Preparation method of alkali-cleaned flux-free or vacuum brazing sheet

Abstract

The invention discloses an alkali cleaning fluxless or vacuum brazing sheet preparing method. The method comprises following steps that an alloy casting device is adopted, a casting ingot is casted, acore layer and a brazing layer are each subject to annealing, and then are hot rolled into thin sheets, all layers are welded together, hot rolling and cold rolling are carried out, finally, annealing is carried out, before welding, and a surface treatment method is executed. The surface treatment method comprises following steps that firstly, an organic solvent is used for cleaning the surface of an alkali cleaning fluxless or vacuum brazing sheet; secondly, alkali liquor is used for cleaning a product in the first step, and the product comprises one or multiple of 0 to 5wt% of sodium gluconate, 0 to 5wt% of sodium pyrophosphate, 0 to 10wt% of sodium carbonate, 0 to 3% of sodium phosphate and 1 to 10wt% of sodium bicarbonate, 0 to 1wt% of NaOH and 0 to 5wt% of sodium silicate; thirdly, asaturated EDTA solution or saturated isopropanol solution is used for cleaning the product in the second step; fourthly, a salpeter solution is adopted to carry out acid pickling on the product obtained in the third step; fifthly, washing is carried out. The corrosion to silicon particles is small, the pollution is small, good brazing gaps are ensured, and the good effect is obtained.

Description

technical field [0001] The invention relates to a method for preparing an alkali-washed flux-free or vacuum brazing plate. Background technique [0002] Flux The heat transfer industry has grown to require the manufacture of high quality materials and components at the lowest possible final cost. Heat exchanger brazing is most commonly produced in an atmosphere of nitrogen with as few oxygen impurities as possible. This process, known as Controlled Atmosphere Brazing (“CAB”), also includes Al-K-F based fluxes, such as the Nocolok flux applied, which is achieved by adding brazing flux to decompose, dissolve and remove the oxide film to form wetting and melting. Purpose. [0003] However, post-brazing flux residues are generally considered detrimental to heat exchangers, as they may spread on the brazed aluminum surfaces or clog internal channels, preventing efficient heat transfer with the heat exchanger. The residue after fluoride flux brazing adheres tightly to the surfac...

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Problems solved by technology

US2015053751A1 discloses a method of alkali cleaning, but the material alloy does not contain magnesium, and the volatilization of magnesium does not react with several ppm oxygen or water vapor in the outer space of brazing. It is difficult to remove the influence of oxygen in the outer space on the oxide film, resulting in brazing Welding is still not full

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