German System of Coding for Electrodes
DIN 1913 (Jan. 1976) Coated Electrodes for the Welding of Unalloyed and Low-alloy Steels
The German coding system is also based on ISO : 2560 with some modifications as in BS 639. It starts with prefix E followed by two digits 43 or 51 indicating the range of tensile
strengths as in ISO, with the addition that minimum yield strength is specified as 360 MPa
and 380 MPa respectively (see Table 4.6).
These two digits are followed by another two digits indicating elongation and impact strength as given in Table 4.8. After this DIN has a departure from ISO 2560 and BS 639. It provides a classification based upon :
(a) coating type
(b) welding position
(c) welding current condition
and then uses the classification number to designate each type of electrode. The details are as follows:
(a) Coating type is indicated by letter or letters as follows
A—acidic B—Basic C—Cellulosic
A—rutile (thin/medium) RR—rutile (heavy coating)
AR—acid-rutile (mixed) R(c) rutile—cellulose (medium coated)
RR(c)—rutile-cellulose (heavy coated)
B(R)—basic coated with non-basic components RR(B)—rutile-basic (heavy coated)
They define :
Thin coated, having a coating factor (CF) of 120% ; medium coated, having a CF of 120-155% and heavy coated having a CF of over 155%.
(b) Welding position
1. all position.
2. all positions except vertical down.
3. butt-weld flat, fillet-weld flat, fillet-weld horizontal.
4. butt-weld flat, fillet weld flat.
(c) Welding current conditions are same as in ISO 2560 and BS 639 except that in case of 0 (zero)
0 means dc only electrode positive or negative polarity
0+ means dc only with electrode positive polarity
0- means dc only with electrode negative polarity
Combining (a), (b) and (c) twelve classifications of electrodes are given in Table 4.9.
This electrode class coding is followed by a three digit number indicating the deposition efficiency, which is to be used only if it is more than 105%. This is identical to ISO 2560 and BS 639.
Table 4.8 First and second digit for elongation and impact strength in DIN 1913
Table 4.9. Classification numbers of electrodes in DIN 1913
4.5.3 Indian Standards System
IS : 815-1974 classification and coding of covered electrodes for metal arc welding of structural steels.
The code starts with a prefix E or R meaning thereby E—electrode produced by solid extrusion R—extruded with reinforcement Next come digits
First digit indicates the type of covering
Table 4.10. First digit for type of covering in IS : 815
Second digit indicates welding position and third digit indicates welding current condition as shown in Table 4.11.
Table 4.11. Second and third digit for welding position and current condition in IS : 815
Fourth and Fifth digits are 41 or 51 indicating tensile strength range in combination with yield stress.
Sixth digit indicates percentage with impact strength as given in Table 4.12.
Table 4.12. Digits indicating mechanical properties in IS : 815
*Upper limit of tensile strength may be exceeded by + 40N/mm2.
The coding terminates with one or more of the following suffixes to be used when appropriate.
Suffix letter Special property
H Hydrogen controlled electrode
J Iron powder covering deposition efficiency 110-130%.
K As J with deposition efficiency 130 - 150.
L As J with deposition efficiency of 150%.
P Deep penetration.
A hydrogen controlled electrode gives a weld deposit that gives not more than 10 ml of diffusible hydrogen/100 g weld deposit. Appendix A gives types of flux coverings according to DIN, 1913, IS : 815 and AWS.
Types of Flux Covering
IS : 815 describes the standard flux coverings as follows :
Type 1: Electrode with covering having a high cellulose content.
The covering contains at least 15% of material having a high cellulose content and up to 30% of titania (as rutile or titanium white). This type of electrode is characterised by a deep penetrating arc and rapid burn-off rate. Spatter loss is somewhat higher than that with electrodes having the mineral type of covering. A voluminous gas shield is formed as a result of the decomposition of the cellulosic material in the arc region. The weld finish is somewhat coarser than usual, the ripples being rather more pronounced and less evenly spaced. The deposit has a thin cover of slag, which is friable and thus easy to remove. Because of its arc characteristics and the small volume of slag produced, the electrode is particularly easy to use in any welding position. With current values near to the maximum of the range, the electrode may be used in the flat position for deep-penetration welding. The electrode is suitable for all types of mild steel welding and is of particular value for applications involving changes in position of welding, for example, in pipe welding, storage tanks, bridges and ship building. Generally, this type of electrode is suitable for use with DC with the electrode connected to the positive pole. Some types are available which contain arc stabilising materials and are suitable for use with AC.
