JPH08118027A - Width widening method of plasma jet - Google Patents

Abstract

PURPOSE: To industrially execute heat treatment of metal material with plasma jet by widening a width of plasma while plasma jet is directly hit to a material to be treated in heating metal material of steel, etc., particularly by means of practical means in the case of a plate material requiring heating in wide range. CONSTITUTION: In the method to widen a width of plasma jet in which widening gas to widen plasma jet is simultaneously jetted to the plasma jet, which is jetted from the outer nozzle of a plasma torch, in the direction intersecting to the center axis line of an outer nozzle from two places, gas jet angles for widening are set to <=20 deg. respectively. In comparing to the plasma jet oscillating method to switch jet direction of widening gas, a switching device is not required, thus, widening of plasma jet is made possible by a simple constitution to adjust a jet angle of widening gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for widening a high temperature gas jet, that is, a plasma jet, which is turned into plasma by electric arc discharge.

[0002]

2. Description of the Related Art When heating a metal material such as steel, a method is known in which a plasma jet injected from a plasma torch is directly applied to a heat-treated material. This method has the advantages that the material to be treated is heated rapidly and that a treatment material without oxide scale can be obtained by using non-oxidizing or reducing plasma.

However, when using such high-density energy, the energy is concentrated in a narrow region of the material to be processed, and the irradiation area of the plasma jet is extremely limited. Therefore, a wide range such as a steel plate is heated. In order to do so, it is necessary to arrange a large number of plasma torches or mechanically shake the plasma torches to expand the irradiation area.

Japanese Unexamined Patent Publication (Kokai) No. 54-24249 discloses a defect removing method in which a defective metal material surface on the surface of a cast metal material or a rolled metal material is removed by melting with a transfer type plasma jet torch. There is. In order to remove a wide range of defects, an electromagnet core is arranged between the plasma jet torch and the metal material, which exerts a magnetic field orthogonal to the arc moving from the torch to the metal material, that is, the plasma arc current to deflect the plasma current. Let By alternately reversing in the energization direction of the electromagnet, the plasma arc current reciprocates and scans the metal surface. As a result, a wide area of defects is removed. JP-A-54-2424
Japanese Patent Publication 9 also discloses a mode in which an electric coil is inserted between a transfer-type plasma current and a metal material to reciprocate a plasma arc current.

On the other hand, the non-transfer type plasma arc is characterized by high-temperature local heating, but a uniform and wide range of heat source is required in the surface treatment of the steel sheet on a micron order. There was no device.

Therefore, the applicant has installed an electric coil for inserting a heat insulating collar between the inner nozzle member and the outer electrode member to surround the plasma flow path from the plasma nozzle to the plasma injection port and generating a magnetic flux across the heat insulating collar. A non-transfer type plasma jet torch equipped with the same was presented (Japanese Patent Laid-Open No. 4-279).
No. 284). According to this, the position where the magnetic flux is applied is made to act as a part where the arc current is confined in the torch, that is, the plasma arc current is deflected by the action of the magnetic field at the base part, so a relatively small electric coil is used. A large deflection amount can be obtained, and the plasma jet oscillates according to the direction and magnitude of the current flowing through the coil.

Furthermore, the applicant of the present invention has disclosed in Japanese Unexamined Patent Publication No. 5-234469.
Japanese Patent Laid-Open No. 5 discloses a technique for oscillating a plasma jet by a gas injection method. According to this, by alternately ejecting the broadening gas in a direction intersecting the central axis of the plasma nozzle to the plasma jet ejected from the outer nozzle of the plasma torch, the plasma jet is oscillated in the above-mentioned direction. The manner of widening the jet is shown. Further, as shown in FIG. 4, the plasma torch used for this also refers to a method of broadening a plasma jet by simultaneously ejecting a broadening gas from a broadening gas supply pipe.

[0008]

However, in the above-mentioned prior art, there is a problem that an unintended evaporation phenomenon of the outer nozzle electrode occurs when the magnetic field is applied to oscillate the plasma jet. Further, in the above-mentioned JP-A-5-234695, a gas switching device for alternately supplying the swinging gas is required, and the switching frequency of the swinging gas cannot mechanically follow the strip speed of the material to be processed, and There is a problem in that there is a peak in the temperature pattern when the plasma jet is irradiated onto the steel plate or the like.

