JP5001456B1 - Electrode wheel for energization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of a spark in a method for directly electrically heating a band-like or bar-like metal material by supplying current to the material while making the material travel. <P>SOLUTION: The gear-shaped electrode wheel is made to contact with and follow a surface of a traveling material to be heated. A tooth tip is an electrode protrusion, and intermittently comes into contact with and presses the material. After contact, electricity is supplied, and electricity is shut off just before releasing, and intermittent supply of electricity is performed. Different from a roll electrode (a conduction point is moved and unstable), energization is opened and closed in a state that the conduction point is fixed, and therefore, the generation of a discharge spark can be prevented, and the generation of the spark can be prevented. Two of the electrode wheels are provided along a travel path, the positions of the electrode protrusions of them are synchronized, and the space therebetween is electrically heated. A spark scar can be prevented, and high quality can be achieved. Heating efficiency of 90% or more is achieved and the heating efficiency is increased to twice with respect to high-frequency heating. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to a method of continuously heating a long metal material by a direct energization method, and more particularly to preventing a spark (electric spark) generated between an object to be heated and an electrical contact accompanying energization.

  There are various methods when heating a rod-like or strip-like metal, especially long steel such as steel bars, wire rods, and thin plates, while running, but there is a variety of methods.・ In some cases, processing is highly efficient. In this method, a heating efficiency (= necessary heat amount / heat consumption amount) of 95% or more is obtained. On the other hand, a spark may be generated between the electrical contact and the steel material, and the surface of the steel material is slightly melted. Although it is not a problem for low-grade products, it is disliked for high-grade products even if they are used for spring steel because they affect fatigue fracture, and it has not been applied yet and induction heating is used. In this case, the heating efficiency is at most 50%.

  When energizing the traveling material to be heated, the electrodes are joined by sliding or roll pressing. In the heat treatment of steel, the latter is frequently used due to wear and heat resistance problems. In the roll pressure welding, the contact point is fixed at one point when viewed from outside the system, but when viewed from one point on the roll, the contact point moves from time to time through approaching, contacting, separating, and turning around the object to be heated. For this reason, when there are impurities, the energized state fluctuates, and a discharge phenomenon tends to occur at or around the contact portion. Generally, discharge is more likely to occur at higher voltages, and local melting is likely to occur at higher currents. Stable electrical contact is essential to prevent sparks.

  As a prior example 1, Patent Document 1 discloses a method for preventing sparks in the direct current heating method. According to this, the mechanical contact between the energizing roll, which is an electrical contact, and the steel plate becomes unstable near the both edges of the steel plate, and sparks are generated. As a countermeasure, measures are taken to prevent thermal deformation of the roll. Maintaining contact. The problem is that a spark is an instantaneous arc discharge due to contact abnormality in the process of contact or separation. In the case of this method, since the contact and the steel material move and approach and separate while moving by biting and biting by the roll, the contact state always fluctuates and is unstable, which is insufficient to solve the abnormal contact.

  As a prior example 2, in Patent Document 2, as described above, multi-point contact is made through a special conductive brush (composite carbon fiber plate) planted on the outer peripheral surface of the wheel without directly contacting the energizing wheel in the energization heating. It is disclosed that the occurrence of sparks can be prevented. When observing the durability test of the method, a lot of fine sparks are stably generated, but it does not become a spark, it does not become a flaw due to its fineness, and the brush does not become high temperature due to the large heat conductivity of graphite fiber, It turns out that there is little oxidation exhaustion. The problem is that it is difficult to manufacture special conductive brushes, the cost is extremely high, and they are not yet popularized.

