WO2019109766A1 - 一种大单重、大断面特厚钢板辊式淬火过程的控制方法 - Google Patents

一种大单重、大断面特厚钢板辊式淬火过程的控制方法 Download PDF

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WO2019109766A1
WO2019109766A1 PCT/CN2018/113711 CN2018113711W WO2019109766A1 WO 2019109766 A1 WO2019109766 A1 WO 2019109766A1 CN 2018113711 W CN2018113711 W CN 2018113711W WO 2019109766 A1 WO2019109766 A1 WO 2019109766A1
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steel plate
section
temperature
heat transfer
transfer coefficient
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PCT/CN2018/113711
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English (en)
French (fr)
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付天亮
王昭东
田秀华
邓想涛
李勇
李家栋
韩冰
韩钧
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东北大学
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Priority to US16/340,008 priority Critical patent/US20190360066A1/en
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/60—Aqueous agents
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D11/00—Process control or regulation for heat treatments
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals

Definitions

  • the invention belongs to the technical field of metallurgy and relates to a method for controlling a steel plate roll quenching process.
  • the temperature field distribution of the extra-thick steel plate after quenching will affect the physical properties and mechanical processing properties of the steel plate to a large extent.
  • traditional immersion quenching the steel plate is immersed in a quenching tank or a quenching tank, which is limited by the volume of the vessel, has a slow cooling rate, and is unevenly distributed.
  • Roll quenching the steel plate enters the quenching machine through the rotating roller, and the high-pressure jet is sprayed onto the surface of the steel plate.
  • the cooling speed is greatly increased, and the steel plate can be cooled to room temperature in a short time.
  • the heat transfer is slow, resulting in a large difference between the core and the surface temperature, and the performance distribution after quenching is uneven.
  • the calculation of the quenching process can better improve this problem.
  • the temperature curve and cooling rate curve of the steel plate are calculated, and the temperature distribution and the change of the cooling rate at different positions of the steel plate during cooling are visually observed. The calculation results can serve the production well and reduce the production cost. .
  • Patent CN105445319A discloses a method and a device for determining the water-cooling heat transfer coefficient of a steel plate surface, and the image information of the non-water-cooled surface of the steel plate is collected by an infrared thermal imager to obtain an actual cooling curve of the non-water-cooled surface, and the finite element simulates the water-cooled surface to the non-water-cooled surface. Through the whole process, the simulated cooling curve of the non-water-cooled surface is obtained by continuously adjusting the water-cooling heat transfer coefficient.
  • the patent CN102507636A discloses a method for determining the interface heat transfer coefficient of a rapid cooling process of steel.
  • thermocouple spot welding By connecting the thermocouple spot welding to the temperature acquisition module, the surface temperature change data is obtained, and the interface heat transfer coefficient during the cooling process is obtained by the heat treatment software. Then, the temperature change of the workpiece cooling process is simulated and compared with the measured results until the change trend is in good agreement; the prior art does not involve the control method related to the large single-weight and large-section extra-thick steel plate quenching process. There is no mention of a specific method for correcting the heat transfer coefficient during the roll quenching process of large single-weight and large-section extra-thick steel sheets by using the modified model.
  • the object of the present invention is to provide a control method for a large single-weight, large-section and extra-thick steel plate roll quenching process, which is suitable for model control of a special thick steel plate in a quenching process, based on a mathematical model, combined with the actual production situation.
  • a control method for a large single-weight, large-section and extra-thick steel plate roll quenching process which is suitable for model control of a special thick steel plate in a quenching process, based on a mathematical model, combined with the actual production situation.
  • the temperature change and the change of the cooling rate of the steel plate head and the tail part on the steel plate surface, the quarter thickness and the core are visually displayed, which can be used to guide the adjustment of the process specification, save production cost, and obtain Good shape plate.
  • the specific technical solution of the present invention is a control method for a large single-weight, large-section and extra-thick steel plate roll quenching process, which comprises the following steps:
  • Step 1 reading the steel plate information and process parameters, including the thickness, length, carbon content, roll speed, and acceleration of the steel sheet;
  • Step 2 Set the initial heat transfer coefficient, calculate the model by temperature drop, and call the specific heat model and the heat transfer coefficient model, and modify the heat transfer coefficient of the air cooling section according to the modified model of the measured air temperature drop of the air cooling section, and then obtain the air cooling.
