The Esab Group Inc.

Michael C McBennett

Gregory William Diehl

Rue Allen Lynch

Tommie Zack Turner

An electrode for a plasma arc torch and method of fabricating the same are disclosed, and wherein the electrode comprises a copper holder defining a cavity in a forward end. An emissive element and separator assembly is positioned in the cavity, and no brazing materials are used to secure the components of the electrode. The emissive element, separator, and metallic holder are heated to accelerate diffusion bonding between the emissive element and separator, and between the separator and metallic holder. A crimping process is also disclosed for further strengthening the electrode and increasing the operational life span thereof.

Electrode diffusion bonding

An electrode for a plasma arc torch and method of fabricating the same are disclosed, wherein the electrode comprises a metallic holder defining a cavity in a forward end. An emissive element and separator assembly is positioned in the cavity. The emissive element has a layer of relatively non-emissive material on the outer surface thereof, which is preferably applied by heating the emissive element to a high temperature such that the emissive element becomes reactive, and spraying the relatively non-emissive material on the emissive element. The coated emissive element is positioned in the separator and the assembly is heated such that the relatively non-emissive material forms a strong bond between with the separator. The superior bonds between the emissive element and separator formed according to the present invention extend the life span of the electrode.

Method of coating an emissive element

An electrode for supporting an arc in a plasma arc torch is provided and includes an emissive element for supporting the arc, which may be formed of hafnium; a relatively non-emissive member comprising a first metal including silver, which is positioned to circumscribe a front surface of the emissive element; and a metallic holder for holding the non-emissive member. The holder is in one embodiment made of a copper alloy including a major portion of copper and a minor portion of another metal, such as nickel. After assembly, the electrode is subjected to a heat treatment that causes a thermal bonding between the relatively non-emissive member and the metallic holder, which, during subsequent operation of the electrode, provides good thermal conduction away from the emissive element and improves the consumable life of the electrode. Advantageously, during the heating step, the nickel attenuates the eutectic reaction between the copper and the silver that would otherwise occur and allows bonding over a wide range of temperatures and heating cycle durations. In addition, the temperature at which bonding occurs between the non-emissive member and the holder is also raised. As a result, if desired, a thermal bond can also be formed between the hafnium emissive element and the non-emissive member during the same heating cycle, thus further promoting thermal conductivity of the electrode. In alternative embodiments, other metals and other configurations, such as the use of an intervening plating, powder or sleeve are used to raise, and provide a greater range for, the temperatures over which bonding occurs between the non-emissive element and the holder.

Electrode component thermal bonding

An electrode for a plasma arc torch and method of fabricating the same are disclosed, and wherein the electrode comprises a copper holder defining a cavity in a forward end. An emissive element and separator assembly is positioned in the cavity, and no brazing materials are used to secure the components of the electrode. An intermetallic compound is formed between the emissive element and the separator, and a eutectic alloy is formed between the separator and metallic holder by independent heating steps. A crimping process is also disclosed for further strengthening the electrode and increasing the operational life span thereof.

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Lamar, SC, United States of America

Michael C McBennett