JP4258235B2 - Steel heating method and program thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for heating a steel material after hot rolling, and particularly to an in-line heat treatment technique in which an induction heating device is arranged on a line.
[0002]
[Prior art]
A thick steel plate is manufactured by a method of quenching a hot-rolled steel plate by quenching or accelerated cooling and then tempering it in order to increase the strength and toughness.
[0003]
In recent years, quenching and accelerated cooling have been performed online, but tempering (hereinafter referred to as “heating”) is still performed offline using a gas-fired furnace and requires a long time. This significantly hinders the productivity of thick steel plates.
[0004]
For this reason, as a method of performing the heat treatment in-line, a technique is disclosed in which a plurality of solenoid induction heating devices are arranged in series in a line and the thick steel plate is heat-treated (see, for example, Patent Document 1).
[0005]
[Patent Document 1]
JP-A-48-25239 [0006]
[Problems to be solved by the invention]
By the way, the steel plate immediately after cooling often warps upward or downward due to residual stress. Therefore, if such a steel plate is allowed to pass through the induction heating device as it is, not only the induction heating device is damaged by contact with the steel plate, but also there is a risk of destruction in some cases.
[0007]
In addition, when such an accident occurs, the steel sheet stops in the induction heating apparatus, and rolling is stopped until recovery, which significantly impedes the production efficiency. Therefore, when heat treatment is performed using an induction heating device, it is indispensable to use a correction device so that bending does not occur at the front and rear ends of the steel plate.
[0008]
However, passing the straightening device lowers the temperature of the thick steel plate due to heat removal by the straightening roll, heat removal by the cooling water in the straightening device, or the like. Therefore, in the subsequent heat treatment with the induction heating device, it is necessary to consider the influence of the correction device, but there is no disclosure of a technique for heat treatment including the correction device.
[0009]
The present invention has been made in view of such circumstances, and provides a heating method capable of accurately heat-treating a steel material such as a thick steel plate using a straightening device and an induction heating device, and a program therefor. For the purpose.
[0010]
[Means for Solving the Problems]
The present invention for solving the above-described problems has a correction device installed on a line and at least one induction heating device, and passes the correction device and then passes the induction heating device. In the heating method for heating a steel material , based on information including the temperature of the steel material on the entry side of the straightening device and the conveying speed of the steel material, a temperature drop amount estimation step for estimating the temperature drop amount of the steel material in the straightening device, and And a power calculating step for calculating the power supplied to the induction heating device for heating the steel material to the target temperature based on the temperature drop amount.
[0011]
Moreover, the heating method of the steel materials which concerns on the other situation of this invention is the heating method of the said steel materials, The amount-of-fall estimation process estimates the 1st temperature fall amount by contact with steel materials and a correction | amendment roll, and A step of estimating a second temperature drop due to heat dissipation from the steel to the atmosphere, and a step of estimating a third temperature drop due to water cooling of the steel.
[0012]
Moreover, the heating method of the steel material which concerns on the other situation of this invention WHEREIN: In the heating method of the said steel material, the estimated temperature of the steel material in the outgoing side of the straightening apparatus calculated | required from the estimated amount of temperature drop of steel materials, and the outgoing side of the straightening apparatus And a correction step of correcting the temperature drop amount estimation model of the steel material based on the measured temperature of the steel material on the exit side of the straightening device measured by the thermometer provided in.
[0016]
The present invention also includes a straightening device installed on a line and at least one induction heating device, and after passing the straightening device, the steel material is heated by passing the induction heating device. In the heat treatment program, based on information including the temperature of the steel material on the entry side of the straightening device and the conveyance speed of the steel material, a temperature drop amount estimation procedure for estimating the temperature drop amount of the steel material in the straightening device, and the estimated temperature An electric power calculation procedure for calculating electric power to be supplied to the induction heating device for heating the steel material to the target temperature is executed based on the descending amount.
[0017]
Further, the heat treatment program according to another aspect of the present invention is the above-described program, wherein the descent amount estimation procedure is a procedure for estimating a first temperature drop amount due to contact between the steel material and the straightening roll, from the steel material to the atmosphere. A computer is made to perform the procedure which estimates the 2nd temperature fall amount by heat dissipation, and the procedure which estimates the 3rd temperature fall amount by water cooling of steel materials.
