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Microbeam Plasma Arc Welding of Bellows Components
skills requirement
The assembly of bellows and pipe joints is shown in Figure Bellows and pipe joint assembly. It is required that the welded joints have reliable tightness and vacuum tightness, and the working flexibility and corrosion resistance of the bellows must be maintained. Therefore, the heating temperature of the working part during the welding process shall not exceed 200 °C.
Weldment material and specification
The material is 1Cr18Ni140Ti stainless steel, the diameter of the bellows is 18 mm, the plate thickness is 0.12 mm, and the wall thickness of the pipe wall head is 2 ~ 4 mm.
Joint form
Due to the great difference in the thickness of the parts to be welded and the different heat dissipation conditions, it is difficult to weld. In order to prevent the edge of the corrugated pipe from burning through, the joint form shown in Figure Bellows and pipe joint assembly is adopted, and the “baffle” structure is used to eliminate the burning through of the edge of the bellows.
Craft equipment
Clamp the corrugated pipe assembly in the special mould, so that the entire working section of the bellows is also in the mould, and the seam is about 2 mm exposed from the mould.
welding process
When welding, the weldment is rotated around the horizontal axis or inclined at an angle of 45° to the horizontal axis, and the welding torch is perpendicular to the weld. Welding parameters: I=14~16A; U=18~20 V; ion gas: argon, the flow rate is 0.4 Lmin; shielding gas: argon or argon-hydrogen mixed gas, the flow rate is 3~4 L/min; nozzle to The weldment distance is 2 ~ 4 mm; the welding speed is 3 m/h.
Microbeam plasma arc welding with this parameter can completely melt the baffle and fuse with the edge of the bellows to form a good weld.
welding quality
The actual measurement shows that the heating temperature of the working part of the bellows is not higher than 80°C during the welding process, which ensures the elasticity of the bellows. After the air tightness test, there is no leakage of the welded joints, which meets the requirements of vacuum tightness. Tensile tests showed that the failure of the samples all occurred on the base metal, and the welded joints had good mechanical properties.
Water recompression type air plasma arc online cutting of spiral welded pipe
The size of the spiral steel pipe manufactured by high-frequency welding is 4219-377 m, and the wall thickness is 7mm. The production process of the spiral welded pipe is shown in Figure Spiral welded pipe production and online cutting. The welding speed is 5 m/min, and its peripheral speed is approximately equal to 3.5 m/min. In order to ensure the continuous production of spiral welded steel pipes, it is required to use air plasma arc fast cutting, and the cutting speed should not be less than 3.5 m/min.
cutting method
It adopts water recompression air plasma arc cutting, and adopts cutter wheel clamping type pipe cutting machine and related auxiliary devices.
Cutting Process Parameters
Through experiments, the optimal process parameters were found to be 1=260 A, U=230V, nozzle aperture d=3.5 mm; gas flow rate Q=1.5 L/min, pressure P=0.5 MPa.
Cutting result
The cutting speed can reach 3.9 m/min, the cutting angle of the pipe end is less than 1.5mm/2π, and the bevel is equal to 30°