About welding procedure have heard even the children.However, not everyone knows that there are many types of welding processes with different energy sources, without which it is impossible to do.There is one type of welding used most DIY - spot welding.The quality of a weld joint depends on the experience acquired, which basically consists in maintaining the required duration of the current pulse on the basis of visual observation of the weld point.
- spot welding Spot welding
- Requirements electrodes
- Homemade welder
- Scheme assembly apparatus
- main unit
- electrode design
spot welding spot welding is used in industry and the home.In industry, spot welding is used for welding of steel blanks of different grades, non-ferrous alloys and metals of different thicknesses, profiled pieces (channels, I-beams, angles), and intersecting rods.At home homemade spot welding is indispensable for the
spot welding process consists of several stages.In position aligned mating parts placed between the electrodes and are pressed together.After this part is heated to a state of plasticity and subjected to plastic deformation.
When using automated equipment in an industrial environment frequency welding often reaches 600 points per minute.For spot welding quality at home is recommended to maintain unchanged the rate of movement of the electrode and to ensure a certain amount of pressure and the contact of the parts.
Details heated due to the passage of the welding current as a short pulse duration that is different about - 0.01 to 0.1 seconds, depending on the welding conditions.Such pulses are responsible for the molten metal in the scope of the electrodes and forming a common liquid core parts, whose diameter is 4 - 12 mm.
After the current pulse ceases the action items, the items will be held for some time, been able to cool the molten core and crystallize.Like all processes, the technology of spot welding is characterized by advantages and disadvantages.
To her advantages include mechanical strength of spot welds and high efficiency, as well as the ability to automate the welding work.A significant drawback is the inability to ensure the integrity of the weld.
Heating time varies from thousandths of up to several tens of seconds, depending on the power of the machine and welding conditions.When welding of steel products, which are prone to hardening and cracking, for example, carbon steel, it is recommended to increase the heating time subsequent to slow cooling of the metal.
welding of austenitic stainless steel is recommended to the contrary, a short duration of heating.It accepted to do to prevent the risk of heating the outer surface of the connection points to certain temperatures of structural transformations that entails a violation of anti-corrosion properties of the outer layer metal.
certain pressure between the electrodes ensures reliable contact details in the joints.Meaning the pressure depends on the kind and thickness of the base metal parts to be connected.The pressure level after heating is important, because its value is responsible for the fine-grained structure in the weld metal, and the strength of the connection points becomes identical to the strength of the base metal.
With clamp parts during the passage of the welding pulse can ensure the formation around the molten core of the sealing girdle which prevents splash of molten material from the welded area.To improve the crystallization of the molten metal, it is advisable to decompress the electrodes with a slight delay after the pulse went welding.
electrodes electrodes which are used for spot welding with their hands, should ensure strength in the range of operating temperatures, high thermal and electrical conductivity, and ease of machining.
correspond to similar requirements of special bronze with the inclusion of cadmium and cobalt, cold electrolytic copper, copper alloys with chromium and tungsten-based alloys.
Copper values for electrical and thermal conductivity is much greater than the bronze and its alloys, but in terms of wear resistance worse in 5 - 7 times.Therefore, for the manufacture of electrodes serves as the best alloy alloy type EV, which it represents almost pure copper, which is present in the composition of about 0.7% chromium and nearly 0.4% zinc.
To reduce the wear of the electrodes, which are used for spot welding, it is recommended to practice their intensive cooling with water.Quality manual spot welding depends on the choice of the diameter of the electrodes.The diameter of the connection points must be 2-3 times the thickness of the thinnest element of the connection.
welder spot welding at home you need to make a special apparatus.Homemade svarochniki have very different configurations - from small portable models up enough overall spot welding machines.At home generally accepted to use the desktop version, used for welding of ferrous and nonferrous metals.
Scheme assembly apparatus
bulk circuit assembly unit - small spot welding circuits, which contain the minimum number of required parts.However, devices produced in this manner do not have high capacity, but the two sheets of iron having a thickness of 0.2 millimeters, or metal wires, they can cook.
Before the production apparatus for spot welding is necessary to recall the Joule-Lenz law, when an electric current passes through a wire, the amount of heat that is released in a conductor is directly proportional to the resistance of the conductor, the square of the current and the time during which the current flows through a conductor.This means that if the current was 1000 amps, a poorly executed connection and thin wires will lose more power approximately 10,000 times than with electric current of 10 amperes.Therefore, the quality of the circuit can not be neglected.
basis of all the work of this unit is to create an electrical pulse, boil 2 pieces of metal parts.For this you need a small transformer, connect to the bottom winding the workpiece, and to secondary - electrode.
not connect the transformer powered directly applicable to this special bridge rectifier with thyristors.To create the necessary momentum to the machine need to further set another source, consisting of one more bridge rectifier and transformer.Electric current will be collected in a condenser, which serves as a collector and creator of the pulse.
