How Beneficial is (FCAW-S) Self-Shielded Flux Cored Welding in the Applications for High Powered Pipeline Welding when compared to (SMAW) Stick Welding?
Thanks to the innovations in science and technology and the progress that has taken place the FCAW-S equipment and wires, we now have plenty of options when it comes to applications for manually done pipeline welding when comparing it to (SMAW) Stick Welding.
Let us check out two means by which to bring down the costs of pipeline since it is directly connected with the pipe. The first is to decrease the load of the steel that is made use of in the construction itself. The second is to build up the tolerance for the pressure of the particular pipeline so as to enable it to forces a larger quantity of substance through it. It has been seen that these two factors have guided pipelines to transformation to steels of higher-strength.
The obvious advantages of higher-strength steel is that it lowers the cost for each foot, the strengthened thickness of the thinner wall which will need lesser filler metal for enabling the completion of the joint (thus helping to reduce the time for welding and other consumables) and finally the decreased costs for fuel and hauling due to the reduced weight. Another advantage is that transportation of the pipe to faraway and interior areas and it has proved to be ideal for areas that are subject to significant extremes in temperature.
But there are new challenges that the higher-strength steels poses – the filler metals will have to equal or greater strengths of the greater tensile but at the same time have a lower content of hydrogen – it is noticed that higher strength steels, since they have a lower carbon base have more chances for cracking that are hydrogen induced. Since the previously used stick electrodes made of cellulosic that were utilized for welding had very high contents of hydrogen (usually 16 ml @ each 100g) which didn’t make them ideally suitable for any welding of X70 or greater. Due to the greater content of hydrogen, it can give rise to notable cracking and other increased costs where downtime and other related reworks are concerned.
It is to overcome these issues that a change from the SMAW (Stick Welding) to the FCAW-S Welding is now happening. Flux Cored Welding definitely has noteworthy advantages in both quality and productivity even though Stick still is universally prescribed for the root passes Let us, through this article, examine these advantages in detail and also review a few of the simple Flux Cored options for filler metal and also examine the gains in the field of welding methodology that proves that it has popularized Flux Cored Welding to make it an ideal option.
The (FCAW-S) Self Shielded Flux Cored Welding and its Advantages
Like the Stick electrodes, the wires for Self-Shielded Flux Cored welding also give protection to the weld puddle, which makes it acceptable for welding during the dirty and windy conditions that occur in the applications of pipeline welding. Though a few additional equipments are required and have to be considered (discussed later), and may even need the re-qualifying of some applications and joints, the procedure does offer significant benefits over the Stick in quite a few areas:
Lesser Hydrogen Content: The most significant advantage worth mentioning is that the wires meant for Self-Shielded Flux Cored welding are structured for the onshore pipeline applications so as to give the required properties for high-strength needed for such applications and at the same time, meeting the standards for lower hydrogen content which is critical when it comes to reducing the cracking that are hydrogen-induced.
Control of the Arc is Increased: Due to the additional wire feeders for checking the voltage and the dual schedule capacities that are associated with the wire feeders of the Flux Cored and the guns, the welders will have more leverage when it comes to precisely performing the arc of the weld.
Uncomplicated to Operate: Flux Cored method makes it possible for comparatively effortless operator training. While welding the high-strength pipe, changes like inter-pass temperatures and pre-heat, together with all the other parameters of welding like voltage, amperage, etc, has to be judiciously monitored. All these features make welding a material risky, so it makes sense to have a welding procedure which is simple to use and also minimizes extra variables that are associated while learning.
Filler Metal for Self-Shielded Flux Cored:
Filler materials that are utilized for welding higher-strength pipe should match or be in excess of the material’s chemical and mechanical property stipulation and must also make available the flexibility to reduce cases of cracking. These are also expected to make up for the very extreme limits of temperatures which the pipelines are usually subject to, as the collision of thermal contraction and expansion, frost and other loadings from the environment have every chance of damaging steel along with the welds. Specific pipeline and the joint designs, when in concurrence with the right selection of filler metal will help to safeguard against such problems.
Till date, many categorizations of the wires for Self-Shielded Flux Cored have proved to be successful when it comes to welding higher-strength pipelines globally. These specially formulated wires are capable of generating lower limits of spatter, creating a slag that can be easily removed to enable speed inter-pass combined with the post-weld cleaning up. Since they don’t require a shielding gas, it enables them to get rid of time and the need to put up shielding tents so as to safeguard gas coverage. Moreover, these special wires give excellent vertical-down competence and provide greater deposition rates when compared to Stick electrodes and thus help to improve the productivity.
Wires Available for Welding High-Strength Pipelines for Self-Shielded Flux Cored are:
AWS E111T8-G H8: These wires are utilized for pipe welding of Grade X100 and also as an over-match on steel with the Grade X80. Though these wires also functions very much like the before mentioned wires, it provides far greater tensile strengths. When welding in the position of 1 G, this wire makes welds having a tensile strength of 123 ksi and gives above tensile strength of above 120 ksi when welding in the position of 3 G. It is ideal for gas and oil transmission pipes and can be procured with a diameter of 5/64 inch. Since the content of hydrogen in these wires is just 6.33 [email protected] g of the weld, it has proved to be an ideal option to help minimize cracking.
