Transformer Corrugated oil Tank structure and its welding method by MAG-Gas shielded Arc Welding.
Abstract: This article deacribled the structure and welding method of transformer ripple oil tank (Transformer Corrugated Oil Tank). The experiment, which welding by using CO2 and mixed gas, shows that the mixed gas arc welding (MAG) is available for welding transformer ripple oil tank.
Keywords:Gas arc welding; Transformer tank; Corrugated fins radiator;
This article is translated from YUGaobo which is the engineer from Department of Technics,Zhe Jiang 3rd Transforemr Group. Stated the Argon Arc Welding method by Gremany TKWZ1600 transformer corrugated tank manufacturing line.
The corrugated oil tank transformer has many advantages, such as small size, beautiful appearance, few solder joints and not easy to leak. It has been more and more popular with users. However, if we can’t master all kinds of welding methods skillfully in the manufacturing process, the corrugated tank produced can not meet the quality requirements. This paper introduces the application of CO2 gas shielded welding in the welding manufacturing of transformer corrugated tank as follows.
1.Transformer corrugated oil tank structure
The Transformer corrugated tank is rectangular in shape. Its structure consists of corrugated wall, bottom and edge of tank. The corrugated wall is made of 08AL SPCC cold-rolled plate 1-2 mm thick, use Hydraulic Decoiler to hold and feed steel roll,folded by hydraulic corrugated forming machine,weld by Auto Corrugated radiator seams welding machine.
The bottom of the transformer corrugated oil tank box is made of 4mm thick common carbon structural steel, while the edge of the box is made of 75mm/ 50mm/ 6mm hot-rolled unequal angle steel. The seams between the bottom, the edge and the corrugated wall of the tank are lapped. The total number of seams for each tank is 8. All seams are completed by fully automatic CO2 arc welding machine on the operation table.
2.Welding Method of Transformer Corrugated Oil Tank
2.1 Pure CO2 Gas Shielded Welding
In the adjusting stage of transformer corrugated tank production line, the welding method is conservative. It operates according to the technical requirements of imported equipment and adopts pure CO2 gas shielded welding. As a result, there are some defects, such as large spatter, poor weld surface formation and many gas holes in the welding process.
In order to improve the welding quality of transformer oil tank, we used the advanced experience of some manufacturers as reference.Which improved the original welding method, and used Ar-rich plus CO2 gas shielded filament to weld corrugated oil tank, and achieved satisfactory results.
2.2 Rich Argon Mixed Gas Shielded Welding
2.2.1 Basic Principles
Short-circuit transfer of Ar-CO2 welding is the basic way of droplet transfer in welding with mixed gas under small specification. This process requires that the proportion of Ar gas in protective gas should be a certain proportion, that is, the mixing ratio of Ar-CO2 gas should be determined first.
What is the difference between pure CO2 welding and Ar gas welding?
We find that if a certain amount of Ar gas is added to CO2 gas, the welding penetration becomes shallow and the spatter is very small, and even if the arc is welded at low current, the arc is quite stable. If used in sheet metal welding, it is found that the bead is beautiful in shape and rarely burns through, and the arc is stable, which is exactly what we expect.
The next question is how much the mixing ratio of Ar and CO2 should be?
After many tests, it is found that the best welding effect is that the volume fraction of CO2 is between 18% and 22%, and the spatter rate is reduced to less than 15%.
2.2.2 Welding Process
In order to realize the welding process, a push wire welding machine was used. The proportioner made the volume fraction of Ar gas reach 78%~82%, and the volume fraction of CO2 reach 22%~18%. It constituted Ar-CO2 mixture gas. Copper-plated wire is 10mm and its brand is H08Mn2SiA. The joint is lapped, and the angle between the torch and the vertical line is shown in Fig. 1a and Fig. 1b
Diagram of angle between welding torch and vertical line
Before welding, two plates should be positioned by spot welding. Generally, the distance between two points is 350-450 mm. A set of welding parameters is recommended for reference, as shown follows:
Welding process parameters:
3 conclusion of Transformer Corrugated Tank welding
In the welding transformer corrugated tank processes,Compared with manual arc welding and pure CO2 welding, the welding quality has the following advantages:
A. High current density, heat concentration, high deposition coefficient, fast welding speed and small deformation;
B. Beautiful bead shape, less pore, stable quality, greatly reduced repair rate;
C. Because the molten pool is small and the penetration becomes shallow, the welding speed is easy to control.
D. Insensitive to grid voltage fluctuation, stable arc and little welding spatter;
E. The process is simple and practical for thin plate welding and can be popularized.