Steel sheets, plated steel sheets and methods for their manufacture
A manufacturing method and steel plate technology, applied in the direction of manufacturing tools, hot-dip coating process, furnace, etc., can solve the problems of steel plate formability reduction, formability reduction, forming cracks, etc., to achieve high utilization value, fuel consumption efficiency improvement, expansion The effect of excellent porosity
Active Publication Date: 2020-06-30
JFE STEEL CORP
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Problems solved by technology
[0003] However, in general, increasing the strength of the steel sheet leads to a decrease in the formability, so when the strength is increased, the formability of the steel sheet decreases, and problems such as cracks during forming occur.
Therefore, it is impossible to simply try to reduce the thickness of the steel plate
Method used
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[0168] A steel having the composition shown in Table 1 and the remainder consisting of Fe and unavoidable impurities was melted in a converter, and a slab was produced by a continuous casting method. The obtained slabs were made into the following various steel plates under the conditions shown in Table 2.
[0169] That is, after hot rolling, at Ac 1 Phase transition point+20℃~Ac 1 Transformation point + 120 ° C for annealing, after cold rolling (sometimes cold rolling is not implemented), in Ac 1 Phase transition point+10℃~Ac 1 Annealing is performed at +100°C at the phase transition point. Thereafter, cold-rolled steel sheets (CR) are obtained, and further, a coating treatment is performed to obtain hot-dip galvanized steel sheets (GI), alloyed hot-dip galvanized steel sheets (GA), hot-dip aluminum-coated steel sheets (Al) and electro-galvanized steel sheets. Steel plate (EG), etc.
[0170] It should be noted that as a hot-dip galvanizing bath, a zinc bath containing 0....
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Abstract
A steel plate with a specified composition: in terms of area ratio, polygonal ferrite is 20% to 65%, unrecrystallized ferrite is more than 8%, and martensite is 5% to 25%. Calculated, the retained austenite is more than 8%, and the average aspect ratio of the grains of each phase (polygonal ferrite, martensite, and retained austenite) is 2.0 to 15.0. In addition, the above-mentioned polygonal ferrite The average grain size of the above-mentioned martensite is 6 μm or less, the average grain size of the above-mentioned martensite is 3 μm or less, the average grain size of the above-mentioned retained austenite is 3 μm or less, the amount of Mn (mass %) in the above-mentioned retained austenite divided by The value obtained by the amount of Mn (mass %) in the above-mentioned polygonal ferrite is 2.0 or more, thereby having a TS of 590 MPa or more and a YR of 68% or more, which is excellent in formability and has a relatively high yield ratio and hole-expanding high-strength steel plates.
Description
technical field [0001] The present invention relates to steel sheets, hot-dip galvanized steel sheets, hot-dip aluminized steel sheets, and electro-galvanized steel sheets and their manufacturing methods, and in particular to a component suitable for use in automotive, electric and other industrial fields with excellent formability and hole expandability And has a higher yield ratio of the steel plate. Background technique [0002] In recent years, improving the fuel efficiency of automobiles has become an important issue from the viewpoint of protecting the global environment. Therefore, initiatives to reduce the weight of the vehicle body itself by increasing the strength of the steel plate used as the material of the vehicle body to achieve thinning are becoming more and more active. [0003] However, in general, increasing the strength of a steel sheet leads to a reduction in formability, and therefore, when the strength is increased, the formability of a steel sheet is...
Claims
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IPC IPC(8): C22C38/00C21D9/46C22C38/14C22C38/60
CPCC21D9/46C22C38/14C21D8/0226C21D8/0236C21D8/0263C23C2/06C23C2/12C22C38/02C22C38/04C21D2211/001C21D2211/005C21D2211/008C23C2/28C23C2/40C23C2/024C23C2/0224C22C38/001C21D8/0205C22C38/002C22C38/005C22C38/008C22C38/06C22C38/08C22C38/12C22C38/16C22C38/28C22C38/38C22C38/60
Inventor 山下孝子川崎由康小林崇植野雅康长泷康伸
Owner JFE STEEL CORP