CN115198214B

CN115198214B - Manufacturing method of marine diesel engine air valve capable of regulating and controlling mixed grain boundary

Info

Publication number: CN115198214B
Application number: CN202210523124.2A
Authority: CN
Inventors: 权国政; 张钰清; 赵江; 余炎泽; 盛雪; 杨焜; 雷盛; 张渝
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2022-05-13
Filing date: 2022-05-13
Publication date: 2023-01-24
Anticipated expiration: 2042-05-13
Also published as: CN115198214A

Abstract

The invention relates to the technical field of metal plastic forming in material processing engineering, in particular to a manufacturing method of a marine diesel engine air valve for regulating and controlling mixed grain boundaries, which comprises the steps of regulating and controlling the mixed grain boundaries of the marine diesel engine air valve in advance through simulation, carrying out simulation design and optimization on processing parameters for manufacturing the marine diesel engine air valve, and determining suggested processing parameters, wherein the processing parameters comprise cold rolling deformation and electric upsetting process parameters; then, the initial bar stock for manufacturing the marine diesel valve is subjected to cold rolling pretreatment and electric upsetting processing with reference to the suggested processing parameters, thereby completing the manufacture of the marine diesel valve. The method can improve the manufacturing method of the gas valve, regulate and control the mixed grain boundary network for grain refinement and high cracking, and further improve the related comprehensive performance of the gas valve and the grain boundary.

Description

Manufacturing method of marine diesel engine air valve capable of regulating and controlling mixed grain boundary

Technical Field

The invention relates to the technical field of metal plastic forming in material processing engineering, in particular to a manufacturing method of a marine diesel engine air valve for regulating and controlling mixed grain boundaries.

Background

The ship industry is a modern comprehensive and strategic industry for providing high-end technical equipment for water traffic, ocean resource development and national defense construction. In the strategy of 'ocean dream and deep blue', the two-stroke diesel-powered low-speed machine is the 'heart' of ocean-going transport ships, maritime work ships and special ships.

The power of a low-speed diesel engine is continuously increased by the aid of the giant ocean equipment with the deep blue strategy, high-load strengthening of a combustion chamber is achieved by the aid of high-efficiency combustion-exhaust, the number of faults of exhaust valves of hot-end movable parts is about 15% of the number of faults of the whole engine, and the diesel engine is reduced and even suddenly damaged due to failure. The exhaust valve with the largest specification in the world at present is made of Ni80A nickel-based superalloy, the diameter of a rod is 110mm, the diameter of a disc is 525mm, the length of the rod is 1600mm, and the change rate of the section of the rod disc is 23; when in forming, the length of an initial blanking rod blank is 4000mm, the length of a material gathering deformation section rod is 2500mm, and the total upsetting ratio reaches 23. At present, the known manufacturing of the rod-disc type components depends on the combination of electric upsetting material forming and die forging net forming process. However, as the electric upsetting deformation body is heated for a very long time, such as 80 minutes of the electric upsetting of the world maximum specification gas valve, the grain growth coarsening effect of the partial region of the deformation body is far beyond dynamic recrystallization refinement, which is enough to coarsen 7.5 grade initial grains to 1 grade or even dissimilarity. And the free upsetting flowing filling mechanism of the poly blank during the subsequent die forging can not fully activate dynamic recrystallization, so that the defect of coarsening of crystal grains left by the electric upsetting can not be relieved. This results in accelerated crack propagation of grain boundary in the service process of the gas valve, which leads to the decrease of toughness and creep resistance, often causing the power reduction of the prime mover and even the sudden damage of the combustion chamber. The low-temperature cracking of the nickel-based alloy is considered in production, and the grain growth can be inhibited only by inhibiting the electric upsetting temperature within a very limited range. In conclusion, large-size air valves are extremely difficult to realize fine grain reinforcement.

The crystal boundary engineering advances the alloy strengthening idea, and the low-stacking fault energy face-centered cubic structure alloy has a low sigma CSL special crystal boundary (namely sigma 3) under the specific energy storage condition ⁿ Grain boundary, n =1,2,3) and dynamic recrystallization associated with a mutual excitation phenomenon, the former ∑ 3 ⁿ The crystal boundary fully cracks the latter general free crystal boundary to form a mixed crystal boundary network structure containing a large number of crack bridges, and the fatigue weakening resistance and the cracking resistance of the crystal boundary are obviously improved. However, the existing process reduces the grain growth by controlling the electric upsetting forming temperature in a narrow parameter range, but also inhibits sigma 3 ⁿ Grain boundary nucleation.

Under the situation that the service requirement of the two-stroke low-speed diesel engine air valve is higher and higher, the manufacturing method of the air valve needs to be perfected, the mixed grain boundary network for grain refinement and high cracking is regulated and controlled, and the related comprehensive performance of the air valve and the grain boundary is further improved, so that the service performance of the low-speed engine air valve is improved.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the method for manufacturing the marine diesel engine air valve for regulating and controlling the mixed grain boundary, which can perfect the air valve manufacturing method, regulate and control the mixed grain boundary network for grain refinement and high cracking, and further improve the relative comprehensive performance of the air valve and the grain boundary.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method for manufacturing a marine diesel engine air valve for regulating and controlling mixed grain boundaries comprises the steps of regulating and controlling the mixed grain boundaries of the marine diesel engine air valve in advance through simulation, carrying out simulation design and optimization on machining parameters for manufacturing the marine diesel engine air valve, and determining machining parameters which are recommended to use, wherein the machining parameters comprise cold rolling deformation and electric upsetting process parameters; then, the initial bar stock for manufacturing the marine diesel valve is subjected to cold rolling pretreatment and electric upsetting processing with reference to the suggested processing parameters, thereby completing the manufacture of the marine diesel valve.

Preferably, the electric upsetting process parameter comprises an initial process parameter and a high-order variation parameter; the initial technological parameters comprise the chamfer size of the rod blank, the clamping length, the preheating time and the preheating current, and the high-order variation parameters comprise the upsetting force, the current and the anvil retreating speed.

Preferably, the simulation design and optimization of the processing parameters comprises:

s1, developing cold compression experiments of small samples with different downward pressures, testing the sub-crystalline formation rule of processing materials with different cold deformation amounts, and fitting to establish a relational expression of dislocation density and cold strain;

s2, taking a standard thermophysical simulation compression experiment for the cold-pressed sample, developing the hot compression experiments at different temperatures and stress rates, and observing and statistically analyzing crystal grains and crystal boundaries of the sample treated under different deformation conditions; establishing a dynamic recrystallization model under the premise of cold deformation pre-stored energy according to a JMAK equation configuration; deducing and constructing a dislocation density evolution model of the cold pressing-hot pressing whole process by adopting a K-M dislocation density model, a static recovery dislocation density model and a two-stage K-M dislocation density model; deducing the establishment of a low dislocation density with grain size, dynamic recrystallization volume fraction andCSLΣ3 ⁿ a grain boundary density evolution model; testing the grain growth behaviors under different initial grain sizes, temperatures and time and constructing a grain growth model;

s3, introducing physical quantity of the pre-stored energy based on the influence of the cold deformation pre-stored energy on the dynamic recrystallization model and the hot compression dislocation density model, and establishing a dynamic recrystallization model containing the pre-stored energy and a response model of the pre-stored energy on the dislocation density under the cold-hot deformation condition;

s4, constructing a machining simulation system based on the models and the relational expressions in the S1-S3, and performing simulation machining according to machining parameters; analyzing the experiment results of S2-S3 and the key parameters to obtain a key parameter relation graph; the key parameter relation graph is used for showing the change rule of the dynamic recrystallization volume fraction, the energy storage, the grain size and the low CSL sigma 3n grain boundary density along with the thermal deformation temperature and the strain rate;

s5, designing processing parameters in the processing simulation model, and performing simulation processing;

s6, judging whether the simulation processing result meets the preset requirement, if not, turning to S7, and if so, turning to S8;

s7, analyzing a key parameter adjusting strategy according to the key parameter relation graph, wherein the key parameter adjusting strategy comprises a cold rolling strain amount, an electric upsetting process temperature, a strain rate and/or an adjusting direction of the strain amount; analyzing a suggested adjusting direction of the processing parameter based on a key parameter adjusting strategy; after the machining parameters are adjusted according to the suggested adjustment direction, the adjusted machining parameters are subjected to simulation machining through a machining simulation system, and the process goes to S6;

and S8, taking the machining parameters as machining parameters which are recommended to be used.

