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Dual phase steels

Description

Dual Phase steels offer a good combination of strength and stampability as a result of their microstructure, in which a hard martensitic or bainitic phase is dispersed in a ductile ferritic matrix. These steels have high strain hardenability. This gives them not only good strain redistribution capability and thus stampability, but also finished part mechanical properties, including yield strength, that are far superior to those of the flat metal. The yield strength of Dual Phase steels is further increased by the paint baking (also called Bake Hardening, BH) process.

This high level of mechanical strength obtained in parts lends these steels excellent fatigue strength and good energy-absorption capacity, making them suitable for use in structural parts and reinforcements. Their strong strain hardening combined with a pronounced bake hardening effect gives them excellent potential for reducing the weight of structural parts and even skin parts, especially in the case of CR290Y490T-GI-E Extragal® or Ultragal®.

Applications

Given their high energy absorption capacity and fatigue strength, cold-rolled Dual Phase Steels are particularly well suited for the manufacture of automotive structural and safety parts such as longitudinal beams, crossmembers and reinforcements.

CR290Y490T-GI-E Extragal® or Ultragal® steel can be used to make visible parts with 20% higher dent resistance than conventional high strength steels, resulting in a potential weight saving of some 15%.

 

As a result of its mechanical strength, hot-rolled Dual Phase 600 can be used to reduce the weight of structural parts by decreasing their thickness. Relevant automotive applications include:

  • Wheel webs
  • Lightweight sections
  • Strut mounts
  • Fasteners
  • B-pillar reinforcement in CR590Y980T-DP-GI Extragal®

  • Bumper in CR900Y1180T-DP (thickness: 1.35 mm)

  • Wheel web in HR330Y580T-DP Patented VersaStyle® wheel from Hayes Lemmerz International

ArcelorMittal has an extensive database on the forming and service properties of the entire range of Dual Phase steels. To incorporate these steels at the design stage, a team of experts is available to carry out specific studies based on either modelling or characterisation testing. 

Designation and standard

Show all
ArcelorMittal name Generic name Euronorms VDA 239-100
CR260Y450T-DP DP450 HCT450X (+ZE,+Z,+ZF)
CR290Y490T-DP DP500 / FF280DP HCT490X (+ZE,+Z) CR290Y490T-DP (-UNC,-EG,-GI)
CR330Y590T-DP DP600 HCT590X (+ZE,+Z,+ZF, +ZM) CR330Y590T-DP (-UNC,-EG,-GI,-GA,-ZM)
CR420Y590T-DP DP600Y420
CR440Y780T-DP DP780Y450 HCT780X (+ZE,+Z,+ZF) CR440Y780T-DP (-UNC,-EG,-GI,-GA)
CR440Y780T-DP-LCE DP780Y450 LCE HCT780X (+ZE,+Z,+ZF) CR440Y780T-DP (-UNC,-EG,-GI,-GA)
CR500Y780T-DP DP780Y500
CR500Y780T-DP-LCE DP780Y500 LCE
CR550Y690T-DP CR80Y100T
CR550Y980T-DP DF140T
CR590Y980T-DP-LCE DP980Y600 LCE HCT980X (+ZE,+Z,+ZF) CR590Y980T-DP(-UNC,-EG,-GI,-GA)
CR700Y980T-DP DP980Y700 HCT980XG (+ZE,+Z) CR700Y980T-DP (-UNC,-EG,-GI)
CR700Y980T-DP-LCE DP980Y700 LCE HCT980XG (+ZE,+Z) CR700Y980T-DP (-UNC,-EG,-GI)
CR800Y1180T-DP DP1180Y800
CR900Y1180T-DP DP1180Y900 HCT1180G2 (+ZE) CR900Y1180T-CP (-UNC,-EG)
Show all
ArcelorMittal name Generic name Euronorms VDA 239-100
HR330Y580T-DP HR DP600 HDT580X HR330Y580T-DP (-UNC)
HR450Y750T-DP HR DP780
  • Euronorms

    Uncoated (EN 10338: 2015): Steel grade name
    Electrogalvanized (EN 10338: 2015 + EN 10152 :2017): Steel grade name+ZE
    Galvannealed (EN 10346: 2015): Steel grade name+ZF
    Extragal® (EN 10346: 2015): Steel grade name+Z
    Zagnelis® (EN 10346: 2015): Steel grade name+ZM

  • VDA 239-100

    Uncoated: Steel grade name-UNC
    Electrogalvanised: Steel grade name-EG
    Galvannealed: Steel grade name-GA
    Extragal®: Steel grade name-GI
    Zagnelis®: Steel grade name-ZM

LCE: Low Carbon Equivalent grade used to optimise properties in service.

