CN115719623A - Method for realizing visualization of recrystallization texture evolution in hot rolling process - Google Patents

Abstract

The invention discloses a method for realizing visualization of recrystallization texture evolution in a hot rolling process, and belongs to the field of steel rolling. The method is based on a recrystallization fraction and grain size prediction model in the rolling process, rolling production process parameters are read from a production field server, a time-varying curve of softening fractions and grain sizes of all passes in the rolling process is calculated, a Vonoroi diagram is used for predicting the microstructure evolution process in the rolling process in real time, and digital analysis of the microstructure evolution in the rolling process is realized. The technology can guide the formulation of hot rolling production process parameters, and optimizes the final grain size and the grain compression ratio in the rolling process by formulating reasonable process parameters, thereby providing a basis for the control of the microstructure of the hot rolled steel.

Description

Method for realizing visualization of recrystallization texture evolution in hot rolling process

Technical Field

The invention relates to the technical field of steel rolling, in particular to a method for realizing visualization of recrystallization texture evolution in a hot rolling process.

Background

The microstructure morphology evolution of hot rolled steel austenite during multi-pass hot rolling is of great importance for its industrial production and has therefore received much attention in the last decades. The structure evolution is not only one of the main modes of grain refinement, but also has an important influence on the austenite transformation during accelerated cooling, and is therefore one of the most important factors influencing the structure and mechanical properties of the hot-rolled steel. In order to predict the mechanical properties of hot rolled products, to design the most efficient process and develop new products, it is necessary to develop mathematical models and visualization methods with good prediction capabilities and low computation time cost to accurately track the evolution of the microstructure during the process.

At present, researches on the structure evolution of the rolling process mainly focus on calculating the recrystallization fraction of each pass of austenite rolling and the grain size change, and the dynamic and static recrystallization fractions of each pass of rolling and the grain size change of the gap of each pass of rolling are calculated with time by changing parameters in a theoretical model. In 1979 selars first presented a theoretical method for calculating the Recrystallization fraction (c.m. selars, j.a. white man, regeneration and grain growth in hot rolling, metal Science (1979) 187-194), providing theoretical guidance for the industrial application of numerical analysis of the tissue evolution of the rolling process. Liu et al predicted the recrystallization behavior of hot rolling on the basis of the Serlars theoretical model (Y. Liu, J.Lin, modeling of micro structural evaluation in multipross hot rolling, journal of Material Processing Technology 143-144 (2003)

723-728). Chinese patent publication nos. CN201110249721.2 and CN02109026.2 provide a calculation method for predicting recrystallization fraction and grain size of C-Mn steel in a C-Mn-Nb steel rolling process, and systematically illustrate a prediction method for recrystallization behavior in a rolling process in industrial production. However, these methods have limitations in that the calculation results cannot be visualized, and imaging information of the tissue evolution in the recrystallization process cannot be shown more intuitively and clearly.

In view of the above, the invention provides a method for realizing visualization of recrystallization texture evolution in a hot rolling process, and provides a reference for texture control in the rolling process.

Disclosure of Invention

The invention aims to provide a method for realizing visualization of recrystallization texture evolution in a hot rolling process, which divides austenite grains into recrystallization substructure grains and deformation substructure grains and provides a calculation method for calculating the grain size, the grain shape and the occupied volume fraction of the two grains. And combining the calculation result, and quickly generating a corresponding microstructure by using a Vonoroi diagram to visualize the calculation result, thereby more intuitively and clearly showing the imaging information of the structure evolution in the recrystallization process.

In order to achieve the above object, the present invention provides a method for visualizing the evolution of a recrystallized structure in a hot rolling process, comprising the steps of:

s1, establishing a dynamic and static recrystallization fraction calculation model in an alloy rolling process;

s2, reading rolling process parameters, and calculating the strain and strain rate of each pass;

s3, calculating the dynamic recrystallization fraction in the rolling process and the static recrystallization fraction between two adjacent passes by using the rolling temperature, the strain and the strain rate;

s4, dividing the austenite grains into non-recrystallized deformed substructure grains and recrystallized substructure grains, and calculating the sizes and volume fractions of the deformed substructure grains and the recrystallized substructure grains;

and S5, generating a corresponding microstructure optimization by combining the Vonoroi diagram by using the size information and the volume fraction of the deformed substructure grains and the recrystallized substructure grains calculated in the step S4.

