JPS61137676A - Back bead control method in one side welding - Google Patents

Abstract

PURPOSE:To control a back bead width uniformly with the prescribed width by detecting the current between the base metal under welding and a metallic plate and by controlling the current thereof in a one side welding. CONSTITUTION:A convertor 7 converts into a DC signal the current I which is between a base metal 1 and backing plate 3 detected by a current detector 6. The current signal outputted from the convertor 7 is inputted into a comparator 9 with the necessary signal for controlling only being taken out by a filter 8. The current signal inputted into the comparator 9 is compared with the preset reference current signal 10 according to the prescribed back bead width by the correlation between the back bead width and base metal 1 and the current I of the backing plate 3. The comparator 9 outputs to a welding power source 5 via an integrator 11 the differential signal of the above both current signals. The welding current is controlled by the welding power source 5 so as to make the inputted differential signal in zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a back bead control method in single-sided welding, particularly in single-sided welding of large plates.

[Conventional technology]

Single-sided welding is widely used because it performs welding from the surface of the base metal without inverting the base metal, produces a good back weld, and can be welded efficiently and economically.

The width of this back bead is rounded to create uniformity in the bevel condition, and to prevent this unevenness, if there is a gap, place a seal bead and create a standard bevel shape. Weld closer.

[Problem that the invention seeks to solve]

However, matching this standard groove shape requires a great deal of skill, and when welding a large steel plate, such as a steel plate for a ship's hull, on one side, it is difficult to see the back side, which makes it difficult to grasp the situation during welding. The problem is that it is difficult to control the width of the bead uniformly.

The purpose of this invention is to propose a back bead control method in single-sided welding that can improve the above problems and uniformly control the width of the back bead.0 [Means for solving the problems] The back bead control method in single-sided welding of the present invention is performed in single-sided welding in which an inorganic material such as flux is brought into close contact with the back side of a base metal steel plate by a metal plate and welded from the front side of the base metal. This is a control method in which the width of the back bead is kept constant by detecting the current generated and controlling this current.

〔Example〕

FIG. 1 shows a principle diagram of a single-sided welding method by submerged arc welding using two electrodes to complete welding in a single pass. In the figure, (11 is the base material, (2) is an inorganic material such as flux that is adhered to the backing metal plate (31) on the back side of the base material flll, (4A), (4B) is an electrode, (5) is a welding power source, (6) is a current detector.

In the single-sided welding shown in the figure, the current between the backing metal plate (3) and the base metal (11) is zero at the start of welding.

After welding starts, when the back bead is well exposed, the base material f
The arc leaking through the gap 11 reaches the backing metal plate (3) and generates a current between the base metal (1) and the backing metal plate (3).

The current ■ between this base material (11) and the backing metal plate (3) was measured with a current detector (6), and the relationship between this current I and the back bead width was investigated. The results are shown in Figure 2. As shown in the figure, the base material (
It is clear that there is a good correlation between the electric current work and the back bead width between 1) and the backing metal plate (3). It was found that it is possible to control

FIG. 3 shows an embodiment of a device used for this method of controlling the back speed in single-sided welding. In the figure, (7) is a converter that converts the current (2) between the base material (11) and the backing metal plate (3) detected by the current detector (6) into a DC signal.

This converter (7) is necessary when an AC power source is used as the welding power source (5), but is unnecessary when the welding power source (5) is a DC power source. The current signal output from the converter (7) is passed through a filter (8) to extract only the signals necessary for the control and input to the comparator (9). The current signal input to the comparator (9) is determined to a predetermined back bead width based on the correlation with the back bead width shown in Figure 2 and the current between the base material (1) and the backing metal plate (3). It is compared with a reference current signal 11rm set in advance accordingly. A comparator (9) outputs a deviation signal between the two current signals to a welding power source (51) via an integrator a1).
Output IC. The welding power source (5) controls the welding current so that the input deviation signal becomes zero. That is, the base material (1
) and the current signal between the backing metal plate (3) and the reference current signal a1
control so that they always match. In this embodiment, the welding current is controlled, but it goes without saying that any welding parameters such as welding speed and arc voltage may be used as long as the detected current signal can be controlled.

As mentioned above, by controlling the current between the base metal (1) and the backing metal plate (3) so that it is always constant, single-sided welding can be performed with a constant back bead width depending on the current welding process. This makes it possible to easily control the back bead width.

〔Effect of the invention〕

As explained above, in single-sided welding, the current during welding between a base metal and a metal plate backed by an inorganic material such as flux on the back side of the base metal has a good correlation with the back bead width. Based on this finding, by detecting and controlling the current between the base material and the metal plate during welding, it is possible to uniformly control the back bead width to a predetermined width without requiring any skill. Furthermore, by detecting and controlling the current between the base material and the metal plate during welding, the back bead width can be uniformly controlled, making it easy to do online (the effect is great because the back bead width can be controlled).

[Brief explanation of the drawing]

Figure 1 is a principle diagram of the single-sided welding method, Figure WX2 is a characteristic diagram of the current between the base metal and the backing metal plate via an inorganic material, and the back bead width, and Figure 3 is an example of the present invention. FIG. 2 is a block diagram of the device used. (1)...Base material, (2)...Inorganic material, (3)...
Metal plate, (4A)t (4B)...electrode, (5)...
・Welding power source, (6)...Current detector, (7)...Converter, f81...Filter, (9)...Comparator, αυ
...Reference current signal, key...integrator.

Claims (1)

[Claims] In single-sided welding, in which an inorganic material such as flux is adhered to the back side of the base metal using a metal plate, etc., and welded from the front side of the base metal, the current between the base metal and the metal plate during welding is detected and this current is controlled. A back bead control method in single-sided welding characterized by making the back bead width constant by