JPS59101289A - Detection of molten metal position in electroslag welding - Google Patents

Abstract

PURPOSE:To detect exactly the position of the weld metal at the end part on base metals and to automate electroslag welding by positioning a probe in a slag bath, detecting the potential difference between the probe and the base metal and comparing the same with a reference voltage. CONSTITUTION:A probe 9 is provided above base metals 1, 2, apart at a spacing lfrom the upper part of the metals 1, 2. The probe 9 and the metal 1 are connected by means of lead wires 10, 11 to a voltmeter 12. A slag bath 8 ascends on progression of welding and contacts with the tip of the probe 9, then the probe 9 is dipped in the bath 8 and the potential difference between the probe 9 and the metal 1 is measured by the voltmeter 12. If the potential difference between the probe 9 and the metal conforming the distance between the probe 9 and a molten metal 7 is beforehand investigated empirically and is set as a reference voltage, the output is obtd. always at the specified distance between the probe 9 and the metal 1 irrespectively of the depth in the bath 8 and the position of the molten metal 7 is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the position of molten metal in electroslag welding.

The Elec2 slag welding method is a welding method that utilizes the resistance heat of a slag bath held on the top surface of molten metal, but the depth of the slag bath is not constant depending on the welding conditions.
It is difficult to directly detect the location of molten metal based on its appearance, etc. For example, when electroslag welding a vertical joint, it is best to end the welding when the molten metal reaches a position flush with the top of the base metal, which is efficient because there is no waste of welding material, and it also looks good. Become something. However, as mentioned above, mol/ii! Since it is difficult to detect the metal position, conventionally, a tab or the like is provided and welding is carried out to the top of the base metal, and after welding is completed, the excess metal is melted and polished to finish. As a result, the current situation is that the process is complicated and efficiency is reduced.

In addition, in the welding of vertical and horizontal stacking platform members as proposed by the present inventors in Japanese Patent Application No. 57-61691, after electroslag welding the vertical members, the horizontal members are sequentially welded by submerged arc or electroslag welding. Even in such a construction method, a control means is required to detect the welding end position of vertical members and move to welding of horizontal members, but conventionally, as mentioned above, it was not possible to directly detect the molten metal position. Since this is difficult, the position has been indirectly detected and controlled using limit switches, etc. Under continuous welding conditions, inconveniences such as excessive or insufficient deposits of fluorophore on the upper part of vertical members may occur. There was a need for a position detection method.

The present invention was made in view of the above-mentioned problems.
The gist is that in the electroslag welding method, a glove is placed in a slag bath above the welding end position, the potential difference between the probe and the base metal is measured, and the potential difference is compared with a preset reference voltage to detect and melt. A method for detecting the position of molten metal in electroslag welding, which is characterized by detecting the position of the metal. The present invention will be explained in detail below with reference to the drawings.

Fig. 1 is a schematic diagram showing the relative positional relationship between the molten metal and the globe according to the welding process in the method of the present invention, and Fig. 2 is a diagram showing the potential difference at each position in Fig. 1. be. FIG. 4 is a sectional view showing an embodiment in which the method of the present invention is applied to electroslag welding of a member having an Lm-shaped cross section.

In Fig. 1, 1 and 2 are the base materials to be welded, and 3
are copper dowels applied to the surfaces of base materials 1 and 2. In electros 2-g welding, backing metals are usually provided on the front and back sides of the base metal, but the backing metals are not shown in the figure. A wire 4 is fed through a tip 5 into a groove surrounded by a copper pad 3 and base materials 1 and 2 and melted. 6 is a weld metal, 7 is an unsolidified molten metal, and 8 is a slag bath. A probe 9 is provided above the base metals 1 and 2 at a distance t from the top of the base metal 1.2, and the probe 9 and the base metal 1 are connected to lead wires 10,
11 is connected to a stain pressure gauge 12. Copper plates 13 and 14 are placed on the upper ends of base materials 1 and 2 to prevent slag from flowing out. With the above-described configuration, welding proceeds in the order of (CB) and (C), and the welding ends when the molten metal reaches the upper end of the base metals 1 and 2 in the state of (C). As welding progresses, the slag bath 8 rises and the globe 9 reaches the position B).
At the position (C), the probe 9 is completely immersed in the slag bath 8, and the potential difference between the sive rope 9 and the base material 1 is measured by the voltmeter 12.