Preferably, in S4, the machining simulation system includes a cold rolling finite element analysis model and a dynamic coupling electric upsetting finite element analysis model;

the process of constructing the machining simulation system comprises the following steps: firstly, establishing a cold rolling finite element model for calculating dislocation density and pre-stored energy in the cold rolling process according to cold rolling deformation; then, a field quantity inheritance subprogram is constructed for inheriting cold for the electric upsetting rod blankPre-stored energy, dislocation density and equivalent plastic strain field amount after rolling; then, constructing an electric upsetting finite element model for carrying out electric upsetting simulation according to electric upsetting technological parameters to obtain electric upsetting process quantity, wherein the electric upsetting process quantity comprises temperature, strain rate and stress data during electric upsetting; then, a dynamic recrystallization model, a grain growth model and a low CSL sigma 3 model containing pre-stored energy are used ⁿ And embedding the crystal boundary density evolution model, the dislocation density model and a response model of pre-stored energy to dislocation density into the electric upsetting finite element model to obtain a dynamic coupling electric upsetting finite element analysis model.

Preferably, in the step S5, during the simulation process, firstly, a cold rolling process is simulated by a cold rolling finite element model, the dislocation density and the pre-stored energy during the cold rolling are calculated according to the cold rolling deformation, and the electric upsetting rod blank is given; then simulating an electric upsetting deformation process according to the dynamic coupling electric upsetting finite element analysis model;

the simulation electric upsetting deformation process according to the dynamic coupling electric upsetting finite element analysis model comprises the following steps: performing electric upsetting simulation according to electric upsetting process parameters through an electric upsetting finite element model to obtain electric upsetting process quantity; calculating a dislocation density model, a grain growth model and a dynamic recrystallization model containing pre-stored energy according to the electric upsetting process quantity to obtain key indexes, wherein the key indexes comprise dislocation density, stored energy, recrystallization volume fraction and grain size; then, low CSL sigma 3 is calculated according to the key index ⁿ Grain boundary density model to obtain low CSL sigma 3 ⁿ Grain boundary density distribution.

Preferably, in S4, the key parameter relationship diagram includes: graph of grain size and energy storage at different heat distortion temperatures and strain rates, dynamic recrystallization volume fraction, and low CSL sigma 3 ⁿ Relationship diagram of grain boundary density, energy storage and low CSL sigma 3 ⁿ Plot of grain boundary density, grain size and low CSL ∑ 3 ⁿ Graph of grain boundary density.

Preferably, in S6, the simulated machining result includes a grain size and a low CSL Σ 3n grain boundary density; the preset requirements include low CSL Σ 3 in the simulation results ⁿ The grain boundary density is larger than the preset density, and the grain size is smaller than the preset size.

Preferably, the initial bar stock for manufacturing the marine diesel valve is subjected to cold rolling pretreatment and electric upsetting processing by referring to the suggested processing parameters, and the specific steps for manufacturing the marine diesel valve comprise:

cold rolling pretreatment: according to the cold rolling deformation in the suggested processing parameters, carrying out cold rolling pre-deformation on the front section of the initial rod blank;

and (3) mechanical processing: machining the cold-rolled rod blank to make the surface of the cold-rolled rod blank smooth;

electric upsetting processing: according to the electric upsetting technological parameters in the suggested machining parameters, carrying out electric upsetting material on the machined rod blank to obtain an electric upsetting piece;

heating and heat preservation: carrying out solid solution line heat preservation on the obtained electric upsetting piece;

die forging and forming: performing die forging forming on the electric upsetting piece after heat preservation to obtain an air valve;

and (3) aging treatment: and carrying out aging heat treatment on the air valve to adjust the homogenized air valve structure.

Preferably, in the aging treatment step, the temperature of the aging heat treatment is 690-710 ℃, the time of the aging heat treatment is 16-18 h, and air cooling is carried out after the aging heat treatment.

Preferably, between the electric upsetting step and the heating and holding step, the method further comprises the following steps:

a heat supplementing treatment step: performing heat supplementing on the head of the blank formed by the electric upsetting material; wherein the heat supplementing temperature is 1000-1050 deg.C, and the heat supplementing time is 15-30min.

Compared with the prior art, the invention has the following beneficial effects:

1. when the front section of the initial rod blank is subjected to cold rolling predeformation, a large amount of subgrain structures with high dislocation density can be obtained by controlling the deformation amount of the front section of the blank. When the preprocessed rod blank is subjected to electric upsetting, because the front section of the rod blank stores higher deformation energy in the form of dislocation density through a cold rolling process, the sub-crystal boundary with high dislocation density can become a dynamic recrystallization and twin crystal nucleation point in the electric upsetting process to increase the nucleation rate, and meanwhile, the stored energy in the cold rolling process also provides driving force for crystal boundary migration in the electric upsetting process to promote the occurrence of dynamic recrystallization and the formation of low sigma CSL crystal boundary. And the mixed grain boundary network with refined grains and high cracking performance is obtained by controlling the cold rolling deformation and the electric upsetting forming process parameters.

An original air valve electric upsetting-forging forming process is adopted, and the electric upsetting forming temperature is inhibited, so that only coarse-grained, mixed-grained and insufficiently cracked tissues can be obtained; by adopting the gas valve manufacturing method provided by the patent, the high-dislocation-density sub-grain boundary is obtained through cold rolling pre-stored energy so as to stimulate dynamic recrystallization and low sigma CSL grain boundary nucleation in the ultra-long range electric upsetting process, and a uniform fine-grain and high-cracking mixed grain boundary network can be obtained. The crystal grains of the rod blank subjected to cold rolling pretreatment are obviously refined during electric upsetting forming, and the low CSL sigma 3 of the outer contour of the electric upsetting garlic head ⁿ The grain boundary density is obviously improved, and the garlic head center is low in CSL sigma 3 ⁿ The region of lower grain boundary density values is significantly reduced.

The experimental result shows that after cold pressing and pre-deformation, the dynamic recrystallization degree is remarkably improved to more than 80 percent from 8.3 percent of the non-cold pressing pretreatment; meanwhile, the crystal grains are fully refined and are fully cracked by the low sigma CSL crystal boundary to form a more ideal mixed crystal boundary network. The grain boundary density of the low sigma CSL before the precooling deformation regulation is 0.0252 mu m ^-1 After precooling deformation regulation, the thickness is as high as 0.2429 mu m ^-1 . Further illustrates that the high dislocation density subgrain boundary formed in the cold deformation process can stimulate dynamic recrystallization and low sigma CSL grain boundary nucleation in the thermal deformation process, thereby obtaining a uniform and fine-grained and high-cracking mixed grain boundary network.

Compared with the prior art, the method can perfect the gas valve manufacturing method, regulate and control the mixed grain boundary network with refined and high-cracking grains, and further improve the related comprehensive performance of the gas valve and the grain boundary.

2. In order to reduce the number of machining experiments and the investment cost of the experiments, the invention also provides a method for designing and optimizing the machining parameters. By constructing a processing simulation system, the grain size and the low CSL sigma 3 under different cold-heat deformation parameters are realized ⁿ And predicting the grain boundary density, and accurately and quickly optimizing the machining parameters by constructing a key parameter relation graph to obtain the machining parameters which are suggested to be used.The machining parameters which are suggested to be used are directly used for machining subsequently, so that not only can the cost be reduced, but also the time can be saved, and the efficiency can be improved.

