There are additional equipment considerations that have been deterrents in the past for Flux Cored welding in pipeline applications: a Flux Cored gun can be more complicated than a stinger used in Stick welding, the wire feeder provides an additional piece of equipment to own and maintain, and controlling things like amperage and wire feed speed are perceived to be more difficult than a Stick electrode. Recognizing these beliefs while also acknowledging the advancement of Flux Cored welding in these applications, equipment manufacturers have taken steps to improve the overall quality, simplicity and productivity of these products.
Advancements include:. As for meeting the overall demands of building high-strength pipelines, it is likely that the shift to the Self-Shielded Flux Cored process will continue as contractors seek to complete projects faster and for less cost. It is equally likely that filler metal and welding equipment manufacturers will be challenged to build on this technology and offer even more solutions to meet the strict welding requirements of high-strength pipe and provide these contractors with an increasingly competitive edge. Weeks had welded with the Flux Cored process in other industries, but had not worked much with it on pipeline repairs.
We had some repairs to inches long and it was much quicker with the wire.
Self-Shielded Flux-Cored Welding: Choosing Your Gun | Bernard
As described in the main body of this article, E71T8-Ni1 wire is designed for all-position welding and provides high-impact toughness at low temperatures. It also offers a tensile strength of 78 ksi in the as-welded AW condition and creates welds with low diffusible hydrogen levels 5. Using the dual schedule capabilities of both the wire feeder and the gun, Weeks was able to manipulate his wire feed speed amperage to match his position on the pipe, such as dropping amperage as he got to the bottom half of the pipe.
The ability to weld downhill with the Flux Cored wire as compared to uphill with a Stick electrode made the process faster.
Most importantly, it allowed him to maintain the high degree of quality demanded in this application while noticeably increasing his productivity. That makes it a lot easier on me.
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Thank you for subscribing to our eNewsletters. You can manage your subscription s by signing into your account. As pipelines transition to high-strength steels such as X70, X80, and X, welding challenges — including matching tensile strength and avoiding hydrogen-induced cracking — have pushed the industry to consider new welding procedures. Advantages include lower hydrogen content, increased speed and deposition efficiency, increased control of the arc and ease-of-use. Advantages of Self-Shielded Flux Cored Welding Just as with Stick electrodes, Self-Shielded Flux Cored wires provide shielding of the weld puddle, making it suitable for welding in the often windy and dirty environments encountered in pipeline welding applications.
While it does require some additional equipment considerations detailed further in the article , and may require re-qualifying certain joints and applications, the process offers noticeable advantages over Stick in a number of areas: Lower Hydrogen Content: Arguably the most important benefit, Self-Shielded Flux Cored wires designed for onshore pipeline applications provide the high-strength properties required in these applications while also meeting the low hydrogen content standards required to reduce hydrogen-induced cracking. Increase in Speed, Deposition Efficiency: While quality is paramount, Flux Cored welding typically allows for faster travel speeds and offers greater filler metal deposition efficiency as compared to Stick electrodes.
This greater deposition efficiency ultimately means welders will need less filler metal to get the same job done.
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Institutional Subscription. Conversely, mixed gases are more expensive, but the welds need less cleaning after completion. Gaining the best results from flux-cored wires is as much a matter of selecting the right wire for the job as it is having the proper equipment and training to weld with them. A common mistake made when setting up equipment to operate FCAW-S is selecting the wrong polarity on the welding power supply. FCAW-S wires often are paired with a voltage-sensing wire feeder. The welder can set the voltage at the power source but then control the wire feed speed and therefore amperage at the feeder.
This feature is helpful on large job sites; fewer trips to the power source allows for more welding time.
In the event that the welder varies the contact-tip-to-work distance CTWD , voltage-sensing wire feeders also can help regulate the subsequent voltage variations. Both wire types require V-knurled drive rolls in the wire feeder to provide smooth wire feeding and consistent weld quality. Flux-cored wire is softer than solid wire and can easily be deformed or crushed if incorrect drive rolls are used. During the welding process, welders should employ a drag technique.
A good drag angle for flat, horizontal, and overhead positions is between 15 and 45 degrees. For vertical-up welds, a gun angle of 5 to 15 degrees works well. A steady and fast enough travel speed keeps the weld pool from getting ahead of the arc, which could lead to slag inclusions. For applications in which companies seek to gain productivity through higher deposition rates, flux-cored wires often are a viable option. These wires are available in self-shielded and gas-shielded varieties for use in the field and shop.
Welders using flux-cored wires should be sure to use the correct stick-out or electrode extension; self-shielded wires are particularly sensitive to this variable. Depending on the wire diameter and type, the manufacturer-recommended stick-out could exceed 2 in.
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Improper stick-out can cause issues such as burnback, worm tracking, incomplete slag coverage, and difficult slag removal. Stick-out also is crucial because it provides a level of resistive wire heating, which helps increase the deposition rate. The increase in resistance allows less current to pass through the arc, permitting higher wire feed speeds to be used, and thus increasing the deposition rate.
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Damage from moisture or other contaminants can lead to poor weld quality and likely void the product warranty. It's a good idea to maintain the same temperature in the storage area as in the welding area.
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