The above table, for information only, summarises the cross-references between the ArcelorMittal product range, European standards and VDA standard 239-100.

These cross-references are given for information only. ArcelorMittal steel grades generally offer tighter mechanical properties (see table below).

Mechanical properties

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ArcelorMittal name Generic name Direction Yield stress Rp0.2 (MPa) Tensile strength Rm (MPa) Min. A(%) Type 1 Min. A50mm (%) Type 2 Min. A80mm (%) Type 3 Min. A50mm (%) Min. BH2 MPa n4-6 n10-20/Ag
CR260Y450T-DP DP450 RD 260 - 340 450 - 530 27 27 29 30 0.16
CR290Y490T-DP DP500 / FF280DP RD 290 - 380 490 - 600 26 24 26 30 0.19 0.15
CR330Y590T-DP DP600 RD 330 - 440 590 - 700 21 20 22 30 0.18 0.14
CR420Y590T-DP DP600Y420 RD 420 - 500 590 - 680 17 17 18 30 0.18
CR440Y780T-DP DP780Y450 RD 440 - 550 780 - 900 15 14 15 30 0.15 0.11
CR440Y780T-DP-LCE DP780Y450 LCE RD 440 - 550 780 - 900 14 14 15 30 0.15 0.11
CR500Y780T-DP DP780Y500 RD 500 - 600 780 - 900 13 13 14 30 0.1
CR500Y780T-DP-LCE DP780Y500 LCE RD 500 - 600 780 - 900 13 13 14 30 0.1
CR550Y690T-DP CR80Y100T RD 550 - 660 ≥ 690 13 12 15 30 0.08 0.06
CR550Y980T-DP DF140T RD 550 - 700 ≥ 980 8 10 10 30 0.08 0.06
CR590Y980T-DP-LCE DP980Y600 LCE RD 590 - 740 980 - 1130 11 10 11 30
CR700Y980T-DP DP980Y700 RD 700 - 850 980 - 1130 9 8 9 30
CR700Y980T-DP-LCE DP980Y700 LCE RD 700 - 850 980 - 1130 8 8 9 30
CR800Y1180T-DP DP1180Y800 RD 800 - 970 1180 - 1300 6 5 6 30
CR900Y1180T-DP DP1180Y900 RD 900 - 1100 1180 - 1350 6 5 6 30
Show all
ArcelorMittal name Generic name Direction Yield stress Rp0.2 (MPa) Tensile strength Rm (MPa) Min. A(%) Type 1 Min. A50mm (%) Type 2 Min. A80mm (%) Type 3 Min. A50mm (%) Min. BH2 MPa n4-6 n10-20/Ag
HR330Y580T-DP HR DP600 RD 330 - 450 580 - 680 23 21 19 20 30 0.16 0.13
HR450Y750T-DP HR DP780 RD ≥ 450 ≥ 750 18 15 15 16 30

A80mm %: Percentage elongation after fracture using a specimen with gauge length L0 = 80 mm (ISO 6892-1 type 2 (EN20x80))
A50mm %: Percentage elongation after fracture using a specimen with gauge length L0 = 50 mm (ISO 6892-1 type 1 (ASTM12.5x50) or type 3 (JIS25x50)
A%: Percentage elongation after fracture using a proportional specimen with L0 = 5.65 (So)1/2
Ag %: Percentage plastic extension at maximum force
BH2: Increase in yield strength between a reference condition after a 2% plastic pre-strain and the condition obtained after heat treatment (170°C-20minutes)