  • Stage temperature field
  • Step 3 Determine the heat transfer coefficient of the water-cooled section, including the determination of the water-cooling heat transfer coefficient of the high-pressure section and the determination of the water-cooling heat transfer coefficient of the low-pressure section; the determination of the water-cooling heat transfer coefficient of the high-pressure section; the function of the high-pressure section of the quencher is mainly to surface the steel plate The temperature is rapidly cooled to a lower temperature. Since the action time of the high pressure section is much lower than that of the low pressure section and cannot be directly obtained in actual production, the empirical data obtained from the experiment is used;
  • the determination of the water-cooling heat transfer coefficient in the low-pressure section can only directly obtain the surface temperature when the steel plate is quenched.
  • the surface of the steel plate changes only at the beginning of the quenching. After that, the temperature tends to be stable until the quenching machine , close to the temperature of the convective medium, it can not be directly used to calculate the convective heat transfer coefficient.
  • the temperature inside the steel plate cannot be directly obtained, so the water cooling coefficient cannot be directly corrected by the water cooling section.
  • the internal temperature is still higher than the surface temperature, the internal temperature is transmitted to the surface of the steel plate through heat conduction.
  • the surface reddening temperature at the time of air cooling after quenching can be used to utilize the heat transfer coefficient.
  • the modified model corrects the heat transfer coefficient of the low-pressure section water-cooled section; the specific method is that the temperature field after the air-cooling is taken as the initial temperature field of the water-cooled section, the initial heat transfer coefficient of the low-pressure section is given, the temperature field is calculated, and after water cooling The temperature field is used as the initial temperature field of the red return section to calculate the temperature value of the surface node after red return.
  • the modified model of the heat transfer coefficient is called to correct the water cooling heat transfer coefficient, and the air cooling heat transfer coefficient is unchanged;
  • the temperature drop calculation model is calculated, and the specific heat model and the heat transfer coefficient model are used to calculate the temperature field of the water cooling section and the red return section until the difference is within the allowable error range;
  • step 4 the temperature drop curve and the cooling rate curve of different positions in the quenching process of the steel plate according to the actual situation are obtained.
  • the correction model of the heat transfer coefficient in the above steps 2 and 3 is:
  • the upper limit value A is taken as the initial heat transfer coefficient for temperature field calculation. If the calculated value is higher than the target value, the heat transfer coefficient range is [A, 1.5A]. The upper limit of the interval above the interval is changed as the lower limit of the new interval, and 1.5 times of the lower limit of the new interval is taken as the upper limit of the new interval, and the heat transfer coefficient is taken as the upper limit of the interval. The calculated value is lower than the target value; it indicates that the actual convective heat transfer coefficient is within the interval, and the golden section method is used in the interval, and the interval is continuously reduced, and the difference between the measured value and the target value is within the allowable error range. At this time, the heat transfer coefficient value is the actual value.
  • the latent heat of phase change during the cooling process of the steel sheet is included in the average specific heat, so the internal heat source can be ignored;
  • the initial conditions are:
  • the boundary conditions are:
  • h x is the convective heat transfer coefficient
  • T f is the water temperature
  • F ox is the Fourier number
  • B ix is the number of Bi ;
  • the stability conditions are:
  • the temperature distribution of any node at any later time is calculated by difference.
  • the model calculation of the steel plate is divided into three parts according to the position of the roller table where the steel plate is located, respectively, the air cooling section before entering the quenching machine, the quenching section when passing through the quenching machine, and the quenching process.
