Submerged arc wire electrode contact nozzle with copper free inlay to reduce copper induced cracking
Publication Date: 2017-Jan-03
The IP.com Prior Art Database
The present document relates to the arc welding industry and more particularly to the wire contact nozzle having a copper-free inlay.
In an arc welding process an electrical arc is burning between an electrode and the work pieces. In case of a welding process with self consuming wire electrode such as gas metal arc welding (GMAW), metal-cored wire electrode (GMAW-C), gas shielded flux cored arc welding (FCAW-G) and submerged arc welding (SAW), the electric arc melts the wire electrode and the work piece. After the welding process the fused mix of electrode and base metal solidifies on the not molten work pieces with a common composition. The solidified weld metal now forms the link between the work pieces.
The wire electrode is fed through drive rolls and passes by a contact nozzle. Inside the contact nozzle the current from the electrical power source is transferred to the wire electrode.
The wire feeding rollers have a V- shape profile. The wire electrode with a circular section is laying inside the V. In order to improve the transportation by the feeding rollers, the surface of the rollers are dented. Each tooth leaves a mark on the wire surface.
The contact nozzle is usually made out of a copper alloy for its good electrical and thermal conductivity. Sometimes copper alloys are used which try to compromise between thermal conductivity and abrasion resistivity.
During welding the contact nozzle can be consumed in various ways such as erosion by the rough wire electrode surface which originates from the dented wire feeding rollers, or by a poor contact inside the nozzle itself. In the latter case an arc ignite between the nozzle and the wire. The inside of the nozzle will erode by the arc.
In submerged arc welding (SAW) the electrical arc is burning below a burden of a flux with a well designed composition. The flux provides a stable arc, protects the arc against atmosphere, modifies the weld metal composition and contributes to form the weld surface after solidification.
It is common praxis in submerged arc welding to use one or more wire electrode to be fed into the groove between to work pieces. The groove is filled with submerged arc welding flux. During the welding process the molten weld metal from the consumed welding electrodes and fused base metal is covered with a molten slag and solidifies before the slag does.
During the feeding of the welding electrode through the welding nozzle, small copper containing particles from the nozzle can fall on the surface of the molten slag, they can become heatedor even fused by the molten slag and dive as particles or droplets by gravity onto the surface of the weld metal.
The melting interval of the weld pool is between 1400- 1800°C, the one of pure copper at 1081°C, the one of copper alloys is even lower. As a result the molten copper alloy can pass the slag and eventually dispose on the up...