Dual phase (DP) steel: excellent ductility and energy absorption

Dual phase steels are mostly a ferritic matrix with islands of martensite. Automotive DP steels have excellent global ductility because of the mostly continuous soft ferrite phase.  When dual phase steels are deformed, the strain is concentrated in the lower-strength ferrite that surrounds the harder islands of martensite. This results in DP steels’ high initial work-hardening rate (n-value).

Higher strength (e.g., 1000+ MPa TS) dual phase grades are most commonly achieved by increasing the amount of martensite and bainite. At a given high tensile strength, dual phase steels show a low yield ratio (Re/Rm) and a strong work hardening capacity. Dual phase steels are therefore especially suited for forming operations with high stretching portions.

• Low yield-to-tensile strength ratio provides excellent ductility for superior cold forming with high ultimate tensile strengths.
• High strain hardening and bake hardening further increase tensile strength.
• Excellent deep drawing and high stretching properties.
• Very good crash performance: high strain rate sensitivity means the faster a DP profile is crushed, the more energy it absorbs.
• Custom yield strength levels can be engineered for specific applications.
• High resistance to local constriction produces highly uniform elongation.
• Good RSW weldability.
• Uncoated or with corrosion protection using EG, GI, GA and ZA metal coatings.
• Enables up to 20% lighter weight structural components compared to micro-alloyed steel grades.

Cold-rolled dual phase steels deliver lightweight and energy-absorbing performance to automotive structures and crash components. Because of their ductility, DP can be used in parts with complex geometries. Applications include:

• Bumpers
• Cross members
• Engine cradles
• Floor panels
• Front sub-frame package trays
• Longitudinal beams
• Pillars and pillar reinforcements
• Rails: front, rear and roof
• Rear shock reinforcements
• Seats
• Shotguns
• Side members
• Sill (rocker) reinforcements
• Tunnels and reinforcements

Looking for even greater ductility for even more complex geometries? See our dual phase with high formability/ductility (DH) grades.

For Dual Phase (DP) steels there is a big difference in yield and tensile strength in un-deformed areas. The work hardening in forming is very strong. DP steels have good formability compared to its strength but are limited in hole expansion. With its lean composition these steels are easy to weld but sensitive to heat treatment (>200°C).

• Docol DP steel has excellent stampability, drawability and global formability.
• DP’s tensile strength can be further increased in the final part through strain hardening and bake hardening.
• With less alloys than hot-rolled (HR) DP, Docol cold-rolled dual phase (CR DP) is more readily weldable, including resistance spot welding.

Do you have forming questions about DP grades? Our Technical Support can provide specific DP steel stamping, drawing, and forming guidance for your automotive component, as well as recommending our dual phase with high formability/ductility as required.

• Four cold-rolled, steel “strength families”: Docol 500DP, Docol 600DP, Docol 800DP and Docol 1000DP.
• 48 standard grades within the four Docol dual phase families, targeting specific YS/TS minimums and standards specifications — with another 11 DP grades available upon request.
• EG, GI, GA and ZA corrosion protection available on many dual phase grades.

Safety engineers: With their low yield-to-tensile strength ratio, dual phase steel are excellent for energy-absorbing crash components.

Lightweighting engineers: Up to 20% lighter than micro-alloyed steels, providing numerous “down-gauging” options for thickness reduction in structural auto parts.

Production engineers: High ductility for excellent global formability, with uniform elongation for deep-drawn parts. Good RSW weldability.

Buyers: Huge range of Docol dual phase steel options to meet your engineers’ specific application needs, plus DH options.

With our Trial Material Stock Center, you can get AHSS samples for most of our commercially available steels – as well as samples for our newest but not yet commercially released grades. Unique to the industry, we ship coils, sheets and custom lengths of any size. In 1 to 2 weeks, your material is ready for dispatch to anywhere in the world.