JPS6131949B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an induction heating control method for heating a moving pipe to a constant temperature. Many induction heating control methods and devices have been published for uniformly heating a long metal material such as a pipe while moving it in its longitudinal direction. For example,
No. 13674 discloses a uniform heating method with improved two-position control of the heating power source. Also, JP-A-52-
No. 122941, JP-A-52-122942 and JP-A-52-
Japanese Patent No. 122943 discloses a control device for controlling the amount of power supplied to a heating induction coil. However, in these known electric induction heating controls, the temperature of the heated material is detected and the amount of power supplied to the heating induction coil is controlled until the temperature reaches a predetermined temperature, and control is not performed within the same heated material. Ru. In these known induction heating controls, the amount of control given is uncertain, and control is continued based on the measured temperature of the heated material exiting the heating induction coil during the control process. Furthermore, in the case of induction heating, since the temperature was controlled within the same heated material, the control was simple, and the control accuracy seemed to be lacking. The present invention reduces the dispersion in the heating temperature increase between each heated material when giving a fixed temperature increase to each of the many heated materials that are sequentially sent to the heating inductor coil. The purpose is to keep the amount of temperature rise to a constant value. In order to achieve the above object, in the present invention, in induction heating using an inductor coil of a large number of materials to be heated belonging to one group such as for each lot division,
Find the difference between the pre-heating temperature and the post-heating temperature of the heated materials in the one group that have already been heated by the inductor coil, that is, the deviation between the actual temperature increase amount and the target temperature increase amount, and respond to this temperature increase amount deviation. The first correction amount is the increment of the operation amount multiplied by a predetermined adjustment gain, and the total operation amount that was output to heat the previous material to be heated with the inductor coil is calculated from the tip to the tail of the material to be heated. The average value of these values is obtained by grasping in an arbitrary section up to the end, and the second correction amount is obtained by multiplying the difference between this average value and the previous initial setting operation amount by a predetermined correction gain. The second correction amount or the first
The heating control operation amount is determined by adding the sum of the correction amount and the second correction amount, or the heating control operation amount is uniformly determined for each of all the heated materials in the above-mentioned one group. When the initial setting operation amount is determined for the heating material, the average value of the wall thickness of the steel pipe to be heated within one pipe is calculated, and the difference between the average wall thickness value and the separately determined wall thickness reference value, that is, the wall thickness Multiply the thickness deviation by a predetermined wall thickness correction gain to obtain the correction amount due to wall thickness, and add this correction amount due to wall thickness to the initial setting operation amount assigned in advance to the current material to be heated. The setting correction amount is The disturbance that causes fluctuations in the amount of temperature increase for each heated material consists of two components: a component that slowly changes in relation to each successive heated material (hereinafter referred to as a periodic component), and a component that slowly changes in relation to each successive heated material. It can be divided into a component (hereinafter referred to as an aperiodic component) that fluctuates independently of each other in each material. In order to prevent fluctuations in the amount of temperature increase caused by periodic components of disturbance, the initial setting operation amount is the first correction amount and the initial setting operation amount for the material to be heated that was previously heated by the inductor coil. It is preferable to determine it by adding a second correction amount,
In this case, when determining the first correction amount, it is preferable that the temperature increase amount deviation is a smoothed value of the temperature increase amount deviation of the plurality of heated materials that have already been heated, in order to smoothly correspond to the periodic component. This smoothing method uses the simple average method, weighted average method, exponential smoothing method, or other smoothing methods. Preferably, a smoothing method is used. In addition, the adjustment gain used in determining the first correction amount is such that the deviation in the amount of temperature increase that has occurred in the already heated material to be heated is dispersed and removed among two or more materials to be heated next. This is to prevent the control from becoming unstable due to sudden changes in the manipulated variable for each line, and it is desirable to give a value between 0 and 1. The second correction amount is determined by incorporating into the current operation amount setting the difference between the total operation amount that was output for heating the heated material last time and the previous initial setting operation amount that is the standard for correction. This is effective in smoothly responding to the periodic component of disturbance and reducing the variation in the amount of temperature increase for each wire. Here, the total manipulated variable is equal to the set manipulated variable according to the present invention, or when the control according to the present invention is combined with heating control that outputs so that the temperature of each part within one heated material is constant. is the operation amount correction amount by this heating control plus the setting operation amount. In the latter case, the total amount of operation changes within one tube, so it is necessary to take the average within one tube, but in this case, the average value should be calculated in the unsteady area of the heated material, especially between 200 mm and 1000 mm at the tip and tail end. It is desirable to obtain the temperature in an interval other than , and it is preferable to use the same temperature average interval when determining the temperature before heating and the temperature after heating when determining the first correction amount.