The present invention is a method for directly applying a plasma jet to a material to be treated when heating a metal material such as steel material. The plasma jet is broadened, and a wide range is made uniform, particularly when the material to be treated is a plate material. It is an object of the present invention to realize industrial heat treatment of a metal material by a plasma jet by providing a specific means for heating.

[0010]

SUMMARY OF THE INVENTION The gist of the present invention as means for achieving the above object is to provide a plasma jet ejected from an outer nozzle of a plasma torch in a direction intersecting a center line of the outer nozzle. In order to widen the plasma jet by simultaneously ejecting a widening gas for widening the plasma from two opposite locations,
It is a method for widening a plasma jet, characterized in that each of the widening gas ejection angles at each location is set to 20 ° or less.
Here, the broadening gas ejection angle means an angle formed by a plane orthogonal to the center of the outer nozzle and the broadening gas ejection direction (see FIG. 3C).

[0011]

When the present inventors simultaneously eject the broadening gas from the two widening gas jets to the plasma jet in the direction intersecting the central axis of the nozzle, the broadening gas is applied to the plasma jet.
The plasma jet intersects with the injected broadening gas on the central axis, and the plasma jet spreads in the direction orthogonal to the widening gas injection direction.The heating gas amount of the plasma jet, the electrode gas amount, and the broadening gas amount. An experiment was conducted to find the conditions for uniformly heating a wide range, since it is possible to widen the width of any plasma jet by changing the angle of the widening gas jet.

That is, using a plasma torch as shown in FIG. 3, the amount of plasma gas (electrode gas + heating gas) and the amount of broadening gas were kept constant, and the steel sheet was heated by changing the jetting angle of the broadening gas. As shown in FIG. 3C, the broadening gas ejection angle is the angle formed by the plane of the broadening gas ejection direction and the plane orthogonal to the center line of the outer nozzle of the plasma torch. FIG.
As shown in (a), the temperature of the steel sheet was measured by irradiating the steel sheet with plasma while ejecting the gas for widening from the nozzle of the plasma jet. The jetting direction of the widening nozzle and the moving direction of the steel plate are the same. The plasma gas spreads in a direction perpendicular to the moving direction of the steel sheet (referred to as the widening direction), and the temperature of the steel sheet was measured at the same interval (40 mm) in the same direction as the widening direction as shown in Fig. 3 (b). did.

As a result, FIGS. 2 (a), 2 (b), 2 (c),
The temperature curve of (d) was obtained. 2A shows a case where the widening gas jet angle is 10 °, FIG. 2B shows a case where the widening gas jet angle is 15 °, and FIG. 2C shows a case where the widening gas jet angle is 2.
In the case of 0 °, the widening gas ejection angle is 22 ° in FIG. 2 (d).
Is the case. According to this result, when the widening gas injection angle with respect to the center line of the outer nozzle is large, a temperature peak occurs and sufficient widening cannot be obtained (FIG. 2 (a)). It will be blocked, and the temperature will be low and the required temperature will not be obtained (Fig. 2
(D)).

Based on this result, widening of the heating range,
This temperature distribution curve was examined from the viewpoints of uniformization and high temperature. In this temperature curve, a region surrounded by a line having a plate temperature of 1000 ° C. and the temperature curve, that is, FIG.
The vertical line part of (d) is (sj), and the rectangular region surrounded by the line of the plate temperature of 1000 ° C. and the maximum value of the plate temperature, that is, the hatched part of FIGS. 2 (a) to (d) is (ss). , And the ratio of both (sj / ss) was used as the plate temperature flatness index.

That is, the plate temperature flatness index serves as an index of how wide and uniformly the heating range of the plasma jet is heated to a high temperature. The larger the value, the better the heating condition.

Further, the relationship between the plate temperature flatness index and the plasma gas ejection angle was investigated. The result is shown in FIG. As can be seen from this figure, when the plasma gas ejection angle is 20 ° or less, the plate temperature flatness index (sj / ss) becomes 50% or more, that is, the temperature peak is not generated, and the heat of plasma irradiation is uniformly applied to the steel plate. It is transmitted (Fig. 2 (c)) and can be heated for the purpose. The lower limit of the widening gas ejection angle is not particularly limited, but if the angle is too small, the plasma gas is blocked and it becomes difficult to obtain the required temperature, and the widening gas supply pipe and nozzle are easily melted and damaged. Therefore, it is preferable that the angle is 5 ° or more.

