Basic knowledge of welding rods

When a beginner hears of a welding rod, he may simply think of it as one type of tool. In fact, however, there are many different types of welding rods. Let us explain how many types there are and by what criteria they are classified, so that beginners can understand them.

No.1: Types of Welding Rods

The correct term for 'welding electrode' is 'covered arc welding electrode. The type of welding rod is distinguished by the type of flux (coating agent), such as slagging agent or gas generator agent, used in the center portion when the covered arc welding rod is welded. The fluxes are divided into four major series, such as 'illumininite,' 'lime-titania,' 'low-hydrogen,' and 'high-titanium-oxide' fluxes. According to these, welding rods are also classified into each of the four types.

No.2: Role of Coating Material 

When arc welding using welding rods, the combined action generated by the melting of the coating agent creates a shield over the weld, which improves the finish and maintenance of the weld. In more detail, the presence of the covering agent facilitates the generation of an arc, which allows the arc to be generated consistently. It also prevents oxygen and nitrogen from the atmosphere covering the molten metal from entering the weld metal when gas is generated. The slag generated also improves the appearance of the bead and slows the cooling rate. The slower cooling rate facilitates welding in various positions. The composition of the coating agent forces the removal of oxygen as slag, which allows for deoxidization and cleaning. In addition, alloying elements can be added to achieve the desired performance.

Types of Welding Rods #1: Illuminite Type

Illuminite type is a type of welding rod whose main raw material is a mineral consisting of a combination of titanium and iron oxides. The advantages are good slag flowability, good melting-in, and good mechanical properties. The disadvantage is the high hydrogen content, making it unsuitable for thick plates and structures with large restraints. This illuminite series was developed uniquely in Japan, and it can be said that it is a type of series that is not yet seen in many other countries. For example, Kobe Steel's 'B series,' including 'B-10,' 'B-14,' and 'B-17,' are included in this series. For example, the G series of welding rods, such as 'G-200' and 'G-300' by Nittetsu Corporation, are included in this category.

Welding Rod Type 2: Lime Titania Type

Lime titania-type welding rods are mainly made of lime and titanium (titanium dioxide) as the main raw materials. Advantages are mild arc, good slag flow, and easy vertical advance welding due to its porous nature. The disadvantage is inferior resistance to radiation penetration tests. For example, Z-44 by Kobe Steel, NS-03Hi by NITTETSU, and LC-3 and LC-08 by NIKKO are typical brands.

Welding Rod Type 3: Low-hydrogen type

Low-hydrogen type refers to welding rods whose main raw materials are calcium carbonate and calcium fluoride, and which are mainly used as coating materials. Advantages are the lowest hydrogen content in the weld metal, strong deoxidizing action and low oxygen content, resulting in very good X-ray performance, mechanical properties and welding workability of the weld metal. The disadvantage is that it is susceptible to moisture, so it must be kept at least 10 cm away from floors and walls, and it must be stored in a well-ventilated place. For example, Kobe Steel's LB-26 and LB-52U LB series are included in this category. For example, S-16 by NITTETSU SUMIKIN and LS-16 by NIKKOH LUMEI are typical brands.

Welding Rod Type 4: High Titanium Oxide Type

Titanium oxide-based welding rods are mainly made of titanium oxide as the main raw material for the coating agent. The advantage of this type of welding rod is that it can provide a shiny bead appearance due to shallow penetration. It is suitable for welding thin plates and light structures where appearance is important. The disadvantage is that it is inferior in mechanical properties, so it is not often used for welding major parts. For example, 'B-33' from Kobe Steel, 'S-13Z' from Nittetsu Sumikin, and 'SK-260' from Nikko Lazer are typical brands.


Illuminite type

lime titania type

low hydrogen type

high titanium oxide type

Blend in

Bead growth

Bead appearance


Difficult to work