JPH0569025A - Method and device for heating h-shaped steel in uniform temperature distribution - Google Patents

Abstract

PURPOSE:To establish a means which can correct the ununiformity of temperature distribution in hot rolling of an H-shaped steel exactly and inexpensively and prevent the product yield caused by thermal strain from deteriorating as possible. CONSTITUTION:When the temperature distribution of the H-shaped steel directly after rolling is uniformized, the direct energizing and heating method that alternating current is applied from an electrode in contact with both ends of a stock to be heated to heat it according to the Joule' law is applied and in direct energizing and heating treatment, plural electrodes 16 arranged face to face at both ends of the H-shaped steel 11 directly after rolling on a support table 14 made of non-electric conductor are brought into contact with plural positions of web parts at both ends, at the same time with this, alternating current having a phase shifted 180 deg. to this energizing current is applied to the induction coils arranged in opposition to the flanges of the H-shaped steel and the number of energized electrodes is changed at the initial time and the final time of the energizing time to heat the web only partially and to uniformize the temperature distribution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to H just after rolling.
The present invention relates to a method for homogenizing the temperature distribution of shaped steel by direct electric heating and an apparatus therefor.

[0002]

2. Description of the Related Art Generally, when an H-section steel is manufactured by hot rolling, if there is a difference between the web thickness and the flange thickness of the H-section steel, a temperature difference occurs during cooling after rolling, resulting in a product. The yield tended to deteriorate.

That is, when the flange thickness and the web thickness of the H-section steel are different, the heat capacities of the flange portion and the web portion are different, so that when the radiated heat progresses, a temperature difference occurs between the flange portion and the web portion. In H-section steel, the web thickness is generally thinner than the flange thickness. Therefore, if the temperature of the flange portion immediately after rolling is about 850 ° C, the temperature of the web portion is about 150 to 200 ° C lower than that. Is usually. For this reason, tensile stress is generated in the web portion, and wavy strain is generated due to plastic deformation due to the tensile stress, which leads to deterioration in yield. However, in recent years, especially for construction H
The demand for a large-sized thin web H-shaped steel as a shaped steel is increasing, and the thermal strain of the web is becoming a big problem.

Therefore, as a measure against the above-mentioned problem, as shown in FIG. 4, cooling water is supplied from outside the flange (3) of the H-section steel (2) at a high temperature by the spray nozzle (1). In order to reduce the temperature of the flange (3) to the same temperature as that of the web (4), a "temperature spray uniformization method by water spray" has been carried out. Reference numeral 5 in the figure indicates a table roller.

However, this "method of uniformizing temperature distribution by water spray" has the following problems. a) Cooling water may fly over the upper part of the flange to the web part, which may promote the temperature decrease of the web part. b) The above-mentioned cooling water splashes especially when the size of H-section steel changes. Since it is conspicuous, a method of arranging a plurality of spray nozzles in the height direction and switching the spray nozzle to be jetted according to the flange height is also adopted as a countermeasure,
In this case, there is a part near the upper part of the flange where cooling water does not flow, and uneven temperature tends to remain in the flange part, which causes defective shape of the flange part. C) Moreover, the product size of H-section steel is 100%. Since there are more than one type, it is difficult for a water spraying device in the same line to follow individual shape variations, and therefore the water spraying method cannot be a perfect temperature equalizing measure.

For this reason, recently, a proposal was made to compensate for excessive cooling of the web portion by heating the web in the rough rolling process of H-section steel and the like (Japanese Patent Laid-Open No. 61-2097).
No. 02). However, the above "web heating" is a bar.
This is not practical because it takes too much time to raise the temperature in the case of burner heating, and it also heats unnecessary parts (especially inside the flange). It was On the other hand, in the case of induction heating, it is difficult to control the gap between the induction coil and the web, even though it is necessary to dispose the induction coils close to each other with the web in between. There is also a problem in practical use, such as a large loss, resulting in a high equipment cost and a high processing cost.

