JPH03258468A - Impeder for tube manufacture welding - Google Patents

Abstract

PURPOSE:To use the impeder for tube manufacture welding as an impeder core having the high service life by using a foil body made of amorphous metallic material or the whole surface of an extra fine wire subjected to insulation coating as a core. CONSTITUTION:Since a filmy amorphous alloy 10 or a wire-shaped amorphous alloy is subjected to insulation coating 11 on the whole surface for each simple substance thereof, its rustproofing performance is excellent. Accordingly, it is not necessary to add Cr to the amorphous alloy material 10 and a material design considering only magnetic characteristics is also made possible. Since the impeder for tube manufacture welding has high cooling power, even when load of high frequency is high, it can be used as the impeder core having the high service life without burning the amorphous alloy having satisfactory magnetic characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an impeder used in a method of manufacturing ERW steel pipes by joining metal pipes by high frequency welding, and particularly relates to an impeder for manufacturing steel pipes for mechanical structures, raw pipes for drawing, etc. The present invention relates to an impeder suitable for manufacturing high frequency electric resistance welded steel pipes having a large /D (thickness/outer diameter).

BACKGROUND OF THE INVENTION High frequency electric resistance welding is the most efficient cold pipe welding process and is therefore widely used.

To join metal pipes by high-frequency electric resistance welding, the joint surfaces of the metal pipes are shaped into an oven pipe using a roll or the like so that the joint surface forms a V-shape with the apex at the welding point. It is a distant relative that is heated by passing a high-frequency current and then rolling the abutting portion that reaches the welding temperature with a rolling roll.

Figure 3 shows an example of the manufacturing method for high-frequency ERW steel pipes.
Skelp (1) with a tubular bottom shape is a work coil (2)
They are heated by eddy currents generated by passing a high-frequency current through them, and are pressure welded with welding rolls (3).

In this high-frequency TLA welding, the impeder used for the purpose of improving welding thermal efficiency by concentrating eddy current at the welding point is an insulating impeder case (4
) has a built-in core (5) made of magnetic material, and is placed inside the tube via a mandrel (6) having a water-permeable structure.

That is, the core (5) is cooled by cooling water supplied from the mandrel (6) in order to maintain its performance during pipe making.

The purpose of this impeder is to improve welding thermal efficiency by exciting the core (5) with a high-frequency current flowing through the work coil (2), but the performance of the impeder is generally determined by the characteristics of the core (5). As for characteristics, it is required to have high magnetic permeability and high saturation magnetic flux density.

That is, in order to improve the welding thermal efficiency of the electric resistance welded pipe, it is necessary to pass more magnetic flux through the impeder core (5).

The amount of magnetic flux φ passing through the core (5) is expressed as the product of magnetic flux density B and cross-sectional area A, as shown in equation (1) below.

$=BXA... (1) As the core (5) of a conventional impeder, a ferrite core (5'), which is an oxide magnetic material made by sintering powdered oxide, is used as shown in Figure 4. Ta.

In the case of high-frequency ERW steel pipes, the welding current is a high-frequency large current, so the magnetic flux density of the ferrite core (5') reaches saturation.
In particular, when the diameter of the tube is reduced, the cross-sectional area A' of the ferrite core (5') also becomes smaller, and the saturation magnetic flux density is reached with a small welding current. In this case, as can be seen from the above-mentioned (1-in type), the amount of passing magnetic flux also becomes saturated and the welding thermal efficiency decreases.

As a countermeasure to this problem, ferrite core manufacturers have investigated the material properties in order to increase the saturation magnetic flux density B's of the ferrite core, and it has become possible to obtain a characteristic of B's = 0.5T, but the condition is still unsatisfactory. Far from it.

Materials with higher saturation magnetic flux density than ferrite cores include metallic magnetic materials such as silicon steel or amorphous alloy steel.
At commercial frequencies (50-60Hz), the thickness is 0.3~
Metal magnetic material rolled and heat-treated to 0.35 mm is used as the iron core of transformers.

In the case of high-frequency electric resistance welded steel pipes, the welding current is a high-frequency large current, so the impeder is exposed to a high frequency and high magnetic flux density, and a large eddy current is also generated in the core, causing a rise in temperature.

In addition, the generated eddy current is proportional to the square of the magnetic flux density and the square of the frequency, and the frequency f is f-10 to 500 KHz.
In high-frequency ERW steel pipes, the amount of heat generated by the core is extremely large compared to that used at commercial frequencies.

For this reason, in the case of metallic magnetic materials that generate a large amount of heat due to eddy currents, the temperature of the impeder core cannot be maintained below the Curie point by cooling it by flowing cooling water, which is usually done industrially, and ferromagnetism disappears. Therefore, it could not be used as the core of an impeder.

This is high frequency! This is why ferrite cores were used in the manufacture of sewn steel pipes, as they generate less heat due to eddy currents in high frequency ranges.

On the other hand, as an impeder with good welding heat efficiency in the production of high frequency xi steel pipes, for example,
There is an impeder published in 7.

This is a combination of blocks made by laminating amorphous metal alloy material (hereinafter referred to as "amorphous alloy") (10') using an insulating adhesive (11') as shown in Figure 2. Amorphous alloys are similar to silicon steel, have a much higher saturation magnetic flux density than ferrite, and have higher magnetic permeability than silicon steel, so they can obtain a large magnetic flux density even in a small magnetic field, so they are different from conventional ferrite cores. Impeders with better welding efficiency can be created.