Preferably, the alloy in the step S1 is one of common C-Mn series steel, nb microalloyed steel and Ti microalloyed steel, and each alloy has chemical components of, by weight, 0.01% to 0.10% of C, 0.8% to 1.5% of Si, 0.15% to 2.5% of Mn, 0% to 0.015% of S, 0% to 0.019% of P, 0% to 0.08% of Nb, 0% to 0.10% of Ti, and the balance of Fe and impurities existing during smelting.

Preferably, the rolling process parameters in step S2 include rolling temperature, thickness of steel plate in each rolling pass, rolling speed, and diameter of roll of each rolling stand.

Preferably, the size of the deformed substructure grains calculated in step S4 is calculated based on the grain size before rolling and the reduction rate of rolling.

Preferably, the calculation of the size of the recrystallized substructure grains in step S4 calculates a model grain growth model and a grain size after static recrystallization according to the dynamic and static recrystallization fractions.

Preferably, the step S4 includes the steps of:

s4.1, the substructures are regarded as basic units for calculating the evolution process of the austenitic microstructure, so that the austenitic microstructure M is a set of substructures S of different shapes, M = { S = ₁ ，S ₂ 8230, all the austenite contained in each class of substructures has the same grain size and shape. The substructures can be divided into two categories, namely a recrystallized substructure RS where the grains are circular and a deformed substructure DS where the grains are oval, depending on whether or not the included grains are recrystallized. The grain size of the recrystallized substructure is characterized by the diameter d, and the grain size in the deformed substructure is characterized by the major axis length d of the ellipse _M And minor axis length d _m Constituent Unit (d) _M ，d _m ) Characterizing;

s4.2, new recrystallized grains randomly appear in all substructures, and all the new recrystallized grains have the same grain size according to the calculation formula of the grain size after dynamic recrystallization, the size of the dynamic recrystallization grains and the grain growth model, so that the recrystallized grains only have one substructure. The size of the new deformed substructure depends on the original substructure, and the size calculation formula is shown as formula 1;

in the formula (I), the compound is shown in the specification,

and

the length of the major axis and the length of the minor axis of the elliptical crystal grain before deformation; d is a radical of _M And d _m The length of the long axis and the length of the short axis of the deformed elliptic crystal grains; p is the deformation rate;

assuming that the microstructure of the i-th pass consists of a recrystallized substructure RS and m deformed substructures DS,

the fractional vector of each substructure is

The grain size vector is

For the (i + 1) th pass, if the static recrystallization is completely carried out, the microstructure after rolling only contains new recrystallized substructures with a composition M _i+1 ＝{RS ⁱ⁺¹ H, score of F _i+1 = 1, size D _i+1 ＝{d ⁱ⁺¹ }，d ⁱ⁺¹ Can be formed by ⁱ Calculating the grain size and the grain growth model after static recrystallization;

s4.3, if the fraction of the static recrystallization of the (i + 1) th pass is f ⁱ⁺¹ Since recrystallized grains randomly appear in all the substructures, each initial substructure is decomposed into a fraction f ⁱ⁺¹ Has a new recrystallized substructure and fraction of 1-f ⁱ⁺¹ Two parts of the new deformed substructure of (a). Due to the identity of the new recrystallized substructureAnd therefore, all new recrystallized substructures can be considered as one substructure, RS ⁱ⁺¹ Of size d ⁱ⁺¹ . Will RS ⁱ The new deformed substructure produced is noted

In a ratio of Rf ⁱ (1-f ⁱ⁺¹ ) Size of it

Can be calculated by equation 1.

The new deformed substructure produced is noted

In a ratio of

Size of it

Can be calculated by equation 1. The recrystallized microstructure contains m +2 substructures, which are recorded as

The fractional vector of each substructure is

The grain size vector is

Therefore, the method for realizing the visualization of the recrystallization texture evolution in the hot rolling process is adopted, the austenite grains are divided into the recrystallization substructure grains and the deformation substructure grains, and the calculation method for calculating the grain size, the grain shape and the occupied volume fraction of the two grains is provided. And combining the calculation result, and quickly generating a corresponding microstructure by using a Vonoroi diagram to visualize the calculation result, thereby more intuitively and clearly showing the imaging information of the structure evolution in the recrystallization process.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is a flow chart of a method for visualizing the evolution of a recrystallized structure in a hot rolling process according to the present invention;

