|
FCA-welding-tipsfor increased productivity.SOLUTIONS with Effective, Powerful Advice
FCA-welding-tips is the subject of this page. We are speaking of course of Flux Cored Arc Welding, a quite important process that could be exploited even more in certain industries. Be alert to the benefits of putting it to good use. First among them the potential to be the most cost effective for the correct application. It competes directly with GMAW (Gas Metal Arc Welding) from which it derived, so that sometimes it may be quite difficult to find out which of the two is the most cost effective. Because first the GMAW process must be optimized for the job, if one wants to look seriously at the comparison.
FCA-welding-tips seekers should know that the process, that provides a continuously fed tubular electrode containing flux, comes in two versions for additional flexibility: self shielded FCAW-S and gas shielded FCAW-G. It is contended though that when weld quality is of paramount importance, only GMAW or Gas Shielded FCAW should be considered.
The torches or guns should be selected according to the process version selected. They may be made for manual or mechanized application, air cooled for low current rating or water cooled for higher amperage, over 600 A, and continuous duty. One of the important FCA-welding-tips is that torches designed to be gas cooled should be operated with the gas and flow rate indicated by the manufacturer. Cutting off gas supply or changing its type could compromise the cooling capacity and limit the torch life. Shielding gas may be supplied concentrically to the electrode through proper gas passages and nozzle, or externally, from the side. Except for the provision of means needed to control the supply and flow of the shielding gas if required, other equipment elements are not significantly different for the two versions.
Special guns or torches with vacuum fume extraction may be useful if other solutions are less effective in providing comfort and health to welders.
Listed with the FCA-welding-tips are the process main Advantages:
FCA-welding-tips should also consider Limitations:
Constant voltage power supply is generally recommended in FCA-welding-tips, with preset voltage for each job, and current dependent on electrode extension and feed speed. Usual polarity is DCEP (electrode positive), however for certain electrode types The electrode extension is the length of electrode between the sliding contact tip and the arc. It is a feature common to other processes like GMAW and SAW using a consumable electrode, but should be included in a presentation of FCA-welding-tips. This length of (steel) wire is preheated by the current flowing, as a result of resistance heating (Power P=I2R), contributing to moisture reduction. The current available to the arc (the welding current providing heat to melt the base metal) and the voltage across the arc are reduced when the electrode extension is increased. In general FCA-welding-tips recommend longer electrode extension than corresponding GMAW for most applications, 18 to 25 mm (3/4 to 1") are common, but also up to 95 mm (3 3/4") in certain cases with proper torches, with at least 12 mm of which inside the nozzle. FCA-welding-tips as to the primary functions of flux are:
The flexibility of the FCAW process to suite a large range of requirements derives primarily from the wide variation of flux composition, much larger than what would appear from official Classifications. Although the task of individual components is generally known, the exact composition is considered proprietary by electrode manufacturers. Alloying elements may be added to control chemical composition of deposited weld metal. It would be highly desirable if each welder knew all the FCA-welding-tips for selecting recommended electrode type and starting parameters for every new job. This type of knowledge and expertise can come only with continuing learning and training followed by critical help from auxiliary services like a metallurgical laboratory in charge of examining the results and providing feedback. In our opinion the task of selection of applicable FCA-welding-tips cannot be left only in welders' hands or on supervisors' shoulders. Management should establish a professional workforce capable and willing to lead research and improvement of the best welding conditions, with setting of goals and measurement of achievements. Reference tables or graphs should be made available, as helpful FCA-welding-tips, to start with suitable parameters for given materials, thickness, joint preparation and position, together with target weld deposition rate. It must be realized that there is not a single acceptable solution to any given job. Therefore the suggested starting parameters should be interpreted as indicating ranges of values, sometimes marked as hatched areas in certain diagrams. To optimize the conditions, parameters have to be probed on test pieces with variations and changes as best suggested by experience, common sense and test results. Once the parameters are optimized, according to the suggested FCA-welding-tips, the data should be organized in formal Welding Procedure Specifications (WPS), to be followed by anyone involved in such a job. A few selection outlines, possibly covering the majority of general applications in carbon steel, were included in a reference article on Selection of Electrodes for GMAW and FCAW that was published in Practical Welding Letter issue No. 06 for February 2004. A short article on FCAW electrodes was presented again in Practical Welding Letter issue No. 18 for February 2005. In the Practical Welding Letter issue No. 32 for April 2006 a short list of FCAW electrode manufacturers is presented, to help interested readers in finding the required information they may need. An Interview with Greg Metko from Miller Electric Mfg. Co. on An Article on Advancements in Flux Cored Filler Metals was published (4) in Issue 92 of Practical Welding Letter for April 2011. An Article on A new Open Specification for FCAW Filler Metals was published (4) in Issue 105 of Practical Welding Letter for May 2012. An Article on Filler Metal for for Gas Shielded FCAW was published (4) in Issue 118 of Practical Welding Letter for June 2013. An Article on Cored wire for welding galvanized steel was published (4) in Issue 135 of Practical Welding Letter for November 2014. An Article on Metal Cored Filler Wire was published (4) in Issue 153 of Practical Welding Letter for May 2016. An Article on Spatter Reduction was published (3) in Issue 158 of Practical Welding Letter for October 2016.
