Nippon Steel Corporation

Kyoichi Nagano

Kunio Koyama

Toshihiko Takami

Koichi Shinada

Motonori Tamura

Shigenobu Soneda

Hiroshi Naganuma

A welding flux which forms a weld metal simultaneously satisfying low-oxygen, low-nitrogen, and low-hydrogen contents, gives weld beads in good form, and joins given metal pieces without entailing weld defects is obtained by formulating the flux in a composition such that a four-component system used therein is formed of CaO, MgO, Al.sub.2 O.sub.3, and SiO.sub.2 in the following proportions based on the total amount of the system taken as unity (100%),

Low-hydrogen, low-nitrogen, low-oxygen welding flux

In a low hydrogen type covered arc-electrode, the sources of diffusible hydrogen are kept to a low level by selecting kind of the ingredients for producing the electrodes or by baking the ingredients. In the process of the present invention, the covered arc-electrode is baked at a high temperature so as to extremely reduce the amount of the sources of diffusible hydrogen of the weld metal, while decomposition of limestone, which is one of the covering components, is prevented due to a novel baking atmosphere containing CO.sub.2. The weight ratio of Na.sub.2 O/K.sub.2 O in the covering is adjusted to be 1 or more, so as to keep amount of fumes.

Process for production of a low hydrogen type covered arc-electrode

Non-Fused flux composition particularly suitable for horizontal submerged-arc welding in production of welded structures such as storage tanks and pressure vessels, comprising 13 to 30% TiO.sub.2, 5 to 50% CaF.sub.2, 20 to 40% MgO, 12 to 30% Al.sub.2 O.sub.3, 2 to [20-(% CaF.sub.2).div.3]% SiO.sub.2, 0.1 to 1.0% B.sub.2 O.sub.3, and providing good low temperature fracture toughness of weld metal.

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Kamakura, Japan

Kyoichi Nagano