Chemical composition

Show all
ArcelorMittal name Generic name Max. C (%) Max. Si (%) Max. Mn (%) Max. P (%) Max. S (%) Al (%) Max. Cu (%) Max. B (%) Max. Ti + Nb (%) Max. Cr + Mo (%)
CR260Y450T-DP DP450 0.14 0.5 1.8 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1
CR290Y490T-DP DP500 / FF280DP 0.14 0.5 1.8 0.05 0.01 0.015 - 1 0.2 0.005 0.15 1
CR330Y590T-DP DP600 0.15 0.8 2.5 0.05 0.01 0.010 - 1.5 0.2 0.005 0.15 1.4
CR420Y590T-DP DP600Y420 0.15 0.8 2.5 0.05 0.01 0.010 - 1.5 0.2 0.005 0.15 1.4
CR440Y780T-DP DP780Y450 0.18 0.8 2.5 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4
CR440Y780T-DP-LCE DP780Y450 LCE 0.10 0.8 2.5 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4
CR500Y780T-DP DP780Y500 0.18 0.8 2.5 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4
CR500Y780T-DP-LCE DP780Y500 LCE 0.1 0.8 2.5 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4
CR550Y690T-DP CR80Y100T 0.17 0.4 1.7 0.02 0.01 ≥ 0.010 0.2 0.005 0.15 1.0
CR550Y980T-DP DF140T 0.17 0.4 1.7 0.02 0.01 ≥ 0.010 0.2 0.005 0.15 1.0
CR590Y980T-DP-LCE DP980Y600 LCE 0.11 1.0 2.9 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4
CR700Y980T-DP DP980Y700 0.23 1.0 2.9 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4
CR700Y980T-DP-LCE DP980Y700 LCE 0.11 1.0 2.9 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4
CR800Y1180T-DP DP1180Y800 0.23 1.0 2.9 0.05 0.01 0.015 - 1.0 0.2 0.005 0.15 1.0
CR900Y1180T-DP DP1180Y900 0.23 1.0 2.9 0.05 0.01 0.15 - 1.0 0.2 0.005 0.15 1.0
Show all
ArcelorMittal name Generic name Max. C (%) Max. Si (%) Max. Mn (%) Max. P (%) Max. S (%) Al (%) Max. Cu (%) Max. B (%) Max. Ti + Nb (%) Max. Cr + Mo (%)
HR330Y580T-DP HR DP600 0.14 1.0 2.2 0.06 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4
HR450Y750T-DP HR DP780 0.14 1.0 2.2 0.06 0.01 0.015 - 1.0 0.2 0.005 0.15 1.4

LCE: Low Carbon Equivalent grade, used to optimise properties in service.

  • CR330Y590T-DP

  • CR700Y980T-DP 

The service properties of Dual Phase steels are guaranteed by manufacturing process control. The controlled (temperature, cooling rate) annealing cycle in particular ensures that the Dual Phase microstructure is achieved and mechanical properties are reproducible.

Global availability


Under development     Customer trials     Commercial unexposed only     Commercial exposed and unexposed    