Type 2: Electrode with covering having a high content of titania and producing a fairly viscous slag.
The covering contains a high proportion of titania (as rutile, titanium white or ilmenite) and the high content of ionisers provides excellent welding properties. An electrode of this type is suitable for butt and fillet welds in all positions and is particularly easy to use for fillet welds in the horizontal-vertical position. Sizes larger than 5 mm are not normally used for vertical and overhead welding. Fillet welds tend to be convex in profile and have medium root penetration. The electrode has smooth arc characteristics and normally produces very little spatter. The slag is dense and completely covers the deposit and is easily detached, except from the first run in a dc ep V-groove. The electrode is particularly suitable for use with AC, and on DC it may be used with the electrode connected to either pole.
Type 3: Electrode with covering containing an appreciable amount of titania and producing a fluid slag.
The covering contains an appreciable amount of titania (as rutile, titanium white or ilmenite), but the addition of basic materials yields a much more fluid slag than produced by electrodes of Type 2. Welding in the overhead and vertical (upwards) position is far easier with this type of electrode than with any other type of mild steel electrode, but its use is not confined to these positions. The electrode has smooth arc characteristics, medium penetration, and normally produces very little spatter. The slag is generally easy to detach, even from the first run in a deep V-groove. The deposit produced by this type of electrode will usually meet normal radiographic tests more readily than the one made with electrodes of Type 2. The electrode is suitable for use with AC and DC and may be used with the electrode connected to either pole.
Type 4: Electrode with covering producing an inflated slag and having high content of oxides and/or silicates of iron and manganese.
The covering consists principally of oxides or carbonates of iron and manganese, together with silicates. The electrode is generally produced with a thick covering and is used for welding in the flat position only. Certain varieties have a thinner covering, and these may be used for welding in all positions but have generally been superseded by other types of electrodes. Both the forms of covering produce a fluid, voluminous slag which freezes with a characteristic internal honeycomb of holes, the so-called inflated slag, which is very easily detached. The weld finish is smooth, the ripples being much less pronounced than on deposits produced by the other types of electrodes. In grooves and fillet welds, the weld profile is concave. The principal application for this type of electrode with a thick covering is for deep groove welding in thick plates, particularly where such welds are subject to strict radiographic acceptance standards. Certain varieties of this type of electrodes are suitable for deep penetration welding. The electrode is suitable for use with DC, usually with the electrode connected to the positive pole, and may be used on AC.
Type 5. Electrode with covering having a high content of iron oxides and/or silicates producing a heavy solid slag.
This type of electrode has a thick covering, consisting principally of iron oxides with or without oxides of manganese. An electrode of this type is used principally for single run fillet welds, where appearance is of primary importance. The covering melts with a pronounced cupped effect at the electrode tip, enabling the electrode to be used touching the work, this procedure being known as touch welding. The degree of penetration is low. A heavy solid slag is produced which is sometimes self-detaching, and in fillet welds, gives a smooth, concave weld metal has low carbon content and a particularly low manganese content. This type of electrode has been used with some success for the welding of certain high tensile steels and also steels having a higher content of sulphur than those used for structural welding, but on such steels the weld profile may be more irregular. Weld metal deposited by this type of electrodes usually has low mechanical properties, the reduction of area and Izod impact values being generally less than the values normally specified. The electrode is particularly suitable for use with AC and DC and may be used with the electrode connected to either pole.
Type 6: Electrode with covering having a high content of calcium carbonate and fluoride.
The covering of this electrode contains appreciable quantities of calcium carbonate and fluoride. The slag is fairly fluid and the deposit is usually convex to flat in profile. This class of electrode is generally suitable for welding in all positions. Electrodes of this class are also known as basic coated, and have the advantage of being particularly suitable for welding medium and high tensile structural steels and other applications, where high mechanical properties and maximum resistance to cracking are required. They are also used for welding steels having higher carbon and sulphur contents than normal structural steels. During manufacture, these electrodes are baked at a high temperature and to obtain the best results they should be properly stored, and if necessary, thoroughly dried to the manufacturer’s recommendations before use. In welding with these electrodes, it is necessary to use a short arc and the correct electrode angle to achieve maximum soundness in the weld deposit. Properly used in this way, the electrode will produce welds to high radiographic acceptance standards. Most of the electrodes recently developed can be used with AC but with some types DC is preferred, in which case the electrode should be connected to the pole recommended by the manufacturer. Coatings of this type are commonly used for electrodes dopositing high tensile and alloy weld metals.
Note: The addition of metal powder to any of the above types of covering may affect the characteristics described above.