Today the following types of electric arc welding are known:

At home, these types of welding are practically not used. Therefore, let’s move on to consider the fourth type of welding work - manual electric arc welding.

Manual arc welding is based on the use of a special electrode in a coating

Electric welding machines for manual welding are divided into two types - alternating current and direct current. The use of alternating current allows the design of devices with high performance and power. The advantage of direct current, due to the lack of polarity reversal, is a smoother weld with less metal spatter.

In 1802 V.V. Petrov discovered the phenomenon of galvanic voltaic arc.

A device for welding metals using “electrohephaestus” was patented in 1882 by N.N. Benardos.

Russian engineer N.G. Slavyanov first used an electrode for welding in 1888.

In 1932, Soviet physicist K.K. Khrenov. Successful welding of metals under water was carried out.

Subsea pipeline repair

The operation of the welding machine is based on the creation of an electric arc at the point of contact of two metal parts. High temperature (up to 7000 o C) melts the material to a liquid state and diffusion occurs - mixing at the molecular level.

The fundamental difference between welding and gluing is the absence of auxiliary materials - the parts being joined are transformed into a monolithic structure.

Therefore, it is necessary to clearly understand that for the correct application of welding, only homogeneous metals can be used. You cannot weld aluminum to iron or copper to stainless steel. The melting point of different materials is different, and the creation of alloys is not within the capabilities of welding equipment.

There are various welding machines for welding iron structures.

The main advantage of inverter welding is the improvement of the dynamics of the electric arc, as well as a noticeable reduction in the weight and dimensions of the installation (compared to direct transformers). In addition, it became possible to smoothly regulate the output current, which significantly increased the efficiency of the unit and ensured ease of ignition of the arc during operation.

But there are also disadvantages:

• temporary limitations in use due to heating of the electronic conversion circuit;
• creation of electromagnetic “noise”, high-frequency interference;
• negative influence of air humidity, which leads to the formation of condensation inside the device.

What is needed for work

Before you start welding, you need a welding machine and equipment:

The place where welding work is carried out is cleared of flammable materials and equipped with fire extinguishing means - water, sand, technical soda. If this is an enclosed space, it is necessary to arrange supply and exhaust ventilation.

Necessary fire-fighting equipment at any site

How to cook by welding

To successfully master the technique of permanently joining metal parts, you need to master 4 basic skills, without which not a single “welding session” is complete.

Setting up the device

The basis for setting up a welding machine is the correct selection of current and voltage output to the terminals. Despite the simplicity of the formulation, the topic of customization deserves a separate discussion. But if we briefly formulate the setting criteria, we can distinguish 5 main parameters:

In order to accurately select the current value, the easiest way is to use ready-made tables.

But due to the fact that each device has its own design features and technological nuances, the final word still remains with the “scientific poking method” - the empirical selection of the required current experimentally.

Setting the welding current depending on the electrode diameter

Table of relationship between electrode and welding current

Current selection mode for welding standard butt joints:

A one-sided seam connects the surface of parts on one side, a double-sided seam connects the surface of parts on two opposite sides.

Examples of welding parts using various seams

You can also use a universal table for a wide range:

A simple rule is easy for a novice welder to remember. If the current exceeds the required value, the electrode will burn through the workpiece. If the current is lower than necessary, the part is not welded, the deposited metal falls off when exposed to mechanical means.

Electrode connection

The electrode can be connected to the positive or negative current output. If “+” is connected to the part, then the polarity is called straight. If “-” - reverse. Accordingly, with direct polarity there is a “minus” on the electrode, and with reverse polarity there is a “plus”. The difference between these positions is that more heat is always generated at the “positive” terminal. Experienced welders use this phenomenon to solve specific problems. For example, by manipulating the polarity, you can cook thin sheet stainless steel that is sensitive to overheating. To do this, “plus” is applied to the electrode, and “minus” is applied to a sheet of thin metal.

One of the electrode connection options

Video: direct and reverse polarity when operating an inverter welding machine

Creating an Arc

The welding process begins with the ignition of an electric arc. In all types of manual welding, the arc is created by briefly touching the electrode to the part. In this case, the end of the electrode is sharply heated to a temperature sufficient to establish an arc discharge.

The process of igniting an electrode arc requires certain skills

After a short circuit, if the arc ignites, it is necessary to maintain a distance between the end of the electrode and the part of 3–5 mm. In this case, it is necessary to take into account the fact that the length of the electrode decreases as welding progresses. When exceeding a distance of 5 mm. the arc is interrupted when the decrease is less than 3 mm. the electrode may stick to the workpiece or cause large splashes of molten metal.

Electrode movement

To create a good seam, various arc patterns have been developed along the welded area. In this case, it is considered important not only to melt the edges of the parts being welded, but also to fill the weld pool with the required amount of metal deposited from the electrode.

Various options for the trajectory of the electrode end

This can be achieved by maintaining a constant length of the electric arc and systematically moving the end of the electrode along a certain trajectory.

When producing a seam without transverse movements, the width of the joint is usually equal to b = (0.8–1.5)xd el. Where b is the width of the welded joint, and d is the diameter of the weld

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Today there are many different ways of joining metal products. They can be divided into two groups:

1. Detachable.
2. One-piece.

Classification of welding seams.

The connections of the first group include parts that can be separated without disturbing the connecting elements, for example, a bolt with a nut. It is the second connection that is the most reliable. In this case, the parts cannot be separated without breaking the connecting part. We are talking about welding and riveting joints. When it is necessary to obtain a high-quality and reliable connection, a welding seam is considered the best. Many people buy welding machines to weld parts, but have absolutely no experience. After several unsuccessful attempts, the question arises: how to properly lay a welding seam? To do this you need to know a few basic rules.

Main characteristics

The welding process is the joining of metal using electric arc welding. The connected parts are melted using an electric arc, as well as an electrode consisting of a metal rod with a special coating. The quality and reliability of the weld is influenced by many different factors:

Covered metal electrode welding diagram.