When the state of current heating by the current-carrying rolls installed at two points in the direction of travel of the straight wire was observed closely, the occurrence of sparks and sparks was found to be as follows.
1) Sparks are strongly influenced by the surface condition of the wire, especially the remaining of foreign matters such as oxide film and the separation pool.
2) There are many sparks when the pressing force is light (contact resistance fluctuation or contact position movement).
3) The downstream roll (wire temperature is about 1000 ° C.) has a smaller and less spark than the upstream roll (because the pressure is stable).
4) As a roll material, graphite cast iron is better than copper, and graphite is better.
5) Both upstream and downstream rolls occur on both the biting side and biting side, but both on the biting side. An arc is more likely to occur at the time of separation than at the time of approach.
6) On the downstream side, many fine sparks are always visible, but there are no sparks.
7) Sparks are generated even if the load current is changed from AC to DC. There is no big difference.
8) On the upstream side, local red heat is generated immediately below the contact area, and then the heat diffuses and soaks, and the red hot spot is seen to fluctuate and move. It can be seen that the contact is moving and that the contact has a local high current density.
From the above, the contact portion is geometrically a point or a line, but actually forms a spot-like surface by elastic pressing. There are many conduction points in it, and it fluctuates and moves from moment to moment. At the moment of contact, a molten spark is generated by a local large current due to point contact depending on the situation, while fine arc discharge is always generated at the moment of separation. It is speculated that each big thing becomes a spark.

  Therefore, in order to prevent sparks, it is necessary to make sure that the contact state is stable and stable in combination with the previous case, and to make the spark itself fine and harmless by making multi-point contact, but it creates a situation where the discharge itself does not occur. It is more desirable.

Published Patent Publication No. 05-345931 Published Patent Publication 2004-63293

  When energizing the metal continuously while running straight through a long metal, the two electrodes, usually roll-shaped, are rolled as contact electrodes and energized to the material to be heated. Heat with Joule heat. Depending on the surface condition of the material to be heated, the properties of the electrode surface, the pressed state, etc., a spark is generated at the contact portion, which sometimes becomes a spark and generates flaws on the surface of the material to be heated, resulting in a decrease in product quality. This invention makes it a subject to prevent generation | occurrence | production of this spark.

  In order to solve this problem, the present inventor, when bringing the electrode into contact with the material to be heated, intermittently repeatedly presses the electrode with the material to be heated, and turns off at the moment of contact and the moment of separation, and energizes only during that time. It has been found that the occurrence of sparks and thus the occurrence of sparks can be prevented by the above-described process, and the present invention is constructed.

  The first invention is a method in which a belt-like or rod-like metal material is run while directly energizing and heating the material, and the electrode energized in contact with the material has a large number of electrode protrusions on the outer peripheral surface of the wheel. A gear-shaped electrode ring provided at intervals, and when the electrode protrusion of the electrode ring is pressed and followed at the same speed while being fixedly contacted with a heated material that travels straight, By energizing the material to be heated from the protrusion and turning off the current immediately before the protrusion is separated from the material to be heated by rotation, the generation of sparks at the time of contact and separation is suppressed, and after the separation, The direct current heating method is characterized in that the electrode projections are contacted and the same operation is repeated to intermittently energize continuously.

  According to a second aspect of the present invention, electrode rings are provided at two locations on the traveling path of the material to be heated, and the electrode protrusions of the both electrode rings are synchronized with each other at the same position on the circumference. The direct current heating method according to the first aspect, wherein the material to be heated is energized and heated.

  According to a third aspect of the present invention, an electrode wheel is provided at one place on the traveling path of the material to be heated, a roll electrode that is always in contact with the electrode wheel is provided on the downstream side of the electrode wheel. The direct current heating method according to the first aspect, wherein the material is heated by energizing the material.

The predicate definition is as follows.
The fixed contact means a state where the contact point between the electrode and the material to be heated is fixed. In the roll electrode, the contact moves on both the electrode surface and the heated material surface.
“Pressing” refers to a state in which contact resistance is stabilized by a certain amount of rolling force.
Contact is not the state of contact, but the moment of contact.

According to the present invention, when a long steel plate or bar wire is run straight and continuously heated, the current-carrying electrode is intermittently pressed by the material to be heated in the method of heating by direct energization of the material to be heated. The Since power is supplied immediately after pressing and the electrode is turned off immediately before the electrode is separated from the material to be heated, the occurrence of sparks due to contact and separation is suppressed, and the problem of spark scratches is solved.
As a result, it is possible to replace the high-frequency induction heating that has been widely used in the past, and the heating efficiency is doubled to save energy.
In practice, the equipment cost is the same level as the conventional roll electrode system, which is more advantageous than induction heating.

