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

Dual phase automotive steels have an excellent balance of ductility, high tensile strengths, easy cold formability, and very good crash energy-absorption. Its high early-stage strain hardening (n-value) makes DP steel resistant to local necking due to strain redistribution — providing highly uniform elongation. Dual phase steel’s low yield-to-tensile-strength ratio creates high global formability for deep-drawing and high-stretching capacities — all with good weldability.

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    What is the definition of dual phase steels?

    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.

    DP steel properties

    • 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.

    Automotive applications for dual phase steels

    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.

    Additional application ideas
    Dual phase steel for automotive applications

    Grades and mechanical properties for Docol dual phase steel

    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).

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      Product Family Product name Coating Dimensions Standards Datasheet
      Docol 500DP Docol CR​290Y​490T-​DP UC, GI, GA*, ZA T: 0.50 - 3.00 mm
      W: Up to 1527 mm      T: 0.020 - 0.118 in
      W: Up to 60.12 in             		VDA 239-100

      Docol 500DP
      Docol CR​230Y​500T-​DL UC T: 0.50 - 2.10 mm
      W: Up to 1527 mm      T: 0.020 - 0.0827 in
      W: Up to 60.12 in             		SSAB

      Docol 500DP
      Docol CR​290Y​500T-​DP UC T: 0.50 - 2.10 mm
      W: Up to 1527 mm      T: 0.020 - 0.0827 in
      W: Up to 60.12 in             		SSAB

      Docol 500DP
      Docol 600DP Docol CR​330Y​590T-​DP UC, GI, GA, ZA T: 0.50 - 3.00 mm
      W: Up to 1527 mm      T: 0.020 - 0.118 in
      W: Up to 60.12 in             		VDA 239-100

      Docol 600DP
      Docol CR​280Y​600T-​DL UC T: 0.50 - 2.10 mm
      W: Up to 1527 mm      T: 0.020 - 0.0827 in
      W: Up to 60.12 in             		SSAB

      Docol 600DP
      Docol CR​350Y​600T-​DP UC T: 0.50 - 2.10 mm
      W: Up to 1527 mm      T: 0.020 - 0.0827 in
      W: Up to 60.12 in             		SSAB

      Docol 600DP
      Docol 800DP Docol CR​440Y​780T-​DP UC, GI, GA, ZA* T: 0.50 - 2.50 mm
      W: Up to 1527 mm      T: 0.020 - 0.0984 in
      W: Up to 60.12 in             		VDA 239-100

      Docol 800DP
      Docol CR​450Y​780T-​DP UC T: 0.80 - 2.00 mm
      W: Up to 1527 mm      T: 0.031 - 0.0787 in
      W: Up to 60.12 in             		SSAB

      Docol 800DP
      Docol CR​390Y​800T-​DL UC T: 0.50 - 2.10 mm
      W: Up to 1527 mm      T: 0.020 - 0.0827 in
      W: Up to 60.12 in             		SSAB

      Docol 800DP
      Docol CR​500Y​800T-​DP UC T: 0.50 - 2.10 mm
      W: Up to 1527 mm      T: 0.020 - 0.0827 in
      W: Up to 60.12 in             		SSAB

      Docol 800DP
      Docol 800DPX GI, GA* T: 0.80 - 2.00 mm
      W: Up to 1527 mm      T: 0.031 - 0.0787 in
      W: Up to 60.12 in             		SSAB

      Docol 800DP
      Docol 1000DP Docol CR​590Y​980T-​DP UC, EG, GI, GA, ZA T: 0.50 - 2.10 mm
      W: Up to 1527 mm      T: 0.020 - 0.0827 in
      W: Up to 60.12 in             		VDA 239-100

      Docol 1000DP
      Docol CR​700Y​980T-​DP UC, EG, GI, GA*, ZA* T: 0.70 - 2.10 mm
      W: Up to 1527 mm      T: 0.028 - 0.0827 in
      W: Up to 60.12 in             		VDA 239-100

      Docol 1000DP
      Docol CR​700Y​980T-​DP-LCE UC, EG, GI, GA*, ZA* T: 0.50 - 2.10 mm
      W: Up to 1511 mm      T: 0.020 - 0.0827 in
      W: Up to 59.49 in             		SSAB

      Docol 1000DP
      Docol CR​700Y​1000T-​DP UC, EG T: 0.50 - 2.00 mm
      W: Up to 1527 mm      T: 0.020 - 0.0787 in
      W: Up to 60.12 in             		SSAB

      Docol 1000DP
      Docol 1000​DPX GI, GA* T: 1.00 - 2.00 mm
      W: Up to 1320 mm      T: 0.0394 - 0.0787 in
      W: Up to 51.97 in             		SSAB

      Docol 1000DP
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        *Available upon request.

