense, without defects such as porosity or cracks. This is the microstructure refined bar stock, which can proceed to subsequent finishing and surface grinding processes.

[0076] The fine-grained bars are finished and surface-ground to remove the oxide scale and surface defects generated during forging, ultimately producing alloy steel bars with uniform microstructure.

[0077] The core of this step is to correct the external dimensions of the bar stock through finishing and to remove surface defects through surface grinding, ensuring the dimensional accuracy, surface quality, and uniformity of the alloy steel bar stock to meet the requirements of subsequent die forging or extrusion forming. The specific implementation method is as follows: The core function of finishing is to correct shape defects such as bending and ellipticing in the bar stock, ensuring that the straightness and roundness of the bar stock meet the requirements, and providing dimensionally accurate blanks for subsequent forming processes. The finishing operation is carried out using a press equipped with a dedicated finishing die. The die size matches the target size of the bar stock. In the example, the target diameter of the bar stock is 100mm, the roundness tolerance is ±0.2mm, and the straightness tolerance is 0.3mm / m.

[0078] Before finishing, the dimensions of the refined bar stock are inspected using calipers and a straightness measuring instrument to check the diameter, roundness, and straightness. The inspection data is recorded, and a targeted finishing plan is developed for any defects such as bending or ellipticity. During finishing, the bar stock is placed in the finishing mold, and the pressure of the press is adjusted, controlled between 5000 and 6000 kN. The pressure is adjusted according to the severity of the defect to avoid excessive deformation due to excessive pressure, or ineffective straightening due to insufficient pressure. In the example, a bar stock had a bending defect of 0.5 mm / m. The pressure was adjusted to 5500 kN, and a single finishing operation was performed. After straightening, the straightness reached 0.25 mm / m, meeting the tolerance requirements.

[0079] After finishing, surface grinding is performed. The core purpose of surface grinding is to remove surface defects such as oxide scale, scratches, dents, and inclusions generated during forging, while reducing surface roughness to ensure a smooth and defect-free bar surface. This prevents surface defects from expanding during subsequent forming processes and affecting the quality of the key component blank. Surface grinding is performed using a grinding wheel with a grit size of 80 to 100 mesh. The grinding speed is controlled at 15 m / min. Coolant is used during the grinding process to prevent high temperatures from generating oxidation or thermal stress on the bar surface.

[0080] The grinding operation is carried out in two steps. The first step is rough grinding, which mainly removes surface oxide scale and obvious surface defects. After rough grinding, the surface roughness is controlled to Ra≤3.2μm. The second step is fine grinding, which mainly refines the surface quality and removes scratches generated during rough grinding. After fine grinding, the surface roughness is controlled to Ra≤1.6μm, meeting the surface requirements of subsequent forming processes. During the grinding process, the operator observes the surface condition of the bar in real time to ensure that all surface defects are removed without omission.

[0081] After grinding, the bars undergo comprehensive quality inspection, including dimensional accuracy, surface quality, and microstructure uniformity. Dimensional accuracy is checked using calipers and a straightness measuring instrument to ensure diameter tolerance is within ±0.2mm, roundness tolerance is within ±0.2mm, and straightness tolerance is within 0.3mm / m. Surface quality is checked visually and with a magnifying glass to ensure the surface is free of defects such as oxide scale, scratches, dents, and inclusions. Microstructure uniformity is checked using a metallographic microscope, with three randomly selected inspection points to observe grain size and distribution, ensuring uniform grain size controlled below 20μm, with no obvious segregation or porosity.

[0082] After passing the inspection, the bar stock undergoes surface rust prevention treatment by applying rust-preventive oil with a thickness controlled between 0.01 and 0.02 mm to prevent oxidation and rusting. It is then sorted and stored, resulting in a uniform alloy steel bar stock. This bar stock can be directly used for subsequent die forging or extrusion forming to prepare blanks for critical components.

[0083] S204, the alloy steel bar is prepared into a critical component blank by die forging or extrusion forming process, and then subjected to a heat treatment system of quenching and cyclic deep cold tempering for toughening treatment. After precision machining, a high-strength and tough alloy steel critical component resistant to high overload is obtained that meets the specified plastic elongation strength, tensile strength, elongation after fracture and impact absorption energy index.

