Manual arc welding is widely used. It is easy to use, does not require a large number of specialized devices, and the welding equipment used is very portable. This means it can be used practically anytime and anywhere.
What is the principle behind manual arc welding?
The principle behind manual arc welding is very simple. An arc generates heat, which melts the materials, and these materials then join the workpieces into a single unit. The electrode itself slowly melts away during the process and acts as the filler material, while the electrode’s coating provides the shielding gas. The process is also versatile in terms of current, as it can be performed using either direct current or alternating current.
The arc burns between the workpiece and the coated rod electrode, which is guided by hand. This allows materials with a thickness of 1.5 mm or more to be joined without difficulty. This applies to unalloyed, low-alloy, and high-alloy steels. The melting rate can reach up to 3 kg per hour.
| Characteristic | Value / Description |
|---|---|
| Heat source | Electric arc between the electrode and the workpiece |
| Filler material | Coated rod electrode (melts away on its own) |
| Inert gas | From the electrode coating (no shielding gas connection required) |
| Type of Electricity | Direct or alternating current (direct current preferred) |
| Material thickness | 1.5 mm and up |
| Materials | Unalloyed, low-alloy, and high-alloy steels |
| Melting capacity | Up to 3 kg per hour |
What welding accessories are available for manual arc welding?
Although both direct current and alternating current can be used, direct current is preferred. Welding power sources, welding transformers, welding rectifiers, inverters, and welding converters are used as power sources. The current should be 250 amperes. This allows for a duty cycle of 60 % and enables the use of electrodes with a core rod diameter of 5 mm.
In addition to the length and diameter of the electrode, the thickness of the base material and the desired type of weld also limit the current that must be set. Each electrode comes with specifications regarding the load it can handle.
The circuit requires power cables, a ground clamp, and an electrode holder. The welder holds the electrode holder in his hand. Therefore, it must be easy to handle and allow for quick and, above all, safe clamping of the electrode. The electrode holder must also be insulated.
The power cables must have a cross-sectional area that ensures a low voltage drop but is also capable of handling the current. As for the connections, it is crucial that they are clean and securely fastened. The ground clamp is used to connect the workpiece to the current conductor.
What are the different types of electrodes used in manual arc welding?
The rod electrodes used are coated. They consist of a core wire covered with a mineral coating that has been applied to the core wire using a binder. When using unalloyed rod electrodes, their selection is based on their properties in terms of strength and toughness. They must be less hard than the base materials within the heat-affected zone of the molten pool.
With high-alloy rod electrodes, on the other hand, it is important that their grade matches that of the base material. When dealing with stainless steels, the percentages of chromium and nickel—as well as titanium and carbon—must be taken into account.
Welding electrodes are classified as thin, medium, and thick. The thickness used depends on the material joint and the welding position. For alloyed and high-alloy steels, the only distinction is between basic-coated electrodes and rutile electrodes (acidic). For other steels, the following types of coatings are used:
Type C – Cellulose Electrodes
Type C stick electrodes are coated with cellulose. This makes them particularly suitable for welding in vertical-down positions. The coating contains organic substances, primarily cellulose. They are used to weld pipes and large pipelines. The welding speed is very high, as evidenced by the high melting rate and rapid penetration. Very coarse droplets form from the material, which are well-suited for bridging gaps. The resulting welds are coarse and scaly. However, using a Type C electrode requires a high arc voltage, which means it cannot be used with every welding machine.
Type RA – Rutile-based electrodes
RA-type electrodes, or rutile-acid rod electrodes, are characterized by a very high current-carrying capacity. This enables them to deliver a high deposition rate. At the material interface, they produce fine droplets, resulting in concave and smooth welds. This makes it easy to access the root of the weld in fillet welds. Their low silicon content simplifies subsequent galvanizing, rubber coating, or enameling. The slag produced when welding with this electrode can be easily removed after the job is complete.
Type R and RR – Rutile Types
The rutile-type stick electrodes are used for thin sheet metal. They can be used in all welding positions except the vertical-down position. The droplet transfer for R electrodes is coarser than that for the thicker-coated RR electrodes. The RR type produces fine-scaled, uniform surfaces from which the slag can be easily removed.
Type RC – Rutile-cellulose electrodes
The rutile-cellulose electrode produces a very viscous molten pool during welding. The cellulose content reduces slag formation. This makes this type of electrode suitable for welding vertical and fillet welds in metal fabrication. It is primarily used in assembly work because of its versatility.
