The essence of the action of technical gases when welding
There are many kinds of welding. The division is based on the method of obtaining a high-temperature weld pool( energy type).For example, welding with electric arc, ultrasound, gas flame and others. Such a burner can cut and weld any metals. The edges of the welded metal parts are literally melted and, when combined, form a new single structure in the place of the alloy, called the welded seam.
Welding gases include, first of all, acetylene for welding, which is released as a result of reaction with water of calcium carbide. Mixed with oxygen, it allows you to obtain a flame temperature of over three thousand degrees.
Welding is also considered propane, butane, liquefied MAF( new gases, replaced acetylene), benzols, kerosene and others. An important feature of the use of welding gases will be the mandatory presence of oxygen, as a combustion catalyst. Moreover, the developed temperature depends on the quality( purity) of oxygen supplied to the burner.
What should be the gas mixture for welding?
A gas mixture for welding with the use of technically pure oxygen gives very intensive and complete combustion of the mixture itself or the evaporation of combustible substances, since it provides very high combustion temperatures. The amount of oxygen in the flame will determine its oxidation or reduction properties.
On the other hand, the use of technical( pure) oxygen requires special cylinders for its storage and delivery. In a mixture with such oxygen, some gases or compositions may prove explosive( due to the extremely high rate of their combustion in such a catalyst).
Often they can and in themselves be dangerous because of their toxicity. For example, acetylenes, dicyans, and the like.
The use of oxygen contained in atmospheric air makes welding gas mixtures less effective. Their combustion slows down, which dramatically reduces the temperature of the flame. The reason is that in air oxygen is no more than a fifth of it, more gases are present, more nitrogen, for example.
In addition to the above, welding with atmospheric oxygen often does not give the required geometry of the joint, changes the properties of the metal in this zone, which ultimately affects the quality of the joint.
Protective gases - what is it and what do they serve?
Technical gases are used not only in welding. The use of various inert gases( helium, argon) or active( nitrogen, CO2, hydrogen, oxygen) gases as a protective medium for the weld pool significantly improves the quality of the result, increases the speed of work,allows you to get the right seam parameters, etc.
The principle of welding in a protective gas environment is simple. The desired composition is fed into the arc zone through the nozzle of a special burner under pressure, creating this most protective environment. This principle is based on popular welding on semi-automatic machines.
Such welding is available not only in the factory, it is widely used in workshops and even in private garages. More often, gas for welding semi-automatic is a mixture of inert and carbon dioxide( in various proportions).From inert gases helium and argon are more applicable. In practice, the use of argon is accepted, therefore, CO2 and argon are present in the composition.
Generally, an inert gas for welding is needed to protect the melt of the bath from external exposure to air, as well as in the case of high-quality welding operations on stainless steels, titanium and its alloys, non-ferrous metals( nickel, copper, aluminum and alloys)In this case, the electrode can be any: classical melting, not changing its shape and structure( serving to create an arc), etc.
The choice of the gas needed for welding is influenced by which metal is used in operation. The same mixture of CO2 and argon in the welding of steel elements contains more carbonic component( about 18%).And when welding stainless steels, argon predominates( 98%), CO2 is only two percent.
Thus, which gas is used for welding, is determined by the metal, its brand, the necessary properties of the seam, the types of welding equipment, the requirements for the chemical composition and even the form of the joints, the working conditions, etc.