Special steel wire rod rolling whole-line temperature field and phase change coupling calculation method

Abstract

The invention relates to a special steel wire rod rolling whole-line temperature field and phase change coupling calculation method, and belongs to the technical field of metallurgy. The method comprises the following steps: inputting process parameters of a production line; secondly, the rolling speed and the running time of each pass are calculated, and time step length and cross section grid division are carried out; utilizing a temperature field finite difference equation, a phase change model and a heat exchange model to couple and solve the temperature evolution and phase change process of a rolling section and a cooling section to obtain the temperature and phase composition of any position of the whole line; calculating the grain size and recrystallization fraction of austenite in each stage of the rolling section by using a physical metallurgy model; and calculating the final mechanical property by using the mechanical property model. According to the method, whole-line temperature field and phase change prediction including the rolling stage and the cooling stage can be achieved, the temperature and phase composition of different positions of the section of a rolled piece are calculated, and the method is suitable for whole-line temperature field and phase change coupling calculation of multiple steel wires and temperature field and phase change coupling calculation of air cooling line lap joints and non-lap joints.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and relates to a method for calculating the temperature field and phase change coupling of a special steel wire rolling line. Background Art

[0002] At present, steel enterprises are actively promoting the deep integration of new generation information and communication technologies such as digitalization and intelligence with the entire process of steel manufacturing, and the steel industry is gradually transforming towards high-end, green and intelligent directions. In the field of steel material rolling, with the progress and development of modern science and technology, the equipment level of steel material rolling process is getting higher and higher, the degree of automation is getting higher and higher, and emerging technologies such as organization performance prediction are also born. Organization performance prediction technology is based on temperature field heat exchange model, physical metallurgy model, phase change model and mechanical property model to predict the temperature, organization and final performance of rolled parts in the rolling production process, which is of great significance to the development and optimization of new rolling processes and the regulation of final organization and performance.

[0003] During the rolling process, the temperature field and phase change process of the rolled piece affect each other. Changes in temperature will affect the phase change behavior of the rolled piece, and the heat released or absorbed during the phase change will in turn affect the temperature field. Therefore, coupling calculations of the temperature field and phase change in the rolling stage can more accurately describe the physical phenomena in the rolling process and provide strong support for process optimization and product quality control. The chemical composition of plain carbon steel is relatively simple. The current microstructure and performance prediction technology believes that the phase change process will not occur in the high-temperature rolling line stage, but only in the subsequent air cooling line or cooling bed stage. The phase change process begins, so the current microstructure and performance prediction technology only performs coupled calculations of the temperature field and phase change in the air cooling line or cooling bed stage, and only uses a separate temperature field calculation method in the previous rolling section.

[0004] Special steel has become the main choice for machinery, automobiles, chemicals, home appliances, ships, transportation, railways and emerging industries due to its high strength, high toughness, wear resistance, corrosion resistance and other excellent properties. These industries have higher and higher requirements for the quality and performance of materials, which has promoted the growth of demand for special steel. Special steel is a type of steel with specific properties made by adding specific alloy elements. Its chemical composition is richer. These added alloy elements will change the phase change type, phase change temperature and phase change products of special steel. This means that the current microstructure performance prediction system that ignores the phase change in the rolling stage is not suitable for microstructure performance prediction on special steel production lines. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for coupling calculation of temperature field and phase change of the entire special steel wire rolling line, which can realize the coupling calculation of temperature field and phase change of the entire line from heating furnace to cooling process, predict the temperature and phase composition at any position of the entire line, and then more accurately predict the final mechanical properties.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for calculating the temperature field and phase change coupling of a special steel wire rolling line, the method comprising the following steps:

[0008] 1) Upload the production line process parameters required for calculation: including heating furnace parameters (furnace entry temperature, heating temperature, heating time, soaking temperature, soaking time), rolling mill parameters (hole shape, rolling elongation, roller ring diameter, rolling mill position, roller temperature, number of rolling mills), water tank parameters (length, water pressure, water volume, position, ring gap width, nozzle length, inlet and outlet diameter, turbulence tube length, nozzle angle, number of nozzles, number of water tanks), fan parameters (air volume, rated power, opening, insulation cover status, fan type, air cooling line length, number of fans), incoming material parameters (brand, chemical composition, size,), production line parameters (rolling specifications, average speed before rolling, final rolling speed, head stripping pass, ambient temperature, turbid ring water temperature, billet type, product type).

[0009] 2) Calculate the rolling speed and running time of each pass, and perform time step and cross-sectional mesh division.

