Short-time Annealing Steel Having Ferrite Formed by Strain Induced Dynamic Transformation and Method for Manufacturing the Steel

摘要

PURPOSE: To provide a short-time softening steel for greatly shortening softening heat treatment such as spheroidizing heat treatment by forming fine ferrite by strain induced dynamic transformation, and a method for manufacturing the steel. CONSTITUTION: The short-time softening steel having ferrite formed by strain induced dynamic transformation is characterized in that the steel contains 0.2 wt.% or more of carbon(C) and 0.01 to 0.1 wt.% of niobium(Nb), structure of the steel is composed of ferrite, pearlite and cementite, the ferrite is consisted of ferrite formed by strain induced dynamic transformation and ferrite formed by strain induced static transformation, and the cementite is distributed between the ferrites formed by strain induced dynamic transformation.