To get at no cost every issue of PWL as it is published, please subscribe.
For meeting special requirements, interested readers are urged to study official classifications and to obtain manufacturers' recommendations. Electrode Classification The first letter E designates electrodes, and the letter T just before the dash indicates Tubular shape, containing flux. (That is opposed to the letter S, indicating Solid wires). Other designators were selected for minimum tensile strength, welding position, usability, composition and possibly the shielding gas. There may be a dependence on electrode size, with small sizes suitable for all positions, and larger sizes only for flat or horizontal welding. The suggested polarity may be included in the classification or in information supplied by the manufacturer. Not all consumables are made equal, this is an important FCA-welding-tip, even if put by manufacturers in the same AWS class. Therefore it is advised, before committing to a large job, to contact different manufacturers explaining the type of application, and to devote sufficient time and energy in practical testing of proposed electrodes. It should be noted that "all position" electrodes are usually not the best for flat and horizontal applications. All position means really "all other positions", excluding flat or horizontal. This capability is achieved by promoting fast freezing and thin slag, sometimes at the expense of correct fusion and acceptable weld appearance. For complete information and additional FCA-welding-tips the interested reader is referred to specialized publications like the AWS Welding Handbook ninth edition, Volume 2, pages 225-239.
While the classification presents suggestions and FCA-welding-tips, it is understood that the user may deviate from them. For example, a given electrode may be recommended for flat or horizontal position: it may also be suitable for other positions, depending on the (small) size selected, the current level and welder's skill. It may be important to add to the FCA-welding-tips the reason why certain electrodes are suggested for single pass welding, while others are for multiple passes. Those for single pass may include increased proportions of deoxidizers like silicon and manganese that make the filler metal suitable for welding over light scale or rust without resulting in porosity. If used for multiple passes though, those elements would increase the weld metal alloy content, therefore increasing hardness and reducing ductility. The same unwanted effects could be caused by using, instead of straight carbon dioxide as recommended by classification for the case in question, less reactive mixtures of 75-80% Argon and 25-20% carbon dioxide. However it should be noted that in certain cases experimenting with a different gas may give improved result and even be recommended by electrode manufacturers. Selecting the right electrode from Classification lists might be quite difficult except possibly in a few well defined situations. Even the Welding Handbook urges users to contact electrode manufacturers and ask for their recommendations to find the proper filler to be used in given applications and for their suggested optimum settings. In his important book "A Management and Engineers Guide to Mig-Welding, Quality-Cost-Training" Ed Craig (www.weldreality.com) suggests the following FCA-welding-tips for the selection of Flux Cored Wires instead of the more common solid wires used with GMAW:
Specifications ANSI/AWS A5.20/A5.20M:2005
ANSI/AWS A5.29/A5.29M:2010
ANSI/AWS A5.22/A5.22M:2012 ANSI/AWS A5.21/A5.21M:2011
Safety Also exposure to radiant energy, to excessive noise and to electric shock should be taken care of by applying proper provisions.
Any specific questions? Write them down and send them to us by e-mail, by clicking on Contact Us.
To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on
Tig Welding Tips
If you did not yet find what you need, why not typing your question in the following Search Box?
POWERED BY:
Click on this Logo NOW! Copyright (c) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017  FCA-welding-tips and skill, knowledge and practice will help in getting out from the process the increased productivity it is able to provide.
|
