Nippon Steel Corporation

Tooru Matsumiya

Wataru Ohashi

Katsuhiro Sasai

Junji Nakashima

Yoshiaki Kimura

Hideaki Yamamura

Yoshiyuki Ueshima

Shozo Mizoguchi

Akihito Kiyose

A steel product for welding includes the following component: by mass %, C: 0.3% or less, Si: 0.5% or less, Mn: 0.3&#x2dc;2%, P: 0.03% or less, S: 0.03% or less, Al: 0.3&#x2dc;5%, O: 0.003&#x2dc;0.01%, and N: 0.006% or less; wherein the balance is composed of Fe and inevitable impurities; wherein Al-containing oxides having a size of 0.005 to 0.05 &#x3bc;m are dispersed in steel at a ratio of 1&#xd7;10/mmor more.

Steel product for welding

The present invention provides a low carbon steel sheet and a low carbon steel slab on which formation of surface defects can be surely prevented by preventing aggregation of inclusions in the molten steel and finely dispersing inclusions in the steel sheet or slab, and a process for producing the steel sheet and slab. The present invention provides a process comprising the steps of decarburizing a molten steel so as to produce a carbon concentration of up to 0.01% by mass, pre-deoxidizing the molten steel by adding Al thereto so as to produce a dissolved oxygen concentration from 0.01 to 0.04% by mass, adding thereto Ti and at least La and/or Ce, and casting the molten steel, and a steel sheet and a steel slab obtained by the process.

Low carbon steel sheet and low carbon steel slab and process for producing same

The .alpha.-stabilizing element, e.g. P, and the .gamma.-stabilizing element, e.g. Mn, do not segregate at an identical site of a casting. Castings are cooled at a rate of 40.degree. C./min or less in a temperature range of the peritectic reaction and/or the Ar.sub.4 transformation, thereby condensing P and Mn into .delta. and .gamma. phases, respectively.

Method for mitigating solidification segregation of steel

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Futtsu, Japan

Tooru Matsumiya