Temperature Field Prediction Based On Finite Difference Method And Heat Transfer Model

In various industrial scenarios, it is not only necessary to calculate the temperature at a certain time in the processing process, but also sometimes in order to be more accurate, it is necessary to simulate the temperature field (temperature at any position) of the processed workpiece at any time point. Finite difference method is an ideal computing tool.

I.  World Leading Feat

In 2005, our team completed a feat: under the calculation conditions at that time, in the web version of the software, we can use the finite difference method to complete more than 50 processes, such as air cooling, dozens of passes rolling of wire and bar, water cooling and so on, and calculate the temperature field at any time point! And the calculation results are consistent with the measured data! (see the figure below)

Our team further optimized the finite difference method software that has been used by a world-class large company for many years, such as re modeling with more than ten books and thousands of pages of test results sorted out all over the world for decades to determine the accurate heat transfer coefficient model; Then use the calculation model of relevant temperature in hundreds of models developed by our team!

In the operation of the finite difference method, in order to make the web version software run in a short time, the operation process has to be greatly improved, which also restricts the accuracy of the operation. If you refine the mesh and increase the operation time, the operation accuracy can be greatly improved! In the comparison with the field measurement data, since only the surface temperature can be measured, only the surface temperature can be compared!

In the competition with European and American counterparts in the past few decades, the project leader has always taken the lead with the high precision of the model!

Although the finite element method (the doctoral project field of the project leader) can also simulate the temperature, it is too large a calculation system, and it still needs several hours of calculation time at that time!

II.  Simulation Method

Based on the finite difference method, the temperature models that have been used in the field for many years, such as the air cooling temperature before and after each rolling pass, the temperature of each rolling pass, the water cooling temperature and the model calculated by steelmo, are further optimized.

In this example, special consideration should be given to the heat transfer between high-temperature steel (1200-1000 ℃) and water during water cooling, and the heat transfer between high-temperature steel and steel roll with pass during dozens of passes; Relatively speaking, the heat transfer with air is relatively easy!

This model requires several stages of parameter input:

（1）Phase of cooling in air

（2）In the rolling process, the data of nearly 30 passes (pass parameters and reduction parameters, etc.) need to be input one by one

（3）Water cooling parameters, such as water temperature, whether there is stirring and relative speed (it belongs to high-speed rolling, and the final rolling speed can be as high as 100M / S!) etc.

The input parameters mainly include: steel grade, initial size, initial temperature, final rolling size, various thermal and mechanical properties, etc.

For properties that vary with temperature, such as flow stress, Young's modulus, Poisson's ratio, specific heat, density, thermal conductivity, etc., accurate change trends are input.

The project leader personally measured the young's modulus of a steel at high temperature in his early years, and the measurement results varied exponentially in different temperature ranges; Since then, thousands of materials have been collected in major libraries around the world, and the above high-temperature properties change with temperature. Relevant data can be found in the material high temperature performance section of this website.

III.  Technical Application Examples

The project leader learned about the American steelmo production line when he was in a domestic university; Since then, as a senior engineer of this company in the United States, he led the model development, so he has a lot of first-hand information on relevant technology development.

In the final stage of production, high-temperature wire rod is coiled in air-cooled environment; Through special temperature and processing technology, the state with the best mechanical properties is formed. This is the main process of steelmo.

In steelmo process, the core temperature of the wire rod after rolling is high, the surface temperature is relatively low, and the temperature change continues. In fact, the measured surface temperature is not the same as the wire rod temperature, which should be grasped through the simulation of temperature field. Moreover, the temperature field near steelmo roll is also changing continuously, and the obtained relevant temperature needs to be effectively simulated and accurately determined. The change of temperature directly affects the change of microstructure, and then affects the mechanical properties.

Figure 1: temperature field prediction results based on finite difference method and heat transfer model

Project Cases

   Summary, Key Projs, Model Projs, Rolling Mills
   Model System, Intelli Equip., New Level 2, Li-Batt

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