AWS-A5.1 - 81 Specification for Carbon Steel Covered Arc Welding Electrodes

The American Coding System starts with a prefix E which means an electrode. Then comes a two digit number 60 or 70 designating tensile strength in ksi (60 ksi or 70 ksi). The actual stipulated minimum tensile strength values and the associated yield strength values vary according to the type of covering as given in Table 4.13. The impact strength require­ments are given in Table 4.14.

The third digit indicates the welding positions in which the electrode can be used satis­factorily, as follows:

1. F, H. V. OH

2. F, H-fillet

3. F, H, V-down, OH.

The last two digits together indicate current conditions and the type of covering. Table 4.15 gives complete classification and their significance.

Table 4.13. Strength and elongation requirements for all-weld-metal tension test in the as-weld condition (AWS. A-5.1)

For each increase of 1% in elongation, the tensile strength or yield strength or both may decrease by 7 MPa to a minimum of 420 MPa for tensile strength and 330 MPa for yield strength for E60 series and to a minimum of 480 MPa for tensile and 400 MPa for yield strength for E70 series, except for E6012, E6013 tensile and yield strength may reduce to a minimum of 450 and 365 MPa respectively. Since E-6022 electrodes are for single-pass welding, the elongation and yield measurement is not necessary.

*Upon agreement between the supplier and the purchaser classified as E7018 may be supplied to a minimum Charpy-V notch impact requirement of 27 J at - 46°C. Such electrodes shall be identified as E7018-1.

*Letters in brackets indicate equivalent ISO 2560 symbols for types of covering.

** The standard refers to D + as reverse polarity and D — as straight polarity and A as a. c. f Electrodes of the E6022 classification are for single-pass welds.

Chemical composition limits for weld-metal as per AWS-A5.1

— For electrodes E6010, E6011, E6012, E6013, E6020, E6022, E6027, no specific chemi­cal limits are given.

AWS Chemical composition

E7028, E7048

Note: For obtaining above chemical composition dc en should be used.

The total of all elements for E7018, E7027 shall not exceed 1.75 except for silicon and in the case of other six electrodes it shall not exceed 1.5 except for silicon.

Apparently, ISO 2560 and the various national standards based on it have put forward a universal coding system, in which all possible electrodes could fit. The AWS standard has, on the other hand, considered the types which are in general industrial usage in the U. S.A. and then brought out a system to fit them.

AWS A5.1 has provided description of electrode classification in the Appendix. Follow­ing are the extracts:

E6010-high cellulose sodium

E6010 electrodes are characterised by a deeply penetrating, forceful, spray type arc and readily removable, thin friable slag, which may not seem to completely cover the deposit. Fillet welds are usually relatively flat in profile and have a rather coarse, unevenly spaced ripples. The coverings are high in cellulose, usually exceeding 30% by weight. The other materials generally used in the covering include titanium dioxide, metallic deoxidisers such as ferromanganese, various types of magnesium or aluminium silicates, and liquid sodium sili­cate as a binder. These electrodes are recommended for all-position work, particularly on mul­tiple pass applications in the vertical and overhead positions and where weld of radiographic soundness are required. These electrodes have been designed for use with direct current, re­verse polarity. The maximum amperage that can generally be used with the larger sizes of these electrodes is limited in comparison to that for other classification due to the high spatter loss that occurs with high amperage.

E6011-high cellulose potassium

E6011 electrodes are designed to duplicate the usability characteristics and mechanical properties of the E6010 classification, using AC. Although also usable with DC, reverse polarity, a slight decrease in penetration will be noted when compared to the E6010 electrodes. Penetration, arc action, slag, and fillet weld appearance are similar to those of the E6010 electrodes. The coverings are also high in cellulose content and are designed as the high- cellulose potassium type. In addition to the other ingredients normally found in E6010 coverings, small quantities of calcium and potassium compounds are usually present. High amperage results in high spatter loss.

