Development of a cold spot joining method that enables sound joining of carbon steel below the A₁ temperature

Abstract

A novel solid-state joining method, which we call cold spot joining (CSJ), was successfully developed. In this joining concept, the material in the vicinity of the interface is plastically deformed using high pressure to form the joining interface, and impurities at the interface are expelled to the outside. Medium-carbon steel sheets were joined using the CSJ method under various process conditions. The joining temperature can be modified by the pressure applied during CSJ. Microstructural observations and hardness distributions revealed that proper pressurisation led to a joining temperature below the A₁ point and prevented the formation of brittle martensitic phase. A sound S45C joint showing plug rupture at the base metal under both tensile shear and cross-tension tests was successfully fabricated by providing appropriate applied pressure and energising conditions.

KEYWORDS:

• solid-state joining
• non-transformation joining
• spot joining method
• carbon steel
• pressure control
• microstructure
• mechanical properties

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the JST-Mirai Programme under Grant number JPMJMI19E5; a Grant-in-Aid for Science Research from the Japan Society for the Promotion of Science under Grant number 19H00826; and the JST program for the establishment of university fellowships towards the creation of science technology innovation under Grant number JPMJFS2125.