What is resistance welding

All about resistance welding - technology and equipment

[Resistance welding] is used for domestic and industrial needs.

The types of resistance welding used in various conditions are distinguished by their price, which increases depending on the power and speed of the work process.

Welding equipment is united by a common principle of operation - during operation, the seam points of materials are heated and welded through their contact with the base that supplies electric current.

General information about resistance welding

Electric welding is a connection in which the parts to be welded are heated by direct or alternating current.

The photo below shows a diagram that a resistance welding machine may have.

Like all production equipment, electric resistance welding has advantages and disadvantages.

Among the main advantages are high productivity, minimal costs of consumables and ideal quality of the welding seam.

The time it takes to connect a point is a fraction of a second and depends on the parameters of the material.

During the welding process, a minimum amount of air and water is consumed, and even a welder without qualifications can ensure the quality of the seam.

At the same time, the contact welding technology is environmentally friendly and can be automated.

Welding work is carried out using special and universal machines and devices.

The nature of the technical action allows us to divide contact welding equipment into classes:

• mechanical models - endowed with minimal power;
• automatic and semi-automatic - can have medium and high operating power, used for processing continuous workpieces.

Depending on the type of installation, electric contact welding can be portable or mobile, suspended, or stationary.

The first option is indispensable if it is necessary to weld large-sized objects with a large mass of components. For example, pipes, transport bodies, railway cars and rails.

Stationary equipment is used for processing products whose weight and dimensions allow them to be delivered to the workplace.

Equipment classification

A resistance welding machine, in accordance with GOST 158-78-79, comes in different types depending on the type of welding seams.

Joining machine

Resistance butt welding is the process of heating a butt seam passing through the entire plane of the part.

The butt joint is most often used for welding copper pipes; seam and spot technology for copper pipes is not practiced.

At the same time, processing copper pipes using the reflow method is difficult due to the need to maintain molten metal at the ends of the elements being welded.

Therefore, using butt technology, if pipes are welded, it is not from pure copper, but from its alloys. Otherwise, it is necessary to use high pressure, up to 400 MPa.

IMPORTANT TO KNOW: Using borax for brass soldering

Contact butt welding, depending on the characteristics of the metal structure, the area being processed and the expected quality of the weld, is carried out using different methods.

In this case, contact butt welding in accordance with GOST 2601-84 can be carried out using resistance technology, reflow with heating and continuous reflow.

Resistance - used when welding material whose cross-sectional area does not exceed 200 mm².

As a rule, this flash butt welding technology is used for processing low-carbon steel products with a small cross-section (pipes, wire, rods).

Melting - this technology allows you to connect material in the form of reinforced concrete products, pipes, profile steel and fittings, with a cross-sectional area of ​​up to 100 thousand mm².

The technology has found its application in the field of shipbuilding, in the manufacture of chains for anchors, coils of refrigerator refrigeration units.

In the railway sector, where such welding equipment makes it possible to connect railway rails on continuous tracks. Its use makes it possible to produce long products from ferrous and non-ferrous metals.

Seam resistance butt welding

The machine, made in accordance with GOST 2601-84, allows you to connect the material using cast zones, which are a seam consisting of separately located welding points.

The zones either overlap or do not overlap each other, depending on which the weld can be sealed.

For this welding process, a special machine is used, equipped with one or more rotating disks with electrodes.

Roller welding technology allows for tightly compressed, rolled and high-quality joining of parts.

Roller welding is used for the production of pipes, tanks and other products that require, in accordance with established GOST requirements, highly reliable sealed seams.

Relief welding

In accordance with GOST 2601-84, relief welding is a machine that allows you to connect relief protrusions at one or several working points at the same time.

This machine is similar in principle to a resistance butt welding device; the difference between them comes down to determining the welding location by the shape of the surface of the products, and not by the working area of ​​the electrodes.

Relief protrusions can be located on one or simultaneously on two welded products; they are prepared in advance by stamping.

Resistance resistance welding is used in the automotive industry, where the device allows you to fix various types of brackets to sheet material.

In the field of radio electronics, projection welding is used for high-quality connection of wires to thin elements.

Resistance spot welding

In accordance with GOST 2601-84, this welding technology makes it possible to connect elements at one or many points at once.

The strength of the connection can be determined by such characteristics of the weld point as size and structure; in turn, they depend on the parameters of the electrodes used, the strength and speed of current passing through the material.

IMPORTANT TO KNOW: Optical fiber splicing - equipment and technology

The butt welding regulator, present in modern machine models, allows you to carry out the work process with different welding current options.

As a rule, in seam technology there is no resistance welding regulator, and the required cycle is provided by synchronous interrupters.

The resistance spot welding machine is usually operated on an assembly line. The welding element of a contact connection in this category is electrodes.

The tool is replaceable, as it wears out quickly.

Electrodes for welding are made of high-quality bronze and copper, the additional components are chromium, cadmium, titanium and beryllium, depending on this the price of the product varies and can range from $1-5.

The technology of such welding has found its application in the automotive, aircraft, shipbuilding and agricultural sectors, as well as other industrial areas.

A variation of this type of welding is pulsed welding, when the electrode is heated due to short-term but powerful electronic pulses. Pulse welding is used in automobiles, equipment and repairs.

For example, pulse technology is useful when resistance welding of aluminum is used, which reduces the risk of overheating of the device and wear of the electrodes.

Pulse welding is operated using alternating current and energy converted into a pulse of a certain shape.

At the same time, pulsed resistance welding technology differs in its work with accumulated energy and in the rectified current pulse.

At the moment, the price for such a device (pulse welding for household use) is $100-140.

Electrode characteristics

Electrodes for resistance welding ensure contact of the welding machine with the workpiece.

The scheme of their purpose includes: sealing parts, supplying current, removing heat emanating from parts, moving elements (resistance seam welding).

At the same time, the productivity and quality of the welded seam is influenced not only by the design of the electrodes, but also by the material being processed, its area and the shape of the working surface.

General standard requirements for electrodes, marking rules, testing methods for welded joints and seams, and other technical issues are specified in GOST 9466-75.

Electrode wear is caused by changes in current and temperature.

Therefore, when producing consumables for contact welding, a metal that is resistant to high temperatures and has high conductive properties is used.

It can be a special copper alloy. For example, contact welding of copper is often carried out with electrodes made of cadmium bronze; the price for them can be $1-3.

