Al-plated steel sheet for exhaust gas passageway members of motorcycles excellent in high-temperature strength and the members

Abstract

Provided is an Al-plated steel sheet for motorcycle exhaust gas passageway members excellent in high-temperature strength and red scale resistance, which is produced by dipping a substrate steel sheet comprising, in terms of % by mass, at most 0.02% of C, at most 2% of Si, at most 2% of Mn, from 5 to 25% of Cr, from more than 0.1 to 1% of Nb, at most 0.3% of Ti, at most 0.02% of N, and optionally at least one of at most 0.6% of Ni, at most 0.2% of Al, at most 3% of Mo, at most 3% of Cu, at most 3% of W, at most 0.5% of V, at most 0.5% of Co and at most 0.01% of B, with a balance of Fe and inevitable impurities, in a hot-dip Al-base plating bath to thereby form a hot-dip plating layer having a mean thickness of from 3 to 20 μm on the surface thereof.

1 . An Al-plated steel sheet for motorcycle exhaust gas passageway members excellent in red scale resistance, which is produced by dipping a substrate steel sheet comprising, in terms of % by mass, at most 0.02% of C, at most 2% of Si, at most 2% of Mn, from 5 to 25% of Cr, from more than 0.1 to 1% of Nb, at most 0.3% of Ti and at most 0.02% of N with a balance of Fe and inevitable impurities,
 in a hot-dip plating bath containing, in terms of % by mass, from 3 to 12% of Si with a balance of Al and inevitable impurities, then pulling it up, and controlling the plating amount to thereby form a plating layer having a mean thickness of from 3 to 20 μm on the surface thereof.   
   
   
       2 . The Al-plated steel sheet for motorcycle exhaust gas passageway members excellent in red scale resistance as claimed in  claim 1 , wherein the steel sheet of the substrate further contains at least one of at most 0.6% of Ni, at most 0.2% of Al, at most 3% of Mo, at most 3% of Cu, at most 3% of W, at most 0.5% of V, at most 0.5% of Co and at most 0.01% of B. 
   
   
       3 . The Al-plated steel sheet for motorcycle exhaust gas passageway members excellent in red scale resistance as claimed in  claim 1 , wherein the hot-dip plating bath further contains at least one of Ti, B, Sr, Cr, Mn, Mg and Zr in a total amount of at most 1%. 
   
   
       4 . A motorcycle exhaust gas passageway member which is formed of the plated steel sheet of  claim 1  as the constitutive material thereof and which is so designed that the plating layer thereof is kept in contact with exhaust gas and that the maximum service temperature is 400° C. or higher. 
   
   
       5 . The Al-plated steel sheet for motorcycle exhaust gas passageway members excellent in red scale resistance as claimed in  claim 2 , wherein the hot-dip plating bath further contains at least one of Ti, B, Sr, Cr, Mn, Mg and Zr in a total amount of at most 1%. 
   
   
       6 . A motorcycle exhaust gas passageway member which is formed of the plated steel sheet of  claim 2  as the constitutive material thereof and which is so designed that the plating layer thereof is kept in contact with exhaust gas and that the maximum service temperature is 400° C. or higher. 
   
   
       7 . A motorcycle exhaust gas passageway member which is formed of the plated steel sheet of  claim 3  as the constitutive material thereof and which is so designed that the plating layer thereof is kept in contact with exhaust gas and that the maximum service temperature is 400° C. or higher.