JPS5847274B2 - Arc swing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to arc or plasma arc (hereinafter both will be collectively referred to as arc).

) is spatially swung by the action of an external magnetic field.

It is well known that a current flowing in an arc is subjected to a Lorentz force in a magnetic field having a vector component perpendicular to the current, and that the current path is bent as a result.

In addition, the present inventor first applied an external magnetic field perpendicular to the arc and caused the arc and/or the external magnetic field to operate in alternating current, thereby bringing the Lorentz force acting on the arc current into an alternating state. Invented a method of swinging a fan on a fan-shaped plane.

However, this rocking force method has the drawback that the arc spot can only move in one dimension, reciprocating along a fixed straight line.

In addition, the moving speed of the arc spot is large at the center on the reciprocating line and small at both ends, so the heat input distribution due to arc heating is uneven, with large amounts at the ends and small amounts at the center, making it difficult to control the spatial distribution of heat input. Have difficulty.

The present invention ameliorates these drawbacks.

The behavior of an arc in an oblique magnetic field will be explained in principle with reference to FIG.

In the figure, 1 is a torch for arc or plasma generation, and 2 is a metal material.

An arc is generated between the torch 1 and the metal material 2.

To simplify the explanation, the origin of the coordinates is set at point C directly below the torch on the surface of the metal material.

The external magnetic field is spatially uniform and intersects the °2 axis that connects the torch and the coordinate origin at an angle of θ, and the x'y plane that defines the X and y axes is It is a metal surface.

i! First, consider the movement of the arc spot on the surface of the metal material 2 when an arc is ignited with the magnetic field intensity B set to zero, and then the intensity is increased while the direction of the magnetic field remains fixed.

When the magnetic field strength is zero, the arc spot is at the zero point.

The arc current at this time has only the Z component.

Apply an external magnetic field to this.

The force F acting on the current ■ from the magnetic field B is given by F=IXB per unit length according to the law of electromagnetic observation.

Here, F, I, and B are force, current, and magnetic field strength expressed as vectors.

IXB means vector product.

When the arc spot is at the 0 point, the arc current is only 2 precepts Iz.

When the X component Bx of the external magnetic field acts on this, a force F in the y direction
y=z-Bx occurs, and the arc spot shifts in the y direction.

When it shifts in the y direction, a y component ■y is generated in the arc current, and a magnetic field component Bz acts on it, resulting in a force in the X direction Fx = IyBz
comes out.

For this reason, the arc spot moves in the y direction and simultaneously moves in the x direction due to the magnetic field.

Due to the shift in the X direction, an X component Ix is created in the arc current, and a new force in the y direction is generated between this and Bz, but the direction of this force is opposite to the force in the y direction previously given by IzBx. Direction.

Therefore, as a general form, the force in the y direction acting on the arc F y
= IzBx-IxBz.

When the absolute value of the current is fixed and the magnetic field strength is increased, the FX
increases monotonically, but since Fy is given as the sum of an increasing term and a decreasing ring, consider the limit where the magnetic field strength increases to infinity, increases at first, reaches a maximum value, and then decreases. Then, the arc current cannot cross the magnetic field, so the arc becomes parallel to the magnetic field.

That is, if a line passing through the torch tip Q and parallel to the magnetic field vector is drawn and the point where it intersects with the x-7 plane is P, the arc will be located on the straight line QP and the arc spot will be at the P point.

Through calculation, it was found that the trajectory of the arc spot starting from point 0 and reaching point P at B→■ is a semicircle with OP as the diameter, as shown by dotted line 4 in the figure.

If the length of QO is L, the radius of this circle is θ.

If the arc spot works up to 8 points with a certain magnetic field strength B, and the angle between OR and SR at that time is α, then α and B
The relationship between is shown in the figure.

In Figure 2, the horizontal axis corresponds to the magnetic field strength, α=
The magnetic field strength at 90° is expressed as B2O1, and the magnetic field strength is normalized to this value.

Now, considering an alternating magnetic field expressed as Bs1nωt and assuming that the arc current is a direct current, the arc spot is at α=0, that is, at the origin in FIG. 1 at t-O.

When 0<1<-1, the arc spot moves on the arc indicated by the dotted line in a direction in which α increases by 2ω, and at t=π/2ω1, the arc spot reaches, for example, 8 points.

When π/2ω<1<π/ω, the arc spot returns from point 8 to point 0 on the circular arc indicated by the dotted line.

At t=π/ω, it is again at the 0 point.

−〈t≦π/ω, the arcsbot ω moves in the same way at S′1 on the dotted line indicated by 4/f in Figure 1 in the range of negative α, and returns to the origin O at t=2π/ω. I'll be back.

It will be easily understood that thereafter, the arc spot reciprocates on the circular arc at a time period of 2π/ω.

To know the value of α when B is given, the value of B2O must be known, but B9o depends on the angle θ between the magnetic field and the two axes, arc current ■, gas atmosphere, gas flow rate button, torch design, etc. is involved, and it is difficult to obtain it analytically.

Determination of B2O must be determined experimentally.

That is, starting from O and increasing the value of B, α-900
What is necessary is to measure the value of B that becomes B2O.