  • the red-back phase after the machine is
  • the time of the air cooling section is determined; since the steel plate has a certain length and the time required to enter the quenching machine at different positions is different, the head and the tail are respectively calculated, and the head of the steel plate is moved at a uniform speed before entering the quenching machine, and the distance from the head to the quenching machine And the initial speed is calculated; when the head of the steel plate enters the quenching machine, the roller road starts to apply a certain acceleration, so the tail of the steel plate starts to accelerate in the air cooling section, and the position of the quenching machine is the length of the steel plate, and the initial speed, Distance and acceleration to calculate the tail air cooling time;
  • the quenching time is determined; the quenching time is divided into the time passing through the high pressure section and the time passing through the low pressure section to first determine the length of the high pressure section, and the quenching time of the steel head is directly calculated according to the initial velocity and acceleration of the roller table; Since the steel plate is accelerated when the steel plate head enters the quenching machine, the time and acceleration of the air cooling acceleration portion are used to determine the speed at which the tail enters the quenching machine, and then the speed and acceleration according to the calculation are used to determine the required high pressure section. Time, the steel plate passes the low pressure period time according to the swing time;
  • the determination of the time of returning to the red zone is to start timing when the steel plate is quenched by the stopwatch, and the reddening temperature of the steel plate at different times is measured for the same position of the steel plate, and the timing is stopped after the red return, and the red color is taken back.
  • the maximum temperature is used as the target temperature in the simulation calculation, and the corresponding time is taken as the time of the red-back phase.
  • the initial temperature field model of each step in the above steps 2 and 3 is established: the temperature of the steel plate is taken as the initial temperature field of the air cooling section, and the simulated temperature field and the quenching machine before the air cooling are calculated by using the temperature field model. The temperature measured at the temperature point is compared and corrected, and finally the temperature field after air cooling is obtained, and this is used as the initial temperature field of the water cooling section. The water cooling section does not need to be corrected, and the model calculation result is directly transmitted to the reddening stage. As the initial temperature field of the reddening phase.
  • the output result of the above step 4 includes the air-cooling section, the water-cooling high-low pressure section heat exchange coefficient value, the steel plate head, the tail surface, the quarter, the central part temperature change curve and the cooling rate change curve.
  • the initial parameters are in accordance with the actual production regulations. Considering the on-site production conditions, the required measurement data can be directly obtained in production;
  • the output result is the cooling curve and the cooling speed curve at different thicknesses, which more intuitively shows the heart and table temperature difference, the heart and table cooling speed difference, the head-to-tail temperature difference, and the head-to-tail cooling speed difference, which can be used to guide the adjustment of the production process;
  • Figure 1 Flow chart of the calculation process.
  • Figure 4 Cooling rate curve after filtration of the high pressure section.
  • the thickness of the steel plate is 132mm, the length is 7250mm, the carbon content is 0.15%, the roller speed is 0.2m/s, the acceleration is 0.00015m/s 2 , the high pressure section of the quenching machine is 3.2m, and the initial heat transfer coefficient is 100W/(m 2 K ), high pressure section 20000W / (m 2 K), low pressure section 8000W / (m 2 K), water temperature 22.1 ° C, tapping temperature 910 ° C, temperature 830 ° C before entering the quenching machine, air cooling time 45s, low pressure swing time 1560s, red The time is 142s, and the temperature after returning to red is 28 °C.
  • the cell length is 1 mm and the time step is 0.5 s.
  • the calculation flow is as shown in FIG.
  • the calculation results show that the air-cooling section heat transfer coefficient is 124.64W/(m 2 K), and the low-pressure section water-cooling heat transfer coefficient is 2250W/(m 2 K).
  • the temperature drop curve is shown in Figure 2. As can be seen from the figure, the steel plate enters the water-cooled high-pressure section via the air-cooling section, and the surface temperature rapidly decreases. After entering the low-pressure section, the temperature is slightly increased due to the internal temperature, which is compared with the temperature. The surface, the thickness of the quarter and the temperature of the heart are cooled more slowly.
  • the cooling rate curve is shown in Figure 3. Corresponding to the temperature drop curve, it can be found that in the high pressure section, the surface cooling rate rises rapidly.
  • the cold speed curve After entering the low pressure section, the cold speed curve has a negative value indicating that the temperature has risen due to the short surface.
  • the cooling rate in the time is much higher than other times, and it is not convenient to observe the cooling speed at other times. Therefore, after filtering off part of the cooling rate, as shown in Figure 4, it can be found that one quarter and the heart are cold when the temperature difference between the heart and the heart is large. Gradually increase, and then as the temperature decreases, the cooling rate gradually decreases.

