High-strength hot-dip-galvanized steel sheet having excellent moldability, and method for production thereof
A technology of hot-dip galvanized steel sheet and manufacturing method, which is applied in the direction of manufacturing tools, hot-dip coating process, chemical instruments and methods, etc., can solve the problems of reduced formability, stretchability, hole expandability and bendability, etc., to achieve Ensures safety, hole expandability, and excellent bendability
Inactive Publication Date: 2010-12-29
JFE STEEL CORP
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Problems solved by technology
[0003] However, in general, the increase in the strength of the steel sheet leads to a decrease in the tensile properties, hole expandability, and bendability of the steel sheet, which leads to a decrease in formability. Therefore, it is currently expected to have high strength and excellent formability at the same time, as well as excellent corrosion resistance. hot-dip galvanized steel
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[0104] Steel Nos. A to K having the composition shown in Table 1 were melted in a converter and cast into slabs by continuous casting. After heating the obtained steel slab to 1200 degreeC, it hot-rolled at the finishing temperature of 850-920 degreeC, and coiled at the coiling temperature of 600 degreeC. Next, after pickling, it was cold-rolled at a rolling reduction of 50% to the plate thickness shown in Table 2, and annealed under the annealing conditions shown in Table 2 using a continuous hot-dip galvanizing line. Perform heat treatment before plating for the time shown in Table 2, and then immerse in a 475°C galvanizing bath containing 0.13% Al for 3 seconds to form a coating with a coating weight of 45g / m 2 The galvanized layer was alloyed at the temperature shown in Table 2 to produce hot-dip galvanized steel sheets No. 1 to 20.
[0105] In addition, as shown in Table 2, some galvanized steel sheets were not subjected to pre-plating heat treatment and alloying treatme...
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Disclosed is a high-strength hot-dip-galvanized steel sheet having a TS value of 780 MPa or more and having excellent hole-expanding properties and excellent bendability. Also disclosed is a method for producing the steel sheet. The steel sheet has the following chemical composition (% by mass): C: 0.05-0.15%, Si: 0.8-2.5%, Mn: 1.5-3.0%, P: 0.001-0.05%, S: 0.0001-0.01%, Al: 0.001-0.1%, N: 0.0005-0.01%, Cr: 0.1-1.0%, Ti: 0.0005-0.1% and B: 0.0003-0.003%, with the remainder being iron and unavoidable impurities. The steel sheet has a structure composed of a ferrite phase at an area ratio of 30%or more and a martensite phase at an area ratio of 30 to 70% (inclusive), wherein a tempered martensite phase makes up 20% or more of the total area of the martensite phase and a martensite phase having a particle diameter of 1 [mu]m or less makes up 10% or less of the total area of the martensite phase.
Description
technical field [0001] The present invention relates to a high-strength hot-dip galvanized steel sheet excellent in formability mainly suitable for structural parts of automobiles and a method for producing the same, and particularly relates to a high-strength hot-dip galvanized steel sheet having a tensile strength TS of 780 MPa or more and excellent ductility such as hole expandability and bendability. Strength hot-dip galvanized steel sheet and its manufacturing method. Background technique [0002] In recent years, in order to ensure the safety of occupants in the event of a crash and to improve fuel consumption by reducing the weight of the car body, high-strength steel sheets with a TS of 780 MPa or more and a thin plate thickness have been actively used in automotive structural parts. In particular, application of extremely high-strength steel sheets having TS of 980 MPa class and 1180 MPa class is also being studied recently. [0003] However, in general, the increa...
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Login to View More IPC IPC(8): C22C38/00C21D9/46C22C38/38C22C38/58C23C2/06C23C2/28
CPCC22C38/32C23C2/28C22C38/06C23C2/02C22C38/38C22C38/28C23C2/06C22C38/001C21D9/48C22C38/02C22C38/002C22C38/22C22C38/26C22C38/34C22C38/42C22C38/54C22C38/58B32B15/013C22C18/00C22C38/50Y10T428/12799C23C2/29C23C2/024C23C2/0224C23C2/022
Inventor 金子真次郎川崎由康松冈才二铃木善继舞嶽孝二
Owner JFE STEEL CORP