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MartINsite® steels

Description

The family of MartINsite® steels extends ArcelorMittal's range of Ultra High Strength Steels (UHSS). These steels allow the realization of lightweight structural elements by a forming method such as roll forming. To achieve maximum weight reduction while maintaining a very good anti-intrusion during the crash properties, some parts require the use of UHSS, such as the sills and door reinforcements, have simple shapes, and therefore the steel is slightly deformed. For this reason, ArcelorMittal has complemented its offer with the family of MartINsite® steels with very high yield strength delivery and interesting properties of bending deformation and a very good formability of the cut edges.

Application

Thanks to their excellent mechanical properties, these grades are particularly suitable for automotive safety parts for shock resistance. Typical parts are shown in the figure below:

  • Front and rear bumper beams
  • Door beam
  • Side Sill Reinforcement
  • Roof cross member

Typical parts for MartINsite® steels

Designation and standard

  Euronorms VDA 239-100
MartINsite® 1200
MartINsite® 1500 CR1220Y1500T-MS(-UNC,-EG)
 

Euronorms


VDA 239-100

 
 Hot rolled     Cold rolled

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

Technical characteristics

Mechanical properties
Guaranteed for 20x80 mm ISO specimen of uncoated sheet
TD - Tranverse direction (perpendicular to the rolling direction) / RD - Rolling direction

  YS (MPa) UTS (MPa) ef (%)
L0 = 80 mm
th < 3 mm
Direction
 MartINsite® 1200 ≥ 950 1200 - 1400 ≥ 3 SL - ST
 MartINsite® 1500 1200 - 1500 1500 - 1700 ≥ 3 SL - ST
 
 Hot rolled     Cold rolled

MartINsite® 1200 microstucture

MartINsite® 1500 microstucture

Chemical composition (%)

  C Mn Si
  Max Max Max
MartINsite® 1200 0,13 2,40 0,30
MartINsite® 1500 0,25 2,00 0,50
 
 Hot rolled     Cold rolled

Available coatings and Worldwide availability

  Uncoated Electrogalvanized Jetgal®
  EUR NAM SAM RSA CHI EUR NAM SAM RSA CHI EUR NAM SAM RSA CHI
MartINsite® 1200                        
MartINsite® 1500                    

 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  available  / O  under development
MartINsite® steels with Electrogalvanized coating have been optimized to provide excellent crash performance and protection against corrosion, ensuring a good resistance to hydrogen embrittlement.

Recommendations for use and secondary processing

Forming
MartINsite® steels exhibit a good behavior in roll forming, in bending and in hole expansion.
The graph below illustrates their behavior in hole expansion according to the ISO 16630 standard.

The table below gives typical values ​​of minimum bend radius for Matensitic steel (thickness 1.5 mm)

  Rolling direction Transverse direction
MartINsite® 1200 1,5 2
MartINsite® 1500 2 3
 
 Hot rolled     Cold rolled

Bending method: 90° flanging

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

Welding

Resistance spot welding
The MartINsite® range of steels has a 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 MartINsite® matching joints, determined according to the ISO 18278-2 standards.

  Coating Thickness (mm) Nugget diameter (mm) Pure tensile (kN) Weld diameter (mm) Tensile-shear (kN)
MartINsite® 1200 - 1.5 7.5 10 7.5 30
MartINsite® 1500 - 1.5 7.5 8 7.5 30
 
 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 MartINsite® range.

Fatigue

MartINsite® steels exhibit good fatigue properties. The table below gives examples of Wöhler curves for a variety of MartINsite® 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 curves or S-N curves for a variety of MartINsite® steels

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.

ArcelorMittal can provide a full database on the fatigue performance of MartINsite® steels.

Impact strength

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

 

MartINsite® steels have been characterized in the 3-point bending test using top hat cross-section specimens impacted at 30 kph. The tests showed very good behavior of these steels. The following graph shows the mass reduction potential of these steels compared to that of an HSLA 380.

Mass reduction potential compared to that of an HSLA 380 steel (reference)

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