Electrodes for spot contact welding can have a straight or shaped shape, as in the photo. But most often the first type of this design is used.

They are used when welding pipes and other products with the possibility of free access to the work area.

IMPORTANT TO KNOW: Tips and lessons on arc welding

Electrodes with a straight shape are produced in accordance with GOST 14111-90 standards, with a diameter from 12 to 40 mm.

The highest quality electrodes are considered to be products whose design is made in accordance with GOST 1411-69 regulations.

Here the price of products increases depending on their purpose and structure.

The design of shaped electrodes is more complex - the axis running through the center of the working area is shifted by a certain distance relative to the landing axis.

Electrodes of this type are inconvenient to use and most often have low resistance, which is why they are used only in cases where resistance welding cannot be performed by any other method.

For relief welding, flat electrodes are used. Moreover, in each of them or in one there may be holes intended for protrusions of the elements to be welded.

Features of welding machines for household use

When planning to purchase a welding machine for your own needs, you initially need to know what material will be processed and on what scale the work will be carried out.

The price of a spot welding machine largely depends on the characteristics and design parameters, as well as on the operating power of the equipment.

At the moment, the installation for spot welding elements can be manual or portable, suspended or stationary.

Suspended and stationary equipment is usually used in large and small industries.

But a portable machine is most often used in everyday life; its price is quite reasonable and can range from $120-220.

At the same time, the specified device may not be inferior in power to spot welding machines, the price of which is twice as high.

Portable equipment is divided into two types: inverter and machine with pliers for manual spot welding.

Inverter devices are compact in size and light in weight. The design uses a thyristor current generator and a microprocessor.

In this connection, the device circuit allows you to adjust the pulse duration and operating power of the unit.

At the same time, for this category of welding machines, household power supply is quite sufficient.

The second model for spot welding with manual pliers has a weight of no more than 15 kg.

The device circuit, using a microprocessor, allows for manual and automatic adjustment of welding work in several modes.

The device with clamps is powered from a single-phase household electrical network.

The device is equipped with a manual compression drive capable of providing a pressure of 150 kg.

Source: https://rezhemmetall.ru/kontaktnaya-svarka-metalla-texnologiya-i-instrukciya-po-svarke.html

Resistance spot welding: general information

Resistance welding is one of the types of welding work where metal is melted under high heat using a pressing press. Basically, this method is used in industrial mass production, in factories for the production of aircraft, cars, and in the creation of microcircuits, but it is possible to master this method at home.

Welding Features

Resistance welding technology in production is a complex machine with many functions. An important component is the electrode, with the help of which the point connection is made. For contact welding, it is better to use copper electrodes.

The second main component is the regulator. Thanks to it, the sequence of operations is carried out, their duration is controlled, and the welding current is regulated without sudden jumps.

Resistance welding is not possible without a converter and switching device that transform the electric current. Spot welding requires high current strength at low voltage from 1V to 16V. This reduction is carried out using a transformer. Parameter settings are specified in the operating instructions for the welding machine, depending on the thickness of the metal walls.

Modern welding machines are equipped with a large number of electronics that simplify the work of the welder. Many processes are automated.

Advantages and disadvantages of resistance welding

This type of welding is widely recognized, and here's why:

• high productivity, a single metal connection occurs in a fraction of a second, it is easy to calculate that in a minute of work a welder can perform up to six hundred fastenings;
• the electrodes are durable and do not require frequent replacement;
• welding is easy to perform, beginners will quickly master this method with the correct machine settings;
• no need to purchase consumables. No shielding gas, fluxing agents, or filler materials are needed;
• environmentally friendly welding, it is not harmful to human health.

But such advantages do not come without disadvantages, these include:

• high cost of equipment;
• the power source must be stable without sagging, since a current of up to 1000 amperes is applied;
• State standards apply to resistance welding, without compliance with which the connection is considered defective.

Despite the fact that GLSTs for spot welding were introduced back in the last century, they still exist and connections are controlled according to their requirements.

What are the types of contact welding?

There are four main types of surface welding:

• pointwise is the most common method used in all areas of activity. A strong connection can be obtained at one or more points with appropriate welding mode settings. Allows joining very thin sheets from a few micrometers to two millimeters;
• butt to butt – in this type of contact welding, 3 methods of butt jointing are known:
• with resistance, the parts are combined with each other and strongly compressed, after which an electric current is applied, which heats the metal and melts it, resulting in a strong connection;
• with continuous heating, in this option the parts are melted and only then combined, temperature heating is maintained throughout the entire welding process;
• with discontinuous reflow, as in the previous case, the parts are heated and joined, but heating and cooling are performed alternately. This method is more economical for large enterprises.

With this method, the connections are clean, since under the influence of physical properties all oxidation and foreign substances are eliminated from the contact zone.

• suture method creates tight connections. The use of roller electrodes completely seals the welding seam from the ingress of the smallest particles. Used in the production of containers for gasoline and water supply. Can weld metal from 0.2 mm to 3 mm;
• relief. This type of welding is used in the automotive industry. Requires some additional preparation of welding elements. It is not enough to clean and degrease the surface; you also need to make relief depressions with a special tool, after which the welding itself is carried out.

Resistance welding is divided into one-sided, when the electrode is applied to only one part (for example, there is no technical possibility to capture the second point) and two-sided, when the electrodes are located on both sides of the surfaces being welded. The second method is more reliable and durable.

Legend

When reading the drawings, you may find it useful to know how resistance welding is indicated. The following schematic signs are used under existing standards:

• a solid line indicates a visible seam;
• hidden solid connections are drawn with a dotted line;
• all other connections are shown as a thin line;
• visible spot welding is indicated by a plus;
• invisible spot welding is not displayed at all.

If additional information is required, footnotes are provided on the drawings. They may contain data about hidden and visible seams. Resistance welding is usually denoted by a capital letter K, and the type of welding is indicated by a small letter next to it. For example, the designation Kt indicates that welding was performed using the contact spot method.

Source: https://svarka-weld.ru/kontaktnaya-tochechnaya-svarka-principy-sposoby-raboty-i-ee-vidy

Basic principles of resistance welding

Resistance welding is used to connect metal elements using pressure and an electrical impulse. The main area of ​​use of this type of welding work is the industrial production of various types of mechanisms, cars, airplanes, ships, and units for agricultural use.

