Hot dip plated high strength steel sheet for press forming use superior in low temperature toughness
View Patent ↗The present invention provides a hot dip plated high strength steel sheet comprising a cold rolled steel sheet and a hot dip plated layer formed on the surface thereof, characterized in that the cold rolled steel sheet contains, by mass %, C: 0.0005 to 0.0050%, Si: over 0.3 to 1.0%, Mn: 0.70 to 2.0%, P: 0.05% or less, Ti: 0.010 to 0.050%, Nb: 0.010 to 0.040%, B: 0.0005 to 0.0030%, S: 0.010% or less, Al: 0.01 to 0.30%, and N: 0.0010 to 0.01%, and a balance of Fe and unavoidable impurities, and the cold rolled steel sheet has a value of TB* defined by the equation TB*=(0.11−[Ti])/(ln ([B]×10000)) of 0.03 to 0.06, and P is present in an amount of [P]≦10×[B]+0.03, where [Ti] is the Ti content in mass percent, [B] is the B content in mass percent, and [P] is the P content in mass percent.
1. A hot dip Sn-Zn plated high strength steel sheet for press forming, superior in low temperature toughness, comprising a cold rolled steel sheet and a hot dip plated layer formed on the surface of the cold rolled steel sheet, the cold rolled steel sheet comprising, by mass %,
C: 0.0005 to 0.0050%,
Si: 0.61 to 1.0%,
Mn: 0.70 to 1.39%,
P: 0.05% or less,
Ti: 0.010 to 0.018%,
Nb: 0.010 to 0.040%,
B: 0.0007 to 0.0021%,
S: 0.010% or less,
Al: 0.01 to 0.066%,
N: 0.0010 to 0.0041%, and
a balance of Fe and unavoidable impurities, wherein
P is present in an amount of [P]≦10×[B]+0.03, wherein
[B] is the B content in mass percent, and [P] is the P content in mass percent.
2. The hot dip Sn-Zn plated high strength steel sheet as set forth in claim 1 , wherein, when the hot dip plated high strength steel sheet is formed at a drawing ratio of 1.9, the hot dip plated high strength steel sheet has a secondary work embrittlement resistance temperature of −50° C. or less.
3. A hot dip Sn-Zn plated high strength steel sheet for press forming, superior in low temperature toughness, comprising a cold rolled steel sheet and a hot dip plated layer formed on the surface of the cold rolled steel sheet, the cold rolled steel sheet comprising, by mass %,
C: 0.0005 to 0.0050%,
Si: 0.61 to 1.0%,
Mn: 0.70 to 1.39%,
P: 0.05% or less,
Ti: 0.010 to 0.013%,
Nb: 0.010 to 0.040%,
B: 0.0007 to 0.0025%,
S: 0.010% or less,
Al: 0.01 to 0.066%,
N: 0.0010 to 0.0041%, and
a balance of Fe and unavoidable impurities, wherein
P is present in an amount of [P]≦10×[B]+0.03, wherein
[B] is the B content in mass percent, and [P] is the P content in mass percent.
4. The hot dip Sn-Zn plated high strength steel sheet as set forth in claim 3 , wherein, when the hot dip plated high strength steel sheet is formed at a drawing ratio of 1.9, the hot dip plated high strength steel sheet has a secondary work embrittlement resistance temperature of −50° C. or less.