PLASTIC WORKING METHOD AND PLASTIC WORKING DEVICE FOR METAL MATERIAL

摘要

Provided is a plastic working method of steel including austenite, the method including: analyzing a strain ratio ²x of an estimated breaking point which is specified during plastic deformation of the steel; heating a steel such that a local temperature T local is within a temperature range indicated by the following expression 1, when T ²x represents a strain-induced-transformation-maximum-ductility-temperature in the unit of °C for the strain ratio ²x, ÃL ²x represents the standard deviation of a fitted curve of critical equivalent strain which depends on the strain ratio ²x on a lower temperature side than T ²x , ÃH ²x represents the standard deviation of a fitted curve of critical equivalent strain which depends on the strain ratio ²x on a higher temperature side than T ²x , and T local represents a local temperature in the unit of °C of the estimated breaking point; and plastically deforming the steel after heating: T ²x - 2 × Ã �¢ L ²x ‰¤ T local ‰¤ T ²x + 1.25 × Ã �¢ H ²x