Due to their high quality and the ability to quickly create multiple welding points, such devices are gaining wide demand. On an industrial scale, such an installation is undeniably better than an inverter, since the speed and quality of welding is often much better.

A little about the principle of welding

The principle of welding is quite simple, but this is only at first glance. Under the influence of pressure, welding electrodes compress two parts at the required point with a set force, after which a current pulse is applied. The current heats up the welding site and melts it to a liquid state. Since the welding time is quite short, the point immediately begins to crystallize and form a welding core at the heating site.

To increase the strength of the connection, the pressure must continue after the electrical pulse is turned off for a certain period of time. After which the core acquires the most fine structure possible, and the strength becomes close to the base metal. Ideally, after turning off the current, the pressure should increase.

In this article we will analyze the working process of resistance welding, find out what types and features of welding there are. Let us describe the types of electrodes and what they are needed for. Having dealt with these questions, you will be able to clearly understand what electric resistance welding is and what it is intended for.

Work process

Electric resistance welding is divided into stages, which result in a high-quality design. The whole process can be divided into the following points:

1. Selection of materials that will be used to create the part.
2. Determining the most suitable device in terms of characteristics and structural features.
3. Preparing the metal surface.
4. Start of welding, installation of the workpiece, impulse delivery, cooling.
5. Final quality control, checking for defects and defects.

Having gone through all the stages, you get a completely finished, high-quality welded part, which can already be subjected to further processing. The heating and cooling process itself is very fast; some machines are capable of creating up to six hundred points in one minute.

Types of welding and their features

Contact connections are divided into four categories, which have their own characteristics and methods of application. Let's look at what types there are:

• Contact point.
• Butt.
• Contact suture.
• Embossed.

Now let's talk in more detail about each of them, so that you can specifically understand what each type represents and what its features are. Spot welding joints help to connect parts in one or many places at once with points. The point is formed in the process of heating and melting the metal under the influence of an electric pulse current, the shape of the electrodes that exert pressure on the material and the heating time.

Different variations of all these indicators help to make a weld spot of any shape, strength, etc.

Classification of welding types

Widely used in large-scale production and in serial production of mechanisms of the same type.
Also used to create rechargeable batteries. To connect parts simultaneously over the entire area of ​​their joint, a contact butt joint is used.

Thanks to this method, two parts are subsequently heated and combined into a single structure over a large area at once, in a short period of time. The time and method of such joining depends on the characteristics of the metal, the total area to be welded and the required strength of the connection.

Types of welded joints

Butt welding is performed using three methods:

1. Resistance.
2. Continuous reflow.
3. Melting with simultaneous heating of the welding site.

For parts with a small cross-section, up to two square centimeters, the resistance method is used. This method is also often used for pipes made of metals with low carbon content. For parts whose cross-sectional area does not exceed 10 thousand square centimeters, the melting method is used. The scope of application is very wide, from welding reinforcement structures in reinforced concrete to creating a seamless railway.

This technology helps to produce parts of very long lengths without leaving any noticeable seams. Using fusion, cutting tools are welded, for example, drill tips or knife blades. Massive chains of ship anchors are welded. Hot flashing, a modification of conventional flashing, is used to create a higher-quality weld.

Seam resistance welding is performed by welding several points in a row. Such points can be sealed if they are overlapped. If you leave a gap, it will be almost similar to a regular, dotted one. This welding process can be performed on one or more welding machines. The disc roller unit rotates along the contour that needs to be welded, leaving behind points.

If roller rolling occurs on one side, then it is one-sided. If roller rolling is on both sides, then the connection occurs on each side. This method is good because it can be either unilateral or bilateral, which is good in certain cases.

The highest quality seam is obtained on metals with a thickness of 0.2-3 millimeters. They are used to create sealed seams in aluminum barrels, canisters and other containers.

Contact relief welding is very similar to spot welding. To carry it out, special convex sections are prepared in advance and welded. The main feature is that the shape of the weld point in this case depends on the shape of the convexity that was made, and not on the shape of the electrode used. The scope is quite wide, from cars to various electrical appliances.

Characteristics of the electrodes used

The electrodes have the following characteristics, thanks to which it is possible to make high-quality welding:

• High temperature resistance (can withstand temperatures over six hundred degrees).
• High density of the material, which allows it to maintain its shape, even with shock compression equal to five to six kilograms per square millimeter.
• Very high thermal and electrical conductivity. Due to their high electrical conductivity, they can transmit a current pulse without loss.
• For single-sided or double-sided welding, the electrodes have a flat disc shape. For other types, barrel-shaped elements are used.

After reading this article, you were able to understand the technological process of the resistance welding device. We learned what types of resistance welding there are, and what types of electrodes are divided into. Now we can move on to the practical study of this process.

Source: http://GeneratorVolt.ru/invertornyjj/osnovnye-principy-raboty-kontaktnojj-svarki.html

What is contact electric welding, principle of operation, technology of operation

Thanks to welding in a garage or on a summer cottage, you can do a lot with your own hands. It is necessary to understand that there are many devices designed for welding work.

There are types of work that will take several days, but if you use the appropriate welding machine, then the same work can be done in a few hours. One of the varieties of such devices is resistance spot welding.

But you need to know that this device is not suitable for all types of work. For example, it cannot be used in a heating system or for sutures.

Spot welding is a very popular method of welding metal together. In this method, metal products are connected to each other at several points - this method influenced the name of the working technology. The size of the point will influence the level of strength of the connection. Butt spot welding can only be used in cases where the metal thickness does not exceed three millimeters. The choice of device depends entirely on the thickness and type of material.

Operating principle

The formation of compounds occurs due to the process of heating the metal through which a current discharge is passed. As a result, deformation of the welding zone occurs due to the compressive force.

The technology of resistance spot welding is based on the principle of heating metal using an electric discharge. During the welding process, a current discharge passes between the electrodes and at the same time between the elements of the material being welded and secures them to each other. In order to reduce the resistance between the electrode and the material being welded, materials with a high level of electrical conductivity are used in the manufacture of electrodes.

Due to the fact that there is a certain resistance between the parts, the greatest heating occurs precisely in the places of maximum values. This results in the formation of small weld spots. The diameter of each point can vary from 4 to 12 millimeters.