3. The processing simulation model in the method realizes the full-flow dynamic coupling of cold rolling and electric upsetting and the grain size, energy storage and low CSL sigma 3 in the ultra-long-range electric upsetting process ⁿ And the real-time monitoring and the distribution visualization of key indexes such as grain boundary density and the like. By combining the key parameter relational graph, the low CSL sigma 3 with high grain refinement and high strength can be obtained by optimizing the processing parameters (namely the cold rolling deformation and the electric upsetting process parameters) ⁿ Grain boundary density.

4. The critical parameter relationship diagram shows the grain size and the low CSL sigma 3 ⁿ The change rule of the grain boundary density along with the temperature and the strain rate; when the processing simulation result does not meet the preset requirement (i.e. low CSL sigma 3) ⁿ Grain boundary density is less than or equal to a preset density, or grain size is greater than or equal to a preset size), a key parameter adjustment strategy, namely, adjustment directions of cold rolling strain, electric heading process temperature, strain rate and/or strain amount, can be obtained according to a key parameter relation graph. The change of the key parameters is directly related to the change of the processing parameters (cold rolling deformation and electric upsetting process parameters), so that the adjustment direction of the processing parameters can be analyzed according to the key parameter adjustment strategy. By the mode, the machining parameters can be gradually optimized, and the machining parameters with the simulated machining results meeting the requirements are finally obtained.

In other words, the method takes the cold rolling strain, the electric upsetting process temperature, the strain rate and the strain quantity as intermediate reference quantities, correlates the machining parameters with the simulated machining result, and is difficult to understand the relationship between the machining parameters and the simulated machining result if the intermediate reference quantities are lacked. With these intermediate references, a reasonable optimization can be carried out when optimizing the processing parameters.

Drawings

For purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made in detail to the present invention as illustrated in the accompanying drawings, in which:

FIG. 1 is a schematic flow diagram of a manufacturing method of a marine diesel engine gas valve for regulating and controlling mixed grain boundaries according to the invention;

FIG. 2 is a schematic diagram of a forming effect and an expected effect of a grain boundary of a manufacturing process for regulating and controlling a mixed grain boundary of a gas valve of a marine diesel engine;

FIG. 3 is a flow chart of an implementation of an optimization system for regulating and controlling a gas valve mixed grain boundary of a marine diesel engine;

FIG. 4 is a schematic structural diagram of a mixed grain boundary unified model;

FIG. 5 shows a cold rolling-ultra-long range electric upsetting full-process multi-field multi-scale analysis algorithm and low CSL sigma 3 ⁿ A schematic calculation flow chart of the grain boundary density;

FIG. 6 is a schematic flow chart illustrating a processing parameter optimization step in the method for manufacturing the gas valve of the marine diesel engine for regulating and controlling the mixed grain boundary according to the invention;

FIG. 7 is a graphical illustration of a relationship between key parameters analyzed in the process of the optimization step of process parameters;

FIG. 8 is a diagram showing a simulation example of dislocation density distribution of a bar stock after three passes with a total cold rolling deformation of 6mm;

FIG. 9 is a diagram showing a simulation example of dislocation density distribution of an electric upsetting rod blank after field quantity inheritance is performed on the cold-rolled rod blank;

FIG. 10 shows the temperature, grain size and low CSL ∑ 3 during electric upsetting of cold rolled bar stock ⁿ The grain boundary density distribution is shown in the chart.

FIG. 11 is a graph comparing preliminary results of hot-deformed mixed grain boundary network formation after different amounts of cold deformation pretreatment;

FIG. 12 is a graph of the temperature, grain size and low CSL Σ 3 for an un-cold rolled bar stock during electrical heading ⁿ A graph is displayed on the density distribution condition of the grain boundary;

FIG. 13 is a graph comparing the maximum temperature change during electro-upsetting of cold rolled and cold rolled bar blanks;

fig. 14 is a graph comparing the change of the maximum grain size during the electric upsetting formation of the cold rolled and non-cold rolled rod blanks.

Detailed Description

The following is further detailed by the specific embodiments:

the invention provides a manufacturing method of a marine diesel engine air valve for regulating and controlling a mixed grain boundary, which comprises the steps of regulating and controlling the mixed grain boundary of the marine diesel engine air valve in advance through simulation, carrying out simulation design and optimization on machining parameters for manufacturing the marine diesel engine air valve, and determining machining parameters which are recommended to use, wherein the machining parameters comprise cold rolling deformation and electric upsetting process parameters; then, the initial bar stock for processing and manufacturing the valve of the marine diesel engine is subjected to cold rolling pretreatment and electric upsetting processing according to the processing parameters suggested to be used, and the manufacturing of the valve of the marine diesel engine is completed.

The method of the invention determines the recommended processing parameters through the pre-simulation design and optimization, and then the specific process for manufacturing the marine diesel engine gas valve by referring to the recommended processing parameters is shown in figure 1, which comprises the following steps:

cold rolling pretreatment: according to the cold rolling deformation in the suggested processing parameters, carrying out cold rolling pre-deformation on the front section of the initial rod blank; by controlling the deformation of the front section of the blank, a large amount of sub-crystalline structures with high dislocation density are obtained.

And (3) mechanical processing: machining the cold-rolled rod blank to make the surface of the rod blank smooth;

electric upsetting processing: according to the electric upsetting technological parameters in the suggested machining parameters, carrying out electric upsetting material on the machined rod blank to obtain an electric upsetting piece; because the front section of the bar blank stores higher deformation energy in the form of dislocation density through a cold rolling process, the sub-boundaries with high dislocation density can become nucleation points of dynamic recrystallization and twin crystals in the electric upsetting process to increase the nucleation rate of the dynamic recrystallization and the twin crystals, and meanwhile, the stored energy in the cold rolling process also provides driving force for the migration of the grain boundaries in the electric upsetting process, so that the dynamic recrystallization and the formation of low sigma CSL grain boundaries are promoted. And the mixed grain boundary network with refined grains and high cracking performance is obtained by controlling the cold rolling deformation and the electric upsetting forming process parameters.

Heating and heat preservation: carrying out solid solution under-line heat preservation on the obtained electric upsetting piece; in specific implementation, before the heating and heat preservation step is carried out, heat supplementing can be carried out on the head of the blank formed by the electric upsetting material; wherein the heat supplementing temperature is 1000-1050 ℃, and the heat supplementing time is 15-30min; in the heat preservation treatment process, the heat preservation temperature can be 1000-1050 ℃, and the heat preservation time can be 15-30min; the total time length of the heat supplementing time length and the heat preservation time length is within 60 min.

Die forging and forming: adopting a flat die or a mode of matching a male die and the flat die to perform die forging forming on the electric upsetting piece after heat preservation to obtain the air valve;

and (3) aging treatment: and carrying out aging heat treatment on the air valve to adjust the homogenized air valve structure. In the specific implementation, the temperature of the aging heat treatment can be 690-710 ℃, the time of the aging heat treatment can be 16-18 h, and the air cooling is carried out after the aging heat treatment.

When the front section of the initial rod blank is subjected to cold rolling predeformation, a large amount of subgrain structures with high dislocation density can be obtained by controlling the deformation amount of the front section of the blank. When the preprocessed rod blank is subjected to electric upsetting, because the front section of the rod blank stores higher deformation energy in the form of dislocation density through a cold rolling process, the sub-crystal boundary with high dislocation density can become a dynamic recrystallization and twin crystal nucleation point in the electric upsetting process to increase the nucleation rate, and meanwhile, the stored energy in the cold rolling process also provides driving force for crystal boundary migration in the electric upsetting process to promote the occurrence of dynamic recrystallization and the formation of low sigma CSL crystal boundary. And the mixed grain boundary network with refined grains and high cracking performance is obtained by controlling the cold rolling deformation and the electric upsetting forming process parameters. An original air valve electric upsetting-forging forming process is adopted, and the electric upsetting forming temperature is inhibited, so that only coarse-grained, mixed-grained and insufficiently cracked tissues can be obtained; by adopting the gas valve manufacturing method provided by the patent, the high-dislocation-density sub-grain boundary is obtained through cold rolling pre-stored energy so as to stimulate dynamic recrystallization and low sigma CSL grain boundary nucleation in the ultra-long range electric upsetting process, and a uniform fine-grain and high-cracking mixed grain boundary network can be obtained.

