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High strength IF steels

Description

These steels were designed to provide an excellent combination of drawability and mechanical strength based on their specific interstitial free (IF) metallurgy. IF180 offers drawability similar to that of ArcelorMittal 04 combined with tensile strength comparable to that of H220, for example.
These steels are hardened by adding manganese, silicon and phosphorous in solid solution to the ferrite. The metallurgy of IF steels optimizes their drawability.

  • Their low YS/UTS ratio and high strain hardening coefficient n ensure excellent deep-drawability and good strain redistribution.
  • Their high strain ratio r ensures good deformation behavior, making them suitable for deep-drawing.

These steels are particularly suitable for complex parts requiring high mechanical strength, such as wheel arches, toe-boards, reinforcements, etc.
These steels have high strain hardening potential during forming, lending deep-drawn parts (trunks, tailgates, doors, linings, wheel arches, etc.) good dent resistance.
The IF180 to IF 260 grades can be used, with certain coatings, to manufacture visible parts such as door panels. The IF 300 grade is designed for more complex structural parts (longitudinal beams, cross members, suspension and chassis components, etc.).

Application

With their high mechanical strength guaranteeing good fatigue and impact resistance, these steels are intended for structural parts (longitudinal beams, cross members, B-pillars, etc.) as well as for skin parts, in which they provide good indentation resistance.
In contrast to that of conventional drawing qualities, the weight reduction potential of these products increases with drawing depth.

Hood in IF220 Extragal®
(thickness: 0.7 mm)

Designation and standard

 EuronormsVDA 239-100
IF 180HC180Y (+ZE) / HX180YD (+Z, +ZF, +ZM)CR180IF (-UNC,-EG,-GI,-GA,-ZM)
IF 220HC220Y (+ZE) / HX220YD (+Z, +ZF, +ZM)CR210IF (-UNC,-EG,-GI,-GA,-ZM)
IF 260HC260Y (+ZE) / HX260YD (+Z, +ZF, +ZM)CR240IF (-UNC,-EG,-GI,-GA,-ZM)
IF 300/ HX300YD (+Z, +ZF, +ZM)
 

Euronorms
Uncoated ( EN 10268: 2006+A1: 2013): Steel grade name
Electrogalvanized (EN 10268 :2006+A1: 2013 + EN 10152 :2017): Steel grade name+ZE
Galvannealed (EN 10346 :2015): Steel grade name+ZF
Extragal®/Ultragal® for visible parts (EN 10346 :2015): Steel grade name+Z
Zagnelis® (EN 10346 :2015): Steel grade name+ZM

VDA 239-100
Uncoated: Steel grade name-UNC
Electrogalvanized: Steel grade name-EG
Galvannealed: Steel grade name-GA
Extragal®/Ultragal® for visible parts: Steel grade name-GI
Zagnelis®: Steel grade name-ZM

 
 Hot rolled     Cold rolled

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 for ISO 20x80 specimen of uncoated sheet in the transverse direction

 PS0,2 (MPa)UTS (MPa)ef (%)
L0 = 80 mm
th < 3 mm
rn
 IF 180180 - 230340 - 400≥ 35≥ 1,7≥ 0,19
 IF 220220 - 260340 - 400≥ 33≥ 1,7≥ 0,19
 IF 260260 - 300380 - 440≥ 30≥ 1,5≥ 0,18
 IF 300300 - 340400 - 460≥ 28≥ 1,5≥ 0,17
 
 Hot rolled     Cold rolled

Chemical composition (%)

 CMnSi
 MaxMaxMax
IF 1800,0101,000,25
IF 2200,0100,700,50
IF 2600,0101,000,50
IF 3000,0101,000,50
 
 Hot rolled     Cold rolled

Available coatings and Worldwide availability

 UncoatedElectrogalvanizedExtragal®Ultragal®GalvannealedZagnelis®
 EURNAMSAMRSACHIEURNAMSAMRSACHIEURNAMSAMRSACHIEURNAMSAMRSACHIEURNAMSAMRSACHIEURNAMSAMRSACHI
IF 180                
IF 220             
IF 260                
IF 300                       

 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 - XX Available in visible part quality

Microstructure of IF 180

Recommendations for use and secondary processing

Forming
IF steels offer excellent drawability for their strength level as a result of their very good fracture elongation, normal strain ratios and strain hardening coefficients.

The diagram opposite shows examples of forming limit curves for the IF family of steels in 1.00 mm thickness.

Forming limit curves calculated for IF 180 and 260 steels
(thickness: 1.0 mm)

ArcelorMittal has an extensive database on the forming of IF steels. To integrate these steels at the design stage, a team of experts is available to carry out specific studies based on modeling or shop-floor experience.

Welding

IF steels can be readily welded by all welding processes.
The table below shows examples of spot welding parameters according to the ISO 18278-2 method for products in the IF range:

 Welding range (kA)
IF 180 Galvannealed (thickness: 2 mm)1,8
IF 260 Extragal® (thickness: 1 mm)1,4
 
 Hot rolled     Cold rolled

Based on long experience in the spot and arc welding characterization of its products, ArcelorMittal can provide technical assistance in adjusting the welding parameters of any other product in the IF range.

Fatigue strength

Fatigue strength can be expressed as an endurance limit (maximum stress).

Examples of Wöhler curves for a variety of IF steels are given in the graph below. The curves plot maximum stress versus number of cycles to failure. They are calculated for a tension-compression loading ratio of R = 0.1.

Wöhler curves for a variety of IF steels

ArcelorMittal has a comprehensive database on the fatigue performance of IF steels.

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