摘要:
An object of the present invention is to provide a cold-rolled steel sheet and an alloyed hot-dip galvanized steel sheet in which tensile strength is effectively increased by press forming and heat treatment while maintaining excellent deep drawability in press forming. Specifically, a steel composition contains less than 0.01% of C, 0.005 to 1.0% of Si, 0.01 to 1.0% of Mn, 0.005 to 0.050% of Nb, 0.005 to 0.030% of Al, 0.005 to 0.040% of N 0.0005 to 0.0015% of B, 0.05% or less of P, and 0.01% or less of S, the balance substantially composed of Fe, in which the following equations (1) and (2) are satisfied: N %null0.00-15null4/93nullNb %null14/27nullAl %null14/11nullB %nullnull(1) C %null(12/93)nullNb %nullnull(2)
摘要:
The present invention presents a high tensile strength cold rolled steel sheet having excellent formability, impact resistance and strain age hardening characteristics, and the production thereof. As a specific means, a slab having a composition which contains, by mass %, 0.15% or less of C, 0.02% or less of Al, and 0.0050 to 0.0250% of N at N/Al of 0.3 or higher, and has N in a solid solution state at 0.0010% or more, is first hot rolled at the finish rolling delivery-side temperature of 800null C. or above, and is subsequently coiled at the coiling temperature of 750null C. or below to prepare a hot rolled plate. Then, after cold rolling, the hot rolled plate is continuously cooled at a temperature from the recrystallization temperature to 900null C. at a holding time of 10 to 120 seconds, and is cooled by primary cooling in which the hot rolled plate is cooled to 500null C. or below at a cooling rate of 10 to 300null C./s, and furthermore if necessary, by secondary cooling in which a residence time is 300 seconds or less in a temperature range of the primary cooling stopping temperature or higher and 350null C. or higher. Provided is a steel sheet containing a ferritic phase having an average crystal grain size of 10 nullm or less at an area ratio of 50% or more, and if necessary, a martensitic phase at an area ratio of 3% or more as a second phase.
摘要:
An object of the present invention is to provide a cold-rolled steel sheet and an alloyed hot-dip galvanized steel sheet in which tensile strength is effectively increased by press forming and heat treatment while maintaining excellent deep drawability in press forming. Specifically, a steel composition contains less than 0.01% of C, 0.005 to 1.0% of Si, 0.01 to 1.0% of Mn, 0.005 to 0.050% of Nb, 0.005 to 0.030% of Al, 0.005 to 0.040% of N, 0.0005 to 0.0015% of B, 0.05% or less of P, and 0.01% or less of S, the balance substantially composed of Fe, in which the following equations (1) and (2) are satisfied:N%null0.0015null14/93.Nb%null14/27.Al%null14/11.B%nullnull(1)C%null(12/93).Nb%nullnull(2)
摘要:
An object of the present invention is to provide a cold-rolled steel sheet and an alloyed hot-dip galvanized steel sheet in which tensile strength is effectively increased by press forming and heat treatment while maintaining excellent deep drawability in press forming. Specifically, a steel composition contains less than 0.01% of C, 0.005 to 1.0% of Si, 0.01 to 1.0% of Mn, 0.005 to 0.050% of Nb, 0.005 to 0.030% of Al, 0.005 to 0.040% of N, 0.0005 to 0.0015% of B, 0.05% or less of P, and 0.01% or less of S, the balance substantially composed of Fe, in which the following equations (1) and (2) are satisfied: N %null0.0015null14/93.Nb %null14/27.Al %null14/11.B %nullnull(1) C %null(12/93).Nb %nullnull(2)
摘要:
The present invention presents a high tensile strength cold rolled steel sheet having excellent formability, impact resistance and strain age hardening characteristics, and the production thereof. As a specific means, a slab having a composition which contains, by mass %, 0.15% or less of C, 0.02% or less of Al, and 0.0050 to 0.0250% of N at N/Al of 0.3 or higher, and has N in a solid solution state at 0.0010% or more, is first hot rolled at the finish rolling delivery-side temperature of 800null C. or above, and is subsequently coiled at the coiling temperature of 750null C. or below to prepare a hot rolled plate. Then, after cold rolling, the hot rolled plate is continuously cooled at a temperature from the recrystallization temperature to 900null C. at a holding time of 10 to 120 seconds, and is cooled by primary cooling in which the hot rolled plate is cooled to 500null C. or below at a cooling rate of 10 to 300null C./s, and furthermore if necessary, by secondary cooling in which a residence time is 300 seconds or less in a temperature range of the primary cooling stopping temperature or higher and 350null C. or higher. Provided is a steel sheet containing a ferritic phase having an average crystal grain size of 10 nullm or less at an area ratio of 50% or more, and if necessary, a martensitic phase at an area ratio of 3% or more as a second phase.
摘要:
An object of the present invention is to provide a cold-rolled steel sheet and an alloyed hot-dip galvanized steel sheet in which tensile strength is effectively increased by press forming and heat treatment while maintaining excellent deep drawability in press forming. Specifically, a steel composition contains less than 0.01% of C, 0.005 to 1.0% of Si, 0.01 to 1.0% of Mn, 0.005 to 0.050% of Nb, 0.005 to 0.030% of Al, 0.005 to 0.040% of N, 0.0005 to 0.0015% of B, 0.05% or less of P, and 0.01% or less of S, the balance substantially composed of Fe, in which the following equations (1) and (2) are satisfied: N %null0.0015null14/93.Nb %null14/27.Al %null14/11.B % nullnull(1) C %null(12/93).Nb % nullnull(2)
摘要:
An object of the present invention is to provide a cold-rolled steel sheet and an alloyed hot-dip galvanized steel sheet in which tensile strength is effectively increased by press forming and heat treatment while maintaining excellent deep drawability in press forming. Specifically, a steel composition contains less than 0.01% of C, 0.005 to 1.0% of Si, 0.01 to 1.0% of Mn, 0.005 to 0.050% of Nb, 0.005 to 0.030% of Al, 0.005 to 0.040% of N, 0.0005 to 0.0015% of B, 0.05% or less of P, and 0.01% or less of S, the balance substantially composed of Fe, in which the following equations (1) and (2) are satisfied: N%null0.0015null14/93nullNb%null14/27nullAl%null14/11nullB% nullnull(1) C%null(12/93)nullNb%nullnull(2)