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Poor anti-corrosion function of stainless steel air duct mac

1. Phenomena
 
There are scratches, scratches and other defects on the surface of the air duct machine, as well as welding slag spatters. Black, macular and speckles appear on the surface of the welding seam.
 
2. Cause analysis
 
(1) The method of cutting and processing the sheet of air duct machine is inappropriate.
 
(2) During operation, carbon steel contacts stainless steel.
 
(3) The selected welding technology is unreasonable.
 
(4) The method of preventing the dropping of welding slag spatter was not adopted in the welding process.
 
(5) Surface is not cleaned up after welding.
 
(6) Open holes in the weld seam and its surroundings.
 
3. Prevention and control measures
 
(1) When cutting or processing the sheet, the worktable should be laid with rubber sheet, and the scratch needle should not be used for scratching, so as to prevent scratches and abrasions on the surface of stainless steel, thereby damaging the oxide film on the surface and reducing the corrosion resistance of the stainless steel sheet. When biting, use wooden square ruler and wooden hammer; roll round, pre-bend and fold edge, use copper hammer or stainless steel hammer to prevent the formation of scars and depressions on the surface of the board; the surface of the air duct that does not need processing should be as flat as possible, without hammer marks.
 
(2) In the process of processing or storage and stacking of stainless steel sheets, it is necessary to prevent contact with carbon steel and to prevent corrosion centers on the surface of stainless steel due to long-term contact between iron chips of carbon steel and stainless steel, and to damage the passive film of oxide layer on the surface.
 
(3) For stainless steel air ducts with thickness greater than 1 mm, the welding method should be chosen. Argon arc welding and direct current arc welding are optional, but gas welding is not allowed. Oxygen and acetylene have corrosive effects on nickel and chromium in stainless steel. Together, under the action of oxygen, nickel and chromium will be burned down at high temperature, which will damage the corrosion resistance of stainless steel. There should be no cracks or over-burning on the surface of weld and heat-affected layer, no pore and slag inclusion on the surface of weld, and no blackening, yellowing and spots on the surface of argon arc welding.
 
(4) When making stainless steel air duct by arc welding, chalk powder should be coated on the surface of both ends of the weld during the welding process to prevent welding slag spatters from adhering to the surface of stainless steel plate.
 
(5) After the air duct is welded, the welding seam and the surface of the air duct should be cleaned up. That is to say, oil stain and welding slag and spatter are removed first, then pickled, then washed clean with hot water, passivated and then washed.
 
(6) The air duct made of stainless steel plate will be deformed by opening holes in the weld seam and its edge, and the mechanical strength and corrosion resistance will be reduced due to the change of metallographic structure in secondary welding. Therefore, it should be considered comprehensively when making air ducts.
Jiangsu Sanzheng Machinery Technology Co., Ltd.

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