Hitachi Metals, Ltd.

Proterial, Ltd.

Hiroyoshi Fujihara

Tomonori Ueno

Ichirou Kishigami

A martensitic stainless steel strip capable of achieving higher fatigue strength. This martensitic stainless steel strip has a martensite structure and has a thickness of 1 mm or less, and is characterized in that the compressive residual stress at a surface of the steel strip is 50 MPa or more and the areal ratio of carbides present in the metal structure of the steel strip is 0.5-8.0%. The compressive residual stress at a surface of the steel strip is preferably such that the compressive residual stress in a direction perpendicular to rolling is at least 50 MPa greater than the compressive residual stress in the direction of rolling.

Martensitic stainless steel strip and method for producing same

In the method of producing a martensitic stainless steel strip, a quenching furnace of a quenching process includes at least a temperature raising unit and a holding unit. When a predetermined quenching temperature is set as T (&#xb0; C.), the temperature raising unit is set to be within a temperature range of 0.7T (&#xb0; C.) or higher and lower than T (&#xb0; C.), and a set heating temperature on an exit side of the steel strip is set to be higher than a set heating temperature on an entry side of the steel strip when the steel strip passes through the temperature raising unit. The holding unit is set to the quenching temperature T (&#xb0; C.). A time spent in the furnace by the steel strip in the temperature raising unit is equal to or longer than a time spent in the furnace by the steel strip in the holding unit.

Method of producing martensitic stainless steel strip

Provided is a carbon tool steel strip suitable for use in various spring materials, valve materials, and the like, in which press punching properties and fatigue characteristics are enhanced. A carbon tool steel strip having a thickness of 1 mm or less and a carbon tool steel composition containing 0.8-1.2% C by mass %, wherein the carbon tool steel strip has a Vickers hardness of 500-650 (Hv), and when a cross-section at the center in the sheet thickness direction of the carbon tool steel strip is viewed with the plane of observation in a direction at a right angle to a rolled surface of the carbon tool steel strip and in the length direction of the carbon tool steel strip, the area ratio of carbides having an equivalent circle diameter of at least 0.5 &#x3bc;m among the carbides present in the metallographic structure is 0.50-4.30%.

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Tokyo, Japan

Hiroyoshi Fujihara