It is the schematic of the principal part of the apparatus which implements the direct electricity heating method of this invention. It is the whole apparatus schematic which implements the direct current heating method of the present invention. The example of the other apparatus which implements the direct electricity heating method of this invention is shown.

  The direct energization method of the present invention will be described with reference to FIG. The electrode wheel 2 comes into contact with the heated material 1 that travels straight and rotates and follows the current. The electrode wheel 2 mainly includes a wheel 21, conductive electrode protrusions 3 provided at equal intervals on the outer peripheral surface of the wheel 21, and is individually connected to the electrode protrusions 3 to be concentric with the side surfaces of the wheel 21. It comprises a commutator 4 provided at intervals, a brush 5 fixed to a fixed base (not shown) that is in sliding contact with the rotating commutator 4, and a rotating mechanism (not shown). The brush is similar to the brush of a DC motor and has a graphite block shape. The outer shape of the electrode ring is gear-shaped.

  The rotating electrode protrusion 3 contacts the material to be heated 1 at the point p and separates at the point q. In the meantime, both are in mechanical contact, move at the same speed, and the electrode protrusion 3 maintains an elastically pressed state against the material 1 to be heated. Since the locus of the tip of the protrusion is slightly arcuate, it is desirable that the back surface of the material to be heated is pressed when the material to be heated is thin (thin), and the electrode protrusion is elastically retractable when the material to be heated is thick (thick). In any case, the fixed contact is more stable when the protrusion is elastically flexible not only in the vertical direction but also in the longitudinal direction. The design is not particularly difficult for those skilled in the art. The pitch (interval) of the electrode protrusions 3 is not less than the length pq. As soon as the preceding electrode protrusions are separated, the subsequent electrode protrusions come into contact with each other and the intermittent contact state is maintained.

  The contact state is essentially different from that of a conventional roll electrode. The former is fixed pressing contact, but in the latter, the contact point is constantly moving on the surface of the material to be heated and the surface of the roll, and the former is remarkably excellent in terms of stability of conduction.

  The commutator 4 has an appropriate length in the circumferential direction. Immediately after the electrode protrusion 3 reaches the point p and presses the material 1 to be heated, the front end of the commutator 4 (in the rotational direction) at the point r. The front) contacts the rear end (upstream side) of the brush 5 to start energization. When the rear end of the commutator 4 reaches the front end of the brush 5 at the point s with rotation, the energized state is cut off. Corresponding to the length of the commutator in the circumferential direction and the length of the brush in the running direction, the positions of the r point and the s point move back and forth. The electrode protrusion 2 is separated from the material to be heated 1 at the point q after turning off.

  Therefore, at the moment of starting energization, the electrode protrusion 3 has already been fixedly pressed against the material 1 to be heated, so that no spark is caused by energization. Similarly, at the moment of turning off, a spark is not generated in a fixed pressing state. It is the core of the present invention to suppress the spark phenomenon by opening and closing the energization only in the fixed pressing state.

  The energization is temporarily cut off, but after the electrode protrusion 3 is separated, the subsequent electrode protrusions and the like repeat the same operation to constitute intermittent energization. Strictly speaking, intermittent energization is a kind of batch heating in the length direction of the material to be heated. In some cases, uneven heating may be a concern, but since the ratio of the heating zone length / energization length rs is large in a heating apparatus described later, continuous energization / continuous heating is performed in the same manner as conventional roll electrodes.

  The electric heating method of the present invention will be described with reference to FIG. Two electrode wheels 2 and 9 are provided for the heated material 1 that travels straight. A heating zone is formed between both electrode wheels. The length is appropriately designed in consideration of production efficiency, non-heated material cross-sectional area, traveling speed, heating speed, specific resistance, and the like. There is no particular problem for those skilled in the art. Generally, it is 1 to several meters.

A sliding guide 8 is provided on the back surface of the material to be heated in order to stabilize traveling and to form a pressing force. Both electrode wheels 2 and 9 are controlled by the synchronizing means 10 so that the electrode protrusions are always in the same phase.
The same phase means that the upstream and downstream electrode protrusions are simultaneously positioned at the point p. As a specific means, a gear train or a timing belt is used. Conductive wiring is performed from the single-phase power source 11 to the brushes of both electrode wheels. When a predetermined voltage is applied, a current corresponding to the resistance of the heating zone flows and is heated. Measure the current and adjust the current. Direct current heating similar to the conventional one can be easily obtained.

