In-situ synthesized metal coating silver brazing rod and preparation method thereof

Abstract

The invention relates to an in-situ synthesized metal coating silver brazing rod and a preparation method thereof. The in-situ synthesized metal coating silver brazing rod is composed of a strip-shaped silver brazing filler metal core and a coating coated on the outer part of the silver brazing filler metal core, wherein the silver brazing filler metal core consists of the following components inpercentage by weight: 10-50% of Ag, 15-45% of Cu, 17-40% of Zn, 1-3% of Sn, 0.1-0.5% of P, 0.5-2% of Ni, 0.1-0.3% of Si and 0.1-0.3% of Li; and the coating consists of the following components in percentage by weight: 5-10% of elemental boron micro powder, 5-10% of sodium borohydride, 15-30% of potassium fluoborate, 25-40% of boric anhydride, 10-30% of sodium fluoride, 2-4% of potassium bifluoride, 1-5% of copper sulfate, 0.1-2% of polystyrene and 0.2-2% of dibutyl phthalate. The brazing filler metal core of the coating sliver brazing rod is good in wettability, is good in liquidity, has self-brazing effect, and enables zinc to be not liable to volatilize; and moreover, the coating has the advantages of being high in activity, weak in moisture absorption, less in carbon residues, good in plasticity and toughness, and the like, and is especially suitable for assemblies such as brazing stainless steel and manganese brass.

Description

technical field [0001] The invention relates to the technical field of welding materials, in particular to an in-situ synthesized metal-coated silver brazing rod and a preparation method thereof. Background technique [0002] The traditional brazing process of the pipeline is the manual flame brazing of wire or strip solder. The flame brazing temperature is high and the heating is fast, but it is prone to problems such as uneven heating and overburning, and the heat conduction of brazing copper is fast. The heating time is longer for metals. When brazing, wire or strip-shaped solder is used to apply the flux to the workpiece before heating or pre-heating. The amount of solder can not be guaranteed, and problems such as solder leakage and solder blockage are prone to occur, followed by Rework, rework or even scrapping will cause waste of solder and raw materials and increase manufacturing costs. In addition, the operation of solder paste or pre-coated flux increases the pre...

AI Technical Summary

Problems solved by technology

[0004] At present, only flux-cored solder rings and self-contained flux-type solder rings are used in pipeline brazing. Since the processing performance of flux-cored solder is restricted by its composition, many component drugs The core solder has the defect of poor deep processing performance, which can only be prepared into strips, and it is difficult to prepare into a ring (the preparation method of the core solder is: the solder is rolled into a strip shape, and then the solder strip is rolled into a U-shaped groove, and the solder is added Finally, through multi-pass rolling joints to form O-shaped tubular structure flux core solder, and then draw and reduce the diameter to prepare flux core solder), the most promising application prospects for pipeline brazing in air conditioners, refrigerators and other industries coated silver brazing rod

However, the self-contained flux-type solder ring disclosed at present has the following disadvantages: during induction heating, in order to ensure brazing efficiency and joint quality, heat must be transferred rapidly between the silver-coated brazing rod and the pipeline to be welded, so the silver-coated brazing rod must The thickness of the coating in the brazing rod should not be too thick, otherwise it will affect the heat transfer efficiency

In order to ensure the ability of the traditional Chinese medicine skin to remove the oxide film, it is necessary to increase the activity of the flux in the coating. Therefore, the coating of the silver brazing rod often contains boric anhydride, potassium fluoride, potassium hydrogen fluoride and other inorganic substances, which are easy to absorb moisture and The pieces fall off, and the flux layer after moisture absorption is corrosive, which seriously corrodes the solder core covered by the coating, especially the copper-phosphorus solder is easy to oxidize, corrode and "rust", and the solder core "rusts". "rust" will seriously affect the storage, transportation, appearance and performance of the coated silver brazing rod. In order to avoid corrosion of the solder core after the coating absorbs moisture, a flux with weak moisture absorption has to be selected, which will lead to the activity of the flux. Very low (the main function of the flux is to remove the oxide film on the surface of the metal to be welded and to protect the metal to be welded from oxidation, and the activity of the flux mainly refers to the ability to remove the oxide film); when brazing stainless steel and manganese brass, Cr on the surface 2 o 3 、TiO 2 and MnO 2 It is relatively stable and difficult to remove; in current projects, a layer of copper or nickel is plated on the surface of difficult-to-braze metals to improve its brazeability, but whether electroplating or electroless plating is used to add a process, the operation is complicated, the cost is also increased, and it is harmful to the environment. serious pollution

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