Type RB – Rutile-based electrodes
The rutile-based electrode type produces a weld pool with medium-sized droplets. This results in good strength and toughness properties. It also offers excellent positional weldability. Thanks to its high deposition rate, this electrode is therefore frequently used in pipeline construction and structural steelwork, particularly for root passes and forced-position welding.
Type B – Basic Electrodes
Basic Type B electrodes are characterized by high crack resistance. This is particularly true when welding in low-temperature environments. These basic electrodes are especially suitable for steels with thick walls or for steels that are not well-suited for welding. The weld bead is formed with coarse droplets. Welding can also be performed in all positions except the vertical-down position.
| Type | Envelope | Drop Transition | Typical Applications | Distinctive Feature |
|---|---|---|---|---|
| C | Cellulose | Rough | Pipes, large pipelines, vertical seams | Very high welding speed; high arc voltage required |
| RA | rutile acid | Fine | Fillet welds, galvanizing/enameling afterward | High current-carrying capacity; easy slag removal |
| R / RR | Rutile (thin/thick) | Coarse (R) / Fine (RR) | Thin sheets, all positions except for the vertical seam | RR: fine-grained, uniform surfaces |
| RC | Rutile cellulose | Medium | Assembly work, fillet welds, vertical welds | Versatile; produces little slag due to its cellulose content |
| RB | Rutile-based | Medium-sized | Pipeline Construction, Steel Construction, Root Passes | Good toughness; high melt-off rate |
| B | Alkaline | Rough | Thick-walled steel, low-temperature applications | High crack resistance; hygroscopic — must be allowed to dry out |
How does the manual arc welding process work?
The welding process begins when the electrode makes contact with the workpiece. This ignites the arc between the two. For basic electrodes, a sweeping motion is recommended instead of a light tap. The ignition point on the workpiece must be within the welding area.
The electrode should be held at a 45° angle in the direction of welding. The length of the arc should be approximately equal to the diameter of the electrode’s core. There is an exception for basic electrodes: In this case, the arc should be kept shorter—half the diameter of the electrode’s core is recommended as a guideline.
For this movement, the work is performed using the straight-stitch technique. In some cases, welding may also be performed using a slow, dragging motion with a slight back-and-forth motion. In ascending seam positions, however, one must always use a back-and-forth motion with the electrode held in a vertical position.
Welding Current – Calculation and Rule of Thumb
The welding current affects the melting rate and penetration. The voltage adjusts automatically based on the current source. The maximum current that can be set depends on the selected electrode and its load limit. If the current is set too high, the electrode becomes too hot and its coating either cracks or burns out. However, a minimum current is also required for the electrode to burn off.
Rule of thumb: Calculating welding current
- Electrode length 250–350 mm: Current = 20–40 × electrode diameter
Example: Ø 2.0 mm → 40–80 amperes - Electrode length of 350 mm or more: Current = 30–50 × electrode diameter
- Electrode length 450 mm or longer, Ø 6 mm: Current = 35–60 × diameter
Example: 35–60 × 6 mm → 210–360 amperes
Note: The lower values apply to root passes and forced positions. The upper values apply to fill and cap passes, as well as PA and PB welding. For high-alloy materials, the current must be reduced.
What are the common mistakes in manual arc welding, and how can they be avoided?
There are various sources of error in manual arc welding. However, these can be avoided by following the correct procedure.
Bubble Formation (Magnetic Bubble Effect)
When welding with direct current, bubbles may form. These are slag inclusions, result from incomplete penetration, or insufficient penetration. All of these defects can be attributed to magnetic fields, which can interfere with consistent welding. This causes the arc to be deflected.
Magnetic fields are generated, for example, by large masses of steel. This causes the arc to be deflected toward the mass. Tilting the electrode helps counteract this. Deflection can also be prevented or compensated for by adding extra steel mass or relocating the connection point.
The Re-drying of Basic Electrodes
Alkaline electrodes have a hygroscopic effect—they absorb water. This produces hydrogen, which is trapped in the weld metal and can cause cracks. Therefore, it is important to store the electrodes properly. They can also be dried by heating them to 250 to 350 °C for 30 to 120 minutes. Always follow the manufacturer’s instructions.
Defective Welds – Causes and Solutions
| Error Type | Causes | Solution |
|---|---|---|
| Burn marks | Current too high, electrode angle too steep, arc too long | Reduce the current, adjust the electrode angle and arc length |
| Slag inclusions | Excess slag, insufficient current, excessive welding speed | Completely remove the slag; adjust the current and speed |
| Gas inclusions / Pores | Contaminated workpiece surface, damp electrode coating, arc too long | Clean the surface; store the electrodes in a dry place or pat them dry |
| Terminal crater | Electrode withdrawn from the melt too quickly | Slowly withdraw the electrode and fill the crater neatly |
| Shrinkage Cracks | Excessive current, poor-quality materials, too rapid cooling | Reduce the current, preheat the workpiece, and allow it to cool slowly |
| Root error | Excessive face-to-face distance, slag ingress into the root area | Select the correct end face clearance; weld the root pass carefully |
How important is occupational safety in manual arc welding?