Show all
ArcelorMittal name Generic name Uncoated (-UNC) Alusi® (-AS) Extragal® (-GI) Ultragal® (-GI) Galvannealed (-GA) Zagnelis®Protect (-ZMP) Zagnelis®Surface (-ZMS) Electrogalvanized (-EG) Jetgal® (-ZV)
CR260Y450T-DP DP450
CR290Y490T-DP DP500 / FF280DP
CR330Y590T-DP DP600
CR420Y590T-DP DP600Y420
CR440Y780T-DP DP780Y450
CR440Y780T-DP-LCE DP780Y450 LCE
CR500Y780T-DP DP780Y500
CR500Y780T-DP-LCE DP780Y500 LCE
CR550Y690T-DP CR80Y100T
CR550Y980T-DP DF140T
CR590Y980T-DP-LCE DP980Y600 LCE
CR700Y980T-DP DP980Y700
CR700Y980T-DP-LCE DP980Y700 LCE
CR800Y1180T-DP DP1180Y800
CR900Y1180T-DP DP1180Y900
HR330Y580T-DP HR DP600
HR450Y750T-DP HR DP780
Show all
ArcelorMittal name Generic name Uncoated (-UNC) Extragal® (-GI) Ultragal® (-GI) Galvannealed (-GA) Zagnelis®Protect (-ZMP) Zagnelis®Surface (-ZMS) Galfan (-ZA) Electrogalvanized (-EG) Jetgal® (-ZV)
CR260Y450T-DP DP450
CR290Y490T-DP DP500 / FF280DP
CR330Y590T-DP DP600
CR420Y590T-DP DP600Y420
CR440Y780T-DP DP780Y450
CR440Y780T-DP-LCE DP780Y450 LCE
CR500Y780T-DP DP780Y500
CR500Y780T-DP-LCE DP780Y500 LCE
CR550Y690T-DP CR80Y100T
CR550Y980T-DP DF140T
CR590Y980T-DP-LCE DP980Y600 LCE
CR700Y980T-DP DP980Y700
CR700Y980T-DP-LCE DP980Y700 LCE
CR800Y1180T-DP DP1180Y800
CR900Y1180T-DP DP1180Y900
HR330Y580T-DP HR DP600
HR450Y750T-DP HR DP780
Show all
ArcelorMittal name Generic name Uncoated (-UNC) Extragal® (-GI) Galvannealed (-GA) Zagnelis® (-ZM) Electrogalvanized (-EG) Surface treatments
CR260Y450T-DP DP450
CR290Y490T-DP DP500 / FF280DP
CR330Y590T-DP DP600
CR420Y590T-DP DP600Y420
CR440Y780T-DP DP780Y450
CR440Y780T-DP-LCE DP780Y450 LCE
CR500Y780T-DP DP780Y500
CR500Y780T-DP-LCE DP780Y500 LCE
CR550Y690T-DP CR80Y100T
CR550Y980T-DP DF140T
CR590Y980T-DP-LCE DP980Y600 LCE
CR700Y980T-DP DP980Y700
CR700Y980T-DP-LCE DP980Y700 LCE
CR800Y1180T-DP DP1180Y800
CR900Y1180T-DP DP1180Y900
HR330Y580T-DP HR DP600
HR450Y750T-DP HR DP780
Show all
ArcelorMittal name Generic name Alusi® (-AS) Extragal® (-GI) Galvannealed (-GA)
CR260Y450T-DP DP450
CR290Y490T-DP DP500 / FF280DP
CR330Y590T-DP DP600
CR420Y590T-DP DP600Y420
CR440Y780T-DP DP780Y450
CR440Y780T-DP-LCE DP780Y450 LCE
CR500Y780T-DP DP780Y500
CR500Y780T-DP-LCE DP780Y500 LCE
CR550Y690T-DP CR80Y100T
CR550Y980T-DP DF140T
CR590Y980T-DP-LCE DP980Y600 LCE
CR700Y980T-DP DP980Y700
CR700Y980T-DP-LCE DP980Y700 LCE
CR800Y1180T-DP DP1180Y800
CR900Y1180T-DP DP1180Y900
HR330Y580T-DP HR DP600
HR450Y750T-DP HR DP780
Show all
ArcelorMittal name Generic name
CR260Y450T-DP DP450
CR290Y490T-DP DP500 / FF280DP
CR330Y590T-DP DP600
CR420Y590T-DP DP600Y420
CR440Y780T-DP DP780Y450
CR440Y780T-DP-LCE DP780Y450 LCE
CR500Y780T-DP DP780Y500
CR500Y780T-DP-LCE DP780Y500 LCE
CR550Y690T-DP CR80Y100T
CR550Y980T-DP DF140T
CR590Y980T-DP-LCE DP980Y600 LCE
CR700Y980T-DP DP980Y700
CR700Y980T-DP-LCE DP980Y700 LCE
CR800Y1180T-DP DP1180Y800
CR900Y1180T-DP DP1180Y900
HR330Y580T-DP HR DP600
HR450Y750T-DP HR DP780
Show all
ArcelorMittal name Generic name Uncoated (-UNC) Extragal® (-GI) Galvannealed (-GA)
CR260Y450T-DP DP450
CR290Y490T-DP DP500 / FF280DP
CR330Y590T-DP DP600
CR420Y590T-DP DP600Y420
CR440Y780T-DP DP780Y450
CR440Y780T-DP-LCE DP780Y450 LCE
CR500Y780T-DP DP780Y500
CR500Y780T-DP-LCE DP780Y500 LCE
CR550Y690T-DP CR80Y100T
CR550Y980T-DP DF140T
CR590Y980T-DP-LCE DP980Y600 LCE
CR700Y980T-DP DP980Y700
CR700Y980T-DP-LCE DP980Y700 LCE
CR800Y1180T-DP DP1180Y800
CR900Y1180T-DP DP1180Y900
HR330Y580T-DP HR DP600
HR450Y750T-DP HR DP780

Please enquire about the availability of products shown as being under development or left blank in the table.

LCE: Low Carbon Equivalent grade, used to optimise properties in service.

Forming

Dual Phase steels offer a good combination of strength and stampability as a result of their good ductility and strain hardening capacity from the onset of deformation, which ensure uniform strain distribution and reduced local thinning. For example, in the case of a Dual Phase 500 steel, the yield strength increases by about 120 MPa after 2% of plastic strain in uniaxial tension (a phenomenon known as work hardening or WH2). The yield strength can be further increased through bake hardening (BH2) after paint curing.