In order to clarify the difference between the conventional arc oscillation method and the present method, the motion of the arc spot will be compared between the case of θ=- and the case of 0 in FIG. 1.

θ-1 is the conventional method, θ\- is the method 2 of the present invention It is.

In the magnetic field of θ-1, no force is generated to move the arc in the X direction, so the arc spot can only move along the y axis.

In an alternating magnetic field, it performs reciprocating motion around the origin O on the y-axis.

As the magnetic field strength increases, the oscillation amplitude also increases.

The velocity of the arc spot is small at both ends and large at the center, so the heat input distribution due to the arc has peaks at both ends.

On the other hand, in θ\-, the arc spot moves on the circumference of a circle on the x-y plane with the center at point R, that is, X = -1 θy = o, z = 0, and radius 110. In an alternating magnetic field, it reciprocates on this circular plate with the zero point as the center.

If we consider the motion of the arc spot by projecting it onto the y-axis,
In the case of BζB90, the amplitude of the arc spot increases as B increases, but reaches a maximum when B=B9o, and the amplitude is Ltanθ.

When B > B 90, the amplitude projected on the y-axis does not become larger than L tan θ even if B is increased.

However, in this case, the turning point L of the oscillating arc
L is the maximum amplitude point y"" tanθ, and y=tanθ
It is located 2 degrees inside, and this turning point is the point of maximum heat input.

The larger B is, the closer the maximum point of human heat is to the X axis.

One of the features of the present invention is that the heat input distribution can be controlled by changing the magnetic field strength while the heat input is constant during heat input.

There are various methods of creating an oblique magnetic field, but a simple method is shown in FIG.

In FIG. 3, 1 is an arc torch, 2 is a metal material, and an arc is generated between the arc torch 1 and the metal material 2.

Buttons 5 and 6 are conducting wires for passing current, and both extend perpendicularly to the plane of the paper.The plane that includes both conducting wires 5 and 6 is the center axis of the torch, which is represented by a dashed line. It is arranged so that it intersects at an angle that is not perpendicular to .

If current is passed through the parallel conducting wires 5 and 6 so that the directions of the currents maintain a reactive relationship with each other, a magnetic field obliquely intersecting the arc will be generated in the space where the arc occurs.

Dotted line 7 shows the conceptual state of the magnetic lines of force of the magnetic field created when a current flows through the conductor 6 from the front to the back of the paper, a current flows from the back to the front of the paper through the conductor 5, and the absolute values of the currents are equal. It shows.

Although the magnetic field is not spatially uniform, there is a magnetic field that crosses the arc obliquely.

The angle between the arc and the magnetic field can be changed by changing the positions of the conductor wires 5 and 6.

The magnetic field strength can be changed by changing the current value flowing through the conductive wires 5 and 6.

The magnetic field strength created by currents flowing in two parallel conductors in opposite directions can be easily calculated using Ampere's circuit law from electromagnetic theory.

If the distance between the two conductors is a1 and the absolute value of the flowing current is 3, then the magnetic field strength B at the center of the conductors is given by B = 0.8 x IB / a (Gauss).

However, IB is a value in ampere, and a is a value in reserve.

The vector direction of the magnetic field at the center is perpendicular to the plane containing the conductors 3 and 4.

Specific examples relating to the present invention are shown below.

Example (Slab melting and care experiment using an oscillating arc using an oblique magnetic field) An experiment was conducted in which the plasma arc was oscillated in an arc shape using the oblique magnetic field generation method shown in Figure 3 to melt and care for the surface of a stainless steel slab. went.

Experimental conditions Molten metal material: 5US304 slough plasma Arc current: 300AD, C Plasma gas: Ar + 10%Hz 101/wa
rn Spacing between conductor wires for magnetic field generation: 4 crn Current for magnetic field generation: 430 A, 50 Hz A-C Torch tip distance between metal material surfaces: 9 cm Metal material moving speed: 20 cm1 Results The following numerical values were obtained as a result of magnetic field measurement.

Magnetic field generated at the center between the conductors, B = 85 Gauss Intersection angle between the A arc and the magnetic angle θ = 400 Magnetic field strength that gives B90 B9o = 40 In the wind melting care experiment, as the stainless steel slab piece was moved, it melted with good surface quality. A reconsolidation zone was formed with a width of 6 cm.

After the treatment, the slab was cut and the structure was observed. As a result, the uniformity of the penetration depth in the direction of the melt width was good.

As shown in the examples, the method of the present invention is not only useful as a method for treating the surface of a metal piece by melting it, but is also extremely effective as a method for heat treatment and other methods for applying heat to a wide area.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the movement of an arc spot in an oblique magnetic field, and FIG. 2 is a diagram illustrating the relationship between the moving angle of the arc spot and the magnetic field strength. FIG. 3 is a diagram showing the principle of an example of the oblique magnetic field generation method of the present invention. 1... Arc torch, 2... Metal material, 5, 6...
Conductor, 7... lines of magnetic force.

Claims (1)

[Claims] 1. A method of spatially moving an arc or plasma arc by applying an external magnetic field to the arc or plasma arc. An arc oscillation force method characterized by causing an arc or plasma arc to move in an arc by passing currents flowing in opposite directions through two parallel conducting wires.