[0084] Specifically, a forming process scheme can be designed according to the structural shape of the critical component. A die forging or extrusion forming process can be adopted. The number of forming passes, the deformation amount per pass, and the heating temperature can be determined through numerical simulation optimization. The alloy steel bar is heated and placed into a mold for die forging or extrusion forming to generate a critical component blank. The core of this step is to select a suitable forming process based on the structural characteristics of the critical components, and optimize the process parameters through numerical simulation to ensure that the formed blank has accurate dimensions, uniform microstructure, and no forming defects. This lays the foundation for subsequent toughening treatment and precision machining. The specific implementation method is as follows: The structural shape of critical components is the core basis for the design of forming process schemes. Different critical components with different structures need to be matched with different forming processes. In the example, a critical component with high overload resistance is selected. Its structure is a stepped shaft. One end is a flange (diameter 180mm, thickness 30mm), the other end is a slender shaft (diameter 50mm, length 600mm), and the middle is a transition section (diameter 80mm, length 120mm). The overall structure has the characteristics of large size difference and local stress concentration. It is necessary to take into account both forming accuracy and microstructure density.

[0085] The design of forming process schemes needs to clearly define the process type, mold structure, heating parameters and forming steps. Based on the structural characteristics of the part, the die forging forming process should be selected. The core advantages of die forging are high forming accuracy and dense structure, which can effectively control the external dimensions and internal quality of the part. It is suitable for the preparation of blanks for critical parts with complex structures and high dimensional accuracy requirements. If the critical part is a simple columnar or tubular structure, the extrusion forming process can be selected. Extrusion forming can make the metal structure evenly distributed along the forming direction, further improving the toughness of the material.

[0086] Numerical simulation is the core method for optimizing forming process parameters. Employing the finite element method (FEM), the core principle is to establish a three-dimensional model of the alloy steel bar and the mold, simulating the plastic deformation, stress distribution, and temperature changes of the metal during forming. By comparing multiple sets of simulated parameters, the optimal forming passes, pass deformation amounts, and heating temperatures are selected, avoiding mold damage and blank defects caused by blind trial molding. During the simulation, the forming passes were set to a range of 3-5, the pass deformation amount to a range of 20%-40%, and the heating temperature to a range of 1000-1050℃. The optimization goal was to achieve a blank without folds, cracks, or shrinkage cavities, with dimensional deviations within ±0.5mm.

[0087] Through numerical simulation optimization, the final forming process parameters were determined: Four forming passes are required. The first pass involves a 35% deformation, upsetting a 100mm diameter alloy steel bar to 130mm to accommodate the flange portion. The second pass involves a 30% deformation, performing preliminary elongation and transition section forming, reducing the diameter from 130mm to 80mm. The third pass involves a 25% deformation, completing the preliminary forming of the slender shaft portion, reducing the diameter from 80mm to 60mm. The fourth pass involves a 20% deformation, finishing the shape to ensure that the dimensions of each part meet the design requirements. The heating temperature is set at 1020℃, which ensures good plasticity of the alloy steel bar, reduces deformation resistance, and avoids grain coarsening caused by excessively high temperatures.

[0088] Before forming, the alloy steel bar (100mm in diameter, 8200mm in length) is cut into segments of 950mm in length according to the blank size, ensuring that the cut surfaces are flat and free of burrs, skewing, or other defects. The cut bars are then placed in a heating furnace and heated to 1020℃ for 40 minutes to ensure thorough heating, uniform temperature, and that the temperature difference between the core and edges is controlled within 20℃. After heating, the bars are quickly placed into a pre-set forging die, and pressure is applied using a hydraulic press at 9000kN. Forging is then performed step-by-step according to the optimized four-pass forming parameters. After each pass, the blank is simply cleaned to remove surface oxide scale before proceeding to the next pass.

[0089] After forming, the blank is removed from the mold and allowed to cool naturally to room temperature. The blank is then subjected to dimensional and visual inspections to ensure that the deviation between the blank's external dimensions and the design drawings is within ±0.5mm, and that there are no forming defects such as folds, cracks, dents, or slag inclusions on the surface, and that the internal structure is dense. This indicates that the blank is a qualified key component blank and can proceed to the subsequent quenching process.

[0090] The blank of the critical component is quenched by heating it to the austenitizing temperature, holding it at that temperature, and then rapidly cooling it to transform the austenite into martensite, thus generating the quenched critical component. The core of this step is to transform the austenitic structure of the critical component blank into a martensitic structure through quenching, significantly improving the material's hardness and strength. This lays the foundation for subsequent toughening treatment through cyclic cryogenic tempering. Simultaneously, heating and cooling parameters are strictly controlled to avoid quenching cracks and deformation. The specific implementation method is as follows: The core principle of quenching is to heat the blank of the critical component to the austenitizing temperature, allowing carbon to fully dissolve into the austenite, followed by rapid cooling to inhibit carbon precipitation and transform the austenite into martensite, thereby increasing the material's hardness and strength. The austenitizing temperature is a key parameter in quenching; too low a temperature will result in insufficient austenitization and incomplete martensite transformation, failing to achieve the desired strengthening effect; too high a temperature will lead to grain coarsening, reduced material toughness, and even oxidation and decarburization defects.