Options

In order to use contact spot welding, you need to know the basic parameters of the tool. These include:

• Current strength during operation. Current strength is the main parameter during operation. In order to determine what level of current will be required during operation, special forms, calculations, tables and drawings are used.
• Pulse duration. By welding time it is customary to refer to the pulse duration of the current for one point. In order to correctly calculate the welding time, it is necessary to take into account the characteristics of the material.
• Electrode compression force. This process affects the level of deformation, heat distribution and degree of cooling.
• Characteristics of the working surface of the electrodes used. Thanks to them, contact occurs during welding. There are straight and shaped electrodes. Each electrode meets the requirements of GOST. The material from which they are made is copper alloys. Thanks to this, the electrodes are able to retain their functional properties for a longer period.

Operating modes

At the moment, there are two operating modes of the welding machine:

1. Soft mode features gradual heating using current. The heating process takes place in a few seconds. The main characteristics include: low power consumption, low load on the electrical network. This mode allows you to use the device at home.
2. Hard mode is characterized by a short process duration, which lasts up to one and a half seconds. The current strength and compression pressure are much higher than that of the soft mode. The main disadvantage is the increased power requirement of the welding machine and the high load on the electrical network. The advantages include high productivity in a relatively short time.

Based on these modes, all welding machines are divided among themselves by power level. Therefore, there is a large product range, which includes equipment not only in the form of powerful devices, but also small portable equipment.

Device

Regardless of the model, operating mode and operating voltage, all welding machines have the same main parts:

• Transformer.
• A mechanism that is used to compress the electrode.
• Current regulating device.
• Current and pulse duration control system.

Low power devices may not have a control system. The pulse duration in this case is adjusted manually.

With conventional similar welders it is possible to regulate:

• Current strength.
• The time it takes for the current to pass.
• The force with which the electrode is compressed.

When starting work, be sure to monitor the electrodes; their diameter should not increase. The size should remain the same as the size of the welding spot. Even though the electrodes are made from a copper alloy and are highly durable, they can still wear out during use, so they should be replaced as needed.

Work technology

In order for the part to heat up to the required temperature, a significant current pulse is applied to it in a short period of time. In this case, the metal begins to melt, which leads to the formation of a liquid core between the parts. The parts to be welded should be held until the molten metal has cooled.

Pressure on the parts is required so that during the melting of the metal a sealing belt is formed, which does not allow the molten metal to flow beyond the welding site. In order for the parts to be connected reliably, the planned welding site should be treated, this allows you to remove corrosion and oxide film.

If necessary, you can use the video and photo materials provided, where you can see the welding process in detail.

Continuous reflow welding

To use this method, it is necessary to secure the parts to be welded into the clamps of the welding machine and only after that can it be turned on. After the electric welding is turned on, the process of melting the ends of the parts takes place.

After the metal has been deposited to the required amount, the device should be turned off. This method is used to connect sheets of metal and pipes together. The benefits include a high level of productivity.

The main disadvantage is that you can lose metal due to spattering.

Intermittent reflow welding

This method is performed with alternating tight and loose connections of parts during operation. In the process of clamping parts, a periodic closure of the electrical circuit occurs. The parts will be heated until the temperature reaches 900 degrees. After heating, the parts are melted and deposited.

Resistance welding

When using this method, the parts must be connected, after which they are compressed and current is applied. After the parts reach the required temperature, the transformer turns off. When using this method, you need to monitor the heating temperature. To work, the surface must be clean.

Main stages of work when spot welding

Let's consider the main stages in the work process:

• It is imperative to prepare the edges of the material being welded for welding.
• The parts must be aligned in the desired position and placed between the electrodes.
• Heat the material until it becomes plastic.
• The deformation process completes the work stages.

In order to prepare the edges of the material for welding, it is necessary to clean it until a metallic shine is formed and degrease the surface. During welding, the parts must fit tightly to each other.

Advantages

When using a welding machine, you need to know not only general information - what it is, how the work process is carried out, but also understand all the disadvantages and advantages of the work.

The main advantages include:

• The ability to connect the thinnest parts made of different metals. In such cases, spot welding equipment is considered an indispensable item.
• When connecting parts, you can be sure of the strength of the connection. In addition, the appearance of the connection remains attractive. When using this device, you should know that the welding site will not change its appearance and will not age.
• High level of productivity.
• Electrodes are consumed sparingly, which allows you to reduce the amount of money for their purchase and replacement.
• This device can be used by anyone, even if they are not qualified in this field. If you have no experience in using a welding machine, then it is best if, before starting work, you look at information materials that will help you understand how to handle the machine and perform the process of joining parts.

At the moment, automated devices are becoming more and more popular. Thanks to this, you can significantly reduce operating time, increase productivity and reduce the cost of the device.

Defects during operation

All defects are conventionally divided into visible and invisible. Let's consider visible defects during spot welding:

• Appearance of cracks.
• Burning of material.
• Formation of gaps.
• Darkening of the surface of the dots.
• Formation of dents.
• Disproportional shape of weld spots.

Let's pay attention to invisible defects:

• The joints are not welded.
• Internal damage appears - cracks.

Defects can form due to the wrong choice of welding technology, incorrect treatment of the surface of the part before starting work, during work the electrodes are not cooled sufficiently, or wear of the electrode occurs. External defects can be identified immediately during operation. To identify internal ones, you need to use special methods and equipment that are used in production.

Safety precautions

When using any equipment, you should follow safety precautions. The following is required:

• Means of protection. To avoid electric shock, it is necessary to ground all parts that initially require it. To protect yourself from possible burns, you need to wear protective clothing, as well as respiratory and eye protection.
• Device safety. The device must be in good condition during operation. All these measures must be observed in order to protect yourself from possible damage.

Download GOST

GOST 15878-79 “RESISTANCE WELDING. WELDED CONNECTIONS. CONSTRUCTION ELEMENTS AND DIMENSIONS”

Source: https://oxmetall.ru/svarka/kontaktnaya-printsip-dejstviya-tehnologiya-raboty

General information about spot welding

Resistance spot welding is one of the most popular welding methods. It allows you to quickly and efficiently join thin metals. In this article we will tell you what spot welding is, what the technology of resistance spot welding is and what defects can result if welding is performed incorrectly.

general information

Spot resistance welding is one of the types of resistance welding. In addition to spot welding, there are also butt, seam and other types of resistance welding, but it is spot welding that is most widespread, so we’ll talk about it in this article. Spot resistance welding is used in many areas: from construction to aircraft manufacturing. For example, when constructing modern airliners, millions of points are located on the hull, forming a strong seam.

