Dual Phase Steel

ME 322 Term Paper

Dual Phase Steel

Dual phase steel is a high strength steel with a microstructure that is made up of both ferrite and martensite. The martensite typically makes up somewhere between 10-40% of the volume and is embedded in ductile ferrite matrix. If you were to increase the volume per cent martensite you would increase the strength of the steel and will decrease the ductility. This type of steel is a good mix of high strength and formability, at a relatively low production cost it is an optimal choice for the automotive industry. This is mainly used for the outer paneling of vehicles and the safety cage. The advantages of using dual phase steel (and the reason it is used over a more conventional HSLA steels) is that it is lighter and can lower the overall weight of any part it is used in. This microstructure gives the steel an ultimate tensile strength value of between approximately 400 to 1200 MPa.

There are also many different kinds of dual phase alloys. Some alloy even have some amount of bainite in the microstructure. Some vary the amount of carbon content in the steel, carbon content from between .06 - .15 wt. % will act as an austenite stabilizer and strengthen the martensite in the material. If Manganese is added in the range of 1.5 – 3 wt. % it will also act as an austenite stabilizer but it will also slow ferrite formation. Similar effects occur when adding small amounts of other elements. The heat treatment process for dual phase steel involves controlled cooling from the austenite phase of from two-phase ferrite plus austenite phase during an intercritical annealing treatment step. This works to transform the austenite into ferrite before rapid cooling turns the remaining austenite into martensite.

References:

"Dual Phase Steels." Dierk-raabe.com. Web. 16 Feb. 2016. <http://www.dierk-raabe.com/dual-phase-steels/>.

"Dual Phase (DP) Steels." WorldAutoSteel. Web. 15 Feb. 2016. <http://www.worldautosteel.org/steel-basics/steel-types/dual-phase-dp-steels/>.

"Automotive-Adv High-Strength-Dual-Ten." Automotive-Adv High-Strength-Dual-Ten. Unite States Steel Corporation. Web. 14 Feb. 2016.