Forms and Roles of Bismuth in Steel: A Review

Abstract

Bismuth (Bi), as a green free-cutting metal element, has been used for the production of free-cutting steels in the field of free-cutting steel for a couple of decades. One of the merits of bismuth is to improve the machinability of steel, while more Bi addition to steel causes cracking of steels during thermal rolling, attributed to the formation of liquid Bi films. Due to a lack of summary, people have limited mastering the Bi-bearing steels. Herein, the forms and roles of Bi in steel based on the literature survey are summarized. These specific reviews concentrate on the forms, mechanical properties, segregation, solidification, and solubility of Bi in steel, and the effect on grain, machinability, and thermal expansion of steel is also reviewed. This review is of great significance in advancing the understanding of Bi-bearing steels.

Source Apportionment of Particulate Matter in a Metal Workshop

“…Several techniques were reported for Unit 5, but no specific materials were reported for these techniques. We presume that different free machining steels were used, which often contain Bi for better mechanical properties during machining [ 50 ]. In addition to steel, other materials, such as Wood’s metal (which also contains Bi) or zinc alloys, are also commonly used for machining.…”