In FIG. 2, the state of change in the potential difference between the globe 9 and the base material 1, which is sub-determined by the voltmeter 12 shown in FIG. 1, will be explained. The horizontal axis shows the elapsed welding time, and the vertical axis shows the magnitude of the potential difference. A and B in the figure.

C corresponds to FIG. 1 (A), (B), and (C), respectively. At point A, the probe 9 and the slag bath 8 are not in contact, so no potential difference appears, but at point B, the probe 9 and the slag bath 8 are in contact and a potential difference VM is detected, and thereafter - as welding progresses. The potential difference tends to decrease9
At 0 point, it becomes Vc. Here, the reference voltage set in advance and the probe 9 as shown in the block diagram in FIG.
If a circuit is provided to compare and output the potential difference between the base material 1 and the base material 1, an output can be obtained at a position between (a) and (b) in FIG. 2 that corresponds to the reference voltage. That is, the reference voltage is the potential difference ve
If set equal to , output will be obtained at 0 point. Therefore, if you experimentally investigate the potential difference between the probe 9 and the base metal 1 that corresponds to the distance between the globe 9 and the molten metal 7 and set it as the reference voltage, it will always be constant regardless of the depth of the slag bath 8. The output is obtained at the distance between the probe 9 and the base material 1,
As good as melting! The position of I@7 can be detected.

In Fig. 1, the probe 9 is positioned at l -5m, the reference voltage is set to 3V, and the workpiece to be welded, which has base materials 1 and 2 with a thickness of 16 fins, is connected to a wire with a diameter of 1.6 tea and a melted wire. As a result of electroslag contact using mold flux at a current of 360 A and a voltage of 38 V, welding could be completed almost on the same plane as the upper end of the base material, confirming the effectiveness of the method of the present invention.

When carrying out the method of the present invention in which a member having an L-shape as shown in FIG. 1′
After detecting that the upper end has been reached, the wire 4 is moved in the direction of the welding line of the horizontal member I' to weld the horizontal member 1''. Platinum, 15, is 7 lux for welding the horizontal member l''. Furthermore, the lead wires 10 and 11 are connected to the electric circuit shown in FIG.

As described above, according to the method of the present invention, the position of molten metal at the upper end of the base metal can be accurately detected in electroslag welding, and electroslag welding can be fully automated, so it has great industrial value. .

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the relative positional relationship between the molten metal and the globe in the method of the present invention, Fig. 2 is a diagram showing the potential difference at each position in Fig. 1, and Fig. 3 is an electrical control diagram of the method of the present invention. FIG. 4 is a cross-sectional view showing an embodiment in which the method of the present invention is applied to welding a member having an L-shaped cross section. 1.2... Base metal, 3.14... Copper dowel, 4... Wire, 5... Chip, 6... Weld metal, 7... Molten metal, 8... Slag Bath, 9...Gloves, 10.
11... Lead wire, 12... Voltage st, ia, t4
... Slag flow prevention copper plate, 15 ... Flux, 1
'...Vertical member, l''...Horizontal member, t...Distance between the probe and the top of the vertical member. Applicant: Yo Nippon Steel Corporation

Claims (1)

[Claims] In the electroslag welding method, a probe is positioned in the slag bath above the welding end point, the potential difference between the probe and the base metal is measured, and the molten metal position is detected by comparing and detecting the potential difference with a preset reference voltage. A method for detecting a molten metal position in electros 2-g welding, characterized in that: