JPS6122510A - Long lead-sheathed submarine power cable and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a long lead-sheathed submarine power cable whose lead sheaths are welded together in a factory, and a method for manufacturing the same.

(Background of the invention) Figure 2 is a cross-sectional view showing an outline of a lead-sheathed submarine OF cable, where 0shi is a cable conductor with a hollow oil passage GD inside, 0J is an oil-impregnated paper insulation layer, and 0Φ is a lead-sheathed cable conductor. , 051 is the floor layer,
OD is a steel wire armor made by winding a large number of iron wires, 0
71 is a protective layer.

Such lead-sheathed submarine power cables are usually jointed in advance in a factory and then shipped by ship as a series of cables of the required length. The most problematic part of this factory joint is the lead-sheathed welded connection. Conventionally, as shown in Figure 3, the bevel of the lead-sheathed 041 to be welded is removed to form a trough 0 seconds. Welding by hand with a gas torch (
) The base material, lead sheathing 041, and lead welding rod 0! l
The connection was made by filling the valley OD while melting the il, but there were problems as listed below, and sometimes breakage occurred at the welded connection, and improvements were desired. For this reason, extremely large equipment may be required to manufacture cables in a continuous length without connecting parts, which poses the problem of requiring a huge investment in equipment.

■Due to gas welding, atmospheric air and combustion gases are drawn in during welding, resulting in subtle pinholes in the welded area.

For this reason, the mechanical properties of the welded part are poor, and it is weak against tension and bending, leading to breakage.

■Welding lead sheathing itself is technically difficult, so it requires a high level of skill, and it is necessary to train experienced people.

■Quality varies due to manual work. In other words, the difficulty of workability varies depending on the skill of each worker and the welding position (upper, lower, lateral, etc.), so the amount of lead welding rod supplied, the amount of lead covering and lead welding rod melted, the flame the size and strength of
This is due to the inability to quantify and stabilize welding positions, etc., and large variations in welding conditions.

(Disclosure of the Invention) The present invention solves the above-mentioned problems and provides a long lead-sheathed submarine power cable with stable quality and a welded joint that is difficult to crack, and a method for manufacturing the same.

The inventors realized the necessity of mechanizing and automating welding in order to stabilize the quality of lead-covered welded joints and ensure that the welded joints never cracked. In addition to gas welding, which was used in the As a result, it was found that gas welding is difficult to manage, such as the amount of gas, the strength of the flame, and the need to ignite each time, making it unsuitable for mechanization and automation. It was found that it was necessary to employ electric welding such as welding or TIG welding.

However, due to the high current of MIG78 welding, it was impossible to weld lead sheathing with a low melting point, so we ended up conducting more in-depth research on relatively low-current TIG welding.

However, conventionally, when welding lead sheathing with a low melting point, the lead welding rod is melted little by little at a low temperature using a weak flame of propane gas, hydrogen gas, etc., and the welding is done by gradually melting the lead welding rod. Gas welding has been common because it allows for visual inspection and is easy to work with. Generally, TIG tB welding is used to weld steel materials in a short period of time at a high temperature (usually at a high current of 50 amperes or more), and the idea of welding lead sheathing by TIG welding has never occurred. In this way, we found a problem in welding lead coatings, which we had no experience with. One of the most important conditions is that the welding current be in the range of 10-30 Ambea, with the optimum current being +8A. As mentioned above, the welding current for ordinary steel materials is as high as 50 amperes or more, but the key point of the present invention is to use a low current. It is extremely important to keep the welding current between 10 and 30 amperes because dripping occurs and welding becomes difficult, and on the other hand, if the current is lower than 10 amperes, it is difficult to melt both the lead coating and the welding rod.

Next, the welding direction is to proceed from the bottom to the top on the circumference of the lead sheath 041, as shown by the arrow in Figure 4, where the lead penetrates well and a good weld is obtained. . Note that FIG. 4(a) shows the case of two divisions, and the same figure (→ shows the case of four divisions; the larger the number of divisions, the less the change in shape of the parts to be continuously welded becomes easier, and the welding becomes easier.

Furthermore, welding conditions other than those mentioned above are listed below.

■The size of the tungsten electrode is 1.0 to 3.0 mmφ, and the optimal value is 1.0 mmφ. Bmmφ. This is because if the electrode length is smaller than 0 maφ, the electrode will quickly melt and must be replaced frequently, whereas if it exceeds 3.0 maφ, the arc will disperse and will not be concentrated at the required location.

■The positional relationship between the welding rod and the welding torch on the lead sheath is such that the welding rod is in the front and the welding torch is in the back in the welding direction. If this positional relationship is reversed, the welding rod will follow the molten pool created by the welding torch, which will narrow the allowable range of the welding rod feed speed and welding speed, making management difficult and welding difficult.

■The distance between the base metal, that is, the lead coating, and the welding torch is 1 to 4 degrees, and the optimum value is 2 degrees. If the distance exceeds 4 fins, the lead covering will not melt and only the welding rod will melt, making it impossible to weld, and the
If the welding rod is smaller than 1Jl, the welding rod and welding electrode will come into contact and arc breakage will occur, making welding difficult.

■The welding speed, that is, the feed speed of the welding torch is 5 to 20 mm/
sec, the optimal value is I Ow /see. If the velocity is less than 5 discharge/see, the volume of the molten pool in the lead coating increases and the melt falls, and the
If it exceeds e, the lead coating will not fully melt and welding will be difficult.

■The wire speed of the welding rod is 2~8mm/sec, and the optimum value is 4,5 w/see. speed is 2 rh
If it is smaller than 8 mm/sec, the amount of welding rod supplied is small compared to the size of the molten pool of the lead coating, so the surface will be uneven, and if it exceeds 8 mm/sec, the amount of welding rod supplied is large and it is sufficient. It is not completely melted and does not adhere properly to the lead coating, resulting in a convex surface and voids in the built-up area.

■The size of the welding rod is 1 to 4 mmφ, and the optimal value is 2■φ
It is. If it is smaller than 1 φ, the welding rod is too soft and a stable feed line speed cannot be obtained, and if it exceeds 4IIIlφ, the feed line speed becomes small and control becomes difficult.

■The angle (θ) between this tangent line and the welding torch (fifth
(see figure) is 65-80', and the optimum value is 72°.

Hereinafter, we have explained various conditions for welding lead sheaths using the TIG welding method.
We have confirmed that welding is more stable in quality and produces better quality welds than conventional gas welding.

However, skill training is difficult, and even for those who have some skill, the welding position becomes poor depending on the welding position (second, downward, lateral, etc.), resulting in variations in quality. Also, in the case of TIG welding, the arc cannot be seen directly, so
It is necessary to work with the welding surface attached, but it is difficult to move the welding torch to the designated welding start position because it is dark until the arc flies, and it is also difficult to check the melting of the lead coating and welding rod during welding. Therefore, the quality varies depending on the person.

If we use robots to eliminate such variations and carefully manage each control point, the quality will be even more stable and welded joints of high quality can be obtained. The combination of conventional gas welding and robots controls the gas scene, the size, intensity, color, etc. of the gas flame, extinguishes the flame each time the welding torch leaves the lead coating, and extinguishes the flame each time the welding torch approaches the lead coating. It is difficult to control such things as attaching them, and it is difficult to combine them. In contrast, in the combination of TIG welding and robots, for example, the strength of the flame can be determined by setting the current value, and the flame can be automatically ignited or extinguished depending on the distance between the lead coating and the welding torch. Moreover, when the flame goes out, various controls such as automatically stopping the welding rod feed line and other in-lock functions can be easily performed, and the effects of the combination can be fully demonstrated.

FIG. 1 is a schematic explanatory diagram of a device that combines a TIGf&connection device and a robot to achieve the manufacturing method of the present invention. (1) is a welding robot with an articulated robot equipped with motion functions of 5 or more axes, preferably Air set 1 for normal S-axis functional robot
A robot with a 6-axis movement function and an 80° rotation axis is used. (2) is the robot control panel, (3) is the welding condition command panel, (4) is the TIG welder, 0 is the TIG welder control panel, (6) is the welding rod automatic feeder, and (6^) is its Control panel, (force is the welding torch, (8) is the welded part of the cable lead sheath (9), 0■ is the cable holder is the roller, GD is the reel (1)
The lead welding rod supplied from 1^) and 02+ are the grounding lead wires.

The following is an outline of the working method for welding cable lead sheaths in a factory using such a device.

■As usual, use jigs and tools to prepare the grooves for the lead sheathing that will be welded and connected.

■Move the robot using the teaching box inside the robot control panel■, and have the robot memorize the image of the part to be welded all around.

■TIG welder Welding machine control panel Type Welding conditions are set.

■Set the welding rod feed speed to the specified conditions on the welding rod automatic feeder control panel (G6L).

■Instruct the position to be welded, welding contents, etc. on the welding condition command panel (3).

When the settings above 0 are completed and the robot start switch is turned on, the robot automatically determines the position to be welded according to the set conditions and generates the lead welding rod that is the base material and the lead coating from the welding torch tip. The metal is melted in an inert gas atmosphere using an electric arc, and welded overlay.

(2) From then on, the welding operation is automatically repeated until the predetermined build-up thickness is reached, making it possible to form a high-quality lead-covered welded joint.

Regarding the lead plate, T was tested using a robot in an inert gas.
The table below shows the characteristics when comparing IG welding and conventional gas welding.

In the case of conventional gas welding methods, workability is affected by the occurrence of pinholes within the weld, variations in skill among workers, and differences in welding positions in the circumferential direction (upper, lower, side, etc.) even for the same worker. There are variations depending on the difficulty level, and the characteristic values themselves are low and have large variations. Also, most of the fracture points were in the center of the weld. On the other hand, in the case of TIG welding according to the present invention, it was confirmed that the quality is stable and that characteristics close to the original can be expected.

(Effects of the Invention) In the welding of lead sheathing by TIG welding in the present invention, electric welding is performed in an inert gas, so that a stable and high-quality welded part without pinholes can be obtained even by hand. Furthermore, by combining automatic welding with a robot, the distance between the welding torch and the base material, the distance between the welding torch and the welding rod, the welding speed,
Since the welding temperature and other welding conditions can be controlled and managed quantitatively, welded parts with more stable quality can be obtained, and there are advantages such as no need for training by experts.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of a device combining TIG welding and a robot according to the present invention, Fig. 2 is a cross-sectional diagram schematically showing a lead-sheathed submarine OF cable, and Fig. 3 is an explanatory diagram showing a conventional welding method. FIG. 4 is an explanatory diagram showing the welding direction in the present invention, and FIG. 5 is an explanatory diagram of the angle of the welding torch. 1... Welding robot body, 2... Robot control panel,
3... Welding condition command board, 4... TIG welding machine, 5...
... TIG welding machine control panel, 6... Welding rod automatic feeder, 7... Welding torch, 8... Welding section.

Claims (3)

[Claims] (1) A long lead-sheathed submarine power cable characterized by having a lead-sheathed connection part welded and connected by TIG welding. (2) In a manufacturing method for obtaining a long lead-sheathed submarine power cable by welding and connecting lead sheaths in a factory, the welding tangents of the lead sheaths are welded using TIG welding in an inert gas atmosphere at a welding current of 1
A method for manufacturing a long lead-sheathed submarine power cable, characterized in that welding is performed from the bottom to the top on the circumference of the lead-sheath at 0 to 30 amperes. (3) A method for manufacturing a long lead-sheathed submarine power cable according to claim 2, characterized in that automatic welding is performed using an articulated robot equipped with motion functions of five or more axes.