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Zinc hot-dipped steel sheet

A hot-dip galvanized steel sheet and hot-dip galvanized technology, applied in hot-dip galvanizing process, heat treatment furnace, heat treatment equipment, etc. Excellent corrosion resistance and excellent plating adhesion

Active Publication Date: 2020-04-03
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

If the steel plate is heated to a high temperature, the microstructure inside the steel plate may deteriorate, especially coarse iron-based carbides are likely to be formed, which impairs the properties of the steel plate, so it is not preferable.
[0012] On the other hand, for example, in the hot-dip galvanized steel sheet described in Patent Document 12, unevenness in appearance due to unevenness in the Fe content of the plating layer in the width direction may occur.

Method used

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  • Zinc hot-dipped steel sheet
  • Zinc hot-dipped steel sheet
  • Zinc hot-dipped steel sheet

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0255] "Example 1"

[0256] Cast the slabs with the chemical components (compositions) of A to AK shown in Table 1, and perform hot rolling according to the hot rolling process conditions (slab heating temperature, rolling end temperature) shown in Tables 2 and 3. The hot rolling process conditions shown in 2 and Table 3 (average cooling rate from the end of hot rolling to coiling, coiling temperature, formula (1)) were cooled to obtain a hot-rolled steel sheet.

[0257] Then, the hot-rolled steel sheet was pickled (immersed in 10% hydrochloric acid at 80°C, the immersion time is shown in Table 2 and Table 3), and the cold rolling process conditions (reduction rate) shown in Table 2 and Table 3 Cold rolling is performed to obtain a cold rolled steel sheet.

[0258] Next, follow the heating process conditions in the annealing process shown in Table 4 to Table 7 (air ratio in the preheating zone, Log(P(H 2 O) / P(H 2 )), Log(P(H 2 O) / P(H 2 )), the average heating rate in the temperature...

experiment example 81

[0293] Experimental example 81 is an example in which the C content is low, and the volume fraction of the hard structure V2 in the range of 1 / 8 thickness to 3 / 8 thickness centered on 1 / 4 of the plate thickness is reduced, and good tensile strength is not obtained.

experiment example 82

[0294] Experimental example 82 is an example in which the C content is high and the spot weldability is deteriorated.

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Abstract

In a specific thickness range centering on 1 / 4 of the thickness from the surface of the parent material steel sheet, the ferrite phase has a volume fraction of 0% to less than 50%, the total of hard structures comprising one or more of bainite structure, bainitic ferrite phase, fresh martensite phase and tempered martensite phase has a volume fraction of at least 50%, retained austenite phase hasa volume fraction of 0% to 8%, the total of pearlite phase and coarse cementite phase has a volume fraction of 0% to 8%, and at the interface between the plated layer and the parent material steel sheet, there is an Fe-Al alloy layer having an average thickness of 0.1-2.0 um, and a difference between the maximum thickness and minimum thickness in the steel plate width direction of within 0.5 um. In a refined layer which is in direct contact with the Fe-Al alloy layer, the difference between the maximum thickness and minimum thickness of the refined layer in the width direction of the steel plate is within 2.0 um.

Description

Technical field [0001] The present invention relates to a high-strength hot-dip galvanized steel sheet having excellent ductility, bendability, hole expandability, and coating adhesion during bending deformation, and excellent resistance to continuous bending fatigue. Background technique [0002] For steel plates mainly used for automobile frame members, the demand for higher strength is increasing. In these high-strength steel sheets, in order to obtain high strength and excellent formability, alloy elements represented by Si and Mn, which contribute to the improvement of strength, are generally added. However, the alloying elements represented by Si and Mn also have the effect of reducing the adhesion of the coating. [0003] In addition, since steel sheets for automobiles are generally used outdoors, they generally require excellent corrosion resistance. [0004] However, in applications such as outer panels of automobiles, severe bending processing (edge ​​bending) is generall...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/46C22C38/58C23C2/06C23C2/40
CPCC21D9/46C23C2/06C23C2/40B32B15/013C21D6/005C21D6/001C21D6/002C21D6/008C21D8/0205C21D8/0236C21D2211/001C21D2211/002C21D2211/005C21D2211/008C22C38/002C22C38/005C22C38/02C22C38/06C22C38/08C22C38/16C22C38/22C22C38/26C22C38/28C22C38/38C23C2/02C23C2/29C23C2/024C23C2/0224C22C38/58C22C38/42C22C38/44C22C38/32
Inventor 森下敦司金藤泰平内田智史中田达也山口裕司
Owner NIPPON STEEL CORP