Hot rolled ferrite-bainite steels

Transcription

1 Automotive Worldwide ferrite-bainite steels Extract from the product catalogue -European edition Note: Information contained in this catalogue is subject to change. Please contact our sales team whenever you place an order to ensure that your requirements are fully met. Please contact us if you have a specific requirement that is not included in the range of products and services covered by this catalogue. We are also reachable by the address automotive.request@arcelormittal.com.

2 We are also reachable by the address ferrite-bainite steels Advanced high strength steels Description This range of hot-rolled high strength steels has been developed to meet weight reduction requirements. It comprises four strength levels: FB 450, 540, 560 and 590. This family of steels extends the HSLA range of micro-alloyed steels to include products combining high tensile strength (UTS) with excellent formability and hole expansion (stretch flangeability) based on their ferrite-bainite microstructure. Applications These steels are cold-drawn. The main applications are: structural parts (longitudinal beams, cross beams, car-body and ground liason parts), wheels, mechanical parts (ground liason parts, gear boxes...). ArcelorMittal has an extensive database relating to the forming and service properties of the entire range of ferrite-bainite steels. To integrate these steels at the design stage, a team of experts is available to perform specific studies based on modeling or laboratory tests. Front and rear underseat cross member in galvanised FB 560 (thickness: 1.8 mm) Suspension arm in uncoated (thickness: 4 mm) 2

3 Suspension arm in Extragal (thickness: 4 mm) Pillar reinforcement in galvanised (thickness: 1.8 mm) Wheel in 3

4 Designation and standards Euronorms VDA HDT450F (+Z) HR300Y450T-FB (-UNC,-GI) HDT580F(+Z) HR440Y580T-FB (-UNC,-GI) HDT580F HR440Y580T-FB (-UNC) HHE* Euronorms Uncoated (EN :2015): Steel grade name Electrogalvanized (EN : EN :2017): Steel grade name +ZE Galvannealed (EN :2015): Steel grade name +ZF Extragal (EN :2015): Steel grade name +Z VDA Uncoated: Steel grade name-unc Electrogalvanized: Steel grade name-eg Galvannealed: Steel grade name-ga Extragal : Steel grade name-gi HHE: High Hole Expansion. The above indicative table summarizes the European and VDA standards corresponding to the ArcelorMittal product range. While the ArcelorMittal grades conform perfectly well to the indicated EN standards, ArcelorMittal grades generally offer tighter mechanical properties (see table below). Technical characteristics Mechanical properties Guaranteed for ISO 20X80 (thickness < 3 mm) or proportional (thickness 3 mm) test specimen of uncoated sheet. ST -Transverse direction (perpendicular to the rolling direction) / SL -Rolling direction Ef (%) L0 = 5,65 S0 (mm) th 3 mm Direction YS (MPa) UTS (MPa) ef (%) L0 = 80 mm th < 3 mm SL SL SL ST HHE* ST * HHE: we recommend this option for parts requiring very high hole expansion (HHE: High Hole Expansion grade). For this grade, the minimum guaranteed JIS elongation is 18%. Chemical composition (%) 4

5 Chemical composition (%) C Max Mn Max Si Max 0,17 0,8 0,05 0,17 1,5 0,15 0,1 1,6 0,15 0,1 1,6 0,15 HHE 0,05 2,0 0,8 Ferrite-bainite microstructure of Available coatings and Worldwide availability Uncoated EUR NAM SAM Extragal RSA CHI EUR NAM SAM RSA CHI HHE Available in non-visible part quality quality (Z) Undergoing customer testing Under development Available in visible and non-visible part EUR : Europe Region -NAM : North America Region -SAM : South America Region -RSA : South Africa Region -CHI : China X available product Recommendations for use and for secondary processing High hole expansion grade 5

6 High hole expansion grade ArcelorMittal offers an FB590 HHE (High Hole Expansion) grade, which is recommended for parts with sheared edge stretchability requirements (stretch flangeability, edge flanging, edge stress during secondary processing, etc.). The images opposite shows an example of hole expansion behaviour according to the ISO standard for grades and HHE. View of hole expansion in grades and HHE in 4 mm thickness. The HHE achieves a much higher hole expansion value. Forming The graph below gives critical forming limits calculated for the FB family of steels in 2.5 mm thickness. Forming limit curves for the FB family of steels Please consult us for further information relating to the forming of steels in the FB range with specific thicknesses and coatings. Welding Examples of data relating to resistance spot welding of coated and uncoated steels of different thicknesses in the FB product range, determined according to the ISO method. These steels can be arc welded. Coating Thickness (mm) Welding range (ka) Extragal uncoated The following indicative welding parameters are used in MAG welding: Filler metal: GS2-type wire Protective gas: ATAL 5 or ATAL 18 Welding speed: 80 cm/min ArcelorMittal can provide technical assistance in adjusting the welding parameters of any other steel in the FB range product. Fatigue strength As a result of their high tensile strength and their microstructure, FB steels have good fatigue strength. 6

7 As a result of their high tensile strength and their microstructure, FB steels have good fatigue strength. Examples of Wöhler curves for a variety of FB steels are given in the graph below. The curves plot maximum stress versus number of cycles to failure. They are calculated for a tension-tension loading ratio of R = 0.1. Wöhler curves of the FB range of steels ArcelorMittal can provide a full database on the fatigue performance of FB steels. ArcelorMittal Last update: