Question

Describe the heat treatment (temperatures, cooling rates, etc.) to accomplish the following microstructural transformations:

(a) tempered martensite to bainite in a 1085 steel

(b) spherodite to tempered martensite in a 1076 steel

(c) pearlite to bainite in a 1050 steel

Answer 1

Microstructural transformations

Various heat treatment regimes are applied to get selective microstructural tranformations. To accomplish the following microstructural transformations we would need,

(a) tempered martensite to bainite in a 1085 steel : heat at 700°C for of 24 h.

(b) spherodite to tempered martensite in a 1076 steel : This is achieved by austenitizing at a temperature of 760°C, followed by quenching to room temperature at a rate higher than 140°C/s.

(c) peralite to bainite in a 1050 steel : This can be achieved by first austenitizing at a temperature of 760°C followed by rapidly cooling to a temperature range about 220°C and 540°C, finally holding at this temperature for enough time to get bainite microstructure.