Influence of Pressure of Medium Frequency Spot Welding Machine on Welding Quality

In the actual intermediate frequency spot welding machine, adjusting the electrode pressure is one of the key parameters of spot welding. The properties of the workpiece adjust the parameters and pressure. Too large or too small electrode pressure will reduce the load-bearing capacity and dispersion of the solder joints, especially for tensile loads.

When the electrode pressure is too small, the contact resistance increases, the current density is too large, and the heating speed is too fast, resulting in spatter; when the electrode pressure is too large, the contact area of the welding area increases, the contact resistance decreases, and the resistance heat decreases. Defects such as fusion and deselding. When the nugget is cooled and crystallized, proper pressure can avoid defects such as shrinkage cavity and crack. Therefore, on-line monitoring of dynamic electrode pressure is of key significance to ensure the quality of spot welding.

While increasing the electrode pressure, appropriately increase the welding current or welding time to keep the heating of the welding area consistent. At the same time, due to the increase of pressure, the negative influence of welding joint strength caused by welding assembly gap and uneven stiffness can be eliminated. At this time, the solder joint strength is not only consistent, but the stability can also be greatly improved.

The force of the electrode joining the workpiece can be divided into two parts, one part overcomes the elastic deformation of the workpiece, so that the workpiece can contact. The other part is used to press the welding contact surface. The force to overcome the deformation of the workpiece and the pressure on the electrode are related to the thickness of the workpiece. As the thickness of the workpiece increases, the pressure increases at the same time.

If other parameters are consistent, as the electrode pressure increases, the strength of the solder joint will slowly decrease. As the electrode pressure increases, the current density decreases, the heat loss increases, and the heating difficulty of the welding area increases, the welding core size and welding quality will inevitably decrease.

If the welding current is increased while the electrode pressure is increased, or the welding time is moderately extended while the electrode pressure is increased to make the solder joint strength consistent. As the electrode pressure increases, the solder joint strength becomes more and more stable.