Loading patent…
AssigneeKabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
InventorsYoichi Mukai, Shinji Kozuma, Masahiro Nomura
Estimating the term…
The invention provides a high strength cold rolled steel sheet having excellent chemical conversion treatment property stably even Mo is added aiming high strengthening. The surface property of the cold rolled steel sheet satisfies that the characteristic of 10 μm or more of the maximum depth (Ry) of the unevenness and 30 μm or less of the average spacing (Sm) of the unevenness, and that either one or more preferably both of, the characteristic of the load length ratio (tp40) of the unevenness of the surface is 20% or less, and the characteristic of the difference of the load length ratios (tp60) and (tp40) is 60% or more, is satisfied, and the crack of 3 μm or less width and 5 μm or more depth does not exist on the surface.
A cold rolled steel sheet wherein the maximum depth (Ry) of the unevenness existing on the surface of the steel sheet is 10 gm or more, the average spacing (Sm) of the unevenness is 30 μm or less, the load length ratio (tp40) of the unevenness of the surface is 20% or less, and the crack of 3 μm or less width and 5 μm or more depth does not exist.
A cold rolled steel sheet wherein the maximum depth (Ry) of the unevenness existing on the surface of the steel sheet is 10 μm or more, the average spacing (Sm) of the unevenness is 30 μm or less, the difference of the load length ratios (tp60) and (tp40) of the unevenness of the surface is 60% or more, and the crack of 3 μm or less width and 5 μm or more depth does not exist.
A cold rolled steel sheet wherein the maximum depth (Ry) of the unevenness existing on the surface of the steel sheet is 10 pm or more, the average spacing (Sm) of the unevenness is 30 μm or less, the load length ratio (tp40) of the unevenness of the surface is 20% or less, the difference of the load length ratios (tp60) and (tp40) of the surface is 60% or more, and the crack of 3 μm or less width and 5 μm or more depth does not exist.
Dependencies are inferred from the claim text.