The principle of operation is simple: using an electric discharge, the metal is heated at a certain point to its melting point. At the same time, the two parts are pressed against each other with a certain force. Under the influence of temperature and mechanical load, the parts are connected to each other. A very aesthetic and reliable seam is formed.

Multi-spot welding differs from other types of resistance welding in several ways.

First of all, the spot method allows you to significantly reduce welding time (one “point” of the seam is formed in a fraction of a second), while the work uses high values ​​of welding current (more than 1000 amperes), also sets a low voltage (no more than 10 watts), the melting zone small (from a few mm to 1-2 centimeters), a significant mechanical load is used, which can reach up to several hundred kilograms.

In most cases, spot welding is used when thin sheet metal or rod materials need to be overlapped. Spot welding is capable of joining metal with a thickness of 1 millimeter to 3 centimeters, but such indicators are redundant and in practice you will not have to weld parts thicker than 5-7 millimeters. For this reason, spot welding is great for auto body work.

Advantages and disadvantages

The great popularity of do-it-yourself spot welding is due to many advantages. To work, you do not need electrodes, wire, fluxes, and so on. And this saves not only time, but also finances.

Also, the deformation of the metal is insignificant and only in places of “points”; the spot welding machine is very convenient to work with, even a beginner can cope with this task. The seam itself turns out very neat, the workflow is cheaper than analogues, and it can be easily automated.

It is multi-point welding that can perform a huge amount of work, forming up to several hundred weld “points” per minute.

The disadvantages are minor and few. Seams made by spot welding do not have such good tightness as connections made using electrodes, for example. There may also be excess voltage in the area where the “point” is formed; this needs to be monitored.

Welding technology

Resistance spot welding technology consists of three stages, which we will describe in detail. First, the parts are prepared (we will talk about this in more detail later). Then the parts are placed under the tip of the welding machine and are subjected to compression, as a result the surface of the metal is deformed and a small depression is formed - a dot.

Then an electric current is applied, the metal heats up, melts and a so-called liquid core is formed at the “point”. Gradually, the current penetrates through the entire core, and it increases in size. The "spot" becomes part of the weld.

And thanks to the preliminary deformation of the parts, the metal does not spatter during melting and the seam is neat and does not need to be cleaned.

Then the current supply is stopped, the metal cools and crystallizes. The liquid core becomes molten. But there is a nuance: when cooled, the core may decrease slightly in size and residual stress is formed.

It is undesirable and can be dealt with using different methods. We recommend that before completing the welding process, press the parts harder against each other in order to properly heat them and make the seam more uniform.

Otherwise, do-it-yourself spot welding is very simple and does not require highly qualified welders.

Metal preparation

Do-it-yourself spot welding, like any other welding method, requires preliminary preparation of the metal. To do this, you need to clean the areas of the future seam from dirt, corrosion and oxide film (if any).

If this is not done, power will be lost during welding and the degree of wear on the welding machine will increase. To clean the metal, use the sandblasting method, an angle grinder with a wire brush or sandpaper.

You can also etch a small part in a special solution.

Pay special attention to the preparation of aluminum and its alloys. There is a thick oxide film on the surface of this metal, which prevents complete heating and welding of the part. So remove it thoroughly before starting work. This is especially important if particularly important structures are to be welded.

Welding equipment

To do your own spot welding, you will need equipment. You can use a device operating on direct or alternating current, a capacitor-type device, or equipment operating at a low frequency.

All these types differ in the power electrical circuit and the shape of the welding current. Also, each type has its own pros and cons, do not listen to those who tell you about the superiority of this or that equipment.

In our practice, we use a device that runs on alternating current; this is the most common option. You can choose another type of equipment.

Pay attention to modern TIG LORCH welding, it is very technologically advanced.


Possible welding defects

With proper experience and knowledge in your head, resistance spot welding should not turn out bad. Moreover, it is not so complicated and its basics can be learned fairly quickly. But if mistakes were made or the work was entrusted to an inexperienced craftsman, then various defects are possible. Moreover, they are formed not in the place of the points, but along the base metal.

Defects can be of various types. Often the cast core is too large or small, or it is offset from the center of the joint. Also, the distances between the points are too large and the seam is not continuous. Sometimes during operation, beginners may adjust the device incorrectly, which leads to excessive deformation of the metal.

But the most dangerous defect is an uncooked cast core or its absence at all. Such a part, of course, will be able to withstand small loads, but soon it will simply break at the joint. In this case, a defect can be detected under the most unusual conditions, for example, during temperature changes (the part was taken from a warm workshop to the street in winter).

If a mistake was made, but the part did not break, then do not think that you are lucky. Most likely, corrosion has already begun to form at the site of lack of penetration or any other type of defect. So the destruction of the part is only a matter of time.

To weld correctly, follow our recommendations: the point should be located in the middle of the joint, the cast core should not be too large or too small, should not be porous and should not contain slag inclusions, no cracks, and no too much stress in the weld area. Don't rush, practice more. Only with experience can you understand all the features of spot welding.

Instead of a conclusion

Source: https://svarkaed.ru/svarka/vidy-i-sposoby-svarki/obshhaya-informatsiya-o-tochechnoj-svarke.html

Resistance welding - technology, types, designation

Resistance welding is the process of creating a monolithic weld by melting the edges of the parts being welded with an electric current and subsequent deformation by compressive force. The technology has become particularly widespread in heavy industry and serves for the continuous production of similar products.

This technology is common for serial joining of thin sheet metal

Today, at least one resistance welding machine is available in every plant, and all thanks to the advantages of technology:

• productivity – a weld point is created in no longer than 1 second;
• high stability of operation - once the device is configured, it can work for a long time without third-party intervention, maintaining the quality of work;
• low maintenance costs - this applies to consumables, the working element is contact electrodes;
• Possibility of working with the machine by low-skilled specialists.

Resistance welding technology

Simple, at first glance, resistance welding technology consists of a number of procedures that must be performed. A high-quality connection can only be achieved if all technological features and process requirements are met.

Essence of the process

First, let's figure out how this system works?

The essence of electric contact welding is two inseparable physical processes - heating and pressure. When electric current passes through the connection area, heat is generated, which serves to melt the metal. To ensure sufficient heat generation, the current must reach several thousand or even tens of thousands of amperes. At the same time, some pressure is applied to the part from one or both sides, which creates a tight seam without visible or internal defects.