In view of the above, the object of the present invention is to correct the temperature distribution non-uniformity during the hot rolling manufacturing of H-section steel at a precise and low cost, and to improve the product yield due to thermal strain. It was to establish means to prevent the deterioration as much as possible.

[0008]

Means for Solving the Problems In the process of advancing research from various viewpoints in order to achieve the above-mentioned object, the inventors of the present invention directly energize and heat the material to be heated. I was strongly attracted to the "direct current heating method". The "direct current heating method" is, for example, Japanese Patent Laid-Open No. 62-
As disclosed in Japanese Unexamined Patent Publication No. 86117, Japanese Utility Model Laid-Open No. 62-70160 or Japanese Unexamined Patent Publication No. 3-111517, electrodes are pressed and brought into contact with both ends of a material to be heated, and the material is heated through the electrodes. This is a method of applying an electric current to heat the material in a jule manner, and is attracting attention as a means for heating a material with high energy efficiency by a relatively simple facility.

However, the direct current heating method has never been applied to the correction of the uneven temperature distribution in the H-section steel at high temperature. This is because in order to make the temperature distribution of the high temperature H-section steel uniform, it is necessary to locally raise the temperature of only the web part where the temperature drop is remarkable, but the "direct current heating method" is applicable to all cross sections of the material to be heated. This is because it is intended to uniformly energize and heat uniformly, and it has been considered impossible to heat only a part of the cross section because diffusion of the current path occurs. Certainly, the point that "it is impossible to heat only a part of the cross section by the direct current heating method" was a fact that applies to most cases in heating of general materials.

However, the following facts have been found out as a result of research conducted by the present inventors through many experiments. a) In particular, in the case of H-section steel that is in the process of cooling from a high temperature state such as during rolling manufacturing, the temperature drop in the web portion is significant compared to the flange portion, so a large temperature difference occurs between the two and the flange portion Compared with the flange part, the electrical resistance of the web part, which is considerably lower than that of the web part, when it is energized becomes low, so until the temperature rises to some extent and the temperature difference with the flange part decreases. It is possible to raise the temperature of only the web part relatively efficiently by the direct current heating method, b) However, even in this case, the position of current application to the material to be heated is important, and good current heating efficiency is secured. In order to carry out such a direct current heating method for the H-section steel web portion, an induction coil is placed opposite to both flange portions of the H-shaped steel web portion, and Phase of web current When direct current heating is performed while supplying an alternating current that is shifted by 180 degrees, the induction current induced by this induction coil more reliably prevents the "circulation of the current applied to the web portion to the flange portion", Electric heating efficiency is further improved.

The present invention has been completed based on the above findings and the like. "In order to make the temperature distribution of the H-section steel immediately after roll forming uniform, the both ends of the material to be heated were brought into contact with each other. Applying the "direct current heating method" in which an alternating current is applied from the electrodes to heat the Jule, and in the direct current heating process, a plurality of electrodes placed opposite to each other at both ends of the H-section steel immediately after roll forming are provided on both end web parts. Of the H-shaped steel, and an induction coil is also arranged to face both flanges of the H-section steel so as to change the number of electrodes to be energized at the beginning and the end of the energization time of the web portion, and at the same time Current is supplied to the induction coil with an alternating current whose phase is shifted by 180 degrees to partially heat only the web, so that uniform temperature distribution can be achieved easily and accurately with good heating efficiency. Point In addition, "The direct current heating device is moved in the direction of the H-shaped steel support base made of a non-conductive material and the support bases arranged at opposite ends of the support base. A plurality of possible electrodes, a plurality of induction coils that are arranged to face the front and rear of the support and are connected to a phaser, and a power supply device that energizes the electrodes and the induction coil. By doing so, it is possible to easily and accurately make the temperature distribution of the H-section steel immediately after roll forming uniform. ”

The present invention will be described below in more detail with reference to the drawings. FIG. 1 and FIG. 2 are conceptual diagrams for explaining one example of “heating means for uniform temperature distribution of H-section steel” according to the present invention.

