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High-strength alloyed hot-dipped galvanized steel sheet having excellent workability and delayed fracture resistance, and method for producing same

A technology of hot-dip galvanized steel sheets and high-strength alloys, applied in hot-dip galvanizing processes, chemical instruments and methods, manufacturing tools, etc., can solve the problems of reduced wettability of hot-dip galvanized, failure to galvanize, etc., to achieve Improves bendability and delayed fracture resistance, suppresses hydrogen embrittlement, and has excellent delayed fracture resistance

Inactive Publication Date: 2016-11-16
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, Si and Mn are easily oxidizable elements, and the oxide film formed on the surface with Si oxide, Mn oxide, or a composite oxide of Si and Mn will significantly reduce the wettability of hot-dip galvanizing, resulting in undesired Can be galvanized and other issues

Method used

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  • High-strength alloyed hot-dipped galvanized steel sheet having excellent workability and delayed fracture resistance, and method for producing same
  • High-strength alloyed hot-dipped galvanized steel sheet having excellent workability and delayed fracture resistance, and method for producing same
  • High-strength alloyed hot-dipped galvanized steel sheet having excellent workability and delayed fracture resistance, and method for producing same

Examples

Experimental program
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Embodiment

[0159] A slab containing the composition shown in the following Table 1 and the remainder being iron and unavoidable impurities was heated to 1250°C, hot-rolled to 2.4mm at a finishing temperature of 900°C, and then rolled at the temperature shown in Table 2. Coiled.

[0160] For some examples No.24-26, 35-38, they were then placed in a thermal insulation device made of ceramic fiber, and kept warm under the conditions shown in Table 2. The holding time at 500°C or higher was measured using a thermocouple attached to the outer periphery of the coil.

[0161] Next, the hot-rolled steel sheet obtained as above was pickled under the following conditions, and then cold-rolled at a cold-rolling ratio of 50%. The plate thickness after cold rolling was 1.2 mm.

[0162] Pickling solution: 10% hydrochloric acid, temperature: 82°C, pickling time: as shown in Table 2.

[0163] Next, in the continuous hot-dip Zn plating line, under the conditions shown in Table 2, cooling was performed...

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Abstract

The invention discloses a high-strength alloyed hot-dipped galvanized steel sheet having excellent workability and delayed fracture resistance, and a method for producing the same. Provided is an alloyed hot-dipped galvanized steel sheet which has excellent workability in terms of platability, bendability and hole expandability, while having excellent delayed fracture resistance, and which has a tensile strength of 1,180 MPa or more and an yield ratio (YR) of 73.0% or more. The high-strength plated steel sheet according to the present invention comprises a plating layer on the surface of a base steel sheet, and contains a specific steel component. This high-strength plated steel sheet sequentially comprises, from the interface between the base steel sheet and the plating layer toward the base steel sheet: an internal oxide layer which is present at the interface between the base steel sheet and the plating layer and contains at least one element selected from the group consisting of Si and Mn; a soft layer which includes the internal oxide layer and has a Vickers hardness equal to 90% or less of the Vickers hardness of the base steel sheet at a position of t / 4, where t is the sheet thickness of the base steel sheet; and a hard layer that is configured of a structure mainly composed of martensite. The average depth (D) of the soft layer is 20 [mu]m or more, and the average depth (d) of the internal oxide layer is 4 [mu]m or more and less than (D). The variation coefficient of KAM of the base steel sheet at a position of t / 4 is 0.66 or less.

Description

technical field [0001] The present invention relates to a high-strength alloyed hot-dip galvanized steel sheet having a tensile strength of 1180 MPa or more, a yield ratio YR of 73.0% or more, excellent workability including bendability and hole expandability, and delayed fracture resistance, and its production method. Background technique [0002] Alloyed hot-dip galvanized steel sheets commonly used in the fields of automobiles and conveyors are required not only to have higher strength, but also to have excellent workability in bendability and hole expandability (stretch flangeability). Excellent delayed fracture resistance. Furthermore, it is required to be excellent in impact resistance and absorption (that is, high yield ratio YR). [0003] In order to ensure high strength and workability, it is effective to add a large amount of strengthening elements such as Si and Mn to steel. However, Si and Mn are easily oxidizable elements, and the oxide film formed on the sur...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/46C22C38/60C23C2/02C23C2/06C23C2/28C23C2/40
CPCC22C38/00C21D2211/008B32B15/013C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06C22C38/08C22C38/12C22C38/14C22C38/16C22C38/38C21D9/46Y10T428/12757Y10T428/12792Y10T428/12799Y10T428/12951Y10T428/12958Y10T428/12972B32B15/01B32B15/012C21D8/0205C21D8/0226C21D8/0236C21D8/0263C21D9/48C22C38/28C22C38/32C23C2/02C23C2/06C23C2/28C23C2/0222C23C2/29C23C2/024C23C2/0224C23C2/40B32B15/04B32B15/18C23C30/00C23C30/005
Inventor 池田宗朗中屋道治
Owner KOBE STEEL LTD
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