To create a variety of metal structures, each owner of a suburban area wants to have an apparatus for welding metal. The most popular and reliable method is resistance welding, which is widely in demand in the repair of automotive equipment.
Many are interested in whether there is a technology for the manufacture of resistance welding with their own hands? Yes, at home, many contact bonding methods are the most durable and reliable. It is not difficult to make devices for welding work on your own, while you can use many consumables that have long been considered unnecessary in the household.
Scope of contact welding
The name contact welding indicates that the connection of two parts occurs as a result of the action of an electric current and the application of a sufficiently large compression force to certain points of the material.
Do-it-yourself welding allows you to connect products with a thickness of 0.02 mm to 20 mm. Moreover, the details of the material to be welded can have various properties and profiles. Most often, products are welded from mild and corrosion-resistant steel or brass and light alloys of non-ferrous metals.
Many methods of this type of connection are used exclusively in industrial production for the construction of aircraft, automobiles, ships and other complex equipment. Appliances for resistance welding (made by oneself including) are widely used in the agricultural sector of the national economy. And also not a single car maintenance and repair station can do without contact-type welding equipment.
At home, do-it-yourself contact welding is used to make various metal structures of frame shape, cabinets, dishes and other household utensils.
Connection technology
The contact welding process is carried out by heating the junction of the two parts when an electric current passes through them. Moreover, the current supply occurs simultaneously with the use of strong pressure on the welded surface.
Necessary stages of welding with a contact joint:
- Carrying out preliminary preparatory work for the mechanical cleaning of the surface of the materials being welded.
- Reliable fixation of the workpiece in the welding machine, with particular attention to be paid to the exact alignment of the edges of the welded products.
- The supply of electric current to the contacts of the electrodes.
- The process of molten metal at the junction point.
- Draft of the junction and disconnection of electric current.
The main indicators of do-it-yourself contact welding from a welding machine are:
- The time interval for the passage of electric current.
- The nominal value of the compression force of the welded workpieces.
Based on these indicators, do-it-yourself contact welding can be divided into two operating modes:
- The soft mode is characterized by a long duration of the current period of the current strength, as well as a relatively smooth heating of the junction. The application of this method can significantly reduce power losses, which significantly reduces the cost of do-it-yourself contact spot welding, and also reduces the hardening of the welding zone.
- The hard welding mode is characterized by a short period of action of the current strength with a significant increase. The main advantage of this method is the reduction in the total time of the welding process, therefore, a significant increase in the productivity of the work performed.
Advantages of contact welding
Compared to other methods of joining metal surfaces, do-it-yourself contact welding from a welding machine has a number of significant advantages:
- The equipment manufacturing process requires a minimum expenditure of additional resources, which makes this type of welding economical.
- The junction of two metals, even of a heterogeneous type, is strong, reliable and of high quality. Moreover, the welder does not require high qualifications and extensive experience in conducting work, as the technology of resistance welding with their own hands does not imply the use of a large number of precise equipment settings.
- Significant speed of the process, and therefore high productivity are considered one of the most important advantages of contact joints. So, to complete one joint, it will take only 0.02 seconds, which is much less than another type of welding.
- Environmental safety of the process of resistance welding with their own hands is also an important characteristic of it.
Types of resistance welding
The difference in the order of the welding process and the technological features of supplying electric current to the junction determine the division of contact welding into several different types:
- butt welding;
- point connection;
- suture joining of metals.
Each of these types of welding has its own characteristic features and methods of application.
Butt welding
In butt welding, the contact of the products occurs over the entire surface area, so the joining process is carried out using special machines. Machines have devices capable of holding workpieces and exerting pressure on parts.
Butt welding is carried out in two ways:
- The resistance at which the metal in the weld zone heats up to a plastic state, after which the weld site is precipitated. This method requires a good contact of two surfaces, so a very important condition for high-quality work is the preliminary processing of the butt ends of the product.
- Flash welding consists in the complete melting of the metal in the place of the joined surface. If the action of electric current and the compression force are constant, then continuous welding is performed. But in the case of a periodic change in pressure on the abutting surfaces, intermittent melting of the ends occurs, while the current strength is unchanged.
The use of flash butt welding from a welder in the home is very difficult due to the high cost of equipment.
Resistance spot welding
It is this type of connection that is most often used at home for welding individual parts from sheet metal. The technology of contact welding is based on the action of a heated electrode at the point of contact of two metal surfaces. An ideal application for this type of connection is a do-it-yourself contact welding for batteries.
