Carbon tool steel strip

Abstract

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 μm among the carbides present in the metallographic structure is 0.50-4.30%.

1 . A carbon tool steel strip having a composition comprising 0.8 to 1.2% of carbon by mass % and having a thickness of not more than 1 mm, wherein the strip has a Vickers hardness of 500 to 650 HV, and
 wherein the strip has an area ratio of carbides having an equivalent circle diameter of not less than 0.5 μm among carbides in a metallographic structure is 0.50 to 4.30%, when an observation plane is taken perpendicular to a rolled surface of the strip and parallel to a length direction of the strip and a cross-section is observed at a center portion in a thickness direction of the strip in the observation plane.   
     
     
         2 . The strip according to  claim 1 , wherein the area ratio of the carbides having an equivalent circle diameter of not less than 0.5 μm is 1.50 to 4.00%. 
     
     
         3 . The strip according to  claim 1 , having a thickness of 0.1 to 0.5 mm. 
     
     
         4 . The strip according to  claim 2 , having a thickness of 0.1 to 0.5 mm.