CN-122020888-A - Piston steel closed-loop design method for commercial vehicle and piston steel preparation method

CN122020888ACN 122020888 ACN122020888 ACN 122020888ACN-122020888-A

Abstract

The invention provides a piston steel closed-loop design method for a commercial vehicle and a piston steel preparation method, and relates to the technical fields of metal material calculation design and ferrous metallurgy manufacturing. The design method comprises the steps of constructing a high-dimensional material database containing chemical components, process parameters and high-temperature thermophysical properties, constructing a multi-head self-attention mechanism neural network model based on a transducer architecture, accurately capturing nonlinear interaction between microelements V, mo and matrix elements, constructing an optimization model with ' maximum high-temperature yield strength at 500 ℃ and ' maximum heat conductivity ' as double targets in a low-silicon constraint space by using an NSGA-II algorithm, and performing global optimization. The invention solves the problems of poor heat dissipation and high cost caused by high alloy content of the traditional high-strength steel on the premise of 0 Ni element by AI auxiliary design and strict Si content control, and is suitable for manufacturing the engine piston of the commercial vehicle with high explosion pressure.

Inventors

SONG RENBO
MA WEITAO
Rao Yanjun
WANG XINWEI
Ren Shuhao
ZHANG ZIJIAN
ZHANG ZHEYUE

Assignees

北京科技大学

Dates

Publication Date: 20260512
Application Date: 20260114

Claims (10)

1. The design method of the piston steel closed loop of the commercial vehicle is characterized by comprising the following steps of: S1, establishing a Gao Weire physical property database, namely collecting historical production data and thermodynamic calculation data of steel for an internal combustion engine piston, and constructing a multidimensional dataset; S2, attention mechanism feature coding, namely constructing a deep neural network prediction model, calculating covariance matrixes among the alloy element features, and capturing nonlinear interaction of trace elements under a low silicon substrate and influence on lattice distortion; S3, double-target evolution optimizing, namely defining an objective function vector Wherein As a function of the cost of the raw materials, Performing iterative search in a constraint space of low silicon components to output an optimal solution set; And S4, closed loop iteration and decision, namely selecting an optimal formula from the optimal solution set in the S3 by adopting an inflection point identification method, performing small furnace smelting and performance test, feeding actual measurement data back to the multidimensional data set in the S1, and triggering online modeling of the model.
2. The method for designing a closed loop of piston steel for a commercial vehicle according to claim 1, wherein the input characteristics of the multidimensional dataset in S1 comprise mass fraction C, si, mn, cr, mo, V, ni, al, S, P, austenitizing temperature, tempering temperature and cooling rate, and the output characteristics mainly comprise room temperature mechanical properties, 500 ℃ high temperature yield strength and 500 ℃ thermal conductivity.
3. The method for designing a piston steel closed loop for a commercial vehicle according to claim 1, wherein the thermodynamic calculation data in S1 is thermodynamic Calphad data.
4. The method for designing a piston steel closed loop of a commercial vehicle according to claim 1, wherein the deep neural network prediction model in S2 is based on a transducer architecture, and a Multi-Head Self-attribute mechanism is used to calculate a covariance matrix between the characteristics of each alloy element.
5. The method for designing a closed loop for piston steel of a commercial vehicle according to claim 4, wherein the Multi-Head Self-Attention mechanism in S2 comprises h=4-8 Attention heads, and the Attention weight matrix calculation formula of the i-th Head is: Wherein, the Respectively a query, a key and a value matrix, The model is used for guiding the optimization direction by analyzing the weight relation between V and Mo and between Si and the thermal conductivity through thermodynamic diagram.
6. The method for designing the piston steel closed loop of the commercial vehicle according to claim 1, wherein the iterative search in the constraint space of the low silicon component in the step S3 is performed in the constraint space of the low silicon component with Si less than or equal to 0.35% by adopting NSGA-II, and the output optimal solution set is a Pareto Front optimal solution set.
7. The method for designing a piston steel closed loop for a commercial vehicle according to claim 1, wherein the comprehensive performance function in S3 The method comprises the following steps: Wherein the method comprises the steps of At a yield strength of 500C, Is a thermal conductivity at a temperature of 500 ℃, 、 Is a weight coefficient, and when the predicted thermal conductivity is lower than 32W/(mK), a penalty term is applied To force the population to converge toward the region of high thermal conductivity.
8. The method for designing the piston steel closed loop of the commercial vehicle according to claim 1, wherein the inflection point identification method is adopted in the step S4 to select the chemical components with the weight percentage of ：C 0.38-0.45%,Si 0.15-0.35%,Mn 0.70-1.10%,Cr 1.00-1.30%,Mo 0.20-0.40%,V 0.08-0.15%,P≤0.015%,S≤0.015%,Al 0.015-0.035%, and the balance of Fe and unavoidable impurities from the Pareto Front optimal solution set of the step S3; the microstructure of the commercial vehicle piston steel is tempered sorbite, the prior austenite grain size is more than or equal to 8 levels, MC type and M 23 C 6 type nano carbides which are mainly VC and have the size less than or equal to 20nm are dispersed in a matrix, the high-temperature yield strength of the commercial vehicle piston steel at 500 ℃ in a quenched and tempered state is more than or equal to 800MPa, and the thermal conductivity of the commercial vehicle piston steel at 500 ℃ is more than or equal to 32W/(m.K).
9. The piston steel preparation method based on the commercial vehicle piston steel closed-loop design method of claim 1 is characterized in that the piston steel preparation method is a preparation method for selecting an optimal formula from Pareto Front optimal solutions in S3 in a centralized manner by adopting an inflection point identification method in S4, and comprises the following steps: Step 1, smelting, namely, electric furnace/converter+LF refining+VD vacuum treatment, and after VD is broken, feeding V-Fe, mo-Fe and Ca-Si wire for smelting to obtain piston steel ingots; Step2, forging, namely heating the piston steel cast ingot in the step 1 to a homogenization temperature for heat preservation, then starting forging, and performing stack cooling after forging to obtain a piston steel forging material; Step 3, performing preliminary heat treatment, namely normalizing the piston steel forging stock in the step 2 to obtain a piston steel normalized forging material; And 4, tempering, namely carrying out oil quenching on the piston steel normalizing forging material in the step 3, and then carrying out high-temperature tempering to finally obtain a finished product of the piston steel for the commercial vehicle.
10. The method for manufacturing piston steel for a closed-loop design method for piston steel for a commercial vehicle according to claim 9, wherein the room-temperature mechanical properties of the piston steel for a commercial vehicle in the step 4 are that the tensile strength is 1000-1250MPa, the yield strength is 900-1100MPa, the yield ratio is 0.85-0.92, the elongation is 12-18%, the product of strength and elongation is 15-22GPa%, the impact power is 40-80J, the hardness is 35-42HRC, the elastic modulus is 206-215GPa, the high-temperature yield strength is 800-900MPa, the elastic modulus at 500 ℃ is 170-190GPa, and the thermal conductivity at 500 ℃ is 32-36W/(m·k).

