Duplex stainless steel sheet with excellent press-formability

Abstract

The present invention provides a duplex stainless steel sheet with excellent press-formability which defines the ingredients of the steel, Ni balance, and austenite phase rate to obtain a 0.2% proof stress and Erichsen value equal to that of SUS304 or another austenitic stainless steel, that is, a duplex stainless steel sheet which contains, by mass %, C: 0.05% or less, Si: 0.5 to 3%, Mn: 1 to 5%, Cr: 16 to 21%, Ni: 1 to 6%, Cu: 0.5 to 3%, and N: 0.07% or less, has an Ni-bal. value given by the following formula <1> of −7.5 to −3.5, has a balance of Fe and unavoidable impurities, has an austenite phase rate of 50% to 95%, and has a balance of ferrite phases: Ni-bal.=30(C+N)+Ni+0.5Mn+0.3Cu−1.1(Cr+1.5Si)+8.2   <1>

1 . A duplex stainless steel sheet with excellent press-formability characterized by containing, by mass %,
 C: 0.05% or less,   Si: 0.5 to 3%,   Mn: 1 to 5%,   Cr: 16 to 21%,   Ni: 1 to 6%,   Cu: 0.5 to 3%, and   N: 0.07% or less   having an Ni-bal value given by the following formula <1> of −7.5 to −3.5, having a balance of Fe and unavoidable impurities, having an austenite phase rate of 50% to 95%, and having a balance of ferrite phases:
   Ni-bal=30(C+N)+Ni+0.5Mn+0.3Cu−1.1(Cr+1.5Si)+8.2   formula <1>
 
   
     
     
         2 . A duplex stainless steel sheet with excellent press-formability as set forth in  claim 1  characterized in that said steel further contains, by mass %, one or more of:
 Mo: 1% or less, 
 Nb: 0.5% or less, 
 V: 0.5% or less, 
 Ti: 0.5% or less, 
 Sn: 1% or less, 
 Sb: 1% or less, 
 W: 1% or less, and 
 Al: 0.1% or less. 
 
     
     
         3 . A duplex stainless steel sheet with excellent press-formability as set forth in  claim 1  or  2  characterized in that said steel further contains, by mass %, one or more of
 B: 0.01% or less, 
 Ca: 0.01% or less, 
 Mg: 0.01% or less, 
 La: 0.3% or less, 
 Ce: 0.3% or less, 
 Zr: 0.3% or less, and 
 Y: 0.3% or less. 
 
     
     
         4 . A duplex stainless steel sheet with excellent press-formability as set forth in  claim 1  or  2  characterized in that a 0.2% proof stress in a tensile test is less than 400 MPa and an elongation at break is 35% or more. 
     
     
         5 . A duplex stainless steel sheet with excellent press-formability as set forth in  claim 3  characterized in that a 0.2% proof stress in a tensile test is less than 400 MPa and an elongation at break is 35% or more. 
     
     
         6 . A duplex stainless steel sheet with excellent press-formability as set forth in  claim 1  or  2  characterized in that a formed height found by an Erichsen test (Erichsen value) is 11 mm or more. 
     
     
         7 . A duplex stainless steel sheet with excellent press-formability as set forth in  claim 3  characterized in that a formed height found by an Erichsen test (Erichsen value) is 11 mm or more. 
     
     
         8 . A duplex stainless steel sheet with excellent press-formability as set forth in  claim 4  characterized in that a formed height found by an Erichsen test (Erichsen value) is 11 mm or more. 
     
     
         9 . A duplex stainless steel sheet with excellent press-formability as set forth in  claim 5  characterized in that a formed height found by an Erichsen test (Erichsen value) is 11 mm or more.