The quality of the connection of the workpieces significantly depends on the following parameters:
- the size and shape of the electrodes, which has a significant effect on the value of the connection point;
- level of applied compression at the weld point;
- magnitude of electric current;
- quality of preliminary surface cleaning;
- exposure time current.
Spot welding can be carried out both by one-sided heating, in which the effect on the metal occurs only on one side, and by the two-sided method, in which case the part is heated immediately on both sides.
Before you make resistance welding with your own hands, you need to think about which principle of connection is best suited for high-quality performance of the task.
Suture joint
The weld in this type of welding is a series of connection points that overlap each other. As a result of such a technological operation, a tight and durable weld is formed on the surface of the metals.
Seam welding electrodes are special disc rollers that, rotating, provide tight compression of the metal surfaces and heating it at the junction.
Depending on the location of the rotating electrodes, this type of welding can also be one-sided or two-sided.
Of all types of contact welding, the point type of connection is best suited for use in domestic conditions, since it is not difficult to make a contact welding with your own hands from a microwave or use a welding inverter, even for a beginner.
Microwave Spot Welder
Many amateur welders for the manufacture of a welding machine came up with the idea of using a transformer from an old microwave oven that was unnecessary in the household. Therefore, a simple home-made circuit for resistance welding from a microwave was developed, which you can do with your own hands at home.
For these purposes, you need to disassemble the old apparatus by removing the necessary transformer. All other components of this device will not be needed.
The secondary winding of the transformer is not needed, so it will have to be completely dismantled. To make resistance welding from a microwave with your own hands, you need to upgrade the secondary winding of the device.
Transformer upgrade
To make a high-quality welding machine, it is necessary to make a small alteration of the transformer. For this:
- After dismantling the transformer, it is necessary to wind a new secondary winding from the wire with a cross section of at least 16 mm.
- You need to wind two turns in order to exclude an increase in the resistance of the winding.
- After creating the winding and conducting its isolation, you need to measure the voltage (just 2 V is enough).
When making resistance welding from a microwave with your own hands, you must ensure that the current supplied by the device does not exceed 200 A. Otherwise, the use of a more powerful unit can damage the electrical wiring of the home electrical network.
Of course, if there is a factory welding machine in the farm, then it is easy to make contact welding from an inverter with your own hands. You will only have to make your own special clamps for attaching the electrodes, while the length of the wires connecting the current source and the electrodes should be minimal in order to reduce their resistance and heating during operation.
Making a casing and tongs for homemade welding
Like any other technical device, a home-made resistance welding machine should have a practical housing. Very popular for transformer welding is the case from the system unit of a personal computer.
Structurally, the system unit case has a fan for cooling the transformer windings, as well as the required number of ventilation holes. You can make a casing for welding from sheet metal by making an ordinary box that is suitable in size.
You can make pincers for resistance welding with your own hands from a steel profile with a cross section of 20 × 20 mm, which is able to provide sufficient strength. A lever with a length of 50-60 cm allows you to create a compression force of the order of 30 kg, which is enough for a home-made device. Welding electrodes are attached at the ends of the lever.
Resistance welding for batteries
In modern home appliances, batteries are commonly used. In the event of a power supply failure, one or more elements often have to be changed. Replacement of the batteries by soldering is not possible, as the cells are afraid of overheating. Therefore, it is better for these purposes to make contact welding for 18650 batteries with your own hands.
The easiest option to repair the battery at home is to use a car battery. The electrodes can be made of two pieces of copper wire, previously stripping them and securing them with electrical tape. The ends of the electrodes are located in the same plane at a distance of 2-3 mm from each other. The other ends of the electrodes are connected to the terminals of the battery via wires with clamps. When connected, the polarity of the battery terminals does not matter.
When connecting do-it-yourself contact welding for batteries, a short circuit will occur, and the metal at the junction will melt. After cooling, a reliable and durable contact will appear.
Point Connection Defects
If the welding process is violated, some defects may occur at the junction of the two parts. Conventionally, they can be divided into external (visible) and internal (invisible) damage.
External defects include:
- burn through metal;
- surface cracks;
- points of irregular shape;
- darkening of the surface of the points;
- dents.
Internal defects are characterized by the following features:
- cracks inside the weld joint;
- improper heating of the points (poor penetration);
- the appearance of pores and shells.
Visible defects are easily identified by visual inspection of the junction. Internal defects are detected using special quality control devices in the workplace.
There are many methods of contact welding. The use of any of them requires compliance with safety regulations for working with electrical equipment, as well as the protective equipment necessary when performing operations with elevated temperature.