E6012-high titania sodium

E6012 electrodes are characterised by medium penetration and dense slag which com­pletely covers the bead. The coverings are high in rutile content, usually exceeding 35% by weight. 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 direct current, straight polarity. Fillet welds tend to be convex in profile with a smooth, even ripple in the horizontal position, and a widely spaced convex ripple in the vertical position, which becomes smoother and more uniform as the size of the weld is in­creased. The E6012 electrodes are all-position electrodes. Their ease of handling, good fillet weld profile, and ability to bridge gaps under conditions of poor fitup and to withstand high amperages make them very suited to this type of work. Weld metal from these electrodes is generally lower in ductility and may be high in yield strength.

E6013-high titania potassium

E6013 electrodes, although very similar to the E6012 electrodes, have distinct differ­ences. Their slag system promotes better slag removal and a smoother arc transfer than E6012 electrodes. E6013 electrodes were designed specifically for light sheet-metal work. However, the larger diameters are used on many of the same applications as E6012 electrodes and pro­vide similar penetration. Coverings of E6013 electrodes contain rutile, cellulose, ferro-manga - nese, potassium silicate as a binder, and other siliceous materials. The potassium compounds permit the electrodes to operate with alternating current at low amperage and low open-cir - cuit voltages. E6013 electrodes are all-position electrodes and are similar to the E6012 elec­trodes in operating characteristics and bead appearance. The arc action tends to be quieter and the bead surface smoother with a finer ripple. In addition, the weld metal is definitely freer of slag and oxide inclusions than E6012 weld metal and gives better radiographic sound­ness.

E7014-iron powder, titania

E7014 electrode coverings are similar to those of E6012 and E6013 electrodes, but with the addition of iron powder for obtaining higher deposition rates. The covering thickness and the amount of iron powder in it are less than for E7024 electrodes. The iron powder also per­mits the use of higher amperage than are used for E6012 and E6013 electrodes. The amount and character of the slag permit E7014 electrodes to be used in all positions. Typical weld beads are smooth with fine ripples. Penetration is approximately the same as that obtained with E6012 electrodes which is advantageous when welding over gaps due to poor fit-up. The profile of fillet-welds tends to be flat to slightly convex. The slag is easily removed. In many cases it removes itself.

E7015-low-hydrogen sodium

E7015 electrodes are low-hydrogen electrodes to be used with direct current, reverse polarity. Their slag is chemically basic. E7015 electrodes are commonly used for making small welds on heavy sections, since they are less susceptible to cracking. They are also used for welding high sulphur and enameling steels. The arc of E7015 electrodes is moderately penetrating. The slag is heavy, friable, and easy to remove. The weld beads are convex, although fillet welds may be flat. E7015 electrodes are used in all positions up to 4 mm size. Larger electrodes are used for groove welds in the flat position and fillet welds in the horizontal and flat positions. Amperage for E7015 electrodes are higher than those used with E6010 electrodes of the same diameter. The shortest possible arc should be maintained for best results with E7015 electrodes. This reduces the risk of porosity. The necessity for preheat is reduced; therefore, better welding conditions are provided.

E7016-low-hydrogen potassium

E7016 electrodes have all the characteristics of E7015 electrodes plus the ability to operate on AC. The core wire and coverings are very similar to those of E7015, except for the use of a potassium silicate binder or other potassium salts in the coverings to facilitate their use with AC. Most of the preceeding discussion of E7015 electrodes applies equally well to the E7016 electrodes.

E7018-low-hydrogen potassium, iron powder

E7018 electrode coverings are similar to E7015 coverings except for the addition of a high percentage of iron powder. The coverings on these electrodes are slightly thicker than those of the E7015 and E7016 electrodes. The iron powder in the coverings usually amounts to between 25 and 40% of the covering weight. E7018 low-hydrogen electrodes can be used with either AC or DC, reverse polarity. They are designed for the same applications as the E7015 electrodes. As is common with all low-hydrogen electrodes, a short arc should be maintained at all times. In addition to their use on carbon steel, the E7018 electrodes are also used for dis­similar joints involving highstrength, high carbon, or alloy steels. The fillet welds made in the horizontal and flat positions are slightly convex in profile, with a smooth and finely rippled surface. The electrodes are characterised by a smooth, quiet arc, very low spatter, adequate penetration, and can be used at high travel speeds. Electrodes identified as E7018-1 have the same usability and design characteristics as E7018 electrodes, except that their manganese content is set at the high end of the range. They are intended for use in situations requiring a lower transition temperature than is normally available from E7018 electrodes when used out of position or with high-heat input.