In addition, the correction gain used in determining the second correction amount is the average value of the operation amount correction amount by heating control of each part of the heated material heated last time.
This is to prevent the control from becoming unstable due to sudden changes in the amount of operation for each heated material due to dispersion over more than one heated material, and it is desirable to give a value between 0 and 1. . Next, in order to prevent fluctuations in the amount of temperature increase caused by a periodic component of the disturbance that changes relatively quickly and a non-periodic component of the disturbance, in the present invention, the set operation amount is 1 of the material to be heated
The initial setting operation amount is corrected and determined based on the difference between the wall thickness average value and the wall thickness reference value in the book, that is, the wall thickness deviation. This is based on the knowledge that the main cause of disturbance that changes the amount of temperature rise is the variation in the average wall thickness from one piece to another, and that by removing this, the variation in the amount of temperature rise can be greatly reduced. . Naturally, the periodic component of the disturbance includes a large amount due to fluctuations in the wall thickness average value, and even if the initial setting operation amount is uniformly determined within one heating group, the method according to the present invention can control the It has an effect. When determining the amount of correction based on wall thickness, the average wall thickness value can be determined by measuring the wall thickness at a representative point on the entire surface of the pipe and calculating the average value. There are methods such as measuring the length and outer diameter and calculating from them, but any method may be used. In addition, the wall thickness reference value is a wall thickness value corresponding to the initial setting operation amount, and when determining the initial setting operation amount uniformly, the wall thickness value that was used as the reference when it was obtained is used as the wall thickness value, and the initial setting operation amount is is the first correction amount and/
Alternatively, if the second correction amount is determined by successive additions, it is changed accordingly. For example, when using the first correction amount and calculating the temperature increase deviation by smoothing, the same smoothing method is applied to the average wall thickness of each material to be heated, and the smoothed value is used as the wall thickness reference value. Bye. Further, the wall thickness correction gain converts the wall thickness deviation into a change in the manipulated variable, and depends mainly on the outer diameter, and may be determined in advance for each outer diameter. In the heating control method of the present invention, the operating amount of the first heating supply power is set for each lot based on the size and specification of the material to be heated. The operation amount of the second heating supply power is set for each heated material based on the actual temperature increase of the heated material, and furthermore, in the heating control of each part of each heated material, the heating of each part is Heating each part based on the correspondence between the previous temperature and the temperature increase target value, and/or
Three-stage heating setting or heating control that controls the heating of the remaining parts based on the deviation of the already heated parts increases the temperature of the entire lot, each material to be heated, and each part of each material to be heated by a constant amount. It is particularly suitable for use as a part of heating control (setting of the manipulated variable of the second heating supply power). FIG. 1 shows an exemplary configuration of an apparatus for implementing the present invention. In FIG. 1, 1 ₁ , 1 ₂ and 1 ₃ are heating inductor coils, and the pipe 3 which is the material to be heated
are arranged along the transfer route 2. 4 ₁ ~ 4
₆ is a temperature detector, and detectors 4 ₁ , 4 ₃ and 4 ₅ are inductor coils 1 ₁ , 1 ₂ and 1 respectively.
₃ , the temperature T of the arriving heated material 3
_i1 , T _i2 and T _i3 , and the detectors 4 ₂ , 4 ₄ and 4 ₆ are respectively inductor coils 1
The temperatures T _p1 , _{T p2} , _and T _p3 of the heated material 3 are detected on the outlet sides of the heated materials 1 , 1 ₂ , and 1 3 . These temperature detectors 4 ₁ to 4 ₆ may be of almost any type, but radiation thermometers are usually used. When multiple sensors are installed in the circumferential direction of the pipe, the average value of their detected temperatures is used. In this embodiment, the first inductor coil ₁₁ has a constant temperature in order to always heat the outlet temperature T _p1 to a constant target temperature T ₁ despite the variation of the inlet temperature T _i1 . The second inductor coil ₁₂ is arranged for temperature heating, and the second inductor coil 12 is used for constant temperature rise heating to give a predetermined temperature rise (T ₂ −T ₁ ) to the inlet temperature T _i2 . The inductor coils 1 _{to 3} also have an inlet temperature T
It is used for constant temperature rise heating that gives a predetermined temperature rise (T ₃ - T ₂ ) to _i3 . Correspondingly, a heating control circuit that controls the heating power of each of the inductor coils 1 ₁ to 1 ₃ has almost the same configuration, but a heating control circuit that controls the heating power of the first inductor coil 1 ₁ for constant temperature heating. The control circuit uses the difference between the inlet temperature T _in1 and the target temperature T ₁ (T ₁ - _{T in1} ) as one input quantity, while the second and third inductor coils for constant temperature rise heating Heating control circuits ₁₂ and ₁₃ each use the set temperature increase amounts ( _T2 - _T1 ) and ( _T3 - _T2 ) as one input amount. The heating control circuit receives an electrical signal representing the inlet temperature T _i1 continuously or at intervals, and outputs a signal representing a time series average value T _in1 of T _i1 .
