EFFECT OF MARTENSITE VOLUME FRACTION ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF LOW CARBON DUAL PHASE STEEL

The purpose of this work is to study the effect of the difference intercriticalannealing temperatures, which produce dual-phase microstructure of ferriteand various percentages of martеnsite volume fractions (MVF) in dualphasesteel, and its influence on microstructure and mechanic properties.Dual phase steel (DPS) was developed from low carbon steel, which hasgood machinability using an intercritical annealing heat treatment. Theintercritical annealing made by water quenching low carbon steel from threedifferent temperatures (740, 760, and 780 ºC) to obtain different martensitevolume fraction (MVF). The microstructure of (DPS) resulting afterintercritical annealing contains bands of martensitic isles formed around theferrite grains. The martinsite volume fraction increases by increase thetemperature of intercritical annealing treatment. Dual phase steel showedlarge improvement in hardness and tensile properties with increasingmartensite volume fraction. Also fatigue strength, and endurance limitincrease with increasing (MVF). While wear resistance improved at (760and 780 ºC) and decrease at (740 ºC).

Keywords:

Dual phase steel , Intercritical annealing , Martensite volume fraction (MVF) , Low carbon steel