Dual Phase steels

Question 1

Characteristics

Answer 1

> good toughness, ductility, weldability, low DBTT< high work hardening rate, excellent formability, no sharp yield point, low cost
flow stress after cold forming is very high due to high rate of work hardening
low carbon steels with 0.08-0.2wt% carbon and 1.0-1.5wt% Mn
microstructure has ferrite and tempered martensite

Question 2

Isothermal intercritical annealing to produce dual phase steel

Answer 2

1. holding steel in the two phase field to produce required vol % ferrite
2. rapid cooling to room temp so austenite –> martensite
3. continuously cooled through two phase field then rapidly cooled to room temp

Question 3

What does the strength of dual phase steels depend on?

Answer 3

vol fraction of tempered martensite, CC of martensite, ferrite grain size and vol fractions and avg sizes of carbides of the micro alloying elements