High-strength plated steel sheet having superior plating properties, workability, and delayed fracture resistance, and method for producing same
a technology of high-strength plated steel and workability, which is applied in the direction of solid-state diffusion coating, surface reaction electrolytic coating, metallic material coating process, etc., can solve problems such as unplating, and achieve excellent workability, effective suppression of hydrogen embrittlement, and delayed fracture resistance
Inactive Publication Date: 2016-06-09
KOBE STEEL LTD
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The patent describes a plated steel sheet that has a plated layer, an internal oxide layer, a soft layer, and a hard layer. The internal oxide layer is controlled to have a large average depth, which acts as a hydrogen trap site, to effectively suppress hydrogen embrittlement. The plated steel sheet has high strength and good workability, including bending workability and hole expandability, as well as delayed fracture resistance. The relationship between the average depth of the internal oxide layer and the average depth of the soft layer is appropriately controlled to further improve bending workability and delayed fracture resistance.
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[0117]A slab having a composition shown in Table 1 below with a balance of iron and inevitable impurities was heated to 1250° C., subjected to hot rolling at a finish rolling temperature of 900° C. to 2.4 mm, and then wound at a temperature shown in Table 2.
[0118]For some examples Nos. 26 to 28, the slab was placed in a thermal insulating device of ceramic fibers, and the temperature was kept under conditions shown in Table 2. The time in which the temperature was kept at 500° C. or more was measured with a thermocouple attached to an outer circumferential portion of a coil.
[0119]Then, the thus-obtained hot-rolled steel sheet was pickled under conditions described below, and then cold rolled at a cold rolling percentage of 50%. The thickness after the cold rolling was 1.2 mm.[0120]Pickling solution: 10% hydrochloric acid, Temperature: 82° C.[0121]Pickling time: shown in Table 2.
[0122]Thereafter, in a continuous calvanizing line, annealing (oxidation and reduction) and cooling were p...
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Abstract
The present invention relates to a high-strength plated steel sheet having a plated layer on a surface of a base steel sheet, contains predetermined steel compositions, and includes, in order from a base steel sheet side of an interface between the base steel sheet and the plated layer: a soft layer having a Vickers hardness of 90% or less of a Vickers hardness of a t / 4 portion of the base steel sheet, where t is a thickness of the base steel sheet, and a hard layer having a structure containing martensite and bainite as main components. The soft layer has an average depth D of 20 μm or more, an internal oxide layer has an average depth d of 4 μm or more and less than D.
Description
TECHNICAL FIELD[0001]The present invention relates to a high-strength plated steel sheet having a tensile strength of 980 MPa or more and excellent in plating properties, workability including both bending workability and hole expandability, and delayed fracture resistance, and to a method for producing the high-strength plated steel sheet. The plated steel sheets according to the present invention include a hot-dip galvanized steel sheet and an alloyed hot-dip galvanized steel sheet.BACKGROUND ART[0002]A hot-dip galvanized steel sheet and an alloyed hot-dip galvanized steel sheet, which are generally used for various fields including automobiles and aircrafts, are required of having high strength and being excellent in workability including bending workability and hole expandability (stretch flange formability), and delayed fracture resistance. These sheets are also required of being excellent in shock absorption.[0003]To obtain high strength and excellent workability, it is effect...
Claims
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Login to View More IPC IPC(8): C23C2/06C21D9/46C21D6/00C21D8/02C21D1/74C22C38/38C22C38/34C22C38/28C22C38/16C22C38/14C22C38/12C22C38/08C22C38/06C22C38/04C22C38/02C22C38/00C23C8/18
CPCC23C2/06C22C38/001C21D9/46C21D6/004C21D6/005C21D6/008C21D8/0205C21D8/0226C21D8/0236C21D8/0257C21D8/0263C21D1/74C22C38/38C22C38/34C22C38/28C22C38/16C22C38/14C22C38/12C22C38/08C22C38/06C22C38/04C22C38/02C22C38/002C23C8/18C23C2/40C21D9/48C22C38/00C23C2/02C23C28/3225C23C28/345C21D9/561C21D2211/002C21D2211/008B32B15/01B32B15/012Y10T428/12792B32B15/013Y10T428/12757Y10T428/12951Y10T428/12958Y10T428/12799Y10T428/12972C23C2/0222C23C2/024C23C2/0224B32B15/043C23C30/005C23C30/00B32B15/04B32B15/18
Inventor IKEDA, MUNEAKI
Owner KOBE STEEL LTD