[0010] 3) The temperature evolution and phase change history of the rolling section and the cooling section are solved by coupling the temperature field finite difference equation, the phase change model, and the heat exchange model to obtain the temperature and phase composition at any position of the entire line. The phase change model includes a phase incubation period model and a phase transition variable model. The heat exchange model includes an air cooling heat exchange model, a roll heat exchange model, a water cooling heat exchange model, an air cooling heat exchange model, and a cooling bed heat exchange model. The phase transition variable model is obtained through the TTT curve. The coupling solution relationship steps are:

[0011] (1) Through the difference equation Solve for the temperature value at the next moment Δt

[0012] (2) Then, the phase transition variable at time t0+Δt is obtained using the phase transition variable model X=f(T,t) The phase shift variable ΔX at time Δt;

[0013] (3) Then, the phase change latent heat generated at the time Δt is calculated using the phase change latent heat model q = f(T, ΔX, t);

[0014] (4) Through the formula Find the final temperature.

[0015] 4) Calculate the grain size and recrystallization fraction of austenite at each stage of the rolling section using a physical metallurgical model. The physical metallurgical model includes an austenite grain growth model, a critical strain model, a dynamic recrystallization fraction model, a dynamic recrystallization size model, a static recrystallization fraction model, a static recrystallization size model, and a metadynamic recrystallization model.

[0016] 5) Calculate the final mechanical properties using a mechanical property model, wherein the mechanical property model includes a yield strength model, a tensile strength model, an elongation model, and a cross-sectional shrinkage model.

[0017] The beneficial effects of the present invention are:

[0018] 1) The present invention can realize the prediction of the temperature field and phase change of the entire line including the rolling stage and the cooling stage, and can describe the phase transformation process caused by the forced water cooling of the water tank in the rolling stage, which is more in line with the actual production process.

[0019] 2) The present invention can calculate the temperature and phase composition at different positions of the cross section of the rolled piece, determine the temperature and structure differences between the core and surface of the rolled piece, and help optimize the rolling process.

[0020] 3) The present invention is applicable to the full-line temperature field and phase change coupling calculation of various types of steel wires, including but not limited to common special steels such as cold heading steel SCM435 and spring steel 55SiCr.

[0021] 4) The present invention is applicable to the coupled calculation of temperature field and phase change at overlap points and non-overlap points of air-cooled wires, and is helpful to analyze the differences in microstructure and mechanical properties at overlap points and non-overlap points.

[0022] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 It is the principle diagram of the process of the present invention;

[0025] Figure 2 is the ferrite phase precipitation curve in the rolling stage of Example 1;

[0026] Figure 3 This is the ferrite phase precipitation curve in the cooling stage of Example 1;

[0027] Figure 4 This is the pearlite phase precipitation curve in the cooling stage of Example 1;

[0028] Figure 5 This is the temperature field curve of the rolling stage of Example 1;

[0029] Figure 6 This is the temperature field curve of the cooling section of Example 1;

[0030] Figure 7 is the pearlite phase transition amount at the overlap point of the cooling section in Example 2;

[0031] Figure 8 The pearlite phase transition amount at the non-overlapping point in the cooling section of Example 2

[0032] Fig. 9 This is a temperature field change diagram of the non-overlapping points and overlapping points in the cooling section of Example 2. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Figure 1This is the schematic diagram of the process of the present invention. At present, the phase change calculation only stays in the cooling stage of the rolling production line, which makes it difficult to predict the performance of special steels with more complex phase change processes. The present invention extends the phase change calculation to the entire rolling line to achieve coupled calculation of the temperature field and phase change of the entire line. The temperature field is calculated using finite difference equations, and the phase transition variable model is established through the TTT curve. It is possible to predict the temperature field and phase change at any position of the entire line and the entire cross-section of the rolled piece, and ultimately achieve the prediction of the mechanical properties of special steels. The present invention can be used to guide the formulation of hot rolling and cooling processes for special steel wire rolling production lines, and improve the product qualification rate; it can be connected to actual industrial production to achieve online temperature field phase change and mechanical property prediction of rolled pieces, and reduce the subsequent testing costs of rolled pieces.

[0037] See also Figure 2 to Figure 6 , Example 1: Taking the SCM435 cold heading steel wire rod with a production specification of 14 in a domestic steel plant as an example, the temperature field, phase composition and final mechanical properties of the whole line are predicted. The production line has 20 rolling mill units, and there are four water tanks after the intermediate rolling mill unit, pre-finishing rolling mill unit and finishing rolling mill unit. There are 17 fans on the air cooling line. The cold heading steel SCM435 needs to be cooled slowly during the cooling process, and the insulation cover is covered for slow cooling. The specific steps are as follows:

[0038] 1) Upload the production line process parameters required for calculation: including heating furnace parameters, rolling mill unit parameters, water tank parameters, fan parameters, incoming material parameters, and production line parameters.

