A look at the characteristics and advantages that can result in overall cost savings.
Quick highlights – Metal Cored Wire:
- High deposition efficiency
- High deposition rates
- Increased duty cycles
In today’s industrial world, metal fabricators have an array of choices to select from when deciding which welding process and consumable to use for a specific application. As always, product cost, efficiency, and quality will play a key role in these decisions. It is a continuing struggle to find consumables that can reduce costs without sacrificing the integrity of the work. Many fabricators, however, are finding that metal cored wire is quite a beneficial change. While this type of consumable is not new to the welding industry, the classification and the advantages of using metal cored wire are not always recognized.
Metal Cored Wires
The American Welding Society classifies metal cored wires under the same specification as solid MIG wires. Metal cored wires have a very similar construction to flux cored wires but the performance and functionality parallel solid MIG wires. The basic composition of metal cored wire is a tubular electrode comprised of an outer metal sheath and a core of powdered materials. Both the outer sheath and internal powder composition can be formulated to meet specific requirements.
The outer metallic sheath can be cobalt, nickel, iron or stainless steel-based. This sheath conducts the electrical current during the welding process and the current carrying density is greater in metal cored wires, therefore increasing the deposition rate as compared to solid MIG wires. Also, improved penetration and sidewall fusion capabilities are made possible due to these increased deposition rates.
Metal cored wire internal composition consists of both elemental and alloyed powders such as nickel, cobalt, chromium, tungsten, molybdenum, and manganese to name a few. This internal composition of metallic powders is far less conductive than the outer sheath carrying the electrical current, resulting in a more controlled weld pool.
Advantages of Metal Cored Wires
Making the change to metal cored wire can be extremely advantageous. There are a number of factors that contribute to the success of metal cored wires, including:
- High deposition efficiency
- High deposition rates
- Increased duty cycles
The deposition efficiency of a consumable is the amount of material that converts to weld metal. During the welding process, a portion of the consumable is lost to slag, spatter, and fumes. The lower this percentage of lost consumable is, the higher the deposition efficiency will be. Depending on the transfer used, metal cored wire can exhibit a deposition efficiency range of 92-98%. This high efficiency is due to a decreased volume of slag and spatter that require removal from the weld and parent material. Reduced fume levels are also reflected in the deposition and create a healthier work environment for the welder.
Higher deposition rates are also seen in the implementation of metal cored wire. The deposition rate is the amount of weld metal deposited during a given time. The deposition rate of metal cored wire is about 57% higher per hour than solid MIG wire. This ultimately results in higher achievable welding speeds.
Travel speeds rely on duty cycles. During the welding process, a duty cycle refers to the amount of continuous arc time. Factors such as travel time, equipment, slag removal, and replenishing consumables affect the duty cycle. Shielded metal arc welding using stick electrodes can only produce about 12 minutes of welding every hour, whereas metal cored wire yields a duty cycle of about 30 minutes an hour. While solid MIG and flux cored wire can achieve these high duty cycles as well, only metal cored wire can take the process to a whole new level with faster travel speeds. Metal cored wire can account for increased travel speeds of 35-40%. Fabricators can practice automatic application with high duty cycles and travel speeds without jeopardizing weld integrity and appearance.
Conclusion
As stated earlier, the main objectives for fabricators are to achieve productivity and efficiency at a lower cost. While metal cored wire has a higher cost per pound than other consumables, the true economic payback is seen during the process itself, not in the initial cost of materials. Labor costs are generally a substantial portion of total cost and therefore welding efficiency and productivity must be weighed heavily. When assessing the change to metal cored wire, keep in mind these key points that result in overall cost savings: high deposition efficiencies, high deposition rates, increased duty cycles and faster travel speeds.
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