Main coating types of stick electrodes.
A stick electrode is not just any stick electrode. In addition to the composition of the core rod material, the coating of the stick electrode for arc manual metal arc welding (MMA welding) plays a special role. It influences the droplet transfer, weld appearance, and suitability of the electrode for certain welding positions. Different substances such as mineral and organic materials, alloying elements, as well as water glass as a binder, are used as coating components. Through the combination of the various base materials, four basic types and several mixed types have been developed over time. The letters used to designate the coating type (type abbreviations) indicate the properties or the main components of the coating.
| Basic types | Mixed types |
| A = acidic coated | RA = rutile-acidic coated |
| B = basic coated | RB = rutile-basic coated |
| C = cellulose coated | RC = rutile-cellulose coated |
| R = rutile coated RR = thick rutile coated |
(A) Acidic coated stick electrodes
The coating of this currently uncommon type of stick electrode is characterised by high iron oxide content and – due to the high oxygen potential – by deoxidising substances (ferromanganese). With a thick coating, the acidic slag causes particularly fine droplet transfer and flat, smooth weld seams. Acidic coated stick electrodes are only limitedly suitable for welding in forced positions and are more sensitive to the formation of solidification cracks than other coating types.
(B) Basic coated stick electrodes
Characteristic of the thick coating of these stick electrodes is the large proportion of alkaline earth carbonates, such as calcium carbonate and fluorspar. To improve the welding properties especially for welding with alternating current, larger amounts of non-basic components such as rutile and quartz may be necessary.
Outstanding properties of basic coated stick electrodes are:
- The notch impact toughness of the weld metal is particularly higher at low temperatures.
- Their crack resistance corresponds to the high metallurgical purity of the weld metal.
- The low hydrogen content ensures low susceptibility to cold cracking (provided the stick electrodes are dry). It is lower than with all other stick electrodes.
- Basic coated stick electrodes are suitable for welding in all positions except vertical down welding. Basic electrodes specially designed for vertical down welding have a particular coating composition.
(C) Cellulose coated stick electrodes
Stick electrodes of this type contain a large proportion of combustible organic substances in the coating, especially cellulose. Due to the intense arc, they are particularly suitable for welding in the vertical down position. They are often used in pipeline construction.
(R) Rutile coated stick electrodes
Stick electrodes of this type produce a coarser droplet transfer than the thick rutile coated ones. They are therefore suitable for welding thin sheets.
Rutile type stick electrodes are suitable for all welding positions – except vertical down welding.
(RR) Thick rutile coated stick electrodes
For stick electrodes of this type, the ratio of coating to core rod diameter is at least 1.6 : 1. Characteristic is the high rutile content of the coating, which results in good re-ignition and fine-scaled, even seams.
(RA) Rutile-acidic coated stick electrodes
The welding behaviour of stick electrodes of this mixed type is comparable to acidic coated ones. Their coating consists of rutile and iron oxide. Therefore, these usually thick coated electrodes can be used for welding in all positions except vertical down welding.
(RB) Rutile-basic coated stick electrodes
Characteristic of the coating of this type are high rutile and increased basic proportions. These usually thick coated electrodes have, in addition to good mechanical properties of the weld metal, good welding properties in all welding positions except vertical down welding.
(RC) Rutile-cellulose coated stick electrodes
The coating of these stick electrodes contains, in addition to rutile, larger cellulose proportions. Stick electrodes of this type can therefore also be used for welding in the vertical down position.
Notes and Tips
- When selecting a welding electrode, observe the manufacturer's specifications regarding the amperage – higher amperage values are suitable for horizontal welding, lower amperage values for vertical welding or overhead welding.
- The electrode manufacturer specifies the polarity with which a particular electrode can or should be used. Refer to the information on the electrode packaging.
- Use the following rule of thumb to select the electrode diameter: Sheet thickness x 0.5 + 1.0 mm = electrode diameter
The following RED by Lorch welding machines are suitable for welding with stick electrodes:
Do you want to read more about electrode welding or get to know the other welding processes?
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