[0018]
The heat treatment program according to another aspect of the present invention is the above-described program, wherein the estimated temperature of the steel material on the outlet side of the straightening device determined from the estimated temperature drop of the steel material and the temperature provided on the outlet side of the straightener device Based on the measured temperature of the steel material on the outlet side of the straightening device measured by the meter, the computer is further caused to execute a correction procedure for correcting the temperature drop estimation model of the steel material.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a side view showing a schematic configuration of a heat treatment facility according to a first embodiment to which a heating method according to the present invention is applied. This heat treatment equipment includes a plurality of induction heating devices 1, a straightening device 2 installed in front of the induction heating device 1, a temperature detection that detects the temperature of the steel material 3 provided before and after the induction heating device 1 and before and after the straightening device 2. It comprises a container 4 and a conveying roller 5 for conveying the steel material 3. Here, in FIG. 1, illustrations of power equipment for supplying power to the induction heating device 1 and a control device for controlling the power are omitted.
[0020]
Hereinafter, the heating method of the first embodiment according to the present invention will be described using the heat treatment equipment having the configuration shown in FIG.
[0021]
When heat-treating a steel material, heating conditions such as a target temperature to be heated, a heating upper limit temperature, and a lower limit temperature are given in accordance with the type of material. The electric power supplied to the induction heating apparatus 1 is determined based on the heating conditions and the operating conditions of the steel material conveyance speed and the steel material temperature measured immediately before heating. And when determining the heating power supplied to the induction heating device 1, it is necessary to consider the temperature drop of the steel 3 due to the cooling of the air between the induction heating devices, and when using the straightening device 2, It is necessary to obtain the power to be distributed to each induction heating device after including the temperature drop amount of the steel material 3 in the straightening device 2.
[0022]
FIG. 2 is a flowchart showing a procedure for obtaining the heating power supplied to the induction heating apparatus. This process may be realized by incorporating a program into a processing device (not shown).
[0023]
In step S1, the type, thickness, width, target heating temperature, and the like of the steel material to be heated are acquired. Such information may be acquired from the outside by transmission or setting input by the processing device, or may be extracted from data stored in the processing device in advance.
[0024]
In step S2, the actual temperature value of the steel material on the entry side of the straightening device 2 and the conveyance speed are acquired. As the actual temperature value of the steel material, the value measured by the temperature detector 4 is used. The conveyance speed may be a value actually measured from the number of rotations of the conveyance roller 5, or may be acquired from the outside by transmission or setting input by the processing device, or from data stored in the processing device in advance. What to extract may be used.
[0025]
In step S3, the temperature drop amount of the steel material 3 in the straightening device 2 is estimated based on these data.
[0026]
The amount of temperature drop in the straightening device 2 can be obtained by the equation (1) by considering heat removal by the roll of the straightening device 2, heat removal by the atmosphere in the straightening device, and heat removal by the cooling water.
[0027]
ΔT _L = ΔT _R + ΔT _A + ΔT _W (1)
ΔT _L : Estimated value of temperature drop in straightening device ΔT _R : Contact heat removal by roll, ΔT _A : Cooling by air, ΔT _W : Cooling by water cooling Further, each heat removal term is expressed by equations (2) to (5) ).
[0028]
ΔT _R = h _R (T _S −T _R ) / √ (τ _R ³ ) (2)
τ _R = L _R / ν (3)
h _R : roll heat transfer coefficient, T _S : steel surface temperature, T _R : roll surface temperature τ _R : roll contact time, L _R : roll contact distance, ν: transport speed, where roll contact distance (L _R ) Means the length obtained by adding the contact lengths (steel material conveying direction) between each straightening roll and the steel material 3 for all straightening rolls. In the straightening device, in order to straighten the steel material 3, the sheet is passed through the roll in a state where the steel material 3 is wound by a predetermined length. Accordingly, the straightening roll and the steel material 3 are in contact with each other during the time obtained by dividing the roll contact distance by the conveyance speed (ν), and the steel material 3 receives heat from the straightening roll.
