C - Chemistry – Metallurgy – 22 – C
Patent
C - Chemistry, Metallurgy
22
C
C22C 38/00 (2006.01) C21D 9/46 (2006.01) C22C 38/38 (2006.01) C22C 38/58 (2006.01) C23C 2/06 (2006.01) C23C 2/28 (2006.01)
Patent
CA 2693963
The present invention provides a high-strength galvanized steel sheet with low YP and excellent uniformity and a method for producing the same. A high-strength galvanized steel sheet has a steel composition which contains, by % by mass, 0.01 to 0.12% of C, 0.2% or less of Si, less than 2% of Mn, 0.04% or less of P, 0.02% or less of S, 0.3% or less of sol. Al, 0.01% or less of N, and over 0.3% to 2% of Cr, and which satisfies 2.1 <= [Mneq] <= 3 and 0.24 <= [%Cr]/[%Mn], the balance being composed of iron and inevitable impurities, and has a steel microstructures containing ferrite and a second phase, wherein the area ratio of the second phase is 2 to 25%, the area ratio of pearlite or bainite in the second phase is 0% to less than 20%, the average grain diameter of the second phase is 0.9 to 7 µm, and the area ratio of grains with a grain diameter of less than 0.8 µm in the second phase is less than 15%. Herein, [Mneq] represents the Mn equivalent shown by [Mneq] =[%Mn] + 1.3[%Cr] and [%Mn] and [%Cr] represent the contents of Mn and Cr, respectively.
L'invention porte sur une feuille d'acier laminé à froid, de haute résistance, de faible limite élastique, avec une moindre fluctuation de la qualité de la matière. Cette feuille d'acier comprend, en masse, 0,01 à 0,12 % de C, 0,2 % ou moins de Si, moins de 2 % de Mn, 0,04 % ou moins de P, 0,02 % ou moins de S, 0,3 % ou moins d'Al sol, 0,01 % ou moins de N et plus de 0,3 à 2 % de Cr de telle sorte que les relations 2,19 < ([%Mn] + 1.3 OE[%Cr]) < 3 et 0,24 = [%Cr] / [%Mn] soient satisfaites ([%Mn] et [%Cr] représentent les teneurs en respectivement Mn et Cr) et comprenant, comme complément, le fer et les impuretés inévitables, laquelle feuille d'acier a de la ferrite et la seconde phase de rapport surfacique de 2 à 25 %. Dans la seconde phase, le rapport surfacique de perlite ou de bainite est inférieur à 20 %, et le diamètre moyen de grain de la seconde phase se situe dans la plage de 0,9 à 7 µm. Dans la seconde phase, le rapport surfacique de grains de moins de 0,8 µm de diamètre de grain est inférieur à 15 %.
Fujita Takeshi
Kimura Hideyuki
Okuda Kaneharu
Ono Yoshihiko
Sakurai Michitaka
Jfe Steel Corporation
Ridout & Maybee Llp
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