The Influence Of Welding Current On Resistance Welding Machine
The Influence of Welding Current on Resistance Welding Machine
Contact resistance exists in a short time, generally exists in the initial welding, formed by two reasons:
1) the workpiece and the electrode surface with high resistance coefficient of oxide or dirt layer, the current will be a greater obstruction. Resistance Welding Machine Too thick oxide and dirt layer can even make the current can not turn on.
2) in the surface is very clean conditions, due to the surface of the micro-roughness, so that the workpiece can only be in the rough surface of the local contact points. Forming a current line at the point of contact. The resistance at the contact is increased due to the reduction of the current path.
The resistance between the electrode and the workpiece Rew compared to Rc and Rw, because the copper alloy resistivity and hardness is generally lower than the workpiece, so small, the impact of the formation of nuggets smaller, Resistance Welding Machine we less consider its impact.
2. Resistance welding machine welding current
The effect of current on heat production is greater than both resistance and time. Therefore, in the welding process, it is a must control the parameters. The main reason for the current change is the voltage fluctuation of the grid and the secondary circuit impedance change of the AC welding machine. Resistance Welding Machine Impedance changes are due to changes in the geometry of the circuit or the introduction of different amounts of magnetic metal in the secondary circuit. For DC welding machine, secondary circuit impedance changes, no significant impact on the current.
3. Effect of welding time
In order to ensure the nugget size and solder joint strength, precision welding welding time and welding current in a certain range can complement each other. In order to obtain a certain strength of the solder joints, you can use high current and short time (strong conditions, also known as hard specification), can also be used in small current and long time (weak conditions, also known as soft specifications). The choice of hard or soft specifications depends on the performance of the metal, the thickness and the power of the welder used. For the different performance and thickness of the metal required current and time, there is a upper and lower limits, when used as the standard.
4. Effect of electrode pressure
The electrode pressure of the resistance welding machine has a significant effect on the total resistance R between the two electrodes. As the electrode pressure increases, the R is significantly reduced, and the increase in the welding current is not significant and can not affect the production Heat reduction. Therefore, the solder joint strength always decreases as the welding pressure increases. The solution is to increase the welding pressure at the same time, increase the welding current.
5. Effect of electrode shape and material properties
Since the contact area of the electrode determines the current density, the resistivity and thermal conductivity of the electrode material are related to the generation and dissipation of heat. Therefore, Resistance Welding Machine the shape and material of the electrode have a significant effect on the formation of the nugget. As the electrode tip deforms and wears, the contact area increases and the solder joint strength decreases.
6. Effect of workpiece surface condition
The surface of the workpiece oxide, dirt, oil and other impurities increase the contact resistance. Too thick oxide layer can even make the current can not pass. Local conduction, due to excessive current density, will produce splash and surface burns. The presence of the oxide layer also affects the unevenness of the heating of the individual solder joints, causing the welding quality to fluctuate. So thoroughly clean the surface of the workpiece is to ensure access to high-quality joints of the necessary conditions.