• welding machine;
• current adjustment;
• electrode size;
• welder's professionalism.

Types of welding that are used in everyday life and industry are divided into several groups:

• gas press;
• contact;
• roller;
• electroslag;
• termite;
• friction welding.

When gas press welding is used, an open flame of oxygen acetyl is used. The positive side of this method is considered to be high productivity. This method has become widespread in the gas and oil industries. It often occurs when pipelines are laid. This method is also widely used in mechanical engineering.

Resistance welding occurs at low voltage but high electric current. This method can be used for spot and butt welding.

Semi-automatic welding circuit diagram.

To master the technological process of welding work, you first need to have the appropriate welding equipment. You can rent it or buy it. Today, stores offer a wide range of welding machines that have a device that makes it possible to adjust the current strength. A home craftsman can make a welding machine himself, but he cannot do without an electrical energy converter. These devices come in several varieties.

Some types of devices for high-quality work

Transformer. Designed to produce direct current when you have to use a household outlet. When purchasing such a unit, you must always remember that inexpensive models are not able to maintain stable operation of the electric arc. Voltage leakage occurs very often. The negative side is also their mass; they are heavy and clumsy.

Rectifier. This is a device that converts household current into direct current. The device differs from a transformer in the stable operation of the electric arc. The quality of the weld is quite high.

Inverter. The latest converter that allows you to work on any type of current. Always produces high quality welding. The seams are even and smooth. The device is very compact, light weight, and easy to light. The inverter is characterized by high performance and speed.

For normal operation of electric welding there must be a stable arc. This consistency depends on the correct choice of the gap between the part being welded and the electrode coating. The arc burns best when the gap is 5 mm.

Technique for making welds.

The high temperature of the arc causes the part and the metal rod of the electrode to melt. At this time, all the depressions that were formed as a result of melting are filled. When the electrode moves slowly along the surface of the seam, voids are filled.

In order to be proud of the resulting seam, you need to choose the right electrode. To do this, you need to know the metal composition of the part that will need to be welded. The selection of an electrode is based precisely on these parameters. Electrodes are manufactured in several types. They can be:

• steel;
• copper;
• cast iron;
• bimetallic;
• brass.

By marking the electrode, you can determine the viscosity of the resulting weld; the numbers will tell you about the hardness of the metal. The main rule when choosing an electrode is its size. It must match the thickness of the metal.

For high-quality electric welding, so that the seam looks neat and durable, it is necessary to select the correct inclination of the electrode. Typically this angle is 75 degrees relative to the direction of the electric arc. In order for an arc to appear, you need to strike the surface of the metal and, when a flash appears, quickly lift the electrode. When the arc appears, it must be slowly drawn along the seam. An arc will also occur when the electrode is tapped on the surface.

To obtain a stable arc, the current must be adjusted correctly. If it is insufficient, the arc will go out very quickly, and the electrode will “stick”. When the current strength is high, the metal splashes in all directions and it begins to burn.

During operation, the electrode melts and gradually decreases in size. In this regard, you need to constantly move it towards the part, maintaining the required distance for a stable arc. If this is not done, the arc will quickly go out.

During the welding process, a weld pool is formed, which is a liquid mixture of molten metal and a melting coated metal core. When there is a constant smooth movement of the electrode with a maintained gap, the quality of the seam will be the most reliable, and the mechanical performance will be at its best. The seams will look aesthetically pleasing.

After welding, slag is formed over the entire surface of the seam.

It is removed with small blows of a hammer. Then the seam is cleaned with a wire brush. To learn how to weld metal well, you need constant training and a desire to get excellent quality work. Before you start working on your own, it’s worth watching how experienced welders work.

Of course, welding is a very complex and difficult job. It is almost impossible to instantly master all the nuances of this matter. It will take a lot of time to master all the tricks of welding. Once you have experience and skills, you will be able to produce original and beautiful products using welding.

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Welding ceiling seams. Sequence of work.

Ceiling welding is considered one of the most difficult types of welding because the weld pool is located upside down. Welding ceiling seams requires a precise sequence of all actions. If you do not follow the rules and recommendations, you can get a poor-quality connection, which can lead to leaks of hot metal.

When making a ceiling seam, you need to follow safety precautions and protect your face and hands from possible contact with hot drops of metal.

Features of the ceiling seam technique

Note! Preparatory work before welding ceiling seams is accompanied by a number of difficulties. This is due to the fact that during the welding process, molten metal can flow down and accidentally fall on the skin of the person performing the weld. That is why experienced specialists, knowing how to weld such a seam, use special welding techniques that ensure strict compliance with safety rules.

Before connecting ceiling seams, you must clearly understand all the requirements and not neglect to fulfill the mandatory conditions. This information is especially important for novice welders.

If your workpieces are more than one centimeter thick and you do not know how to weld a ceiling seam, then know that in such a situation welding must be done in stages. At the very beginning of work, you need to use an electrode whose diameter does not exceed 3 mm; at all other stages, an electrode with a diameter of 4 mm is used.

Note! Welding a ceiling seam involves creating not only horizontal seams, but also connections along a certain slope (from 10 to 80°C). In this case, both manual welding and semi-automatic welding can be used. You can also use arc welding using coated electrodes.

As already noted, the main distinctive feature of such welding is based on an inverted weld pool and holding the hot metal by tension force. It is very important to maintain the minimum size of the bath and sometimes move the electrode to the side so that the metal has time to cool and set. In addition, this welding method will protect your connection from cracks.

Welding methods

• Crescent, this method involves placing the electrode at an angle of 90-140° to the surface. Using oscillatory movements in an arc, it moves from edge to edge.
• Ladder, here the electrode is placed in exactly the same way. It is taken away from the hot metal and returned back.
• Back-and-forth method. In this case, the electrode must be constantly returned to the frozen seam.

The first method is considered the simplest and is well suited for inexperienced welders. Options involving ladder and back-and-forth welding are more complex and time-consuming. But such a connection will be of better quality.