Average value calculation circuit 5 ₁ consisting of an integrating circuit with a predetermined time constant, etc. Average value calculation circuit 5 ₂ having a similar configuration and outputting a signal representing the average value _pn1 of the outlet temperature T _p1 ; Target temperature setting device A signal representing the target temperature T ₁ from 6 ₁ (for example, a potentiometer) and an average value T of the inlet temperature from the average value calculation circuit 5 ₁
Temperature increase target value setting circuit 7, which is composed of an operational amplifier, a differential amplifier, etc., receives a signal representing T _in1 as an input, and outputs a signal representing a temperature difference of (T ₁ - T _in1 ).
₁ ; With the signals representing T _in1 and T _pn1 from the average value calculation circuits ₅₁ and ₅₂ as inputs, and the signal representing (T ₁ −T _in1 ) from the setting circuit ₇₁ , (T _pn1 −T _in1 ) − (T ₁ − T _in1 ), that is, the actual average temperature increase amount (T _pn1 − T _in
1 ) A temperature rise amount deviation calculation circuit 8 ₁ composed of an operational amplifier etc. outputs a signal representing the deviation from the target temperature rise amount (T ₁ −T _in1 ); the output deviation signal of the calculation circuit 8 ₁ is Smoothing circuit 12 ₁ that smooths over two or more heated materials, for example, several pieces; This smoothing value is multiplied by the unit operation amount (operation amount required to change the amount of temperature increase by 1°C) and the adjustment gain to calculate the electric power. A first correction amount calculation circuit 9 ₁ consisting of an operational amplifier, a function generator, etc., which converts the control operation amount change (first correction amount) into a signal representing the control operation amount change (first correction amount); A manipulated variable calculation circuit 10 ₁ consisting of an operational amplifier, etc., which outputs the current initial setting manipulated variable by adding the first correction amount and the second correction amount; the pipe inlet temperature and its target temperature that change every moment In-line control circuit 13 ₁ that outputs the manipulated variable correction amount in response to the difference between 14 ₁ ; Inputs the total manipulated variables that change moment by moment, and outputs the average value of all manipulated variables, 5 ₁ , 5
Average value calculation circuit 15 ₁ having the same configuration as ₂ ; a second correction amount that calculates the difference between the total operation amount average value and the initial setting operation amount, multiplies this by a predetermined correction gain, and outputs a second correction amount. Arithmetic circuit 16 ₁ ; Wall thickness average value measurement circuit 17 that measures, calculates and outputs the wall thickness average value for each object to be heated; and sequentially inputs the wall thickness average value to obtain a wall thickness standard value, Find the difference between the average value and the wall thickness reference value, multiply it by a predetermined wall thickness correction gain to find the correction amount due to wall thickness, add the initial setting operation amount to it, and calculate the current setting operation amount (this is the power supply control device It is composed of a wall thickness correction calculation circuit ₁₈₁ which outputs a signal (input to ₁₁₁ ). In this heating control circuit, the temperature T _in1 on the inlet side of the first inductor coil 1 ₁ and the target temperature T ₁ are input to the temperature increase target value setting circuit 7 ₁ , so that (T ₁ −T _in1 ) becomes the target temperature increase amount, and therefore, even if the temperature T _i1 on the input side of the heated material 3 varies, heating control is performed to set the temperature on the output side as the target value T ₁ . In the heating control circuit, signals representing the first and second target temperatures _T1 and _T2 are sent from target temperature setting devices ₆₂ and ₆₃ such as potentiometers to the temperature increase target value setting circuit ₇₂ . is applied. Therefore, the heating control circuit sets the target temperature increase amount to a fixed amount (T ₂ −T ₁ ). Therefore,