A schematic diagram of the forming effect of the manufacturing process for regulating and controlling the mixed grain boundary of the gas valve of the marine diesel engine and the expected effect of the grain boundary are shown in fig. 2. The processing result shows that crystal grains of the rod blank subjected to cold rolling pretreatment are obviously refined during electric upsetting forming, and the low CSL sigma 3 of the outer contour of the electric upsetting garlic head ⁿ The grain boundary density is obviously improved, and the garlic head center is low in CSL sigma 3 ⁿ The region where the grain boundary density value is low is significantly reduced. The effect of a small Ni80A nickel-based superalloy sample after cold deformation pre-stored energy regulation is explained as follows: ni80A nickel base pairThe small samples of the alloy were pre-treated at cold reduction of 0%, 15%, 20%, 25% and 30% and then strained at 1273K at a strain rate of 0.1s ^-1 Isothermal hot compression was performed under a compression amount of 60% (true strain of 0.916). The experimental result shows that after cold pressing and pre-deformation, the dynamic recrystallization degree is remarkably improved to more than 80 percent from 8.3 percent of the non-cold pressing pretreatment; meanwhile, the crystal grains are fully refined and are fully cracked by the low sigma CSL crystal boundary to form an ideal mixed crystal boundary network. The grain boundary density of the low sigma CSL before the precooling deformation regulation is 0.0252 mu m ^-1 After precooling deformation regulation, the thickness is as high as 0.2429 mu m ^-1 . Further, the high dislocation density subgrain boundary formed in the cold deformation process can stimulate dynamic recrystallization and low sigma CSL crystal boundary nucleation in the hot deformation process, and then a uniform fine-grained and high-cracking mixed crystal boundary network is obtained.

The method can improve the manufacturing method of the gas valve, regulate and control the mixed grain boundary network for grain refinement and high cracking, and further improve the related comprehensive performance of the gas valve and the grain boundary.

The technical key point of the other aspect of the scheme of the invention is that the mixed grain boundary of the marine diesel engine air valve is regulated and controlled in advance through simulation, the simulation design and optimization are carried out on the machining parameters for manufacturing the marine diesel engine air valve, and the machining parameters which are recommended to be used are determined. In specific application implementation, the optimized design of the processing parameters can be applied to an optimization system for regulating and controlling the mixed grain boundary of the gas valve of the marine diesel engine, and the optimization system comprises a mixed grain boundary unified model, a mixed grain boundary prediction system, a cold rolling-ultra-long range electric upsetting full-process dynamic coupling finite element model and a cold-heat deformation parameter regulation and control mixed grain boundary module.

The mixed crystal boundary unified model is used for calculating dislocation density, energy storage, dynamic recrystallization volume fraction, grain size and low CSL sigma 3 under different cold-heat deformation parameters ⁿ The grain boundary density realizes the intergrowth of multiple mechanisms of solving dynamic recrystallization, grain growth and low sigma CSL grain boundary; mixed grain boundary prediction system for predicting grain size and low CSL sigma 3 under different cold-heat deformation parameters ⁿ Key indexes such as grain boundary density and the like and a key index relation graph established by display; cold rolling-super long distance electric upsetting full flow dynamic couplingSynthetic finite element model for dynamically monitoring grain size and low CSL sigma 3 ⁿ The evolution and visualization of key indexes such as grain boundary density and the like also provides an effective means for regulating and controlling the mixed grain boundary evolution in the electric upsetting process; the cold-hot deformation parameter regulation and control mixed crystal boundary module is used for regulating and controlling cold rolling deformation or comprehensively coordinating cold rolling deformation and electric upsetting high-order variation parameters to obtain grain refinement and high low CSL sigma 3 ⁿ Grain boundary density.

An implementation flow of the optimization system for regulating and controlling the mixed grain boundary of the marine diesel engine valve is shown in fig. 3. Firstly, a mixed grain boundary unified model is constructed. Then, a mixed grain boundary prediction system is developed based on the constructed mixed grain boundary unified model, and on one hand, the grain size and the low CSL sigma 3 under different cold-heat deformation parameters are realized ⁿ And on the other hand, the system also comprises a relationship diagram established among the key indexes, and can accurately identify the mixed grain boundary network parameter interval of grain refinement and high cracking. Because of the high-order variation of parameters such as upsetting force, current, anvil retreating speed and the like in the gas valve ultra-long range electric upsetting process, the mixed grain boundary regulation and control and the optimization of the multi-field multi-scale finite element model in the gas valve cold rolling-electric upsetting process are realized, therefore, corresponding subprograms are developed based on the built mixed grain boundary unified model, the MSC.Marc software multi-physics field coupling solution scheme is adopted to build the cold rolling-ultra-long range electric upsetting full-process dynamic coupling finite element model and implant the developed subprograms, and the grain size and the low CSL sigma 3 in the electric upsetting process are realized ⁿ And the real-time monitoring and the distribution visualization of key indexes such as grain boundary density and the like. During cold rolling-ultra-long range electric upsetting full-flow dynamic coupling finite element simulation, the distribution condition of key indexes needs to be monitored in real time, and if the grain refinement and the high low CSL sigma 3 are met ⁿ Outputting cold rolling and electric upsetting high-order variation parameters when the grain boundary density is required; if the temperature and the strain rate of the electric upsetting process are not met, the identified grain refinement and high low CSL sigma 3 parameters and the high CSL sigma 3 parameters are obtained by regulating and controlling high-order variation parameters such as force, current, anvil retreating speed and the like through a relation graph of key indexes in a mixed grain boundary prediction system ⁿ In the grain boundary density parameter interval, the grain refinement and the electric upsetting high-order variation parameters can be obtained by regulating and controlling the cold rolling deformation or comprehensively coordinating the cold rolling deformation and the electric upsetting high-order variation parametersHigh low CSL Σ 3 ⁿ Grain boundary density.

The construction method of the optimization system for regulating and controlling the mixed crystal boundary of the air valve of the marine diesel engine and the specific functions of each module are as follows:

mixed crystal boundary unified model:

as shown in FIG. 4, the mixed grain boundary unified model comprises a dynamic recrystallization model containing the physical quantity of the pre-stored energy, a grain growth model, a dislocation density model and a low CSL sigma 3 ⁿ And (5) a grain boundary density evolution model. The dynamic recrystallization model containing the pre-stored energy physical quantity is used for calculating the volume fraction of the dynamic recrystallization crystal and the size of the dynamic recrystallization crystal grain under different cold strains, different heat deformation temperatures, strain rates and strains. The grain growth model is used to calculate the grain size after growth at different temperatures and times. The dislocation density model comprises a dislocation density model in a cold deformation process and a dislocation density model in a hot deformation process, and is used for calculating the dislocation density in the whole process of reheating deformation after cold deformation. Low CSL Σ 3 ⁿ The grain boundary density model is used for calculating the energy storage and the low CSL sigma 3 in the reheating deformation process after cold deformation ⁿ And the grain boundary density is a model taking the grain size, the volume fraction of the dynamic recrystallization and the stored energy as variables, wherein the grain size can be calculated through a dynamic recrystallization model containing the physical quantity of the pre-stored energy and a grain growth model, the volume fraction of the dynamic recrystallization can be calculated through a dynamic recrystallization model containing the physical quantity of the pre-stored energy, and the stored energy can be calculated through the dislocation density. Furthermore, low CSL Σ 3 ⁿ The grain boundary density model can also be used to calculate low CSL Sigma 3 for thermal deformation only ⁿ Grain boundary density. Aiming at different cold-heat deformation parameters, the dislocation density, the energy storage and dynamic recrystallization volume fraction, the grain size and the low CSL sigma 3 in the processes of pre-storage under different cold strains and reheating deformation after cold deformation can be calculated according to the established mixed crystal boundary unified model ⁿ Grain boundary density.