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Abstract

一种大单重、大断面特厚钢板辊式淬火过程的控制方法，包括比热模型、热传导系数模型，温度场模型以及修正模型。具体为，输入钢板参数；工艺规程；实测参数。利用温度场模型并调用比热模型、热传导系数模型依次对冷却空冷段、水冷段、返红段进行计算，并分别通过修正模型对温度场进行修正。模拟结果为得到一组不同厚度处冷却曲线及冷速曲线。该控制方法的优点在于结合生产实际情况，得到符合实际的温降、冷速曲线，通过模型计算替代部分实际调试过程，可用于指导工艺规程的调整，节约生产成本，并能获得板形良好的产品。

Description

一种大单重、大断面特厚钢板辊式淬火过程的控制方法 技术领域
本发明属于冶金技术领域，涉及钢板辊式淬火过程控制方法。
背景技术
特厚钢板淬火后温度场分布，在很大程度上会影响钢板的物理性能和机械加工性能。传统的浸入式淬火，将钢板浸入淬火池或淬火槽中，受容器体积限制，冷却速度较慢，且分布不均。辊式淬火，钢板通过转动的辊道进入淬火机，高压射流喷射到钢板表面，相比于传统淬火方式，冷却速度大幅度增加，钢板在短时间内即可冷却至室温。但由于钢板厚度较大，传热较慢，导致心部与表面温度相差较大，淬火后性能分布不均。淬火过程计算，能够较好的改善这一问题。通过设置不同的参数，计算得到钢板的温度曲线、冷速曲线，直观的观察到冷却中钢板不同位置出的温度分布情况及冷速变化情况，计算结果可以很好的服务于生产，降低生产成本。
专利CN105445319A公开了一种测定钢板表面水冷换热系数的方法及装置，由红外热像仪采集钢板非水冷面图像信息，得到非水冷面的实际冷却曲线，有限元模拟水冷面到非水冷面的全过程，通过不断调整水冷换热系数，得到非水冷面的模拟冷却曲线。专利为CN102507636A公开了一种测定钢的快速冷却过程界面换热系数的方法，通过将热电偶点焊连接到温度采集模块，得到表面温度变化数据，利用热处理软件得到冷却过程中的界面换热系数，再以此模拟工件冷却过程的温度变化，并与实测结果进行对比，直至变化趋势吻合良好；现有技术中均未涉及与大单重、大断面特厚钢板辊式淬火过程有关的控制方法，更未提及利用修正模型对大单重、大断面特厚钢板辊式淬火过程中的换热系数进行修正的具体方法。
发明内容
本发明的目的是提供一种大单重、大断面特厚钢板辊式淬火过程的控制方法，该方法适用于特厚钢板在淬火过程中的模型控制，以数学模型为基础，结合生产实际情况，以曲线的形式直观的表现出钢板头部、尾部在钢板表面、四分之一厚度处以及心部的温度变化及冷速变化，可用于指导工艺规程的调整，节约生产成本，并能获得板形良好的产品。
本发明的具体技术方案为，一种大单重、大断面特厚钢板辊式淬火过程的控制方法，其特征在于，包括如下步骤：
步骤1，读取钢板信息及工艺参数，包括钢板的厚度、长度、含碳量、辊速、加速度；
步骤2，设置初始换热系数，利用温降计算模型，并调用比热模型、热传导系数模型，根据实测空冷段温降利用换热系数的修正模型对空冷段换热系数进行修正，进而得到空冷段温度场；
步骤3，确定水冷段换热系数，包括高压段水冷换热系数的确定和低压段水冷换热系数的确定；高压段水冷换热系数的确定，淬火机高压段的作用主要是将钢板的表面温度快速冷却到一个较低的温度，由于高压段的作用时间远低于低压段且实际生产中无法直接获得，故采用实验所得经验数据；
低压段水冷换热系数的确定，由于钢板出淬火机时只能直接获得表面温度，而在淬火过程中钢板表面仅仅在淬火开始时温度变化剧烈，此后，至出淬火机，其温度趋于稳定，接近对流介质温度，故不能直接用于计算对流换热系数。而钢板内部的温度无法直接获得，故无法通过水冷段对水冷换热系数直接进行修正计算。钢板在离开淬火机时，由于内部的温度仍高于表面温度，通过热传导作用，会将内部的温度传递到钢板的表面，因此，可采用淬火后空冷时的表面返红温度利用换热系数的修正模型对低压段水冷段的换热系数进行修正；具体方法为以出炉空冷后的温度场为水冷段的初始温度场，给定低压段初始换热系数，进行温度 场计算，并以水冷后温度场作为返红段初始温度场计算返红后表面节点的温度值，与测量值进行比较，调用换热系数的修正模型对水冷换热系数进行修正，空冷换热系数不变；并重新利用温降计算模型，并调用比热模型、热传导系数模型进行水冷段、返红段温度场计算，至差值在允许误差范围内；
