The argon welding method (TIG system) is mainly used for working with thin-walled workpieces with a thickness of not more than 6 mm. According to the configuration of execution and the types of metal available for maintenance, this technology can be called universal. The limitations of the scope of argon welding are determined only by its low efficiency in working with large volumes. The technique focuses on high precision operations, but with large resources.
General principles of technology
This is a type of manual arc welding, which uses a tungsten electrode in a shielding gas environment. By means of an arc excited between the electrode and the target workpiece, the melt is carried out. During operation, the gas supply and the correct direction of tungsten should be ensured. To obtain a high-quality weld, the gas mixture must flow continuously and without interruptions, but slowly. One of the basic principles of argon welding is to manually perform work manipulations, but depending on the technological support, for example, the process of sending filler material can be automated. Gas is selected based on the characteristics of the metal being welded. Often use helium and argon, hence the name of the method. In the case of porous preform structures, protective gas baths with oxygen supply up to 3-5% are used. Such an additive increases the protective properties of the weld from cracking and exposure to atmospheric air. In this case, pure argon as such is not able to create a barrier to the passage of moisture, dirt and other particles, which can have a direct negative effect on the formed structure of the weld. Foreign sources can also be external environmental factors and a poorly cleaned surface of the part.
TIG welding machine
Inverters or transformers are used as a current source. More often - the first, because they differ in a more ergonomic device and optimized for most typical tasks characteristics. Inverters can operate in two modes - with the supply of direct or alternating currents. To service solid-state metals (for example, steel), direct current is used, and for soft (aluminum and its alloys) - alternating current. A modern device for argon welding is provided with the ability to fine-tune the current, has protection against overheating and overvoltage, and in some versions, a display with a reflection of all the main parameters. Recently, modifications are also in demand with facilitated ignition of the arc and stabilization of welding parameters. These are the Hot-Start and Arc-force functions, respectively.
Equipment specifications
Inverters are selected according to voltage, mass, power, welding current spectrum, the presence of certain functions and sizes. The average ranges of the main operational parameters of the apparatus for argon welding can be represented as follows:
- Power - from 3 to 8 kW.
- The current values are minimum 5-20 A, maximum 180-300 A.
- Voltage - 220 V for household models and 380 V for industrial.
- Weight - from 6 to 20 kg.
To perform simple operations, inexpensive models with a maximum current of about 180 A are used. Moreover, such equipment lacks power and is usually compensated by a high coefficient of turn-on time - on average 60-70%. This means that the operator will be able to work for 7 minutes without stopping the process and, for example, rest for 3-4 minutes. Professionals mainly use powerful devices that operate on three-phase networks of 380 V. The advantages of such devices include the possibility of welding with power surges up to 15%, smooth adjustment of current strength and an efficient cooling system.
Additional equipment
In addition to the current generator, a gas mixture cylinder, a burner, electrodes and a filler wire will be required. The cylinder has a reducer in the design with adjustment of the gas supply volume and a hose connected to the tool. For direct shielding gas use a gun burner. It connects to the cylinder hose and secures the tungsten electrode in the holder. Buttons for turning on the gas and current supply are provided on the torch handle. The parameters of the torch for argon welding are selected both for the format of the electrode and for the requirements for servicing the target part. Dimensional and structural characteristics, nozzle throughput, etc. are taken into account. As for the filler wire, it is not always used - usually in cases of working with thick carbon metal workpieces. This is a metal bar, which also lends itself to welding.
Conditions for obtaining high-quality welding
Mostly the success of the operation will be supported by the skills of the contractor. An experienced master is distinguished by the ability to hold the burner in the correct position for a long time, as well as to perform the correct supply of filler materials if they are required in solving a specific problem. In addition to the skills of the master, the quality will be determined by the observance of welding technology. There are many nuances and subtleties both in the organization of the process, and during the physical performance of the work. For example, not everyone knows that the burner must be held at an angle of 20-40 ° relative to the direction of thermal action. Ignoring this rule, you can get a fragile and unreliable connection. Also, the apparatus for argon welding is of great importance in obtaining a high-quality result. And the point is not even in the technical and operational parameters, but in the reliability of the tool, the ergonomics of its design and the effectiveness of the functional.
Preparation of material for welding
Before welding, clean the surface of the target part. At the first stage, physical processing is performed, and then degreasing. Oil and grease stains are removed with acetone or solvents for metal surfaces. There is another trick associated with the preparation of parts with a thickness of more than 4 mm. The so-called edge cutting is performed. They are beveled so that the weld pool can subsequently be below the surface of the part. This will allow you to more effectively form a connecting seam. Before working with sheet material, a flanging technique is also used, in which the edge is bent at a right angle. In order for argon welding to leave behind a minimum of piercing and deformation, the oxide film is also removed from the workpiece. For this operation you can use abrasive materials with tools. For example, in a manual process, a file or sandpaper is often used.
