Vacuum Repair Welding Process

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1. Cleaning the workpiece to be repaired. For casting cracks, welding cracks or quenching cracks of new parts, the surface is usually polished with a fine emery cloth and then cleaned with alcohol or acetone. For iron and cobalt-based superalloy cracks, generally, only surface degreasing, sandblasting, cleaning and vacuum purification are sufficient. For nickel-based superalloys, ultrasonic or other special cleaning methods should be added. For surface aluminized parts, the aluminized layer must be removed first (pickling or sand blowing, etc.).

2. Injecting the solder. For penetrating cracks, only one side is allowed to be injected with solder; for non-penetrating cracks, the exhaust part should be reserved when filling with solder. In this way, it can be ensured that the gas inside the crack is completely evacuated by the pump before the solder is melted, so as to facilitate the capillary function. If it is a non-penetrating crack in a larger courtyard, the alloy powder can be directly loaded into the crack, solidified with a fine needle or stainless steel wire, and diluted with alcohol or acetone, and then a sufficient amount of paste-like BNi68CrSiWB solder can be applied to the alloy powder superior. When heated to a fixed temperature, the solder melts and moves along the alloy.The powder penetrates into the pores. After cooling, the joint is formed with a new alloy in which alloy particles are evenly involved.

3. Selection of process parameters Cold vacuum degree is required to be higher than 8×10-3Pa for iron and cobalt-based high-temperature alloys, and higher than 5×10-3Pa for nickel-based superalloys. The heating rate, below 500C, requires slow heating and a proper stable period of time at this temperature to ensure that the binder in the solder has time to volatilize and the gas in the crack can be removed. From 500C to the solidus temperature of the solder, the heating rate can be selected according to the size of the workpiece, the required diathermy time, and the control deformation; at the same time, it should be stable for a certain period of time at 30~50C below the solidus temperature of the solder to make the parts list The temperature gradient is reduced. From this temperature to the brazing temperature, the heating rate can be faster to avoid the segregation of the solder components, resulting in an increase in the melting point of the solder. The refilling time depends on the filler material used, and the thickness of the workpiece and the heat treatment requirements of the material must be taken into account, usually 15~25min. After soldering, it should be cooled to below the solidus temperature of the solder along with the furnace, and then fast cooling or slow cooling should be performed according to the heat treatment requirements of the material.

Learn more:

High Temperature Vacuum Brazing Furnace

Low Temperature Vacuum Brazing Furnace

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