Stick Welding Arc Blow: Causes and Solutions for Magnetic Arc De

Understanding Arc Blow in Stick Welding

Arc blow is a phenomenon where the welding arc is deflected from its intended path by magnetic forces. This deflection can cause the arc to wander, keyhole to one side, or even extinguish entirely. Arc blow is particularly problematic in DC welding, where the unidirectional current creates strong magnetic fields that interact with the arc plasma.

The problem occurs when magnetic fields surrounding the arc become unbalanced, creating forces that push the arc away from the intended direction. This unbalance typically happens near the ends of joints, at corners, or when welding near other magnetic materials. The arc is literally blown by magnetic forces, hence the name.

Arc blow frustrates welders, reduces quality, and can make welding impossible in severe cases. Understanding the causes and solutions for arc blow helps welders manage this challenging phenomenon and maintain productivity.

Causes of Arc Blow

Magnetic Field Unbalance

The fundamental cause of arc blow is unbalanced magnetic fields around the welding arc. When current flows through the workpiece, it creates circular magnetic fields according to the right-hand rule. Under ideal conditions, these fields are balanced and don't affect the arc.

Unbalance occurs when:

• The arc is near the end of a joint, creating asymmetrical current paths
• Welding near corners or complex geometries
• Current returns through a path that creates interfering fields
• Welding on materials with residual magnetism
• Working near other magnetic fields or equipment

The magnetic force on the arc plasma is proportional to the magnetic field strength and current. Higher currents create stronger arc blow effects.

Workpiece Geometry Effects

Workpiece geometry significantly affects arc blow severity. The worst arc blow typically occurs at the ends of joints where current paths become asymmetrical.

At the start of a joint, current must flow around the end to complete the circuit, creating a magnetic field that pushes the arc backward. At the end of a joint, current concentrates at the corner, creating fields that push the arc forward off the joint.

Complex geometries with multiple current paths create complex magnetic field patterns that can deflect the arc unpredictably. Large structures with long current paths are particularly susceptible.

Residual Magnetism

Materials that have been magnetized by previous welding, magnetic particle inspection, or exposure to magnetic fields retain some residual magnetism. This residual field adds to the field created by welding current, potentially causing severe arc blow.

High-carbon steels and some alloy steels are more easily magnetized than low-carbon steels. Materials that have been in magnetic particle inspection equipment are particularly prone to residual magnetism issues.

Recognizing Arc Blow

Symptoms of Arc Blow

Arc blow manifests in several observable ways:

Arc Deflection: The most obvious symptom is the arc visibly bending or wandering from its intended path. The arc may point toward one side of the joint or wander unpredictably.

Keyhole Deflection: With cellulose electrodes, the keyhole may form off-center or elongate in the direction of arc deflection. This causes uneven penetration and potential lack of fusion.

Excessive Spatter: Arc blow often increases spatter as the arc becomes unstable. The deflected arc may contact the workpiece at unfavorable angles, causing explosive metal transfer.

Undercut: Arc blow that pushes the arc to one side can cause undercut on that side of the joint. The arc concentrates heat on one side while the other side receives insufficient fusion.

Arc Extinguishing: Severe arc blow can extinguish the arc entirely as the deflection takes the arc beyond sustainable conditions.

When Arc Blow Occurs

Arc blow is most likely to occur:

• At the beginning and end of welds
• In corners and complex joints
• On thick materials with high current
• Near ground connections
• When welding on magnetized material
• In DC welding (AC is less susceptible)

Recognizing these situations helps welders anticipate and prepare for arc blow problems.

Solutions for Arc Blow

Work Connection Strategies

Work connection (ground) placement significantly affects arc blow. The current return path creates magnetic fields that interact with the arc.

Start Block Technique: Attach a steel block at the beginning of the joint and connect the work lead there. Start the arc on the block, then move onto the joint. This eliminates starting arc blow by moving the problematic geometry outside the weld area.

Run-off Tabs: Attach tabs at the end of the joint that extend beyond the weld termination point. Weld onto the tab before breaking the arc, avoiding the arc blow at the joint end.

Multiple Work Leads: For long joints, use multiple work leads connected at intervals along the joint. This distributes current return and reduces magnetic field strength at any point.

Work Lead Positioning: Place the work lead to create favorable magnetic fields. Experiment with different positions to find what works best for your specific geometry.

Welding Technique Adjustments

Short Arc Length: Maintain a shorter arc than normal. The shorter arc is less affected by magnetic deflection and more controllable.

Angle Adjustment: Angle the electrode to counteract arc blow. If the arc blows to the right, angle the electrode slightly to the left. This compensation helps direct the arc where needed.

Backstep Welding: Weld in short segments back toward the completed weld. This technique can reduce arc blow by changing the current path geometry.

Reduced Amperage: Lower amperage reduces magnetic field strength and arc blow severity. The trade-off is reduced penetration and deposition rate.

Process Changes

Switch to AC: If possible, switch from DC to AC welding. The alternating current creates alternating magnetic fields that largely cancel out, significantly reducing arc blow. E6011 electrodes work on AC and can replace E6010 for many applications.

Reduce Current: Lower amperage reduces magnetic effects. If the application allows, reduce current and compensate with slower travel or multiple passes.

Demagnetization: For materials with residual magnetism, demagnetization may be necessary. This can be done with AC coils, specialized demagnetizers, or by heating above the Curie temperature (about 1414°F for steel).

Joint Design Modifications

Start and Run-off Tabs: Design joints with tabs at both ends for starting and stopping. Remove tabs after welding.

Symmetrical Design: Where possible, design joints to be symmetrical about the weld line. Symmetrical current paths create balanced magnetic fields.

Avoid Sharp Corners: Round corners and transitions reduce magnetic field concentrations that cause arc blow.

Preventing Arc Blow

Design Considerations

During design and planning, consider arc blow potential:

• Minimize long, straight welds near joint ends
• Provide start and run-off areas
• Design symmetrical joints where possible
• Consider AC welding for susceptible applications

Material Handling

Setup Planning

• Plan work lead placement before starting
• Consider multiple work leads for long welds
• Have start blocks and run-off tabs ready
• Test weld to identify arc blow issues before production

When Arc Blow Is Unavoidable

Some situations make arc blow unavoidable:

• Welding at joint ends without run-off areas
• Complex geometries with no alternatives
• Code requirements dictating DC welding
• Material that cannot be demagnetized

In these cases, use all available mitigation techniques:

• Short arc length
• Electrode angle compensation
• Reduced amperage
• Careful technique
• Patience and persistence

Sometimes arc blow must simply be managed rather than eliminated. Skilled welders can produce acceptable welds despite moderate arc blow through technique and experience.