The term, “uranami,” is the literal pronunciation of the two-word Japanese technical term . “Ura” literally means, “reverse side,” and “nami,” “ripples.” “Uranami” is used to describe the penetration bead protruded on the reverse side of the weld joint when welded from the face side of the weld joint (one-side welding without backing materials) — Fig. 1.
Fig. 1 — The uranami is the penetration bead protruded on the reverse side of the groove when welded from the face side of the groove (one-side welding without backing materials).
“Uranami” has been used in the welding field in Japan for quite some time. This term was common already in 1954, when LB-52U was developed. LB-52U is now called the “uranami” electrode, or an exclusive-use covered electrode for “uranami” welding (one-side welding without backing materials). The JIS standard now specifies “uranami” bead, to mean “penetration bead.”
“Uranami” welding is one of the one-side welding processes, but no backing material (steel backing, refractory backing, weld backing, or gas backing) is used. Therefore, the “uranami” electrode is ready to use for one-side welding without any need to prepare backing material or equipment (backing and clamping jigs) — Fig. 2.
PS NOTE : The above write up is a gist taken from an original article.
Find the link to the original article here https://www.kobelco-welding.jp/education-center/abc/ABC_1998-04.html
NIKIT’s Experience on Uranami :
Over the years Uranami Welding has reached far beyond the uranami electrode method, as we have experienced the same by adopting Uranami in TIG welding process, where the high pressure connectors tubes in used in excavators & rock breakers cylinders can be welded with only TIG fusion and with flat butt joints rather than groove / chamfered butt joints.
With pressure burst testing withstanding up to 2000 bar these connector tubes do not crack in any of the weld joint & this is solely because of the process of Uranami Welding. With such high quality weld bead & load withstanding capabilities many of the high pressure connector tube manufacturers & related industries are seamlessly adopting this methodology.
Our first tryst with Uranami Welding dates back to the year 2014 when our most coveted customer SOBO Technologies & a major vendor to WIPRO Hydraulics had approached us to solve a bent tube welding automation with torch rotary which now we call as Orbital Welding. This system initially designed to solve one major problem of welding bent tubes that is through interpolative insertion of torch solved another major issue of internal bead consistency with only TIG fusion welding.
Over the years as we researched on the product further for a lot more optimizations we have currently reached our third generation of the Orbital Welders with complete integrated Uranami Welding solution. You can also see a the kind of weld beads achieved by this system in the figure below.