Induction equipment for heat treatment of welds and connections of pipelines, pipes, metals (steel, cast iron)

Heat treatment is a process in which metal, or some other material, is placed in a working chamber and undergoes a processing process over a certain period of time. The process itself involves the impact of electromagnetic rays on the metal, which makes it cleaner, eliminating various types of impurities. There are, of course, installations that process metal, but this process can hardly be called heat treatment. Thermal radiation is directed at the material in different ways, depending on which vacuum chamber we are talking about. Vacuum heat treatment equipment plays a huge role in this process, therefore, even before purchasing, you need to take care to purchase a unit that can cope with the tasks that you assign to it.

Equipment for heat treatment of metals

Expanding the topic of heat treatment of metals, one can encounter a number of questions that are of interest to everyone. For example, how long does the heat treatment process take, what conditions are needed for this, what type of vacuum chamber is best suited, and so on. All these points are really important, but you need to understand them yourself in order to delve at least a little deeper into the topic of metalworking.

Now we will look at the types of metals that can be heat treated in vacuum furnaces:

• Lead – metal processing takes a relatively short time, especially if high-quality vacuum thermal equipment is used.
• Cast iron is one of the most difficult metals to melt, which requires equipment at a high or ultra-high vacuum level.
• Stainless steel can be easily processed in various vacuum chambers and furnaces. We just need to create favorable conditions for this process to take place.
• Aluminum is also quite easy to process, but still, it is easier to melt than hardening and other processes.
• Copper is considered one of the most controversial metals, which can show itself differently in different situations.
• Brass – requires the use of stable equipment to heat treat complex metals.
• Steel is one of the simplest materials that can often be heat treated.

All of the above types of metals are amenable to heat treatment in vacuum equipment. It is only important to choose a suitable variation of the stove that could cope with the task that interests you.

Heat treatment equipment

Heat treatment equipment can have various capabilities that facilitate specific processes.
This applies to the maximum temperature created in it, the amount of material processed simultaneously, and the type of processing performed. Equipment for heat treatment at various enterprises is presented:

• shaft furnaces;
• chamber furnaces;
• ovens with a retractable hearth;
• vacuum furnaces;
• melting presses;

Shaft furnaces have high productivity and can process materials of large dimensions. With their help, it is possible to carry out heat treatment for the operation of hardening, annealing, tempering, and normalizing non-ferrous metals. The application is optimal for enterprises that do not focus on the accuracy of operations.

Today, various enterprises produce shaft furnaces that have electric and gas heating. Installations of this type can be used in endogas, nitrogen, air, vacuum and hydrogen environments. Their main application is the heat treatment of large steel elements. These include steel parts and assemblies, large-sized castings and forgings. In addition, they are normalized and rolled out.

Chamber heat treatment furnaces have smaller dimensions and are therefore used to change the properties of small objects. Installations of this type are popular in various types of production. They can be used either separately or in conjunction with automated systems.

The set of equipment for heat treatment may include:

• heating furnaces;
• hardening tank;
• washing chambers;
• vacation cameras;

Tempering chambers in some installations are combined with a cooling container to avoid temper brittleness. Chambers are often used in which the elements are treated with cold, this helps reduce retained austenite. The automated complex may include a rail transport system for loading and unloading.

Furnaces with a retractable hem are the optimal tool for heat treatment of parts or assemblies that have large dimensions. To carry out loading and unloading, cranes and overhead cranes are used. Among the disadvantages, large heat loss can be eliminated. This is due to their size. They are used to perform austenitization and annealing. Often used to heat metal before the forging procedure. Small manipulators and robots can be used to load items. The workspace can be heated by gas or electricity.

Features of thermal equipment

All heat treatment equipment can be divided into two large groups:

1. Main group. It includes equipment that serves for direct heating or cooling. These are all kinds of heating furnaces, various chambers and similar devices;
2. Additional group of equipment. This group includes various units that use the energy of the units of the main group, and devices that ensure the operation of the main mechanisms.

In large thermal shops, many heat treatment units are installed. This heat treatment equipment includes :

1. Heating furnaces;
2. Various firing devices;
3. Equipment for primary cleaning and adjustment of processed parts;
4. Various sensors and various devices that serve to check the quality of finished products.

Furnaces that are used for heat treatment are divided into continuous units and intermittent furnaces. Furnaces can be used for annealing, hardening, tempering, carburizing and so on. Furnaces are divided into types depending on the type of fuel used. As a rule, gas or electric furnaces are used in production, but there is equipment that runs on various types of liquid fuel.

