CHOOSING THE RIGHT ELECTRODE FOR YOUR NEEDS
It is important to consider both materials and technical aspects when selecting stick electrodes.
Type, Name, Definition
R, RR, Rutile:
Standard electrode for universal use, fine to medium droplet transfer, good mechanical properties, welding positions PA, PB, PC, PE, PF, (PG limited use only).
Use as a combination of achievable, high toughness values and universal use with increased demands on the welder and the seam finishing work.
Use for the requirement of high mechanical properties, average to coarse droplet transfer, poorly detaching slag, possible in all positions, please allow for redrying of the electrodes.
Used as a replacement for rutile electrodes, to make welding position PG safer, less slag formation, higher demands on the welder and the finishing work.
Used mainly for the root pass on pipe connectors (pipeline welding) in position PG, good mechanical properties, average globules, almost no slag
SELECTION ACCORDING TO TECHNICAL ASPECTS
Each type of electrode has very specific welding properties, making them suitable for certain welding tasks.
CELLULOSE ELECTRODE (C)
Cellulose electrodes (C) are well suited for vertical down welding (position PG), so they are chosen for welding circumferential seams on large-diameter pipes. Pipelaying is the preferred field of use. Compared to welding in the vertical up position (PF), relatively thick electrodes (4 mm) may be used even for the root pass. This has economic benefits. The advantage of the rutile-acid mixed type (RA) is the slag residue in narrow gouges, where a compact slag is pinched and is difficult to remove. The slag produced by the RA type is itself porous and breaks into small pieces under the chipping hammer, making it easy to remove.
RUTILE ELECTRODE (R, RR)
The special characteristics of rutile electrodes (R, RR), i.e. good re-ignition properties, the ease of removing slag, and good seam appearance, determine how they are used. Preferred applications include fillet welds and final passes, whereby complete removal of slag and good seam appearance are important.
RUTILE-CELLULOSE TYPE (RC)
The rutile-cellulose type (RC) may be used in all positions, including vertical-down welds. This makes it suitable for universal use, especially installation applications. The thick-coated version, which fulfills high expectations with respect to seam appearance, is therefore frequently considered to be an all-round electrode, especially at small companies.
RUTILE-BASIC ELECTRODE (RB)
Due to its somewhat thinner coating and special characteristics, the rutile-basic electrode (RB) is particularly well suited to root passes and welding in the PF position. For this reason, small and medium-diameter pipe construction is a preferred field of application for RB electrodes.
BASIC ELECTRODE (B)
The basic electrode (B) is suitable for welding in all positions. Special types are even appropriate for vertical down welding. Seam appearance is somewhat less desirable than other types. However, the weld metal has other benefits. Of all electrode types, basic electrodes have the best toughness and the best crack resistance of the weld metal. For this reason, this type is used whenever the welding suitability of the parent metals is a challenge, such as steel types that have limited weldability or with thick-wall materials. Basic electrodes are also chosen when tremendous toughness is required, such as on structures that will later be subjected to low temperatures. Its low hydrogen content makes this type particularly well suited for welding high tensile stainless steels.
SELECTION ACCORDING TO MATERIAL ASPECTS
In general, the strength and toughness of the parent metal also be achieved in the weld metal. The full designation of a stick electrode according to DIN EN ISO 2560-A also contains information on the minimum values for yield strength, tensile strength, and toughness of the weld metal as well as a few welding characteristics, making it easier to select the right electrode.
Looking at the brief designation of E 46 3 B 42 H5, for example, we can decipher the following: The stick electrode for MMA welding (E) has a yield strength of at least 460 N/mm2, a tensile strength between 530 and 680 N/mm2, and a minimum elongation of 20 % (46). Impact energy of 47 J is achieved to a temperature of -30 °C (3). The electrode is basic-coated (B). This is followed by optional information on metal recovery and suitable current for the electrode. The stick electrode in the example has metal recovery of 105 % to 125 %, maybe welded using direct current only (4), and is suitable for all positions with the exception of vertical-down (2). The hydrogen content of the weld metal is below 5 mL/100 g/weld metal (H5). If the weld metal contains alloy elements other than manganese, this will be indicated before the coating type code using the code for the chemical elements and sometimes with figures for the percentage content (for example 1Ni).
Having a low hydrogen content is important when welding steels that tend to form hydrogen-induced cracks, such as high tensile steel. In these cases, the code for hydrogen content provides the necessary information.
Similar designation systems are also used for high tensile electrodes (DIN EN ISO 18275), creep-resistant electrodes (DIN EN ISO 3580-A), as well as for stainless electrodes (DIN EN ISO 3581-A). In cases of creep-resistant and stainless electrodes, creep-resistance properties or corrosion properties, respectively, of the weld metal must also match those of the parent metals in addition to strength properties. That is the reason for the rule that the weld metal should be as close as possible to the same type as the parent metal or be somewhat higher alloyed.