The world's first pump casing with TIGer how wire cladding technology--The innovative application of Nuclear power petrochemical company
TIGer: tungsten inert gas electrically reinforced technology, a torch equipped with two electrodes.
The main pump is the heart of the nuclear power plant, while the pump casing is one of the key equipments for the main pump. The safety and durability of Hualong No. 1 proposes higher requirements on the design and manufacture of the main pump casing.
The traditional process for the inner wall cladding of the pump casing is with the help of the peripheral equipment: overturn the positioner to realize the rotation of the workpiece; then install the welding head on the column boom and finish the overlaying process by fixing the welding head while rotating the workpiece. However, the shape of the inner wall of the pump casing is irregular and curved, and the welding space is very limited. At this point, manual welding is required. Especially when carrying out the transition layer 309L overlay in the inner layer, it is hot cladding and takes long time. It’s a necessity that the temperature of the base metal is not lower than the certain preheating temperature. The working environment and process conditions are very harsh. All these make it very difficult to weld with traditional welding technology.
To this end, in order to improve the working environment and labor intensity of workers, and to ensure the quality of corrosion-resistant layer surfacing of the products, the technical department of CNEG brings in the POLYSOUDE SPX endless rotating TIGer how wire cladding machine. Without considering the cable winding, the SPX endless rotating welding head keeps rotating which drives the torch to perform circumferential welding on the inner wall of the pump casing. At the beginning of welding, with the automatic centering function of the column boom, we can keep the rotation center of the welding head and the entrance and exit hole center of the workpiece at the same concentricity (the concentric accuracy is controlled within 0.1 mm). The welding head reaches deep into the inner wall of the pump casing, and the torch has an angle adjusting mechanism which allows the torch to be adjusted from 0-360° so as to realize 1G, 2G and 4G welding functions. The whole welding process is programmed and the arc length is automatically controlled, which effectively avoid welding failure caused by tungsten electrode or wire sticking to workpiece due to the irregularities of the workpiece and the inaccurate position of the contoured intersection. That’s why it can satisfy various overlaying requirements i.e. all kinds of space interferences, different cladding thickness and width, and the variable diameter positions.
By TIG hot wire overlay technology, the welding heat affected area is protected by high purity argon gas during the whole welding process. The dilution ratio between the base metal and the deposited metal after cladding is very low, about 3%-10%. The deposition rate is about 2 to 3 times compared with the traditional welding. After cladding, the precise geometry can be obtained according to the process requirements and the rework rate is low which can save a lot of time and cost.
CNEG works closely with Polysoude this time and jointly develops TIG tungsten hot wire overlay machine which marks a new leap in the localized manufacturing capability, new breakthroughs in manufacturing technology and new improvements in the manufacturing of nuclear power equipment in China.
"Hualong No. 1" is an important measure for China's nuclear power "going out" development strategy and promoting the "Belt and Road" construction. It is also an important step in the national energy development plan. In the past, for China’s nuclear power products “going out”, we used to buy directly from other countries or collaborate with them. But now "Hualong No. 1" nuclear power products promote the transforming from traditional ways to making our own products. Through the output of advanced nuclear power technology with independent intellectual property rights, it will drive all aspects “going out” from engineering, equipment, materials, technical services to technical standards.