The joining process involves local heating of the workpieces while simultaneously pressing them

If the process is properly organized, the parts themselves are practically not subject to heating, since their resistance is minimal. As a monolithic connection is created, the resistance decreases, and at the same time the current strength. The electrodes of the welding machine, which are subject to heating, are cooled by the introduced technology using water.

Surface preparation

There are many technologies that allow you to treat the surface before using resistance welding. These include:

• cleaning from coarse dirt;
• degreasing;
• removal of oxide film;
• drying;
• passaging and neutralization.

The order and technologies themselves are determined by the specific process and type of workpiece.

In general, before welding begins, the surface must:

• ensure minimal resistance between the part and the electrode;
• ensure equal resistance along the entire length of the contact;
• The parts to be welded must have smooth surfaces without bulges or depressions.

We recommend! How to weld titanium in argon

Resistance welding machines

Equipment for resistance welding is:

• motionless;
• mobile;
• suspended or universal.

Welding is divided according to the type of current into direct and alternating current (transformer, capacitor). According to the welding methods, there are spot, seam butt and relief, which we will talk about below.

The equipment can be either stationary or portable

All spot welding devices consist of three parts:

• electrical systems;
• mechanical part;
• water cooling.

The electrical part is responsible for melting parts, monitoring work and rest cycles, and also sets the current modes. The mechanical component is a pneumatic or hydraulic system with various drives. If only a compression drive is installed, then we have a point type, seam drives also have rollers, and butt drives have a system for compressing and upsetting products. Water cooling consists of a primary and secondary circuit, distribution fittings, hoses, valves and relays.

Electrodes for resistance welding

In this case, the electrodes not only close the electrical circuit, but also serve as a heat remover from the welded joint, transmit mechanical load, and in some cases help move the workpiece (roller).

The sizes and shapes of electrodes for resistance welding vary depending on the equipment used and the material being welded

This use imposes a number of stringent requirements that the electrodes must meet. They must withstand temperatures over 600 degrees, pressure up to 5 kg/mm2.

This is why they are made from chrome bronze, chrome zirconium bronze or cadmium bronze. But even such powerful alloys are not able to withstand the described loads for a long time and quickly fail, reducing the quality of work.

The size, composition and other characteristics of the electrode are selected based on the selected mode, type of welding and thickness of the products.

Welding defects and quality control

As with any other technology, welding joints must be subject to strict control to identify all kinds of defects.

Almost all non-destructive testing methods are used here and, above all, external inspection. However, due to the pressing of the parts, it can be very difficult to identify defects in this way, so part of the manufactured products is selected and the parts are cut along the seam to identify errors. If a defect is detected, a batch of potentially defective products is sent for processing, and the device is calibrated.

We recommend! Semi-automatic welding of stainless steel

Types of contact welding

The technology for creating a weld spot determines the division of the process into several types:

Spot resistance welding

In this case, welding occurs at one or simultaneously at several points. The strength of a seam consists of many parameters.

The spot method is the most common method

In this case, the quality of work is affected by:

• electrode shape and size;
• current strength;
• pressure force;
• duration of work and degree of surface cleaning.

Modern spot welding machines are capable of operating with an efficiency of 600 welded joints per minute. This technology is used to connect parts of precision electronics, to connect body parts of cars, airplanes, agricultural machinery, and has many other areas of use.

Seam welding

A multi-spot welding process in which multiple weld joints are placed closely or overlapping to form a single monolithic joint. If there is overlap between the points, then a sealed seam is obtained; if the points are close together, the seam is not sealed. Since a seam using the distance between points does not differ from that created by a spot seam, such devices are rarely used.

In industry, the most popular is an overlapping, sealed seam, which is used to create tanks, barrels, cylinders and other containers.

Butt welding

Here the parts are connected by pressing them against each other, and then the entire contact plane is melted. The technology has its own varieties and is divided into several types based on the type of metal, its thickness and the required quality of the connection.

Welding current flows through the joint of the workpieces, melts them and reliably connects them

The simplest method is resistance welding, suitable for low-melting workpieces with a small contact patch area. Reflow and preheat fusion welding is suitable for stronger metals and larger cross-sections. This method is used to weld parts of ships, anchors, etc.

We recommend! How to cook cast iron using electric welding. Welding with inverter

The most popular and used ones are described above, but there are also the following types of spot welding:

• seam-butt welding is carried out by a rotating electrode with several contacts to close the circuit; by pulling the workpiece through such a device, you can get a leaky continuous seam consisting of many weld points;
• the relief-point part is welded according to the current relief, however, the seam does not consist of a continuous contact patch, but of many points;
• according to the Ignatiev method in which the welding current flows along the parts being welded, so the pressure does not affect the heating of the product and its welding.

Resistance welding designation in the drawing

According to the existing standard of symbols, spot welding has the following symbol on the drawings:

1. Full seam. The visible continuous seam on the general plan of the drawing is marked with the main line, the remaining structural elements with the main thin line. The hidden continuous weld is indicated by a dashed line.
2. Weld points. Visible welded joints in the general drawing are marked with a “+” symbol, while hidden ones are not marked at all.

From a visible, hidden solid seam or visible weld point there is a special line with a leader on which auxiliary symbols, standards, alphanumeric signs, etc. are marked. The designation contains the letter “K” - contact and the small letter “t” - spot, indicating the method of welding and its type. Seams that do not have a designation are marked with lines without flanges.

GOST 15878-79 Regulates the dimensions and designs of resistance welded joints

All basic information is presented on the leader line or below it, depending on the facing side (front or back). All necessary information about the seam is taken from the corresponding GOST, which is indicated in the footnote or duplicated in the table of seams.

Source: https://svarkagid.ru/tehnologii/vidy-kontaktnoj-svarki.html

Contact welding: features and types

Resistance welding is a popular technology that is actively used in industrial and domestic conditions. During this process, metal products are joined together using high heat and pressure. The result is a strong welded joint with a smooth surface.

This type of welding is used to connect similar products and thin parts. Despite the fact that this method has been used for a long time in various areas of production, it is necessary to study its important features and characteristics.

