JP2004055265A - Constant electric power energization heating method of metal plate - Google Patents
Constant electric power energization heating method of metal plate Download PDFInfo
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- JP2004055265A JP2004055265A JP2002209502A JP2002209502A JP2004055265A JP 2004055265 A JP2004055265 A JP 2004055265A JP 2002209502 A JP2002209502 A JP 2002209502A JP 2002209502 A JP2002209502 A JP 2002209502A JP 2004055265 A JP2004055265 A JP 2004055265A
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- metal plate
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Abstract
Description
【0001】
【発明の属する技術分野】
本発明は、鋼板等の金属板を目標温度まで定電力で通電加熱する金属板の定電力通電加熱方法に関するものである。
【0002】
【従来の技術】
鋼板などの金属板を温間プレスするに際しては金属板を適当な温度に加熱する必要があり、そのために従来から通電加熱が広く用いられている。金属板の通電加熱に当たって、従来は作業者が金属板の寸法、目標温度、加熱時間等に応じて経験的に電力値を設定して金属板に供給していたので、最適な電力値を設定するまでに試行錯誤を要していた。また、金属板の寸法や材質が変更された場合にも、新たに最適な電力値を設定し直す必要があって、そのために加熱温度がばらついたりする問題があった。
【0003】
【発明が解決しようとする課題】
本発明は上記した従来の問題点を解決して、経験や試行錯誤に頼ることなく、金属板に定電力を通電して目標時間で目標温度まで精度よく昇温することができる金属板の定電力通電加熱方法を提供するためになされたものである。
【0004】
【課題を解決するための手段】
上記の課題を解決するためになされた本発明の金属板の定電力通電加熱方法は、金属板の比熱を温度の関数として近似し、この関数を用いて金属板に供給する電力と電力供給による金属板の温度上昇率との関係式を求め、この関係式から金属板を定電力通電により目標時間で目標温度まで昇温するに要する定電力の値を求め、この値の定電力を金属板に通電することを特徴とするものである。
【0005】
本発明の金属板の定電力通電加熱方法によれば、金属板を目標時間で目標温度まで昇温するに要する定電力の値を正確に求めることができるので、この値の定電力を金属板に供給することによって、金属板を目標温度にまで精度よく昇温することができる。このため金属板の材質や寸法が変更された場合にも、直ちに電力値を演算して適切な値に変更することができ、無駄が生ずることがない。
【0006】
【発明の実施の形態】
以下に本発明の好ましい実施形態を説明する。
図1は本発明を実施するための通電加熱装置の一例を示す概略図であって、電極1、1間に支持された金属板に電源装置2から電流が通電されて、ジュール熱で加熱される。本発明ではあらかじめ計算された一定電力が金属板に通電され、目標時間で目標温度にまで加熱される。このための定電力値の計算は以下のようにして行なう。
【0007】
本発明の金属板の定電力通電加熱方法においては、金属板の寸法と物性(比熱、比重)、目標温度、加熱時間から定電力の値を決定する。すなわち、金属板に供給される電力と金属板の比熱及び質量から電力と温度上昇率との関係式を求めて、この関係式により必要な定電力の値を演算して、この値の定電力を金属板に供給する。ここで、比熱は温度に依存して変化するので、演算に用いる比熱は温度の関数として近似したものを用いる必要がある。以下、鋼板を例に本発明における定電力値の演算方法を説明する。なお、以下の計算においては放射による抜熱は小さいので無視している。
【0008】
先ず、金属板の比熱Cを温度Tの関数として近似する。比熱の温度依存性は図2に示すとおりであって、この比熱C(J/kg・K)はC=pT+qの一次式で近似することができる。ここで、p=0.449、q=432である。
【0009】
そして、比熱Cの金属板に電力Pが供給されることによる昇温速度は、dT/dt=P/m*Cで与えられる。mは金属板の質量(kg)である。この式に比熱の関数を代入して、dT/dt=P/{(pT+q)m}}となる。この式の両辺を積分してtを求めると、数1の通りとなる。
【数1】
ここで、T0は昇温前の温度、T1はt時間昇温後の温度である。この式は金属板の比熱を温度の関数として近似したうえで、加熱時間を金属板の質量と供給された電力および目標温度から求めるものである。
【0010】
この式より電力Pは下記の数2の式で表すことができる。
【数2】
このようにして計算された定電力を金属板に所定時間tだけ通電すれば、金属板を目標温度にまで精度良く昇温することができる。なお、電源装置2に上記の演算式を記憶させたコンピュータを接続しておき、必要な項目を入力するだけで定電力値を求めることができるようにしておくことが好ましい。
【0011】
【実施例】
以下に説明した本発明の効果を確認するために、長さ0.2m、幅0.08m、厚さ0.0032mの鋼板に定電力を通電して3秒にて1000℃にまで通電加熱した。金属板の寸法、目標時間、目標温度から上記の式により演算した定電力の値は88.178KWであった。この値の電力を鋼板に通電したときの温度変化を図3に示すが、予定どおり3秒の通電加熱により鉄板を1000℃に昇温することができた。
【0012】
【発明の効果】
以上に説明したように、本発明の金属板の定電力通電加熱方法は、金属板の比熱を温度の関数として近似し、この関数を用いて金属板に供給する電力と電力供給による金属板の温度上昇率との関係式を求め、この関係式から金属板を目標時間で目標温度まで昇温するに要する定電力の値を正確に求めることができる。このため、この値の定電力を金属板に供給することによって、金属板を目標温度にまで精度よく昇温することができる。
したがって本発明によれば、金属板のサイズや品種が代わった場合にも、最適な定電力値を演算して通電することができるので、金属板の通電加熱を常に極めて高精度に行うことができる。
【図面の簡単な説明】
【図1】本発明に用いる通電加熱装置の概略図である。
【図2】比熱と温度との関係を示すグラフである。
【図3】定電力加熱による金属板の温度変化を示すグラフである。
【符号の説明】
1 電極
2 電源装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for heating a metal plate, such as a steel plate, to a target temperature with a constant power at a constant power.
[0002]
[Prior art]