In FIG. 1, for example, the H-section steel (11) immediately after being rolled by a finishing mill is conveyed on a table roller (12) to reach a direct electric heating apparatus according to the present invention. The table roller (12) stops so that it stops at the heating position when the tip of the H-section steel (11) being conveyed is detected by the material detector (13).
Is equipped with an automatic circuit.

At the bottom of the position where the H-section steel (11) stops,
A support base (14) for lifting the shaped steel (11) to the top is provided, and at the top of the stop position, along the pedestal (15) in the line direction (approaching and separating from the support base (14)). The electrode device (16) is arranged so as to be movable in any direction. Of course, the H-section steel support 14 is made of a non-conductive material so that the heating current does not flow into it.

The electrode device (16) is arranged in pairs at both end portions of the support base (14), and as shown in FIG. 2 which is a plan view of a main part, the electrode moving device (17) has an electrode support tube. A plurality of electrodes (19) are attached via (18).

At the front and rear positions sandwiching the support base (14), a plurality of flanges (20) of the H-section steel (11) supported by the support base (14) are provided so as to face a plurality of surfaces. An induction coil (22) is arranged, and the induction coil (22) is connected to the power supply device (24) via the phase shifter (23).

The H-section steel (11) immediately after hot rolling, which has been conveyed on the table roller (12) and stopped at the heating position, is lifted upward by the support base (14) and both ends thereof are lifted. Electrode device (16)
Be opposed to. In this state, replace the electrode device (16) with H-shaped steel.
After approaching both end faces of (11) and pressing a plurality of electrodes (19) facing each other at a plurality of positions on the end face web (21) to bring them into contact with each other, an electric wire (25 A low-frequency alternating current is supplied to heat the web (21) by jule heating.

At this time, at the same time, an alternating current having the same system as the current supplied to the web (21) but having a phase shifted by 180 degrees by a phase shifter (23) is also supplied to the induction coil (22). ..

As described above, the H-shaped steel (1
When a current is applied to the web (21) of 1), the current tends to flow through the path having the shortest distance between the electrodes on both ends of the pair,
Flange (20) from the electrode near the flange (20)
Since a bypass route is also generated, it is usually unavoidable that the flange (20) is also heated by the jar. That is, when the position of the energizing electrode is close to the flange (20), the energization heating efficiency also tends to decrease.

Therefore, in the initial stage of energization, only the electrodes near the center of the web (21) in the width direction (for example, the electrodes 2 to 3 at the center of the web).
(Only for books), and make arrangements to energize all electrodes when the energization time reaches the latter half. This allows the flange
The current diverted to (20) is reduced as much as possible.

Moreover, while the web (21) is being energized, an alternating current whose phase is 180 degrees out of phase with the current supplied to the web is also supplied to the induction coil (22) facing the flanges (20). Therefore, the induction coil (22) induces a current in the direction opposite to the web current. for that reason,
The current flowing from the electrode (19) to the web part (21) and trying to bypass the flange part (20) is induced by the induction coil (22) and the course is blocked by the induced current flowing in the opposite direction to the web current. As a result, the bypass current to the flange portion (20) can be more surely suppressed.

Therefore, according to the above direct current heating, only the web portion (21) having a low temperature is appropriately heated by the jule heat, the temperature distribution of the H-section steel immediately after rolling is made uniform, and the deformation due to heat shrinkage is prevented. can do.

Regarding the energizing time, the radiation thermometer (26) measures both the flange (20) and the web (21), and energizes until the temperatures of both are uniform. Normally, in H-section steel immediately after hot rolling, the flange temperature is about 850 ° C and the web temperature is about 650 ° C, but the time required to electrically heat the web to 850 ° C is about 2 minutes / cycle. Since the time can be absorbed during the rolling pitch for this time, heating can be completed without impairing the rolling efficiency.

Next, the effects of the present invention will be described more specifically by way of examples.

