A plate rolling machine used by a factory has a long-term operation and the turbine of the transmission system is worn and broken. This plate rolling machine has an older model and cannot be replaced by parts, making the equipment inoperable.
The turbine material is phosphor bronze, which has high thermal conductivity and poor welding performance. It is very difficult to repair by welding. Because the turbine is the transmission system of the main machine, after welding, not only must there be no defects such as pores and slag inclusions in the weld, but also to ensure that it can be machined to achieve a certain accuracy before assembly. According to this requirement, the following repair welding process was adopted.
1: Preparation before welding
1) Grind the broken teeth of the turbine with an angle grinder to remove cracks, surface scratches, etc., so that the surface to be welded is clean and smooth, exposing metallic luster.
2) The oxide layer at the surfacing area should be removed by pickling. The formula of the pickling solution is as follows: 75em3/L HNO3 + 100cm/LH2SO4 +1em3/L HCI. After the turbine is pickled, it is washed with alkali water to neutralize Finally rinse with clean water and blow dry.
3) Welding materials are selected according to phosphor bronze base metal, and Hunan WISE New Material Technology Co., Ltd. special high-entropy alloy hardfacing powder and wear-resistant spray powder are used. Before welding, put the spray powder into the drying box, bake it at 250C for 2h, and then put it in the insulation box for use.
2. Welding process
The welding ambient temperature should not be lower than 5C. Plasma powder spraying equipment is used for automatic spray welding, high current and slow powder feeding, and artificial intelligence program controls the formation of the weld seam to meet the requirements of post-weld mechanical processing.
After each layer of weld bead is welded, the weld bead and closely related surfaces should be hammered immediately to eliminate the welding residual stress.
3. Heat treatment after welding
After the surfacing, the turbine should be sent to the heating furnace in a hot state (about 200C), heated to 500 and kept for 2h, and then taken out of the shield and quickly cooled to room temperature to eliminate welding residual stress, improve the grain structure, and Ensure the machining performance of surfacing metal.
After the wreck wheel is mechanically processed, the dimensional accuracy meets the technical requirements. After more than three years of use, there is no abnormal phenomenon in the surfacing part, and the effect is good.