When a metal plate such as a steel plate is warm-pressed, it is necessary to heat the metal plate to an appropriate temperature. For this reason, electric heating has been widely used. Conventionally, when conducting electric heating of a metal plate, the operator has to empirically set the power value according to the dimensions of the metal plate, the target temperature, the heating time, etc., and supply it to the metal plate, so the optimal power value is set It took trial and error to do so. In addition, even when the dimensions and the material of the metal plate are changed, it is necessary to newly set an optimum electric power value, so that there is a problem that the heating temperature varies.
[0003]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and allows a constant power supply to a metal plate to accurately raise the temperature to a target temperature in a target time without relying on experience or trial and error. The purpose of the present invention is to provide a power supply heating method.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the constant-power energizing and heating method for a metal plate according to the present invention approximates the specific heat of the metal plate as a function of temperature, and uses the power and the power supplied to the metal plate using this function. The relational expression with the temperature rise rate of the metal plate is obtained, and from this relational expression, the value of the constant power required to raise the temperature of the metal plate to the target temperature in the target time by applying constant power to the metal plate is obtained. Is supplied with electricity.
[0005]
According to the constant-power energizing and heating method for a metal plate of the present invention, the value of the constant power required to raise the temperature of the metal plate to the target temperature in the target time can be accurately obtained. , It is possible to accurately raise the temperature of the metal plate to the target temperature. Therefore, even when the material and dimensions of the metal plate are changed, the power value can be immediately calculated and changed to an appropriate value, and no waste occurs.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
FIG. 1 is a schematic view showing an example of an electric heating device for carrying out the present invention, in which a metal plate supported between
[0007]
In the method for heating a metal plate with constant electric power according to the present invention, the value of the constant power is determined from the dimensions and physical properties (specific heat and specific gravity) of the metal plate, the target temperature, and the heating time. That is, a relational expression between the electric power and the temperature rise rate is obtained from the specific heat and the mass of the electric power supplied to the metal plate and the metal plate, and a required constant power value is calculated according to the relational expression. Is supplied to a metal plate. Here, since the specific heat changes depending on the temperature, it is necessary to use the specific heat used for the calculation as an approximation as a function of the temperature. Hereinafter, a method of calculating a constant power value in the present invention will be described using a steel plate as an example. In the following calculations, heat removal due to radiation is small and is ignored.