步骤4，得到符合实际情况的钢板淬火过程中不同位置的温降曲线，冷速曲线。
由于无法直接测得淬火过程中的对流换热系数，因此需要通过比较计算温度与实测温度，利用修正模型对换热系数进行修正，进而对温度场进行修正。上述步骤2、步骤3中所述换热系数的修正模型为：
给定初始换热系数区间范围[0,A]，取上限值A作为初始换热系数进行温度场计算，若计算值高于目标值，则取换热系数范围为[A,1.5A]；每次更改区间以上一区间的上限值作为新区间的下限值，并以新区间的下限值的1.5倍作为新区间的上限值，至换热系数取值为该区间的上限，计算值低于目标值为止；表明此时实际对流换热系数处于该区间内，在该区间内采用黄金分割法，不断缩小所在区间，至实测值与目标值差值在允许误差范围内，此时换热系数值即为实际值。
进一步地，上述步骤2、3中：
1)比热模型的计算；比热系数主要与钢板的含碳量及温度有关；含碳量以设定的定值作为界定范围，当含碳量不为上述值时，先确定其所对应的左右界值，通过插值的方式确定含碳量的权重，再比定温度所在区间，从而确定钢板的比热值；
2)热传导系数模型的计算；首先实验得出不同含碳量钢板在不同温度下的比热值及热传导系数值，然后通过插值的方式确定其他含碳量、其他温度对应的比热及热传导系数值；
3)温降计算模型为：
建立笛卡尔坐标系中的一维非稳态导热微分方程：
Figure PCTCN2018113711-appb-000001
其中：
Figure PCTCN2018113711-appb-000002
x为划分单元格长度；d为钢板厚度；t为时间；T为温度；a为导温系数，
Figure PCTCN2018113711-appb-000003
为内热源；λ为淬火板热传导系数；ρ为淬火钢板密度；c为淬火板比热；
计算时将钢板冷却过程中的相变潜热计入平均比热内，因此可以忽略内热源；
初始条件为：
T(x,0)＝T0(0＜x＜d,t＞0)
边界条件为：
Figure PCTCN2018113711-appb-000004
为了提高傅里叶数的收敛性和稳定性并使模型更具有更小的误差，采用Crank-Nicolson差分方法；
Figure PCTCN2018113711-appb-000005
t为时间；i为节点，0≤i≤I；建立温度场如下:
内部节点：
Figure PCTCN2018113711-appb-000006
边界节点：
Figure PCTCN2018113711-appb-000007
其中
Figure PCTCN2018113711-appb-000008
h x为对流换热系数；T f为水温；
Figure PCTCN2018113711-appb-000009
为时间为t时钢板第i个节点所对应的温 度值；F ox为傅里叶数；B ix为毕渥数；
稳定性条件为:
Figure PCTCN2018113711-appb-000010
当已知初始温度场及换热系数的条件下，通过差分计算出之后任一时刻任一节点的温度分布情况。
进一步地，上述温降计算模型中冷却时间的控制：钢板的模型计算根据钢板所在的辊道位置分为三部分，分别为进入淬火机前的空冷段、通过淬火机时的淬火段和通过淬火机以后的返红阶段；
空冷段的时间确定；由于钢板具有一定的长度，不同位置进入淬火机所需要的时间不同，因此对头尾分别进行计算，钢板头部进入淬火机前为匀速运动，通过头部到淬火机的距离及初速度进行计算；当钢板头部进入淬火机以后辊道开始施加一定的加速度，所以钢板的尾部在空冷段即开始进行加速，此时及距离淬火机的位置为钢板长度，通过初速度、距离以及加速度来对尾部空冷时间进行计算；
