JPS58202992A - Arc welding electrode - Google Patents

Abstract

PURPOSE:To reduce the initial preheating time of base metal and to improve the quality in the structure of weld beads stably in the stage of using the thick base metal by using a coated arc welding electrode by forming the diameter of the core wire in the forward end part of the welding electrode convergent. CONSTITUTION:It takes time in preheating thick base metal to the adequate welding temp. thereof and the arc does not stabilize during this time, thus blowholes and cracks are generated in weld beads and the structure of the beads is inferior in quality in the stage of welding said metal by using a coated arc welding electrode. The forward end part 11b of the core wire 11 of said welding electrode in this case is formed to the diameter convergent in a step part 11a. Since the part 11b has the smaller diameter, the current density therein is large in the stage of welding, hence penetration is faster. The base metal is preheated initially up to the welding temp. in a short time, the arc is stabilized in the earlier time and the weld beads have the better quality in structure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding rod that improves the quality of the pead structure by shortening the initial preheating time for arc welding.

As arc welding rods, there are coated arc welding rods.

A conventional coated arc welding rod of this type is formed by covering a core wire 1 having a uniform standard thickness over its entire length with a coating material 2 having a substantially uniform thickness, as shown in FIG.

This coated arc welding rod is supported by a welding holder connected to a power source, and the base metal and the welding rod are melted by the heat of the arc generated by shorting the base metal connected to the ground side of the power source. Covered arc welding is done. However, since shielded arc welding is generally used for thick base materials,
It is necessary to make the initial preheating time, which is the time it takes for the part of the base metal to be welded to reach the appropriate welding temperature due to the heat input effect of the arc, to a certain extent. During this time, the arc is not stable, so if welding is started before the required preheating time has elapsed, there will be insufficient heat input, which will cause blow holes and cracks in the placed bead, resulting in poor welding quality due to defects in the bead structure. Easy to occur. In this case, it is possible to shorten the preheating time by increasing the current density, so increasing the welding current can be considered for that purpose, but since there is an appropriate value for the welding current, it is appropriate to increase the current only in the initial stage of welding. isn't it.

Therefore, in order to improve the drawbacks of such coated arc welding rods, the one shown in Fig. 2 has been proposed. The coated arc welding rod shown in FIG. 2 has a blind hole 1t provided at one end of the core wire 1, and the coating material 2 is also filled in the blind hole 1a. By reducing the cross-sectional area of the core wire near the tip in the blind hole 1a and increasing the initial current density, the initial preheating time can be shortened.
This is intended to improve welding quality. However, since a deep blind hole was created along the axis of the relatively thin core wire and the coating was then filled into the hole, the manufacturing process was complicated and costly. The present invention was made in view of these conventional problems, and aims to solve the above problems by forming the tip of the core wire of an arc welding rod into a tapered shape.

The present invention will be explained below based on the drawings.

FIG. 3 is a diagram showing an embodiment of the present invention.

First, let me explain the composition: Heart! l1lFi, a stepped portion 11& is provided near one tip, and the thickness of the tip portion 11b beyond the stepped portion 11& is formed to be thinner than the thickness of the standard dimension up to the other end. The adherend 12 is placed along the shape of the core wire, and the whole is stepped and tapered.

1; The core wire 11 at the thick end of the coated arc welding rod constructed as described above is supported by a welding holder, and the base metal connected to a power source is welded in the same manner as in the conventional method.

Compared to conventional arc welding rods of uniform thickness with the same standard dimensions, the thin tip part has a higher initial electric current M+ density and larger energy per unit area, so the thin tip part 11b of the core 4111 melts It's hard to fit in.

Therefore, the spinning preheating time after the arc occurs ends in a very short time, and the arc stabilizes at an early stage. In this way, the welding rod in the standard dimension part after the tapered tip can always form a bead in a stable arc state, and there is no risk of blowholes or cracks occurring due to unstable arc as in the past. . Moreover, the tip portion 11b is connected to the core wire 1.
Since the entire outer diameter of 1 is made thinner in that part and the cross-sectional area is reduced, it is much easier to manufacture than other conventional products that have a blind hole in the tip as shown in Figure 2. It can be mass-produced at low cost.

FIG. 3 shows another embodiment of the invention.

In this embodiment, a core wire 21 and a coating material 22 covered therewith are used.
One tip portion 22b of 1 is provided with a stepped portion.
It is formed into a tapered shape, with the thickness gradually decreasing. In addition to the same effects as in the first embodiment, this embodiment also prevents non-uniformity of the liquid reservoir location due to sudden changes in the core 1i1j21.

As explained above, according to the present invention, the configuration is an arc welding rod characterized in that the tip of the core wire of the arc welding rod is tapered. The effect is that arc welding in which the expected heating time for the /I period is shortened and the structure quality of the weld bead is improved can be provided extremely easily and at low cost.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional coated arc welding rod with a uniform thickness, Figure 2 is a sectional view of a main part of another conventional coated arc welding rod with a blind hole at one tip, and Figure 3 The figure is a sectional view of a main part of one embodiment according to the present invention, and FIG. 4 is a sectional view of a main part of another embodiment according to the invention. 11.21・・・・・・ Core wire 11 &・・・・・・・・・・・・・・・Step part jlb,
22b...Tip IL22...Coating material 2

Claims (1)

[Claims] An arc welding rod characterized by a tapered core wire tip.