You can buy a wide range of heat treatment equipment in Moscow. Our company’s specialists will select the optimal equipment for heat treatment in accordance with the characteristics of your enterprise.

Weld processing - overview of methods

Welds are responsible for the integrity of the metal structure. In particular, the connection must be strong enough, resistant to rust and moisture. Weld seam processing is designed to ensure the fulfillment of these tasks.

Processing methods

There are three methods by which welded joints are protected:

1. Heat treatment. Thanks to this method, it is possible to remove residual stresses in the material resulting from welding work. Heat treatment is carried out using one of two technologies: local, when only the connection itself is heated or cooled, or general - the entire part is subject to temperature treatment.
2. Mechanical restoration. In this case, the task is to remove slag residues and check the reliability of the connection. A typical example of machining is tapping a seam with a hammer or sanding it. If the slag is not removed, corrosion may develop.
3. Chemical treatment. Applying protective coatings to joints is one of the ways to combat corrosion processes. The most affordable option for chemical protection is treating the seam with a primer paint and varnish material.

Heat treatment

In addition to reducing residual stresses in the metal, heat treatment allows you to achieve the following goals:

• make the structure of the seam and heat-affected zones more adapted to external factors;
• optimize the physical and operational properties of the material, in particular, increase rust resistance, heat resistance, etc.

Heat treatment of welded joints involves heating the welded joint or the entire metal to a given temperature for a certain time. Next comes artificial cooling, which is also carried out according to a certain scenario.

Heat treatment equipment

Four types of technological equipment can be used for heat treatment of joints:

1. Induction devices. Induction heating is often used during pipeline installation. The essence of this method is the use of copper inductors, including multi-core air-cooled copper cable. When installing the inductor on the pipeline, the distance between the pipe and the inductor must be taken into account. The general rule is: the larger the gap between objects, the worse the equipment's power is used.
2. Flexible resistance heaters. This method is considered one of the most convenient and affordable methods for processing welds.
3. Muffle furnaces. When working with this type of equipment, special attention must be paid to the uniform heating of the connection, which is achieved by non-centered installation of the part in the furnace.
4. Heating using gas-flame equipment. When using gas flame heating, welding and special multi-flame gas burners are used. Gas heaters produce thermal energy resulting from the combustion of a mixture of combustible gas and oxygen.

Heating equipment is selected based on installation conditions, availability of a particular type of device and other circumstances. Heating equipment must meet certain requirements: be clearly connected to the welds, not have too much mass, and ensure uniform heating of the joint both in width and length.

To reduce heat loss, all kinds of heat insulators are used when heat treating welded joints.

Thermal insulation must be heat-resistant with low thermal conductivity, durable, but at the same time flexible, wear-resistant and safe to use.

Heat treatment methods

Several methods of heat treatment of welded joints are known:

1. Preheating. It is used both before welding and during welding of parts. This type of heat treatment is used when welding structures made of low-carbon steel. The metal warms up to 150-200 degrees Celsius.
2. High holiday. The technique consists of heating the material to 650-750 degrees Celsius (the specific temperature depends on the type of steel). The temperature is maintained for 5 hours. The technology makes it possible to reduce stress by 80%, as well as increase the material’s resistance to mechanical stress and increase its elasticity.
3. Normalization. Applicable to carbon and low-alloy steel grades. Such heat treatment of the compound is carried out at temperatures from 950 degrees Celsius. At the end of heating, exposure and cooling are carried out under ambient conditions. Normalization makes it possible to reduce the grain size of the metal, reduce stress, and also increases the strength of the weld.
4. Austenization. It is the hardening of a welded joint by heating it to a temperature of 1070 degrees and above. The part is heated for 60 minutes, and then rapid artificial cooling is performed. The technique is widely used for hardening austenitic steels. The result of austenitization is increased elasticity of the welded joint.
5. Stabilization. Stabilizing annealing differs from austenitization by a lower temperature and a shorter period of holding the metal.
6. Thermal rest. The technology consists of heating the weld to 250-300 degrees Celsius. Then the metal is kept in a heated state. As a result of the procedure, the level of diffuse hydrogen in the welded joint is reduced and internal stresses are reduced.

The choice of the method by which heat treatment of welded joints will be carried out depends on the physical and chemical characteristics of the steel (determined by its grade). Fulfillment of technological requirements is of particular importance, otherwise the quality of the welded joint will deteriorate.

Key parameters to consider when performing local heat treatment:

• width of the heated area;
• uniform heating across the wall thickness and width of the heated area;
• holding period;
• cooling intensity.

Mechanical restoration

Mechanical elimination of welding defects is carried out using a wire brush. You can greatly simplify the task and improve the quality of sanding if you use a portable sander or an angle grinder with a flap attachment. Instead of a nozzle, you can also use an abrasive wheel.