淬火段时间的确定；淬火段时间分为通过高压段的时间和通过低压段的时间首先确定高压段长度，根据设定好辊道的初速度和加速度，直接计算出钢板头部的淬火时间；由于在钢板头部进入淬火机时即对钢板进行加速，通过之前空冷加速部分的时间和加速度确定尾部进入淬火机时的速度，再根据此时的速度和加速度计算确定其通过高压段所需要的时间，钢板通过低压段时间根据摆动时间确定；
返红段时间的确定；其具体方法为在钢板出淬火机时，通过秒表开始进行计时，针对钢板的同一位置，测量其在不同时刻的返红温度，返红结束后停止计时，取返红温度最大值作为模拟计算中的目标温度，其对应时间作为返红阶段的时间。
进一步地，上述步骤2、3中各段初始温度场模型的建立：以钢板出加热炉时温度作为空冷段的初始温度场，利用温度场模型计算得到的空冷后模拟温度场与淬火机前测温点测得的温度进行比较修正，最终得到符合实际的空冷后温度场， 并以此作为水冷段的初始温度场，水冷段不需要进行修正计算，直接将模型计算结果传递到返红阶段，作为返红阶段的初始温度场。
进一步地，上述步骤4输出结果包括空冷段、水冷高低压段换热系数值，钢板头部、尾部的表面、四分之一、中心部的温度变化曲线及冷速变化曲线。
本发明具有以下优点：
1)初始参数符合实际生产规程，考虑到现场生产条件，所需测量数据在生产中可以直接获得；
2)各阶段计算结果分别依据实测值进行修正，计算结果与钢板实际冷却曲线更贴近；
3)输出结果为不同厚度处冷却曲线、冷速曲线，更加直观的展现心、表温差，心、表冷速差，头尾温差，头尾冷速差，可用于指导调整生产工艺；
4)通过计算代替部分现场调试，减少能源消耗，降低生产成本。
附图说明
图1：计算过程流程图。
图2：计算所得温度变化曲线。
图3：计算所得冷却速度变化曲线。
图4：过滤高压段后冷却速度变化曲线。
具体实施方式
1)参数的输入。包括钢板参数：厚度、长度、含碳量；工艺规程：辊道速度，加速度，淬火机高压段长度，出炉温度，换热系数初值；实测参数：出炉温度、进入淬火机前温度、返红时间、返红后温度；
2)空冷段、淬火段、返红段时间的确定。由于钢板具有一定的长度，不同位置进入淬火机所需要的时间不同，因此对头尾分别进行计算，钢板头部进入淬火机前为匀速运动，进入淬火机高压段后为加速运动，此后在低压段进行摆动。 钢板尾部的运动方式为进入淬火机前空冷段首先为匀速运动，当钢板头部进入淬火机后为加速运动，高压段为加速运动，此后在低压段进行摆动。空冷段及高压段时间通过距离、初速度、加速度进行计算，低压段时间通过设定的摆动时间确定，返红段通过计时确定；
3)空冷段温度场的计算，以出炉温度建立初始温度场，每个时间步分别对不同节点的比热、热传导系数进行计算，然后调用温度场模型对空冷温度场进行计算，将计算结果与实测值进行比较，调用修正模型，对空冷换热系数进行修正，得到空冷后温度场。
4)水冷段时间的确定。分别计算钢板头部、中间部位、尾部通过淬火机高压段所需要的时间，根据摆动时间确定钢板通过低压段时间；
5)水冷温度场的计算。以计算的空冷后温度场为初始温度场，调用比热模型、导热系数模型、温度场模型，计算获得水冷后温度场；
6)返红后温度场的计算。以水冷后温度场为的初始温度场，换热系数值采用修正后的空冷换热系数值，调用比热模型、导热系数模型、温度场模型对返红温度场进行计算，将计算结果与实测值进行比较，未在允许误差范围内，调用修正模型对水冷换热系数进行修正，重新计算步骤5、6；
7)计算结果的输出。绘制钢板头尾部表面、四分之一厚度处、心部在空冷段及淬火段的温降曲线、冷速曲线。
实施例：
