# HOW ARE FILLER RODS CLASSIFIED FOR THE GTAW-TIG PROCESS? Filler rods used in the GTAW (Gas Tungsten Arc Welding) / TIG (Tungsten Inert Gas) process are classified according to standards established by the **American Welding Society (AWS)**, based on the base metal to be welded. The main classifications are as follows: — ## 1. **FILLER RODS FOR CARBON AND LOW-ALLOY STEEL** ### Standard: **AWS A5.18** | Classification | Description | |—|—| | ER70S-2 | Triple-deoxidized; suitable for rusty or dirty base metals | | ER70S-3 | General purpose; for clean base metals | | ER70S-6 | High manganese and silicon content; for semikilled steels | – **”E”** = Electrode – **”R”** = Rod (filler rod) – **”70″** = Minimum tensile strength (70,000 psi) – **

The properties of the deposited weld metal depend on the type of filler metal, type of shielding gas, and the welding process variables that are identified according to standards; for this reason, and in order to organize the different types of consumables by classifying them according to the type of metal to be welded, several institutions or associations created standards or specifications for this purpose.

Below, two of the most widely known standards worldwide are detailed, beginning with the best known, AWS, followed by the Euro Standard EN, or depending on the country, the DIN standard.

In the system developed by AWS, only filler metals are classified, with shielding gases being excluded. The rods commonly used for the GTAW process are covered by the following specifications:

AWS A5.18 – 93          Specification for the Classification of Wires and Rods for Welding with the GTAW and PAW Processes of Carbon Steels.

AWS A5.28 – 79          Specification for the Classification of Wires and Rods for Welding with the GTAW and PAW Processes of Low-Alloy Steels.

AWS A5.9 – 93            Specification for the Classification of Wires and Rods for Welding with the GTAW and PAW Processes of Stainless Steels.

AWS A5.10 – 88          Specification for the Classification of Wires and Rods for Welding with the GTAW and PAW Processes of Aluminum and its Alloys.

AWS A5.7 – 84            Specification for the Classification of Wires and Rods for Welding with the GTAW and PAW Processes of Nickel and its Alloys.

AWS A5.14 – 89          Specification for the Classification of Wires and Rods for Welding with the GTAW and PAW Processes of Magnesium Alloys.

AWS A5.16 – 90          Specification for the Classification of Wires and Rods for Welding with the GTAW and PAW Processes of Titanium and its Alloys.

AWS A5.24 – 90          Specification for the Classification of Wires and Rods for Welding with the GTAW and PAW Processes of Zirconium and its Alloys.

The metals covered by the following specification may also be used in the GTAW Process:

AWS A5.2 – 88            Specification for the Classification of Rods for Welding with the OFW Process of Carbon and Low-Alloy Steels.

Classification Criteria.

Below, some of the most widely applied AWS Specifications for GTAW Process welding are detailed.

In the case of AWS Specification A5.18 – 93, which classifies filler metals for welding Carbon Steels, and AWS A5.28 – 79, which classifies filler metals for welding Low-Alloy Steels, these specifications are the same as those used for GMAW Process consumables; therefore, the same concepts will be repeated.

The classification of the rods covered by these two specifications is based on the mechanical properties of the deposited weld metal in the as-welded condition, type of shielding gas, and chemical composition.

Classification System.

The classification of rods in AWS Specifications A5.18 and A5.28 has the following characteristics:

Where:

1. The letters ER, when used together, refer to the consumable in the form of a Wire or Rod, applicable to the GMAW, GTAW, and PAW Processes.

• These digits, which could also be three in number, indicate the minimum Tensile Strength of the deposited weld metal, in thousands of pounds per square inch. Some examples are given below.

• 3. This digit, in letter form, indicates the following:

S          Indicates that it is a Solid Wire or Rod.

C         Indicates that it is a Composite Wire or Rod.

• 4. This last digit indicates the chemical composition of the deposited weld metal, in percent units. In the case of AWS Specification A5.18, “Wires and Rods for Welding with the GTAW and PAW Processes of Carbon Steels,” it consists of a single number for solid wires and rods, and of a number and a letter for composite metals, which are used only in the GMAW Process. In AWS Specification A5.28, “Wires and Rods for GTAW and PAW Welding of Low-Alloy Steels,” it consists of letters and numbers.

AWS A5.18 SPECIFICATION – Solid Wires and Rods

AWS A5.28 SPECIFICATION

Single values correspond to the maximum

1. All values are given in percent units.
2. N.S. = Not Specified.

The classification of filler metals, Wires and Rods for welding Stainless Steels, also referred to as Corrosion-Resistant, Chromium, and Chromium-Nickel steels, under AWS Specification A5.9, is based on the chemical composition of the deposited weld metal, and is similar to the classification adopted by AISI for steels with those same properties.