The AWS E91T8-G H8: Over and above having a relatively lesser distribution of hydrogen content just 6.2 [email protected] g, the AWS E91T8 all-inclusive position wire offers an impressive tensile rigidity of over 113 ksi, besides exceptional low-temperature strength for impacts (44 ft.lbs, at -40° F/Celsius). It has been formulated as an over-match on the pipe with a Grade X80 which provides good ductility too. As it is obtainable in diameters of 1/16 inch, it makes it easier for even novice welders. Because of its smooth arc features, it also enhances operator appeal. Other similar wires for Self-Shielded Flux Cored that are meant for pipes of high-strength, it offers outstanding mechanical properties, leads to faster freezing, easily removable slag which enables a reasonable weld puddle and also an easy clean-up. The AWS E91T8-G H8 also operates very much like the E81T8-Ni2 J H8 and the E71T8-Ni1 J H8 wires, helping to make welding operations easier while moving around numerous pipelines projects.
The E81T8-Ni2 J H8: A wire that can be utilized for filling and capping passes on pipeline ventures that are constructed from the Grade X80 (or lesser) pipes. This offers high traction strength of 94 ksi and lower CVN collision properties as less as 96 ft, lbs. at -40° Fahrenheit/Clesuis, along with excellent ductility. Because of the “J” designation of the wire, it is guarenteed that it adhers with all the strict specifications for the low-temperature of CVN impact toughness that are required by the AWS A5.29, ensuring the more particular properties when compared to other E8 1 T8 wires that are designated only to the “G” classification. It is used on lap, fillet or for deep grooved welds in both single and multi-pass applications since it possesses a quick-freezing slag which peels off easily thus helping to bring down the post-welding time for cleaning. These E81T8-Ni2 J H8 wires are ideal for welds in any position.
The E71T8-Nil J H8: An all inclusive-position wire that has been formulated for any onshore transmission of pipelines is composed of Grade X70 (and over) pipes and offers high-impact strength at lower temperatures. Offering a tensile toughness of 78 ksi into its (AW) as-welded state, creating welds with less diffusible levels of hydrogen (5.45 [email protected] g). Because of its unique formulation, the wires offer an excellent control over the weld puddle, particularly welding between the 4 and 7 o’clock positions. This comes in really handy for welding operators who are in training and with little experience. This also offers uniformity in weld beads and the possibility of a good weld, while welding numerous passes on the deep-groove joints of the pipe weld. Normal impact values CVN varies with the weld positions (1 G against 3 G) though they fall between the ranges of 295 ft.lbs. at -29áµ’ Celsius (-20áµ’ Fahrenheit) and 135 ft.lbs. at -49° Celsius (-40° Fahrenheit).
Considerations for Flux Cored Equipments
It is possible to perform both the Flux Cored and Stick welding utilizing the same welding generators that are engine-based and that pipe welders have been using earlier, though some machines and other special programs that helps to give maximum performance efficiency when it comes to welding in Flux Cored.
There have been considerations for additional equipments which have in the past, been a deterrent for pipeline applications, when it came to Flux Cored welding. Compared to using a Stinger while Stick welding, the gun for Flux Cored may prove to be more complex, where wire feeders offer an extra item of gadget to posses are take care and when it comes to being in control of matters such as the speed of the wire-feed and amperage, it is considered to be even more strenuous than the Stick electrodes.
While accepting these thoughts and accepting the advancements and developments of welding in Flux Cored in all such applications, the manufactures of these equipments have initiated actions for the improvement of the overall productivity, simplicity and quality of their products. These advancements are:
Flux Cored Guns: These guns have successfully been made to be friendlier ergonomically and substantially lighter than the models that were available in the past. Even the other consumables like the contact tips, etc. have now become more dependable and are easier to adjust and change that the older models.
Wire Feeders: Where, at one time, the designs of the wire feeders were clunky and it has now become both, more reliable and compact. It is possible to keep the dirt out along with other contaminants because of the tight-sealing polypropylene cases that are used now. The additional motors with a high-torque have been included, handles both the small and large diameters of wires for Flux Cored which offers a more uniform feeding.
The digital meters which can exhibit both the amperage and voltage during the welding process greatly helps in improving the accuracy of the weld. Models with voltage sensing capacity provide outstanding arc control. Those with dual schedule competence ( when compared to a Flux Cored gun that is dual scheduled) permits welders in adjusting the speed for the wire-feed on the fly depending on their pipe position. The more robust and reliable designs will include greatly improved contractors – an earlier item that involved heavy maintenance.
The Wireless Remote Controls: Whether it involves the Flux Cored or the Stick welding, where the usual corded remotes have an extension of only 90 ft, the latest remote controls that are wireless are capable of extending the work covering an area to 300 ft from the source of power. Moreover, the presence of digital displays that is available on the remote controls that are wireless now, further offers welders and their helpers’ accurate knowledge and information about the settings of their machine. This, when combined with and the voltage sensing attributes of the feeder and the attributes of the dual schedule gun, gives greater control to the welders and their helpers over the filler deposition and the arc characteristics than was ever possible.
When it comes to addressing the overall requirements of building pipelines of high-strength, there is likelihood of shifting to the FCAW-S welding methodology since contractors are interested to not only complete their projects quickly but also at a lesser cost. Also, there is every chance that the welding equipment and filler metal manufacturers will face the challenge of building on this particular technology and provide even more answers so as to adhere to the strict requirements when it comes to pipes of higher-strength and also provide such contractors with the much needed edge where competition is involved.