What is welding

 

 What is welding?

Welding is the connection of metals by melting them. This process is widely used in many branches of mechanical engineering and construction. Its physical essence consists in creating bonds between atoms and molecules of two surfaces connected to each other. In order for them to have high strength, the following conditions must be observed:

 cleaning of work pieces from dirt;

energy activation of atoms;

placement of the welded parts at such a distance equal to the interatomic distance.

 The welded seam

Thanks to the development of technologies, portable welding machine can be carried out not only in industrial enterprises, but also in installation and field, and even in space. Various energy sources are used for processing, so this process requires extreme attention and compliance with work standards.

 Types of welding

To date, there are at least 10 types that are used in the case. The most popular types of welding have received, with the help of which not only metals are bonded, but also glass, ceramics and plastic. Currently, there are welds that differ from each other in the type of energy used to perform the work.

 Thermal welding

During thermal welding, parts are joined at the molecular level, using metal melted from the influence of an energy source. A solid monolithic seam is formed by liquid metal, which fills the gap between the parts.

 The advantages of this technology are the following:

 joint strength;

low metal consumption;

low cost price;

There are also disadvantages of this method:

 heat treatment can be carried out only on refractory metals;

the presence of an oxide film on the surface of the product significantly worsens the quality of the compound.

Electric arc contact welding

This universal type of welding is the most common method and is used both in production and in domestic conditions. When performing electric welding, the use of expensive equipment is not required, besides, even beginners can conduct it.

 Scheme of manual electric arc welding with a melting electrode.

The principle of operation of this method involves melting adjacent areas of the welded parts with the help of heat coming from an electric arc. The arc melts the electrode and the base metal, forming a welding bath. When the welding seam cools, the liquid metal solidifies, due to which a strong connection of the products occurs.

 MMA-manual arc welding

This type of processing is carried out exclusively with one electrode using an arc burning between the welding bath and the metal rod on which the coating is applied. As a result of the closure of the electrical circuit, thermal energy is generated and transferred to the elements, as a result of which the metal begins to melt. When the electricity supply stops, a welded joint is obtained.

ATTENTION: For manual welding, electrodes coated with a special coating are used, their composition depends on the purpose and ensures the correct formation during crystallization.

MMA is the simplest method of connection, for which it is enough to have a welding machine and suitable electrodes. They are produced of a certain type and have a limited length, so it is necessary to constantly interrupt the welding process to change this element. Like any kind of metal compound, MMA technology has its pros and cons.

 Advantages:

 the ability to connect almost all types of metals;

the cost of the equipment allows you to purchase a device for use in everyday life;

welding operations can be carried out in conditions of limited space;

atmospheric conditions are not an obstacle to the use of equipment (with the exception of precipitation).

Disadvantages:

 low productivity;

the coating evaporates quickly;

a complex technological process: the electrode often sticks.

Against the background of the advantages, the disadvantages are insignificant and are not a reason for refusing to use manual welding. This versatile equipment is affordable, and also unpretentious in operation.

 Argon TIG welding

Tig welding is a method of joining metals using a tungsten electrode with a protective gas. The rod does not melt during the process, in order to get a smooth seam, the welder needs to sharpen it before use. Among other welding methods, Tig technology allows you to obtain a high quality of the seam.

 TIG welding

To perform argon welding, the tungsten electrode must be fixed in the burner. Along the edges of the burner there are holes through which the protective gas-argon is supplied. By penetrating into the welding bath, argon protects it from the effects of other atmospheric gases. Due to this, a high-quality connection of metals occurs without an oxide film.

 Working on such equipment does not require special skills, to master the skill of creating beautiful seams, it is enough to work 2-3 times. The quality of the joint can be affected by wind and other unfavorable atmospheric conditions, therefore, when using the equipment outdoors, the connection point should be closed.

 MAG-semi-automatic welding

This type of connection involves the use of active gas and metal wire. During welding, an arc lights up between the electrode and the metal, as a result of which the product completely melts and a welding bath is formed. A gaseous substance protects it from the effects of oxygen. After a certain time, a weld appears due to the crystallization of the elements in the welding bath.

 Unlike other welding technologies, MAG has the following features:

 Fully automated welding process.

Changing the welding wires takes a minimum of time.

Welding is possible in any spatial position.

This method is used to connect different metals, so it is popular in many industries. The technology has found wide application in the production of marine vessels and automobiles.

 IMPORTANT: Semi-automatic welding requires a lot of professional skills and abilities from the welder, so only professionals can work with the device.

Submerged welding

SPF refers to the connection of metals using an electric arc, where the end of the electrode and the cast weld are hidden under a layer of granular fusible flux. This function protects against oxidation, increases the strength and forms a compound with a high degree of uniformity.