E7048-low-hydrogen potassium, iron powder

Electrodes of the E7048 classification have the same usability, composition, and design characteristics as E7018 electrodes, except that E7048 electrodes are specifically designed for exceptionally good vertical-down welding.

E6020-E6022-high iron oxide

E6020 electrodes have a high iron oxide covering. They produce flat or slightly concave, horizontal fillet and groove welds with either AC or DC, straight polarity. They are character­ised by a spray type arc and a heavy slag, well honeycombed on the underside, which com­pletely covers the deposit and can be readily removed. Medium penetration will be obtained with normal amperages. However, these electrodes are capable of operating at high amper­ages and in that case will penetrate deeply. The E6020 electrodes are generally considered better than all other classifications for deep penetration fillet welds. E6020 electrodes contain manganese compounds and silica in their covering, along with large amounts of iron oxide and sufficient deoxidisers. The slag coverage is so extensive and the slag-metal reaction of such a nature that the electrodes do not normally depend on gaseous protection. Fillet welds tend to have a flat or concave profile and a smooth, even ripple. In many cases the surface of the deposit is dimpled. E6020 electrodes are recommended for horizontal fillet and flat welds, where radiographic soundness is important. Radiographic quality welds can be obtained even with high deposition rates in heavy plates. These electrodes are not usually used on thin sec­tions, because of the higher amperages that are generally used. Electrodes of the E6022 clas­sification are recommended for single pass, high-speed, high current flat and horizontal lap and fillet welds in sheet metal. The weld bead profile tends to be more convex and less uni­form, especially since the welding speeds are higher.

E7024-iron powder, titania

E7024 electrode coverings contain large amounts of iron powder in combination with ingredients similar to those used in E6012 and E6013 electrodes. The coverings on E7024 electrodes are very heavy and usually amount to about 50% of the weight of the electrode. The E7024 electrodes are well suited for making fillet welds. The welds are slightly convex to flat in profile, with a very smooth surface and an extremely fine ripple. These electrodes are char­acterised by a smooth, quiet arc, very low spatter, and low penetration. They can be used with high travel speeds. Electrodes of this classification can be operated on AC or DC, either polar­ity.

E6027-high iron oxide, iron powder

E6027 electrode coverings contain large amounts of iron powder in combination with ingredients similar to those found in E6020 electrodes. The coverings on E 6027 electrodes are also very heavy and usually amount to about 50% of the weight of the electrode. The E6027 electrodes are designed for fillet or groove welds in the flat position with AC or DC, either polarity, and will produce flat or slightly concave, horizontal fillets with either AC or DC, straight polarity. E6027 electrodes have a spray-type arc. They will operate at high travel speeds. Penetration is medium and spatter loss is very low. They produce a heavy slag, which is honeycombed on the underside. The slag is friable and easy to remove. Welds produced with E6027 electrodes have a flat to slightly concave profile with a smooth, fine, even ripple and good wash up the sides of the joint. The weld metal may be slightly inferior in radiographic soundness to that from E6020 electrodes. High amperages can be used, since a considerable portion of the electrical energy passing through the electrode is used to melt the covering and the iron powder it contains. These electrodes are well suited for fairly heavy sections. E7027-high iron oxide, iron powder

E7027 electrodes have the same usability and design characteristics as E6027 electrodes, except that they are intended for use in situations requiring slightly higher tensile and yield strengths than are obtained with E6027 electrodes. In other respects, all previous discussion for E6027 electrodes also apply to E7027 electrodes.

E7028-low-hydrogen potassium, iron powder

E7028 electrodes are very much like the E7018 electrodes. They differ as follows: the slag system of E7028 electrodes is similar to that of E7016 electrodes, rather than E7018 electrodes. E7028 electrodes are suitable for horizontal fillet and flat welding only, whereas E7018 electrodes are suitable for all positions. The E7028 electrode coverings are much thicker. They make up approximately 50% of the weight of the electrodes. The iron content of E7028 electrodes is higher (approximately 50% of the weight of the coverings). Consequently, on horizontal fillet and flat position welds, E7028 electrodes give a higher deposition rate than the E7018 electrodes for any given size of electrode.