钢板厚度132mm，长度7250mm，含碳量0.15％，辊道速度0.2m/s，加速度0.00015m/s 2，淬火机高压段长度3.2m，换热系数初值：空冷段100W/(m 2K)，高压段20000W/(m 2K)，低压段8000W/(m 2K)，水温22.1℃、出炉温度910℃、进入淬火机前温度830℃、空冷时间45s，低压摆动时间1560s，返红时间142s，返红后温度28℃。取单元格长度1mm，时间步长0.5s，计算流程如附图1所示。
计算结果：空冷段换热系数值124.64W/(m 2K)，低压段水冷换热系数2250W/(m 2K)。温降曲线如附图2所示，由图可知，钢板经由空冷段进入水冷的高压段，表面温度迅速降低，进入低压段后由于内部的温度向外传递，温度有少许的回升，相较于表面，四分之一厚度处及心部温度冷却较缓慢。冷速曲线如附图3所示，与温降曲线相对应可以发现，在高压段，表面冷速迅速升高，进入低压段后，冷速曲线为负值代表温度有所上升，由于表面短时间内冷速远高于其他时刻，不便于观察其他时刻冷速，因此过滤掉部分后冷速如附图4所示，可以发现，四分之一和心部在心表温差较大时冷速逐渐增加，此后随着温度的降低，冷速逐渐降低。

Claims (6)

  1. 一种大单重、大断面特厚钢板辊式淬火过程的控制方法，其特征在于，包括如下步骤：
    步骤1，读取钢板信息及工艺参数，包括钢板的厚度、长度、含碳量、辊速、加速度；
    步骤2，设置初始换热系数，利用温降计算模型，并调用比热模型、热传导系数模型，根据实测空冷段温降利用换热系数的修正模型对空冷段换热系数进行修正，进而得到空冷段温度场；
    步骤3，确定水冷段换热系数，包括高压段水冷换热系数的确定和低压段水冷换热系数的确定；高压段水冷换热系数的确定，采用实验所得经验数据；
    低压段水冷换热系数的确定，采用淬火后空冷时的表面返红温度利用换热系数的修正模型对低压段水冷段的换热系数进行修正；具体方法为以出炉空冷后的温度场为水冷段的初始温度场，给定低压段初始换热系数，进行温度场计算，并以水冷后温度场作为返红段初始温度场计算返红后表面节点的温度值，与测量值进行比较，调用换热系数的修正模型对水冷换热系数进行修正，空冷换热系数不变；并重新利用温降计算模型，并调用比热模型、热传导系数模型进行水冷段、返红段温度场计算，至差值在允许误差范围内；
    步骤4，得到符合实际情况的钢板淬火过程中不同位置的温降曲线，冷速曲线；
    上述步骤2、步骤3中所述换热系数的修正模型为：
    给定初始换热系数区间范围[0,A]，取上限值A作为初始换热系数进行温度场计算，若计算值高于目标值，则取换热系数范围为[A,1.5A]；每次更改区间以上一区间的上限值作为新区间的下限值，并以新区间的下限值的1.5倍作为新区间的上限值，至换热系数取值为该区间的上限，计算值低于目标值为止；表明 此时实际对流换热系数处于该区间内，在该区间内采用黄金分割法，不断缩小所在区间，至实测值与目标值差值在允许误差范围内，此时换热系数值即为实际值。
  2. 根据权利要求1所述的大单重、大断面特厚钢板辊式淬火过程的控制方法，其特征在于，温降计算模型中冷却时间的控制：钢板的模型计算根据钢板所在的辊道位置分为三部分，分别为进入淬火机前的空冷段、通过淬火机时的淬火段和通过淬火机以后的返红阶段；
    空冷段的时间确定；对头尾分别进行计算，钢板头部进入淬火机前为匀速运动，通过头部到淬火机的距离及初速度进行计算；当钢板头部进入淬火机以后辊道开始施加一定的加速度，所以钢板的尾部在空冷段即开始进行加速，此时及距离淬火机的位置为钢板长度，通过初速度、距离以及加速度来对尾部空冷时间进行计算；
    淬火段时间的确定；淬火段时间分为通过高压段的时间和通过低压段的时间首先确定高压段长度，根据设定好辊道的初速度和加速度，直接计算出钢板头部的淬火时间；由于在钢板头部进入淬火机时即对钢板进行加速，通过之前空冷加速部分的时间和加速度确定尾部进入淬火机时的速度，再根据此时的速度和加速度计算确定其通过高压段所需要的时间，钢板通过低压段时间根据摆动时间确定；
