HOT-ROLLED STEEL SHEET FOR NITRIDING AND COLD-ROLLED STEEL SHEET FOR NITRIDING WITH EXCELLENT FATIGUE STRENGTH AND MANUFACTURING METHOD THEREFOR, AS WELL AS AUTOMOBILE PARTS OF EXCELLENT FATIGUE STRENGTH USING SAME

WIPO Patent Application WO/2013/077298

A1

A hot-rolled steel sheet for nitriding or cold-rolled steel sheet for nitriding of excellent fatigue strength, wherein the steel contains appropriate amounts of Cr, V, and B in particular, and the dislocation density within 50 μm from the surface in the sheet thickness direction is 2.0 to 10.0 times the dislocation density at the ¼ position in the sheet thickness direction. The manufacturing method therefor is characterized in that after acid pickling the hot-rolled steel sheet or cold-rolled steel sheet comprising said components, skin pass rolling is performed under the conditions of the rolling reduction being 0.5 - 5.0%, and the ratio F/T of the line load F (kg/mm), which is the rolling mill load divided by the steel sheet board width, to the load per unit area T (kg/mm2), which is applied on the longitudinal direction of the steel sheet, being 8000 or more. Said hot-rolled steel sheet or cold-rolled steel sheet is then molded to produce nitrided automobile parts.

SAKURADA EISAKU (JP)
HIWATASHI SHUNJI (JP)
HAYASHI KUNIO (JP)
SUZUKI SHINICHI (JP)

PCT/JP2012/079991

May 30, 2013

November 19, 2012

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NIPPON STEEL & SUMITOMO METAL CORP (JP)

C22C38/00; B21B1/22; B21B3/00; C21D1/06; C21D9/46; C22C38/32; C23C8/26; C23C8/32; C23C8/38; C23C8/54

JPH0925544A	1997-01-28
JP2005146354A	2005-06-09

HAGIWARA, Yasushi et al. (JP)
Yasushi Hagiwara (JP)

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