Mixed grain boundary prediction system:

and developing calculation software aiming at a mixed grain boundary unified model and constructing a mixed grain boundary prediction system to realize the symbiotic effect of solving multiple mechanisms of dynamic recrystallization, grain growth and low sigma CSL grain boundary. Aiming at different cold strains andthe mixed crystal boundary prediction system can accurately predict the pre-stored energy, dislocation density, recrystallization volume fraction, grain size and low CSL sigma 3 under different cold-hot deformation conditions ⁿ The value of the grain boundary density and reveals the dynamic response rule of the indexes to the cold-heat deformation parameters. In addition, in order to accurately identify the parameter interval and the pre-energy storage condition of the mixed grain boundary network with refined and high cracking grains, the mixed grain boundary prediction system also comprises a relation graph of grain sizes and energy storage under different heat deformation temperatures and strain rates, a dynamic recrystallization volume fraction and low CSL sigma 3 ⁿ Relationship diagram of grain boundary density, energy storage and low CSL sigma 3 ⁿ Plot of grain boundary density, grain size and low CSL ∑ 3 ⁿ Based on the relationship graph of the key indexes, the grain refinement and the high low CSL sigma 3 can be searched and obtained ⁿ The interval of thermal deformation parameters of the grain boundary density and the pre-energy storage condition.

Cold rolling-overlength journey electric upsetting full process developments coupling finite element model:

and (3) carrying out subprogram development on the mixed grain boundary unified model based on a Visual Studio2015 program development tool and a Fortran language compiler. Establishing a cold rolling-ultra-long range electric upsetting full-process dynamic coupling finite element model by utilizing an MSC.Marc software multi-physical field coupling solving scheme, wherein the cold rolling-ultra-long range electric upsetting full-process dynamic coupling finite element model comprises a cold rolling finite element model and an electric-heat-force-energy-dislocation multi-field, deformation-crystal grain multi-scale dynamic coupling electric upsetting finite element analysis model. Firstly, establishing a rod blank cold rolling finite element model, and calculating dislocation density and pre-stored energy in the cold rolling process according to cold deformation parameters; then, a field quantity inheritance subprogram is developed to inherit the field quantities of pre-stored energy, dislocation density, equivalent plastic strain and the like after cold rolling on the electric upsetting rod blank; then, a dynamic recrystallization model, a grain growth model and a low CSL sigma 3 containing the physical quantity of the pre-stored energy are used ⁿ And a subprogram after programming of series models such as a crystal boundary density evolution model, a response model of pre-stored energy to dislocation density under a cold-hot deformation condition and the like is embedded into the electric upsetting finite element model, and an electric-heat-force-energy-dislocation multi-field and deformation-crystal grain multi-scale dynamic coupling electric upsetting finite element analysis model which accords with the reality and gives consideration to the calculation precision and efficiency is established.

Cold-hot deformation parameter control of mixed grain boundaries:

aiming at a certain fixed cold rolling deformation, based on the established electric-heat-force-energy-dislocation multi-field and deformation-crystal grain multi-scale dynamic coupling electric upsetting finite element analysis model, carrying out electric upsetting finite element simulation on the cold-rolled rod blank, and calculating dislocation density, energy storage, crystalline re-crystallization volume fraction, crystal grain size and low CSL sigma 3 under the conditions of different electric upsetting forming temperatures, strain and strain rate parameters through a subprogram ⁿ Grain boundary density; grain size and low CSL Sigma 3 if electro-upset formed ⁿ Low CSL ∑ 3 with grain boundary density not satisfying grain refinement and high ⁿ Grain boundary density requirement, the grain size and low CSL sigma 3 in the system are predicted according to the mixed grain boundary ⁿ The change rule of the grain boundary density along with the temperature, the strain rate and the strain, high-order variation parameters such as regulating force, current, anvil retreating speed and the like are subjected to electric upsetting finite element simulation, so that the parameters of the temperature and the strain rate in the electric upsetting process are subjected to identified grain refinement and high low CSL sigma 3 ⁿ The grain boundary density parameter interval.

Under the condition that the cold rolling deformation is not fixed, the cold rolling deformation can be regulated or comprehensively coordinated with the cold rolling deformation and the electric upsetting high-order variation parameters to obtain grain refinement and high low CSL sigma 3 ⁿ Grain boundary density. Firstly, performing cold rolling finite element simulation on a rod blank based on an established cold rolling finite element model, and controlling the cold rolling deformation of the rod blank; then, carrying out electric upsetting finite element simulation on the cold-rolled rod blank, and repeating the previous step until the requirements of grain refinement and high low CSL sigma 3 are met ⁿ Grain boundary density requirements.

FIG. 5 is a diagram of a specific multi-field multi-scale analysis algorithm and low CSL sigma 3 ⁿ And calculating the grain boundary density and implementing the flow. Firstly, a cold rolling process is calculated, when an iterative cycle starts, a rigidity matrix is called to calculate a structure field, a blank strain field is extracted to calculate dislocation density and pre-stored energy until the cold rolling process is finished. And then, deriving pre-stored energy and dislocation density data of the blank when cold rolling is finished, endowing the blank to the electric upsetting rod through a field quantity inheritance subprogram, and then calculating the electric upsetting ultra-long-range thermal deformation process. At the beginning of the iterative cycle, the electrical parameters and the boundary contact conditions are called to calculate the current field, and then the current field is focusedCalculating a temperature field by using the ear effect, the thermal parameters and the thermal boundary; then calling conditions such as rheological stress, upsetting force and the like, and calculating a structural field based on the current field and the temperature field; extracting data such as temperature, strain rate, stress and the like calculated by electricity-heat-force coupling, and calculating a dislocation density model, a crystal grain growth model and a dynamic recrystallization model containing pre-stored energy physical quantity based on the data to obtain key indexes such as dislocation density, stored energy, recrystallization volume fraction, crystal grain size and the like; then calculating low CSL sigma 3 based on the obtained key index ⁿ Grain boundary density model to obtain low CSL ∑ 3 ⁿ Grain boundary density distribution; and judging whether the electric upsetting process is finished or not, and if not, continuing to perform the next increment step until the analysis is finished.

Based on the design thought, the invention further adds a processing parameter optimization step before the cold rolling pretreatment step: and performing simulation optimization on the machining parameters to obtain machining parameters which are recommended to be used. Wherein the processing parameters comprise cold rolling deformation and electric upsetting technological parameters; the electric upsetting process parameters comprise initial process parameters and high-order variation parameters; the initial technological parameters comprise the chamfer size of the rod blank, the clamping length, the preheating time and the preheating current, and the high-order variation parameters comprise the upsetting force, the current and the anvil retreating speed.

Specifically, the process flow for optimizing the processing parameters is shown in fig. 6, and includes the following steps:

s1, developing cold compression experiments of small samples with different pressing amounts, testing the sub-crystal formation rules of processing materials with different cold deformation amounts, and fitting and establishing a relational expression of dislocation density and cold strain;

s2, performing a standard thermophysical simulation compression experiment on the cold-pressed sample, performing a hot compression experiment under different temperatures and stress rates, and performing crystal grain and crystal boundary observation and statistical analysis on the sample treated under different deformation conditions; establishing a dynamic recrystallization model under the premise of cold deformation pre-stored energy according to a JMAK equation configuration; deducing and constructing a dislocation density evolution model of the cold pressing-hot pressing whole process by adopting a K-M dislocation density model, a static recovery dislocation density model and a two-stage K-M dislocation density model; deriving and establishing the crystal grain size and dynamic recrystallizationDynamic low CSL sigma 3 with integration number and dislocation density as variables ⁿ A grain boundary density evolution model; testing the grain growth behaviors under different initial grain sizes, temperatures and time and constructing a grain growth model;

for the sake of understanding, in this embodiment, an Ni80A nickel-based superalloy valve is used as an example for description. Firstly, developing cold compression experiments of small samples under different pressing quantities, testing the formation rule of Ni80A nickel-based superalloy subgrain with different cold deformation quantities, and fitting and establishing a relational expression of dislocation density and cold strain as formula (1);

in the formula: rho _ε Dislocation density during cold compression; epsilon _pres Is cold pressing pre-strain.

