Introduction to the History of Cold Welding Machines
Cold welding machines are internationally known as ESD (Electro Spark Deposition). They were developed by Soviet experts using a circuit principle similar to that of an electrical discharge machining (EDM) machine. The primary purpose of cold welding machines is to use high-hardness materials such as tungsten carbide for coating metal surfaces, enhancing their wear resistance, heat resistance, and anti-sticking properties. Initially, the thickness of coatings from these machines could only reach around 30 μm, making them unsuitable for repair purposes. After extensive research and development, their output power was increased, the structure of the welding gun and the composition of the welding rod materials were improved, and rotating electrodes replaced the previous vibrating ones. Additionally, argon gas protection was used to prevent oxidation and nitriding of the deposited metal, enabling continuous multi-layer overlay welding repairs and increasing the repair overlay thickness. This led to the machine being marketed as a metal workpiece repair processing machine. For manufacturers of metal products, when defects such as burrs, pinholes, pores, cracks, wear, or scratches appear on workpieces, traditional welding methods often cause deformation, thermal cracking, or easy detachment, leading to unsatisfactory repair results and direct scrapping, resulting in significant economic costs or delivery delays. However, due to its characteristics of no deformation, no hard spots, no color difference, and strong welds after repair, the cold welding machine has been widely used in the surface defect repair of metal castings and mold wear fields.
Working Principle of Cold Welding Machines:
Cold welding machines achieve repair through micro-electric instantaneous discharge, producing high thermal energy that melts the welding wire onto the damaged part of the workpiece and firmly fuses it with the original base material. After welding, only minimal grinding and polishing is required.
The working principle: The cold welding machine uses a charged capacitor with a cycle of 10–3 to 10–1 seconds and ultra-short discharge times of 10–6 to 10–5 seconds. The discharge time is extremely short compared to the interval before the next discharge, allowing the equipment sufficient relative downtime. Heat dissipates through the basic body of the workpiece into the environment, so there will be no heat accumulation at the processed area of the workpiece. Although the temperature rise of the workpiece remains almost at room temperature, due to instantaneous melting, the tip of the electrode can reach about 10,000 degrees Celsius. Thus, the electrode material transitions in a plasma state as molten metal metallurgically bonds to the surface layer of the workpiece. Due to alloying with the base material, diffusion occurs internally within the workpiece, forming a diffusion layer, thereby achieving a high-strength bond that won't peel off.
Product Advantages:
1. Reasonable design, freely adjustable. Different discharge frequencies can be selected based on different metal materials to achieve the best repair effect.
2. Small heat-affected zone. There is no heat input during the overlaying process, hence no deformation, undercutting, or residual stress. No local annealing occurs, and reheat treatment is unnecessary after repair.
3. Minimal welding impact. This welder overcomes the shock effect on the surrounding areas of the workpiece caused by conventional TIG welding. It can also repair surfaces of parts without extra margin.
4. High repair accuracy: Overlay thickness ranges from a few micrometers to a few millimeters, requiring only grinding and polishing.
5. High fusion strength: Fully penetrating the workpiece's surface material creates a very strong bonding force.
6. Portability: Lightweight (28 kg), powered by 220V electricity, with no specific environmental requirements.
7. Cost-effectiveness: Immediate on-site repairs increase production efficiency and save costs.
8. Multi-functionality: Can perform overlay welding, surface strengthening, etc. By adjusting the discharge power and frequency, the desired overlay and strengthening thickness and smoothness can be achieved.