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Working Principle of Electric Welding Machines

Release time：2026-03-30

The core function of an electric welding machine is to achieve a strong, durable bond between metals, with its operating principle fundamentally based on the conversion of electrical energy into thermal energy. By leveraging the coordinated operation of its internal core components, the machine converts mains electricity into the energy required for welding and ultimately fuses the metal through the heat generated by the electric arc, thereby completing the joint. The key components include step-down transformers in conventional models, inverters in high-frequency models, welding electrodes, and control circuits for stable process regulation. These components work in a division of labor to ensure that the welding process proceeds in an orderly and controlled manner.

I. Principle of Electrical Energy Conversion (Mains Power → Welding Power Supply)

The mains electricity used in everyday industrial and residential applications is typically high-voltage, low-current AC at 220 V or 380 V. This type of power cannot be used directly for welding—welding requires a stable power source with low voltage (usually 20–80 V) and high current (up to several hundred amperes) to meet the energy demands of metal melting. Welding machines achieve the conversion from mains power to welding power through internal core conversion components, and this conversion is mainly carried out in two main types:

1. Traditional models: These rely on step-down transformers to change the number of coil turns via electromagnetic induction, directly converting mains power into low-voltage, high-current AC. They feature a simple structure and low cost, making them suitable for basic welding applications.

2. High-frequency inverter models: The conversion process is more complex. First, the utility power is rectified and filtered into DC, then inverted by power switching devices such as IGBTs into medium-frequency AC. After step-down transformation and secondary rectification and filtering, a stable DC welding power supply is obtained. Compared with traditional models, inverter models offer advantages such as lower energy consumption, superior welding performance, and a compact footprint, making them widely used in precision welding applications.

II. Principle of Arc Generation (the Core Process in Welding)

The core of welding operations is the generation of a high-temperature electric arc, which is essential for melting the metal. The arc-generation process consists of two steps:

1. Short-circuit heating: The two poles of the electric welding machine—one connected to the electrode/wire and the other to the workpiece to be welded—first come into contact, creating a short circuit. The contact point generates high temperatures due to resistive heating (according to Joule’s law, Q = I²Rt), causing the metal at the contact site to melt rapidly and form metal vapor.

2. Arc Formation: Subsequently, the two electrodes are rapidly separated, creating a strong electric field between them. This intense electric field ionizes the surrounding air, ultimately resulting in the formation of a high-temperature arc. The arc consists of three distinct regions: the cathode zone, the anode zone, and the arc column. The central temperature of the arc can reach 3,000°C to 8,000°C, with the highest temperature occurring at the center of the arc column. This extreme heat rapidly melts the joint surfaces of the workpieces to be welded while simultaneously melting the electrode or welding wire, thereby forming a molten pool that accommodates the liquid metal.

III. Weld Formation and the Welding Completion Process

Once a high-temperature electric arc is established and a molten pool forms, the welding operation enters the weld bead formation stage, with the entire process unfolding as follows:

1. Protection and Metallurgical Reactions: When using coated electrodes, the coating melts and decomposes simultaneously, generating protective gas and slag. These protective gas and slag effectively shield the molten metal from atmospheric oxidation, while also optimizing the chemical composition and appearance quality of the weld.

2. Molten Pool Extension and Cooling: The operator holds the electrode or welding wire and guides the arc to move slowly, causing the molten pool to extend gradually as the arc advances. During natural cooling, the liquid metal undergoes metallurgical reactions such as deoxidation and desulfurization with the slag and shielding gas, further optimizing the chemical composition and mechanical properties of the weld.

3. Weld Formation: After the molten metal has completely cooled and solidified, the melted base metal and the electrode/wire metal fuse together to form a tightly bonded weld. The weld strength can approach or even match that of the base metal, thereby firmly joining the two metal pieces and completing the entire welding operation.

IV. Principle of Full-Process Control and Assurance

Throughout the entire welding process, the control circuit of the welding machine operates in real time, with its core function being the regulation of current magnitude. Precise current control ensures stable arc combustion, preventing issues such as arc extinction and excessive spatter, thereby maintaining consistent weld quality and accommodating the welding requirements of metals with varying thicknesses and material types.

Electric welding machine,Mechanical equipment,Mechanical Manufacturing,Machining,Production,Cutting the material

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