    返红段时间的确定；其具体方法为在钢板出淬火机时，通过秒表开始进行计时，针对钢板的同一位置，测量其在不同时刻的返红温度，返红结束后停止计时，取返红温度最大值作为模拟计算中的目标温度温度，其对应时间作为返红阶段的时间。
  3. 根据权利要求1或2所述的大单重、大断面特厚钢板辊式淬火过程的控制方法，其特征在于，步骤2、3中各段初始温度场模型的建立：以钢板出加热炉时温度作为空冷段的初始温度场，利用温度场模型计算得到的空冷后模拟温度场与淬火机前测温点测得的温度进行比较修正，最终得到符合实际的空冷后温度场，并以此作为水冷段的初始温度场，水冷段不需要进行修正计算，直接将模型计算结果传递到返红阶段，作为返红阶段的初始温度场。
  4. 根据权利要求1或2所述的大单重、大断面特厚钢板辊式淬火过程的控制方法，其特征在于，步骤4输出结果包括空冷段、水冷高低压段换热系数值，钢板头部、尾部的表面、四分之一、中心部的温度变化曲线及冷速变化曲线。
  5. 根据权利要求3所述的大单重、大断面特厚钢板辊式淬火过程的控制方法，其特征在于，步骤4输出结果包括空冷段、水冷高低压段换热系数值，钢板头部、尾部的表面、四分之一、中心部的温度变化曲线及冷速变化曲线。
  6. 根据权利要求1或2或5所述的大单重、大断面特厚钢板辊式淬火过程的控制方法，其特征在于，步骤2、3中：
    1)比热模型的计算；比热系数主要与钢板的含碳量及温度有关；含碳量以设定的定值作为界定范围，当含碳量不为上述值时，先确定其所对应的左右界值，通过插值的方式确定含碳量的权重，再比定温度所在区间，从而确定钢板的比热值；
    2)热传导系数模型的计算；首先实验得出不同含碳量钢板在不同温度下的比热值及热传导系数值，然后通过插值的方式确定其他含碳量、其他温度对应的比热及热传导系数值；
    3)温降计算模型为：
    建立笛卡尔坐标系中的一维非稳态导热微分方程：
    Figure PCTCN2018113711-appb-100001
    其中：
    Figure PCTCN2018113711-appb-100002
    x为划分单元格长度；d为钢板厚度；t为时间；T为温度；a为导温系数，
    Figure PCTCN2018113711-appb-100003
    为内热源；λ为淬火板热传导系数；ρ为淬火钢板密度；c为淬火板比热；
    计算时将钢板冷却过程中的相变潜热计入平均比热内，因此可以忽略内热源；
    初始条件为：
    T(x,0)＝T0(0＜x＜d,t＞0)
    边界条件为：
    Figure PCTCN2018113711-appb-100004
    为了提高傅里叶数的收敛性和稳定性并使模型更具有更小的误差，采用Crank-Nicolson差分方法；
    Figure PCTCN2018113711-appb-100005
    t为时间；i为节点，0≤i≤I；建立温度场如下:
    内部节点：
    Figure PCTCN2018113711-appb-100006
    边界节点：
    Figure PCTCN2018113711-appb-100007
    其中
    Figure PCTCN2018113711-appb-100008
    h x为对流换热系数；T f为水温；
    Figure PCTCN2018113711-appb-100009
    为时间为t时钢板第i个节点所对应的温度值；F ox为傅里叶数；B ix为毕渥数；
    稳定性条件为:
    Figure PCTCN2018113711-appb-100010
    当已知初始温度场及换热系数的条件下，通过差分计算出之后任一时刻任一节点的温度分布情况。
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