Welding has been known for a long time. It has found application in various industries, as well as in construction. With the help of welding you can connect parts from different metals. It can be cast iron, steel, iron, aluminum. Welding is divided into several varieties. This includes manual arc, automatic and semi-automatic. Often used welding semiautomatic argon. The latter is an inert gas that protects the weld and improves the quality of the connection.
Argon welding scheme.
The semiautomatic device allows to optimize the technological process, since the welding wire feed is carried out directly by the apparatus itself, whereas during the manual process, the welder organizes all the work. Semi-automatic welding has its positive and negative aspects that you need to know when organizing work. Let us consider in more detail the features of the connection of metal products in the presence of a protective argon gas.
What is semi-automatic welding?
Few know what a semi-automatic is. It is a unit that includes several components: a mechanism for advancing and feeding the wire, a torch, a starting device and a power source. Until recently, devices such as transformers were widely distributed. They allowed to translate the current in the network in AC or DC, depending on the type of unit. Currently, there are new devices. The semiautomatic argon welding machine may vary in performance. Depending on its size and ability to move, stationary, portable and mobile units are distinguished. Of great importance is the method of protection of the welded joint.
Diagram of the process of aluminum welding semiautomatic.
On this basis, the semiautomatic device can work with the participation of protective gas or special flux-cored wire. In the first case, the gas is represented by carbon dioxide, argon, helium. Argon is widely used for welding aluminum products. It is important that the equipment is divided by the type of wire fed. The latter is solid steel, aluminum or universal. If during manual welding a welder selects electrodes, then in this situation they will not be required. Welding is carried out with wire, the diameter of which depends on the type and thickness of the metal.Back to table of contents
Advantages and disadvantages
Why do so many welders prefer it is a semi-automatic process using argon? Positive aspects include:
- the ability to connect products from non-ferrous metals and alloy steel;
- the ability to weld thin products (up to 0.5 mm);
- optimal arc burning and melting depth;
- the formation of a more even and high-quality seam;
- the ability to work at low current;
- reducing the release of toxic substances into the air of the working area due to blowing with argon;
- less slag formation.
Scheme of the device welding semiautomatic.
Inert argon gas is required in order to protect the weld from oxidation. If during the manual process the surrounding air can oxidize the metal, then during argon welding the risk is significantly reduced, and the joint is more durable, without cracks and other defects.
As for the negative sides of argon welding, there are very few of them. The disadvantages include more intense splashing of the molten metal, low productivity and more powerful radiation. In the latter case, it is a negative impact on the organs of vision of the worker. If security measures are taken, this effect can be reduced.Back to table of contents
Features of welding in argon
Argon in the process of welding can be used both in pure form and in combination with other protective gases. The peculiarity of argon is that it is an inert gas, that is, it does not enter into chemical interaction with a metal product. In addition, it protects the weld from oxidation. This is especially important when welding non-ferrous metals. The latter are easily oxidized when interacting with air. The main oxidants in the air are nitrogen and oxygen. Argon, in turn, displaces these gases from the welding zone, as a result of which the porosity of the metal being welded decreases and a stronger weld is obtained.
Scheme of jet protection during argon-arc welding.
Argon welding has its own characteristic features. First, argon is used with both consumable electrodes (wire) and non-consumable electrodes. Secondly, the welder may not clean the surface of the welded product from oxides. This is especially true for aluminum. Thirdly, aluminum wire is suitable for welding aluminum. Its diameter is 1-2 mm. As for the mode of operation, the wire feed speed should be equal to from 150 to 650 m / h. The strength of the welding current is not more than 300 A.
Fourthly, for welding it is necessary to stock up with a sufficient amount of gas (argon). The filled cylinder contains about 6000 liters of argon. It is important that in this mode of operation the gas flow will be equal to at least 300 l / h. It is possible to choose the optimum mode of the equipment, based on the instructions for the semiautomatic device. The strength and speed of the wire will depend on the thickness of the metal.Back to table of contents
Argon welding technology
The process of connecting parts in an argon environment begins with an equipment readiness check. To do this, you need to adjust the operating mode of the machine, adjust the current strength, voltage and speed of the wire. For aluminum wire, it is preferable to use a pulling type feeder. Pushing is often used for steel wire. If the metal thickness is less than 3 mm, then the optimum current strength is 120-145 A. The speed of the wire will be 900 m / h.
Do not forget about polarity.
In most cases, a direct current having a reverse polarity is applied.
Table of physical properties of gases for welding.
This means that “-” is supplied to the product, and “+” to the torch with wire. The preparatory stage involves cleaning the surface of products. If they are made of aluminum, the edges are treated with acetone and then brushed with a metal brush. This is done to remove the surface film, which complicates the welding process.
After everything is prepared, the switch that feeds the wire is turned on in the working position. Further the electric arc is ignited. In the presence of a melting wire, just touch the metal. When the arc is lit, it is recommended to check the selected welding mode on any unnecessary product. If everything is OK, then continue welding. The movements of the burner nozzle should not be transverse, it should only be moved in one direction. The best option - welding parts at high speed with a single layer of seam. With a large metal thickness it is required to be heated. The temperature should reach 150-300 °. If it is required to weld vertical products, then the nozzle needs to be moved from top to bottom.Back to table of contents
Cast Iron Welding
Argon is used not only when working with non-ferrous metals. Often it is necessary to weld cast iron or steel. Cast iron is an alloy based on iron and carbon. Cast iron is very difficult to weld due to the fact that the resulting welds tend to form cracks. In addition, pores may form.
Another feature is the ability to oxidize rapidly. For welding cast iron products, cored wire is best suited. As for argon, it ensures the formation of welds on the product without slag. An interesting fact is that the combination of metal products made of cast iron is used in the repair process of cars of old production.
Cast iron is welded on a tungsten wire. Very often used metal heating. It is common and local. The cold method also applies. For welding cast iron is suitable both direct and alternating current. The strength of the current is determined by the thickness of the material and the diameter of the wire. On 1 mm of a wire it is necessary from 50 to 90 And current. The wire can be taken graphite, cast iron, based on copper and iron, nickel.Back to table of contents
List of tools and materials
For the organization of such work will need equipment. It includes cylinders with argon, semiautomatic, wire of the desired diameter. To prepare the metal, you will need a rag, brush, hammer, chisel, acetone solution.
The welder must work in protective clothing. It is necessary to use means of individual and collective protection: ventilation, current earthing system, fencing, mask or shield, mittens, shoes. It must be remembered that it is impossible to weld products on the surface of which there are combustible-lubricating substances. Thus, semi-automatic welding in argon allows for a strong connection and an excellent weld.