JPS5827035B2 - Overlay welding method using a strip electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing a weld bead in a strip electrode type overlay welding method.

As overlay welding methods using strip electrodes, (4) a submerged arc welding method and (B) a method utilizing resistance heat generation of slag are known, and the present invention relates to method (B).

(B) In implementing the law, the
(Japanese Patent No. 1,080,698) or other improved fluxes proposed by the present applicant are used.

Then, the flux is spread in advance in the forward direction of the welding direction, and the slag bath is held before being melted one after another, and the strip electrode and base metal are melted by the resistance heat generated by the slag. Shown in Figure 1.

In Fig. 1, 1 is a strip electrode, 2 is a welding bead, and 3 is a strip-shaped electrode.
4 means a molten pool, 4 means a base material, 5 means a flux, arrow A shows the feeding direction of the strip electrode 1, and arrow B shows the welding progress direction.

By the way, as I accumulated experience with such overlay welding, I learned that the shape of the weld bead 2 can be greatly influenced by certain factors.

It is the molten pool 3 that directly determines the shape of the weld bead 2.
However, when we closely observed the condition of pool B, we found the following.

Figures 2 to 4 show a situation diagram A of the pool 8 seen from diagonally above the rear part in the direction of welding progress, and a bead 2 formed at this time.
This is a contrasting cross-sectional view B showing the shape of , and C in the figure means the flow direction of the molten metal.

Further, a white arrow F indicates the magnitude and direction of a force (electromagnetic force) due to the influence of magnetism, which will be described later.

FIG. 2 shows the case where a wide and good bead is obtained, and the molten metal flows outward and evenly on both sides.

Of course, if this flow is too strong, the center of bead 2 may become depressed and split into two peaks on the left and right.

However, in FIG. 3, the flow to the left and right is uneven, and the shape of the bead 2 is asymmetrical, as if the molten metal was pulled in the direction where the flow was stronger.

When this tendency becomes noticeable, overlap tends to occur on the left side of the figure, and undercut tends to occur on the right side of the figure.

Figure 4 shows the case where the flow of molten metal is closer to the center.
Undercuts tend to occur at both ends of the bead 2.

There is also a tendency for slag to flow backwards, sometimes causing arcing.

Convection due to the generation of high heat may also be the cause of such a flow in the melt pool, but convection is thought to mainly cause a flow in the vertical direction, and the flow in the horizontal plane as shown in the figure is , it is presumed that this is due to another cause, namely electromagnetic force.

Therefore, we considered the influence of electromagnetic force on the flow of molten metal, and as a result of various studies, we came up with a means to ensure the flow situation as shown in Figure 2 as stably as possible, and we are now completing the present invention. reached.

That is, the internal welding method according to the present invention is a method in which a strip electrode fed in the direction of the base metal is welded while being surrounded by a magnetic frame with a notch on the rear side in the direction of welding progress, and electromagnetic force is actively applied. By controlling the temperature, a stable melt pool shape can be maintained.

The structure and effects of the present invention will be explained below while referring to the circumstances leading to the completion of the present invention.

First, the mechanism by which the flow of molten metal in the molten pool is caused by electromagnetic force can be considered as shown in FIG.

The figure shows the case under the condition of DC reverse polarity, and the current flows from the electrode 1 into the molten pool 3 and further into the base material 4, but is almost evenly distributed directly below the electrode 1.

However, some parts of the melt pool 8, as shown by arrow 1 in FIG.
It flows inside toward the rear in the direction of welding progress.

If we now consider an upward magnetic field H, an electromagnetic force F in the direction shown in FIG. 5 will be generated according to Fleming's left-hand rule.

That is, it has been found that the movement of the molten pool is essentially caused by the current flowing within the molten pool and the magnetic field in the thickness direction.

It has also been found that the direction and magnitude of the force depend not only on the strength of the current but also on the direction and magnitude of the magnetic field H.

Therefore, in order to further confirm these points, an experiment shown in FIG. 6 was conducted.

That is, the test plate 4' is placed on the pedestal 5 and overlay welding is performed in the same manner as shown in FIG. passed the electric current.

Therefore, a magnetic field as shown in 7 was generated in the molten pool.

Since all of these magnetic fields are directed upward, the electromagnetic force F shown in Figure 5 becomes extremely large, causing the molten pool to deflect largely to the left as in the example in Figure 3, and to the right of the formed bead, there is an underside. A cut occurred.

Next, experiments shown in FIGS. 7 and 8 were conducted with the same purpose.

In this experiment, a coated power cable 6 was placed on the lower surface of the test plate 4', and grounding by the power cable 6 was performed at one location on the front side (Figure 7) and the rear side (Figure 8) in the welding direction. It was made in a similar manner.

