Welding technologies are used in various fields of human activity. Its versatility has made welding in shielding gases an integral element of any production.
This variety allows you to easily connect metals with a thickness of 1 mm to several centimeters in any position in space. Gradually, welding in a protective environment displaces traditional welding with electrodes.
The essence of the welding process in a protective gas environment
The welding process is used to create a permanent connection of various metals. It is achieved by heating the elements to be connected to a temperature close to the melting point. Warming up is carried out by means of an electric arc, which has a combustion temperature from 7,000 to 18,000 ° C. This allows you to heat the weld metal and form a weld pool, which is filled with a molten electrode.
In order for the electric arc to burn stably, and also so that air does not affect welding, a protective gas is supplied to the combustion zone, which creates a dome that prevents oxidation.
Welding in shielding gases is used where simple welding with an electrode in a coating does not give a result. This is a compound of metals such as:
- copper;
- bronze;
- titanium;
- molybdenum;
- chrome and others
In modern automatic production, mechanized welding in the environment of shielding gases is used. With its help, not only non-ferrous metals are cooked, but also ferrous (varieties of steel).
Method Advantages
This type of welding has many advantages.
- Allows welding of non-ferrous metals. The difficulty of their welding lies in the fact that they have a low melting point with high oxidizability, which pollutes the welding zone with oxides and creates difficulty in obtaining a high-quality weld.
- High temperature heating. This makes it possible to localize the welding zone within small limits. As a result, the metal being welded does not change its mechanical properties due to overheating.
- High performance. Welding in a shielding gas environment makes it possible to automate the process through the use of wire wound around a coil and its automatic feeding.
- Lack of slag. No time is taken to remove it.
Disadvantages of welding in a protective environment
The disadvantages of this type of welding include the bulkiness of the equipment. In addition to the welding machine itself, gas cylinders, gearboxes, gas fittings are included.
Consumables are more expensive than for conventional electric arc welding.
In modern enterprises, the main criterion of economic feasibility is the time spent on production. They introduce automatic welding systems in a shielding gas environment. Therefore, the high cost of materials is offset by high performance.
How strong are welding joints
Welding metals creates a strong connection. It is much stronger than bolting or riveting. Moreover, where it is necessary to create tightness, welding is indispensable. The main limitation in its application is the inability to withstand dynamic loads, which vary both in magnitude and in the impact vector. For this reason, rivets are used in aircraft construction instead of welded joints.
The strength of the weld depends on the materials used, adherence to the technology and proper cutting of the welded edges.
Varieties of equipment used
Shielded gas welding has two varieties:
- Non-consumable electrode. An electric arc is created by a tungsten rod, which does not melt in the process. Material for filling the weld pool is fed manually in the form of a piece of wire.
- Consumable electrode. Here, an electric arc is created by an automatically supplied wire to which electric current is supplied. This wire melts and fills the weld pool, forming a seam.
Depending on this, equipment for welding in shielding gases is divided into two types:
- Welding transformers and inverters equipped with a tungsten-tip torch.
- Semiautomatic welding machines. Now this type of equipment is most widely used. With their help, you can weld the entire spectrum of metals. They are mobile and have great performance. Semiautomatic welding in a shielding gas environment is used both in garages and private farms, and in serious enterprises.
- Laser arc welding. This is a type of hybrid equipment where, in addition to the welding arc from a tungsten electrode, deep fusion with a laser beam is created. In this case, a device is used that combines laser optics and a burner with a tungsten tip.
What gases are used
There are several varieties of gases used, which can be divided into 3 groups: inert, active and combined.
Inert gases include: helium, argon. Helium is lighter than air and more expensive to manufacture, less commonly used. But the arc in it is gaining a higher temperature than in argon, so welding in helium has a higher productivity. It is used for welding alloys of aluminum and magnesium.
Argon has a wider application. It is used for welding critical parts, as well as rare and non-ferrous metals.
Nitrogen can be attributed to conditionally inert gases. It is used only for welding copper and its alloys, in relation to which it is not active.
Although active gases protect the welding zone, they themselves dissolve in the weld metal, changing its composition. These include carbon dioxide and oxygen. CO 2 is used for welding ferrous metals: low- and medium-carbon steels, cast iron, low alloy steels, etc.
Oxygen is only mixed with inert gases.
Combinations of gas mixtures are used in different proportions to increase the stability of the welding process and improve the mechanical characteristics of the weld.
Expendable materials
For semi-automatic welding in a protective gas environment, a wire rolled into coils is used. It has over 80 varieties. Its diameter is from 0.3 to 12 mm. The skeins in which it is folded weigh from 1.5 to 40 kg. The wire is selected with the same composition as the parts to be welded.
The non-consumable electrode can be either tungsten or carbon. A tungsten electrode is a wire with a diameter of 0.5-3 mm or rods with a diameter of 5-8 mm. The material for the additive is a wire with a diameter of 1.6-5 mm.
Preparation for welding
Welding in a protective environment is carried out mainly for welding critical parts. Therefore, the first requirement is a highly skilled worker. To carry out such work, welders of at least 5 categories who are trained and have received an admission are allowed.
Before starting work, regardless of the certificate, the welder is forced to butt-weld a sample that will be tested for strength. GOST welding in shielding gases determines what tensile strength this specimen must withstand.
The welding room should contain a minimum of dust. All types of work with its formation are prohibited (cutting, grinding, grinding work).
The air in the room should be warm and dry. For this, thermometers and hygrometers are installed. The temperature should not be lower than 16 ° C.
Good lighting should give an overview of the welding zone and allow timely detection of defects that occur in different modes of welding in a protective gas environment.
Drafts are not allowed in the room. The air velocity should not exceed 0.5 m / s.
Tips & Tricks
To get a quality connection, you need to do the preparatory work.
- Properly cut the edges of the elements to be welded. The penetration and filling of the weld pool with metal depends on this.
- Thoroughly clean the surface to be welded of dirt and rust.
- Select shielding gas pressure. If the pressure is high, there will be excessive cooling of the welding zone. Low pressure will lead to the formation of pores in the weld.
- Select the optimal current strength. It is selected based on the thickness of the metal being welded. Wire feed is regulated depending on the current strength.
- To obtain a high-quality weld, the burner must be periodically cleaned of scale. If this is not done, then the scale will reduce the internal diameter of the burner, and the protective gas will be supplied to the combustion zone with an incorrect torch. Also, scale will make it harder to feed wire. Silicone can be used to reduce carbon deposits on the burner. It lubricates the inside of the burner. Aerosol cans are very convenient for welding.
Welding in shielding gases is an important process, which largely depends on the human factor. Compliance with safety measures, the use of protective equipment will help not only to perform quality work, but also to maintain health.