Stages of work execution

Initially, the places that will be welded must be well treated by cleaning the edges with a grinder or a metal brush. Then the root of the seam is welded with an electrode (3 mm). Through it, a roller of molten metal is formed. If it is necessary for the roller to be on the reverse side, then the electrode is directed into the gap in small short throws. Monitor and control the uniform arc burning. The resulting roller must be freed from slag. If its shape is too convex, then it is necessary to bring it to pure metal. As already mentioned, in the following stages an electrode with a large diameter (4 mm) is used.

In order to obtain a reliable and durable seam, all safety regulations must be followed. Not only the quality of the seam, but also your personal safety depends on compliance with the rules.

• Be sure to insulate all wires, and when you pause work, completely turn off the welding machine. This way you will protect yourself from electric shock during the welding process.
• It is recommended to weld ceiling seams in a warm, dry room.
• Under no circumstances should you work in rainy or snowy weather. Only specialists with extensive experience should carry out welding in wet areas, but even then you should be extremely careful.
• Wear special protective clothing, a mask and goggles. The entire body should be tightly covered with clothing.

In conclusion, it is worth noting once again that welding ceiling seams is a rather labor-intensive and energy-consuming process. It is quite difficult for a novice welder to make this type of connection. In order to do the job efficiently and create a good, strong seam, you need to gain special knowledge, master the technique of working with a welding machine and become familiar with all the nuances of this type of work. It’s better to practice welding some parts first. If you do not have enough knowledge and experience, then it is better to entrust this process to specially trained people. In any case, both experienced welders and beginners must strictly follow safety rules. Accurate compliance with all requirements and instructions is the key to your personal safety.

How to weld properly. How to place a welding seam correctly

One of the most inconvenient and difficult positions for welding is the ceiling. But it is worth mastering this type of connection due to the automatic increase, which has learned to apply high-quality sutures in such a spatial position. This is in demand at enterprises whose activities are related to laying, and at construction sites. This skill is also useful in everyday life, when welding heating or gazebos. Some elements of a metal garage cannot be assembled without welding joints at the top. How to weld a ceiling seam using electric welding? What are the main precautions and optimal device settings?

Many welders do not like ceiling seams because of the difficulties in their execution. A beginner’s results can often be poor, which discourages them from learning. But if you understand the main problems and prevent them as much as possible, then pretty soon, after training, you can master this difficult connection.

Welding a ceiling seam with an inverter or transformer is significantly different from working on a similar product in the lower position. When metal is welded on the floor, the weld pool spreads over the joint, and the welder only needs to ensure that the joint is properly filled, preventing slag from getting in front of the pool. When the ceiling serves as the working surface, the molten metal tends downward under its own weight.

The slag, being in a liquid state, also constantly drips, which interferes with the welding. These splashes hitting the ground scatter even more, hitting the welder and surrounding objects. The main difficulty when arc welding in the ceiling position of the seam is connecting the sides of the product. A weld pool forms on one edge, but there is no way to bond both sides with metal.

Welding of ceiling seams is performed at a reduced current, which leads to frequent sticking of the electrode and lack of penetration. One more. The body position with the head thrown back and the arm raised up quickly tires the welder. Therefore, frequent breaks are simply necessary for quality work. Understanding these complexities will help you tune in to the challenges and take steps to make the process easier to implement.

Ceiling welding technology

To understand how to properly perform this type of connection, you need to know the basic rules used by experienced welders. Additionally, you can see how to weld a ceiling seam using electric welding in the video. Here are the main points:

• The sides to be welded should be brought together as much as possible. Welding with gaps on the ceiling is only available to experienced specialists, so the more closely the parts are connected, the easier it will be to apply a seam.
• Edge cutting is carried out as in the lower position. When the thickness of the sides is more than 5 mm, a V-shaped bevel is made.
• The electrode is brought to the ceiling at an angle of 45 degrees relative to the upper plane. Beginner welders can try welding with half of the electrode, as this will allow better control of its tip and control the formation of the seam.
• The welding process and the seam itself in this spatial position are possible due to the surface tension of the metal. To prevent drops of molten iron from flying off before they catch on the edge, the current should be reduced.
• If the sides are brought close together, then the first seam on even plates can be made without oscillatory movements. This will fill the joint well. The second pass is made wider to strengthen the ligament. But on pipes it is better to immediately weld with a wide seam.
• Electrode welding can be performed in several ways: crescent, horizontal figure eight, or spiral. When there is a small gap, an intermittent arc is used to allow the deposited drop of metal to cool. After a moment, without allowing the red color to pass through (this can be seen through the mask), the next drop is applied. This is a long process, so the welder does not need to rush and needs to rest periodically.
• Do not be intimidated by the appearance of the connection after the work is completed. Slag can flow down several tiers. But after beating it off, a high seam should remain. Sagging and large rollers are not critical.

Devices and electrodes

Ceiling seams can be made using an inverter or a conventional transformer. It is important to correctly set the current strength, which is 25% lower than when welding on the floor. For example, for plates 5 mm thick, 100A is sufficient. It will be easier to work if the cable is not heavy. This will make it easier to control the end of the electrode and your hand will get less tired. You can also loop the cable around your hand to reduce the strain on your wrist.

Electrodes for ceiling welding are suitable with a diameter of 3 and 4 mm. It is important to use them to reduce the amount of splashing. If beginners use short electrodes, this will allow them to manipulate the arc more confidently.

Precautionary measures

For ceiling seams, you should wear a thick jacket and trousers. Gloves must cover the cuffs, otherwise scale will reach the elbows and burn the skin. A hat or cap without a visor is required on the head. It is important to choose trousers of such length that they cover the collar of the shoe to prevent molten particles from getting inside.

Since the spray hits the ground and spreads further, there should be no flammable objects nearby. You need to use safety glasses to beat off the slag, because it will fall down on the welder. Frequent rest will allow you to relieve stress from the muscles of your neck and arms and get the job done efficiently.