[0008]
First, the specific heat C of the metal plate is approximated as a function of the temperature T. The temperature dependence of the specific heat is as shown in FIG. 2, and this specific heat C (J / kg · K) can be approximated by a linear expression of C = pT + q. Here, p = 0.449 and q = 432.
[0009]
Then, the rate of temperature rise by supplying the electric power P to the metal plate having the specific heat C is given by dT / dt = P / m * C. m is the mass (kg) of the metal plate. By substituting the function of the specific heat into this equation, dT / dt = P / {(pT + q) m}. When t is obtained by integrating both sides of this equation,
(Equation 1)
Here, T 0 is the temperature before the temperature is raised, and T 1 is the temperature after the temperature is raised for the time t. This equation approximates the specific heat of the metal plate as a function of temperature, and then determines the heating time from the mass of the metal plate, the supplied power, and the target temperature.
[0010]
From this equation, the power P can be expressed by the following equation (2).
(Equation 2)
If the constant power calculated in this way is applied to the metal plate for a predetermined time t, the temperature of the metal plate can be accurately raised to the target temperature. Note that it is preferable that a computer storing the above-described arithmetic expressions be connected to the
[0011]
【Example】
In order to confirm the effects of the present invention described below, a constant power was applied to a steel plate having a length of 0.2 m, a width of 0.08 m, and a thickness of 0.0032 m, and was heated to 1000 ° C. in 3 seconds. . The value of the constant power calculated by the above equation from the dimensions of the metal plate, the target time, and the target temperature was 88.178 KW. FIG. 3 shows a temperature change when the electric power of this value is applied to the steel sheet. The iron plate could be heated to 1000 ° C. by conducting the electric current for 3 seconds as expected.
[0012]
【The invention's effect】
As described above, the constant-power energizing and heating method for a metal plate of the present invention approximates the specific heat of the metal plate as a function of temperature, and uses this function to supply power to the metal plate and supply the metal plate with power. A relational expression with the temperature rise rate is obtained, and from this relational expression, the value of the constant power required to raise the temperature of the metal plate to the target temperature in the target time can be accurately obtained. Therefore, by supplying the constant power of this value to the metal plate, the temperature of the metal plate can be accurately raised to the target temperature.
Therefore, according to the present invention, even when the size and the type of the metal plate are changed, the optimum constant power value can be calculated and the power can be supplied. it can.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an electric heating device used in the present invention.
FIG. 2 is a graph showing a relationship between specific heat and temperature.
FIG. 3 is a graph showing a temperature change of a metal plate due to constant power heating.
[Explanation of symbols]
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JP2002209502A JP2004055265A (en) | 2002-07-18 | 2002-07-18 | Constant electric power energization heating method of metal plate |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2013077083A1 (en) | 2011-11-24 | 2013-05-30 | 本田技研工業株式会社 | Side panel structure for vehicle |
US10060017B2 (en) | 2009-08-06 | 2018-08-28 | Nippon Steel & Sumitomo Metal Corporation | Metal sheet to be heated by radiant heat transfer and method of manufacturing the same, and metal processed product having portion with different strength and method of manufacturing the same |
JP2020017354A (en) * | 2018-07-23 | 2020-01-30 | 中央発條株式会社 | Heating device and heating method |
-
2002
- 2002-07-18 JP JP2002209502A patent/JP2004055265A/en active Pending
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10060017B2 (en) | 2009-08-06 | 2018-08-28 | Nippon Steel & Sumitomo Metal Corporation | Metal sheet to be heated by radiant heat transfer and method of manufacturing the same, and metal processed product having portion with different strength and method of manufacturing the same |
WO2013077083A1 (en) | 2011-11-24 | 2013-05-30 | 本田技研工業株式会社 | Side panel structure for vehicle |
US20140319877A1 (en) * | 2011-11-24 | 2014-10-30 | Honda Motor Co., Ltd. | Side panel structure for vehicle |
US9452786B2 (en) * | 2011-11-24 | 2016-09-27 | Honda Motor Co., Ltd. | Side panel structure for vehicle |
JP2020017354A (en) * | 2018-07-23 | 2020-01-30 | 中央発條株式会社 | Heating device and heating method |
JP7111543B2 (en) | 2018-07-23 | 2022-08-02 | 中央発條株式会社 | Heating device and heating method |
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