[0091] Based on the compositional characteristics of alloy steel, the austenitizing temperature range was determined to be 880-920℃. In this example, 890℃ was selected, as this temperature ensures sufficient austenitization while avoiding grain coarsening. The holding time was determined based on the maximum thickness of the blank for the critical component, calculated as: Holding time = Maximum blank thickness × 1.5 min / mm. In this example, the maximum blank thickness is 30 mm (flange area), therefore the holding time = 30 mm × 1.5 min / mm = 45 minutes. During the holding process, the furnace temperature was monitored in real time, with temperature fluctuations controlled within ±5℃ to ensure uniform austenitization.

[0092] The heating operation utilizes a box-type resistance furnace, which features uniform heating to prevent localized overheating or underheating. Before heating, the surface of the critical component blank is cleaned to remove oxide scale and oil stains using high-pressure air blowing to prevent oxidation defects and decarburization during heating. The cleaned blank is then placed in the heating furnace, and the temperature is slowly increased at a rate controlled at 100℃ / h to avoid excessively rapid heating that could lead to internal thermal stress concentration and cracking.

[0093] When the furnace temperature reaches 890℃, start timing and hold for 45 minutes. After holding, quickly remove the billet from the furnace and place it in a cooling medium for rapid cooling. The cooling rate must be controlled at over 200℃ / min to ensure rapid transformation of austenite into martensite. A brine solution with a concentration of 10% (mass fraction) is used as the cooling medium. This concentration of brine provides a fast cooling rate, meeting the cooling requirements for martensitic transformation while preventing the billet from cracking due to excessively rapid cooling.

[0094] During the cooling process, the cooling temperature of the blank is monitored in real time. When the blank temperature drops below 200℃, it is removed from the brine and allowed to cool naturally to room temperature to avoid surface corrosion caused by prolonged immersion at low temperatures. After quenching, a quenched critical component is generated, with a hardness of HRC60-62, significantly higher than the hardness before quenching (HRC28-30). However, the material has poor toughness and residual stress at this point, requiring subsequent deep cryogenic tempering treatment to improve toughness and eliminate residual stress.

[0095] After quenching, the key parts are visually inspected to ensure that there are no defects such as quenching cracks, deformation, oxidation, or decarburization on the surface. If there are minor cracks, they need to be ground and repaired. If the cracks are severe, they are deemed unqualified and must be re-formed and quenched.

[0096] The key components in the quenched state are subjected to cyclic cryogenic tempering. First, cryogenic treatment is performed to transform the residual austenite into martensite. Then, the temperature is restored to room temperature, and a second cryogenic treatment is performed. This process is repeated multiple times to control the type, size, and distribution of precipitated phases. Finally, tempering treatment is performed to generate strong and tough key components. The core of this step is to eliminate residual stress in the quenched critical components through cyclic deep cryogenic tempering, fully transforming the residual austenite into martensite, and simultaneously controlling the type, size, and distribution of precipitated phases to achieve a balance between hardness and toughness, thereby improving the strength and toughness of the critical components. The specific implementation method is as follows: The core function of cyclic cryogenic tempering is to solve the problems of poor toughness and high residual stress in quenched materials. Its principle is to gradually transform the residual austenite in the quenched critical parts into martensite through multiple cryogenic-warming cycles, while promoting the uniform precipitation of fine precipitates (such as carbides and nitrides), refining the grains, eliminating residual stress, thereby improving the toughness and strength of the material and achieving toughness enhancement.

[0097] The number of deep cryogenic cycles is determined based on the retained austenite content, generally 3-4 times. In this example, 3 cycles are selected to ensure sufficient transformation of the retained austenite while avoiding excessive cycles that could lead to fatigue cracks. The cryogenic treatment temperature is set between -80 and -100℃. This temperature range effectively promotes the transformation of retained austenite into martensite without causing material embrittlement. In this example, a cryogenic temperature of -90℃ is selected.