Manual arc welding is a manual process. During this process, the welder is exposed to specific risks, making appropriate occupational safety measures essential.
1. Protection from Radiation
Radiation can be divided into three types: visible light, infrared light, and ultraviolet radiation. Welding shields provide good protection against both visible and invisible light rays. Alternatively, welding helmets or automatic protective helmets with appropriately tinted lenses can be used. Work clothing must provide UV protection against glare.
2. Protection against slag and weld spatter
Another source of danger is pieces of slag that fly off—these can cause eye injuries in particular. In addition, welding spatter can obstruct vision. Safety goggles with side protection or clear-view shields help protect against both.
3. Protection against gases and smoke
The gases and smoke produced during welding pose another source of risk. Depending on the electrode used, these gases can be inert, toxic, or even carcinogenic. Therefore, when working indoors, it is important to ensure that the area is well ventilated and that the air in confined spaces is extracted to keep exposure levels below the permissible concentration.
4. Protection Against Electric Shock
Then there is the electrical current itself. Even without an arc, the current is present as open-circuit voltage in the workpiece and the welding cable. It is also present between the jaws of the electrode holder, at the terminal, and in the workpiece cable. Any contact can result in electric shock, which can be fatal. Therefore, shoes with adequate insulation, appropriate work clothing, and leather gloves must be worn.
| Source of danger | Risk | Protective measure |
|---|---|---|
| UV/IR radiation, electric arc | Eye and skin damage, flash blindness | Welding shield / automatic helmet with protective glass; UV-protective clothing |
| Slag & Droplets That Fly Off | Eye injuries, burns | Safety glasses with side shields, clear lens |
| Welding Fumes & Gases | Respiratory damage, toxic/carcinogenic gases | Good room ventilation, exhaust system in confined spaces, respiratory protection |
| Electric Current (Open-Circuit Voltage) | Electric shock, life-threatening | Insulated shoes, leather gloves, appropriate protective clothing |
FAQ: Frequently Asked Questions About Manual Arc Welding
An electric arc burns between the coated rod electrode and the workpiece. The heat generated by this process melts both materials and fuses them into a single unit. The electrode itself melts away during the process and serves as filler material; its coating generates the shielding gas. The process works with either direct or alternating current and is suitable for material thicknesses of 1.5 mm or more.
Direct current produces a more stable arc than alternating current and allows for better control of the welding process. It reduces the magnetic blow effect with many electrodes and improves seam quality. Welding power sources, welding rectifiers, and inverters are used as power sources. The recommended current is typically 250 amperes, which allows for a duty cycle of 60 %.
Type C (cellulose): Pipes and vertical seams, very high welding speed. Type RA (rutile-acid): Fillet welds, followed by galvanizing or enameling. Type R/RR: Thin sheets, all positions except vertical down-welds. Type RC (rutile-cellulose): General-purpose, assembly work, low slag formation. Type RB (rutile-basic): Piping and structural steelwork, root passes. Type B (basic): Thick-walled steels, low-temperature welding, high crack resistance.
As a rule of thumb: For an electrode length of 250–350 mm, the current is 20 to 40 times the electrode diameter (e.g., Ø 2 mm → 40–80 A). For lengths of 350 mm or more, the factor is 30–50; for lengths of 450 mm or more and a diameter of 6 mm, the factor is 35–60 (i.e., 210–360 A). The lower values apply to root passes and constrained positions; the upper values apply to fill and cover passes. Always reduce these values for high-alloy materials.
Basic electrodes have a hygroscopic (water-attracting) effect. Moisture absorbed by the electrodes is converted into hydrogen during welding, which accumulates in the weld metal and can lead to hydrogen cracks—a particularly dangerous phenomenon in high-strength steels. To prevent this, the electrodes are dried for 30 to 120 minutes at 250 to 350 °C. The manufacturer’s instructions on the packaging are binding.
At a minimum: a welding shield or automatic helmet with tinted protective glass (UV and IR protection), UV-protective work clothing, safety goggles with side shields to protect against flying slag, leather gloves, and insulated safety shoes to protect against electric shock. In enclosed spaces, a high-performance exhaust system is absolutely necessary, as welding fumes may contain toxic or carcinogenic gases depending on the electrode.