Comparison of the advantages and disadvantages of argon-free TIG welding and argon-filled TIG welding
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This post was last edited by lovingyou on 2018-4-12 at 17:50. Our company has installed two fine chemical production units, and the construction was entrusted to a chemical engineering firm. Due to the tight schedule of on-site construction, the chemical engineering company outsourced one of the units to a private firm. During the pipeline welding process, I compared the welding quality of the two sets of equipment, and there was a significant difference. For now, let’s call the device constructed by the construction company itself Device A, and the device constructed by a private party Device B. During the pipeline welding for Unit A, argon shielding is used for both the steam pipelines and the 304 material pipelines; there is no oxide layer inside the pipes, giving them a smooth surface, and the welds have a beautiful fish-scale appearance. When welding the pipes of Unit B, the construction party usually uses argon-free welding electrodes. There are oxide layers inside some of the flange butt welds, and occasionally there are issues such as weld beads and spatter within the pipes. Unit B relies heavily on internally polished 304 pipes due to process requirements, thus demanding a high level of cleanliness inside the pipes. I am concerned about residual oxide layers in the pipes; it may not be possible to completely remove these oxide layers during purging, acid cleaning, and passivation, so I will communicate with the construction party. The construction party believes that knocking on the welds during purging can remove the oxide layer, without affecting the quality of the product in the later stages. Currently, 80% of the piping work has been completed. I would like to ask these questions to fellow sailors; I hope you can kindly offer your advice. There are the following questions: 1. Compared to TIG welding with argon supply, which method yields better welding quality? How are the two in terms of advantages and disadvantages? If it can withstand X-ray examination. 2. For pipes that have been welded using argon-free welding, can the oxide layer be completely removed during tapping, purging, and pickling? Our products require a very high level of cleanliness; if impurities cannot be removed completely, they will remain in the products and cause black spots, thereby affecting their quality.
No reply......... I’m posting it myself; hope the experts will see it
This post was last edited by CHANGBAISHI on 2018-4-13 08:19. Ordinary TIG welding should be sufficient; if higher standards are required, it is advisable to purge the area and then fill it with argon in order to reduce the formation of internal oxides. It is best to communicate with Party A to determine the specific medium, and it would be ideal to look up the relevant standards as well.
What confuses me now is also determining in which situations TIG welding should be used for the root pass and manual welding for the finish pass, in which situations pure TIG welding is required, and in which situations argon shielding welding is needed. Is there a corresponding standard for this? For fine chemical industries, I believe it is still necessary to use argon welding for process pipelines; for pressure pipelines (X-ray inspections are required), argon welding is also essential for internally polished pipes. Thank you for the reply. Communicate more. I haven’t been to Haichuan for several years now, and it seems that the atmosphere for discussions isn’t as lively as it used to be. Is this post in the wrong section, or are there fewer people in Shanghai Chuan discussing technology these days...
For further clarification: The welds shown in the images of the post were not welded using argon-free welding electrodes; this was because the on-site technician failed to provide proper instructions, and the welder used 304 welding electrodes for manual welding. As a result, there was excessive spatter, and a thick oxide layer that was difficult to remove.
Follow-up update: 1. Coordination has been carried out with the construction party; argon welding will be used for all internally polished pipes and process material pipes. For sections of the pipeline where argon filling is not possible (such as dead ends, and welds where flanges are joined to the pipeline), argon-free welding electrodes should be used. 2. Upon investigation, **no relevant standards or specifications have been established for the applications of argon-filled welding and argon-free welding.** The common practices of construction companies are as follows: (1) Welding of chemical process pipelines: For both carbon steel and stainless steel pipelines, the minimum requirement is TIG welding (this applies to utility pipelines such as compressed air pipelines and circulating water pipelines as well). All connections up to DN100 are welded by TIG welding; for those larger than DN100, TIG welding is used for the root layer while shielded metal arc welding is used for the cover layer. (2) Argon welding: Determined according to process requirements. Process requirements mainly take into account the properties of the medium and the pressure level, as well as whether it is a flammable, explosive, toxic, harmful, or corrosive medium. To put it simply, since it belongs to pressure pipelines and requires radiographic inspection, argon welding must be used. For areas where argon filling is not possible, argon-free welding electrodes are used to ensure welding quality and a high pass rate in radiographic inspections.
Argon-free operation – use with caution! ! ! I don’t dare to talk too much; in principle, extensive recommendations for domestic or international project experience are not supported
Should argon-electric welding or pure argon welding be used, based on the material thickness or the pipe diameter? Isn’t it defined by thickness?