Stainless steel material for diffusion bonding

Abstract

Provided is a stainless steel material suitable for diffusion bonded moldings in which diffusion bondability has been further improved without being affected by the extent of surface roughness. The present invention is a stainless steel material for diffusion bonding in which the metal structure before diffusion bonding has a multi-phase structure obtained from two or more of a ferrite phase, a martensite phase and an austenite phase, wherein: the mean crystal grain diameter in the multi-phase structure is not more than 20 μm; γmax represented by formula (a) is 10-90; and creep elongation when a 1.0 MPa load is applied at 1000° C. for 0.5 his at least 0.2%. γmax=420C−11.5Si+7Mn+23Ni−11.5Cr−12Mo+9Cu−49Ti−47Nb−52Al+470N+189 . . . Formula (a) The element notations in formula (a) represent the contents (mass %) of the respective elements.

1 . A dual-phase stainless steel material for diffusion bonding, a metal structure before diffusion bonding having a dual-phase structure composed of at least two phases of a ferrite phase, a martensite phase, or an austenite phase, wherein
 the dual-phase structure has an average crystal grain size of 20 μm or less,   γmax represented by the formula (a) mentioned below is 10 to 90, and   creep elongation is 0.2% or more when a load of 1.0 MPa is applied at 1,000° C. for 0.5 hour:
   γmax=420C−11.5Si+7Mn+23Ni−11.5Cr−12Mo+9Cu−49Ti−47Nb−52Al+470N+189  Formula (a)
 
   where an element symbol in the formula (a) mentioned above denotes the content (% by mass) of each element.   
     
     
         2 . The stainless steel material for diffusion bonding according to  claim 1 , comprising, in % by mass: C: 0.2% or less, Si: 1.0% or less, Mn: 3.0% or less, P: 0.05% or less, S: 0.03% or less, Ni: 10.0% or less, Cr: 10.0 to 30.0%, N: 0.3% or less, Ti: 0.15% or less, and Al: 0.15% or less, with the remainder being Fe and inevitable impurities, wherein the total amount of Ti and Al is 0.15% or less. 
     
     
         3 . The stainless steel material for diffusion bonding according to  claim 1 , further comprising, in % by mass: one or two or more elements of Nb: 4.0% or less, Mo: 0.01 to 4.0%, Cu: 0.01 to 3.0%, and V: 0.03 to 0.15%. 
     
     
         4 . The stainless steel material for diffusion bonding according to  claim 1 , further comprising, in % by mass: B: 0.0003 to 0.01%.