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Complex Phase steels

Description

The Complex Phase family of steels supplements ArcelorMittal's VHSS (very high strength steel) product range. These steels are cold formed to make lightweight structural elements. A number of automotive parts, such as sills and door reinforcements, have simple shapes and the steel is therefore only slightly deformed. For this reason, ArcelorMittal has added the Complex Phase family of steels to its range. These steels offer high as-delivered yield strength and good bendability and stretch flangeability.

Applications

Given their high energy absorption capacity and fatigue strength, these grades are particularly well suited for automotive safety components requiring good impact strength and for suspension system components.

Seat flange in Complex Phase 600 (thickness: 1.5 mm)

Door bar in Complex Phase 1000 (thickness: 2 mm)

Tunnel stiffener in Complex Phase 800 (thickness: 1.6 mm)

Fender beam in Complex Phase 1000 (roll-formed)

Fender beam in Complex Phase 1000 (roll-formed)

Suspension arm in Complex Phase 800 (thickness: 3.1 mm)

Designation and standard

 EuronormsVDA 239-100
Complex Phase 600HCT600C (+ZE)
Complex Phase 800 Y500
Complex Phase 800 Y600HCT780C (+ZE,+Z)CR570Y780T-CP (-UNC,-EG,-GI)
Complex Phase 1000
Complex Phase 1000 SFHCT980C (+ZE)CR780Y980T-CP (-UNC,-EG)
Complex Phase 1000 Y800HCT980C (+Z)CR780Y980T-CP (-GI)
Complex Phase 750HDT750C (+Z)
Complex Phase 800 SFHDT780C (+Z)HR660Y760T-CP (-UNC,-GI)
Complex Phase 1000HDT950C (+Z)
 

Euronorms
Uncoated (EN 10338 :2015): Steel grade name
Electrogalvanized (EN 10338 :2015 + EN 10152 :2009): Steel grade name+ZE
Galvannealed (EN 10346 :2015): Steel grade name+ZF
Extragal® (EN 10346 :2015): Steel grade name+Z

VDA 239-100
Uncoated: Steel grade name-UNC
Electrogalvanized: Steel grade name-EG
Galvannealed: Steel grade name-GA
Extragal®: Steel grade name-GI

 
 Hot rolled     Cold rolled

SF (Stretch Flanging): grade specially developed for improved stretch flangeability.

While the ArcelorMittal grades conform perfectly well to the indicated EN standards, ArcelorMittal grades generally offer tighter mechanical properties (see table below).

The above indicative table summarizes the European and VDA standards corresponding to the ArcelorMittal product range.

Technical characteristics

Mechanical properties

Guaranteed values for ISO 20x80 specimen of uncoated sheet in the strip center at ambient temperature

ST - Transverse direction (perpendicular to the rolling direction) / SL - Rolling direction

 YS (MPa)UTS (MPa)ef (%)
L0 = 80 mm
th < 3 mm
Direction
 Complex Phase 600*360 - 440600 - 700≥ 19SL
 Complex Phase 800 Y500500 - 650780 - 900≥ 13SL
 Complex Phase 800 Y600600 - 700780 - 900≥ 10SL
 Complex Phase 1000700 - 850980 - 1200≥ 8SL
 Complex Phase 1000 SF780 - 950980 - 1200≥ 7SL
 Complex Phase 1000 Y800800 - 950980 - 1130≥ 6SL
 Complex Phase 750620 - 750≥ 750≥ 10SL
 Complex Phase 800680 - 830≥ 780≥ 10ST
 Complex Phase 1000*800 - 950≥ 950≥ 10SL
 
 Hot rolled     Cold rolled

SF (Stretch Flanging): grade specially developed for improved stretch flangeability.

* The guarantees for this grade are subject to change.

Microstructure of hot rolled Complex Phase 800

Microstructure of hot rolled Complex Phase 1000

Chemical composition (%)

 CMnSi
 MaxMaxMax
Complex Phase 6000,101,600,40
Complex Phase 800 Y5000,172,200,60
Complex Phase 800 Y6000,172,200,60
Complex Phase 10000,182,400,60
Complex Phase 1000 SF0,182,400,60
Complex Phase 1000 Y8000,202,700,80
Complex Phase 7500,251,400,40
Complex Phase 8000,102,000,25
Complex Phase 10000,141,700,25
 
 Hot rolled     Cold rolled

SF (Stretch Flanging): grade specially developed for improved stretch flangeability.