The working process
The mass cable is attached to the workpiece, the burner is connected to the inverter and the gas cylinder. The master takes the torch in one hand, and the filler wire in the other. Next, proceed to configure the operating parameters of the equipment. It is necessary to establish the optimal current strength based on the parameters of the part. How to choose the best mode? In the case of large-format base steels and their alloys, argon welding is carried out with direct current of direct polarity. If we are talking about non-ferrous metals, then alternating current with reverse polarity will create optimal conditions. Before the immediate start of the operation, it is necessary to turn on the gas mixture for about 15-20 seconds. After that, the nozzle of the burner is brought to the surface of the part, and the distance from the electrode should be 2-3 mm. An electric arc will form in this gap, which will further provide a melt of the edge and filler rod.
Features of working with titanium
In the case of titanium, the difficulties are caused by its chemical activity, which occurs when interacting with a gas mixture. In particular, oxidation occurs during the melt, a solid film is formed, and hydrogen reduces the quality of the weld. Moreover, due to the low thermal conductivity of titanium, there is a need for secondary suturing around an existing joint, which is provided during the first pass by argon welding. With your own hands, you can perform high-quality processing of this metal using a combination of tungsten electrodes and a filler rod, maintaining an angle between these elements of 90 °. At least this recommendation can be used when working with sheets from 1.5 mm.
Features of working with copper
The problems of welding this metal are partly similar to those discussed above. In the course of the work, the same oxidation is observed, leading to an inhomogeneous weld. There are other features associated with the acidification of the copper billet due to the reaction with hydrogen. Vapors are formed that fill the structure of the junction, which logically leads to the preservation of air bubbles. How to cook argon welding of copper, to eliminate similar effects? Work only with reverse polarity or alternating current. The gas used is argon, and the electrodes are not tungsten, but graphite. In contrast to titanium welding, the method of edge melting without a filler rod is used.
Features of working with aluminum
Perhaps this is the most capricious metal in welding, which can be explained by the complexity of shape retention during melt, high oxidizability, high thermal conductivity and a tendency to crack, dents and other defects. The argon mixture in this case will not only fulfill the role of protection against oxygen, but will also act as an activator of the conductive plasma. During heating, a refractory layer will form, which will need to be destroyed under conditions of reverse polarity or alternating current. In many ways, the quality of argon welding of aluminum will also depend on the degree of intensity of the direction of argon. So, in working with an aluminum sheet 1 mm thick with a current strength of not more than 50 A, the inert gas consumption will be 4-5 l / min. Thick parts of up to 4-5 mm are cooked at a current strength of 150 A with an argon supply of up to 8-10 l / min.
Welding Safety Precautions
Even with insignificant in scope of work, a whole range of protective measures should be provided, including the following:
- To prevent thermomechanical effects in the form of splashing of the melt with contact with the skin, it is necessary to use special equipment - a jacket, pants, gloves and arm ruffles made of heat-resistant dense fabric.
- The risk of fire during argon welding should be minimized by cleaning the workplace from flammable substances and objects. The equipment, its connection channels are carefully checked, and gas communications are pre-blown.
- The issue of electrical safety is also important. The equipment must be dielectric coated, and the wiring must be earthed and protected against short circuit.
Advantages and disadvantages of the method
One of the main advantages of the technology is its versatility and ability to work with different metals at high speed. As already mentioned, even alloys that are afraid of interaction with oxygen can be successfully serviced under certain conditions. Another plus is expressed in a protective gas environment, due to which the risk of pore formation and foreign inclusions in the weld structure is reduced. In many situations, it is necessary to protect the work area as much as possible so that the rest of the surface remains intact. And in this sense, argon welding will be the best solution, since heating is carried out locally and does not deform third-party elements and structural details. If we talk about the shortcomings, then they are few. Firstly, it is the complexity of the physical execution of the task, which requires certain skills and knowledge. Secondly, a high network load with high power consumption is inevitable.
Conclusion
Anyone can implement TIG welding today by purchasing the appropriate equipment and consumables. For everyday tasks in the household, for example, you can get the Resanta apparatus SAI 180 AD, which will allow you to perform functional and efficient argon welding. Equipment of this type with a current strength of 180 A costs about 18-20 thousand rubles. Professionals are recommended models like the Svarog TIG 300S and FUBAG INTIG 200 AC / DC. They are distinguished by high power of about 6-8 kW, a current of 200 A, but they cost at least 25 thousand rubles. Such welding equipment is often used in construction, specialized auto repair shops and in large industries.