[0039] 2) Calculate the rolling speed and running time of each pass.

[0040] 3) The temperature evolution and phase change history of the rolling section and cooling section are solved by coupling the temperature field finite difference equation, phase change model, and heat transfer model to obtain the temperature and phase composition at any position along the entire line.

[0041] 4) Using the physical metallurgical model, calculate the grain size and recrystallization fraction of austenite at each stage of the rolling section.

[0042] 5) Use the mechanical properties model to calculate the final mechanical properties.

[0043] The calculated predicted values ​​are compared with the actual values ​​produced, and the comparison table is shown in Table 1.

[0044] Table 1

[0045] tensile strength Yield Strength Elongation, in % Sectional shrinkage, in % Actual value 808 494 26.6 54.8 Predicted value 794 472 27.5 56.8 Relative error 1.7％ 4.5％ 6.8％ 4.9％

[0046] See also Figure 7 to Figure 9Example 2: Taking a 55SiCr spring steel wire rod with a specification of 17 produced by a domestic steel plant as an example, the temperature field, phase composition and final mechanical properties of the whole line are predicted. The production line has 18 rolling mill units, and the intermediate rolling mill unit, pre-finishing rolling mill unit and finishing rolling mill unit are equipped with four water tanks. The air cooling line is equipped with 17 fans. The specific steps are as follows:

[0047] 1) Upload the production line process parameters required for calculation: including heating furnace parameters, rolling mill unit parameters, water tank parameters, fan parameters, incoming material parameters, and production line parameters.

[0048] 2) Calculate the rolling speed and running time of each pass.

[0049] 3) The temperature evolution and phase change history of the rolling section and cooling section are solved by coupling the temperature field finite difference equation, phase change model, and heat transfer model to obtain the temperature and phase composition at any position along the entire line.

[0050] 4) Using the physical metallurgical model, calculate the grain size and recrystallization fraction of austenite at each stage of the rolling section.

[0051] 5) Use the mechanical properties model to calculate the final mechanical properties.

[0052] The calculated predicted values ​​are compared with the actual values ​​produced, and the comparison table is shown in Table 2.

[0053] Table 2

[0054] tensile strength Yield Strength Elongation, in % Sectional shrinkage, in % Actual value 987 494 27 48 Predicted value 1025 518 25.5 45.7 Relative error 3.9％ 4.9％ 5.6％ 4.8％

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for calculating the temperature field and phase change coupling of a special steel wire rolling line, characterized in that: The following steps are involved: Upload the production line process parameters required for calculation, including heating furnace parameters, rolling mill unit parameters, water tank parameters, fan parameters, incoming material parameters and production line parameters; Calculate the rolling speed and running time of each pass, and perform time step and cross-section meshing; The temperature evolution and phase change process of the rolling section and cooling section are solved by coupling the temperature field finite difference equation, phase change model and heat transfer model, and the temperature and phase composition at any position of the whole line are obtained; Using the physical metallurgical model, the grain size and recrystallization fraction of austenite at each stage of the rolling section are calculated; The final mechanical properties are calculated using the mechanical properties model.

2. The method for calculating the temperature field and phase change coupling of the entire special steel wire rolling line according to claim 1 is characterized in that: The phase change model includes a phase incubation period model and a phase transition variable model, the heat exchange model includes an air cooling heat exchange model, a roller heat exchange model, a water cooling heat exchange model, an air cooling heat exchange model and a cooling bed heat exchange model, and the phase transition variable model is obtained through a TTT curve.

3. The method for calculating the temperature field and phase change coupling of the entire special steel wire rolling line according to claim 1 is characterized in that: The physical metallurgical model includes an austenite grain growth model, a critical strain model, a dynamic recrystallization fraction model, a dynamic recrystallization size model, a static recrystallization fraction model, a static recrystallization size model and a meta-dynamic recrystallization model.

4. The method for calculating the temperature field and phase change coupling of the entire special steel wire rolling line according to claim 1 is characterized in that: The mechanical property model includes a yield strength model, a tensile strength model, an elongation model and a section shrinkage model.

5. The method for calculating the temperature field and phase change coupling of the entire special steel wire rolling line according to claim 1 is characterized in that: The special steel wire is a special steel grade with a TTT curve, including cold heading steel SCM435 and spring steel 55SiCr.

6. The method for calculating the temperature field and phase change coupling of the entire special steel wire rolling line according to claim 1 is characterized in that: The method is suitable for predicting the temperature field and phase variable of overlapping points and non-overlapping points on the air-cooling line.

Images