To load a makeshift spot welding machine, press the button on the handle of the gun "momentum", which is responsible for the opening of the circuit capacitor-resistor that provoke their discharge through the electrode.Watch the video of the spot welding, to understand how it is done correctly.
thyristor in this circuit will act as a cathode, closing bridge rectifier transformer №1.While the capacitor is discharged completely, the thyristor is in an open state.Then release the "impulse" to let go, and the capacitor is charged again.And all will be repeated on the same circuit.
If you need more powerful spot welding machine, you can make it with your own hands with the help of the same parts and assemblies: thyristor semiconductor, welding transformer and timer.However, the need for this more powerful transformer.A certain nodes must have completely different specifications.
easiest to manufacture a welding machine with a fixed AC power indicator current.Workflow Management are controlled by changing the duration of the electric pulse - with time switch or by a switch manually.
main part of any equipment for spot welding is the power transformer, which has a large transformation ratio to help ensure a large welding current.The best way to use this device series production, for example, OSM - 1.
Leave the primary winding of the transformer without changing, remember that it must contain not less than 200 turns.Replace the secondary winding to a more powerful, it is recommended to use a wire PT H - 50 or SEW 2 / 1.9.
also like the transformer you can make a transformer from the microwave oven.Such transformers are characterized by large capacity and accessibility.In addition, the price of spot welding will be low.One transformer of a microwave enough for homemade chiseled welding apparatus that will be welded only steel sheets with a thickness of 1 millimeter.
If you need a more powerful machine, you can use two or more transformer.If there are two identical transformer can merge them into one power source to work with thick metal.Similarly, you can connect and more than two transformers if it allows network.
But remember that too powerful a transformer causes a significant drop in voltage results in a flashing light bulbs, fuses and triggering complaints of neighbors.Therefore, the power of self-made electrical spot welding is usually limited to values that ensure the welding current in the range of 1000-2000 amperes.Lack of current can be compensated by increasing the time of the welding cycle.
electrodes The electrodes made of copper rods used.The thicker the electrode you take, the better.Well, if the diameter of the electrode is not less than the diameter of the wire.For homemade too powerful devices fit on the tip soldering of high power.Periodically, it is recommended to undermine the electrodes, because they lose their shape.Electrodes eventually completely worn down and need replacement.
length of wire that goes from the transformer to the electrode must be minimal.Remember that should be the minimum number of connections, because each connection made a loss of power.At both ends of the cable, it is desirable to put the copper terminals for connection to the electrodes and the installation of the spot welding.
solder lugs to the wire, it is also solder wires.The fact that the point of contact with the times, and perhaps the first run, the oxidation of copper takes place, which leads to an increase in resistance and a large power loss, which is why your machine spot welding can and does stop welding.
Due to the large diameter of the tip of the wire and wire them easy to solder, but this problem can be mitigated through the purchase of tinned soldering tip.Nespayannye connection terminals and the electrodes also create resistance and oxidized, but as the need removable electrodes, then each time when replacing old otpaivat tips and solder the new uncomfortable.Make
lower electrode fixed and isolate it from the mounting bolts and washers cheeks and duct tape.To fix the electrodes in the holder, you can use two screws or brass washers.Holders with electrodes dissolve the spring to its original position.Homemade welder spot welding machine network is connected via a circuit breaker, which is rated at no less than 20 amps.
only controls - switch and lever.Compressive force between the electrodes should be sufficient to provide the contact parts between the electrodes.Remember that the thicker sheets, you weld, the compressive force must be greater.Excessive pressure in improvised devices, you can create a clip - lever and lever-screw.There may be other methods that require different equipment.
switch to be installed in the circuit of the primary winding, since the secondary circuit of a large current is present, and the switch further creates resistance.The switch in the situation of the lever clamping mechanism must be mounted on the arm to be able to put pressure on the lever with one hand and include current.The second hand will stick welded parts.
switched off and the welding current is necessary only at the compressed electrodes, otherwise there is an intense spark, which leads to burning of the electrodes.It is recommended to use a forced cooling apparatus using a fan.If no fan is necessary to constantly monitor the temperature of the transformer, electrodes, conductors and take breaks to prevent overheating.
Thus, today buying a welder - a small problem.In any specialty store, you can find a spot welding apparatus of various capacities from different manufacturers.However, not all devices meet the requirements that are imposed on household masters.And in order to collect their own such a device, it is enough just to ask how to make a spot weld, prepare a diagram of the device, components and parts for the assembly and soldering.