The heating control circuit performs constant temperature increase control so that even if the temperature T _i2 on the inlet side fluctuates, the temperature on the outlet side is always T _i2 +(T ₂ −T ₁ ). The heating control circuit also performs constant temperature rise control in the same way. In addition, in FIG. 1, the target temperature setters 6 ₂ , 6 ₃ , 6 ₄ and 6 ₅ are shown to output signals representing the target temperatures T ₁ , T ₂ , T ₂ and T ₃ respectively, but This is tentatively displayed on the assumption that T _p1 = T _i2 = T ₁ and T _p2 = T _i3 = T ₂ , and each of these target temperature setters 6 ₂ to 6 ₅ is It may be set to output a signal indicating a predetermined target temperature. Because the second inductor coil 1
₂ , it is sufficient to heat the first inductor coil ₁₁ by adding a predetermined temperature increase amount T _p1 (T _p1 = T ₂ - T ₁ in the figure) to the heating temperature (T ₁ ) of the first inductor coil 11, and In the third inductor coil ₁₃ , _a predetermined temperature increase amount T _p2 ( _{T p2 =} T ₃ − _{T 2} ) can be added and heated. In the embodiment shown in FIG. 1, the final target temperature is T ₁ +T _p1 +T _p2 . In addition, it is T ₃ in the illustration, and T ₃ = T ₁ + T _p1 +
The relationship becomes T _p2 . However, the above assumes that the heated material 3 is not cooled while running between the first inductor coil 1 and the second inductor coil, and between the second inductor coil and the third inductor coil. This is the case. The influence of cooling can be compensated for by adjusting the set values of the target temperature setters 6 ₁ - 6 ₅ . Next, to explain in more detail the functions of each of the above-mentioned components, the pipe tracking circuit ₁₄₁ detects the arrival of the tip and tail ends of the pipe, and detects the arrival of the tail end of the pipe, and detects the arrival of the tail end of the pipe, and detects the arrival of the tail end of the pipe. It issues a signal and instructs the average value calculation circuits 5 ₁ , 5 ₂ and 15 ₁ in the averaging period (sampling period), and also instructs the internal control circuit 13 ₁ to control the tube end control timing and the temperature rise of each part in the center of the tube. Instructs the calculation timing for correcting the manipulated variable based on the amount deviation. The internal control circuit 13 ₁ is a control circuit for eliminating temperature fluctuations in the length direction within one pipe, and for example, inputs the inlet temperature and calculates the deviation from the target value.
These include a feed-forward control circuit that calculates the manipulated variable correction amount by multiplying the deviation by a certain coefficient, or a pattern control circuit that outputs the manipulated variable correction amount in a fixed pattern at both ends of a pipe. The output value of these changes within one line. The average value calculation circuits 5 ₁ , 5 ₂ and 15 ₁ respectively receive the temperature detection value and the operation amount correction amount of each coil as signals in the interval designated by the pipe tracking circuit 14 ₁ and calculate the average value thereof. A good method for averaging is simple averaging, which is obtained by taking the integration (or integration) of the signals in the section and dividing it by the number of integrations (or integration time). The maximum average section is from the tip to the tail end of the pipe, but it is desirable to exclude unsteady parts (200 to 1000 mm) at both ends. Temperature increase target value setting circuit 7 ₁ uses the average inlet temperature value T _in1 (of the previous heated material) and calculates the difference from the target temperature T ₁ θ*=T ₁ −T _in1 = target temperature increase amount Outputs a signal representing . On the other hand, the circuit
, _... output a signal representing θ*=T ₂ −T ₁ =target temperature increase amount. The temperature increase amount deviation calculation circuit ₈₁ calculates the average temperature increase value θ _n =T _pn1 −T _in1 , and further calculates the target temperature increase amount θ* and the average temperature increase value θ _n
From this, the temperature increase deviation Δθ=θ _n −θ* is determined, and a signal representing this is output. First correction amount calculation circuit 9 ₁ and smoothing circuit 12 ₁
