Advantages and Disadvantages of Metal Cored Wires

Advantages and Disadvantages of Metal Cored Wires

Know More About Metal Cored Wires Including Its Advantages & Disadvantages

In today’s world, metal-cored wires are growing in popularity. Fabricators have a wide range of welding processes and consumables to choose from and there are many advantages and disadvantages to each. Before making a move, though, you have to factor in welder skill, equipment, availability of consumables, environmental issues, and economics.

Metal cored wire is a tubular wire filled with metallic powders, alloys, and arc stabilizers. Using it offers higher duty cycles, faster travel speeds, low fumes, and improved cost-effectiveness. Below, we’ll explore the advantages and disadvantages of metal-cored wires to help you determine whether it’s a fit for your productivity and profitability needs.

Advantages of Metal Cored Wires

How do you know if metal-cored wires would be an advantage for your process? Consider the following factors:

High Deposition Efficiency

Deposition Efficiency diagram

Deposition efficiency is the relationship of the weight of the weld metal deposited to the weight of the electrode (or wire) consumed in making a weld. The higher the deposition efficiency of a consumable, the lower the amount of that consumable is wasted by not becoming part of the deposited weld metal.

With their arc characteristics, very low spatter level, and low slag volume, metal-cored wires offer deposition efficiencies in the 92-98% range. This is with the selection of spray transfer mode and high argon shielding gas mixtures. However, a change in transfer mode or shielding gasses will impact deposition efficiency.

High Deposition Rates

Deposition rate for metal cored wires

The deposition rate is the measurement of how much weld metal is deposited within a given time period. Deposition rates along with deposition efficiency are the leading determinants of the cost-effectiveness of a consumable.

Generally expressed as pounds per hour (Kg/hr), metal-cored wires have one of the highest deposition rates of all of the welding consumables. Metal cored wires are capable of having deposition rates as high as 12-14 pounds per hour (5.4-6.4 Kg/hr) for a 0.045” (1.2mm) diameter wire. This compares to a solid MIG welding wire in the same diameter of 8-10 pounds per hour (3.6-4.5 Kg/hr).

The high deposition rates coupled with high deposition efficiencies and low slag volume will allow the metal cored wire to be used at higher travel speeds. This leads to an increase in productivity. Generally, when a deposition rate of 9 pounds per hour or greater is achieved with a metal cored wire versus a solid MIG wire, there will be cost savings.

High Duty Cycles, High Travel Speeds

Duty cycle travel speed

With a continuous process, such as metal-cored wire, the duty cycle increases to as much as 50% of the time or 30 minutes per hour for arc generation. The duty cycle for SMAW electrodes, on the other hand, is in the range of 20%. This translates to only 12 minutes of welding every hour an arc is generated. This is one factor that makes the use of automated or robotic welding so attractive.

Along with the increase in duty cycle comes the benefit of faster travel speeds. Automated welding is only limited to the supply of parts to the weld station and the travel speed of the process. Only metal-cored wires have the capability of combining high duty cycles with high travel speeds without sacrificing bead appearance, penetration, or weld integrity. This can significantly reduce the cost of welding.

Low Slag Volume, Low Spatter Levels

Metal cored wires have a very low slag volume. This means decreased spatter levels that need to be cleaned from the parent material prior to finishing. This is especially important to continuous operations where the part moves from an assembly/welding operation directly into a cleaning and painting operation. Cleaning of weld spatter from a fabricated piece can be a significant post-weld clean-up expense.

Potentially Lower Cost

With a filler metal, it’s not how much it costs per pound that counts, but how much it costs per pound to use. Consider an actual welding application using 0.052’ (1.4 mm) E70S-6 MIG wire welded under pulse conditions at 425 inches per minute wire feed speed, 24.5 volts and a travel speed of 70 inches per minute.

This was converted to metal-cored wire and welded at the same wire feed speed, voltage, and travel speed. As a result, the travel speed could be increased to 85 inches per minute, or a 20% increase. Not only was the travel speed increased, boosting the throughput, but the number of necessary repairs also diminished as did the amount of time to make repairs by 10%.

In another application, a 0.040” diameter (1.0mm) ER409Cb solid MIG wire was welded under pulse conditions at 180 amps, 20 volts, and 19.6 inches per minute travel speed for a thin wall tube. It was converted to a 0.045” (1.2 mm) EC409Cb metal-cored wire welded under pulse conditions at 190 amps, 21 volts, and 27.5 inches per minute travel feed speed.

Travel speeds increased and the metal-cored wire was better able to bridge gaps due to poor fit-up. This contributed to a lower defect rate and the need to rework parts offline. The results were a 40% increase in production, lower consumable cost per pound of weld metal, and lower maintenance costs.

Disadvantages of Metal Cored Wires

The advantages of metal-cored wires do not always outweigh the disadvantages that could be costly to your process and time.

Investment in an Automated System

To get the most from metal-cored wire, an automated or robotic setup is required. In addition, experience in programming a robot is necessary due to an increase in weld puddle fluidity. For instance, this is true when welding a small diameter tube where the positioning of the torch to the part is more sensitive with a metal-cored wire. In addition, since the process generates more heat and higher amounts of radiant light, an automated system keeps workers safer.

Adjustments to Equipment

To gain all position capability with a metal-cored wire, like the solid MIG wires, either a short arc transfer mode or pulse mode is required. However, most pulse machines do not contain a program specifically for metal-cored wires. Although not necessary, it does improve performance. This means the equipment manufacturer will have to make adjustments and program modifications to the power source.

Lack of Capacity in Stations Down the Line

A significant increase in productivity and throughput in one station will be negated if the subsequent stations down the line cannot handle the additional parts. When considering the increase in parts per hour that can be achieved by the metal cored process, the stations down the line also need to be considered as far as their capability of handling the increase.

Choosing the right filler metal for the job is a critical decision, one that needs to be weighed carefully. However, knowing when it makes sense to use metal-cored wire can help increase productivity and save money, allowing you to weld more efficiently, deposit more weld metal, reduce issues with quality, and spend less time on clean-up.