Mechanical cleaning allows you to remove the following weld defects:

• scale;
• burrs;
• oxides;
• consequences of discoloration.

Despite the simplicity and low cost of the technology, there are a number of nuances regarding the choice of nozzle, knowledge of which will allow you to perform the job better:

1. First of all, you need to choose a grinding wheel from a suitable material. Aluminum zirconate circle is best suited for mechanical cleaning. The advantage of this material is that, firstly, it provokes corrosion processes, and secondly, aluminum zirconate is stronger than aluminum oxide, from which some types of nozzles are also made.
2. The blades of the grinding wheel should be on the fabric component. The fabric is more reliable and more resistant to heavy loads compared to paper, which is sometimes used on petals as a base. However, such attachments cost much more than their paper-based counterparts. The higher cost of fabric attachments is completely justified and will pay off for work that is aggressive towards the material, such as sanding seams.
3. The size of the abrasive grain depends on the type of work being performed. Very often, when cleaning joints, nozzles with different grain sizes may be needed. Therefore, it is recommended to purchase several types of attachments at once.
4. If you need to properly clean a seam, then different grain sizes are simply necessary, since grinding is carried out with a gradual change of attachments to smaller grain sizes. For example, large scales are removed with coarse-grained nozzles, but fine grinding is done with fine-grained nozzles. Finishing penetration is carried out with the finest grains. Nozzles should be changed sequentially - no more than one size may be missed. However, when it comes to creating a mirror-like shine on a welded joint, no size can be skipped.
5. To process seams located in hard-to-reach places (cavities, edges, holes), special devices are used - burrs installed in a grinding machine. Burrs come in a wide variety of sizes and shapes, so choosing the right configuration is easy.

Equipment for heat treatment of welds and connections of pipelines, pipes, metals

Induction heat treatment of welded joints and seams of steel, most often pipes or pipelines, is an innovative post-welding procedure. This technology is widely used in a variety of fields: oil refining, energy, chemical.

Induction heat treatment of pipes and pipelines can be either local, when it directly concerns the weld or joint, or complete, when the entire structure, including joints, is heated. Regardless of the scale of the operation, there are three main stages of weld heat treatment: first, heating occurs to the desired temperature at a certain speed, then the welded joint is held for some time, and finally, cooling, which also takes place at a predetermined speed.

Induction equipment for heat treatment of metal and welds from the PROMINDUKTOR company is completely air-cooled, has an easy control interface, and a built-in industrial controller with the ability to program heat treatment modes:

1. Preheat

– a simple method of heating a material to a certain temperature and maintaining this temperature for some time;

2. Annealing

Vacuum pumps

Vacuum pumps are technical equipment designed to pump out gases and vapors from a confined space and form a vacuum environment in it. The principle of operation is to remove gases, steam, air from the working chamber.

Our company produces vacuum equipment and special-purpose equipment; batch resistance furnaces (shaft and chamber); continuous resistance furnaces (conveyor and pusher); thermal diffusion and thermocompression installations.

Thermal equipment is used in metallurgy, mechanical engineering, the defense industry, mining and other industries.

SPECIFICATIONS

Vacuum ovens

Vacuum furnaces are the optimal means to produce high-quality tools, high-speed steels, titanium alloys, copper, refractory metals and structural steels. Vacuum furnaces carry out all processes with high technological precision parameters. The temperature in them cannot deviate by more than 5 degrees. They are used as components of heat treatment lines.

Vacuum furnaces can use nitrogen, helium, or air. Moreover, their operation does not require the use of water quenching tanks. This makes it difficult to harden low-carbon and low-alloy steels in them. To make the inner surface of a vacuum furnace, molybdenum sheets are used, heating elements are graphite, ceramics, and powder materials.

Installations that have high power are capable of creating a pressure in a vacuum furnace of 0.00005 mbar. The maximum ambient pressure level will be 20 mbar and the temperature will be 1350 degrees. Water is used as a coolant.

Vacuum chambers are equipped with various vacuum pumps, receivers with a gas cooling medium and installations that provide reverse water cooling. The degree of automation of this heat treatment equipment can vary between 0.7-0.9.

Vacuum furnaces are expensive because they require much more money to develop and manufacture. However, they have one drawback, which is due to the fact that the surface of the alloys is dealloyed if high temperatures are used in them.

