20Mn23Al non-magnetic steel is a kind of electrical special steel produced by domestic steel mills to meet the special requirements of large transformer manufacturers, which is less used in the general machinery industry production, and has no mature welding process and special welding materials. Most domestic transformer manufacturers generally use A202, A302, A132 and other electrode arc welding 20Mn23Al. However, for the thickness of 30mm transformer cover plate, not only the production efficiency is low, but also there are many problems that are difficult to solve. Therefore, as long as we can solve the welding of 20Mn23Al non-magnetic steel and the welding problem of 20Mn23Al non-magnetic steel and Q235 low carbon steel, we can save a lot of raw materials, reduce the cost of transformers, and improve the competitiveness of products.
Domestic manufacturers basically use welding rod arc welding transformer box cover, but the production efficiency is low, and the appearance quality of the weld is greatly affected by human factors. In order to improve productivity and product quality, the use of automation equipment is inevitable. Therefore, we used submerged arc welding (MZ-1000 submerged arc welding machine) on the basis of analyzing the weldability of 20Mn23Al non-magnetic steel and Q235 low carbon steel. As long as the fusion ratio of welding is reasonable, the required structure can be obtained.
The welding material is ER308 welding wire. Submerged arc welding: wire ER308+HJ260; MAG welding: welding wire ER308+ gas mixture (Ar+2% ~ 5%CO2).
Two pieces of 20Mn23Al and Q345(2000mm×200mm) with a thickness of 30mm. The groove is machined, and the groove is asymmetric X-shaped, which is 12mm×45° and 18mm×30° respectively. Clean the rust, oil and oxide within 20mm of the groove and both sides. If there is oil on the surface of the purchased wire, clean it as much as possible.
When selecting and formulating welding parameters, small diameter welding wire, small current and high voltage should be selected. During the welding operation, pay attention to the welding arc do not swing, do linear movement, if necessary, can be properly burned back. Hammer the weld after welding each layer to improve its resistance to thermal cracking.
Note: Adjust the welding sequence according to the deformation of the transformer box cover. The weld must be cleaned before welding, and there must be no oil, water and rust dirt on the welding wire and welding joints. The welding current shall not exceed 480A, and the weld surface shall be golden.
MAG welding is used as the base, submerged arc welding is used to fill the cover, and the production efficiency is four times that of the original manual welding. The weld has high quality and little pollution, which can greatly reduce the labor intensity of welders. However, due to the limitation of equipment conditions, this welding method is only suitable for long and straight welding. MAG welding is used as the base, submerged arc welding is used to fill the cover, and the permeability of the weld can meet the technical requirements of the product. According to the preliminary test, the qualified rate of weld is above 60%.
