Method of bonding metallic members, and metallic bonded body

A method of bonding metal members, by which a ring-shaped first metallic member including an opening that penetrates in a thickness direction and a second metallic member including an outer circumferential wall section capable of coming into partial contact with an inner circumferential wall section of the first metallic member that surrounds the opening are bonded to each other by resistance heating through energization while applying pressure in an axial direction of the metallic members,

• the method comprising the steps of:
• forming a first inner diameter section having a predetermined inner diameter and a second inner diameter section having an inner diameter that is greater than the inner diameter of the first inner diameter section on the inner circumferential wall section of the first metallic member;
• forming a first outer diameter section and a second outer diameter section having outer diameters that are greater than the inner diameters of the first inner diameter section and the second inner diameter section respectively by a predetermined amount on the outer circumferential wall section of the second metallic member;
• and
• forming, by respectively abutting the first and second outer diameter sections of the second metallic member against the first and second inner diameter sections of the first metallic member and energizing the first metallic member and the second metallic member by a pair of electrodes arranged to oppose each other, with the first and second inner diameter sections of the first metallic member and the first and second outer diameter sections of the second metallic member interposed therebetween, while pressurizing both metallic members in an axial direction thereof, a first junction where the first inner diameter section and the first outer diameter section are bonded and a second junction where the second inner diameter section and the second outer diameter section are bonded between both metallic members, and further forming a gap in which the metals do not come into contact with each other between both junctions over a predetermined axial length;
• wherein, at the start of bonding of the first metallic member and the second metallic member, the first inner diameter section and the first outer diameter section, and the second inner diameter section and the second outer diameter section, are simultaneously abutted to each other and energization by the electrodes is started in this state;
• the pair of electrodes includes an upper electrode and a lower electrode vertically arranged so as to oppose each other;
• the first metallic member is placed on the lower electrode in a posture where the first inner diameter section is positioned lower than the second inner diameter section;
• and
• the second metallic member is placed under the upper electrode in a posture where the first outer diameter section is positioned lower than the second outer diameter section.