What is the RWMA Classification System>

Created at : Dec 13, 2023

What is the RWMA classification system? 

The RWMA (Resistance Welding Manufacturing Alliance) is a committee of the American Welding Society (AWS) that:
-    Represents manufacturers making products for resistance welding process and application
-    It provides a forum for the exchange of information and ideas among its members
-    It develops and promotes standards for resistance welding equipment and processes

The RWMA classification system is a simple means to identify materials having similar hardness and electrical conductivity values. It is used in resistance welding to select the appropriate material for a specific application. By choosing the appropriate RWMA class, engineers, welders, manufacturers can ensure consistency, quality, efficiency, and cost savings. It is also used to classify the composition and properties of materials used in resistance welding operations, such as electrodes. 

There for 4 RWMA Classes, each with its own specific properties and characteristics:

RWMA Class 1: Is a group of copper alloys with good strength and high electrical conductivity. Often used to weld aluminum, galvanized or coated materials, and other good conductors. 

-    Class 1 material is C15000 (Copper Zirconium)

RWMA Class 2: Is a group of heat-treatable copper alloys with a combination of high tensile strength and good thermal and electrical conductivity. Class 2 has a lower copper content than Class 1 but is harder and wear-resistant for high-production operations.

-    Class 2 material is C18200 (Copper Chromium) and C18150 (Copper Chromium Zirconium)

RWMA Class 3: Is a group of copper alloys with a lower copper content than Class 2 but are the hardest and most wear-resistant for high-production operations. They also have the lowest conductivity of the classes. 

-    Class 3 material is C18000 (Copper nickel Silicon Chromium) and C17510 (Copper Nickel Beryllium)

RWMA Class 4: Is a group of Beryllium copper alloys with extremally high hardness and compressive strength with lower electrical conductivity.  Often used for projection welding, flash welding and butt-welding applications.  
-    Class 4 material is C17200 (Copper Beryllium) Note: 11/22/23 Beryllium has become a scarce and expensive material due to the mines that harvest the beryllium are in hostile/war -torn areas of the world.

What do RWMA Classes do for engineers, welders, manufacturers? 

The RWMA Classes ensure consistency, quality, efficiency, and cost savings by: 

Consistency: The RWMA classification system provides a consistent and standardized method for selecting the appropriate alloy for the welding application. 
Quality: Engineers, welders, manufacturers can ensure that the RWMA classified materials they are using have the necessary properties for producing a high-quality weld.  
Efficiency: The classification system helps reduce the time and effort to select the appropriate material for the welding application because the properties and characteristics are defined. 
Cost savings: The RWMA classes can help engineers, welders, and manufacturers select the best copper alloy rather than the most expensive. 

In addition, the classification system is based on chemical composition, mechanical properties, and weldability. Here is how the RWMA Class (Group A) stack up:  

RWMA Class    Chemical Composition    Mechanical Properties    Weldability
Class 1    High copper content    Soft, ductile    Excellent
Class 2    Lower copper content than Class 1    Harder, more wear-resistant     Good
Class 3    Even lower copper content than Class 2    Hardest, most wear-resistant    Fair
Class 4    Specialty alloy    Unique properties    Variable

Submitted by Cadi Company