Welding Certificates: The Protective Gas Mixture

The most common welding are the following protective gas mixture:

mixture of argon and carbon dioxide;
mixture of argon and oxygen;
mixture of carbon dioxide and oxygen.

A mixture of argon and carbon dioxide
The use of a mixture of argon and carbon dioxide (usually 18-25%) is effective for welding low carbon and low alloy steels. In comparison with welding in pure argon or carbon dioxide is more easily achieved by inkjet transfer of electrode metal. Welds are more plastic than when welding in pure carbon dioxide. In comparison with welding in pure argon is less likelihood of the pores.

A mixture of argon and oxygen
The gas mixture of argon and oxygen is commonly used in welding alloy and carbon steels. Adding a small amount of argon, oxygen helps prevent porosity.

A mixture of carbon dioxide and oxygen
When you add oxygen to carbon dioxide is reduced spatter during welding, improves the formation of the joint, increases heat, which to some extent increases the productivity of welding. On the other hand, as a result of increased oxidation deteriorate the mechanical properties of joints.

Mixing of gases
Typically, gas mixtures are prepared directly on the welding stations, but also apply multioperator supplying gas mixtures and mixtures to obtain the manufacturer.

The simplest method of mixing is based on using rotameters. The composition of the mixture is regulated by changing the gas flow by means of gears mounted on cylinders with gases. Value is determined by the pre-scaled gas rotameter float on the situation. Rotameter consists of a conical glass tube placed in a metal frame. Inside the glass tube is placed a float made of aluminum, hard rubber or corrosion-resistant steel (see figure below).

Float type flowmeter

The principle of the flowmeter is based on balancing the weight of the float leaving a stream of gas. The higher the float rises, the greater the annular gap between the side surfaces and the glass tube, and therefore more gas.

Used in the production of more convenient gas taps for the binary and ternary mixtures. For example, a standard faucet UCP-1-71 is designed for mixing carbon dioxide and oxygen in a ratio of 70% and 30%. For other gases, and other relations to find the corresponding diameters of the holes in the nozzles and consumables protarirovat mixer.