[0098] First cryogenic treatment: The quenched critical component is placed in a cryogenic chamber and slowly cooled at a rate controlled at 10℃ / min to avoid rapid cooling that could lead to thermal stress concentration and cracking. When the chamber temperature drops to -90℃, it is held for 2 hours, ensuring uniform temperature across all parts of the critical component during this process, with a temperature deviation controlled within ±3℃, to allow the retained austenite to fully transform into martensite. After the holding period, the critical component is removed from the cryogenic chamber and allowed to naturally warm to room temperature. No additional heating is required during this warming process to avoid stress caused by a sudden temperature rise.

[0099] Second cryogenic treatment: After the critical components have fully warmed to room temperature (25℃), they are placed back into the cryogenic chamber, and the first cryogenic operation is repeated. The cooling rate is 10℃ / min, the cryogenic temperature is -90℃, and the holding time is 2 hours to further promote the transformation of residual austenite and refine the precipitated phase. After the holding time is completed, the components are allowed to naturally warm to room temperature.

[0100] The third cryogenic treatment: The operation was the same as the previous two, with a cooling rate of 10℃ / min, a cryogenic temperature of -90℃, and a holding time of 2 hours, ensuring that the residual austenite transformation rate reached over 98%, the precipitated phase size was controlled below 50nm, and the distribution was uniform. After three cryogenic-reheat cycles, the residual austenite in the critical component was basically transformed into martensite, the residual stress was significantly reduced, and the toughness was initially improved.

[0101] After cryogenic cycling, tempering is performed. The core function of tempering is to eliminate residual stress generated during cryogenics, further regulate the distribution of precipitated phases, improve the toughness of the material, and maintain a certain level of hardness, achieving a balance between strength and toughness. The tempering temperature is set at 200-220℃; 210℃ is selected in this example. This temperature avoids martensite decomposition while promoting the precipitation of fine carbides, thus improving toughness.

[0102] The tempering process utilizes a box-type resistance furnace. The critical component is placed in the furnace and slowly heated to 210℃ at a rate controlled at 80℃ / h. The holding time is 90 minutes, with temperature fluctuations controlled within ±5℃ during the holding period. After holding, the component is cooled in the furnace to below 100℃, then removed and allowed to cool naturally to room temperature to avoid stress caused by rapid cooling. After tempering, a strong and toughened critical component is produced, with a hardness controlled at HRC52-54, significantly improved toughness, and an impact absorption energy reaching 65-70 Joules, close to the final performance requirements. The residual stress relief rate exceeds 90%.

[0103] Precision machining is performed on the toughened key components. The machining allowance is removed through turning, milling and grinding processes to achieve the final dimensional accuracy and surface quality requirements of the key components and produce finished key components. The core of this step is to remove the machining allowance of the toughened critical components through precision cutting, accurately control the dimensional accuracy and surface quality of the parts, and ensure that the critical components meet the design requirements and can meet the needs of high overload resistance. The specific implementation method is as follows: The core requirements of precision machining are high accuracy and high surface quality. The machining process follows the sequence of "turning → milling → grinding" to gradually remove machining allowances. After each process, dimensional inspection is performed to ensure that machining accuracy is gradually improved and to avoid dimensional deviations that cannot be compensated for in subsequent machining. Before machining, the surface of the toughened key parts is cleaned to remove surface oxide scale and rust. Alcohol is used to wipe the surface to ensure cleanliness and prevent impurities from affecting machining accuracy and surface quality during the machining process.

[0104] Turning is mainly used to machine the outer diameter, end face, and stepped surface of critical components, removing most of the machining allowance and ensuring preliminary dimensional accuracy. During turning, appropriate cutting tools are selected, with the cutting speed controlled at 80-100 m / min, the feed rate at 0.1-0.15 mm / r, and the depth of cut at 0.2-0.3 mm. This combination of parameters ensures cutting efficiency and machining accuracy, avoiding built-up edge and surface scratches. In the example, the machining allowance for the flange end face is 2 mm, which is removed by turning, and the flatness of the machined end face is controlled within 0.01 mm. The machining allowance for the outer diameter of the slender shaft is 3 mm, completed in two turns: the first with a depth of cut of 0.3 mm and the second with a depth of cut of 0.2 mm. After machining, the dimensional deviation of the outer diameter is controlled within ±0.02 mm.

[0105] After turning, milling is performed, mainly for machining the bolt holes and keyways of critical components such as flanges, ensuring the dimensional and positional accuracy of these parts. During milling, the cutting speed is controlled at 60-80 m / min, the feed rate at 0.08-0.12 mm / r, and the depth of cut at 0.15-0.25 mm. A dividing head is used for positioning to ensure that the positional deviation of the bolt holes is controlled within 0.02 mm, and the width and depth deviations of the keyways are controlled within ±0.01 mm. In the example, six bolt holes with a diameter of 12 mm are evenly distributed on the flange, which are milled, with the hole spacing deviation controlled within 0.015 mm, meeting assembly requirements.

