Source blank for stainless steel three-ply clad sheet, production methods of clad steel plate and sheet for solid polymer type fuel cell separator, and solid polymer type fuel cell separator

A method for producing a source blank for a stainless steel three-ply clad sheet, comprising producing a source blank for clad steel sheet composed of a stainless steel having a B content of 0 to 0.3% by mass as a core component and a stainless steel having a B content of 0.3 to 2.5% by mass as face components, the face components each being combined each of major faces of the core component through steps shown by the following Steps 1 to 7:

• Step 1:
• piling the face components on the core component so that each relevant face of the core component to be clad contacts with the relevant face of the face components in cladding relation therewith to thereby obtain a piled block;
• Step 2:
• disposing, on side end faces, other than a working plane, of the piled block obtained in Step 1, protectors with a length covering the total thickness of the piled block, and a length greater than the length of the side end faces of the piled block, and disposing tabs each in abutting relation with an extension of the protector's face to abut on the side end face of the piled block, where the extension is an extra length portion exceeding the length of the side end faces on two face of the piled block;
• Step 3:
• performing bonding at boundary regions between the tabs and the protectors disposed in Step 2 and between the face components and the protectors, in such a manner that the boundary regions between the tab and the protector becomes a starting point of the bonding;
• Step 4:
• removing the tabs and extended portions of the protectors bonded with the tabs to thereby obtain a bonded composite of the core component, face components and protectors;
• Step 5:
• disposing tabs at end portions of the boundary regions between the face components and the protectors onto the working plane of the bonded composite of the core component, face components and protectors produced in Step 4 so that one of faces of each tab forms the same plane with the side end face on which no protector is disposed in Step 2;
• Step 6:
• performing, in the bonded composite of the core component, face components and protectors, after having the tabs disposed thereon in Step 5, bonding at the boundary regions between the face components and the core component on the side end faces on which no protector is disposed, in such a manner that the protector becomes a starting point of the bonding, and further bonding at the boundary regions between the face components and the protectors and at the boundary regions between the core component and the protectors on the side end faces in such a manner that the tab becomes a starting point of the bonding;
• and
• Step 7:
• removing the tabs to thereby obtain the source blank for the stainless steel three-ply clad sheet.