SMAW Electrode types and welding rod number meaning & classification

SMAW Electrode: Classification, types, coating types

SMAW Electrode: Classification, types, coating types

SMAW Welding or stick welding electrodes are classified based on the following factors:

  1. Size –The commonly available sizes are 3/32, 1/8 (commonest), 5/32, and 3/16, 7/32, ¼ and 5/16 inches (2.4, 2.5, 3.2, 4.0, 4.8, 5.0, 5.6, 6.0, 6.4 & 8.0 millimeter).
  2. Type of current: AC, DC (DCEP/ DCEN)
  3. Type of covering: Cellulose, rutile, acid, basic, iron powder, etc. as explained in detail in this article.
  4. Material –The stick welding electrodes come in mild steel, iron-free, high carbon steel, cast iron, stainless steel, and special alloy.
  5. Strength –The tensile strength of the weld needs to be stronger than the metal being welded. The material in the electrode needs to be stronger as well to accommodate the weld dilution happening due to electrode coating/ base metal.
  6. Welding position –The different electrodes used for each welding position as horizontal, flat, vertical, overhead as given in figure 1, etc. Watch this YouTube Video to learn about different welding positions.

Most common SMAW welding rod numbers

E6010– E6010 [E4310] electrodes are characterized by a deeply penetrating, forceful, spray type arc and readily removable, thin, friable slag which may not seem to completely cover the weld bead. Fillet welds usually have a relatively flat weld face and have a rather coarse, unevenly spaced ripple. The coverings are high in cellulose, usually exceeding 30% by weight. The other materials generally used in the covering include titanium dioxide, metallic deoxidizers such as ferromanganese, various types of magnesium or aluminum silicates, and liquid sodium silicate as a binder. Because of their covering composition, these electrodes are generally described as the high-cellulose sodium type. These electrodes are recommended for all welding positions, particularly on multiple pass applications in the vertical and overhead welding positions and where welds of good soundness are required. They frequently are selected for joining pipe and generally are capable of welding in the vertical position with either uphill or downhill progression.

These electrodes have been designed for use with DCEP (electrode positive). The maximum amperage that can generally, be used with the larger sizes of these electrodes is limited in comparison to that for other classifications due to the high spatter loss that occurs with high amperage.

E6011– The oily, dirty, dusty, and rusty surfaces need this type of electrode. It is versatile as it works for AC and DC polarity. It can create a small slag and need not be placed in an electrode oven. E6011 [E4311] electrodes are designed to be used with ac current and to duplicate the usability characteristics and mechanical properties of the E6010 [E4310] classification. Although also usable with DCEP (electrode positive), a decrease in joint penetration will be noted when compared to the E6010 [E4310] electrodes. Arc action, slag, and fillet weld appearance are similar to those of the E6010 [E4310] electrodes.

The coverings are also high in cellulose and are described as the high-cellulose potassium type. In addition to the other ingredients normally found in E6010 [E4310] coverings, small quantities of calcium and potassium compounds usually are present.

E6012- [E4312] electrodes are characterized by low penetrating arc and dense slag, which completely covers the bead. This may result in incomplete root penetration in fillet welded joints. The coverings are high in titania, usually exceeding 35% by weight, and usually are referred to as the “titania” or “rutile” type. The coverings generally also contain small amounts of cellulose and ferromanganese, and various siliceous materials such as feldspar and clay with sodium silicate as a binder. Also, small amounts of certain calcium compounds may be used to produce satisfactory arc characteristics on DCEN (electrode negative). These electrodes are all-position electrodes and usually are suitable for welding in the vertical welding position with either the upward or downward progression.

E6013–The welding rod specifications are designed for thin metals and joints that are not easy to fit together. E6013 [E4313] electrodes, although very similar to the E6012 [E4312] electrodes, have distinct differences. Their flux covering makes slag removal easier and gives a smoother arc transfer than E6012 [E4312] electrodes. Coverings of E6013 [E4313] electrodes contain rutile, cellulose, ferromanganese, potassium silicate as a binder, and other siliceous materials. The potassium compounds permit the electrodes to operate with ac at low amperages and low open-circuit voltages.

E7014- E7014 [E4914] electrode coverings are similar to those of E6012 [E4312] and E6013 [E4313] electrodes, but with the addition of iron powder for obtaining higher deposition efficiency. The covering thickness and the amount of iron powder in E7014 [E4914] are less than in E7024 [E4924] electrodes. The amount and character of the slag permit E7014 [E4914] electrodes to be used in all positions.

Low Hydrogen type– The iron powder is added in the flux to create a strong weld. It creates puddle which may have difficulty for beginners. Electrodes of the low-hydrogen classifications E6018 [E4318], E7015 [E4915], E7016 [E4916], E7018 [E4918], E7018M [E4918M], E7028 [E4928], and E7048 [E4948]) are made with inorganic coverings that contain minimal moisture. In order to maintain low-hydrogen electrodes with minimal moisture in their coverings, these electrodes should be stored and handled with considerable care.

  1. E7015- E7015 [E4915] electrodes are low-hydrogen electrodes to be used with DCEP (electrode positive). The slag is chemically basic. These electrodes are commonly used for making small welds on thick base metal, since the welds are less susceptible to cracking. They are also used for welding high-sulfur and enameling steels. Welds made with E7015 [E4915] electrodes on high-sulfur steels may produce a very tight slag and a very rough or irregular bead appearance in comparison to welds with the same electrodes in steels of normal sulfur content. The arc of E7015 [E4915] electrodes is moderately penetrating. The slag is heavy, friable, and easy to remove.
  2. E7016- E7016 [E4916] electrodes have all the characteristics of E7015 [E4915] electrodes, plus the ability to operate on ac. The core wire and coverings are very similar to those of E7015 [E4915], except for the use of a potassium silicate binder or other potassium salts in the coverings to facilitate their use with ac.
  3. E7018- E7018 [E4918] electrode coverings are similar to E7015 [E4915] coverings, except for the addition of a relatively high percentage of iron powder. The coverings on these electrodes are slightly thicker than those of the E7016 [E4916] electrodes. They can be used with either ac or DCEP. Electrodes designated as E7018-1 [E4918-1] have the same usability and weld metal composition as E7018 [E4918] electrodes, except that the manganese content is set at the high end of the range. They are intended for welds requiring a lower transition temperature than is normally available from E7018 [E4918] electrodes.
  4. E7024– E7024 [E4924] electrode coverings contain large amounts of iron powder in combination with ingredients similar to those used in E6012 and E6013 [E4312 and E4313] electrodes. The coverings on E7024 [E4924] electrodes are very thick and usually amount to about 50% of the weight of the electrode, resulting in higher deposition efficiency. The E7024 [E4924] electrodes are well suited for making fillet welds in the flat or horizontal position.
  5. E7028– E7028 [E4928] electrodes are very much like the E7018 [E4918] electrodes. However, E7028 [E4928] electrodes are suitable for fillet welds in the horizontal welding position and groove welds in the flat welding position only, whereas E7018 [E4918] electrodes are suitable for all positions. The E7028 [E4928] electrode coverings are much thicker. They make up approximately 50% of the weight of the electrodes. The most common electrode classification for SMAW electrodes is shown in figure 2.

Types of SMAW Electrode Coating & their various functions.

SMAW Electrode: Classification, types, coating types

Welding rods coatings for mild and low steel alloy have six to twelve ingredients that include:

  1. Cellulose– The cellulose disintegrates to produce a gas shield that protects the arc by surrounding it.
  2. Metal carbonates– It provides a reducing atmosphere and adjusts the basicity of the slag.
  3. Titanium dioxide– It is helpful in forming a highly fluid and quick-freezing slag and provides ionization of the arc of the welding. 
  4. Ferromanganese and ferrosilicon– This covering helps to deoxidize the molten metal and also supplement the manganese and silicon content in the deposited weld metal.
  5. Gums and clays– It helps to provide elasticity to the plastic material and provide strength to the coatings.
  6. Mineral silicate– It helps in slag formation and offers strength to the covering.
  7. Calcium fluoride– It produces shielding gas to protect the arc, provide fluidity, adjust the basicity of slag, and solubility of metal oxides. 
  8. Alloying metals as nickel, chromium, and molybdenum– It offers alloy content to the deposited metal.
  9. Manganese or iron oxide– It helps to stabilize the arc and adjust the fluidity and properties of the slag.
  10. Iron powder– It increases productivity and provides extra metal to the weld zone.