Available coatings and surface conditions

 UncoatedElectrogalvanizedExtragal®Jetgal®
 EURNAMSAMRSACHIEURNAMSAMRSACHIEURNAMSAMRSACHIEURNAMSAMRSACHI
Complex Phase 600                 
Complex Phase 800 Y500                 
Complex Phase 800 Y600                
Complex Phase 1000 SF                    
Complex Phase 1000 SF / Complex Phase 1000 Y800                
Complex Phase 750 / MP 800                
Complex Phase 800 / M 800 HY                
Complex Phase 1000 / MP 1000                

 Hot rolled     Cold rolled

Available in non-visible part quality Undergoing customer testing Under development Available in visible and non-visible part quality (Z)

EUR : Europe Region - NAM : North America Region - SAM : South America Region - RSA : South Africa Region - CHI : China

X  Product available / O Product under development

SF (Stretch Flanging): grade specially developed for improved stretch flangeability.

Please consult us about products under development.

Recommendations for use and secondary processing

Forming

Although their ultimate elongation is lower than that of DP and TRIP steels, Complex Phase steels have good formability for their high strength level.

Forming limit curves can be used to define maximum strains without necking for different deformation paths.

Forming limit curves for Complex Phase steels:

Cold rolled in 1.5 mm thickness

Hot rolled in 3 mm thickness

In addition, Complex Phase steels exhibit good roll-forming, bending and hole expansion behavior.
The graph below illustrates hole expansion behavior according to the ISO 16630 standard for a number of Dual Phase and Complex Phase steels with UTS=1000 MPa. The Complex Phase family - and especially the Complex Phase Stretch Flangeable (SF) product, which was specially designed for exceptional stretch flangeability - has higher hole expansion values.

View of hole expansion in grades CR-CP 1000 and CR-CP 1000 SF in 1.5 mm thickness.

The CP 1000 SP achieves a much higher hole expansion value.

The table below shows typical minimum bending radius values for Complex Phase steels in 1.5 mm thickness.

 Rolling directionTransverse direction
Complex Phase 60000
Complex Phase 800 Y50000,5
Complex Phase 800 Y6000,50,5
Complex Phase 10000,51
Complex Phase 1000 SF0,51
 
 Hot rolled     Cold rolled

Rolling direction

Transverse direction

Bending method: 90° flanging

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

Welding

Resistance spot welding

The Complex Phase range of steels has very good resistance spot weldability. The welding range, determined according to the ISO 18278-2 standard, is quite wide. The table below shows examples (indicative) of spot welding characteristics for Complex Phase matching joints, determined according to the ISO 18278-2 standards.

 CoatingThickness (mm)Nugget diameter (mm)Pure tensile (kN)Weld diameter (mm)Tensile-shear (kN)
Complex Phase 600-1.58.415.1921.2
Complex Phase 800-1.58.713.27.624.2
Complex Phase 1000-1.67.29.96.928.1
Complex Phase 800-311.341.49.648.2
Complex Phase 1000Extragal®39.831.19.451.1
 
 Hot rolled     Cold rolled

Laser welding

Laser welding tests have revealed no particular difficulties.

ArcelorMittal can provide technical assistance in adjusting the welding parameters for all steels in the Complex Phase range.

Fatigue

Complex Phase steels exhibit good fatigue properties and can be used in suspension system parts such as suspension arms. The table below gives examples of Wöhler curves for a variety of Complex Phase steels. They are expressed as stress amplitude versus cycles to failure and are obtained with a stress ratio of R = 0.1 and repeated tensile loading.

Wöhler or SN curves for Complex Phase steels (R=0.1)

The graph below shows the low cycle or EN curves for the same steels. These are expressed as strain amplitude versus number of reversals (one cycle equals two reversals). Other high and low cycle fatigue data are available on request.

Low cycle or EN curves for Complex Phase steels (R=-1)

ArcelorMittal can provide a full database on the fatigue performance of Complex Phase steels.

Impact strength

As a result of their very high YS and UTS values, Complex Phase steels are particularly well suited for anti-intrusion parts.

Complex Phase steels have been characterized in the 3-point bending flex test using top hat cross-section specimens impacted at 30 kph. The tests showed very good behavior of these steels.

Mass savings potential compared to an HSLA 380 steel (reference)

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