[0029]
ΔT _A = h _A (T _s −T _A ) (4)
[Delta] T _A: cooling by ambient temperature _{h A:} heat transfer coefficient of air, _{T A:} atmospheric temperature _{ΔT W = h W (T S} -T W) (5)
ΔT _W : Cooling temperature by water cooling h _W : Heat transfer coefficient of water cooling, T _W : Cooling water temperature By the way, these temperature estimated values are measurement errors due to actual measurement, wear of correction rolls, degree of cooling water, etc. It is also influenced greatly by the secular change. Therefore, these estimation equations are corrected based on the temperatures measured by the thermometer detectors 4 provided before and after the correction device 2. The correction equation is given by equation (6).
[0030]
T _L ^* = αΔT _R + ΔT _A + ΔT _W (6)
T _L ^* : the corrected temperature drop amount in the correction device, α: the adjustment coefficient adjustment coefficient α is obtained by equation (7).
[0031]
α = (t ₁ −t ₀ ) / (ΔT _L −ΔT _A −ΔT _W ) (7)
t ₀ : Straightening device inlet side temperature, t ₁ : Straightening device outlet temperature, and Equations (6) and (7) are corrections for heat removal from the straightening rolls, but as in Equations (8) and (9) In addition, an adjustment coefficient can be set for the temperature drop amount of the entire correction apparatus.
[0032]
T _L ^* = βΔT _L (8)
β = (t ₁ −t ₀ ) / ΔT _L (9)
β: If the adjustment coefficient obtained by the adjustment coefficient formula (6) or formula (9) is used, the error in the temperature estimation formula of the correction device can be corrected, and the secular change of the temperature drop amount can be corrected.
[0033]
The adjustment coefficient α or β obtained in this way is used for calculation when determining the heating power for the subsequent materials. Further, these adjustment factors are classified and stored for each thickness, width, and temperature increase amount of the steel material, and the subsequent materials can be used for steel materials having similar heating conditions.
[0034]
In the present embodiment, the temperature drop amount is obtained using an equation, but the present invention is not limited to this form, and the temperature drop amount may be obtained using an estimation model.
[0035]
In step S4, the heating temperature is calculated by equation (10).
[0036]
ΔT _H = T _ref −t ₀ + ΔT _L + ΔT _A (10)
ΔT _H : heating temperature, T _ref : target temperature, t ₀ : device entry side temperature ΔT _L : temperature drop at the straightening device, ΔT _A : air cooling temperature In step S5, an electric energy corresponding to the heating temperature is calculated.
[0037]
P _H = C _P ρVΔT _H / τ _H (11)
P _H : Heating power C _P : Specific heat, ρ: Density, V: Volume, ΔT _H : Heating temperature, τ _H : Heating time Supplying the amount of power determined by the procedure described above to the induction heating device, steel material Can be heated with high accuracy.
[0038]
FIG. 3 is a side view showing a schematic configuration of the heat treatment facility according to the second embodiment to which the heating method according to the present invention is applied. In 2nd Embodiment, the correction apparatus 2 is installed in the back | latter stage of the induction heating apparatus 1 on the heat processing line.
[0039]
Also in the second embodiment, the heating power can be obtained in the same manner as described above. That is, the electric power supplied to the induction heating device 1 is calculated using the equations (1) to (11) according to the procedures of steps S1 to S5 so that the temperature of the steel material 3 after the straightening device 2 becomes the target temperature. It ’s fine.
[0040]
FIG. 4 is a side view showing a schematic configuration of a heat treatment facility according to a third embodiment to which the heating method according to the present invention is applied. In 3rd Embodiment, the correction apparatus 2 is installed between the induction heating apparatuses on the heat processing line.
[0041]
Also in the second embodiment, the heating power can be obtained in the same manner as described above. That is, the electric power supplied to the induction heating device 1 is calculated using the equations (1) to (11) according to the procedures of steps S1 to S5 so that the temperature of the steel material 3 after the straightening device 2 becomes the target temperature. It ’s fine.
[0042]
Next, an application example of in-line heat treatment using the heat treatment facility shown in FIG. 1 will be described. In this embodiment, the induction heating device 1 has three solenoid induction heating devices arranged in series. And the steel material temperature before heat processing was 200 degreeC, and tempering heat processing was performed so that plate | board thickness center part might be 650 degreeC after heat processing. The upper limit of the steel material surface temperature was 700 ° C. below the Ac1 transformation point. The correction device 2 is used on the entrance side of the first pass and the entrance side of the third pass.