As described above, according to the present invention, since the plasma jet can be widened only by adjusting the widening gas ejection angle, it is possible to avoid the above-mentioned unintended deposition phenomenon of the electrode due to the magnetic field. Further, it is possible to achieve widening by a simple means without requiring a device for supplying rocking gas. Therefore, a single plasma torch can heat a metal material such as a steel plate over a wide range.

Further, by using a plasma jet of a reducing gas or an inert gas, the metal material can be heat-treated over a wide range without forming an oxide scale. Also,
In a reducing atmosphere furnace, if the method of the present invention is used on the inlet side of the material to be processed to perform rapid heating with a non-oxidizing plasma jet and the temperature is maintained at a predetermined temperature with a heater, etc. Can be shortened to

A reducing gas is used as the heating gas for the plasma torch, and a reducing gas or an inert gas is used as the broadening gas to broaden the plasma jet flow, thereby making the metal surface, the pipe material surface or the wire surface. The oxide film of can be widely removed by the reducing action. In addition, by using an inert gas or active gas as the heating gas and the broadening gas to broaden the plasma jet flow, it is possible to perform high-temperature heat irradiation over a wide range, and to dissolve, quench, and burn a wide range of metals and nonmetals. It is possible to return it.

Further, by irradiating the work material with the plasma jet torch obliquely, more uniform and wide-range heat irradiation is possible, and the plasma jet torch is widened by making the angle close to parallel to the irradiation surface. Irradiation with a plasma jet stream enables a more uniform heat source. The broadening gas may be used at room temperature, but if a preheated high temperature gas is used, the effect on the processed material will be greater.

[0021]

EXAMPLE A steel plate 15 was heated using the plasma torch shown in FIGS. Here, the plasma current is 200 to
500A, heating gas (using hydrogen gas) (40-60) ~
(200 to 300) Nl / min, electrode gas (using argon gas) is 20 to 50 Nl / min, and broadening gas (using nitrogen gas) is supplied at 50 to 250 Nl / min through the supply pipe 9, respectively, and the present embodiment is carried out. In the example, when the widening gas ejection angle was 20 ° and the steel plate 15 was moved while being irradiated with the plasma jet, the oxidized surface of the steel plate 15 could be reduced over a wide range. At that time, the width of the reduction region could be three times or more as wide as when the widening gas was not used appropriately.

[0022]

As described above, according to the present invention, since the width of the plasma jet is widened with respect to the central axis, the surface of the material to be processed is exposed to the high temperature plasma jet with a wide width. In addition, it is possible to have a simple configuration in which only the broadening gas of the plasma jet and the jetting angle of the broadening gas are adjusted. Furthermore, since the oscillation of the plasma jet moves with respect to the plate surface, uniform irradiation is difficult. In the present invention, the steel sheet is constantly irradiated with the plasma jet, so that stable and uniform heating is possible.

[Brief description of drawings]

FIG. 1 is a ratio (sj / ss: plate temperature flatness) of a widening gas ejection angle, a heat-affected zone (sj) of a plasma jet, and a rectangle (ss) surrounded by a plate temperature of 1000 ° C. or more and a plate temperature maximum value. The figure which shows the relationship of (index).

FIG. 2 (a) is a diagram showing a temperature curve of a steel sheet when the steel sheet is irradiated with a plasma jet. When the widening gas ejection angle is 10 °, FIG. 2 (b) is a widening gas ejection angle of 15 °.
In the case of (c), when the widening gas ejection angle is 20 °,
(D) shows the case where the widening gas ejection angle is 22 °, respectively.

3A is a diagram showing a state in which a plasma jet is being emitted while ejecting a broadening gas to a steel sheet, FIG. 3B is a diagram showing a temperature measurement location of the steel sheet, and FIG. 3C is a broadening gas ejection angle. FIG.

FIG. 4 shows a specific example of a plasma torch for widening, and FIG.
II sectional view of FIG.

5 is a bottom view of the plasma torch shown in FIG.

[Explanation of symbols]

1 electrode 2 chuck 3 cap 4 electrode base 5 core 6 inner nozzle member 6n inner nozzle 7 centering stone 8 outer nozzle member 8n outer nozzle 9 ₁ , 9 ₂ widening gas supply pipe 14 insulating collar 15 steel plate

Claims (1)

[Claims] 1. A plasma jet to be ejected from an outer nozzle of a plasma torch, a broadening gas for broadening the plasma jet in a direction intersecting with a central axis of the outer nozzle is jetted simultaneously from two opposing locations to form a plasma jet. In the method for widening the width of the plasma jet, the widening gas jetting angles at the two locations are each set to 20 ° or less.