Semi-automatic welding technology in gas environments today is one of the most popular methods of joining metals. This technique allows you to perform high-quality joints with a minimum of scrap and damage to the internal structure of the workpieces. Carbon dioxide welding is especially appreciated, eliminating the need for flux and providing even tight joints.
Technology features
When performing gas welding of this type, almost all positions of the arc direction to the target workpiece are allowed. That is, in terms of the organization of the process from the point of view of the arrangement of the electrode, there are no special differences from other methods of semi-automatic welding. But then there are other factors that distinguish the installation process in a carbon dioxide environment:
- Possibility of formation of a high density weld with a minimum content of foreign inclusions.
- Increased power requirements. In terms of energy costs, this is one of the most costly methods, due to the high requirements for thermal support of the arc.
- The possibility of using not only semi-automatic, but also fully automatic mode.
- It is possible to cook sheet metal using electrotechnical rivets.
Many features of semi-automatic carbon dioxide welding are due to the characteristics of the electric arc, which is excited when the welding wire touches the target part. The technique of subsequent holding of the consumable with electrodes is also quite flexible and flexible for the operator, which expands the range of operational capabilities.
Method application areas
Due to the convenience and manufacturability of carbon dioxide thermal exposure, this welding method is used in various fields of construction, industry and economic and engineering services. Among the main areas are the following:
- Engineering.
- Shipbuilding and ship repair activities.
- Installation work.
- Construction, connection and repair of pipelines of various calibers.
- Manufacture of apparatus and boiler equipment.
- Metallurgy and, in particular, welding damage to steel castings.
The simplest schemes of carbon dioxide welding by inverters are widely used in the household sphere, when you need to make connections in a car body, restore a metal roof or repair an iron frame.
Characteristics of carbon dioxide protective environment
Semi-automatic welding as such is a base on which heat treatment in a gaseous medium can be realized. There are a lot of such methods and the use of carbon dioxide is only one of the variations of the general technique. What are the differences between the gas mixture in question? In the working process, liquid carbon dioxide (liquefied gas) is used, which is under high pressure up to 70 atmospheres. Storage is carried out in 40-liter containers, but smaller volumes may also be involved in operations (especially remote ones). For comparison, 25 kg of the mixture is enough for 15-20 hours of operation, although the specific flow rate will depend on other characteristics of the process.
What is more important, carbon dioxide for welding should have a CO2 concentration of about 98%, and when performing high-precision operations - from 99%. Crucial in terms of the quality of the weld will have a moisture coefficient in the composition. Exceeding the normative indicators of moisture contributes to increased spraying of the melt. However, to minimize this factor, experienced welders use special dehumidifiers based on copper sulfate or silica gel with aluminum.
Carbon dioxide welding equipment
A standard set of basic technical and auxiliary tools for welding of this type provides for the presence of a semiautomatic device (inverter), a power source, a container with a gas mixture, and wire (or electrodes). The device for semi-automatic welding is selected according to the characteristics of power, amperage and additional functionality with elements of regulation and automatic protection against overloads and network overvoltage. It can be said that this is the central complex for managing the whole process. From the point of view of regulation, a reducer for carbon dioxide welding is also important, through which the operator can lower or increase the output pressure - for example, to 0.5 kg / cm 2 . As for the wire, it is fed through a special nozzle with a diameter of 15-25 mm. For the convenience of ensuring this procedure, it is also recommended to provide special rectifiers and automatic supplies of 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 carbon dioxide cylinder. To do this, the nozzle is removed from the burner, then the tip is unscrewed and the clamping mechanism is released from the wire feed device. Further in the free position, the wire is passed along the entire sleeve to the nozzle. After this, another task follows - determining the optimal polarity of the current. How to set up carbon dioxide welding by this parameter? In the normal mode of welding with wire and carbon dioxide, plus is directed to the torch, and minus to the clamp. In this configuration, the heat release point will be located directly on the metal workpiece. When using flux wire, the polarity must be straight.
It is important to consider the nuances of pressure regulation when applying gas through a gearbox. An excessively active supply of the mixture at high pressure extinguishes the flame from time to time, which will prevent the formation of a stable protective environment. Conversely, insufficient power in the direction of carbon dioxide under low pressure will make the effect of gas protection insufficient, as a result of which the seam will not be 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 a electric arc forms. How to cook with carbon dioxide welding? The operator is required to perform two functions. Firstly, to maintain the optimum distance of the wire from the welding zone so that the arc is stable and not interrupted. Secondly, you need to try to minimize melt spatter, as this effect directly affects the weld pool security. Both conditions are met through a balanced gas supply, pressure regulation and the correct direction of the wire. In general, it is necessary to protect the joint from oxygen due to carbon dioxide and at the same time not to allow the arc to go out due to lack of power.
Technology benefits
The whole operation may seem technologically complex both in terms of organization and in terms of execution method. However, labor and time costs are offset by the following advantages of carbon dioxide welding technology:
- The weld formation rate in sheet steel increases several times relative to other semi-automatic welding techniques.
- The seam structure is durable and has a flat surface - of course, provided that the operation is skillfully performed by the master.
- Due to the minimum deformation of the workpiece, machining operations are almost excluded after welding operations.
- If we compare the technology with manual welding methods, the advantages of this method include a high degree of protection against air, the possibility of visual control of the process, low cost of work and ergonomics.
Conclusion
The carbon dioxide treatment of metal billets in a thermal bath is attractive for many reasons. But how much does he justify himself in everyday life, because for its use quite serious preparation is required? Do-it-yourself carbon dioxide welding can be implemented using an inverter worth about 8-10 thousand rubles. Accessories with consumables will also cost a similar amount. The high-quality seam, which may be required, for example, in repairing a car body, compensates for these costs.