Arc welding in shielding gas: description of technology, modes, methods

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Gas shielded arc welding is a method that significantly improves the quality of the work result. This technology has a number of features. Before applying it, the master must familiarize himself with the basics of arc welding, which is carried out in a shielding gas environment. The features of this technology will be discussed later.

Features of the technique

One of the subspecies of the arc connection of metal products, workpieces is gas-shielded arc welding. GOST regulates the process during which gas is supplied to the melting point. It can be argon, oxygen, nitrogen or other varieties. There are certain features of such a process.

Every welder knows that the quality of a weld depends not only on the skills of the welder, but also on the conditions at the melting point. Ideally, only the electrode and filler materials should be present here. If others get hereelements, they can have a negative effect on welding. The soldering point will not be strong enough because of this.

The technology of manual gas shielded arc welding dates back to 1920. The use of such substances allows you to make seams without slag. They are characterized by high purity, are not covered with microcracks. This method is actively used in industry when creating various elements from metal.

Special proportions of protective gases allow you to relieve stress in the melt zone. There are no pores here, which significantly improves the quality of soldering. The seam becomes stronger.

In industrial conditions during welding, rods mixed with argon and carbon dioxide are used. Thanks to this combination, the arc becomes constant, protecting the melt zone from drafts. This allows you to connect thin sheets of metal.

If deep penetration is required, carbon dioxide and oxygen are mixed. This composition has oxidizing properties, protects the seam from porosity. There are many techniques that involve the use of different gases during welding. The choice depends on the specifics of this process.

Welding technique

There are different modes of gas shielded arc welding. Two main methods are used. The first of these involves the use of melting spiers. A current passes through them, and the rod melts because of this, forming a strong seam. This material provides a strong bond.

The second technique involvesconducting arc welding in shielding gas with a non-consumable electrode. In this case, the current also passes through the rod, but the material is connected due to the melting of the edges of metal parts, blanks. The electrode material does not become part of the weld.

During such manipulations, different gases are used:

• Inert. Such substances are odorless and colorless. Atoms have a dense shell of electrodes. This causes their inertia. Inert gases include argon, helium, etc.
• Active. They dissolve in the metal blank, reacting with it. These media include carbon dioxide, hydrogen, nitrogen, etc.
• Combined. Certain processes require the use of both types of gases. Therefore, welding takes place in an environment of both active and inert gases.

To choose the gaseous medium, take into account the composition of the metal, the efficiency of the procedure itself, as well as the properties of the soldering. Other nuances may be taken into account.

With the use of inert gases, the stability of the arc is improved, allowing deep melting. Such substances are fed into the melt zone in several streams. If it runs parallel to the rod, it is a central flow. There are also side and concentric jets. Also, gas can be supplied to a movable nozzle installed above the working medium.

It is worth noting that when arc welding, which takes place in a gas bath, the thermal parameters are acceptable for the production of a weld of the required model, quality and size.

Mode selection

To matchrequirements of GOST, gas-shielded arc welding can be carried out in different modes. For this, in most cases, the use of semi-automatic type inverters is required. With the help of such equipment, it becomes possible to regulate the flow of electricity, its voltage.

Inverter semiautomatic devices serve as a power source. They may differ in power, as well as options. Performance varies by model. For most routine operations that do not require welding of thick or infrequently used alloys, simple machines are used.

Automatic gas-shielded arc welding differs by a lot of parameters:

• Wire radius.
• Wire diameter.
• Power of electricity.
• Voltage.
• Contact feed rate.
• Gas consumption.

Existing semi-automatic modes of gas-shielded arc welding are also divided into local and general. In the first case, the shielding gas flows from the nozzle into the welding zone. This option is used more often. Local welding can join different materials, but the result may not always be satisfactory.

When using a local gas supply, air can enter the melt zone. This reduces the quality of the seam. The larger the workpiece to be welded, the worse the result will be when using this technique.

If you need to weld large parts, chambers are used in which the atmosphere is regulated. Of themair is pumped out, a vacuum is created. Further, the gas required by the technology is pumped into the chamber. Welding is performed using the remote control.

Preparation for welding

In order to properly perform the procedure for joining metal blanks, you need to understand the essence of gas-shielded arc welding. Welding requires proper preparation. This procedure is always the same, regardless of the welding technology. First, the edges are given the correct geometry. This is determined by GOST 14771-76.

Mechanized gas-shielded arc welding is used to fully weld the alloy, which allows you to completely connect the edges of the workpiece. There is no gap between them. If there is a certain indentation, cutting edges, welding can be carried out for a workpiece whose thickness does not exceed 11 mm.

To increase productivity in the process of automatic welding, cutting of the edges of workpieces without slopes is carried out.

After welding in carbon dioxide, it will be necessary to clean the entire plane of the seam from dirt and slag. To make the pollution less significant, the surfaces are treated with special compounds. Most often these are aerosols that are sprayed onto metal. You don't need to wait for it to dry.

Standard parts such as wedges, tacks, staples, etc. are used during post-assembly. The design requires careful inspection before starting work.

Advantages and disadvantages

Manual and automatic gas shielded arc welding has both advantages and disadvantages.shortcomings.

The benefits of this method include:

• The quality of the seam is very high. Other welding methods cannot provide this.
• Most shielding gases are relatively inexpensive, so the welding process does not become much more expensive. Even cheap gases provide good protection.
• An experienced welder who has previously used other methods can easily master this technology, so even a large enterprise with a large number of employees can change the specifics of maneuvers.
• The process is universal, allows you to weld both thin and thick sheets of metal.
• Productivity is high, which has a positive effect on production results.
• The technique is used not only for welding ferrous, but also non-ferrous metals and alloys.
• The welding process when using a gas protective bath is easy to upgrade. It can be changed from manual to automatic.
• The welding process can be adapted to all the details of production.

