The lithium battery spot welding machine has a seat because of its strong welding. The spot welding machine adopts the principle of double-sided and double-point over-current welding. When working, two electrodes pressurize the workpiece to form a certain contact resistance under the pressure of two electrodes. When welding current flows from one electrode to another, the two contact resistance points form instantaneous hot fusion, and the welding current instantaneously flows from the other electrode. The inner structure of the welded workpiece is not damaged by the circuit formed by flowing along the two workpieces to this electrode.
Introduction to machinery
Spot welding machine can be divided into universal type (general type) and special type according to its use, single point type, double point type and multi-point type according to the number of welding points at the same time, single side type and double side type according to the conductive mode, and pedal type, motor-cam type, pneumatic type, hydraulic type and compound type (pneumatic-hydraulic type) according to the transmission mode of pressure mechanism。 According to the installation method, there are fixed, mobile or portable (suspended); according to the moving direction of the active electrodes (usually the upper electrodes), there are vertical (linear motion of the electrodes) and arc travel; according to the mode of power supply, there are power frequency welding machines (using 50 Hz AC power supply) and pulse welding machines。 (DC pulse welding machine, energy storage welding machine, etc。), frequency conversion welding machine (such as low frequency welding machine)。
When the workpiece and the electrode are fixed, the resistance of the workpiece depends on its resistivity. Therefore, the resistivity is an important performance of the welded material. Metals with high resistivity have poor electrical conductivity (such as stainless steel) and metals with low resistivity have good electrical conductivity (such as aluminium alloy). Therefore, spot welding of stainless steel is easy to produce heat and difficult to dissipate heat, while spot welding of aluminium alloy is difficult to produce heat and easy to dissipate heat. In spot welding, the former can use a small current (thousands of amperes), while the latter must use a large current (tens of thousands amperes). Resistivity depends not only on the type of metal, but also on the state of heat treatment, processing mode and temperature of metal.
In order to ensure nugget size and weld strength, welding time and welding current can complement each other in a certain range. In order to obtain a certain strength of solder joints, high current and short time (strong condition, also known as hard specification) can be used, but also small current and long time (weak condition, also known as soft specification). The choice of hard or soft specifications depends on the performance, thickness of the metal and the power of the welding machine used. There is a upper and lower limit for the current and time required for metals with different properties and thickness, which shall prevail when used.
The total resistance R between the two electrodes is obviously affected by the electrode pressure. With the increase of the electrode pressure, R decreases significantly, but the increase of welding current is not significant, which can not affect the heat production reduction caused by the decrease of R. Therefore, the strength of solder joint always decreases with the increase of welding pressure. The solution is to increase the welding current while increasing the welding pressure.
Because the contact area of the electrode determines the current density, and the resistivity and thermal conductivity of the electrode material are related to the generation and loss of heat, the shape and material of the electrode have a significant influence on the formation of the nugget. With the deformation and wear of the electrode end, the contact area increases and the strength of the solder joint decreases.
Spot welding machine adopts the principle of double-sided and double-point over-current welding。 When two electrodes press the workpiece, the two metal layers form a certain contact resistance under the pressure of two electrodes。 When the welding current flows from one electrode to another, the two contact resistance points form a instantaneous hot fusion, and the welding current flows from the other electrode to the two electrodes to form a circuit instantaneously, without harming the welded worker。 The internal structure of the parts。
The process of spot welding is to turn on cooling water; clean the surface of welded parts, assemble accurately, put pressure between the upper and lower electrodes to make them contact well; electrify to heat the contact surface of two workpieces, melt locally, and form a nugget; maintain pressure after power failure, make nugget cool and solidify under pressure to form a solder joint; remove pressure and take out the workpiece. The welding parameters such as welding current, electrode pressure, electrification time and electrode working surface size have great influence on the welding quality.
Spot welding machine uses high temperature arc generated by short circuit between positive and negative poles to melt solder and soldered material on electrodes to achieve the purpose of combining them. The structure of the welding machine is very simple. To put it plainly, it is a high-power transformer, which converts 220V AC into a low voltage and high current power source, either DC or AC. Welded transformer has its own characteristics, that is, the voltage drops sharply.
In addition to the 220/380 one-time voltage conversion, the secondary coil also has tap voltage conversion。 At the same time, an adjustable iron core is used to adjust the working voltage of the welding machine。 Welding machine is generally a high-power transformer, which is made of the principle of inductance。 When the inductance is switched on and off, great voltage changes will occur。 The high voltage arc produced by the short circuit between the positive and negative poles is used to melt the solder on the electrode。 To achieve the purpose of combining them。
Spot welding is a method of resistance welding in which the weldments are assembled and pressed between the two electrodes, and the base metal is melted by resistance heat to form a welding joint. Spot welding is mostly used for the connection of thin plates, such as aircraft skin, aeroengine smoke canister, automobile cab housing, etc. Welding transformer of spot welding machine is spot welding electrical apparatus, its secondary circuit has only one loop. The upper and lower electrodes and the electrode arm are used for conducting welding current and transmitting power. Cooling water passes through transformers, electrodes and other parts, so as to avoid heating and welding, cooling water should be connected first, and then power switch should be connected. The quality of electrodes directly affects the welding process, welding quality and productivity. Electrode materials are usually made of copper, cadmium bronze, chromium bronze, etc. The shapes of the electrodes are various, which are mainly determined by the shape of the welding parts. When installing the electrodes, attention should be paid to keeping the surface of the upper and lower electrodes parallel; the surface of the electrodes should be kept clean, and the surface of the electrodes should be trimmed with sand cloth or file.
The welding cycle of spot welding and convex welding consists of four basic stages (spot welding process):
(1) Pre-pressing stage - the electrode drops to the current connection stage to ensure that the electrode tightens the workpiece, so that there is appropriate pressure between the workpieces.
(2) Welding time - welding current passes through the workpiece and produces heat to form a nugget。
(3) Maintenance time - cut off the welding current, and maintain the electrode pressure until the nugget solidifies to a sufficient strength.
(4) Rest time - the electrodes begin to lift up and the electrodes begin to drop again, starting the next welding cycle。 In order to improve the performance of welded joints, it is sometimes necessary to add one or more of the following items to the basic cycle:
(1) Increase the pre-pressure to eliminate the gap between thick workpieces and make them close to each other.
(2) Preheating pulse is used to improve the plasticity of metal, which makes the workpiece easy to adhere tightly and prevent spattering。 In protruding welding, it can make multiple bumps contact with the plate uniformly before electrified welding, so as to ensure the consistency of heating at all points。