[0106] After milling, grinding is performed. This is the final step in precision cutting, primarily used to refine surface quality, correct dimensional deviations, and ensure the final dimensional accuracy and surface roughness of critical components. Grinding is applied to key areas of critical components, including the outer diameter of slender shafts, the end face of flanges, and the inner walls of bolt holes. The grinding speed is controlled at 15-20 m / s, and the feed rate is controlled at 0.005-0.01 mm / r. Coolant is used to prevent surface burns and thermal stress caused by high temperatures during grinding.

[0107] After grinding, the final dimensional accuracy requirements for the critical components are: dimensional deviation within ±0.01mm, flatness within 0.008mm, cylindricity within 0.005mm, and surface roughness Ra≤0.8μm. A comprehensive dimensional inspection is performed on the machined critical components using calipers, micrometers, projectors, and other inspection tools to check the dimensions and surface quality of each part, ensuring compliance with design requirements. After passing inspection, the critical components undergo surface rust prevention treatment by applying rust-preventive oil with a thickness controlled between 0.01-0.02mm to prevent surface oxidation and rusting; this results in the finished critical components.

[0108] Mechanical property testing is conducted on finished critical components. Tensile and impact tests are used to test the specified plastic extension strength, tensile strength, elongation after fracture, and impact absorption energy to verify whether they meet the corresponding index requirements of not less than 1750 MPa, not less than 2000 MPa, not less than 20%, and not less than 75 joules, thus generating high-strength and high-toughness alloy steel critical components resistant to high overloads that have passed the tests.

[0109] The core of this step is to verify whether the mechanical properties of the finished critical components meet the requirements for high overload resistance through mechanical performance testing, screen out qualified products, and ensure that the critical components have sufficient strength and toughness during use. The specific implementation method is as follows: The core items for mechanical property testing include specified plastic extension strength, tensile strength, elongation after fracture, and impact absorption energy. These four indicators directly determine the high overload resistance of critical components. The testing standards strictly follow relevant technical requirements, and the entire testing process is conducted in a professional testing environment to ensure accurate and reliable test results. Before testing, three test samples are randomly selected from the finished critical components. The preparation of the samples must meet the testing standards. The tensile test samples are circular cross-section samples with a diameter of 10 mm, a length of 100 mm, and a gauge length of 50 mm. The impact test samples are Charpy U-notch samples with dimensions of 10 mm × 10 mm × 55 mm and a notch depth of 2 mm. Processing defects are avoided during sample preparation to ensure that the sample performance is consistent with that of the finished critical components.

[0110] Tensile testing is used to measure specified plastic extension strength, tensile strength, and elongation after fracture. It is performed using an electronic universal testing machine with an accuracy of ±1%. The machine is calibrated before the test to ensure accurate data. During the test, the tensile specimen is clamped in the upper and lower jaws of the testing machine. The jaw positions are adjusted to ensure the specimen axis is aligned with the direction of force applied by the machine, avoiding eccentric force. The tensile speed is set to 2 mm / min, and the tensile force is applied slowly, recording the tensile force and specimen deformation in real time until the specimen breaks.

[0111] After the test, various indicators were calculated based on the recorded data: The specified plastic extension strength refers to the stress at which the specimen undergoes 0.2% plastic extension, calculated by reading the corresponding stress value from the stress-strain curve; tensile strength refers to the maximum stress the specimen can withstand before fracture, i.e., the ratio of the maximum tensile force to the specimen's cross-sectional area; elongation after fracture refers to the ratio of the elongation of the gauge length after fracture to the original gauge length, calculated as: elongation after fracture = (gauge length after fracture - original gauge length) ÷ original gauge length × 100%. In the example, the test results for the three tensile specimens were as follows: Specified plastic extension strengths of 1780 MPa, 1795 MPa, and 1770 MPa, all not less than 1750 MPa; tensile strengths of 2030 MPa, 2050 MPa, and 2020 MPa, all not less than 2000 MPa; and elongation after fracture of 21.5%, 22.3%, and 21.1%, all not less than 20%, meeting the indicator requirements.