 Interesting: Features of control of welded joints

During welding, ultraviolet radiation is created and splashes and sparks are formed. Figure 2 shows how the SPF excludes such factors, since in the process the molten metal is covered with a thick layer of flux. There are 3 main ways:

 Manual. For the manual method, a small equipment with a non-melting electrode is used. The welding current and the flux supply are regulated by the welder in manual mode.

On a semi-automatic welding machine, almost all functions are adjusted automatically, only arcing is carried out manually using a handle or remote control.

The automatic method involves the participation of workers only as controllers, all other functions are performed by the control processor.

Gas-flame

This type implies the use of an open burner flame for melting and joining two metals. Mixtures of gases from oxygen and acetylene are used for heating, other options are also possible. Upon contact with the flame, a structural change of the metal occurs and the formation of a liquid welding bath. Fluxes are used to protect the metal from atmospheric exposure. As the flame exposure decreases, the temperature decreases and the crystallization process occurs, which contributes to the formation of a weld.

 Electroslag

ESS is one of the welding methods in which heat is generated in the molten slag environment. The metal is heated in the mass, passing an electric current that generates heat in the slag. With ESS, the use of an arc is not required, vertical welding allows you to weld a thick layer of the alloy in one pass.

 This method is used to connect thick-walled elements made of various steel alloys from cast iron to high-alloy.

 Plasma

Plasma welding is based on the principle of using a narrowly directed plasma jet for melting alloys. This type of technology is suitable for connecting products made of different materials: stainless steel, non-ferrous metals. In plasma welding, argon-arc technology is used, unlike electric, it has the form of a compressed plasma jet and has powerful energy.

 The plasma is based on neutral molecules and atoms, as well as electrons and ions. During welding, a very high temperature is formed up to 300 thousand °C and pressure on the surface of the metals being welded, and the arc acquires a cylindrical shape, maintaining power indicators along the entire length. This method is suitable for use in hard-to-reach places, since a slight change in the distance between the part and the electrode does not affect the quality of the seam.

Thermomechanical welding class

The thermomechanical class includes compounds obtained by using the combined action of heat and pressure introduced into the welding zone from the outside. During thermomechanical welding, the end of the electrode and the part of the part to be connected are melted. A strong welding seam is obtained after the metal cools down.

 Interesting: Features of measuring control of welded joints

Classification of welding methods

In the modern world, there are many welding methods, each of which finds its own application. Types and classification of welding types are carried out according to different criteria and are divided into 2 main groups:

 Fusion welding.

Pressure welding.

To melt the connected parts, a heat source with a very high temperature is used, after which they are merged into a common welding bath. When the heat source is removed, the welding bath cools and hardens, firmly connecting the 2 parts.

 In the second group, the dominant role is played by the pressure applied to the welding site, heating of the metal plays a secondary role, in some cases, the connection can be carried out without the use of heating.

 Pressure welding, in turn, is divided into 2 subgroups:

 Cold, the metal does not heat up in the connection zone, this process involves welding at room temperature.

Pressure welding without melting. In this case, the metal is heated to a certain temperature, at which its mechanical strength and elastic properties decrease. Heating of the elements greatly facilitates the welding process, sometimes it is practically necessary. This method does not require the use of high temperatures, so different heat sources can be used for heating.

Welding methods and technologies

In addition to the above traditional methods, there are other methods that allow you to combine unique metals. They have pronounced properties, because of which the usual methods are not suitable for their connection.

 One of these methods is laser welding, which is performed using semi-automatic or automatic equipment. This method involves the supply of heat strictly at one point to connect very small parts.

 ATTENTION: To weld several parts at once, it is recommended to use a prism with which you can split the laser and point it in different directions.

 Brief description of welding

Regardless of the type of welding and the classification of methods, welding is the technology of creating strong joints by heating, applying pressure, deforming or combining all methods. The essence of this process is the influence of an external energy source to establish interatomic bonds between parts. During the cooling process, crystallization occurs and a welding seam is formed. The connection options are selected taking into account the material, area and chemical properties of the products being welded.

Welding principle

The principle of metal welding is determined by the technological characteristics set for each type separately, since the specifics of their work differ. To obtain a strong welded joint, it is necessary to bring the surfaces of the two metals closer together under high pressure, so that an electron cloud subsequently appears, interacting with the ionized atoms of both metal surfaces.

Heating at the junction leads to the amplitude of the vibration of the atoms relative to the constant points, which in turn creates an easier connection between the products. The pressure strength depends on the heating temperature indicators.