JPS63317621A - Electrical heating method - Google Patents

Abstract

PURPOSE:To avert generation of an arc between electrodes and a material to be heated by detecting the contact resistance between the electrodes and the material to be heated and controlling the energizing current value from the relation between the preset current density at the energizing parts of the electrodes and the contact resistance. CONSTITUTION:The electrodes 2 are pressed to both ends of the steel material 1 to be heated by the actuation of a cylinder 3 and are energized from a power supply 7 to heat the steel material 1. The voltage drop quantity signal from voltage detector 6-1, 6-2, the energizing current from a current detecting part 8, the area of the contact part of the steel material 1 to be heated with the electrodes 2, and the temps. near the contact part and the central part of the steel material from temp. detectors 5-1-5-3 are inputted to an energization controller 9. The controller 9 in the above-mentioned constitution outputs a control signal to the cylinder 3 or a power regulator 7' by the relation between the preset current density in the energizing parts of the electrodes by the steel material 1 to be heated and the contact resistance or the value obtd. by multiplying the contact resistance by the apparent area of the contact area. The generation of the arc in the contact part is thereby prevented and the deformation of the steel material 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electrical heating method, for example, slag generation,
This invention relates to an electrical heating method for steel materials such as electric steel and SUS, which require uniform oxidation-free heating due to yield and quality issues.

(Prior art) In a method that has a movable electrode and presses the electrode against the steel material to be heated, the contact resistance is low because the contact between the end surface of the steel material and the electrode is spot-like. is large, and therefore the current flows only through spot contact areas with small areas, causing arcs to occur at the contact areas and damaging the electrodes.

In particular, when a maximum current value or iti close to the maximum current value is applied from the start of heating in order to shorten the heating time, there is a problem in that arcing is particularly severe and the electrodes are significantly damaged.

Conventionally, by pressing an electrode against the steel material and increasing the current over time, the contact condition between the end surface of the steel material and the electrode is improved, in other words, the contact resistance is reduced, and arc heating is performed while avoiding arcing. ing.

Furthermore, for example, in Japanese Patent Application Laid-open No. 50-70946, when heating starts, the electrode is pressed against the steel material with a strong force to avoid arcing between the steel material and the electrode, and after the required heating, the pressing force is reduced. We are proposing a method to prevent plastic deformation of steel materials.

(Problems to be Solved by the Invention) However, in electric pressing, even if the force is the same, the contact state differs depending on the profile of the end face of the copper material, and if the contact state is poor, the electrodes will be damaged by arcing.

Moreover, if the pressing force is strong when the heated steel material reaches a high temperature, the steel material may be deformed.

Since the condition of the end face of the steel material differs depending on the individual steel material, the method of controlling the pressing force relative to the amount of energization has not been able to fundamentally solve the problems of electrode damage and deformation of the steel material due to arcing.

The present invention solves the above-mentioned conventional problems, and avoids the arc generated between the electrode and the steel material to be heated in the electrical heating method of the steel material, such as electromagnetic steel or SUS steel.
The present invention also provides an electrical heating method that prevents deformation of a material to be heated due to pressing.

(Means for Solving Problems) The gist of the present invention is to detect the contact resistance between the electrode and the heated material in a method in which a movable electrode is brought into contact with the heated material and pressed and heated with electricity. There is an energization heating method characterized in that the current value is controlled based on the relationship between the current density of the electrode current-carrying part and the contact resistance or the apparent contact resistance multiplied by the area of the contact part for a set type of material to be heated. .

Next, ii! according to the method of the present invention! Explain about electric heating.

In the present invention, when the electrode and the material to be heated are pressed together, the contact resistance is detected, so the voltage drop amount ΔV (V) and the current flowing current 1 (A) or the current flowing current ! (A) Apparent current density J (A/a) divided by contact area S (aJ)
j) is detected, and the contact resistance R (Ω) or the contact resistance multiplied by the apparent contact area RXS (Ω・cll
).

R(Ω)-ΔV(V)/I(A)-11-1) or R-3(Ω・-)-ΔV(V)/J(A/ad
)・-・・-(1-2) In this way, the contact resistance R (Ω) or RXS (Ω・i
), that is, while understanding the state of contact between the electrode and the material to be heated, adjust the current density J (A/d) of the current-carrying part and heat it with electricity.There will be no arcing between the electrode and the material to be heated, and the The heating material can also be heated without being deformed.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, numeral 1 indicates a material to be heated, for example, a steel material. 2.
Reference numerals 2' denote electrodes that are pressed against both ends of the steel material 1 to be heated, and the respective pressing electrodes are connected to a force adjusting device, for example a cylinder 3, via a piston rod 4, so that they can come into contact with the end surface of the steel material 1 to be heated and can be detached. It is.