[0112] Impact testing is used to measure impact absorption energy. A pendulum impact testing machine is used, with an energy range of 0-300J and an accuracy of ±1J. The machine is calibrated before testing to ensure accurate impact energy. During testing, the impact specimen is placed on the machine's support, and its position is adjusted to ensure the notch faces the impact direction, preventing specimen loosening. A 150J pendulum is selected, and the pendulum is released to impact the specimen. The impact energy absorbed when the specimen breaks is recorded; this is the impact absorption energy. In the example, the test results for the three impact specimens are 78J, 82J, and 76J, all not less than 75J, meeting the requirements.

[0113] The test data were analyzed and found that all mechanical properties of the three samples met the specified requirements, and the data fluctuations were small, indicating that the mechanical properties of the finished key components were stable. If any indicator of a sample fails to meet the requirements, the sample size must be doubled for retesting. If the retest still fails, the batch of key components is deemed unqualified and must undergo toughening treatment and precision machining again until it passes the test.

[0114] After passing the inspection, the finished critical components undergo a final visual inspection and dimensional verification to ensure there are no surface defects or dimensional deviations. They are then packaged and stored, becoming high-strength and tough alloy steel critical components resistant to high overloads, which are ready for practical use.

[0115] Another embodiment of the present invention provides a low-cost intelligent manufacturing system for high-strength and high-toughness alloy steel for critical components resistant to high overload, see [link to relevant documentation]. Figure 3 The system may include: The solver module 301 is used to construct a multiple regression equation for mechanical properties and chemical composition based on the range of alloy element content and performance index requirements through regression analysis. Combined with the dynamic cost model of alloy elements, the global optimal algorithm is used to solve the lowest cost composition combination under performance constraints, and generate an optimized alloy composition scheme. Preparation module 302 is used to prepare high-purity alloy steel ingots with little or no segregation by employing a dual vacuum melting process of vacuum induction melting and vacuum consumable remelting, according to the optimized alloy composition scheme. Control module 303 is used to upset and draw the alloy steel ingot after preheating, homogenizing and short-time heating, control the initial forging temperature and the final forging temperature, and generate alloy steel bars with uniform structure. Module 304 is used to prepare the alloy steel bar into a critical component blank by die forging or extrusion forming process, and to perform a toughening treatment by quenching and cyclic deep cold tempering. After precision machining, a high-strength and tough alloy steel critical component resistant to high overload is obtained, which meets the specified plastic extension strength, tensile strength, elongation after fracture and impact absorption energy index.

[0116] This invention also provides a storage medium storing a computer program, wherein the computer program is configured to execute the steps in any of the above method embodiments when running.

[0117] This invention also provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0118] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A low-cost method for preparing high-strength and high-toughness alloy steel for critical components resistant to high overload, characterized in that, The method includes: Based on the range of alloy element content and performance requirements, a multiple regression equation for mechanical properties and chemical composition is constructed by regression analysis. Combined with the dynamic cost model of alloy elements, the lowest cost composition combination is solved under performance constraints using a global optimal algorithm to generate an optimized alloy composition scheme. A dual vacuum melting process, combining vacuum induction melting and vacuum consumable remelting, was employed to prepare high-purity alloy steel ingots with minimal segregation according to the optimized alloy composition scheme. The alloy steel ingot is preheated, homogenized and heated before being upset and drawn. The initial forging temperature and the final forging temperature are controlled to produce alloy steel bars with uniform structure. The alloy steel bar is prepared into a critical component blank by die forging or extrusion forming process. After being subjected to a heat treatment system of quenching and cyclic deep cold tempering for strengthening and toughening, and then precision machining, a high-strength and high-toughness alloy steel critical component resistant to high overload is obtained, which meets the specified plastic elongation strength, tensile strength, elongation after fracture and impact absorption energy index.

2. The method according to claim 1, characterized in that, Based on the alloy element content range and performance requirements, a multiple regression equation for mechanical properties and chemical composition is constructed using regression analysis. Combined with a dynamic cost model for alloy elements, a global optimal algorithm is used to solve for the lowest-cost composition combination under performance constraints, generating an optimized alloy composition scheme, including: Determine the range of alloy element content and performance index requirements, take each chemical element as input factor, and take the four mechanical properties of plastic extension strength, tensile strength, elongation after fracture and impact absorption energy as output response to generate factor and response datasets. Based on the factor and response dataset, the regression equations of four mechanical properties and chemical composition were fitted by the multivariate regression analysis method to obtain the regression equations of specified plastic extension strength, tensile strength, elongation after fracture and impact absorption energy, and to generate a set of mechanical property prediction models. Based on the correspondence between the unit price of alloy materials and the percentage parameters of element content, a dynamic cost equation for alloy elements is constructed. The percentage parameters of each element are substituted into the material alloy cost formula and summed to generate a dynamic cost objective function. Using the set of mechanical property prediction models as performance constraints and the dynamic cost objective function as the optimization objective, the Globalsearch global optimal algorithm is used to perform global optimization within the upper and lower limits of the composition variables, and outputs the alloy composition optimization scheme that meets the performance requirements and has the lowest cost.