Welding in the ceiling position is not mastered immediately. It takes practice and patience. It’s good to take a few minutes a day and weld two pieces of pipe or corner to the table and try to weld them from below. Having mastered this method, you can safely weld pipes and metal structures of any complexity.

› How to weld using electric welding: weld metal pipes and make beautiful seams.

A weld is one of the most reliable ways to connect parts. It is used in industry and in normal daily life. Every home craftsman uses welding from time to time. It’s good if he knows how to cook himself, but he often has to turn to specialists. But welding is quite possible to learn. You should start with the simplest: electric welding for beginners is, first of all, learning how to make various seams. More complex work can be performed only after gaining experience. Let's look at the basics of technology and some of the tricks of the welding process. Where to start - the preparatory stage FIRST All you need to do is prepare the equipment. You will definitely need a welding machine, a set of electrodes, a hammer for knocking down slag and a brush. The diameter of the electrode is selected depending on the thickness of the metal sheet. Don't forget about protection. We prepare a welding mask with a special light filter, thick clothes with long sleeves and gloves, preferably suede. You will also need a welding rectifier, transformer or inverter - devices that convert alternating current into the direct current necessary for welding. Before work, it is necessary to prepare protective equipment, which includes a special mask with a light filter, suede gloves and long sleeves, as well as Necessary tools Welding process technology Welding is a high-temperature process. To carry it out, an electric arc is formed and held from the electrode to the workpiece being welded. Under its influence, the base material and the metal rod of the electrode melt. As experts say, a welding hole is formed

Electric arc welding is a method of joining metal parts in which the parts to be joined are melted by an arc discharge in the area of ​​their contact, followed by solidification and the formation of a permanent joint. The heat source for arc welding is a welding arc - a stable electrical discharge in an ionized mixture of vapors of materials and gases, characterized by a high current density and high (4500-6000 ° C) temperature, exceeding the melting point of all known metals.

Welding arc structure

To create an electric discharge, a constant or alternating voltage is supplied to the metal being welded and the welding electrode from a current source (welding machine). As a result, a welding arc occurs between the electrode rod and the metal. Its resistance exceeds the resistance of the electrode and wires, so the main part of the thermal energy is released in the arc.

To form an arc and maintain its combustion, there must be positively and negatively charged particles - electrons and ions - in the space between the electrode and the metal being welded. The process of their formation, called ionization, occurs during ignition of the arc and is continuously maintained during its burning.

The figure below shows a diagram of the welding arc and the process of seam formation. Under the influence of the high temperature of the arc (1), the electrode (2), its coating (6) and the welded metal (3) melt. At the melt site, a weld pool (4) is formed, into which drops of the molten electrode (5) are transferred. The molten coating (6) forms a gas cloud (7) and a slag bath (8), protecting the metal from exposure to oxygen and nitrogen. As the electrode moves, the metal cools and crystallizes, forming a weld seam (9) with a slag crust (10) on the surface.

Required electric welding components

To be able to weld metal using electric welding, you must have:

• current source (welding machine);
• welding materials (for example electrodes) corresponding to the metal being welded;
• protective clothing (mainly a protective mask);
• hammer and wire brush to remove slag.

Before you start working with a welding machine, it is necessary to clean the metal being welded from foreign substances and contaminants - oil, paint, rust, scale, etc. Their presence on the metal leads to disruption of the uniformity of the seam and the formation of pores. Cleaning is done with any suitable tools and materials - a wire brush, a hammer, a rag with a solvent (for example, gasoline). Difficult-to-remove contaminants can be treated with a gas burner flame (blowtorch), followed by cleaning with a brush.

Types of welded joints

In welding, different types of weld joints are used. There are quite a lot of them; the butt ones alone distinguish 32 species. However, there are only four main ones: butt (1), corner (2), T-joint (3), overlap (4). With corner and T-joints, the edges can be connected at any angle to each other.

When the metal thickness is more than 3 mm, it is recommended to cut the edges, which allows you to make a seam running through the entire thickness of the metal. Cutting makes it possible to weld in several seams (layers) of small cross-section, this reduces stress and deformation and improves the structure of the welded joint.

The cutting angle can be different - from 25 to 50°, depending on the thickness of the metal, the type of connection and the requirement for weld strength. At home, when working with small parts, cutting is easiest done on a sharpening machine. When working with large parts, you can use a gas cutter. If the cutting cannot be done for any reason, the welding current is increased to weld the metal through the entire thickness.

Assembling the structure before welding

A feature of the welded joint is severe deformation of the structure. As it cools, the weld metal “pulls” the product, breaking its shape. If proper measures are not taken, the shape of the welded structure will be very different from what was planned. Right angles will turn into acute or obtuse, and the flatness of surfaces will be disrupted.

Deformation is combated using rigid assembly and clamps. The connected parts are fixed in a certain position using clamps, clips, ties and other devices. But even a fixed product can fail if “tacks” are not made in the required places - short seams of small cross-section in different places of the structure. The latter must be positioned in such a way that the stresses of the seams are mutually compensated. In butt joints, for example, clamps are made from different sides of the part.

Connection polarity

Working with a DC welding machine provides an additional opportunity to control the welding mode by swapping the connection of the holder cable (electrode) and the ground clamp (material). In normal mode, the electrode is connected to the minus terminal, and the material is connected to the plus terminal. This connection is called “direct polarity” and provides better heating of the material being welded, which is precisely what is necessary in most cases due to the massiveness of the latter.

The physical nature of stronger heating of the metal with “straight” polarity is that the flow of electrons, representing an electric current, moves from “minus” to “plus”, from the cathode to the anode (in this case, to the metal being welded), transmitting it its energy of movement and heating in addition to heating from the electric arc.

Sometimes it becomes necessary to reduce the heating of the metal - when welding thin-walled materials (to avoid burn-through) or alloy steels (to prevent burnout of alloying elements). In this case, reverse polarity is used, connecting the electrode to “+” and the material being welded to “-”. In this case, the flow of electrons changes its direction and no longer heats the metal, but the electrode.