Advantages and disadvantages

Welding stainless steel and other metals using resistance welding is a popular technology. It is used in various areas of industry, and its prevalence is explained by a number of advantages:

1. Using this welding method ensures high speed. Compared to other welding methods, contact technology creates a strong seam quite quickly.
2. One weld spot can be created in 0.1 seconds. If you perform simple calculations, you will find out that a professional welder will be able to make up to 600 connections in 1 minute.
3. To perform the resistance welding process, you do not need to use electrodes, filler wire, fluxes or other consumables. This allows you to significantly save money.
4. The deformation of the metal is not large. It is observed only in places of points.
5. The contact welding process is quite simple; even beginners and intermediately qualified specialists can handle it.
6. Contact electrodes wear out over a long period of time and have a long service life.
7. When carrying out welding work, the risk of fire is very minimal, for this reason this method is considered the safest.
8. Contact technology has no harmful effects on human health and the environment. That's why it is called environmentally friendly.

But there are still some disadvantages that must be taken into account when carrying out contact welding:

• Welding requires expensive equipment that not everyone can afford;
• It is worth considering that the effect of current during resistance welding should be high - from 1000 Amperes. This means that power from power plants or other sources of electricity must be powerful;
• seams made using the contact method are not as tight as, for example, connections made using technologies using electrodes;
• When carrying out resistance welding, the welder must carefully monitor the voltage in the welding area; it should not be excessive.

Operating principle of the equipment

Various devices can be used to carry out resistance welding. Depending on the conditions, the equipment can be suspended, stationary or portable. Often devices have a narrow specialization, but there are universal devices on sale.

Resistance welding of stainless steel and other types of metal requires the welder to have certain training and special skills, which is why it is often used in production. Electric welding is especially popular, but manual methods are used much less frequently; these devices are usually found in auto repair shops and construction sites.

It is worth noting! Every welder must know what kind of electric current is used in resistance welding. As stated above, it should not be less than 1000 Amperes, preferably more. This indicator ensures high speed and productivity of the welding process.

The resistance welding device consists of the following important components:

1. Mechanical elements. In addition to electrodes, they include components for compressing the welded parts and rollers. On stationary devices, hydraulics are used to create the required pressure and roll metal blanks.
2. The electrical part is based on a welding type transformer. It also includes circuit breakers and other necessary components that supply current to the welded area, creating the required voltage in AC or DC mode.
3. Complex equipment contains a lot of electronics, which allows the use of different modes of contact technology. It can also be used to regulate resistance welding current and other important operations.

Types of resistance welding

Types of resistance welding have characteristic distinctive features that must be taken into account when carrying out any of the methods. They can affect the quality and appearance of the weld.

Spot

When considering resistance welding methods, special attention should be paid to the spot method. During its implementation, welding can be carried out at one or several points of the metal surface.

The strength and quality of the connection depends on several factors:

• shape and size of the electrode used;
• current indicator;
• pressure force;
• duration of the work process;
• degree of cleanliness of the surface of a metal part.

Modern welding equipment has high power and speed. They are capable of producing up to 600 welded joints per minute. It is for this reason that this technology is used for welding electronic parts, body components of cars, aircraft, and agricultural machinery. In addition, this method has found application in many other industrial areas.

Embossed

Resistance relief welding is similar in operating principle to spot technology. But there is a characteristic difference - the welded joint and the electrode have a similar relief shape. The relief is given by the natural shape of the part; it can also be achieved through the use of special stampings.

This technology is used in almost all areas of industry. It can also be used as a supplement for welding relief parts. This method is often used to attach brackets and support parts to flat-shaped workpieces.

Suture

Seam resistance welding of stainless steel or multi-point technology creates several joints that are located closely or overlapping, forming a single monolithic joint. If there is an overlap between the points, then the seam is strong and airtight. If the points are close to each other, then the connection is not airtight.

This method is rarely used in industry. Typically an overlapping, sealed seam is used. It is used to create tanks, barrels, cylinders and other similar containers.

Butt

During this technology, when connecting, the parts are pressed tightly against each other. Afterwards, the entire contact plane is melted. This method has subtypes that are selected depending on the type, thickness of the metal, as well as the required quality of the connection.

Important! The simplest method is flash welding; it is intended for products made of low-melting metal with a small contact patch area. The technology with reflow and melting with heating is suitable for stronger metal elements with a huge cross-section.

Welding process

Contact welding has important features and nuances that must be observed during the process. But as practice shows, in order to perform this method it is not necessary to have a large method; even beginners can cope with the technology.

But still, in this matter you will need knowledge of the welding technology algorithm:

1. At the initial stage, welded surfaces must be cleaned and thoroughly processed. This is necessary to obtain a strong and high-quality connection.
2. When welding, the electrical voltage on the surface of the parts must be the same. To do this, the surfaces are leveled as much as possible. They are processed mechanically, using etching, stripping, straightening or degreasing agents.
3. Afterwards the parts should be pressed tightly. This can be done using mechanisms or manually, but in this case the quality of the connection will not be as good due to insufficient pressure.
4. Then, using equipment, current is applied to the surface of the parts. The welder must know what kind of current is used in resistance welding if he wants to get a durable and high-quality seam.
5. The released thermal energy from the electric current melts the desired area of ​​the metal. It forms a liquid core in which bonds between surfaces arise.
6. The pressure applied to the metal prevents the liquid metal from flowing outside the working area.
7. After the current supply is stopped, the liquid core quickly cools down. It forms a high-quality welded joint. The seam is strong, smooth and wear-resistant.

Designation on drawings

Sometimes a drawing or resistance welding diagram may be required to carry out the technology. It must have the correct designations of the parameters and important criteria of this method. Below is a photo with a diagram of this technology.

The welder should take note of several important symbols:

• in the diagram, the visible seam is marked with a solid line;
• invisible connection - dashed line;
• a visible weld point is indicated by a plus sign - “+”. It is done with basic solid lines;
• the invisible point is not marked in any way.

Welding, which uses contact in the form of electric current and pressure, is a popular technology with which you can create strong and high-quality connections. It is used in many areas of industry, including mechanical engineering and agriculture.

This method is suitable for products made of various metals, steels, stainless steel, it is easy to work with, and it is safe for humans and the environment. But still, before you begin, it is worth knowing in advance what kind of current should be used during contact welding; the quality of the work depends on this.

Interesting video

Source: https://osvarka.com/vidy-i-sposoby-svarki/kontaktnaya-svarka

Resistance welding: types and their characteristics, features, resistance spot welding machine

Resistance welding is a process in which monolithic welds by melting the edges of the elements being welded using an electric current, followed by further deformation by compressive force. This technology is mainly used in heavy industry, where there is a need to maintain a continuous cycle of production of the same type of product, in particular, when connecting series of thin sheets of metal.