3. The method according to claim 2, characterized in that, The aforementioned dual-vacuum melting process, employing both vacuum induction melting and vacuum arc remelting, prepares high-purity, low-segregation alloy steel ingots according to the optimized alloy composition scheme, comprising: The proportions of each alloy material are calculated based on the optimized alloy composition scheme, including ferrochrome alloy, cobalt plate, ferromolybdenum alloy, ferrovanadium alloy, metallic manganese, ferroniobium alloy, ferroboron alloy, electrolytic nickel plate, and carbon raiser, and a material proportion list is generated. The furnace charge weighed according to the material ratio list is loaded into the vacuum induction melting furnace and induction melting is carried out under vacuum conditions. The alloy elements are evenly distributed by electromagnetic stirring, and harmful impurities and gases are removed by slag making and vacuum degassing processes to generate vacuum induction melting ingots. Vacuum induction melting ingots are used as consumable electrodes and loaded into a vacuum consumable remelting furnace. Under vacuum conditions, the electrodes are gradually melted by electric arc heating and dripped into a water-cooled crystallizer for rapid solidification, which further reduces the content of oxygen, nitrogen, and hydrogen gases as well as harmful impurities such as sulfur and phosphorus, thus generating vacuum consumable remelting ingots. By implementing fine-grain solidification process control on vacuum consumable remelting ingots and adjusting the droplet rate and the cooling intensity of the crystallizer to reduce the temperature gradient between the edge and the core, high-purity alloy steel ingots with little segregation and uniform fine grains are obtained, which are secondary hardened high-strength steel base materials.

4. The method according to claim 3, characterized in that, The process of preheating, homogenizing, and briefly heating the alloy steel ingot before upsetting and drawing, controlling the initial and final forging temperatures to produce alloy steel bars with uniform microstructure, includes: The alloy steel ingot is heated by a process route of low temperature preheating, near high temperature homogenization and high temperature short time heating. First, the ingot is heated to 550 to 600 degrees Celsius for preheating, then heated to 950 to 1000 degrees Celsius for homogenization, and finally held at 1080 to 1100 degrees Celsius to generate a heated billet that is thoroughly heated and has not coarsened grains. The heated billet is upset and drawn forged. The drawing process is carried out by wide anvil and large reduction. The matching relationship between feed and reduction is determined by numerical simulation. The initial forging temperature is controlled at 1050 to 1080 degrees Celsius and the final forging temperature is not lower than 960 degrees Celsius to generate a preliminary shaped bar. The pre-formed bar is subjected to multiple upsetting and drawing deformations, with the deformation amount in each pass controlled to be no less than 30%. The temperature difference between the core and the edge of the billet is monitored in real time. When the billet temperature drops below 960 degrees Celsius, it is reheated in the furnace to generate a bar with a refined microstructure. The fine-grained bars are finished and surface-ground to remove the oxide scale and surface defects generated during forging, ultimately producing alloy steel bars with uniform microstructure.

5. The method according to claim 4, characterized in that, The alloy steel bar is prepared into a critical component blank using die forging or extrusion forming processes. After undergoing a heat treatment process of quenching and cyclic deep cryogenic tempering for strengthening and toughening, and precision machining, a high-strength and high-toughness alloy steel critical component resistant to high overload is obtained, meeting specified plastic elongation strength, tensile strength, elongation after fracture, and impact absorption energy indicators. This includes: Based on the structural shape of the critical component, a forming process scheme is designed. Die forging or extrusion forming process is adopted. The number of forming passes, deformation amount per pass and heating temperature are determined by numerical simulation optimization. After the alloy steel bar is heated, it is placed into the mold for die forging or extrusion forming to generate the critical component blank. The blank of the critical component is quenched by heating it to the austenitizing temperature, holding it at that temperature, and then rapidly cooling it to transform the austenite into martensite, thus generating the quenched critical component. The key components in the quenched state are subjected to cyclic cryogenic tempering. First, cryogenic treatment is performed to transform the residual austenite into martensite. Then, the temperature is restored to room temperature, and a second cryogenic treatment is performed. This process is repeated multiple times to control the type, size, and distribution of precipitated phases. Finally, tempering treatment is performed to generate strong and tough key components. Precision machining is performed on the toughened key components. The machining allowance is removed through turning, milling and grinding processes to achieve the final dimensional accuracy and surface quality requirements of the key components and produce finished key components. Mechanical property testing is conducted on finished critical components. Tensile and impact tests are used to test the specified plastic extension strength, tensile strength, elongation after fracture, and impact absorption energy to verify whether they meet the corresponding index requirements of not less than 1750 MPa, not less than 2000 MPa, not less than 20%, and not less than 75 joules, thus generating high-strength and high-toughness alloy steel critical components resistant to high overloads that have passed the tests.

