Spot welding

Spot welding This is a process of joining metals by heating them, passing an electric current through them, and deforming the molten zone with pressure. Heating occurs only at a specific point. This type of joining is classified as pressure welding. The first mention of this method of joining metals dates back to 1877, when it was proposed by the Russian inventor N.N. Benardos.

Spot welding — is also a type of contact welding. In this method, two electrodes, located on opposite sides, conduct an electric current of 1-200 kA. Joining metals this way is very popular. Approximately 30% welds are made this way, and this percentage is currently increasing. Spot welding finds its application in mechanical engineering, aviation industry, and instrument making.

Spot welding technology

Spot welding technology Incorporates the principles of contact welding. The joining process proceeds as follows:

• — welding electrodes are located on both sides of the part;
• - an electric current is passed through them, causing a thermal effect according to the Joule-Lenz law;
• - this thermal effect between the electrodes strongly heats the surface of the metal and melts it;
• — a cast core of a weld spot with a diameter of 4-12 mm is formed, which is strongly compressed mechanically.

This results in a tight connection between the metal surfaces. Spot welding technology The speed of welding can reach 600 joints per minute. Metal thicknesses range from 0.02 µm to 20 mm. This type of welding is used in the electronics industry. A thickness of 20 mm allows for its use in agricultural engineering.

Resistance spot welding technology

Resistance spot welding technology The strength of the connection is determined by the size and structure of the weld spot. This primarily depends on the following factors:

• — the size of the surface of the welding electrode;
• — the strength of the supplied current;
• — flow time through the workpiece;
• — the state of the workpiece surface and the magnitude of the compressive force.

Resistance spot welding technology has different modes of joining metals.

1. Soft mode.

The welding time is slightly longer. Moderate currents gently heat the metal surface with a moderate current, not exceeding 100 A/mm on the work surface.²Current flow typically lasts from 0.5 to 3 seconds. Power consumption in this mode is much lower than in hard mode. Welding machines are less expensive because they don't require a large electrical load. The weld zone isn't subjected to significant hardening, so this mode is suitable for welding steels that are prone to hardening.

2. Strict mode.

In this mode, the welding time is much shorter than in the soft mode. This is facilitated by the higher current used. Its density is 120-300 A/mm.² when welding steel. The pressure of the welding electrodes is 3-8 kg/mm² The current flow rate is typically 0.1-1.5 seconds. Welding machines operating in this mode experience a significant electrical load, resulting in significantly higher power consumption. A significant advantage of this mode is increased productivity and reduced welding time. This method is suitable for joining high-alloy steels, parts of varying thicknesses, and dissimilar workpieces. Metals with high thermal conductivity, such as aluminum and copper, and their alloys, are also excellent welds.

Thus, resistance spot welding technology allows you to join different metals with sufficient strength and speed of welding.