Mechanical properties of different phases in steels Phase Phase R e , MPa R e , MPa R m , MPa R m , MPa A, % A, % Hardening, HV Hardening, HV 280 280 50 50 Interstitial free condition Interstitial free condition 100-150 100-150 - - (Ferrite) (Ferrite) 220 220 300 300 45 45 Ferrite (unalloyed) Ferrite (unalloyed) - - 330 330 550 550 35 35 Ferrite (0,7% Ni, 0,6% Cr) Ferrite (0,7% Ni, 0,6% Cr) about 180 about 180 300 300 500 500 18 18 Ferrite (13% Cr) Ferrite (13% Cr) - - 900 900 1000 1000 10 10 Pearlite Pearlite - - 3000 3000 Cementite Cementite - - - - - - Bainite ( 0,1% C) Bainite ( 0,1% C) 25 25 400-800 400-800 550-1200 550-1200 about 320 about 320 Martensite ( 0,1% C) Martensite ( 0,1% C) 800 800 1200 1200 5 5 about 380 about 380 Martensite ( 0,4% C) Martensite ( 0,4% C) 2400 2400 - - - - - - 300 300 600 600 40 40 Austenite (18% Cr, 8% Ni) Austenite (18% Cr, 8% Ni) - - 64
Homogeneity of grain structure - properties 65
Characteristics of AHSS 66
Microstructures of modern multiphase steels Higher strength 67
Microstructures vs mechanical properties of modern multi-phase steels 50 40 F+P 30 DP DP strain in % TRIP TRIP 20 CP CP 10 MS MS 0 200 400 600 800 1200 1400 1600 1000 Tensile strength in MPa ferrite perlite retained austenite bainite martensite 68
Adjustment of multiphase structures of hot-rolled strip 69
Multiphase steels 70
Characteristics of Dual Phase (DP) steels 71
Dual Phase steels: materials concept 72
Multiphase steels 73
Characteristics of TRIP steels 74
TRIP steels: TRansformation Induced Plasticity 75
TRIP steels: The TRIP-effect Stress Strain 76
Multiphase steels 77
Characteristics of complex phase steels 78
Complex phase steels: materials concept 79
Stress-strain behavior of automotive steels 80
Outline • Automotive evolution • Car body structures • Automotive steels • Mild steels • High strength steels • Multiphase steels • Press hardened steels 81
Direct - indirect press hardening 82
Properties of press-hardened steel sheet 83
Temperature gradient during press hardening 84
Protection of blank surface 85
Demands on the surface coating 86
Changing of surface and microstructure 87
Trend of hot forming of steel 88
Hot stamping 89
Hot stamped of tailored blanks 90
Innovation Tailored Tempering 91
Press-hardened B-pillar 92
Body of Audi A4 93
Press-hardened parts in VW Passat 94
Example of a press-hardening plant 95
Heating of the blank 96
Blank B-Pillar after heating just before hot stamping 97
Hot stamping 98
Application of advanced high strength steels 99
Trend of advanced high strength steels World Japan 100
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