Arc welding is a popular welding process, and everyone, from beginners to professionals, benefits from it. The different types of arc welding provide a range of opportunities and applications, with one common drawback: arc blow. What is the arc blow effect?
The effect of arc blow causes your weld to become ugly and asymmetrical. Arc blow refers to the usually unwanted change in the path of an arc during welding. Sometimes, it can happen despite your care and precision when welding.
This article considers the safety of arc welding and what arc blow effect means. I also discuss how to strike an arc and the possibility of arc blow causing welding defects.
Is Arc Welding Safe?
For any welding project, safety is a critical consideration. Arc welding is safe when you take proper precautions.
If you ignore these safety precautions as you weld, you risk exposure to some hazards, including dust, toxic fumes, fires, electric shock, burns, heat stress, radiation, noise, and explosions. Any of these can cause severe injury and even death for you and the other people around.
The major hazards connected with arc welding are arc radiation and electric shock. Light radiation—ultraviolet and infrared rays—come from the arc, and protective gear helps limit exposure. The protective equipment includes:
- Clothing
Cover exposed areas of the skin, and don’t wear short sleeves or shorts. Use a welding lightweight welding jacket and leather apron when you work. Always keep good gloves (without holes) on.
- Head shields
Shields are made with filter glass, which is dark enough to absorb the radiation rays. The filter glass conforms to EN 169:2002, and their grades follow a shade number, and this number specifies the amount of light the glass allows to pass through—lighter filters have lower numbers.
You should select the shade number based on the current level and welding process.
Electric shock is the chief danger, and it comes from the live parts of the welding circuit—the workpiece and the electrode. Protective measures against electric shock include:
- Checking the equipment
Qualified staff must install all welding equipment and confirm that they connect it according to the manufacturer’s instructions. Before using daily, you must check the cable, coupling devices, and electrode holder for defects.
- In MMA welding, isolate the electrode holder when changing the electrode.
- Use the appropriate level of waterproofing for the welding equipment when working outside. Set up a cover for yourself, the workpiece, and equipment if there’s a risk of heavy rain.
- Don’t wear jewelry, especially metallic watch straps or rings.
- Wear boots, overalls, and gloves.
- Multiple welders using different power sources on the same workpiece should work outside each other’s reach.
Other general protective measures include reading the owner’s manual and relevant safety codes, using a respirator, ventilating confined spaces, and maintaining a clutter-free and safe work environment.
What Is Arc Blow Effect?
Arc blow describes the deviation of an arc from its usual path (usually the shortest distance) between the electrode and the base metal. It deflects forward, backward, or to the sides of the welding direction.
An unbalanced magnetic field around the welding arc is responsible for the arc blow, and it happens when you use DC. The direction of the arc blow varies, but the forward blow creates more difficulties for you, and it can cause slag inclusions.
The two types of arc blow are magnetic arc blow and thermal arc blow. While thermal arc blow produces a considerable effect with high-speed automatic welding, it has a negligible effect with manual welding.
However, magnetic arc blow is more troublesome for you, and it causes most of the welding defects. You can control arc blow by following some steps, including:
- Demagnetizing the workpiece when necessary.
- Using a lower welding current and reducing the welding traveling speed.
- Wrapping a ground cable around the workpiece to neutralize its magnetic field.
- Fixing the workpiece properly by using fixturing devices and heavy tack welds.
- Keeping the arc as short as possible to help the arc force counteract the arc blow.
- Using AC instead of DC for the root run.
Although you may be unable to eliminate an arc blow completely, you can minimize its disruptive effects by applying the above measures.
What Are the Ways to Strike an Arc?
In an electric welding circuit, an arc is formed when you bring the electrode in contact with the workpiece and then withdraw it slightly. The current that jumps this gap creates an arc hot enough to melt both the electrode and the workpiece.
A welder must have the ability to strike and establish the correct arc quickly and easily. Having a steady hand and good spatial recognition will help you get this skill. There are two main methods of striking an arc, and they are:
Scratching—easier for beginners and with an AC machine. Like you would strike a matchstick, you move the electrode across the plate at an inclined angle. The arc is formed when the electrode scratches the plate.
Tapping—you move the electrode downward vertically towards the base metal.
When the arc has formed in both methods, you withdraw the electrode briefly to create an excessively long arc before returning to normal arc length. Freezing is a problem often encountered with striking an arc.
The electrode fuses or sticks to the workpiece because the current melts the electrode tip before you withdraw it from contact with the cold base metal. Brush your work and clear it of dust and dirt before striking an arc.
Does Arc Blow Cause Welding Defects?
Because arc blow moves the arc from its regular path, the following defects may arise:
- Intermittent or continuous undercut.
- Surface porosity.
- Incomplete or excessive penetration based on the allowable limit.
- Lack of fusion, which produces high-stress areas.
- Narrow and high beads or wide, irregular, and wavy beads.
- Slag inclusions between weld beads or within the center of a deposited weld.
- Excessive spatter.
You can avoid these defects by following the tips to control arc blow. Understanding its effects and knowing how to manage it will help you produce strong and clean products.