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  • The use of continuous furnace aluminum brazing process
  • 2018/7/5¡¡Number of reading£º[4572]
  • 1. The surface of the workpiece is prepared
    In order to ensure the formation of uniform high-quality brazed joints, welding must be removed before the surface of the oil, oxide; in order to improve the brazing of certain materials or increase the wetting capacity of the base metal and other materials often used in the base metal plating metal.
    (1) to clear the oil
    Common organic solvents to remove oil, such as alcohol, gasoline, trichlorethylene, carbon tetrachloride and so on. Mass production is often degreased in organic solvent vapors. In the bath cleaning can be used when the mechanical stirring or ultrasonic vibration to improve the cleaning effect. After degreasing, wash with water and dry.
    (2) remove the oxide
    Parts of the surface oxide removal of materials, production conditions and bulk, in the mechanical, chemical etching and electrochemical etching method and other methods to choose. After chemical etching or electrochemical etching, it is necessary to perform a bright treatment or neutralization treatment, followed by washing with water and drying.
    A. Suitable for mass production of mechanical removal methods are grinding wheel, metal brush, sandblasting and other methods.
    B. Chemical etching to remove surface oxide begins in mass production with high productivity. The choice of the etchant depends on the state of the parent metal and its surface oxide. Aluminum and aluminum alloys can be used (10% NaOH, the remaining water or 10% H2SO4, the remaining water) of the etching solution.
    C. Electrochemical etching is also suitable for mass production and the need to quickly remove oxides of the situation, mostly for stainless steel and carbon steel oxide removal process.
    (3) metal coating on the base metal surface
    The metal plating on the surface of the base metal is mainly to improve the brazing property of the brazing filler metal; to increase the wetting ability of the brazing filler metal to the base material; to improve the productivity as a pre-brazing filler layer to simplify the assembly.
    Table 1-1 aluminum base metal plating metal plating and plating methods
    Base metal plating material method function
    Aluminum nickel, copper, zinc plating, chemical plating to improve the solder wetting, improve the corrosion resistance of aluminum
    Al-Si alloy
    Covered
    Used as solder

    2. Preset flux and blocking agent
    Some welding methods require pre-placing flux and blocking agent. Preserved flux is mostly ointment type liquid to ensure uniform coating on both surfaces of the workpiece. Viscosity of small flux can be used dip, hand spray or automatic spraying. Viscosity of the flux will be heated to 50 ~ 600C, without dilution can reduce its viscosity, hot flux its surface tension is reduced, easy to stick to the metal.
    Solder brazing and flame brazing for gas fluxing, and brazing with solder brazing filler, without prefabricated brazing filler metal. Vacuum brazing does not require flux.
    The retarder is an auxiliary material used to prevent solder flow during brazing. Brazing and true in a gas protection furnace
    The most widely used braze in an empty furnace. The retarder is mainly composed of a stable oxide (such as alumina, titanium oxide, magnesium oxide, etc.) and a suitable binder. The paste-like blocking agent is applied to the surface of the base material which does not need to be brazed before welding. Since the flux does not wet these substances, it can prevent its flow. Braze and then remove the blocking agent. 3. Assemble the positioning and placement of solder
    The best assembly method is the part can be self-positioning and self-support, in addition to the fixture can be positioned in the clamping. For the surface of the base metal coated metal flat tube and fins at this time the joints do not consider the gap size, but the joint brazing must be pre-imposed by the fixture pressure, so that the brazing process joints to reduce the gap. The head cover and the main tube installed in accordance with the corresponding position and with a wooden hammer knock tight, and then in the spot welding machine with the inlet and header together with the spot welding method to make it together, For brazing.
    If there is a need for pre-placement of the brazing material, the brazing filler metal is placed at a predetermined position while assembling. 4. Brazing
    For the nitrogen furnace in the aluminum brazing: a flux spray device to spray the flux onto the workpiece, through the drying furnace to the workpiece heated to 150 ¡æ ~ 250 ¡æ for drying, in the protective atmosphere into the brazing furnace When the temperature reaches 610 ¡æ, the workpiece is brazed and then cooled by water cooling and air cooling. The workpiece is unloaded by the unloading station. The process is as follows:
    Welded workpiece ¡ú Spraying agent ¡ú Transfer device ¡ú Drying furnace ¡ú Transfer device ¡ú Heating furnace ¡ú Brazing furnace ¡ú Water cooling room ¡ú Air cooling room ¡ú Transfer device.
    (1) flux spray
    A conveyor chain carrying the workpiece through a closed flux chamber in which the water flux is sprayed onto the workpiece. After the spraying is completed, the excess flux on the workpiece is removed by an air blower, and then the workpiece is conveyed to the drying furnace The
    (2) drying process
    After spraying the flux, the parts need to enter the drying oven to dry, the temperature is usually around 200 ¡æ, should be careful to prevent heat exchanger overheating, due to overheating (ie 250 ¡æ) may lead to the formation of high temperature oxide aluminum oxide.
    (3) continuous brazing furnace
    Brazing furnace must ensure that the temperature of the workpiece per minute to increase above 20 ¡æ, so that the workpiece surface coating solder to the melting point (591 ¡æ). Workpiece temperature balance of ¡À 3 ¡æ, while the furnace to maintain the atmosphere of nitrogen protection. The control of the workpiece temperature and the consistency of the temperature requirements of each workpiece is very high, so the heating chamber is divided into several control areas. The more the area, the better the temperature control of the workpiece. Any large fluctuations will cause the workpiece brazing to be insufficient or excessive.
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