Date:2018-01-23 View:274 Tag:Butt Welding
Butt resistance welding (hereinafter referred to as butt) is the entire end face of a resistance welding method in which two workpieces of a thermal resistance are welded together at the same time. High butt productivity, easy to automate, so widely available.
Docking is divided into two types of resistance butt welding and flash butt welding.
Resistive butt-welding is always applied to both workpieces. Resistance heating is used to heat the plastic state and the forging force is quickly applied to the top (with or without upset force to maintain the weld pressure only) to complete the weld. Spot welding, when the contact surface, temperature and pressure, the resistance of the contact resistance depends on the surface conditions. When the contact resistance of significant oxide or other stolen goods, the contact resistance. Increasing the temperature or pressure will increase the effective contact area, thereby reducing the contact resistance. When the welding starts, the current density at the contact point is large, the temperature at the back end is rapidly increased, and the contact resistance drops sharply. Heating to a temperature (600 degrees steel, aluminum 350 degrees), the contact resistance completely disappeared. The spot welding, but also when the resistance welding resistance welding zone. When resistance welding, the contact resistance exists for a short time, the heat generated is less than 10-15% of the total heat. But because some of the heat is generated in a narrow area near the contact surface. As a result, the temperature in this area rapidly increases and the internal resistance rapidly increases. Even if the contact resistance completely disappears, the intensity of the heating area is still higher than elsewhere.
Flash butt welding can be divided into continuous flash butt welding and flash butt welding preheat. Continuous flash butt welding is mainly divided into two phases: phase flash phase and disturbance phase. Preheat the flash butt welding flash phase before the warm-up phase. The main function of the workpiece flash heating. At this stage, the first force, and the contact surface between the two workpieces, forms many points of contact. The current passes through the contact melting point to become the liquid metal connection end face. As the liquid is too high beam current density, so that the liquid metal evaporation beam, beam blasting. With the progress of the power tongs slowly, lintels also continued to produce and blasting. Under the action of electromagnetic force and vapor pressure, the liquid metal particles are ejected from the continuous interface. Sparks form a jet stream. At the end of the flash phase, there is sufficient pressure applied immediately on the top of the workpiece. The lintel is rapidly lowered to stop the blasting and the forging stage is entered. The role is frustrated and the liquid metal sealing gap after the end of the workpiece beam surface beam after the blasting, and liquid metal and oxide inclusions squeeze out the end of clean plastic metal in close contact, and produce some plastic deformation, the joint area to promote the formation of particles together to obtain a Strong common crystallization. Flash butt welding process, although the molten metal heating, but essentially plastic state welding.