  A driving force is applied to the electrode wheels 2 and 9 to follow the traveling of the heated material 1. Regarding the synchronous control, it must be taken into consideration that the traveling speed is slightly different at the positions of the electrode wheels 2 and 9 (due to thermal expansion and tension stretching). For example, the electrode ring diameter is corrected.

The commutator 4 and the brush 5 must be precisely manufactured so as to slide smoothly like a commutator of a large DC motor. Small sparks are always generated on the brush surface, but no spark is generated.
In the case of the mechanical method regarding the formation of the intermittent current, the current value becomes extremely large when the cross-sectional area of the material to be heated is large, and the mechanical control of the circuit is easy to generate electric discharge at the brush part, so electronic control Is preferred. The current is electronically intermittent by feeding back the position of the electrode protrusion. In this case, the rectifying mechanism described above is unnecessary.
As a simple example, one cycle time of the electrode protrusion is made to coincide with one cycle of alternating current, and the alternating current is made half-wave rectified by a rectifier and synchronized. When the half-rectifier is turned off, the contact of the protrusion is separated. In this case, a rectifying mechanism using a commutator and a brush is not necessary. These specific designs are not particularly difficult for those skilled in the art.
If an appropriate circuit using a thyristor is assembled, it is possible to easily cope with changes in various operating conditions.

  A test for confirming the occurrence of sparks in contact and separation of electrodes in the energization circuit was conducted. Using a normal 30 kW welder, the voltage was rapidly increased to 500 A with both electrodes (made of copper) pressed strongly against each other. The contact was red hot but no spark was generated. Next, the steel plate was energized with both electrodes pressed, and the current was raised to 500 A, and it was confirmed that no spark was generated although it was also red hot. A large spark occurred when the electrode was slid. As is well known, it was confirmed that sparks were likely to occur when the contacts moved, and that no sparks were generated when the contacts were fixed.

A simpler implementation method of the current heating method of the present invention will be described.
As shown in FIG. 3, the structure is the same as that of FIG. 2, but the downstream (high temperature side) electrode wheel is rotated while being pressed by a conventional graphite cast iron roll. In the vicinity of 1000 ° C., minute sparks are always generated but are not sparked. The intermittently energized electrode wheel of the present invention is applied only to the upstream electrode wheel to prevent harmful spark scratches. In this case, a synchronization mechanism for both electrodes is not necessary.

  The direct current heating of the present invention can be substituted for the conventional induction heating, and the heating efficiency is doubled to contribute to energy saving.

  1: Heated material 2: Electrode wheel 21: Wheel 3: Electrode protrusion 4: Commutator 5: Brush 6: Conducting part 7: Non-conducting part 8: Sliding guide 9: Downstream electrode wheel 10: Synchronizing means 11: Single Phase power supply 12: Roll electrode

Claims (3)

In a method in which a belt-like or rod-like metal material travels straight while passing through an electric current directly through the material, the electrode energized in contact with the material has a large number of electrode protrusions provided at equal intervals on the outer peripheral surface of the wheel. A gear-shaped electrode ring, and when the electrode protrusion of the electrode ring is pressed against the material to be heated while moving in a straight line while being followed at the same speed, after the contact of one protrusion, the protrusion from the protrusion by energizing the heating member, while suppressing the occurrence of sparks during the contact time and the separation by cutting the current just before moving away from the material to be heated by projecting outs rotation, projecting outs away after the subsequent electrode projecting A direct energization heating method characterized in that the same operation is repeated by contact and intermittent energization is continued.   Electrode wheels are provided at two locations on the travel path of the heated material, and the electrode protrusions of both electrode wheels are synchronized with the same position on the circumference, and the heated material between the electrode wheels is energized from both electrode wheels. The direct current heating method according to claim 1, wherein the heating is performed.   An electrode ring is provided at one location on the traveling path of the heated material, a roll electrode that is always in contact with rolling is provided downstream of the electrode wheel, and the heated material between the electrodes is energized from both electrodes. The direct current heating method according to claim 1, wherein the heating is performed by heating.