High aluminiferous ferritic stainless steel sheet for weight sensor substrate, method for producing the same, and weight sensor

Abstract

The present invention provides a stainless steel most suitable as a metal base material for the weight sensor substrate of an automobile airbag, a method for producing said stainless steel and said weight sensor; and the stainless steel sheet comprises a high aluminiferous ferritic stainless steel containing Al of 2.5 to 8 mass % and comprising, in mass, C: 0.025% or less, N: 0.025% or less, the sum of C and N being 0.030% or less, and Nb: 0.05 to 0.5%, with the balance consisting of Fe and unavoidable impurities. Further, said stainless steel sheet may further contain, in mass, one or more of V: 0.05 to 0.4%, Ti: 0.02 to 0.2%, and Zr: 0.02 to 0.2%. The present invention makes it possible to control the difference in the average linear expansion coefficient between said stainless steel sheet and crystallized glass for a weight sensor to less than 10% in the temperature range from 20° C. to 900° C. and thus to improve the adhesiveness of said stainless steel sheet with said crystallized glass.

1 . A high aluminiferous ferritic stainless steel sheet for a weight sensor substrate, characterized by comprising a high aluminiferous ferritic stainless steel containing, in mass, 
 Cr: 12 to 30%,    Al: 2.5 to 8%,    Nb: 0.05 to 0.5%,    C: 0.025% or less, and    N: 0.025% or less,    the sum of C and N being 0.030% or less, with the balance consisting of Fe and unavoidable impurities.    
     
     
         2 . A high aluminiferous ferritic stainless steel sheet for a weight sensor substrate according to  claim 1 , characterized in that said high aluminiferous ferritic stainless steel further contains, in mass, one or more of 
 V: 0.05 to 0.4%,    Ti: 0.02 to 0.2%, and    Zr: 0.02 to 0.2%.    
     
     
         3 . A high aluminiferous ferritic stainless steel sheet for a weight sensor substrate according to  claim 1  or  2 , characterized in that the average linear expansion coefficient of said stainless steel is 13.5 to 15.5×10 −6 /° C. in the temperature range from 20° C. to 900° C.  
     
     
         4 . A high aluminiferous ferritic stainless steel sheet for a weight sensor substrate according to  claim 1  or  2 , characterized in that the difference in the average linear expansion coefficient between said stainless steel sheet and crystallized glass for a weight sensor is less than 10% in the temperature range from 20° C. to 900° C.  
     
     
         5 . A high aluminiferous ferritic stainless steel sheet for a weight sensor substrate according to  claim 1  or  2 , characterized in that the thickness of the oxide film of said stainless steel sheet is less than 0.38 μm.  
     
     
         6 . A method for producing a high aluminiferous ferritic stainless steel sheet for a weight sensor substrate, characterized by stamping said high aluminiferous ferritic stainless steel sheet according to  claim 1  or  2  into a desired shape and successively applying heat treatment for 20 to 120 minutes in the temperature range from 800° C. to 900° C.  
     
     
         7 . A weight sensor characterized by being composed of: a weight sensor substrate comprising said high aluminiferous ferritic stainless steel sheet according to  claim 1  or 2; a crystallized glass layer with which the surface of said substrate is covered; strain sensitive resistive elements formed on the surface of said crystallized glass layer; and a pair of electrodes for detecting the change of the electric resistance of said strain sensitive resistive elements.