In this example, as a method of reflecting the temperature increase deviation of the past two or more times in the first correction amount, the temperature increase deviation is obtained by exponential smoothing method, and a predetermined coefficient is applied to this as shown below. The second correction amount was determined by the remainder. This method can be expressed as an arithmetic expression as follows. =αΔθ(1-α)′ ; Smoothed value of temperature increase deviation ′ = Smoothed value of previous temperature increase deviation Δθ; Said temperature increase deviation α; Exponential smoothing coefficient 0<α<1 ΔV ₁ = −a ₁ a ₂ ΔV ₁ ; first correction amount a ₁ = unit operation amount a ₂ = adjustment gain In these equations, a ₁ is the increase/decrease in the operation amount required to increase or decrease the temperature increase amount by 1°C; It changes depending on the pipe size and other operating conditions, and can be set in advance. Therefore, a ₁ is the increment in the amount of operation necessary to increase the amount of temperature rise. Next, a ₂ is intended to prevent the control from becoming unstable due to drastic changes in the manipulated variable due to trying to remove the entire deviation with only the material to be heated this time. Gives a value between 0 and 1. Here, both α and _a2 are adjusted as appropriate depending on the nature of the disturbance in the target process. As a method of determining the first correction amount, in addition to this embodiment, there is also a method as shown in the following equation. This corresponds to a method usually called proportional-integral control. ΔV ₁ = c ₁ (Δθ − Δθ′) + c ₂ Δθ c ₁ , c ₂ ; Constants set appropriately In either of these methods, the deviation of the amount of heating that has already been heated from the first to the previous time in the same group is Everything is reflected in the initial setting operation amount, and fluctuations in the amount of temperature rise are stably and effectively reduced in response to gradual changes in disturbance. The second correction amount calculation circuit ₁₆₁ calculates the second correction amount ΔV ₂ from the total operation amount average value V _T and the previous initial setting operation amount V _p ' using the following equation. ΔV ₂ = b (V _T −V _p ′) b: Correction gain, 0<b≦1 The amount of heat added to the material to be heated is determined by the set operation amount V _S , or if there is heating control for each part. is the total manipulated variable V _T which is the sum of V _S and the manipulated variable correction amount V _D which is its output. The temperature increase amount deviation Δθ occurs because there is a discrepancy between this V _T and the truly necessary operation amount. However, since the previous initial setting operation amount V _p ' is added to the first correction amount ΔV ₁ obtained from Δθ, it is necessary to separately consider the amount V _T -V _p '. However, V _T −V _p ′
is the value for the previous heated material, so in the same way as when calculating the first correction amount, only a part of the operation amount corresponding to the temperature increase amount deviation was used, V _T −V _p ' is changed by 1. It is multiplied by a small correction gain b, and one part is used for correction. By doing so, fluctuations in the amount of temperature increase can be stably and effectively reduced in response to gradual changes in disturbance. Here, the value of b corresponds to the fact that when calculating the first correction amount, the previous temperature increase deviation Δθ was first exponentially smoothed by the smoothing coefficient α, and then further multiplied by the adjustment gain _a2 , and b= It is appropriate to set α・a ₂ . The operation amount calculation circuit 10 ₁ is a first correction amount (Δ
V ₁ ) and the second correction amount (ΔV ₂ ) are input, and the initial setting manipulated variable (V _p ) is calculated and output using the following arithmetic expression. V _p =V _p ′+ΔV ₁ +ΔV ₂ V _p ′: Previous initial setting operation amount The wall thickness average value measuring device 17 includes a weighing machine, a length meter,
Consists of an outer diameter meter and a calculation circuit, and outputs the average wall thickness value. A weighing machine, a length meter, and an outer diameter meter are known measuring instruments, and each measures the weight (W), length (L), and outer diameter (D) of each pipe.