Description

Piston steel closed-loop design method for commercial vehicle and piston steel preparation method Technical Field The invention relates to the technical field of metal material calculation design and ferrous metallurgy manufacturing, in particular to a piston steel closed-loop design method of a commercial vehicle and a piston steel preparation method, which are developed by utilizing an artificial intelligent deep learning model and a multi-objective evolutionary algorithm, and are low-cost, high-heat-conductivity and high-heat-strength alloy steel special for manufacturing a high-explosion-pressure and high-heat-load commercial vehicle engine piston and a manufacturing process thereof. Background With the increasingly stringent global requirements for energy conservation and emission reduction of commercial vehicles (such as emission standards of European VI and national VI), heavy duty diesel engines are evolving towards ultra-high explosion pressures (P max >220bar, even up to 250 bar) and high power density. Under the working condition, the piston is used as a heart part of an engine, the working environment is extremely bad, the piston needs to bear huge periodical gas explosion pressure and reciprocating inertia force, and the temperature of the top part of the piston (particularly the throat of a combustion chamber) is kept at 450-520 ℃ for a long time and bears severe cold-hot alternation. At present, conventional piston steels (e.g., 42CrMo4, 38MnVS 6) have been difficult to meet. When the temperature of the traditional 42CrMo4 exceeds 500 ℃, the matrix is seriously softened, the yield strength is reduced to below 600MPa, and the throat is easily cracked due to high-temperature creep. In order to solve the problem of high temperature strength, the prior art mainly adopts a high alloying route (such as adding a large amount of Ni and W) or a high silicon solid solution strengthening route (adding 0.8-1.2% of Si). However, the prior art solutions described above have a serious physical disadvantage in that the thermal conductivity is greatly reduced. Scientific research shows that Si and Ni are the elements in steel that are the most detrimental to thermal conductivity. High amounts of Si cause severe lattice distortions, strongly scattering electrons and phonons (Phonon Scattering), leading to a sharp drop in the thermal conductivity of the steel at high temperatures (typically below 30W/mK, even as low as 26-28W/mK). Under the working condition of high explosion pressure of 220bar or more, if the heat conduction of the piston material is poor, huge heat generated by the combustion chamber cannot be timely conducted to the cooling oil cavity at the bottom through the piston body, and the temperature at the top of the piston can be caused to form heat accumulation. This not only accelerates the high temperature oxidation and corrosion of the material, but also causes coking of the engine oil, forming a vicious circle, eventually leading to ablative failure of the piston. For example, chinese patent CN119980069A discloses a high-strength and high-toughness low-heat-conductivity steel for a commercial vehicle engine and a preparation method, and obviously, the component content selection of the steel for the piston cannot be accurately matched with the current optimal solution, in the preparation method, the selection of a smelting method, casting blank heat treatment, controlled rolling air cooling and tempering heat treatment and the influence on the structure of the prepared steel do not reach ideal effects, and particularly, the heat conductivity of the prepared steel is lower than 30W/m.K at 500 ℃, and the yield strength cannot reach the level of ultrahigh yield strength (more than or equal to 800 MPa). Chinese patent CN114807745A discloses a steel for automobile piston pins and a manufacturing method thereof, wherein more alloy elements of the steel are selected and need to meet the matching relation among the alloy elements, the preparation method is complex in operation process, high in operation difficulty, and after rolling, the steel is subjected to spheroidizing annealing by an annealing furnace, the high-temperature yield strength is lower than 800MPa, and the highest temperature of the piston pin can reach about 350 ℃ when an automobile engine runs, so that excellent high-temperature strength and heat conductivity at 500 ℃ can not be obtained obviously. Chinese patent CN117778901a discloses a steel for a damping piston rod for an automobile and a production method thereof, which has more alloy element selection, particularly has higher cost of high-cost alloy element, has higher difficulty in adding nano reinforcing phase, can obviously not obtain high-performance steel with dispersed nano reinforcing phase distribution only through simple smelting, forging and heat treatment procedures, and in addition, uniform distribution of a mixture formed by mixing four rare earth elements of the s