FIG. 2 is a graph of the fraction of recrystallized grains as a function of time for a process condition selected for a method of visualizing the evolution of a recrystallized structure during hot rolling according to the present invention;

FIG. 3 is the morphology of the microstructure before finish rolling under the process conditions selected by the method for visualizing the evolution of the recrystallized structure in the hot rolling process according to the invention;

FIG. 4 is the morphology of the microstructure of pass 4 under process conditions selected by a method for visualizing the evolution of a recrystallized structure in a hot rolling process according to the invention;

FIG. 5 is the morphology of the microstructure of pass 5 under process conditions selected by a method for visualizing the evolution of a recrystallized structure in a hot rolling process according to the invention;

FIG. 6 is a diagram showing the morphology of the microstructure of pass 6 under process conditions selected by a method for visualizing the evolution of the recrystallized structure in the hot rolling process according to the present invention;

FIG. 7 is the morphology of the microstructure of pass 7 under the process conditions selected by the method for visualizing the recrystallization evolution of the hot rolling process.

Detailed Description

The technical solution of the present invention is further illustrated by the accompanying drawings and examples.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

The invention provides a method for realizing visualization of recrystallization texture evolution in a hot rolling process, which comprises the following steps:

s1, establishing a dynamic and static recrystallization fraction calculation model in an alloy rolling process, wherein the alloy is one of common C-Mn series steel, nb microalloyed steel and Ti microalloyed steel, and the chemical components of each alloy are 0.01-0.10 percent of C, 0.8-1.5 percent of Si, 0.15-2.5 percent of Mn, 0-0.015 percent of S, 0-0.019 percent of P, 0-0.08 percent of Nb, 0-0.10 percent of Ti and the balance of Fe and impurities existing in smelting according to weight percentage;

s2, reading rolling process parameters including rolling temperature, thickness of a steel plate rolled in each pass, rolling speed and diameter of a roller of each rolling rack from a production field server, and calculating strain and strain rate of each pass;

and S3, calculating the dynamic recrystallization fraction in the rolling process and the static recrystallization fraction between two adjacent passes by using the rolling temperature, the strain and the strain rate.

And S4, dividing the austenite grains into non-recrystallized deformed substructure grains and recrystallized substructure grains, and calculating the sizes and occupied volume fractions of the deformed substructure grains and the recrystallized substructure grains, wherein the sizes of the deformed substructure grains are calculated according to the sizes of the grains before rolling and the rolling reduction rate, and the sizes of the recrystallized substructure grains are calculated according to a dynamic and static recrystallization fraction calculation model, a grain growth model and the sizes of the grains after static recrystallization.

S4.1, the substructures are regarded as basic units for calculating the evolution process of the austenitic microstructure, so that the austenitic microstructure M is a collection of substructures S of different shapes, M = { S = { S = ₁ ，S ₂ 8230, each class of substructure contains austenite all having the same grain size and shape. The substructures can be divided into two categories, i.e. the grains are rounded again, depending on whether or not the included grains are recrystallizedThe crystalline substructure RS and the deformed substructure DS with the grains being oval. The grain size of the recrystallized substructure is characterized by the diameter d, and the grain size in the deformed substructure is characterized by the major axis length d of the ellipse _M And minor axis length d _m Constituent Unit (d) _M ，d _m ) And (5) characterizing.

S4.2, new recrystallized grains randomly appear in all substructures, and all the new recrystallized grains have the same grain size according to the calculation formula of the grain size after dynamic recrystallization, the size of the dynamic recrystallization grains and the grain growth model, so that the recrystallized grains only have one substructure. The size of the new deformed substructure depends on the original substructure, and the size calculation formula is shown in formula (1).

And

the length of the long axis and the length of the short axis of the elliptic crystal grain before deformation; d _M And d _m The length of the long axis and the length of the short axis of the deformed elliptic crystal grains; p is the deformation ratio.

Assuming that the microstructure of the i-th pass consists of a recrystallized substructure RS and m deformed substructures DS,

the fractional vector of each substructure is

The grain size vector is

For lane i +1Secondly, if the static recrystallization is completely carried out, the microstructure after rolling comprises only new recrystallized substructures, with a composition M _i+1 ＝{RS ⁱ⁺¹ H, score of F _i+1 = 1, size D _i+1 ＝{d ⁱ⁺¹ }，d ⁱ⁺¹ Can be formed by ⁱ And calculating the grain size and the grain growth model after static recrystallization.