The designation of some electrodes contains an indication of the polarity of the connection, which must be observed. But, in essence, any electrode can work at different polarities, except that the quality of welding will vary. If the “native” polarity of the electrode is unknown, you need to work with it, changing it, ultimately choosing the one that provides the best welding quality.

Technology of steel welding with coated electrodes

The question - how to learn to cook with electric welding - has only one answer - practice. You cannot become a welding master by studying theory alone. And yet, before starting practical work, it is useful to become familiar with the theoretical foundations.

Arson arc. An arc can occur either in the event of a breakdown of gas (air), or as a result of contact of electrodes with their subsequent removal to a distance of several millimeters. The first method (air breakdown) is only possible at high voltages, for example, at a voltage of 1000V and a gap between the electrodes of 1 mm. This method of arc initiation is usually not used due to the danger of high voltage. When feeding the arc with high voltage current (more than 3000V) and high frequency (150-250 kHz), you can get an air breakdown with a gap between the electrode and the workpiece of up to 10 mm. This method of igniting the arc is less dangerous for the welder and is often used.

The second method of igniting the arc requires a potential difference between the electrode and the product of 40-60V, therefore it is used most often. When the electrode comes into contact with the workpiece, a closed welding circuit is created. At the moment when the electrode is removed from the product, the electrons, which are located on the cathode spot heated by the short circuit, are separated from the atoms and move to the anode by electrostatic attraction, forming an electric arc. The arc stabilizes quickly (within a microsecond). The electrons that leave the cathode spot ionize the gas gap and a current appears in it.

The arc ignition speed depends on the characteristics of the power source, the current strength at the moment of contact of the electrode with the product, the time of their contact, and the composition of the gas gap. The speed of arc initiation is influenced, first of all, by the magnitude of the welding current. The greater the current value (at the same electrode diameter), the larger the cross-sectional area of ​​the cathode spot becomes and the greater the current will be at the beginning of arc ignition. A large electron current will cause rapid ionization and transition to a stable arc discharge.

As the electrode diameter decreases (i.e., as the current density increases), the transition time to a stable arc discharge is further reduced.

The arc ignition speed is also affected by the polarity and type of current. With direct current and reverse polarity (i.e., the plus of the current source is connected to the electrode), the arc initiation speed is higher than with alternating current. For alternating current, the ignition voltage must be at least 50-55V, for direct current - at least 30-35V.

Re-ignition of the welding arc after its extinction due to short circuits by drops of electrode metal will occur spontaneously if the temperature of the electrode end is high enough.

The most convenient way to ignite an arc is to strike the tip of the electrode against the metal. With this movement, an arc occurs and the coating begins to melt. In this case, the electrode does not stick. In order not to leave marks on clean metal, you need to strike along the line of the future seam, moving the electrode to its beginning.

If there is a bead on the tip, it needs to be beaten by tapping the electrode on the metal - preferably on the one to which the “ground” is not connected, otherwise the electrode may stick. If the electrode tip is excessively exposed, it may need to be struck several times to melt the exposed metal to avoid sticking.

Selecting the electrode diameter and welding current. The diameter of the electrode and the current strength are selected, first of all, taking into account the thickness of the metal being welded. For the initial selection of electrode diameter and current strength, you can use the following table, the values ​​\u200b\u200bof which correspond to the bottom seam.

The strength of the welding current is also indicated in the characteristics of the electrode on its packaging.

When making welds in vertical and overhead positions, electrodes with a diameter of no more than 4 mm are used. If there is a cutting of the edges or it is necessary to fill the gap between the parts, then the root weld can be made with an electrode of a smaller diameter - 2.5-3 mm.

The approximate value of direct welding current can be calculated using the formula I= K d, where I- current strength, TO- coefficient, d- diameter of the electrode. Coefficient TO selected depending on the diameter of the electrode.

This calculation allows you to determine the current value for the bottom seam when welding with direct current. If these conditions change, the formula should be amended:

• If a vertical seam will be welded, an adjustment factor of 0.9 must be entered into the formula. As a result, the formula will take the form I = 0.9 K d.
• When making a ceiling seam, the value of the correction factor must be reduced to 0.8 (I = 0.8 K d). This will result in a smaller volume of molten metal and faster crystallization.
• When welding on alternating current, the value of the welding current should be increased by 10-15A.

The optimal current value must be selected during operation depending on specific conditions.

If a welding transformer or rectifier is used as a current source, the actual current strength may differ from that set on the machine when the supply voltage changes. If it is low (in the evening, for example), the actual welding current will be lower than the value indicated by the switch.

When welding a vertical seam from top to bottom, the current strength is set to 5-10A more than when welding from bottom to top.

Affects the required current and the type of welded joint (connection diagram). Butt welding requires less current than lap welding. T-joints, which require more heat when welding, require a 10-15% increase in amperage compared to butt welding.

The thermal conductivity of the steel being welded also affects the required current value. The higher it is, the more intensely the metal is cooled in the area of ​​the arc, the higher the current must be to ensure good penetration. Therefore, when welding chrome-molybdenum and chrome-silver steels, the current should be 10% and 20%, respectively, less than for low-carbon steel, since the latter has greater thermal conductivity.

When welding metal products of different thicknesses, the current must correspond to the lower limit for the larger thickness.

Working with a welding machine at low and high current. If the current is low, the base metal does not heat up strongly enough, the pool is static, does not want to spread, forms curls at the weld boundary, heavy slag floods the arc, and the electrode sticks. If for some reason the current cannot be increased, you need to actively move the electrode from side to side, preventing the slag from filling the arc.

If the current is high, the base metal heats up strongly, the slag becomes too liquid, and the bath becomes excessively mobile, making it difficult to control such a bath. Metal may splash over the edges of the joint, causing spatter. The electrode will also melt too quickly, creating additional inconvenience. In this case, it is necessary to reduce the current or increase the speed of the electrode, thereby reducing the temperature of the base metal.

