Jfe Steel Corporation

Takenaka Kohmuten Co., Lt.

Tetsuo Mochida

Kenji Ichino

Hiromitsu Shibata

Seiji Ozaki

Makoto Hara

Kou Nishinakagawa

Hidekazu Tsuyoshi

Haruki Kanno

Hideaki Kawarabayashi

Minoru Kawarada

Tsugio Hisaka

Yoichi Itoh

Munekazu Miyaki

There is provided a roll surface layer material including a roll surface layer with excellent fatigue resistance. The roll surface layer material has a composition including, on a mass % basis, C: 2.3% to 2.9%, Si: 0.2% to 0.8%, Mn: 0.2% to 1.0%, Cr: 5.0% to 7.5%, Mo: 4.4% to 6.5%, V: 5.3% to 7.0%, Nb: 0.6% to 1.5%, and Co: 0.1% to 4.0% so as to satisfy 14.0&#x2264;(Mo+1.7V)&#x2264;17.0 (where Mo represents a content (mass %) of Mo and V represents a content (mass %) of V) and further including Al: 0.001% to 0.03% and/or REM: 0.001% to 0.03%, wherein a carbide is contained at an area fraction of 13% to 40%. A composite roll obtained by integrally welding a shaft member to the roll surface layer member is treated as a centrifugal cast roll that includes a surface layer with excellent fatigue resistance.

Roll surface layer material for hot rolling with excellent fatigue resistance produced by centrifugal casting, and composite roll for hot rolling produced through centrifugal casting

A roll outer layer material contains small-size carbides having a circle equivalent diameter of 3 to 30 &#x3bc;m in a number of 500 to 2500 pieces/mmand large-size carbides having a circle equivalent diameter of 50 &#x3bc;m or more in a number of 20 pieces/mmor less, preferably having a chemical composition containing, by mass %, C: 2.4% or more and 2.9% or less, Si: 0.2% or more and 1.0% or less, Mn: 0.2% or more and 1.0% or less, Cr: 4.0% or more and 7.5% or less, Mo: 4.0% or more and 6.5% or less, V: 5.3% or more and 7.0% or less, Nb: 0.5% or more and 3.0% or less, and the balance being Fe and inevitable impurities, in which the contents of Cr, Mo, and V satisfy the relationship 1.5&#x2266;(Cr+Mo)/V&#x2266;2.4.

Roll outer layer material, and composite roll for hot rolling

A surface layer material of a hot rolling mill roll is provided. The surface layer has a chemical composition containing, by mass %, C: 2.4% or more and 3.5% or less, Si: 1.2% or more and 2.4% or less, Mn: 0.2% or more and 2.0% or less, Cr: 0.8% or more and 2.1% or less, Mo: 0.3% or more and 1.1% or less, Ni: 3.0% or more and 6.0% or less, V: 1.0% or more and 2.2% or less, Nb: 0.1% or more and 0.5% or less, REM: 0.0005%) or more and 0.1% or less, Al: 0.003% or more and 0.05% or less, and the balance being Fe and inevitable impurities. The contents of C, Cr, V, Nb, REM, and Al satisfy the relationships Cr+0.2&#x2266;C&#x2212;(0.24&#xd7;V+0.13&#xd7;Nb)&#x2266;3.0 and 0.01&#x2266;REM/Al&#x2266;3.2.

Outer-layer material for hot-rolling roll, and hot-rolling composite roll

A tool for a piercing mill, the tool comprising a scale layer in a surface layer of a substrate steel, wherein the scale layer includes a net structure scale layer that is formed on a substrate steel side, has a thickness of 10 to 200 &#x3bc;m in a depth direction, and is complicatedly intertwined with a metal; and wherein a microstructure on the substrate steel side in a range of at least 300 &#x3bc;m in the depth direction from an interface between the net structure scale layer and the substrate steel contains a ferrite phase at an area fraction of 50% or more, the ferrite phase containing 400/mmor more ferrite grains having a maximum length of 1 to 60 &#x3bc;m.

Tool for piercing mill

A seabed mound creating method suitable for a construction of a large scale offshore structure comprises the steps of setting up a plurality of sheet piles along the outer periphery of a mound creation region in a seabed area of soft ground to form an earth-retaining wall projecting from the seabed, and raising the ground level of the seabed within the earth-retaining wall by depositing soft soil into the earth-retaining wall to heap the deposited soil to a predetermined height. The method further comprises the step of implementing a ground improvement process to both the heaped-up soft soil and the soft ground of the seabed within the earth-retaining wall so that the ground improvement process is provided to a predetermined depth below the seabed, thus to form a seabed mound integral with the improved ground. The seabed mound may be provided at the upper portion with a projection area serving as a shear key with respect to a horizontal external force. Such a seabed mound can eliminate difficulty in supplying mound materials even when constructing a structure in an offshore area. When the ground improvement process is equally implemented to both a seabed ground and the heaped up soft soil, the seabed integrally formed with the improved ground can be created. Thus, a great shear strength due to such an integral structure can resist a horizontal external force, thereby ensuring high security.

Method of creating offshore seabed mound

Growing community of inventors

Tokyo, Japan

Tetsuo Mochida