        Forming Docol dual phase steels

        • 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.

        Contact tech support
        Forming Docol dual phase steel

        Additional benefits from Docol DP steels

        • 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.

        OEM-specific dual phase steels

        Individual Docol DP steel grades can be tailored to OEM specifications or made to internationally accepted standards, such as VDA 239-100:2016, EN 10338:2015, EN 10346:2015, or SSAB’s own high standards. We encourage you to reach out early in your design process in case your crash or structural component requires specific dual phase steel properties or is a better candidate for our dual phase with high formability/ductility (DH) grades.

        Custom AHSS for automotive OEMs

        The benefits of Docol® DP steel for each team member

        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.

        Future-proof your life cycle assessment

        Lower your embedded CO2

        Docol dual phase is "future-proofed".
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        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.

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        What is dual phase steel?

        The microstructures of dual phase steels are largely a ferritic matrix with martensitic “islands” as the hard second phase. The soft ferrite phase is virtually continuous, so automotive DP steels have excellent global ductility.

        Why use DP steels?

        Dual phase steels are widely used in automotive components due to their strength, high crash performance, and cold formability – particularly for deeply drawn or stretched parts. Their high n-value make DP steels resistant to local necking due to strain redistribution.

         

        Where is dual phase steel used?

        Cold-rolled dual phase steels are widely specified for their lightweight and energy-absorbing performance in automotive structural and crash components, including car parts with complex geometries.

        What is the formability of DP steels?

        • Low YS-to-TS ratios means high ductility, providing excellent stampability, drawability and global formability — but with high tensile strengths.
        • Strain hardening and bake hardening can further increase tensile strength levels in the final part.

        FAQ

        Other steel categories

        • martensitic steel coil

          Martensitic steel: excellent formability-to-strength ratio

          Martensitic steel combines tensile strengths up to 1700 MPa with good ductility, making it highly efficient for both vehicle lightweighting and improved crash protection — especially in anti-intrusion zones.

        • Dual phase with high formability/ductility for crack-free cold deep drawing

          Dual phase with high formability/ductility (DH) steels are TRIP-assisted, 3rd Generation automotive steels with high global and local formability and good resistance to edge cracking. DH steel have excellent energy-absorbing properties, included reserved ductility during crash impact. DH grades are ideal for complex geometries, including cold deep drawing. DH steel's FLDs and HERs are superior to DP steels, enabling scrap reduction and more streamlined stamping.

        • Press hardening steels (PHS) for complex shapes

          Press hardening steels have four major advantages: they can be formed into very complex shapes, their ultimate tensile strength ranges up to 2000 MPa (290 ksi), there is little or no springback, and, with tailored tempering, you can combine “full hard zones” and “soft zones” for multi-function crash performance within a single part.

        • Docol complex phase steel

          Complex phase (CP) steels for the highest hole expansion ratios

          Complex phase steels have the highest — up to 100% — hole expansion ratios available from advanced high strength steels. Their high HER values provide excellent cold-forming properties for punched and stretched edges/flanges, as well as deep-drawn shapes. CP steels’ superior yield strengths are used for high crash-energy absorption, while their elevated UTS levels enable thinner walls for significant automobile weight reductions.

        • Docol High Edge ductility

          High edge (HE) ductility HSLA steel

          High edge ductility HSLA steel with greatly improved local formability and high hole expansion ratios – ideal for challenging auto components with complex designs on sheared stretched edges.

        • High strength, low alloy (HSLA) steels for cost-effective automotive lightweighting

          High strength, low alloy steels are a cost-effective choice for increasing strength-to-weight ratios when compared to conventional mild carbon steels. HSLA steels also have excellent bendability and weldability and can increase the strength and/or decrease the weight for a variety of body-in-white and chassis automotive components, including suspensions, beams, and subframes.

        • Ferritic-Bainitic steel: stretch edge flangeability for cold-forming

          Ferritic-Bainitic are multi-phased steels with high hole expansion ratios and good edge stretch capabilities. FB steels are suited for cold-formed and punched flanges when lightweighting automotive components such as wheels, cross members, and other structural parts.