S4.3, if the fraction of the static recrystallization of the (i + 1) th pass is f ⁱ⁺¹ Since recrystallized grains randomly appear in all the substructures, each initial substructure is decomposed into a fraction f ⁱ⁺¹ Has a new recrystallized substructure and fraction of 1-f ⁱ⁺¹ Two parts of the new deformed substructure. Since the newly recrystallized substructure has the same size and shape, all of the newly recrystallized substructures can be considered as one substructure, RS ⁱ⁺¹ Having a size d ⁱ⁺¹ . Will RS ⁱ The new deformed substructure produced is noted

In the ratio of Rf ⁱ (1-f ⁱ⁺¹ ) Size of it

Can be calculated by equation 1.

The new deformed substructure produced is noted

In a ratio of

Size of it

Can be calculated by equation 1. The microstructure after recrystallization contains m +2 substructures, which are described as

Division of the substructuresNumber vector of

The grain size vector is

And S5, generating a corresponding microstructure optimization by combining the Vonoroi diagram by using the size information and the volume fraction of the deformed substructure grains and the recrystallized substructure grains calculated in the step S4.

Examples

The example uses hot rolled Ti micro-alloyed steel, the chemical composition of which is shown in table 1,

TABLE 1 Hot-rolled Ti microalloyed steel hot-rolled plate chemistry

Step 1, establishing a Ti microalloyed steel recrystallization model as shown in table 2:

TABLE 2 calculation model of recrystallization fraction and grain size

Wherein, X _s Is the static recrystallization fraction;

the time required for the static recrystallization fraction to reach 50%; t is the recrystallization time; z is a Zener parameter; r is a gas constant; t is the recrystallization temperature; ε is the strain; ε is the strain rate; d _DRX Is the grain size after dynamic recrystallization; d _SRX Is the grain size after static recrystallization; d ₀ Is the recrystallized grain size; d is the grain size after recrystallization.

And 2, reading rolling process parameters from a production field server so as to calculate the rolling temperature, strain rate and pass interval time of each pass, wherein the rolling temperature, the strain rate and the pass interval time are shown in a table 3.

TABLE 3 deformation conditions for each pass of rolling

And 3, calculating a recrystallization fraction time-dependent curve under the rolling process conditions shown in the table 3 according to the flow chart shown in fig. 1, wherein the horizontal axis in the graph is time, and the vertical axis is the recrystallization fraction.

And 4, calculating the shape and size of the grains after each pass of recrystallization and the volume fraction of the grains with different grain sizes, and combining a Vonoroi diagram to quickly generate a corresponding microstructure.

FIG. 2 is a graph showing the change of recrystallization fraction with time under the process conditions of the present invention, and FIGS. 3 and 4 are image information of the microstructure before finish rolling and after 4 th pass rolling, respectively, and it can be seen from FIGS. 3 and 4 that austenite is recrystallized equiaxed grains. As is clear from fig. 2, from the 5 th pass, the austenite is incompletely recrystallized, the unrecrystallized austenite becomes elongated deformed austenite, the volume fraction of the deformed austenite increases as the volume fraction of the unrecrystallized austenite increases, and the volume fraction of the recrystallized austenite gradually decreases. As shown in fig. 5, 6, and 7, the volume fractions of recrystallized austenite of the 5 th pass, the 6 th pass, and the 7 th pass of the finish rolling are 0.689,0.513, and 0.156, respectively.

Therefore, the method for realizing visualization of the recrystallization structure evolution in the hot rolling process adopts the structure, the austenite grains are divided into the recrystallization substructure grains and the deformation substructure grains, and the calculation method for calculating the grain size, the grain shape and the occupied volume fraction of the two types of grains is provided. And combining the calculation results, and quickly generating a corresponding microscopic structure by using a Vonoroi diagram to visualize the calculation results. Visualization information showing the structure evolution of the recrystallization process more intuitively and clearly.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the invention without departing from the spirit and scope of the invention.