And taking a standard thermophysical simulation compression sample from the cold-pressed sample, carrying out hot compression tests at different temperatures and stress rates, and observing and statistically analyzing crystal grains and crystal boundaries of the Ni80A nickel-based superalloy sample treated under different deformation conditions. Establishing a dynamic recrystallization model under the cold deformation pre-stored energy condition according to a JMAK equation configuration as shown in a formula (2);

in the formula: x _drx Is the dynamic recrystallization volume fraction; ε is the strain;

is the strain rate; epsilon _c Is the critical strain; epsilon _p The strain corresponding to the peak value of the rheological stress; epsilon _0.5 The strain when the integral number of the dynamic recrystallization reaches 50%; d _drx Is a dynamically recrystallized grain size; r is an Avogastron constant; t is the temperature.

The dislocation density evolution model of the cold pressing-hot pressing whole process is deduced and constructed by adopting a K-M dislocation density model, a static recovery dislocation density model and a two-stage K-M dislocation density model as shown in formula (3):

in the formula: ρ is a unit of a gradient _r Dislocation density during static recovery; rho ₀ The dislocation density of the material after long-time static recovery; w is the static recovery coefficient; t is the holding time; ρ is the dislocation density in the thermal deformation process; m is Taylor factor; alpha is a constant, generally takes a value of 0.4-0.6, in this example 0.5; μ is the shear modulus; b is a Boehringer vector; sigma is stress; sigma _p Is the peak stress; sigma ₀ Initial stress at the onset of thermal compression; sigma _s Is a steady state stress; epsilon _p The strain corresponding to the peak value of the rheological stress; k is a radical of ₂ 、k′ ₂ Is the dynamic softening coefficient. Z is Zener-Hollomon parameter.

Derivation of dynamic low CSL sigma 3 with grain size, dynamic recrystallization volume fraction and dislocation density as variables ⁿ The grain boundary density evolution model is as shown in formula (4):

in the formula:

is low CSL sigma 3 ⁿ Grain boundary density; d _av Is the average grain size; d _drx Is a dynamic recrystallization grain size; x _drx Is the dynamic recrystallization volume fraction; d _initial Grain size at the start of hot compression; e _s For energy storage; g is shear modulus; b is a Boehringer vector; ρ is the dislocation density in the thermal deformation process; k is the arithmetic mean of 1 and (1-v), v is the Poisson's ratio.

And testing the grain growth behaviors under different initial grain sizes, temperatures and time and constructing a grain growth model as shown in formula (5):

in the formula: d is the grain size after growth; m is ₁ And alpha ₄ Are all coefficients; t is the holding time; r is an Avogastron constant;

t is the temperature; d _drx Is a dynamically recrystallized grain size.

S3, introducing physical quantity of pre-stored energy based on the influence of the pre-stored energy of cold deformation on the dynamic recrystallization model and the hot compression dislocation density model, and establishing a dynamic recrystallization model containing the pre-stored energy and a response model of the pre-stored energy on the dislocation density under the condition of cold-hot deformation;

for the sake of illustration, ni80A Ni-based superalloy valves are also used as examples. Considering the influence of cold deformation pre-stored energy on a dynamic recrystallization model and a hot compression dislocation density model, introducing physical quantity of the pre-stored energy, and establishing a dynamic recrystallization model containing the pre-stored energy and a response model of the pre-stored energy on the dislocation density under the cold-hot deformation condition as shown in the formulas (6) and (7) respectively;

in the formula: f. of ₁ (ε _pres )、f ₂ (ε _pres )、f ₃ (ε _pres )、f ₄ (ε _pres )、f ₅ (ε _pres )、f ₆ (ε _pres ) And f ₇ (ε _pres ) Is a correction factor; epsilon _pres Is cold pressing pre-strain.

S4, constructing a machining simulation system based on the models and the relational expressions in the S1-S3, and performing simulation machining according to machining parameters; the processing simulation system comprises a cold rolling finite element analysis model and a dynamic coupling electric upsetting finite element analysis model; construction of a processing simulation SystemThe process of the system comprises the following steps: firstly, establishing a cold rolling finite element model for calculating dislocation density and pre-stored energy in the cold rolling process according to cold rolling deformation; then, a field quantity inheriting subprogram is constructed for inheriting the pre-stored energy, the dislocation density and the equivalent plastic strain field quantity after cold rolling on the electric upsetting rod blank; then, constructing an electric upsetting finite element model for carrying out electric upsetting simulation according to electric upsetting technological parameters to obtain electric upsetting process quantity, wherein the electric upsetting process quantity comprises temperature, strain rate and stress data during electric upsetting; then, a dynamic recrystallization model, a grain growth model and a low CSL sigma 3 model containing pre-stored energy are used ⁿ And embedding the crystal boundary density evolution model, the dislocation density model and a response model of pre-stored energy to dislocation density into the electric upsetting finite element model to obtain a dynamic coupling electric upsetting finite element analysis model.

Analyzing the experiment results of S2-S3 and the key parameters to obtain a key parameter relation graph; the critical parameter relationship graph is used for displaying the dynamic recrystallization volume fraction, the energy storage, the grain size and the low CSL sigma 3 ⁿ The change rule of the grain boundary density along with the thermal deformation temperature and the strain rate. Specifically, the key parameter relationship diagram includes: graph of grain size and energy storage at different heat distortion temperatures and strain rates, dynamic recrystallization volume fraction, and low CSL sigma 3 ⁿ Relationship diagram of grain boundary density, energy storage and low CSL sigma 3 ⁿ Plot of grain boundary density, grain size and low CSL ∑ 3 ⁿ Graph of grain boundary density. Examples of these key parameters are shown in FIG. 7; in fig. 7, graph (a) shows a relationship between the grain size and the stored energy; graph (b) shows the recrystallized product fraction and the low CSL Σ 3 ⁿ A graph of grain boundary density; graph (c) represents energy storage versus low CSL Σ 3 ⁿ A graph of grain boundary density; graph (d) shows grain size and low CSL Σ 3 ⁿ Graph of grain boundary density.

And S5, designing machining parameters in the machining simulation model, and performing simulation machining.

Specifically, during the simulation processing, firstly, a cold rolling process is simulated through a cold rolling finite element model, the dislocation density and the pre-stored energy during the cold rolling are calculated according to the cold rolling deformation quantity, and an electric upsetting rod blank is endowed with the dislocation density and the pre-stored energy; and then simulating the electric upsetting deformation process according to the dynamic coupling electric upsetting finite element analysis model.

The process of simulating the electric upsetting deformation according to the dynamic coupling electric upsetting finite element analysis model comprises the following steps of: performing electric upsetting simulation according to electric upsetting process parameters through an electric upsetting finite element model to obtain electric upsetting process quantity; calculating a dislocation density model, a grain growth model and a dynamic recrystallization model containing pre-stored energy according to the electric upsetting process quantity to obtain key indexes, wherein the key indexes comprise dislocation density, stored energy, recrystallization volume fraction and grain size; and then calculating a low CSL sigma 3n crystal boundary density model according to the key indexes to obtain the low CSL sigma 3 ⁿ Grain boundary density distribution.

