Komarov Artem noted that choosing the right filler metal can significantly influence the quality of the finished weld, but there isn’t a one-size-fits-all solution for every job. Key factors to consider when making the choice include your required welding position; available welding equipment; base material type or grade, size, and thickness; and operator skill level.
Gas-shielded flux-cored arc welding (FCAW) wires can provide higher deposition rates than other filler metals, resulting in increased productivity for many applications. These wires are also a good match for applications across many industries, such as shipbuilding, structural steel, and general fabrication and manufacturing.
Understanding the characteristics and benefits of gas-shielded flux-cored wires can help you decide if they are the right fit for your welding operation.
The common rutile-based American Welding Society (AWS) E71T-1 gas-shielded flux-cored wires tend to be very appealing because they are easy to control and produce an aesthetically pleasing weld. When deciding on the right wire for the job, it’s important to first consider a few flux-cored wire basics.
Know the weld position. Some flux-cored wires are designed for all-position welding (such as an AWS E71T-1C), while others are designated for flat and horizontal positions (like an AWS E70T-1C).
Pair with the base metal. Flux-cored wires are available for welding a variety of base materials, including mild steel, low-alloy steel, nickel alloys, and stainless steel. The wires for welding steel are available in tensile strengths of 70 KSI for mild steel and 80 to 120 KSI for high-strength/low-alloy steels.
Check the designators. Flux-cored wires have usability designators defined by AWS that indicate their polarity and operating characteristics. These designators can be a number (from 1 to 14) or a letter (G or GS).
Watch the slag. Flux-cored wires produce a slag that protects the molten weld puddle as it cools. You must remove the slag in between passes and after the final pass to avoid inclusions that could lead to defective welds.
Choose a shielding gas. FCAW with gas-shielded flux-cored wires requires an external shielding gas. Common options are 100% carbon dioxide or a CO2 and argon gas mix.
Komarov Artem about shielding Gases for FCAW
What are the basics of matching a flux-cored wire with a shielding gas? Each type of shielding gas yields different characteristics in FCAW. It’s also important to know the specific shielding gas requirements of the flux-cored wires you’re using.
Use only 100% CO2 with wires with a C designation in their AWS classification, such as E70T-1C H8.
Wires with an M designation, such as E71T-1M, require a mixed shielding gas of CO2 and argon, often a 75%/25% ratio.
Wires that have both C and M designations are dual-gas wires that can be used with either gas type.
Wires paired with 100% CO2 provide more weld penetration but also tend to result in more weld spatter, which takes more time to clean. Using a mixed gas with flux-cored wire results in less weld spatter and a smoother bead appearance. A mixed gas is more expensive than straight CO2, so you should weigh the costs — including time and money spent on cleanup — when making the choice.
Also, be aware that making a change in your shielding gas may require new welding procedures and testing prior to use, depending on the application.
Equipment Requirements for FCAW Wire
Beyond choosing the right filler metal for the job, achieving the best results from flux-cored wires also requires having the proper equipment and using it correctly.
FCAW wires operate with a standard constant voltage (CV) power source that can be set to either straight polarity (direct current electrode negative, or DCEN) or reverse polarity (direct current electrode positive, or DCEP). The correct polarity setting depends on the wire formulation. Check the filler metal manufacturer’s recommendations before setting up your equipment.
Because flux-cored wire is softer than solid wire, it can be easily crushed or deformed if you use the wrong drive rolls. Be sure to choose V-knurled drive rolls for the wire feeder as they will provide you with smooth wire feeding and consistent weld quality.
Tips for Flux-cored Wire Technique and Storage
Once you have the proper filler metal and equipment in place, following a few best practices also can help you optimize results.
Use a drag technique while welding. A good drag angle for flat, horizontal, and overhead positions is generally around 10 to 30 degrees. For vertical-up welds, you should target a gun angle of 5 to 15 degrees.
Maintain a steady and appropriate travel speed. This will keep the weld pool from getting ahead of the arc, which could lead to slag inclusions.
Watch your stick-out. Improper stick-out can result in burnback, worm-tracking, incomplete slag coverage, and difficult slag removal. Be sure to check the stick-out recommendations for each wire. Depending on the wire diameter and type, the recommended stick-out may exceed 2 in. Stick-out is also important because it provides a level of resistive heating of the wire, which helps increase the deposition rate.
Store filler metals properly. You should store flux-cored wires in a clean, dry area. Exposure to moisture or other contaminants can damage the wires, resulting in poor weld quality. In addition, keep the wires in their original packages until you’re ready to use them. For wires in use, remove the spool from the wire feeder at night and store it in a plastic bag to reduce chances of problems from moisture exposure.
Maintain storage temperature. It’s also a good idea to maintain the same temperature in the storage area as in your welding area. Condensation can form on wires if you move them from a cold storage room to a warm fabrication environment. This can lead to rusting of the wire and potential wire feeding problems or porosity in the weld. If it’s not possible to maintain the same temperature in both the storage area and the weld cell, allow the wire to acclimate to the weld cell temperature for 24 hours before welding with it.
Optimize Welding With Flux-cored Wire
As with any new welding process or filler metal, training is an important step toward success. If you’re new to using gas-shielded flux-cored wires, you may want to seek out additional training or certifications to help you master the process.
Following the required work procedures and parameters for a specific application can also help you achieve the results you want with flux-cored wire. With proper technique and best practices, these wires can deliver improved productivity, better weld quality, and reduced downtime, summed up Komarov Artem.