Can we weld a 35Cr alloy pipe without purging with argon (there must be a root gap of 3mm)?

Question

we cannot use a flux cored electrode or SMAW as the spec is against it

Answer 1

No, we can not weld a 35 cr alloy pipe without innert gas purging(Argon).
Specification are given only after considering worst case and proper designing.
When welding stainless steel, titanium, and other corrosion-resistant materials, creating a perfect weld environment is of the utmost importance, because the desired corrosion resistance depends on it. During welding, the heated weld seam is exposed to air and oxidizes if it is not protected. This oxidation must either be prevented or treated later. Successful welding depends in part on a combination of proper purging equipment and techniques.
(During the welding of steels, oxidation occurs in the weld seam if oxygen reaches this area unhindered This situation is even more acute with titanium, zirconium, molybdenum, and other gas-reactive metals and alloys. The resulting oxidized surfaces are no longer corrosion-resistant, and further treatment is necessary. Removing oxidation by grinding also removes the metal's passive protection against corrosion. Other mechanical procedures, such as brushing, blasting, and pickling, remove the oxidation, which restores corrosion resistance. However, in some cases such as pipe welding, removing oxidation after welding is difficult or impossible to do. During pipe welding, oxides usually are located in areas that are almost impossible to access, such as in two 4-inch-diameter pipes that are each 10 feet long. Pickling will restore the corrosion resistance, but it is time-consuming and nearly impossible on a remote job site. Instead of removing oxidation, another solution is to prevent it from ever occurring. In essence, this is what purging tries to achieve, With purging, a gas is used to protect the weld seam until it has cooled to the point that oxidation no longer can occur. Usually, an inert gas such as argon, which is heavier than air, is used .)
For, more detailed information click:
http://www.junctiontools.com.au/Pta_Site/JA00.htm

Answer 2

No. You must use Argon purging to prevent oxidation and porosity. The 3mm root gap is normal. Has the spec stated Mig or Tig ? Go with the Tig if you have a choice.

Answer 3

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