SMAW Electrode Coating types for mild steel

  1. Cellulose sodium (EXX10) – This type of electrode has cellulosic material in the form of reprocessed low alloy with 30% paper, and wood flour.  forms a gas shield. The reducing agent carbon dioxide and hydrogen which produces a digging arc for deep penetration. The spatter is at the highest in comparison to other electrodes with a rough weld deposit. It offers extremely good mechanical properties even after aging. It is one of the earliest developed electrodes and used widely in countryside pipeline welding. It is used normally with direct current with reverse polarity when the electrode is positive.
  2. Cellulose potassium (EXX11) –It has similar characters to the cellulose sodium electrode except that here the more potassium is used than sodium. It does ionization of the arc making it suitable to weld with alternating current. The result is similar to cellulose sodium per arc action, penetration, and weld results. A small amount of iron powder is added to E6010 and E6011 for the arc stabilization and better deposition rate.
  3. Rutile sodium (EXX12) –If the titanium or rutile dioxide is high with respect to other components, the electrode gives an appealing appearance to the user. This electrode offers a quiet arc, low spatters, and a controlled slag. The weld surface gives a smooth appearance but with less penetration, and slightly lower metal properties than with cellulose electrodes. This electrode provides a high deposition rate and a low arc voltage to make it fit for alternating current or direct current with electrode negative.
  4. Rutile potassium (EXX13) – This coating of electrode acts very similar to rutile sodium except here potassium is used for the arc ionization. This type of coating produces a very quiet, and smooth-running arc that may be used with suitable for alternating current. It can be used with a direct current of either polarity.
  5. Rutile iron powder (EXXX4) – The coating is very close to a rutile coating with the exception of the iron powder that is included in it. With the iron content of 25-40%, the electrode is EXX14 and 50% or more iron powder makes the electrode EXX24. A lower percentage of iron content makes it suitable for all the positions. The higher percentage of iron makes it suitable for a flat position with horizontal fillet welds. The deposition rate is increased in both cases depending upon the iron content proportion.
  6. Low hydrogen sodium (EXXX5) –A coating with a high proportion of calcium carbonate or calcium fluoride is called lime ferritic, low hydrogen, or basic type electrode. To ensure the lowest possible hydrogen content in the arc atmosphere, the coating should not have cellulose, clays, asbestos, and other minerals. The coatings are baked at a higher temperature and have superior weld metal properties. They offer the highest ductility, medium to moderate penetration with a medium speed of deposition. These must be stored in a controlled condition and can be used with direct current with electrode positive.
  7. Low hydrogen potassium (EXXX6)– The characteristics of these coated welding electrodes are similar to the low hydrogen sodium with the exception of the substitution of potassium from sodium for arc ionization. The electrode is used with AC and can be used with a DC electrode positive. Here the arc is smoother but the penetration of the two electrodes remains the same.
  8. Low hydrogen potassium (EXXX6) – The coating of the electrode here remains similar to the previous one, but the iron powder is added to the electrode in the ratio of 35-40% to name the electrode as EXX18.
  9. Low hydrogen iron powder (EXX28) –This welding electrode has similar characteristics as of EXX18 but has 50% or more iron powder in the coating. It is useful in a flat position and makes a horizontal fillet welding. Here the deposition rate is better than EXX18. The higher alloy electrodes use low hydrogen coatings. We may add specific metal in the coatings to make the electrodes alloy type where suffix letters used to show weld metal compositions. Low hydrogen type electrodes are used for welding stainless steel.
  10. Iron oxide sodium (EXX20) –The high content of iron in the coatings produces a weld deposit that generates a bigger slag and is even difficult to control. This coating produces faster deposition with medium penetration and low spatter level and a very smooth finish in welding. These electrodes are fit for a flat position and make horizontal fillet welds. These electrodes can be used with AC or DC with either polarity.
  11. Iron Oxide Iron power (EXX27) – The features of these electrodes match with iron oxide sodium type electrodes, but it carries 50% or more iron power. This character will improve the deposition rate and can be used with an alternating direct current of either polarity.

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