Vacuum brazing furnace has a flow phenomenon during operation

What is the flow phenomenon of the vacuum brazing furnace? How is it formed, how to solve it? To solve these problems, first understand what is the flow? What are the reasons for the flow?

What is the flow? Diffuse flow refers to the thin solder coating formed by the solder flowing through the brazing joint on the base material during brazing.

vacuum coating machine,pvd coating machine,pvd vacuum machine,vacuum ion coating machine,multi-arc ion coating machine

First, the cause of the flow

The fixture should have a certain degree of elasticity and rigidity at the brazing temperature, so that there is a suitable gap at the weld joint to form a capillary phenomenon to absorb the molten solder. The tooling clamp is not tight, and the gap of the brazing assembly is too large to keep the solder, and the flow defects are generated. The tooling has a low degree of rigidity, and the thermal deformation and gravity caused by heating cause the joint of the brazing assembly to increase, and the capillary phenomenon which cannot form the brazing material also causes the brazing material to flow.

Vacuum brazing is radiation heat transfer, the heat capacity of the fixture is large, the heating rate of the brazed parts is small, the residence time of the brazing material in the solid-liquid phase temperature range is long, the low melting point component of the brazing material is more volatile, and the flux is The action time is also long, which further destroys the surface tension of the liquid solder and excessively improves the wettability of the solder to the base material.

The amount of furnace is large, the temperature of the lifting and lowering is small, the holding time is long, and the heat capacity of the fixture is the same. The solder has a long residence time in the liquid state, and the slow cooling rate is equivalent to prolonging the holding time of the solder liquid, and also generates a flooding flow. The function of the flux is to reduce the oxide film on the surface, reduce the surface tension of the liquid solder, and improve the wettability of the solder to the base material.

vacuum coating machine,pvd coating machine,pvd vacuum machine,vacuum ion coating machine,multi-arc ion coating machine

The flux is used in a large amount, and the wettability of the solder to the base material is too good, resulting in the flow of the solder. The high temperature of the holding, the surface tension of the liquid solder is small, and the effect of the flux reducing the surface tension is enhanced, and the combined effect of these factors causes the flow of the solder. The workpiece stays in the solid-liquid phase temperature range of the solder for a long time and causes a flow.

Second, how should we solve the phenomenon of flooding?

vacuum coating machine,pvd coating machine,pvd vacuum machine,vacuum ion coating machine,multi-arc ion coating machine

It can increase the clamping force of the tooling and reduce the connection gap of the brazing assembly.Improve the rigidity of the fixture, and ensure that the joint gap does not change when the state is hot. The hollowing out reduces the weight of the tooling or replaces part of the steel with graphite to reduce the heat capacity of the tooling. Reduce the amount of flux, and reduce the amount of flux in the case of continuous brazing. The staged lifting and lowering temperature is adopted to rapidly raise and lower the temperature in the solid-liquid phase temperature range of the brazing material, shorten the brazing holding time, reduce the brazing holding temperature and reduce the amount of furnace charging.