Problems to be Solved by the Invention However, the specific resistance of the amorphous alloy is 125XIF'Ω
-cm is high compared to 45X10-'Ω-Cm of 3% silicon steel, but extremely low compared to ferrite core,
Generates heat when used.

As a countermeasure against this problem, a method is known in which, for example, the core cross-sectional area is limited to 50 mm or less to enhance the cooling effect and improve durability (Japanese Patent Publication No. 61-31959).

However, the internal cross-sectional area of the vibrator is small like a small-diameter thick-walled tube,
When welding an impeder with a size that cannot be filled with a large amount and requires a large load power, the metal insulation film may break down due to the heat generated due to insufficient cooling, making it impossible to obtain the expected effect. occurs.

This invention aims to provide an impeder made of an amorphous metal material that has a structure that does not cause insufficient cooling even when a large high-frequency load is applied to the impeder, such as in a small-diameter thick-walled pipe. be.

Means for Solving the Problems As a result of various studies on means for solving the above-mentioned problems, the inventor found that: (1) The smaller the number of layers of the amorphous alloy laminate and the smaller the cross-sectional area of the laminate itself, the higher the high frequency. It is able to withstand loads, and ■The insulating film also has low thermal conductivity, so the heat generated internally accumulates and is more difficult to escape than a laminate.
Furthermore, it was discovered that the arrangement and cross-sectional shape of the laminate do not need to be specified, and that the same effect on welding efficiency can be obtained even if the laminate is divided in the thickness direction. They discovered that the best cooling performance was achieved by attaching an insulating film directly to the impeder case.

That is, the gist of the present invention is an impeder characterized in that a box made of an amorphous metal material or an ultrafine wire whose entire surface is coated with insulation is used as the core.

The thickness of the amorphous alloy box (film), which is an amorphous metal material, or the wire diameter is not particularly limited, but considering the amount of heat generated), the deviation is 60 μm to 2D.
1irn is practical.

That is, if the thickness of the box or the wire diameter is set to 60 μm or less, a highly cooling type impeder (with extremely low heat generation per unit surface area), which cannot be obtained with conventional laminated impeders, can be obtained. It should be noted that if the foil thickness or wire diameter is less than 20 μm, it is difficult to produce it industrially.

Both the film-like amorphous alloy and the wire-like amorphous alloy are directly attached to the impeder case. In that case, since the films or wires themselves are attached at desired intervals, the cooling capacity determined by the contact area with the cooling water supplied to the impeder case is greater than that of the conventional laminated type.

Incidentally, the gap between the film-like or wire-like amorphous metals coated with an insulating coating is not particularly limited, but it is practical to have a gap of 5 μm to the thickness of the amorphous alloy. In other words, if the gap between the alloys is set to 5 μm or less, the gap will be on the same level as the thickness of the boundary layer, and the fluid resistance will be large, making it difficult for cooling water to flow.

Furthermore, if the gap between the alloys is made larger than the thickness of the amorphous alloy, the filling rate as an impeder will be low and no practical effect can be obtained.

Film-like amorphous alloys and wire-like amorphous alloys have excellent rust prevention performance because the entire surface of each individual piece is coated with insulation.

Therefore, it is not necessary to add Cr to the amorphous alloy material, and it is possible to design the material by considering only the magnetic properties.

Embodiment FIG. 1 is a sectional view showing an embodiment of the present invention.
(11) is a film-like amorphous alloy, and (11) is an insulating coating film.

In other words, here we show a case where five film-like amorphous alloys whose entire surfaces are coated with insulation are used.
Each amorphous alloy is attached to the impeder case through a gap (12).

The insulating coating film (11) can be formed, for example, by electrodeposition. For reference, the insulation of the conventional laminate shown in FIG. 2 is performed by vacuum immersion liquid sintering of epoxy resin.

In the case of the core of the present invention, which is constructed by stacking five amorphous alloys (10) with an insulating coating applied to the entire surface with a gap (12) in between, its cooling capacity is higher than that of the conventional five-layer laminated core shown in Figure 2. About 3 times better.

Since the practical laminated type stacks about 1.00 sheets of amorphous alloy, there is a large difference in cooling performance from the conventional laminated type.

Table 1 shows a comparison between the impeder of the present invention and the conventional multilayer impeder. Note that the insulating coating in this invention is applied by electrodeposition coating,
Conventional laminate insulation was provided by vacuum immersion liquid sintering of epoxy resin.

As is clear from Table 1, both impeders made of film-like and linear amorphous materials could be used without burning out because the cooling capacity was superior to that of conventional products even under severe high-frequency loads.

As explained in detail below, the impeder for cold pipe welding of this invention has a large cooling capacity, so even when high frequency loads are large, the amorphous alloy with good magnetic properties does not burn out, and it has a long lifespan. It has the excellent effect of being able to be used as an impeder core.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a sectional view showing an example of a conventional laminated core, and Fig. 3 is an example of a method for manufacturing a high-frequency electric resistance welded steel pipe, which is the subject of this invention. Fig. 4 is a schematic diagram showing Fig. 3 I when using a ferrite core.
It is a sectional view on the V-IV line. 4... Impeder case 6... Mandrel 1
0...Film-like amorphous alloy 11...Insulating coating film 12...Gap Figure 1 Section 3 Figure 4 Figure 2

Claims (1)

[Claims] In an impeder for cold pipe welding that has a core made of magnetic material built into the impeder case and has a structure that supplies cooling water into the case, the entire surface of the box made of amorphous metal material or the ultrafine wire is insulated. An impeder for cold pipe welding characterized by using a coated material as the core.