Method for manufacturing dissimilar material joint structure, and dissimilar material joint structure

A joint structure of dissimilar materials comprising:

• an aluminum or aluminum alloy material;
• a low-temperature thermal spray coating formed on at least a part of a surface of the aluminum or aluminum alloy material and formed by low-temperature thermal spraying a metal powder of at least one metal selected from the group consisting of pure iron, carbon steel, stainless steel, nickel, a nickel alloy, cobalt, and a cobalt alloy;
• a steel material overlapped on the low-temperature thermal spray coating;
• and
• a weld metal by which a fusion zone is formed in the steel material, the low-temperature thermal spray coating, and the aluminum or aluminum alloy material.

A method for manufacturing a joint structure of dissimilar materials, the method comprising:

• forming a low-temperature thermal spray coating on at least a part of a surface of an aluminum or aluminum alloy material by low-temperature thermal spraying a metal powder of at least one metal selected from the group consisting of pure iron, carbon steel, stainless steel, nickel, a nickel alloy, cobalt, and a cobalt alloy;
• overlapping the aluminum or aluminum alloy material and a steel material such that the low-temperature thermal spray coating and the steel material face each other;
• and
• joining the aluminum or aluminum alloy material and the steel material by a laser welding from a steel material side,
• wherein the joining is performed by laser radiation at least twice under a condition in which the low-temperature thermal spray coating is partially penetrated, and an amount of heat input in a second or subsequent laser radiation is equal to or less than an amount of heat input in a first laser radiation.