It is more difficult to control the bath at high current than at normal current. However, with the acquisition of experience, when working with a welding machine becomes familiar and easy, you can increase the welding current, simultaneously accelerating the speed of movement of the electrode. This will improve productivity. In addition, high current increases metal penetration and provides a smoother weld.

The electrode must be held at an angle of 90-45 degrees to the horizontal (towards the seam). The most convenient angle is 75 degrees. Its optimal value depends on what kind of seam is intended to be formed.

The more vertical the electrode is held, the deeper the metal is melted, and the less convex the seam becomes. This is caused by the arc putting pressure on the metal bath, causing it to spread. An inclined electrode by the force of the arc causes the seam to rise and become more convex.

Too much of an inclination results in little penetration, a very convex seam and improper fusion of the coating. By controlling the angle of inclination, you can form seams of different convexity and penetration depth.

Bath formation. After igniting the arc, you need to heat the metal and form a bath. To do this, make 2-3 small turns around the starting point of the seam. In addition to heating the metal and forming a bath, at this time a protective gas atmosphere is formed, which is necessary to prevent pores from appearing in the seam.

Control of the gap between the electrode and the metal. Perhaps the most important thing in welding technology is controlling the gap between the electrode and the metal. The task is complicated by the fact that the electrode is shortened during operation, and it must be constantly lowered to keep the gap constant. It is necessary to master this art. Maintaining the correct gap will help form a high-quality, durable seam.

If the gap is small, the base metal does not heat up well and the weld turns out to be convex with lack of fusion at the edges. If the gap is large, the arc begins to “jump,” which leads to poor penetration and a shapeless, weak seam. A normal gap ensures good penetration, an even seam, and fusion of its edges with the metal. The arc length should be moderately short - no more than the thickness of the coated electrode, usually about 3 mm.

The influence of arc length on the quality of the weld: short, long and normal arc.

Seam formation. To correctly form a seam, when guiding the electrode, simultaneously with the forward movement, it is necessary to make circular or zigzag movements relative to the seam line.

The speed of movement of the electrode (welding speed) must be such that there is enough molten metal to form a seam. If it is not enough, undercuts will remain - a groove along the edge of the seam (see Welding defects).

If the electrode moves too quickly, the arc does not have time to heat the metal, and the seam lies on top without melting the base metal. If the electrode moves too slowly, the base material overheats, creating excess molten metal and causing the pool to spread.

The current strength is closely related to the speed of the electrode. High current increases penetration and allows the electrode to be driven at a higher speed. The higher the current, the higher the speed the electrode should be driven and vice versa. When the speed of movement matches the current strength, the edges of the seam are thin, well fused with the base metal, and the seam itself is strong and beautiful.

Vertical seam. Based on their location in space, there are lower, ceiling, horizontal and vertical seams. The first two are located in horizontal planes, the latter - in vertical planes.

A vertical seam can be welded in two ways - moving from top to bottom or from bottom to top. The heat of the arc moves upward from the welding site, so to ensure good penetration when welding from top to bottom, you need to set the current a little more (5-10A) than when welding from bottom to top.

By changing the angle of the electrode, you can keep the bath from falling down, pushing it up with the force of the arc. If it still falls, you need to increase the speed of movement, increasing the current a little, and move the electrode from side to side, expanding the seam.

Otherwise, the vertical seam is made according to the same rules as the lower one - welding is carried out with a short arc in a zigzag or circular motion. The speed of movement is selected according to the current strength.

Horizontal seam. Welding technology allows for a horizontal seam to be made both from left to right and from right to left. The first method (from left to right) is more convenient for right-handers. The electrode is held perpendicular to the seam or slightly inclined. An excessively large slope will push the bath out of its place. If the molten metal goes down, you need to move faster, reducing the heating of the base metal, or make an “overlap” - moving the electrode up and down. If welding experience is not enough, it is better to make the seam thinner, if necessary, widening it with a second pass.

Ceiling seam. When making a ceiling seam, the electrode is held perpendicular to the ceiling. The arc should be short, the speed of movement should be constant. To keep the metal in the seam, you can make small circular movements to the sides, widening the seam. Ceiling seams are considered the most difficult in welding technology. They should be started only after acquiring the skill of performing lower, horizontal and vertical ones. This cannot be achieved without practical work. Ultimately, only practice can teach you how to weld metal quickly and efficiently.

Welding thin metal. Welding thin steel is a particularly difficult task due to the risk of burn-through. The latter are fought in various ways.

• The welding current should be minimal, this will reduce the temperature of the base metal. Welding is carried out with reverse polarity.
• To avoid deformation of the structure, you need to weld intermittently, moving from time to time to another joint area. For example, start cooking from one edge of the joint, then move to the other, then to the center - and so on. This will prevent severe warping of the metal - especially if the length of the joint is long (more than 200-250 mm). The shorter the continuous seam, the less warping.
• With very thin metal, welding is carried out with periodic interruption of the arc, which is extinguished by withdrawing the electrode and quickly re-ignited.
• When overlap welding, it is necessary to ensure a tight fit of the top sheet to the bottom sheet using pressing weights or clamps. The presence of a gap between the sheets will lead to burning of the top sheet.
• When butt welding, you need to achieve a minimum gap between the edges along the entire length of the joint. The ideal case is a complete absence of gap. To weld very thin metal with an uneven joint, use an auxiliary pad under the joint - retractable and non-retractable, remaining with the part. As a retractable pad, it is good to use a thick copper plate (the thicker the better), which provides good heat dissipation and prevents burn-through. If a non-removable lining is structurally impossible, or there is no copper strip, you can weld the part with a steel lining, removing it afterwards with a grinder. A good way to weld thin steel is to flange the edges at an angle of up to 180°.

In general, before welding very thin steel, it is advisable to practice on a separate piece in order to adjust your own reaction to welding conditions. This will avoid the hassle of sealing the burnt holes.