When the method is applied to specific applications, the mixed grain boundary unified model can be subjected to subprogram development based on a Visual Studio2015 program development tool and a Fortran language compiler. And establishing a cold rolling-ultra-long distance electric upsetting full-process dynamic coupling finite element model by utilizing an MSC.Marc software multi-physical field coupling solving scheme, wherein the cold rolling finite element model comprises a cold rolling finite element model and an electric-heat-force-energy-dislocation multi-field, deformation-crystal grain multi-scale dynamic coupling electric upsetting finite element analysis model. The material is Ni80A nickel-based superalloy, the diameter of an original rod blank is 74mm, and the cold rolling amount is 6mm; the diameter of the electric upsetting blank is 67mm as an example. Firstly, establishing a rod blank cold rolling finite element model, and calculating dislocation density and pre-stored energy in the cold rolling process according to cold deformation parameters; a field quantity inheritance subprogram is developed to inherit the field quantities of pre-stored energy, dislocation density, equivalent plastic strain and the like after cold rolling on the electric upsetting rod blank; then, a dynamic recrystallization model, a grain growth model and a low CSL sigma 3 containing the pre-stored energy physical quantity are used ⁿ The subprogram after programming of series models such as a crystal boundary density evolution model, a response model of pre-stored energy and dislocation density under a cold-heat deformation condition and the like is embedded into an electric upsetting finite element model, an electric-heat-force-energy-dislocation multi-field and deformation-crystal grain multi-scale dynamic coupling electric upsetting finite element analysis model which accords with the reality and considers the calculation precision and efficiency is established, the deformation length of an electric upsetting blank is 1200mm, the size of an end face fillet is R14mm, the initial force of electric upsetting is 480KN, the initial value of current is 14KN, and the temperature in the electric upsetting process is controlled within the range of 950-1150 ℃.

Simulating the rod blank cold rolling process based on the established cold rolling finite element model,the cold rolling process can be one-time or multi-time cold rolling deformation. Fig. 8 and 9 are simulation examples of dislocation density distribution of the rod blank after cold rolling, wherein fig. 8 is a simulation example of dislocation density distribution of the rod blank after three passes and the total deformation amount of the cold rolling is 6mm, and fig. 9 is a simulation example of dislocation density distribution of the electric upsetting rod blank after field quantity succession of the rod blank after cold rolling. And then, carrying out electric upsetting finite element simulation on the cold-rolled rod blank based on the established electric-heat-force-energy-dislocation multi-field and deformation-crystal grain multi-scale dynamic coupling electric upsetting finite element analysis model. Calculating dislocation density, energy storage, recrystallization volume fraction, grain size and low CSL sigma 3 under different electric upsetting forming temperature, strain and strain rate parameters through subprograms ⁿ Grain boundary density. Table 1 shown in FIG. 10 is the temperature, grain size and low CSL Σ 3 of the cold rolled bar stock during electric upsetting ⁿ And the distribution of the grain boundary density is shown.

S6, judging whether the simulation processing result meets the preset requirement, if not, turning to S7, and if so, turning to S8; wherein the simulated processing results include grain size and low CSL Σ 3 ⁿ Grain boundary density; the preset requirements include low CSL Σ 3 in the simulation results ⁿ The grain boundary density is larger than the preset density, and the grain size is smaller than the preset size.

S7, analyzing a key parameter adjusting strategy according to the key parameter relation graph, and analyzing a suggested adjusting direction of the processing parameter based on the key parameter adjusting strategy; after the machining parameters are adjusted according to the suggested adjustment direction, the adjusted machining parameters are subjected to simulation machining through a machining simulation system, and the process goes to S6; the key parameter adjusting strategy comprises a cold rolling strain amount, an electric heading process temperature, a strain rate and/or an adjusting direction of the strain amount.

And S8, taking the machining parameters as the machining parameters which are recommended to be used.

Thus, the grain size and low CSL ∑ 3 after electric heading forming ⁿ Low CSL ∑ 3 with grain boundary density not satisfying grain refinement and high ⁿ Grain boundary density requirement, the grain size and low CSL sigma 3 in the system are predicted according to the mixed grain boundary ⁿ Grain boundary density with temperature and strain rateThe change rule of rate and strain is regulated, high-order variation parameters such as upsetting force, current, anvil retreating speed and the like are regulated, and then electric upsetting finite element simulation is carried out, so that the parameters of temperature and strain rate in the electric upsetting process are subjected to grain refinement and high low CSL sigma 3 ⁿ The grain boundary density parameter interval. Meanwhile, under the condition that the cold rolling deformation is not fixed, the cold rolling deformation can be regulated and controlled or the cold rolling deformation and the electric upsetting high-order variation parameter can be comprehensively coordinated to obtain grain refinement and high low CSL sigma 3 ⁿ Grain boundary density.

In order to reduce the number of machining experiments and the experiment input cost, the embodiment provides the method for optimizing the machining parameters. By constructing a processing simulation system, the method realizes the realization of the grain size and the low CSL sigma 3 under different cold-heat deformation parameters ⁿ And predicting the grain boundary density, and establishing a key parameter relation graph in a communication manner, so that the machining parameters can be accurately and quickly optimized to obtain machining parameters which are recommended to be used. The machining parameters which are suggested to be used are directly used for machining subsequently, so that the cost can be reduced, the time can be saved, and the efficiency can be improved.

The processing simulation model in the method realizes the full-flow dynamic coupling of cold rolling and electric upsetting and the grain size, energy storage and low CSL sigma 3 in the ultra-long-range electric upsetting process ⁿ And the real-time monitoring and the distribution visualization of key indexes such as grain boundary density and the like. By combining the key parameter relation diagram, the grain refinement and the high low CSL sigma 3 can be obtained by optimizing the processing parameters (namely the cold rolling deformation and the electric upsetting process parameters) ⁿ Grain boundary density. In addition, the critical parameter relationship diagram shows grain size and low CSL Σ 3 ⁿ The change rule of the grain boundary density along with the temperature and the strain rate; when the processing simulation result does not meet the preset requirement (i.e. low CSL sigma 3) ⁿ Grain boundary density is less than or equal to a preset density, or grain size is greater than or equal to a preset size), a key parameter adjustment strategy, namely, adjustment directions of cold rolling strain, electric heading process temperature, strain rate and/or strain amount can be obtained according to the key parameter relation graph. The change of the key parameters is directly related to the change of the processing parameters (cold rolling deformation and electric upsetting process parameters), so that the adjustment of the processing parameters can be analyzed according to a key parameter adjustment strategyAnd (4) direction. By the mode, the machining parameters can be gradually optimized, and the machining parameters with the simulated machining results meeting the requirements are finally obtained.

The application example is as follows:

in order to more clearly illustrate the effect of the manufacturing method of the marine diesel valve for regulating and controlling the mixed grain boundary of the marine diesel valve, the effect of the manufacturing method of the marine diesel valve for regulating and controlling the mixed grain boundary of the marine diesel valve is further illustrated by the application example.

1. The effect of the Ni80A nickel-based superalloy small sample after cold deformation pre-energy storage regulation and control is as follows:

FIG. 11 is a graph of Ni80A nickel-base superalloy specimens pre-conditioned at cold reduction levels of 0%, 15%, 20%, 25%, and 30% and then strained at 1273K at a strain rate of 0.1s ^-1 And the results of the structure characterization after isothermal hot compression under the condition of 60% of compression (0.916% of true strain). In fig. 11, the graphs (a) and (a ') are a dynamic recrystallization texture graph and a grain boundary graph at a cold press reduction rate of 0%, the graphs (b) and (b ') are a dynamic recrystallization texture graph and a grain boundary graph at a cold press reduction rate of 15%, the graphs (c) and (c ') are a dynamic recrystallization texture graph and a grain boundary graph at a cold press reduction rate of 20%, the graphs (d) and (d ') are a dynamic recrystallization texture graph and a grain boundary graph at a cold press reduction rate of 25%, and the graphs (e) and (e ') are a dynamic recrystallization texture graph and a grain boundary graph at a cold press reduction rate of 30%, respectively. From fig. 11, it can be found that after cold pressing pre-deformation, the dynamic recrystallization degree is significantly increased from 8.3% of the non-cold pressing pre-treatment to more than 80%; meanwhile, the crystal grains are fully refined and are fully cracked by the low sigma CSL crystal boundary to form an ideal mixed crystal boundary network. The density of the low sigma CSL crystal boundary before precooling deformation regulation is 0.0252 mu m < -1 >, and the density of the low sigma CSL crystal boundary after precooling deformation regulation is as high as 0.2429 mu m < -1 >. Further illustrates that the high dislocation density subgrain boundary formed in the cold deformation process can stimulate dynamic recrystallization and low sigma CSL grain boundary nucleation in the thermal deformation process, thereby obtaining a uniform and fine-grained and high-cracking mixed grain boundary network.

