Processes Occurring

December 20, 2018

The state of any substance is characterized by interrelation of atoms and molecules. Are 3 main states: liquid, solid and gaseous. The distance between the molecules in each case will be different. The distance between the molecules in liquid and solid states are too small, this explains the low compressibility of these substances and their common name – 'fused state'. In gases, the distance between molecules is much longer, so they are under the influence External pressure may be relatively easy to contract.

This explains the difference between the electrical conductivity of substances and gases in the condensed state. In liquids and solids extreme electrons are far from the nucleus their atoms, it is easy to lose touch with the core and move freely through the material. These free electrons are called conduction electrons, and are the current carriers in a conductor. In gases, the electrons are attracted only to their nuclei, so that under normal conditions, gases do not conduct current, but in an electric arc gases are ionized and become electric. Welding arc is the discharge of electrical current in a gas located between the powered by liquid or solid electrodes (conductors), which is a concentrated source of heat and is used for melting metal for welding.

Electric charges in the welding arc transferred charged particles – electrons, as well as negatively and positively charged ions. The process by which a gas having positive and negative ions is called ionization, and a gas – ionized. Ignition of the arc welding consumable electrode begins with a short circuit of the electrode with the base metal. Due to the roughness of the electrode surface contact during a short circuit occurs the individual speakers sites that instantly melt under the action of the released heat, forming a fluid jumper between the base metal and the electrode. With the withdrawal of the electrode liquid bridge is stretched, its cross section decreases electrical resistance and temperature rise. When the molten metal bridge reaches boiling point, a pair of metal can be easily ionized and there is an arc. The appearance of the arc takes mere seconds. Doug, burning between the electrode and the workpiece in the air, said to be free. Free arc consists of 3 parts: the cathode with a cathode spot, which is used for emission (output) electrons of the anode with an anode spot, bombarding electron flow and the arc column, which occupies an intermediate position between the anode and cathode zones. Temperature in the arc column during welding reaches six thousand -7000 C depending on the density of the welding current.

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