The essence of the process
Welded parts are fixed in the grip electrodes and compressed by axial force F St. (P). The left plate is usually fixed. When you turn a piece of welding transformer electric current flowing through the big power and low voltage, heating them. The greatest amount of heat released at the interface details.
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| Flash butt welding process |
When resistance welding parts initially compress the axial force for the formation of a dense ground welded ends. Then the electric current is applied, which docked with the passage of a surface heated to a plastic state. Further runs of sediment (increasing compression force) pieces to form a compound in the solid phase. In this current is switched off before the end of precipitation.
Resistance welding is used to connect parts of circular or rectangular cross-section area, usually up to 200 mm 2 , depending on the metals. To ensure uniform heating of the ends they have to fit exactly and pre-cleaned by mechanical or chemical means.
Fusion welding can be performed with continuous or intermittent reflow.
For continuous fusion butt welding parts gradually pull together when the power source. Touch the ends are on separate ledges. Since the area generated contacts, jumpers are very small, due to the high density of current flowing through them, they are rapidly heated and melted. Part of the metal in the form of bursts of sparks flying out of joint. In the present disposable melt and impurities from the surfaces of workpieces. Further details of convergence leads to the formation of new contacts and the melting-jumpers. As a result of this continuous process at the ends of a layer of liquid metal. Once the ends melted on the surface, made of sediment. The ends of the rapidly converging with great effort. In this case the liquid metal with oxide films extruded from the joint surface and the solidification forms a burr, which is usually removed in hot form.
To connect the pieces with a large cross-sectional area to reduce the capacity of the equipment is used intermittent fusion butt welding . Details of when the current alternately compress with little effort and re-bred. When compressing the surface of the heated docked flowing current. On opening is formed between the ends of an electrical discharge, fused to the surface. After several repeated actions billet surface covered by a layer of liquid metal, and holds residue. Molten metal is extruded from the joint and the ends are joined to produce a welded joint.
To reduce the consumption of metal pre-heating is carried out at rapprochement with the passage of several parts of the current pulses. After this piece divorce, and implemented and the melting of the sediment.
Fusion welding allows you to connect parts of complex shape with a cross section area of 100 000 mm 2 . Thus, in contrast to resistance welding is not required thorough preliminary preparation of the ends of workpieces. In this way produce a variety of long products (pipes, rails, rebar reinforced concrete, etc.), details of the closed form (car wheel trims, chains, links, etc.), as well as the intricate details of the simple preparations.
Welding technology:
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