The essence of technology

Today, at least one resistance spot welding machine is located in all large enterprises, which is facilitated by the strengths of the technology:

• High productivity - it takes about a second to create a weld spot.
• Stable operation - long-term operation without additional outside interference, while maintaining welding quality.
• Insignificant maintenance costs, because the role of consumables is performed by contact electrodes.
• To work with the device you do not need to have high qualifications.

The work process, at first glance, seems simple, but is made up of a number of sequential procedures that must be completed.

The essence of resistance welding is in two inseparable physical processes - heat and pressure. When current passes through the connecting area, a certain amount of heat will begin to be released, which is aimed at melting the metals.

In order for heat to be released in sufficient quantities, the current strength is at least several thousand amperes, in some cases tens of thousands.

At the same time, a certain pressure is applied to the steel from one or two sides, while simultaneously creating a tight seam without any defects.

If the process is organized correctly, the parts will hardly heat up, since the resistance will be insignificant. As monolithic connections are created, the resistance gradually drops, and with it the current strength. The heated electrodes are cooled with water.

How to prepare the surface

There are numerous technologies that can be used to treat surfaces prior to resistance welding. These include:

• Cleaning from significant contamination;
• Carrying out degreasing;
• Removing oxide films;
• Drying;
• Passaging and neutralization.

The procedure and choice of technology depend on the types of workpieces used.

In general, before welding begins, surfaces should:

• Ensure a low level of resistance between parts and electrodes.
• The elements to be welded must be smooth, with no bulges or depressions.
• Ensure equal resistance along the entire length of the contacts.

Equipment is usually divided into three types:

• motionless;
• Mobile;
• Suspended or universal.

Welding is divided depending on the type of current (capacitor and transformer). Depending on the welding method, there are spot, seam butt and relief.

The resistance spot welding machine is composed of three parts:

1. Electrical system;
2. Mechanical part;
3. Water cooling.

The electrical part is responsible for melting parts, controls work cycles and breaks, and also stores current parameters. The mechanical part is a pneumatic or hydraulic system, supplemented by drives. If there is only a compression drive , then you have a point model, the seam ones have rollers, and the butt ones have a compression and upset system. Water cooling includes a primary and secondary circuit, distribution fittings, hoses, valves and relays.

Electrodes are used not only to close the electrical circuit, but also to remove heat from welded joints, to transfer mechanical loads, and in some cases help to move workpieces.

The dimensions and shape of the electrodes are selected depending on the materials being welded and the type of equipment used. They must withstand temperatures in excess of 600 degrees Celsius at a pressure of 5 kg/2 mm2. That is why the main component is bronze and various additives.

Welding joints must be carefully controlled to prevent defects. All methods of non-destructive testing are acceptable, among which the first place is given to primary inspection. But pressing the elements does not allow for a full inspection, so the products are selected and cuts are made along the seams to identify inaccuracies. If a defect is detected, the batch is sent for processing, and the device itself can be calibrated.

What is resistance welding

Resistance (or electric contact) welding is one of the most common types of welding, most often used for fastening thin metal sheets or small parts of the same type.

With this method, a short-term heating of the surfaces being connected occurs with a high voltage current, and simultaneous pressing of them against each other in the contact zone, resulting in the formation of a weld.

Due to its simplicity, high productivity and low costs for consumables, this method is often used in production.

Operating principle of contact welding machines

The essence of the contact welding method is that the surfaces being bonded are simultaneously heated to a plastic state and subjected to mechanical deformation. Therefore, there are two main blocks in the welding machine:

1. Mechanical, including:

• the electrodes themselves (in spot welding machines they are made in the form of clamping pliers, in seam welding machines - in the form of rollers);
• compression drive;
• rotation drive (for roller electrodes);
• clamping and upset drive (for butt welding).

2. Electric. This block consists of:

• welding power transformer;
• output voltage regulator, which switches the number of turns in the primary winding of the transformer;
• a secondary circuit through which current is supplied to the parts;
• primary circuit breaker to turn the current on and off;
• cycle regulator - a device that sets the sequence of welding operations, their duration, and regulates other necessary parameters.

Auxiliary blocks:

• Pneumohydraulic - contains filters, devices for lubricating moving parts, a system supplying air to the compression drive (fittings, air valves, valves) and a pressure regulation system;
• Water cooling unit of the device.

The principle of operation is that the resistance welding area is compressed or rolled between two copper electrodes, to which a low voltage and high current current is supplied. In some devices, the current can reach tens of thousands of amperes. The voltage in the secondary winding is low, less than 15 V. The compression force between the electrodes varies from a hundredth of a newton to 100 kilonewtons.

The main advantages of this method are:

• speed - processing one point or butt connection takes a fraction of a second;
• economical - no oxygen, shielding gas or additive is required, almost no water and air are consumed, electrodes wear out slowly;
• simplicity - the ability to obtain a strong and reliable seam with a small number of controlled parameters, which even inexperienced welders can do;
• safety – the air is not polluted with harmful smoke, the risk of fire is minimized;
• the ability to easily automate the process and put it on stream.

The disadvantages of this method include:

• expensive equipment;
• the need to use high current (over 1000 A);
• complex technology of multi-point welding or welding several seams at the same time.

In addition, this method is not always suitable for joining surfaces of different metals or alloys, or for metals with low contact resistance (such as copper).

Spot welding

Spot resistance welding is the most popular method, which is used both in production and at home, for joining small parts or metal sheets less than 4-5 mm thick. With this method, the surfaces to be fastened are overlapped slightly, sandwiched between two cone-shaped copper electrodes. The metal softens only directly at the point of contact with the electrodes, forming a weld point whose diameter is several millimeters.

Spot welding is the most popular method

Spot welding can be one-sided or two-sided, and the joint strength of the one-sided method is lower, but it makes it possible to create several welded points at once. Multipoint devices operate on this principle.

There are two modes for processing metal in this way: soft and hard. The soft mode is convenient for joining hardened steel products. With it, an electrical impulse of relatively low current and long duration (from 0.5 seconds to several seconds) is passed through the workpieces. At the same time, heating is smoother and power is lower. This device is convenient to use at home.

Source: https://svarkaprosto.ru/tehnologii/chto-takoe-kontaktnaya-svarka