In each figure, 8 indicates the ground point, F, I. The suffixes L and R attached to each symbol H represent the left side and right side, respectively, when viewed from the rear side in the welding direction.

Also, in both figures, A is a plan view of the welding work from above, and B
is a sectional view of the welding bead 2, C is an explanatory diagram showing the direction of the magnetic field, and D is an explanatory diagram showing the direction of action of electromagnetic force.

Looking at FIG. 7, a clockwise magnetic field is created as shown in C, and because of this magnetic field, the electromagnetic force is spread outward as shown in D.

Therefore, the molten pool 3 spreads evenly over the entire surface as shown in A, and a good bead as shown in B is obtained.

On the other hand, when looking at FIG. 8, a counterclockwise magnetic field is formed as shown in C, and the electromagnetic force is concentrated toward the center as shown in D.

Therefore, the molten pool 3 gathers in the center as shown in A, and the bead formed is in the center as shown in B, and there are many undercuts on both sides.

These experiments revealed that the magnetic field generated near the molten pool has a significant effect on the behavior of the molten pool.

At the same time, it has also been found that completely opposite results can be obtained depending on the direction of action of the magnetic field.

Therefore, in order to always maintain the spread of the melt pool in an optimal condition, a magnetic field must be actively created by lateral means.
In response to the conclusion that it is necessary to ensure an electromagnetic force that always spreads in the width direction of the electrode by the magnetic field, we have come to propose the welding method shown in FIG. 9.

That is, the frame member 9 arranged so as to surround the strip electrode 1 is made of a magnetic material, and because of the current flowing in the direction of the arrow in the electrode 1, lines of magnetic force H as shown by the dashed line are formed.

However, a notch indicated by 10 is formed in the frame member 9 on the rear side in the direction of welding progress, and the lines of magnetic force formed around the frame member 9 are transmitted to the molten pool 3 at the notch 10, and are transferred to the frame member 9 again. return.

Therefore, when viewed from behind the welding line, downward magnetic lines of force HR are formed on the right side, and upward magnetic lines of force HL are formed on the left side, and this state corresponds to the state shown in FIG. 7C.

As a result, as shown in the figure (or as shown in FIG. 2A), an electromagnetic force FL t "R, which spreads in the width direction is obtained, and the state of the molten pool 3 can be maintained in an optimal state.

Also, as a result of such adjustment, if FL or FR becomes too large, problems such as the molten metal splitting into two parts and the center of the beat becoming depressed, as mentioned in Fig. 2A, will occur.
In that case, the FL and FR may be lowered by raising the position of the frame member 9 and weakening the magnetic force.

Furthermore, the above explanation relates to adjustment when the absolute values of FL and F8 are the same size, but when their sizes are different as shown in FIG. 3, the frame member 9 may be moved parallel to the band surface of the band-shaped electrode to either the left or the right, and this moving direction is a direction in which support by magnetic force is required to be less.

That is, when the force on the left side is large as shown in FIG. 3, for example, it is necessary to strengthen the magnetic force on the right side, so it is necessary to move the frame member 9 to the left side and make adjustments such as increasing the lines of magnetic force on the right side.

Although the illustrated frame member 9 has a rectangular cross section, its shape is not limited at all as long as it has a notch at the rear.

Each of the above explanations was for overlay welding with reverse polarity,
In the case of positive polarity, the direction of the current is reversed and the direction of the electromagnetic force is also reversed accordingly, but it is clear that there is no need to modify the requirements of the present invention, and the same applies to the case of AC welding. The effects of the present invention can be obtained without any inconvenience.

Since the present invention has been exploited as described above, the shape of the molten pool can be maintained evenly on the left and right sides in band electrode overlay welding that utilizes the resistance heat of slag, and the shape of the weld bead can be stabilized. It was very successful.

[Brief explanation of the drawing]

Fig. 1 is a perspective view schematically showing the band electrode type overlay welding to which the present invention is applied, Figs. 2 to 4 are explanatory diagrams showing fluctuations in the molten pool, and Fig. 5 is the influence of electromagnetic force on the molten pool. FIG. 6 is a perspective view showing the rotation, FIGS. 7 and 8 are explanatory views showing changes in electromagnetic force when a power cable is used, and FIG. 9 is an embodiment of the present invention. 1... Strip electrode, 3... Molten pool,
9... Frame member, 10... Notch.

Claims (1)

[Claims] 1. In an overlay welding method in which a strip electrode and a base metal are melted by resistance heat generation of slag, the strip electrode fed toward the base material is made of a magnetic material having a notch on the rear side in the welding direction. An overlay welding method characterized by welding while being surrounded by a frame. 2. The overlay welding method according to claim 1, wherein the overlay welding is carried out while moving the magnetic frame from side to side parallel to the band surface of the band-shaped electrode depending on the condition of the molten pool.