What Are Brazing Torches?

Flame brazing is divided into flame brazing and flame brazing. Flame brazing. Welding uses a flame that is combusted with combustible gas and oxygen or compressed air as a heat source. Flame brazing equipment is simple and easy to operate. Multiple flames can be used for simultaneous heating and welding according to the shape of the workpiece. This method is suitable for the welding of small and medium pieces such as bicycles, electric frames, and aluminum kettle nozzles.

Flame brazing is performed by using a flame formed by combusting a gasified product of a combustible gas or a liquid fuel with oxygen or air for brazing heating. Flame brazing is widely used. It is versatile, the process is relatively simple, the operation technology is easy to master, and it is easy to realize automatic operation; the initial investment of the equipment is low, the types of combustion gases are many, and the source is convenient and reliable; the flame brazing is completed in the air, and no protective gas is required It is usually necessary to use a flux; a wide range of solders can be used, from low-temperature silver-based solders to high-temperature nickel and copper-based solders, and there is almost no requirement on the shape of the solder, filamentous, flake-like Pre-formed or pasted solder can be used in flame brazing.

Flame brazing also has some disadvantages. For example, flame brazing is performed in an oxidizing environment. After the brazing, there are flux residues and hot scale on the surface of the joint. The heating temperature is difficult to grasp during manual operation, so workers need higher skills. Level; not suitable for brazing easily oxidizable metals such as titanium and zirconium; flame brazing is a local heating process that may cause stress or deformation in the base metal. Flame brazing is mainly used for brazing carbon steel and aluminum alloy with copper-based solder and silver-based solder. Thin-walled and small weldments of low-alloy steel, stainless steel, copper and copper alloys are also used to braze aluminum and aluminum alloys with aluminum-based solders.

The gas used for flame brazing can be acetylene, propane, petroleum gas, atomized gasoline, gas, etc. The combustion-supporting gases are oxygen and compressed gases. The flame has a two-layer structure. The light blue crown flame on the outer layer is an oxidizing flame, which is completely burned, the highest temperature, rich in oxygen, and excessive heating can easily oxidize the metal surface of the workpiece; the inner core of the deep blue flame is a reducing flame, which has a lower temperature Anoxic, carbon monoxide-rich, protects metals from oxidation.

Oxyacetylene flame is the most commonly used flame. The temperature of the inner flame zone of oxyacetylene flame is the highest, which can reach more than 3000 , so it is widely used in gas welding. However, it is only necessary to heat the base material to a temperature higher than the melting point of the brazing material during brazing. Therefore, the outer flame of the flame is usually used for heating, because the flame temperature in this area is relatively low and the volume is large, and the heating is relatively uniform. Generally, neutral flame or carbonized flame is used to prevent oxidation of the base material and the solder.

When the heating temperature is not required to be too high, compressed air can be used instead of pure oxygen, and propane, petroleum gas, and atomized gasoline can be used instead of acetylene. The temperature of these flames is low, and the flames that do not use acetylene will not pollute the flux, and are suitable for brazing relatively small workpieces as well as aluminum and aluminum alloys.

The main components of flame brazing equipment include gas sources, valves, hoses or piping systems for gas transmission, welding torches, nozzles, safety devices and other auxiliary devices.

1. Manual flame brazing equipment

The equipment used for manual flame brazing is essentially the same as the oxygen-gas welding equipment, the main difference is the nozzle, so the structure of the nozzle is mainly explained here.

The various flame brazing nozzles are determined according to the torch size, the size of the workpiece to be heated, and the selected gas. The nozzle is usually made of a copper alloy. Nozzles for acetylene or hydrogen are flat; nozzles for propane or liquefied petroleum gas have a concave surface at the nozzle to prevent lateral wind from extinguishing the flame.

Before brazing, the surface of the workpiece must be cleaned strictly. The flame is then adjusted and heated in the brazed area. When brazing, it is necessary to maintain a uniform temperature, especially the temperature on the joint surface must reach the brazing temperature uniformly, so it should be maintained at the brazing temperature for a period of time as much as possible to complete the brazing material to the joint gap. Passion and precipitation of gas. In order to achieve this, the welding torch is constantly oscillated during the manual brazing process; in an automated operation, the workpiece is oscillated and rotated when it passes through the heating zone, or the flame is moved around the workpiece.

In manual flame brazing operations, feed-in and brazing materials are usually used. In automated flame brazing operations, prefabricated brazing materials or fluxes can be used. When the solder wire is sent to the joint by hand, the solder wire is immersed in the flux first, and then the solder is applied to the joint with the solder. After the solder, if there is a phenomenon that hinders the flow of the solder, it can also be compensated by increasing the flux, while controlling the heat to make the molten solder flow through the joint. After brazing is completed, the joint must be cooled below the solid phase line of the solder in a static state to prevent the joint from cracking. ^[2]