6. A low-cost intelligent manufacturing system for high-strength and high-toughness alloy steel for critical components resistant to high overload, characterized in that, The system includes: The solution module is used to construct a multiple regression equation for mechanical properties and chemical composition based on the range of alloy element content and performance requirements through regression analysis. Combined with the dynamic cost model of alloy elements, the global optimal algorithm is used to solve the lowest cost composition combination under performance constraints, and generate an optimized alloy composition scheme. The preparation module is used to prepare high-purity alloy steel ingots with little or no segregation using a dual vacuum melting process of vacuum induction melting and vacuum consumable remelting, according to the optimized alloy composition scheme. The control module is used to upset and draw the alloy steel ingot after preheating, homogenizing and short-time heating, control the initial forging temperature and the final forging temperature, and generate alloy steel bars with uniform structure. The module is used to prepare the alloy steel bar into a critical component blank by die forging or extrusion forming process, and to perform a toughening treatment by quenching and cyclic deep cold tempering. After precision machining, a high-strength and tough alloy steel critical component resistant to high overload is obtained, which meets the specified plastic elongation strength, tensile strength, elongation after fracture and impact absorption energy index.

7. The system according to claim 6, characterized in that, The solution module is specifically used for: Determine the range of alloy element content and performance index requirements, take each chemical element as input factor, and take the four mechanical properties of plastic extension strength, tensile strength, elongation after fracture and impact absorption energy as output response to generate factor and response datasets. Based on the factor and response dataset, the regression equations of four mechanical properties and chemical composition were fitted by the multivariate regression analysis method to obtain the regression equations of specified plastic extension strength, tensile strength, elongation after fracture and impact absorption energy, and to generate a set of mechanical property prediction models. Based on the correspondence between the unit price of alloy materials and the percentage parameters of element content, a dynamic cost equation for alloy elements is constructed. The percentage parameters of each element are substituted into the material alloy cost formula and summed to generate a dynamic cost objective function. Using the set of mechanical property prediction models as performance constraints and the dynamic cost objective function as the optimization objective, the Globalsearch global optimal algorithm is used to perform global optimization within the upper and lower limits of the composition variables, and outputs the alloy composition optimization scheme that meets the performance requirements and has the lowest cost.

8. The system according to claim 7, characterized in that, The preparation module is specifically used for: The proportions of each alloy material are calculated based on the optimized alloy composition scheme, including ferrochrome alloy, cobalt plate, ferromolybdenum alloy, ferrovanadium alloy, metallic manganese, ferroniobium alloy, ferroboron alloy, electrolytic nickel plate, and carbon raiser, and a material proportion list is generated. The furnace charge weighed according to the material ratio list is loaded into the vacuum induction melting furnace and induction melting is carried out under vacuum conditions. The alloy elements are evenly distributed by electromagnetic stirring, and harmful impurities and gases are removed by slag making and vacuum degassing processes to generate vacuum induction melting ingots. Vacuum induction melting ingots are used as consumable electrodes and loaded into a vacuum consumable remelting furnace. Under vacuum conditions, the electrodes are gradually melted by electric arc heating and dripped into a water-cooled crystallizer for rapid solidification, which further reduces the content of oxygen, nitrogen, and hydrogen gases as well as harmful impurities such as sulfur and phosphorus, thus generating vacuum consumable remelting ingots. By implementing fine-grain solidification process control on vacuum consumable remelting ingots and adjusting the droplet rate and the cooling intensity of the crystallizer to reduce the temperature gradient between the edge and the core, high-purity alloy steel ingots with little segregation and uniform fine grains are obtained, which are secondary hardened high-strength steel base materials.

9. A storage medium, characterized in that, The storage medium stores a computer program, wherein the computer program is configured to execute the method of any one of claims 1-5 when it is run.

10. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to perform the method of any one of claims 1-5.

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