Claims (6)

1. A method for realizing visualization of recrystallization texture evolution in a hot rolling process is characterized by comprising the following steps of:

s1, establishing a dynamic and static recrystallization fraction calculation model in an alloy rolling process;

s2, reading rolling process parameters, and calculating the strain and strain rate of each pass;

s3, calculating the dynamic recrystallization fraction in the rolling process and the static recrystallization fraction between two adjacent passes by using the rolling temperature, the strain and the strain rate;

s4, dividing the austenite grains into non-recrystallized deformed substructure grains and recrystallized substructure grains, and calculating the sizes and volume fractions of the deformed substructure grains and the recrystallized substructure grains;

and S5, generating a corresponding microstructure by combining a Vonoroi diagram by using the size information and the volume fraction of the deformed substructure grains and the recrystallized substructure grains calculated in the step S4.

2. The method for visualizing the evolution of a recrystallized structure of a hot rolling process according to claim 1, wherein: the alloy in the step S1 is one of common C-Mn series steel, nb microalloyed steel and Ti microalloyed steel, the chemical components of each alloy are 0.01-0.10 percent of C, 0.8-1.5 percent of Si, 0.15-2.5 percent of Mn, 0-0.015 percent of S, 0-0.019 percent of P, 0-0.08 percent of Nb and 0-0.10 percent of Ti according to weight percentage, and the balance is Fe and impurities existing in smelting.

3. The method for visualizing the evolution of a recrystallized structure in a hot rolling process according to claim 1, wherein: the rolling process parameters in the step S2 comprise rolling temperature, thickness of the steel plate rolled in each pass, rolling speed and diameter of the roller of each rolling stand.

4. The method for visualizing the evolution of a recrystallized structure in a hot rolling process according to claim 1, wherein: the size of the deformed substructure grain calculated in the step S4 is calculated from the grain size before rolling and the rolling reduction.

5. The method for visualizing the evolution of a recrystallized structure of a hot rolling process according to claim 1, wherein: and step 4, calculating the sizes of the recrystallized substructure grains according to the dynamic and static recrystallization fractions to calculate a model grain growth model and the sizes of the statically recrystallized grains.

6. The method for visualizing the evolution of a recrystallized structure of a hot rolling process according to claim 1, wherein said step S4 comprises the steps of:

s4.1 and the set of austenitic microstructures M is M = { S = { (S) ₁ ，S ₂ 8230, wherein S is a substructure with different shapes, the substructure is a basic unit for calculating the evolution process of an austenite microstructure, the grain size and the shape of austenite contained in each class of substructure are consistent, the substructure is divided into two classes, namely a recrystallized substructure RS with round grains and a deformed substructure DS with oval grains, the grain size of the recrystallized substructure is characterized by a diameter d, and the grain size in the deformed substructure is characterized by the length d of the major axis of the oval _M And minor axis length d _m Constituent Unit (d) _M ，d _m ) Characterizing;

s4.2, calculating through a calculation formula of the crystal grain size after dynamic recrystallization, the crystal grain size after static recrystallization and a crystal grain growth model to obtain new recrystallized grains with the same size, wherein the calculation formula of the size of the new deformed substructure is shown as a formula (1):

in the formula (I), the compound is shown in the specification,

and

the length of the long axis and the length of the short axis of the elliptic crystal grain before deformation; d is a radical of _M And d _m The length of the long axis and the length of the short axis of the deformed elliptical crystal grains; p is the deformation rate;

assuming that the microstructure of the i-th pass consists of a recrystallized substructure RS and m deformed substructures DS,

the fractional vector of each substructure is

The grain size vector is

For pass i +1, if the static recrystallization crystallization is complete, the microstructure after rolling consists of a new recrystallized substructure with a composition M _i+1 ＝{RS ⁱ⁺¹ F in fraction _i+1 = 1, size D _i+1 ＝{d ⁱ⁺¹ }，d ⁱ⁺¹ From d ⁱ Calculating the grain size and the grain growth model after static recrystallization;

s4.3, if the fraction of the static recrystallization of the (i + 1) th pass is f ⁱ⁺¹ Each initial substructure is decomposed into fractions f ⁱ⁺¹ Has a new recrystallized substructure and fraction of 1-f ⁱ⁺¹ New deformed substructure ofIn part, each new class of recrystallized substructure RS ⁱ⁺¹ Of size d ⁱ⁺¹ To RS ⁱ The new deformed substructure produced is noted

In the ratio of Rf ⁱ (1-f ⁱ⁺¹ ) Size of it

According to the calculation of the formula (1),

the new deformed substructure produced is noted

In a ratio of

Size of it

The microstructure after recrystallization contains m +2 substructures, which are recorded as

The fractional vector of each substructure is

The grain size vector is

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