Copper Alloys

The RWMA provides classifications for different alloy types, each suited for specific welding conditions. These standards ensure that when you specify an alloy class, you know what to expect in terms of performance characteristics. This standardization is crucial for quality control and process reliability across different manufacturing setups.

• Class 1 (CuZr): Used for welding highly conductive materials like aluminum and magnesium alloys, as well as coated materials like galvanized steel. It offers a good balance of high electrical conductivity and strength, superior to pure copper.
• Class 2 (CuCr or CuCrZr): A superior, general-purpose electrode material for high-production operations. It is widely used for spot and seam welding of cold- and hot-rolled steels, stainless steel, and also galvanized steel.
• Class 3 (CuCoBe or CuNiSiCr): Known for its high hardness and resistance to deformation under high forces. It is typically used for welding high-resistance materials like stainless steels, Monel, and Inconel, and is often used for projection welding dies and current-carrying structural members.
• Class 4 (CuBe): This is the hardest RWMA alloy, offering extremely high hardness and compressive strength, comparable to some steels. It is recommended for applications involving very high pressures and severe wear, such as specific projection, flash, and butt-welding dies, where heating is not excessive due to its lower conductivity compared to other classes.

It is important to use high quality virgin copper alloys, this insures weld repeatability and weld quality.

RWMA Copper Alloys

RWMA Class 1

Also Known as: Tuffaloy 88, CMW 28, CuZr, and CuCd.

ZIRCONIUM-COPPER, suited to welding aluminum & magnesium alloys, coated materials, and brass & bronze.

Class 1: This alloy surpasses pure copper as an electrode material, and manufacturers recommend it as a general-purpose material for resistance welding use. Users may employ it for spot welding electrodes, seam welding wheels and welding fixture components. Heat treatment cannot strengthen it.

RWMA Class 2

CHROMIUM-COPPER, suited to welding cold- and hot-rolled steels, stainless steel, and low conductivity brasses and bronzes.

Also Known as: CMW 3, CMW 328, Mallory 3, Tuffaloy 77, and Tuffaloy Z, CuCr, and CuCrZr.

Class 2: This alloy provides superior resistance welding electrode material, which manufacturers recommend for high-production operations. Users employ it for welding electrodes, projection welding dies, seam welding shafts and bearings, flash and butt welding dies, and current-carrying structural components. Manufacturers offer it in forms that users can apply as welding gun arms, welding platens and secondary-circuit structural members. Heat treatment can strengthen it.

ZIRCONIUM-CHROMIUM-COPPER is suited to welding galvanized steel & other metallic-coated steel. Manufacturers specially heat-treat this alloy, which meets the minimum electrical conductivity and hardness specifications of Class 2 alloy.

RWMA Class 3

Also Known as: CMW 100, CMW 353, Mallory 100, Tuffaloy 55, Tuffaloy 55A, CuNiSiCr, and CuNiBe.

BERYLLIUM-NICKEL-COPPER and NICKEL-COPPER are suited to welding steels having high electrical resistance, such as stainless steel.

Class 3: Manufacturers recommend this alloy for projection welding dies, and flash and butt-welding dies. Its higher strength allows users to employ it on highly current-carrying parts such as electrode shanks and heavy-duty electrode holders. It is heat treatable.

RWMA Class 4

Also Known as: Tuffaloy 44, CMW 73, and CuBe.

BERYLLIUM-COPPER has extremely high hardness, and manufacturers recommend it for projection, flash and butt-welding dies. It delivers lower conductivity than Class 3 alloy but offers harder and more wear-resistant properties. Users should consider it where high-pressure density and severe wear create concern, but where heating is not excessive due to its low conductivity.

Users employ it frequently in the form of inserts, die facings, and seam welder bushings. Manufacturers supply it in the annealed condition, which machines more readily, and users then subsequently heat-treat it.

RWMA Class 20

Also Known as: Elkaloy 20 and CuAL₂O₃

COPPER-ALUMINUM OXIDE resists deformation exceptionally well when welding, and manufacturers highly recommend it for weld caps when welding coated and galvanized steels. It enables a stable start-up and generally outlasts other cap material when operators do not carefully control welding parameters.