2. Regulation and control effect of mixed crystal boundary in cold rolling-ultra-long range electric upsetting full-process dynamic coupling forming process

Aiming at the same straight blank of the electric upsetting rod, the method for further explaining the effect of the novel method for regulating and controlling the mixed grain boundary of the air valve of the marine diesel engineThe diameter is 67mm, the rod blank is not subjected to cold rolling pretreatment, and the same electric upsetting parameters are directly adopted for electric upsetting finite element simulation. Table 2 shown in FIG. 12 is the temperature, grain size and low CSL Σ 3 of the cold rolled bar stock during electric upsetting ⁿ Grain boundary density distribution. Fig. 13 and 14 are the variation of the maximum temperature and the maximum grain size of the cold rolled and non-cold rolled bar blanks during the electric upsetting formation, respectively. In combination with the results of comparison between table 1 shown in fig. 10, table 2 shown in fig. 12, and fig. 13 and fig. 14, it can be found that, in the electric upsetting forming process, because the electric upsetting forming parameters are consistent, the temperature of the cold-rolled and non-cold-rolled rod blanks does not change significantly in the electric upsetting process; grain size and low CSL ∑ 3 during electrical upsetting ⁿ The grain boundary density is obviously changed, the crystal grains of the rod blank subjected to cold rolling pretreatment are obviously refined during electric upsetting forming, and the low CSL sigma 3 of the outer contour of the electric upsetting garlic head ⁿ The grain boundary density is obviously improved, and the garlic head center is low in CSL sigma 3 ⁿ The region of lower grain boundary density values is significantly reduced. Further explaining the new method for regulating and controlling the mixed grain boundary, the grain size in the electric upsetting process can be obviously refined, and the low CSL sigma 3 is added ⁿ The grain boundary density and the regulation effect are obvious.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.

Claims

1. The manufacturing method of the marine diesel engine air valve for regulating and controlling the mixed grain boundary is characterized in that the mixed grain boundary of the marine diesel engine air valve is regulated and controlled in advance through simulation, simulation design and optimization are carried out on machining parameters for manufacturing the marine diesel engine air valve, and machining parameters which are recommended to use are determined, wherein the machining parameters comprise cold rolling deformation and electric upsetting process parameters; then, performing cold rolling pretreatment and electric upsetting processing on an initial rod blank for processing and manufacturing the air valve of the marine diesel engine according to the processing parameters used in the proposal to finish the manufacturing of the air valve of the marine diesel engine;

the electric upsetting process parameters comprise initial process parameters and high-order variation parameters; the initial technological parameters comprise the chamfer size of the rod blank, the clamping length, the preheating time and the preheating current, and the high-order variation parameters comprise upsetting force, current and anvil retreating speed;

the simulation design and optimization of the processing parameters comprises the following steps:

s2, taking a standard thermophysical simulation compression experiment for the cold-pressed sample, developing the hot compression experiments at different temperatures and stress rates, and observing and statistically analyzing crystal grains and crystal boundaries of the sample treated under different deformation conditions; establishing a dynamic recrystallization model under the premise of cold deformation pre-stored energy according to a JMAK equation configuration; deducing and constructing a dislocation density evolution model of the cold pressing-hot pressing whole process by adopting a K-M dislocation density model, a static recovery dislocation density model and a two-stage K-M dislocation density model; derivation of Low CSL Sigma 3 with grain size, dynamic recrystallization volume fraction and dislocation density as variables ⁿ A grain boundary density evolution model; testing the grain growth behaviors under different initial grain sizes, temperatures and time and constructing a grain growth model;

s4, constructing a machining simulation system based on the models and the relational expressions in the S1-S3, and performing simulation machining according to machining parameters; analyzing the experiment results of S2-S3 and the key parameters to obtain a key parameter relation graph; the critical parameter relationship graph is used for displaying the dynamic recrystallization volume fraction, the energy storage, the grain size and the low CSL sigma 3 ⁿ The change rule of the grain boundary density along with the thermal deformation temperature and the strain rate;

s7, analyzing a key parameter adjusting strategy according to the key parameter relation graph, wherein the key parameter adjusting strategy comprises adjusting directions of cold rolling strain, electric upsetting process temperature, strain rate and/or strain; analyzing a suggested adjusting direction of the processing parameter based on a key parameter adjusting strategy; after the machining parameters are adjusted according to the suggested adjustment direction, performing simulation machining on the adjusted machining parameters through a machining simulation system, and turning to S6;

2. The method for manufacturing the marine diesel engine air valve for regulating and controlling the mixed grain boundary as claimed in claim 1, wherein in S4, the processing simulation system comprises a cold rolling finite element analysis model and a dynamic coupling electric upsetting finite element analysis model;

the process of constructing the processing simulation system comprises the following steps: firstly, establishing a cold rolling finite element model for calculating dislocation density and pre-stored energy in the cold rolling process according to cold rolling deformation; then, a field quantity inheriting subprogram is constructed for inheriting the pre-stored energy, the dislocation density and the equivalent plastic strain field quantity after cold rolling on the electric upsetting rod blank; then, constructing an electric upsetting finite element model for carrying out electric upsetting simulation according to electric upsetting technological parameters to obtain electric upsetting process quantity, wherein the electric upsetting process quantity comprises temperature, strain rate and stress data during electric upsetting; then, a dynamic recrystallization model containing pre-stored energy, a grain growth model and low CSL sigma 3 are used ⁿ And embedding the crystal boundary density evolution model, the dislocation density model and a response model of the pre-stored energy to the dislocation density into the electric upsetting finite element model to obtain a dynamic coupling electric upsetting finite element analysis model.

3. The method for manufacturing the marine diesel engine air valve for regulating and controlling the mixed grain boundary according to claim 1, wherein in the step S5, during the simulation processing, firstly, a cold rolling process is simulated through a cold rolling finite element model, the dislocation density and the pre-stored energy during the cold rolling are calculated according to the deformation amount of the cold rolling, and an electric upsetting rod blank is given; then simulating an electric upsetting deformation process according to the dynamic coupling electric upsetting finite element analysis model;

4. The method for manufacturing a marine diesel valve for regulating and controlling mixed grain boundaries according to claim 1, wherein in S4, the key parameter relationship diagram comprises: graph of grain size and energy storage at different heat distortion temperatures and strain rates, dynamic recrystallization volume fraction, and low CSL sigma 3 ⁿ Relationship diagram of grain boundary density, energy storage and low CSL sigma 3 ⁿ Plot of grain boundary density, grain size and low CSL ∑ 3 ⁿ Graph of grain boundary density.

5. The method for manufacturing a marine diesel valve with mixed grain boundaries as claimed in claim 1, wherein in S6, the simulation result comprises grain size and low CSL Σ 3 ⁿ Grain boundary density; the preset requirements include low CSL Σ 3 in the simulation results ⁿ The grain boundary density is larger than the preset density, and the grain size is smaller than the preset size.

6. The method for manufacturing a marine diesel valve with mixed grain boundaries regulated according to claim 1, wherein the cold rolling pretreatment and the electric upsetting processing are performed on the initial rod blank for manufacturing the marine diesel valve according to the suggested processing parameters, and the specific steps for manufacturing the marine diesel valve comprise:

and (3) machining: machining the cold-rolled rod blank to make the surface of the rod blank smooth;

and (3) aging treatment: and carrying out aging heat treatment on the air valve to adjust and homogenize the air valve tissue.

7. The method for manufacturing the marine diesel valve for regulating and controlling the mixed grain boundary according to claim 6, wherein in the aging treatment step, the temperature of the aging heat treatment is 690-710 ℃, the time of the aging heat treatment is 16-18 h, and the air cooling is carried out after the aging heat treatment.

8. The method for manufacturing the marine diesel valve for regulating and controlling the mixed grain boundary according to claim 6, further comprising the following steps between the electric upsetting step and the heating and heat preservation step:

a heat supplementing treatment step: performing heat supplementing on the head of the blank formed by the electric upsetting material; wherein the heat supplementing temperature is 1000-1050 ℃, and the heat supplementing time is 15-30min.