Automatic and manual gas-shielded arc welding has certain disadvantages:

• If welding is performed in an open area, it is necessary to ensure good tightness of the chamber. Otherwise, protective gases may escape.
• If welding is carried out indoors, a high-quality ventilation system must be equipped here.
• Some types of gases are expensive (like argon). It raisesthe cost of production, increases the cost of the entire production process.

Varieties of gases

Arc welding in shielding gases is performed in different environments. They may be active or inactive. The latter include substances such as Ar, He and others. They do not dissolve in iron, do not react with it.

Inert gases are used for welding aluminum, titanium and other popular materials. TIG welding is used for steel that is difficult to melt.

Active gases are also used in the course of such work. But in this case, cheap varieties are often used, for example, nitrogen, hydrogen, oxygen. One of the most popular substances used in welding is carbon dioxide. For the price, this is the best option.

Features of the gases most often used during the welding process are as follows:

• Argon is non-flammable and non-explosive. It provides high-quality protection of the weld from adverse external influences.
• Helium is supplied in cylinders with increased resistance to pressure, which here reaches 150 atm. The gas is liquefied at a very low temperature, reaching -269ºС.
• Carbon dioxide is a non-toxic gas that is odorless and colorless. This substance is extracted from flue gases. Special equipment is used for this.
• Oxygen is a substance that promotes combustion. It is received ataid cooling from the atmosphere.
• Hydrogen becomes explosive on contact with air. When handling such a substance, it is important to comply with all safety requirements. The gas is colorless and odorless and aids ignition processes.

Features of welding in carbon dioxide, nitrogen

Arc welding in shielding gas with a consumable electrode is carried out using carbon dioxide. This is the cheapest technique, which is in great demand today. Under the influence of strong heating in the melting zone, CO₂ turns into CO and O. To protect the surface from an oxidative reaction, silicon and manganese are present in the wire.

This also leads to some inconvenience. Silicon and manganese react with each other, forming slag. It appears on the surface of the seam, requiring elimination. This is easy to do. This circumstance has no effect on the quality of the weld.

Before starting work, water is removed from the cylinder, for which it is turned over. This must be done at regular intervals. If this manipulation is not performed, the seam will become porous. Its strength properties will be low.

Gas shielded arc welding can be done with nitrogen gas. This technology is used for soldering copper blanks or stainless steel parts. With these alloys, nitrogen does not enter into a chemical reaction. During welding, graphite or carbon electrodes are used. If tungsten contacts are used for these purposes, this causes them to be overused.

It is important to set up the equipment correctly. It depends on thecomplexity of welding, type of material and other conditions. The most commonly used equipment with a voltage of 150-500 A. It creates an arc of 22-30 V, and the gas flow rate is 10 l / min.

Welding process

Gas shielded arc welding is an effective technique. But in order to achieve this, the master must fulfill all the requirements put forward by the standards for this process. This technique is somewhat different from other techniques, which the master must take into account.

First, the metal is prepared for the welding process. When using this technology, this procedure has less impact on the result, but it must be carried out. Next, the equipment is adjusted in accordance with the welding parameters. The thickness and type of material is taken into account.

When the equipment is ready, the arc is ignited. At the same time, the flame of the burner is set on fire. Some types of welding involve preheating the workpiece. To do this, first turn on the burner, with which the metal is pre-treated.

When a weld pool begins to form around the arc, start feeding the wire. For this, the equipment is equipped with a special feeder. It delivers the wire to the melt zone at a certain speed. If you need to make a long seam, this is convenient, since the arc does not have to be broken. For this, a non-fusible electrode is used, which maintains the arc for a long time.

If welding is done using direct current, its polarity must be reversed. This reduces the likelihoodspattering, but metal consumption increases. The deposition coefficient when using this technique is markedly reduced. With direct polarity, it increases 1.5 times.

It is advisable to lead the bath from left to right (if the master is right-handed). This will show the process of seam formation. Also, all actions must be performed towards you. The seam is created simply, the master only needs to drive the machine smoothly at a permanent speed.

The arc breaks away from the workpiece in the opposite direction of the welding motion. In some cases, after such manipulation, additional heating may be required.

Equipment

Arc welding in shielding gas is performed using special equipment. It adopts standard power supplies and also has a voltage adjustment function.

Welding units are equipped with a wire transfer device. There are also units for supplying gases to the melting zone using hoses from cylinders. The welding procedure is carried out at a constant high frequency of current. The stability of the arc depends on the correct adjustment. The wire feed speed is also adjustable. The most popular units for such welding are:

• "Impulse 3A". It is used for welding aluminum, but the disadvantage is the low functionality of the device. It can also be used for welding ferrous metals, as well as making ceiling seams.
• "PDG-502". Used for solderingcarbon dioxide. The device is reliable and efficient. Powered by both 220 V and 380 V. Electricity can be regulated from 100 A to 500 A.
• URS 62A. It is applied at welding in field conditions. Primarily used for welding aluminum, but can also process titanium.

Means of protection

Welding using gas is highly hazardous, especially when using explosives. Therefore, the welder must use personal protective equipment at work. They should cover the skin, eyes, and not allow the master to inhale harmful fumes.

Even if short-term welding is carried out in their own garage, the master must use a special mask, respirator and heat-resistant leggings. In this case, the work will be performed in safe mode, which also greatly affects the quality of the result.