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August 2002 AUTOMOTIVE STEEL DESIGN MANUAL Page 2.4-1 MATERIALS Section 2.4 Hot Rolled and Cold Rolled Steels 2.4 HOT ROLLED AND COLD ROLLED STEELS 2.4.1 INTRODUCTION Steels are …… classified initially as Hot Rolled or Cold Rolled. Hot Rolled steels, finished on the Hot Mill are the most economical sheet products and are generally used in thicknesses greater than 1.83 mm (0.72″) for unexposed surfaces. Cold rolled steels are usually hot rolled to approximately 4.0 mm and then finished cold to 2.0 mm (0.080″) or less.

… classified initially as Hot Rolled or Cold Rolled. Hot Rolled steels, finished on the Hot Mill are the most economical sheet products and are generally used in thicknesses greater than 1.83 mm (0.72″) for unexposed surfaces. Cold rolled steels are usually hot rolled to approximately 4.0 mm and then finished cold to 2.0 mm (0.080″) or less.

2.4.3 DENT RESISTANT, HIGH STRENGTH AND ADVANCED HIGH STRENGTH STEELS High Strength sheet steels cover a broad spectrum of steels designed and used for higher yield and tensile strength applications than the low carbon formable steels. Many different high strength steels have been developed by the various steel producers and are available in hot rolled, cold rolled, and coated products. As indicated in an earlier section, high strength steels are specified in SAE J2340; these are listed in Table 2.4.3-1 below. Advanced high strength steels are defined in the Ultra-light Steel Automotive Body – Advanced Vehicle Concept (ULSAB-AVC) and are discussed in Section 2.4.3.3 . Descriptions are listed below: • Dent Resistant (DR) * Bake Hardenable (BH) * Non-Bake Hardenable • High Strength Solution Strengthened • High Strength Low Alloy (HSLA) • High Strength Recovery Annealed • Advanced High Strength * Dual Phase (DP) * Complex Phase (CP) * Transformation-Induced Plasticity (TRIP) * Martensitic Higher strength steels are desirable for dent resistance, increased load bearing capacity, better crash management, and /or for mass reduction through decrease in sheet metal thickness. Strength in these steels is achieved through chemical composition (alloying) and special processing. Special processing could include mechanical rolling techniques, percent cold reduction, temperature control in hot rolling, and time and temperature in annealing of cold reduced sheet. Each of these major groups of steel is discussed below. Table 2.4.3-1 High and advanced high strength steel grades as described in SAE J2340 and ULSAB-AVC Steel Description Grade Type Available Strength Grade MPa Dent Resistant Non-Bake Hardenable A 180, 210, 250, 280 Dent Resistant Bake Hardenable B 180, 210, 250, 280 High Strength Solution Strengthened S 300, 340 High Strength Low Alloy X&Y 300, 340, 380, 420, 490, 550 High Strength Recovery Annealed R 490, 550, 700, 830 Advanced High Strength See Figure 2.4.3-1 See Figure 2.4.3-1

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