Flux-Cored Electrodes’ Usability Designators: What Do They Mean?
Q: I am a new salesperson for a welding supply company. I have noticed that the AWS classification number for many of the flux-cored wires we carry are the same on the front end, but then have different dash numbers on the back end. Some example numbers are E71T-1, E71T-8, E71T-9, E71T-11, etc. Some wires even have two or three numbers on them. I have heard these “dash numbers” called performance capabilities numbers. But what exactly do they mean? Also, how can some wires have more than one AWS number?
A: The dash numbers you are asking about are called “Usability Designators” and refer to the usability of the electrode with requirements for polarity and general operating characteristics. Before discussing the specifics of each designator, a quick review of the meaning of an electrode’s entire American Welding Society (AWS) classification number is in order. Figure 1 shows the key to an electrode’s AWS classification number. Each letter and digit in the number indicates something about the electrode. Complete details about these electrode classification numbers and more are contained in the AWS document A5.20/A5.20M:2005, titled “Specification for Carbon Steel Electrodes for Flux Cored Arc Welding”.
Figure 1: Key to AWS Classification Designators for Carbon Steel Flux-Cored Electrodes
As stated earlier, the usability designators for flux-cored electrodes specify the requirements for polarity and general operating characteristics. These designators may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, G or GS. Each usability designation indicates a general grouping of electrodes that contain similar usability characteristics. The exceptions are the “G” and “GS” classifications, where usability characteristics may differ between similarly classified electrodes.
The “G” stands for “general” classification. “GS” stands for general, “single” pass only applications. In both cases, it is general because not all of the particular requirements specified for the other designation classifications are specified for this classification. The intent for the general designation is to allow newly developed flux-cored electrodes that may differ in one way or another to all the other usability designations a way to still be classified according to the filler metal specification. This allows an electrode to be used right away, without having to wait potentially years for the filler metal specification to be revised to create a new usability designation.
The usability designator also indicates a particular flux-cored electrode’s type of shielding system. AWS classifies all flux-cored electrodes into one group for the Flux-Cored Arc Welding (FCAW) process. However, there are two fundamentally different categories or sub-sets of electrodes in this group. These include self-shielded, flux-cored electrodes (FCAW-S process) and gas-shielded, flux-cored electrodes (FCAW-G process). They are all tubular electrodes with fluxing elements inside the electrode which, among other things, produce a slag covering of the weld. However, self-shielded electrodes completely produce their own shielding system (like Shielded Metal Arc Welding (SMAW) or stick electrodes), while gas-shielded electrodes also utilize an external shielding gas system (i.e., they are double shielded).
These usability designators can be sub-divided into the two main categories of electrodes as follows:
Self-Shielded, Flux-Cored Electrodes: T-3, -4, -6, -7, -8, -10, -11, -13, -14, -G, -GS
Gas-Shielded, Flux-Cored Electrodes: T-1, -2, -5, -9, -12, -G, - GS
Detailed information on each of these usability designation classifications are found in the AWS A5:20/A5.20M:2005* carbon steel flux cored filler metal specification. Various tables in the specification include requirements for each usability designation. Table 1 lists the required mechanical properties. Table 2 lists the “Electrode Usability Requirements”, including position of welding, use or none use of an external shielding gas, polarity and application (single or multi-pass). Table 3 lists the tests required for classification. Table 6 lists the weld metal chemical composition requirements. In addition, Annex A, Section A7 contains a detailed description and intended use for each usability designator.
A summary of the main points of each usability designation group are included in this article in Figures 2 and 3.
* The dual numbering system for filler metal specifications (e.g. A5:20/A5:20M) means that they include both English units and metric units. The year of publication is also included at the end of the document number.