CR290Y490T-GI-E Extragal® or Ultragal® steel can also be used to manufacture skin parts, as a result of its excellent behaviour in expansion and in tension broadly.

Dual Phase steels can be drawn on conventional tools, subject to settings being optimised. For example, stamping pressure should be increased by approximately 20% for a CR330Y590T-DP steel, compared to a micro-alloyed (HSLA) type steel of the same thickness. It should be noted that these steels, especially the highest grades, are sensitive to the so-called springback phenomenon. Component geometry must be carefully studied during design (small die radius, reinforcement perpendicular to bends to stiffen open parts, etc.) and drawing sequence definition (overbending, calibration tool, punch stroke, increased blank-clamping force, etc.).

ArcelorMittal has developed expertise in controlling springback by means of part and drawing tool design (OUTIFO method).

Forming limit curves for the Dual Phase family of steels (thickness: 1.0 mm) (ArcelorMittal model for Europe)

Forming limit curves for the Dual Phase family of steels (thickness: 1.0 mm) (Keeler model for North America)

For more information about the forming of Dual Phase steels in special thicknesses and with special coatings, please contact us.

Welding

Although Dual Phase steels are more highly alloyed than HSLA steels, they can be readily welded using conventional resistance spot welding processes, provided the parameters used in industrial conditions are adjusted. The table below gives  examples, for information only, of some spot weld properties for Dual Phase steel similar joints complying with the ISO 18278-2 standard.

Show all
ArcelorMittal name Coating Thickness (mm) Nugget diameter (mm) Pure tensile (kN) Weld diameter (mm) Tensile-shear (kN)
CR290Y490T-DP Uncoated 1.5 8 14.2 8.8 18.4
CR330Y590T-DP Extragal® 1.5 7.7 13.1 9.5 22.3
CR440Y780T-DP Extragal® 1.5 8.9 10.5 9.4 25.6
CR440Y780T-DP-LCE Uncoated 1.5 7.6 14.3 6.6 22.7
CR590Y980T-DP-LCE Extragal® 1.5 8.4 13.2 10.1 30.4
Show all
ArcelorMittal name Coating Thickness (mm) Nugget diameter (mm) Pure tensile (kN) Weld diameter (mm) Tensile-shear (kN)
HR330Y580T-DP Uncoated 3 11.6 32.6 11.2 46.7

For coated (galvanised and alloy galvanised) products, electrode service life tests show values characteristic of the type of coating considered. The Dual Phase substrate does not affect the service lifespans obtained.

 

In butt or lap MAG (Metal Active Gas) arc welding, maximum hardness in the fusion zone does not exceed 300 HV for a HR330Y580T-DP steel, whatever the parameters. The weld runs meet ISO 25817 Class B requirements. Recommended welding consumables are:

  • Filler: G3Si1 NF EN 440;
  • Protective gas: Ar + 8% CO2.

 

Dual Phase steels have excellent mechanical strength in laser lap welding. Based on long shop-floor experience in characterising its products, ArcelorMittal can provide technical assistance in adjusting the welding parameters for Dual Phase steels.

 

 

Fatigue strength

As a result of their high mechanical strength, Dual Phase steels exhibit good fatigue properties. Examples of Wöhler curves for a variety of Dual Phase steels are shown in the two graphs below. The curves plot maximum stress versus number of cycles to failure. They are calculated for two loading ratios: tension-compression R=-1 and tension-tension R=0.1.

 

Wöhler curves or S-N curves for a variety of Dual Phase steels

The graph below shows the oligocyclic fatigue or E-N curves for the same steels. The curves plot strain amplitude versus number of reversals to failure (one cycle corresponds to two reversals). Other high and low cycle fatigue data can be provided on request.

ArcelorMittal can make a Dual Phase steel fatigue performance database available to its customers.

Impact resistance

As a result of their very high tensile strength, Dual Phase steels are particularly suitable for parts designed to absorb energy during an impact.

 

Dual Phase steels have been characterised in dynamic axial compression tests using a top-hat structure with a spot-welded closure plate at an impact velocity of 56 km/h. These tests have demonstrated the good impact behaviour of these steels. The following graph gives, for information only, the minimum potential weight saving for some Dual Phase steels compared with an HSLA 380 steel.

Potential weight saving compared to a CR380LA steel (reference)

Potential weight saving compared to a CR380LA steel (reference)

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