焊接的种类1（Types of welding 1）.doc

焊接的种类1（Types of welding 1） Types of welding Electrode arc welding (I) welding arc An arc is a persistent and intense gas discharge between two electrically charged conductors. 1. arc formation (1) short contact between welding rod and workpiece; In short circuit, the current intensive individual contact point is heated by the resistance thermal Q=I2Rt, and the electric field intensity of the smallest air gap is very high. Results: a small amount of electron escaped. The individual contact points are heated, melted, and even evaporated and vaporized. There are many metals with low ionization potential. (2) raise the electrode to keep the proper distance Under the action of thermal excitation and strong electric field, the negative electrode launches electrons and moves at high speed, hitting the neutral molecules and atoms to excite or ionize them. Results: the gas in the air gap is ionized rapidly. In the process of impact, excitation and the combination of positive and negative charged particles, the energy is converted and light and heat are emitted. 2. arc structure and temperature distribution The arc consists of three parts, that is, the cathode area (usually the white spot on the end of the electrode), the anode region (the thin bright region on the workpiece corresponding to the dissolution cell at the end of the electrode) and the arc column region (the air gap between the two electrodes). 3. Conditions of stable arc combustion (1) a power supply that meets the requirements of the arc welding electrical characteristics (a) when the current is too short, the gap between the gas gap is not enough, the arc resistance is large, and higher arc voltage is required to maintain the required ionization degree. (b) as the current increases, the degree of ionization of the gas increases, the conductivity increases, the arc resistance decreases, and the arc voltage decreases. But to a certain extent, in order to maintain the necessary electric field strength and ensure