Figure 2: Description of Usability Designations for Self-Shielded, Flux-Cored Electrodes
Figure 3: Description of Usability Designations for Gas-Shielded, Flux-Cored Electrodes
Addressing the second question for this column, some electrodes do indeed carry two or more different AWS classification numbers. This is quite common with electrodes that are dual classified as a “T-1” and “T-9” electrode. Referring back to figure 3, note that these two usability designations have the exact same electrode and operating characteristics. The only difference is with the impact properties. A “9” electrode has a more stringent impact toughness requirement of 20 ft•lbf @ -20⁰ F (27 J @ -29⁰ C) versus a “1” electrode of 20 ft•lbf @ 0⁰ F (27 J @ -18⁰ C). Therefore, if a specific electrode can meet the minimum impact toughness requirement at the colder -20⁰ F (-29⁰ C) temperature, then it can also more easily meet it at the warmer 0⁰ F (-18⁰ C) temperature. Thus one electrode can meet the requirements of two different usability classifications.
In other cases, electrodes may be tri-classified as a “T-1”, “T-9” and “T-12” electrode. A “12” designation classification also has the exact same electrode and operating characteristics as a “1” and “9” classification. A “12” classification has a slightly lower maximum manganese (Mn) level and slightly lower maximum tensile strength cap than “1” and “9” classifications. Therefore, “12” electrodes also meet the requirements of “1” and “9” electrodes. While “12” electrodes were traditionally classified by themselves, manufacturers have more recently begun to tri-classify them.
Note that flux cored electrodes can also have an optional "J" designator. This means that the electrode can meet an even more stringent impact toughness requirement of 20 ft•lbf @ -40⁰ F (27 J @ -40⁰ C). Most “12” electrodes have the optional J designation. However, a “12” electrode does not technically have to meet Charpy V-notch (CVN) values of 20 ft•lbf @ -40⁰ F (27 J @ -40⁰ C), it is just that most do. Note also that while most “1” / “9” electrodes do not have an optional J designator, they technically could have it if they met the impact requirement. And in fact, some do carry the optional J designator, such as Lincoln Electric’s Outershield® 71M electrode.
This column has focused on carbon steel electrodes. However, there are also low alloy flux-cored electrodes available in the welding market. These electrodes are classified in the AWS document A5.29:A5.29M:2010 “Specification for Low Alloy Electrodes for Flux Cored Arc Welding”. These electrodes produce welds that are typically stronger than welds made with carbon steel electrodes, and have minimum tensile strengths of 80 to 120 ksi (550 – 827 MPa).
Their electrode classification numbers are similar to carbon steel electrodes, including similar (but less) usability designation classifications. The mechanical properties and weld metal chemical composition requirements of each usability classification can vary with different alloy types and alloy levels in each electrode. Again the detailed requirements of each usability classification are contained in various tables in the A5.29:A5.29M filler metal specification.
These usability designators for low alloy flux cored electrodes can by sub-divided into the two main categories of electrodes as follows:
• Self-Shielded, Flux-Cored Electrodes: T4, 6, 7, 8, G
• Gas-Shielded, Flux-Cored Electrodes: T1, 5, G
One slight difference with low alloy electrodes’ classification numbering system is that the usability designator, following the “T” designator, now precedes the dash, with the deposition composition or alloy designator now following the dash. For example, a carbon steel electrode might have the classification number “E71T-1M-JH8”, while a low alloy electrode might have the classification number “E81T1-K2M-JH4”.
As a final point, note that there is a new filler metal specification, AWS A5.36/A5.36M:2012, “Specification for Carbon and Low-Alloy Steel Flux Cored Electrodes for Flux Cored Arc Welding and Metal Cored Electrodes for Gas Metal Arc Welding". It covers both carbon steel and low alloy flux-cored electrodes, as well as carbon steel and low alloy metal cored electrodes. It is the first of a new and improved style of filler metal specifications. It is effective now and runs in conjunction with AWS A5.20 and A5.29 until 2015. At that point the old specifications will be obsolete and the new A5.36 specification will be the only one in effect. While the usability designations are similar to those in A5.20 and A5.29, it does include a few slight changes and some additional ones involving metal cored wires. However, discussion of this new A5.36 specification is for a future column.