Industrial and hydrogen furnaces

Another popular type of heat treatment oven is the industrial oven. These units, as a rule, have large dimensions and are designed for heat treatment of large volumes of materials. Industrial furnaces can run on electricity or gas, and sometimes there are models that run on different types of liquid fuel. When installing industrial furnaces in production, you need to calculate all possible costs for devices that will ensure uninterrupted operation of industrial equipment.

Energy costs are a very important factor when purchasing heat treatment equipment. If you purchase too powerful equipment that will not be 100% fully loaded, you can completely lose your profit, since it will all be spent on paying for electricity or another type of fuel.

Enterprises that engage in metal smelting and heat treatment often use hydrogen vacuum furnaces. Their main difference is the supply of hydrogen to the working area. Hydrogen supply helps achieve higher quality of heat treated parts. In order to save money, some enterprises use dissociated ammonia, which costs a little less. Although this appears to be more cost effective, when using ammonia the treatment efficiency drops by approximately 10% compared to using hydrogen.

Hydrogen vacuum furnaces are capable of processing a large number of products in a minimum time. Most often, they operate in continuous mode.

Basic set UINT-50-2.4

The questionnaire can be downloaded here

Equipment used

The following types of equipment are used for heat treatment of welds:

1. Induction. The operating principle is based on heating the metal by eddy currents created by an induction coil (inductor) connected to a high-frequency generator. The heated area is preliminarily covered with asbestos. On top of it, coil turns are wound with a flexible wire in increments of 2.5 cm at a distance of 25 cm on both sides of the joint. Pads with wires located inside are also used as an inductor. The technology ensures fast, uniform heating of the joint area, regardless of the position of the parts.
2. Radiation. Heating is carried out by heat from nichrome wires through which electric current passes. Flexible heating elements are convenient for processing complex shaped joints. Radiation equipment is more effective than induction equipment when working with metals with low electromagnetic characteristics.
3. Gas is advantageous for use because it does not require electricity. However, it takes a long time to heat up. Therefore, the equipment is used on small structures. To ensure uniform heating of the joint, the work is performed with two multi-flame acetylene torches simultaneously on both sides.
4. Muffle furnaces are used to work with small parts. They are also used on small diameter pipelines.

Treatment of the weld after welding

Welding is the most reliable, fastest and economical way to create permanent joints of metals and their alloys. During the welding process, the metal is heated to its melting point. This causes internal tension in him. In addition, slag remains on the surface of the weld. To remove slag and relieve internal stresses in the metal, various weld processing methods are used.

Basic methods of processing welded joints

The following weld processing methods have become the most common:

• Thermal. Used to eliminate internal residual stresses. It is carried out by local or general heating.
• Mechanical. Cleaning welds after welding removes slag and scale from the joint surface.
• Chemical. Consists of degreasing and coating with a protective layer. Prevents the formation of corrosion foci. The method is used to process materials susceptible to corrosion that will have to work in active environments.

The method of exposure is chosen based on the technical requirements for the structure and its operating conditions. Often all three methods are used sequentially.

Heat treatment

Heat treatment of welded joints must be carried out after welding thin-walled products that are especially susceptible to deformation under the influence of internal stresses. Such structures include pipelines, various containers, and pressure vessels.

Heat treatment of the weld

Heat treatment is also carried out for most critical structures, such as nuclear and chemical reactor vessels.

Heat treatment consists of heating the part and then cooling it according to a strictly specified temperature schedule.

Why is it needed?

During welding, a small area of ​​the part near the seam is heated. Uneven heating leads to the emergence of internal stresses that can deform or even destroy the part. In addition, in the zone of uneven heating, the structure of the metal crystal lattice changes, which leads to a deterioration in its physical, mechanical and chemical properties.

Near the weld seam there is a hardening zone in which the strength is increased and the elasticity, on the contrary, is decreased. It is surrounded by a zone of softening, in which ductility is preserved, and the strength becomes lower than it was before welding.

Heat treatment of welded joints is intended to restore

What types of heat treatment equipment are there?

There are 4 types of thermal equipment based on the principle of impact on metal:

1. Thermal
   - a metal part is heated by using heat produced by various methods.
2. Thermochemical
   - when a metal is heated, its surface is coated with chemical compounds. Increases strength, wear resistance, reduces susceptibility to corrosion. Performed at high temperatures with prolonged exposure. Solves the problems of carburization, nitriding, chrome plating and others.
3. Thermomechanical
   - when a metal part is heated, it undergoes deformation to impart the necessary properties.
4. Cryogenic
   - the effect on the metal is through extremely low temperatures. Increases wear resistance, reduces the coefficient of friction of parts.

Often, to create the desired metal structure, heat treatment of various types of effects on the metal is carried out. Therefore, units were developed and implemented that perform complex treatment with different types of influence.