EXAMPLE An H-section steel having a cross-sectional dimension shown in FIG. 3 (length: 20
m), flange temperature 850 ° C, web temperature 65
A test was conducted in which the web temperature was electrically heated to 850 ° C. from the state of 0 ° C.

In the test, an electric heating device as shown in FIG. 1 and FIG.
Press the electrodes one by one, and make a total of 15Hz alternating current 15
kA flowed. At the same time, the induction coil placed opposite to the flange of the H-section steel is connected to the same power source as the above-mentioned electrode,
The current of (1) was applied with the phase shifted by 180 degrees. At this time, for 60 seconds after the start of energization, only three of the five electrodes at the center of the web width direction were energized, and then 4
For 0 seconds (that is, up to 100 seconds in total elapsed time), electricity was supplied from all electrodes.

As a result, only the web portion is 850 ° C. ± 5 ° C.
It was possible to make the temperature distribution of the H-section steel uniform by raising the temperature to the temperature range of. The temperature of the flange is approximately 850 ° C.
However, this is considered to be a result of the balance between the cooling and the heating by the leakage current or the induction current.

As described above, in the direct current heating according to the present invention, the H-shaped steel web is effectively prevented in the preceding stage of heating while effectively preventing the direct current from being bypassed to the flange by the induced current by the induction coil. Since most of the heating is performed by the electrodes that are in contact with the center of the width direction, the temperature near the center of the web is efficiently raised. Since it is possible to make the temperature uniform, the uniform temperature distribution can be achieved efficiently and accurately, and it becomes possible to manufacture an H-section steel with good shape accuracy.

[0028]

[Summary of Effects] As described above, according to the present invention, the uneven temperature distribution in the production of H-section steel by hot rolling can be corrected promptly and accurately without requiring large equipment, and the shape can be corrected. Industrially useful effects are brought about, such as being able to stably manufacture highly accurate products.

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating an example of “heat treatment means for uniform temperature distribution of H-section steel” according to the present invention.

FIG. 2 is a plan view of a main part of an electrode portion of FIG.

FIG. 3 is an explanatory view of a cross-sectional dimension of H-section steel used in the examples.

FIG. 4 is an explanatory diagram relating to a conventional method for uniformizing the temperature distribution of H-section steel by a water spray.

[Explanation of symbols]

 1 Spray Nozzle 2 H-Shaped Steel 3 Flange 4 Web 5 Table Roller 11 H-Shaped Steel 12 Table Roller 13 Material Detector 14 Support 15 Stand 16 Electrode Device 17 Electrode Transfer Device 18 Electrode Support Tube 19 Electrode 20 Flange 21 Web 22 Induction coil 23 Phaser 24 Power supply 25 Wire 26 Radiation thermometer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area H05B 6/40 8915-3K

Claims (2)

[Claims] 1. A "direct current heating method" in which an alternating current is applied from an electrode in contact with both ends of a material to be heated to heat the material for jule heating.
"H-shaped steel uniform temperature distribution heat treatment method", wherein a plurality of electrodes, which are arranged opposite to each other at both ends of the H-shaped steel immediately after roll forming, are brought into contact with a plurality of positions of both-end web portions, Induction coils are arranged opposite to each other on both flanges of the H-section steel, and the number of electrodes to be energized is changed at the beginning and the end of energization time at the time of direct energization heating, and at the same time, the energization current is 18
A method for uniformizing the temperature distribution of H-section steel, characterized in that only the web is partially heated by passing an alternating current whose phase is shifted by 0 degree to the induction coil. 2. An H-shaped steel support base made of a non-conductive material, a plurality of electrodes, which are arranged at opposite ends of the support base and are movable toward the support base, and front and rear portions of the support base. An H-shaped steel having a uniform temperature distribution, which is provided with a plurality of induction coils arranged opposite to each other and connected to a phaser, and a power supply device for energizing the electrodes and the induction coil. apparatus.