Difference between E309L-15, 16 17, E316L-15,16 and 17 & 26
For Stick or SMAW Welding stainless steel electrodes, there are 3 types of electrode coating, as 15, 16, 17 and 26. The electrodes are designated as E309L-15, E309L-16, E309L-17 and E309L-26 etc. The same rule is applicable for other stainless steel electrodes as per SFA 5.4 such as E308, E316, E310, E321 and so on. So, what is the difference between these different types?
First of all these are called, Usability characteristics of the electrode that mean the factors that affects how an electrode can be used? You must remember that this number does not affect the mechanical properties or chemical properties of the electrodes. They only affect the electrical characteristics and welding positions as shown in below table.
Usability Characteristics of SMAW/ STICK Welding Electrode
The type of covering used for a electrode core wire to make a SMAW or stick welding electrode usually determines the usability characteristics of the electrode. This article explains the covering types which is used by the electrode manufacturers.
Usability Designation -15
Electrode with 15 number at the end e.g. 309L-15 has a lime-based coating (Basic type) and is shall be used for DCEP polarity only. These electrodes produces lighter slag than the other two types (16 and 17) and used for all position welding, with some electrodes of this type used mainly for vertical down welding. They gives better impact properties compare to other type due to their basic coating.
The electrodes are usable with dcep (electrode positive) only. While use with alternating current is sometimes accomplished, they are not intended to qualify for use with this type of current. Electrode sizes 5/32 in [4.0 mm] and smaller may be used in all positions of welding.
Usability Designation -16.
Electrode with 16 number at the end e.g. 309L-16 has a titania or rutile-based coating and can be used with both DCEP and AC polarity. Electrode sizes of 5/32 in. (4.0 mm) and smaller are often used for all welding positions. Electrodes having 26 classification is the same as a “16” type coating, but gives higher deposition rate and limited to the flat and horizontal position only and will not work for vertical and overhead position.
The covering for these electrodes generally contains readily ionizing elements, such as potassium, in order to stabilize the arc for welding with alternating current. Electrode sizes 5/32 in [4.0 mm] and smaller may be used in all positions of welding.
Usability Designation -17
Electrode with 17 number at the end e.g. 309L-17 has a silica-titania type coating and is a modified type of a 16 coating, in that some of the titania is replaced with silica. These electrodes also can be used with both DCEP and AC polarity. Additional silicon in the coating works as a wetting agent, giving the effect of increasing weld puddle fluidity. This is mainly helpful with stainless steel, as it tends to have more of a sluggish weld bead than carbon steel. 17 type electrodes produce a flatter bead profile than the other two types and are often used for flat and horizontal position welding. However, electrode sizes of 5/32 in. (4.0 mm) and smaller can be used for all position welding. Note that with a vertical up progression, the slower freezing slag will require more of a weave technique than with a 16-type electrode.
The covering of these electrodes is a modification of the -16 covering, in that considerable silica replaces some of the titania of the -16 covering. Since both the -16 and the -17 electrode coverings permit ac operation, both covering types were classified as -16 in the past because there was no classification alternative until the 1992 revision of AWS A5.4. However, the operational differences between the two types have become significant enough to warrant a separate classification.
On horizontal fillet welds, electrodes with a -17 covering tend to produce more of a spray arc and a finer rippled
weld-bead surface than do those with the -16 coverings. A slower freezing slag of the -17 covering also permits improved handling characteristics when employing a drag technique. The bead shape on horizontal fillets is typically flat to concave with -17 covered electrodes as compared to flat to slightly convex with -16 covered electrodes. When making fillet welds in the vertical position with upward progression, the slower freezing slag of the -17 covered electrodes requires a slight weave technique to produce the proper bead shape. For this reason, the minimum leg-size fillet that can be properly made with a -17 covered electrode is larger than that for a -16 covered electrode. While these electrodes are designed for all-position operation, electrode sizes 3/16 in [4.8 mm] and larger are not recommended for vertical or overhead welding.
Usability Designation -26
This designation is for those electrodes that are designed for flat and horizontal fillet welding and that have limited out of position characteristics. In practice, most of these electrodes give higher deposition rates than their all-positional counter-parts owing to their thicker coatings that contain higher levels of metal powders. The thicker coating gives larger fillet welds that are typically flat to concave. It also reduces the effects of core wire overheating, making 18 inch long electrodes possible for the larger electrodes, even with stainless steel core wire. Higher currents are usually required to achieve the necessary penetration compared to the all-positional types.
The slag system of these electrodes is similar to those of the -16 and -17 designations. The resulting slag may be more
fluid and even slower freezing than that from electrodes with a -17 designation. Core wire compositions are typically either Type 304L stainless steel or low-carbon mild steel. Electrodes with the latter tend to have thicker coatings to accommodate the necessary alloys in order to attain the required weld metal composition. Such electrodes require even higher currents to compensate for the additional coating to be melted and the lower resistance of the core wire.
Electrodes with the -26 designation are recommended for welding only in the flat and horizontal fillet positions. The manufacturer’s suggested operating current.