[0043]
FIG. 5 is a table showing operating conditions for realizing the above-described heat treatment. According to this operating condition, the temperature heated in all three passes of heat treatment is 540 ° C., while the temperature drop due to cooling is 90 ° C. Therefore, the temperature rises by 450 ° C.
[0044]
Here, the amount of temperature drop in the straightening device 2 was obtained from Equation (1), and the amount of temperature drop in each induction heating device 1 was calculated from Equation (4) as a temperature drop due to air cooling. In consideration of the capacity and efficiency of the induction heating apparatus 1, the fastest transport speed was selected among those capable of heating.
[0045]
The amount of electric power supplied to each induction heating device 1 obtained in this way is shown in a table in FIG. Furthermore, the temperature change of the steel material 3 at the time of giving and heating this electric power to FIG. 7 is represented with a graph. It is shown that the steel was heated to the original target temperature at the final induction heating device exit side.
[0046]
The above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed structural requirements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.
[0047]
【The invention's effect】
As described above, according to the present invention, when a heat treatment of a steel material is performed using an induction heating device, the steel material can be accurately heated to the target temperature, and the quality of the product can be ensured.
[Brief description of the drawings]
FIG. 1 is a side view showing a schematic configuration of a heat treatment facility according to a first embodiment to which a heating method according to the present invention is applied.
FIG. 2 is a flowchart showing a procedure for obtaining heating power supplied to the induction heating device.
FIG. 3 is a side view showing a schematic configuration of a heat treatment facility according to a second embodiment to which a heating method according to the present invention is applied.
FIG. 4 is a side view showing a schematic configuration of a heat treatment facility according to a third embodiment to which a heating method according to the present invention is applied.
The figure which shows the temperature distribution of steel materials.
FIG. 5 is a table showing operating conditions for realizing heat treatment.
FIG. 6 is a table showing the amount of power supplied to each induction heating device.
FIG. 7 is a view showing a temperature change of a steel material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Induction heating apparatus, 2 ... Straightening apparatus, 3 ... Steel materials, 4 ... Thermometer, 5 ... Roller for conveyance.

Claims (6)

After the installed correction device on the line and have at at least one induction heating device was passed through the straightening device, the heating method of heating the steel material by passing the induction heating device,
Based on information including the temperature of the steel material on the entry side of the straightening device and the conveyance speed of the steel material, a temperature drop amount estimation step for estimating the temperature drop amount of the steel material in the straightening device;
A method for heating a steel material, comprising: an electric power calculation step for calculating electric power supplied to the induction heating device for heating the steel material to a target temperature based on the estimated temperature drop amount. The descent amount estimation step includes:
Estimating a first temperature drop due to contact between the steel material and the straightening roll;
Estimating a second temperature drop due to heat dissipation from the steel to the atmosphere;
The method for heating a steel material according to claim 1, further comprising a step of estimating a third temperature drop due to water cooling of the steel material.   The estimated temperature of the steel material on the outlet side of the straightening device obtained from the estimated temperature drop of the steel material, and the measured temperature of the steel material on the outlet side of the straightening device measured with a thermometer provided on the outlet side of the straightening device The steel material heating method according to claim 1, further comprising a correction step of correcting the temperature drop amount estimation model of the steel material based on the above. The installed correction device on the line and have at at least one induction heating device, after having passed through the straightening device, the heat treatment program for heating the steel by passing the induction heating device,
On the computer,
Based on information including the temperature of the steel material on the entry side of the straightening device and the conveying speed of the steel material, a temperature drop amount estimation procedure for estimating the temperature drop amount of the steel material in the straightening device,
An electric power calculation procedure for calculating electric power supplied to the induction heating device for heating the steel material to a target temperature based on the estimated temperature drop amount,
A program for running The descent amount estimation procedure includes:
A procedure for estimating a first temperature drop due to contact between the steel material and the straightening roll;
A procedure for estimating a second temperature drop due to heat dissipation from the steel to the atmosphere;
The program according to claim 4 , further comprising a procedure for estimating a third temperature drop due to water cooling of the steel material. The estimated temperature of the steel material on the exit side of the straightening device obtained from the estimated temperature drop of the steel material, and the measured temperature of the steel material on the exit side of the straightening device measured with a thermometer provided on the exit side of the straightening device based on the bets, the program according to claim 4 or 5, further comprising a modification procedure to modify the temperature drop amount estimation model of the steel.

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