Technology of semi-automatic welding in gaseous environments is one of the most popular methods of joining metals today. This technique allows you to perform high-quality joints with a minimum amount of rejects and damage to the internal structure of the workpieces. Especially appreciated is carbon dioxide welding, which eliminates the need for flux and provides even, tight seams.
Technology Features
When performing gas welding of this type, almost all positions of the direction of the arc to the target workpiece are allowed. That is, in terms of organizing the process from the point of view of the electrode layout, there are no special differences from other methods of semi-automatic welding. But there are other factors that distinguish the installation process in a carbon dioxide environment:
- Possibility of forming a high-density seam with a minimum content of foreign inclusions.
- Increasedpower requirements. In terms of energy costs, this is one of the most expensive methods, which is explained by the high requirements for thermal support of the arc.
- The ability to use not only semi-automatic, but also fully automatic mode.
- You can weld thin sheet metal using electrical rivets.
Many features of semi-automatic carbon dioxide welding are due to the characteristics of the electric arc that is ignited when the welding wire touches the target part. The post-holding technique of the consumable with electrodes is also quite flexible and pliable for the operator, which expands the range of operational possibilities.
Scope of the method
Due to the convenience and manufacturability of carbon dioxide thermal exposure, this welding method is used in a wide variety of areas of construction, industry and utility services. Among the main directions are the following:
- Engineering.
- Shipbuilding and ship repair activities.
- Installation work.
- Construction, connection and repair of pipelines of various sizes.
- Production of apparatus and boiler equipment.
- Metallurgy and, in particular, welding damage on steel castings.
The simplest schemes for carbon dioxide welding by inverters are also widely used in the domestic sector, when you need to make connections in a car body, restore a metal roof orrepair the iron frame.
Characteristics of carbon dioxide protective environment
Semi-automatic welding as such is the basis on which heat treatment in a gas environment can also be implemented. There are many such methods and the use of carbon dioxide is only one of the variations of the general technique. What is the difference between the considered gas mixture? The working process uses liquid carbon dioxide (liquefied gas), which is under high pressure up to 70 atmospheres. Storage is carried out in 40-liter cylinders, but in working operations (especially remote ones) smaller containers may be involved. For comparison, 25 kg of mixture is enough for 15-20 hours of work, although the specific consumption will depend on other process characteristics.
More importantly, carbon dioxide for welding should have a CO2 concentration of about 98%, and when performing high-precision operations - from 99%. The moisture factor in the composition will be decisive in terms of the quality of the seam. Exceeding the normative indicators of moisture contributes to an increase in the splashing of the melt. However, to minimize this factor, experienced welders use special dehumidifiers based on copper sulphate or silica gel with aluminum.
CO2 welding equipment
A standard set of basic technical and auxiliary tools for welding of this type provides for a semi-automatic device (inverter), a power source, a container withgas mixture and wire (or electrodes). The device for semi-automatic welding is selected according to the characteristics of power, current strength and additional functionality with elements of regulation and automatic protection against overloads and mains overvoltage. It can be said that this is the central complex for managing the entire process. From the point of view of regulation, the reducer for carbon dioxide welding is also important, through which the operator can lower or increase the output pressure - for example, up to 0.5 kg/cm2. As for the wire, it is fed through a special nozzle with a diameter of 15-25 mm. For the convenience of this procedure, it is also recommended to provide special rectifiers and automatic feeders for consumables.
Preparation for work
Preparatory activities consist of several stages. First you need to pass the wire through the sleeve of a gas burner connected to a cylinder of carbon dioxide. To do this, the nozzle is removed from the torch, then the tip is unscrewed and the clamping mechanism is released from the wire feeder. Further, in a free position, the wire is passed along the entire sleeve to the nozzle. This is followed by another task - determining the optimal polarity of the current. How to set up carbon dioxide welding according to this parameter? In the normal mode of welding with wire and carbon dioxide, the plus goes to the torch, and the minus goes to the clamp. In this configuration, the heat release point will be located directly on the metal workpiece. Polarity must be straight when using flux-cored wire.
It is important to take into account the nuances of pressure regulation when supplying gas through the reducer. Excessively active supply of the mixture at high pressure at times extinguishes the flame, which will not allow the formation of a stable protective environment. On the other hand, insufficient power when pushing carbon dioxide under low pressure will make the gas shielding effect insufficient, resulting in a seam that is not strong enough.
Welding process
The semiautomatic device is connected to the network when all settings of the burner, gas cylinder and wire are prepared. A charge of the required polarity is directed to the point of convergence of the wire and the surface of the workpiece, against which an electric arc is formed. How to cook with carbon dioxide welding? The operator is required to perform two functions. First, maintain the optimal distance of the wire from the welding zone so that the arc is stable and does not break. Secondly, it is necessary to try to minimize the splashing of the melt, since this effect directly affects the protection of the weld pool. Both conditions are met by balanced gas supply, pressure regulation and correct wire guidance. In general, it is necessary to protect the seam from oxygen due to the carbon dioxide environment and at the same time not to let the arc go out due to lack of power.
Advantages of Technology
The whole operation may seem technologically complex both in terms of organization and method of execution. However, labor and time costs are offset by the following advantages of carbon dioxide technology.welding:
- The speed of forming a seam in thin sheet steel increases several times compared to other semi-automatic welding techniques.
- The structure of the seam is durable and even surface - of course, subject to the skillful operation of the master.
- Due to the minimum deformation of the workpiece, machining operations after welding are practically eliminated.
- If we compare the technology with manual welding methods, then the advantages of this method include a high degree of protection against air, the ability to visually control the process, low cost of work and ergonomics.
Conclusion
The method of carbon dioxide treatment of metal blanks in a thermal bath is attractive for many reasons. But how does it justify itself in everyday life, because its use requires quite serious preparation? With your own hands, carbon dioxide welding can be implemented using an inverter costing about 8-10 thousand rubles. Auxiliary equipment with consumables will also cost a similar amount. Compensating for these costs is a high-quality seam, which may be required, for example, in the repair of a car body.