The arithmetic circuit calculates the average wall thickness t based on the following formula: W=π×γ・L・(D−t)・t γ: Based on the density of the material of the pipe. A method other than the above-mentioned method may be used to obtain the average wall thickness value t. For example, there is a method of running an ultrasonic thickness gauge spirally over the outer surface of a steel pipe to measure the wall thickness at regular intervals, and then averaging the measured values to obtain the average wall thickness. Thickness correction calculation circuit 18 ₁ is the initial setting operation amount V _p
and wall thickness average value t as input, and outputs the set operation amount V _S . First, a wall thickness smooth value is determined from the wall thickness average value t using the following equation. =βt+(1-β)': Previous thickness smoothed value β: Smoothing coefficient Here, the smoothing constant β is the same value as the smoothing constant α of exponential smoothing used when calculating the first correction amount. . This is to ensure that the wall thickness smoothing value obtained in this manner corresponds to the initial setting operation amount. Therefore, next time the current wall thickness value t differs from the previous wall thickness smoothed value ', the initial setting operation amount V _p is corrected and the setting operation amount V _S is determined. V _S =V _p (1+K-t-t'/t'θ K: Thickness correction gain Next, an example will be explained. Inner diameter 370 mm, rated voltage
In the second stage coil ₁₂ of 1000V, coil capacity 1200KW, coil length 700mm, and oscillation frequency 330Hz, the material to be heated is a pipe with an outer diameter of 244.5mm and a wall thickness of 11.3mm, and the temperature increase target value T ₂ - T ₁ is , 120℃ (T ₂ = 280
℃, T ₁ = 160℃). Also, smoothing coefficient of temperature rise amount deviation (α) 0.6 Unit operation amount (a ₁ ) 1.2 Adjustment gain (a ₂ ) 0.7 Correction gain (b) 0.42 Smoothing coefficient of wall thickness (β) 0.6 Wall thickness correction gain (K) Each coefficient was set at 0.7. The calculation for determining the set operation amount V _S for the fourth pipe at this time is shown below. In addition, when heating the third pipe, the initial setting operation amount (V _p ') is 512V, the average value of the total operation amount (V _T ) is 511V, the average value of the inlet temperature is 161℃, the average value of the outlet temperature is 279℃, and

【table】 From the above

[Table] Setting operation amount for the 4th pipe using the calculation
508V was obtained. Figure 2 shows an example of numerical calculation and the actual values of the initial setting operation amount, set operation amount, average value of all operation amounts, and average value of temperature increase for the 2nd stage coil ₁₂ from the 1st to the 20th coil in the same lot. shows. The average wall thickness value is also listed. From this, we can see that the initial initial setting operation amount (the value is predetermined for each lot) of 500V was about 20V smaller than the appropriate value, but it quickly recovered, and that although there were fluctuations in the wall thickness value, it was set to this value. It can be seen that by following the manipulated variables, the temperature increase amount deviations are controlled to be small except for the first one. If it were not controlled, it can be estimated that the variation in temperature increase deviation would be about ±10°C, but it can be seen that the effect of control is significant. In addition, in FIG. 1, a configuration is shown in which the average of the inlet temperature T _i1 and the average of the outlet temperature T _p1 are first determined and the amount of temperature increase is determined from these values.
The difference between _{the 1} and 4 ₂ signals may be first determined, and then the average value may be taken. Further, in FIG. 1, the No. 1 coil is used for constant temperature heating and the coils after No. 2 are used for constant temperature heating, but a plurality of arbitrary coils may be used for constant temperature heating. In addition, in FIG. 1, the temperature detectors 4 ₂ and _{4 3} may be used in common _;
may also be shared as one item. At this time, the average value calculation circuits ₅₂ and ₅₃ become one common circuit.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an example of an electric induction heating device that embodies the present invention, and Fig. 2 is a graph showing the relationship between the voltage applied to the inductor coil and the amount of temperature rise when the present invention is implemented. It is. 1 ₁ to 1 ₃ : inductor coil, 2: transfer path,
3: Heated material, 4 ₁ - 4 ₆ : Temperature detector, 6 ₁ -
6 ₅ : Target temperature setting device, 7 ₁ , 7 ₂ : Temperature increase amount target value setting circuit.

Claims (1)

[Claims] 1. In heating each heated material to a constant temperature increase by passing many heated materials through an inductor coil in sequence, the average value of the wall thickness of the steel pipes to be heated is determined within one pipe. , the difference between the wall thickness average value and a separately determined wall thickness standard value, that is, the wall thickness deviation, is multiplied by a predetermined wall thickness correction gain to obtain the correction amount due to wall thickness, and the amount of correction due to wall thickness is determined, and the amount of correction due to wall thickness is determined. A pipe induction heating control method characterized by adding a correction amount based on the wall thickness to an initial setting operation amount to obtain a set operation amount for the current material to be heated. 2. Find the average value of the initial setting operation amount for each heated material in any section from the tip to the tail end of the heated material of all the manipulated variables that were output to heat the heated material last time, and calculate this average value. The difference between the value and the previous initial setting operation amount is multiplied by a predetermined correction gain, and the pre-correction setting operation amount assigned in advance to the current heated material is added. 1
A method for controlling induction heating of a pipe as described in . 3 Calculate the pre-correction setting operation amount for each heated material by calculating the difference between the pre-heating temperature and post-heating temperature of the heated material that has already been heated by the inductor coil, that is, the deviation between the actual temperature increase amount and the target temperature increase amount. Claim 2, wherein the initial setting operation amount for the heated material is added with a correction operation amount obtained by multiplying the operation amount change corresponding to the temperature increase amount deviation by a predetermined adjustment gain. Induction heating control method for pipes.