A The **AWS A5.18** is the industry standard that classifies **carbon steel electrodes and rods** used for **gas shielded arc welding**, most commonly **MIG welding (GMAW)**.
This specification ensures that all solid wires for welding mild and low-alloy steels meet strict chemical composition and performance criteria.
Understanding this classification is essential for welders to select the appropriate **welding wire** to achieve strong, reliable, and defect-free **welds** on a variety of steel types.

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The classification system uses a specific alphanumeric code to provide detailed information about the wire’s characteristics.
A common example is **ER70S-6**, which can be broken down to understand the wire’s tensile strength, its form, and its chemical composition.
This standardized system makes it straightforward for fabricators and welders to choose the correct filler metal for their specific application, ensuring compatibility with the **base metal** and welding process.

What do the parts of an AWS A5.18 designation mean?

The "ER" prefix stands for **Electrode** and **Rod**, indicating the filler metal can be used as a continuous wire for MIG welding or as a rod for TIG welding.
The first two digits, such as "70," denote the minimum tensile strength of the deposited weld metal, which in this case is 70,000 psi (480 MPa).
The "S" indicates that the wire is a **solid** wire, which distinguishes it from flux-cored wires.
The final number, for example, "-6," specifies the precise chemical composition of the wire, particularly the levels of deoxidizers like silicon and manganese.

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Two of the most widely used classifications are **ER70S-3** and **ER70S-6**, each with distinct properties suited for different welding conditions.

What are the characteristics of ER70S-6 welding wire?

**ER70S-6** is a very popular **carbon steel MIG wire** known for its high levels of **silicon and manganese**.
These deoxidizers make it an excellent choice for welding on steel that has moderate rust, mill scale, or other surface contaminants.
The wire produces a smooth arc, good bead wetting action, and a clean, porosity-free weld, making it ideal for general fabrication, automotive repairs, and shipbuilding.

What are the characteristics of ER70S-3 welding wire?

**ER70S-3** is another common type, but it contains lower levels of deoxidizers compared to ER70S-6.
It is best used on clean, shiny steel surfaces that are free of contaminants.
This wire is often chosen for its good arc stability and smooth appearance, making it a reliable choice for manufacturing and applications where a clean surface is guaranteed.

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