The essence of the method.
To the electrode and the workpiece to form and maintain the arc welding power sources from the fed constant or variable welding current. Welding arc (1) is on a metal rod between the electrode (2) and the base metal (3) Under the heat of the arc metal arc electrode coated electrode and the base metal is melted to form a weld pool (4). Drops of liquid metal (5) from the end of the molten core of the electrode are transferred to the bath through the arc gap. Together with the rod melts the electrode surface (6), forming an arc around the gas protection (7) and a liquid slag bath (8). As the movement of the arc, the metal hardens the weld pool, weld is formed (9) and slag crust (10) on the surface of the weld.
The depth to which the base metal is melted, is called the depth of penetration. It depends on the welding conditions (welding current and electrode diameter), the spatial position of welding, the velocity of the arc on the workpiece surface (end face of the electrode and arc reported forward movement in the direction of welding and transverse vibrations), the design of the weld, shape and dimensions of the welded edges etc. Dimensions of the weld pool depends on the mode of welding and are usually in the range: the depth of 7 mm, width 8-15 mm, 10-30 mm. Participation rate of the base metal in the formation of the weld metal is typically 15-35%.
The distance from an active spot on the molten surface of the electrode to the other active arc spots on the surface of the weld pool is called the length of the arc. Melted electrode coating forms around the arc and weld pool on the surface of the gas atmosphere, which is pushing the air out of the fusion, interferes with its interactions with the molten metal. In the gas atmosphere, there are also a couple of the ground and the electrode metal and alloying elements. The slag, covering the electrode metal droplet and the surface of molten metal weld pool, helps protect them from contact with air and is involved in the interactions of metals with molten metal.
The crystallization of the metal weld pool as the distance of the arc leads to the formation of the joint that connects the welded parts. When the random cliffs arc or by changing the crystallization of the metal electrodes weld pool leads to the formation of the crater welding (deeper in the seam, reminiscent of the outer surface of the weld pool). Solidifying the slag formed on the surface of weld slag crust.
Given that the current supply to the electrode holder of the welding current flows through the electrode metal rod, the rod is heated. This heating is greater, the longer the rod the flow of welding current and the larger the magnitude of the latter. Before you start welding a metal rod has a temperature of ambient air, and by the end of the electrode melting temperature rises to 500-600 ° C (when the content in the coating of organic matter - no higher than 250 ° C). This leads to the fact that the rate of melting of the electrode (the amount of molten metal electrode) at the beginning and the end is different. Changes and the depth of penetration of the base metal due to changes in the conditions of heat transfer from the arc to the base metal through the layer of liquid metal in the weld pool. As a result of change in the ratio of shares of the electrode and base metals involved in the formation of the weld metal, and thus the composition and properties of the weld metal, made by one electrode. This - one of the drawbacks of manual arc welding with coated electrodes.
See also:
Manual Arc Welding
Introduction to Arc Welding
Creating and maintaining an arc
Ways to improve performance
Technique of upper and horizontal joints
Technique of the lower seam
Pipe Welding Technique
The Method
Arc Welding in Protective Gases
Electrodes for Manual Arc Welding
No comments:
Post a Comment