Abstract: The present invention provides (1) diffusion bonding methods for joining metallic materials like carbon steels or stainless steels,interposing a bonding material, such as 10 to 80 .mu.m thick Ni-based alloy with the melting point of 1150.degree. C. or lower,between base materials, heating so that the length heated at 800.degree. C. or above measures from 3 to 20 mm, in case of joining stainless steels a bonded layer, further, being heated between the both melting points, and applying the compressive stress, for example 0.5 to 2 kgf/mm.sup.2, so that a lateral expansion ratio is made within 1.0 to 1.1, and (2) a joined structure having the bonded joint formed thereby.

Abstract: The method provides a diffusion-bonding of dual-phase stainless steel material having excellent strength and corrosion. The method includes: cold-working a material to be bonded so as to enhance the proof stress; inserting into the bonding portion an insert material; applying pressure thereto while performing shielding by mixed nitrogen/argon gas; heating the restricted bonding portion; cooling at a restricted rate; so as to form a bonded portion having the ferritic phase percentage of 30-70% by volume.

Abstract: A method of hot pressure welding of hot steel stock, in which the ends of the steel stock are descaled mechanically and pressure joined under a reducing flame. Since re-oxidation after descaling is prevented and the feasible temperature for hot pressure joining is maintained by the reducing flame, the joining is accomplished firmly and strong joints are obtained.

Abstract: A method of carrying out hot pressure welding of hot steel stock is disclosed, which is effective for achieving a continuous hot rolling line. The hot steel stock to be joined is subjected to butt joining or lap joining in a reducing atmosphere under pressure while under hot conditions.