Welding cast iron, stainless steel and non-ferrous metals

Each metal has its own welding characteristics, which sometimes introduce significant changes into the process, and the answer to the question “how to properly weld with electric welding” without considering the welding of cast iron, stainless steel and non-ferrous metals will be incomplete.

For example, copper, due to its high thermal conductivity, requires a greater concentration of energy in the welding zone than other metals, and if the part is massive, then preheating is indispensable. Copper welding.

Aluminum is a difficult material to weld due to the formation of an oxide film on the surface of the molten metal droplets, which prevents their fusion. Aluminum welding.

Cast iron is fragile and can crack due to significant temperature differences, and a large amount of carbon leads to undesirable chemical processes. Welding cast iron.

Stainless steel has low thermal conductivity and requires less current to weld than regular steel. Action is also required to maintain anti-corrosion properties. Welding stainless steel.

Titanium requires very careful protection from air gases. Titanium welding.

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One of the most inconvenient and difficult positions for welding is the ceiling. But it is worth mastering this type of connection due to the automatic increase in the class of a welder who has learned to make high-quality seams in such a spatial position. This is in demand at enterprises whose activities involve laying pipelines and at construction sites. This skill is also useful in everyday life, when welding heating or gazebos. Some elements of a metal garage cannot be assembled without welding joints at the top. How to weld a ceiling seam using electric welding? What are the main precautions and optimal device settings?

Many welders do not like ceiling seams because of the difficulties in their execution. A beginner’s results can often be poor, which discourages them from learning. But if you understand the main problems and prevent them as much as possible, then pretty soon, after training, you can master this difficult connection.

Welding a ceiling seam with an inverter or transformer is significantly different from working on a similar product in the lower position. When metal is welded on the floor, the weld pool spreads over the joint, and the welder only needs to ensure that the joint is properly filled, preventing slag from getting in front of the pool. When the ceiling serves as the working surface, the molten metal tends downward under its own weight.

The slag, being in a liquid state, also constantly drips, which interferes with the welding. These splashes hitting the ground scatter even more, hitting the welder and surrounding objects. The main difficulty when arc welding in the ceiling position of the seam is connecting the sides of the product. A weld pool forms on one edge, but there is no way to bond both sides with metal.

Welding of ceiling seams is performed at a reduced current, which leads to frequent sticking of the electrode and lack of penetration. Another defect is sagging. The body position with the head thrown back and the arm raised up quickly tires the welder. Therefore, frequent breaks are simply necessary for quality work. Understanding these complexities will help you tune in to the challenges and take steps to make the process easier to implement.

Ceiling welding technology

To understand how to properly perform this type of connection, you need to know the basic rules used by experienced welders. Additionally, you can see how to weld a ceiling seam using electric welding in the video. Here are the main points:

• The sides to be welded should be brought together as much as possible. Welding with gaps on the ceiling is only available to experienced specialists, so the more closely the parts are connected, the easier it will be to apply a seam.
• Edge cutting is carried out as in the lower position. When the thickness of the sides is more than 5 mm, a V-shaped bevel is made.
• The electrode is brought to the ceiling at an angle of 45 degrees relative to the upper plane. Beginner welders can try welding with half of the electrode, as this will allow better control of its tip and control the formation of the seam.
• The welding process and the seam itself in this spatial position are possible due to the surface tension of the metal. To prevent drops of molten iron from flying off before they catch on the edge, the current should be reduced.
• If the sides are brought close together, then the first seam on even plates can be made without oscillatory movements. This will fill the joint well. The second pass is made wider to strengthen the ligament. But on pipes it is better to immediately weld with a wide seam.
• Electrode welding can be performed in several ways: crescent, horizontal figure eight, or spiral. When there is a small gap, an intermittent arc is used to allow the deposited drop of metal to cool. After a moment, without allowing the red color to pass through (this can be seen through the mask), the next drop is applied. This is a long process, so the welder does not need to rush and needs to rest periodically.
• Do not be intimidated by the appearance of the connection after the work is completed. Slag can flow down several tiers. But after beating it off, a high seam should remain. Sagging and large rollers are not critical.

Devices and electrodes

Ceiling seams can be made using an inverter or a conventional transformer. It is important to correctly set the current strength, which is 25% lower than when welding on the floor. For example, for plates 5 mm thick, 100A is sufficient. It will be easier to work if the cable is not heavy. This will make it easier to control the end of the electrode and your hand will get less tired. You can also loop the cable around your hand to reduce the strain on your wrist.

Electrodes for ceiling welding are suitable with a diameter of 3 and 4 mm. It is important to dry them well to reduce the amount of splashing. If beginners use short electrodes, this will allow them to manipulate the arc more confidently.

Precautionary measures

For ceiling seams, you should wear a thick jacket and trousers. Gloves must cover the cuffs, otherwise scale will reach the elbows and burn the skin. A hat or cap without a visor is required on the head. It is important to choose trousers of such length that they cover the collar of the shoe to prevent molten particles from getting inside.

Today there are a wide variety of methods for joining metal. But in order to understand how to correctly lay a welding seam, it is necessary to study in more detail the principles and methods of welding. According to technical characteristics, methods are divided into two types:

• detachable;
• one-piece.

Detachable connections include those connections in which it is possible to separate parts without breaking the connecting elements. For example, a bolt and a nut. But a permanent connection is considered the most durable, since with it the parts do not separate without breaking the connecting parts. This type includes welding and rivet types of joining. If it is necessary to obtain a high-quality and reliable connection, a welding seam is the best option.

Often craftsmen purchase welding devices for welding elements without having any skills or experience in the work. And after failures, they begin to wonder how to properly lay a welding seam.

Principles of the Welding Process

Various types of welding.

Welding is the process of joining individual metal elements using electric welding. The connecting elements melt under the influence of an electric arc and an electrode, which is a metal rod with a special coating. c and the strength of the weld largely depend on various factors:

• welding device;
• current regulator;
• on the size of the electrode used;
• from the classification and skills of the welder.

In domestic and industrial areas, several types of welding are used, which, in turn, are divided into groups:

• gas press;
• contact;
• roller;
• electroslag;
• termite;
• friction.