By this operation of the cylinder 3, the force of pressing the electrode 2 against the end face of the heated steel material 1 is adjusted in ms. 5-1, 5-2
．． 5-3 is a temperature detector, 5-1.5-2 is installed near the end surface of the electrode for measuring the temperature near the contact part,
5-3 is installed so as to be able to measure the temperature at the longitudinal center of the heated steel material.

In addition, 6-1.6-2 is the voltage drop amount ΔV (V
), and is installed near the end face of the heated steel material and at parts A and B, respectively, so that the voltage drop between the parts can be measured.

In this case, it is possible to measure either one of the parts A and B without measuring them individually, or to measure the voltage between the electrodes 2 and 2', and determine the temperature in the steel material from the temperature T6 of the heated steel material 1 and the current value I. The amount of voltage drop at the contact portion may be determined by calculating the amount of voltage drop.

7 is a power supply, and 8 is a current detector that detects the current flowing. Reference numeral 9 denotes an energization control device, which receives a voltage drop amount ΔV (V) signal from a voltage detector 6-1, 6-2, a energization current I (A) from a current detector 8, and separately contacts the electrode of the steel material 1 to be heated. Partial area S (cod) is input.

The energization control device 9 is based on the calculation formula (1-1) or (1
-2), and the contact resistance R between the electrode 2 and the heated preparation material 1 is
(Ω) or R, which is the contact resistance multiplied by the contact area
Find -3(Ω・d).

Next, the steel material to be heated is determined in advance by type, for example, electromagnetic steel, S
The current-carrying part of the electrode made of US steel (stainless steel), ordinary steel, Ti steel, etc. is connected to the fluidized layer J (A/cd) and the contact resistance R (Ω).
Alternatively, the apparent contact resistance multiplied by the contact area is R-3 (
According to the relationship shown by the line in Figure 2 with Ω・d), the contact resistance R (Ω) or the apparent contact resistance per contact area is
・Electrode current density J (
When the electrode 1 is pressed, a control signal of A/an is outputted to the force adjusting device 3 or the power regulator 7'.C in the figure indicates the arc generation limit.

When electrically heated in this way, the electrode 2 and the steel to be heated 1
No arc is generated between the electrodes 2, and the heated steel material 1 is prevented from being damaged and deformed.

Note that temperature detection of To, T+, and Tz is not essential.

(Example) Current density J (A
, 'rito, contact resistance R (Ω) x apparent contact area 5
(-), the presence or absence of arcing at the contact area was investigated.

The results are shown in FIG. 2, and it can be clearly distinguished that there is a certain relationship between the electrode current density J and the contact resistance RXS per contact area as a boundary.

Based on the above relationship set in advance, the current value was controlled according to the detected contact resistance, and 1ffi electric heating of SUS steel was carried out, but there was no arcing at the contact area as shown by the O mark. The lifespan of the electrode has been significantly extended from the conventional 10 to 15 heats to 90 to 120 heats.

In addition, by detecting the contact resistance of the pressing force, we were able to minimize the necessary force and significantly suppress the deformation of the steel material.

The effects of the present invention have also been obtained with steel materials such as ordinary steel and electromagnetic steel.

(Effects of the Invention) As described above, according to the present invention, it is possible to avoid arcing at the contact portion with an electrode during electrical heating of a steel material, and to prevent deformation of the steel material due to pressing.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, and FIG. 2 is an illustration of an SU
It is a chart showing arc avoidance conditions in the case of S steel. 1: Steel material to be heated, 2.2': Electrode 6-1.
6-2: Voltage detector, 7: Power supply 8: Current detector, 9: Contact resistance/electrode pressing force control device 10: Control signal, 11: Stand agent Patent attorney Tatsuo Chanogi First cause

Claims (1)

[Claims] In the method of pressing and energizing heating by bringing a movable electrode into contact with the material to be heated, the contact resistance between the electrode and the material to be heated is detected,
An energization heating method characterized in that the current value is controlled based on the relationship between the current density of the electrode current-carrying part of the material to be heated and the contact resistance or the value obtained by multiplying the contact resistance by the apparent contact area.