When using gas press welding, an open flame of acetyl oxygen is used. The advantage of this method is its high productivity. This method is widely used in the gas and oil industries. It is common in pipeline laying and is also widely used in mechanical engineering.

If the network voltage is low, resistance welding is often used, but the electric current must be high. With this method, spot and butt welding is permissible. Consequently, it is easier to work along the seam.

To master welding technology, you need to purchase a welding device. You can rent it, and if you need it for long-term work, then it would be wiser to buy it. Today's specialized stores can offer a number of welding devices, among which there are also devices equipped with a current regulator.

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Sequence of weld laying

To learn how to correctly place a weld, it is important to take into account that the electrodes must be selected taking into account the thickness of the metal being welded, and the current strength must be set according to the electrodes.

The calculation method is not difficult, for example:

• when using welding transformers with an electrode cross-section of 1 mm, the current should correspond to 30-40 A;
• a welding inverter with an electrode size of 3 mm requires a current of 80 A, and with a current of 100 A it is possible to cut metal.

As for the room, this does not matter, but when carrying out welding work, to ensure fire safety, you need to stock up on a bucket of water. Before you start welding, you need to prepare all the tools so that they are at hand. The parts to be welded at the seams must be cleaned with a wire brush. To ensure that the seam is smooth and neat, it is recommended to pre-align the workpieces to be welded using clamps or a vice.

To have an idea of ​​how to properly work with electric welding, it is advisable to first practice welding beads on a plane, and when performing this process, the best option would be to use electrodes with a cross section of 3 mm, since they are the most common.

It is important to take into account that it is best to use newly purchased electrodes for work, since those purchased a long time ago can absorb moisture, which complicates the welding process.

The following actions:

1. It is necessary to attach the mass to the working element using a clamp;
2. The electrode is inserted into the holder.
3. The arc is ignited, and one of two methods is used: struck, like a match, or tapped on the part being welded.
4. Next, welding is performed by moving the electrode along the surface (the angle must be maintained at 75°), and oscillatory fractions must be produced; according to the principle of operation, this is reminiscent of raking a molten mass of metal under the crater of the arc.
5. The end result is a high-quality, even seam.

Making an even, high-quality seam is not difficult. It is important to have at least a little knowledge of physics, the necessary high-quality equipment and a little skill.

Welding is one of the main methods of fastening two elements, and welding seams are zones connecting two metal workpieces to each other. Such adhesions are formed during the melting and subsequent cooling of steel.

A good welder must know the types of welded joints and be able to apply all types of seams . Without these skills it is impossible to produce a high-quality and durable structure.

Types of joints

Welds are divided into 5 variations:

• overlap;
• parallel;
• butt;
• corner;
• t – shaped.

Lap joints are often used to create cylindrical tanks that are planned to be operated in a horizontal or vertical position. The elements to be welded overlap, but do not completely overlap. The result is a structure that looks like a step. Welding seams are applied to the end sides of the parts .

Parallel application methods are used to increase the strength of the structure. Both components are tightly applied to each other and fastened by welding from the ribs. This technique can be used to strengthen structures whose exterior will be subject to strong mechanical stress. However, such technology is prohibited from being used in the repair of moving mechanisms.

The butt version is the most popular. The parts to be welded must be in the same plane, one opposite the other. This joint is used to fasten water pipes, chimneys, storage facilities or steel columns. This system is also used in mechanical engineering, in the manufacture of air and water transport, and in military factories. Yes, and creating such a “glue” requires a minimum of money and time.

Corner types of welds are well suited for fastening several workpieces that need to be positioned at right angles. The workpiece is made as follows: parts are installed at an angle of 90° (in the form of the “G” symbol), and a weld is applied at the junction of the edges . This welding is common in both industry and private use. And with its help you can make durable supports or boilers.

A T or T weld is not like the others because the finished part will look like the letter "T". It will be difficult for an inexperienced person to create this, since in the process it is important to take into account the restrictions related to holding the electrode (it is recommended to adhere to an angle of 60°). In this case, the thickness of the joined sheets may differ. Also, more wire will be required for execution, and elements welded by the T-method may come out with defects.

Operating technique

Moving the rod along a solid line will not be enough for a good weld. , and to become a master of your craft, you need to understand the technique of using the device. The main features of the technology are constant control of the gap between components. If the distance is too small, the steel will not warm up well, which will negatively affect its strength. Both the speed of the tripod and the basic soldering procedure should be controlled. The main thing is that the molten metal is evenly distributed throughout the groove.

How to suture correctly :

1. Cook in a circular or zigzag motion. The trajectory must be maintained throughout the entire adhesion.
2. Hold the handle at the correct angle. The sharper the slope, the shallower the depth of steaming.
3. Control the pace of movement of the electrode. It all depends on the voltage of the device. Higher current allows the holder to move at higher speeds, and the resulting seams will be thinner.
4. Choose the adhesion layers wisely. Several rows can be made in the butt areas, however, a T-weld seam is most often made using this technique.

Taking these rules into account will help achieve the desired result, and the specialist will accurately produce any type of welding seam.

Application methods

Application methods include:

• Horizontal type. According to the rules, you can apply a seam both from right to left and in the opposite direction. Here it is important to maintain an acceptable angle of inclination, since excess molten metal will flow out. If a person has few skills, then the entire procedure can be completed in 2-3 passes.
• Vertical type. The work surface can be located in the ceiling or wall areas. Welding joints can also be made using two methods: top-down and bottom-up. However, it is better to choose the first option, since the heat from the arc contributes to high heating of the alloy.
• Ceiling type. The whole process must be completed very quickly, maintaining a stable pace of guiding the rod. Also, to maintain the alloy in the weld, you will need to make rotational movements. It should be noted that the current version is the most complex, and you should start working after gaining the necessary experience.

From the first time it is difficult to understand what types there are and to study all the technologies. But regular practice will turn any beginner into a real professional.