What metals are used in a car?

What is meant by dual-phase steel?

Developed in the 1970s, dual-phase steel (DP) is a high-strength steel that provides the
advantages of high-strength steel without losing good overall elongation. As a result of its
microstructure consisting of both ferritic–martensitic microstructure. DP steel has good fatigue resistance making it ideal for automotive-related sheet-forming operations.

Mechanical properties of common dual-phase Steels

Grade designation	Yield strength (MPa), Minimum	Tensile strength (MPa), Minimum	% Total elongation, minimum, cold reduced	YS/TS ratio
DP600	340	590	21	0.58
DP800	420	780	14	0.54
DP1000	550	980	8	0.54

What is bake hardening steel?

Bake hardening is a steel that has undergone a controlled aging process during thermal treatment which is known as the bake hardening effect. This steel is an excellent choice for class-A panels that must also be dent-resistant. Bake-hardenable steels have been used for many years to downgauge exterior panels without reducing denting performance. After stamping conventional high-strength steel into the desired shape, it is baked (thermal cycled) similar to paint curing.

What is martensite state?

Martensite is the hardest phase of steel. By rapidly cooling (quenching) high-carbon steel at very high rates from the austenite–ferrite region, you form martensite. These materials have very high tensile strength but the lowest percent elongation of all the AHSS. Martensitic stainless steels are alloys that have body-centered tetragonal (bct) crystalline structure.

What does TRIP steel stand for?

Transformation-induced plasticity also known as TRIP steels is a class of high-strength steel alloys that uses higher quantities of carbon to obtain sufficient carbon content for stabilizing the retained austenite phase to below room temperature. The TRIP effect is the particular formation of islands of martensite which is surrounded by ferrite and bainite. As a result; these types of metals have a large uniform elongation, high strength, and high fracture toughness.

Chemistry of a typical TRIP steel (General Motors Corporation data).

%C	%Mn	%Si	%Al	%P	%Cr	%Ni	%N	%Ti
018	1.5	0.05	2	0.01	0.02	0.002	0.003	0.003

What is interstitial-free?

IF steel gets its name from the fact, that there are minimal interstitial solute atoms to strain the solid iron lattice. IF steels have very low carbon contents, typically in the bandwidth of 20–50 ppm (0.002%–0.005%), and commonly have manganese levels below 0.25%. As a result, they have very high elongations that can approach or even exceed 50%. They also have very high strain hardening coefficients that are advantageous when stamping very difficult-to-form parts.

High-strength low-alloy steel:

Unlike other types of conventional steels, HSLA steels are not made to meet a specific chemical composition but rather specific mechanical properties. As a result, HSLA provides better mechanical properties or greater resistance to corrosion than carbon steel.

Mechanical properties of common HSLA steels

Grade designation	Yield strength, (MPa), Minimum	Tensile strength, (MPa), Minimum	Total elongation (%)a, minimum cold rolled	Total elongation (%)a, minimum, hot rolled
300	300	400	27	27
340	340	410	25	25
380	380	450	23	23
420	420	490	18	22
550	550	620	16	18

 Comparison of mechanical properties of various grades of steel

Elongation is 50 mm with an ISO #1 tensile bar.

	Tensile strength (MPa)	Yield strength (MPa)	Total elongation (%)a	Uniform elongation (%)a	n-value
Mild steel	181	296	42.4	21.4	0.208
HSLA 340	375	480	24	13	0.15
Dual-Phase 600	355	623	26	19	0.18
Dual-Phase 800	440	825	17	18	0.13
TRIP800	503	831	27.6	21.5	0.236

Source:

C.D. Horvath, Chapter 2 – Advanced steels for lightweight automotive structures, Editor(s): P.K. Mallick,
In Woodhead Publishing in Materials, Materials, Design, and Manufacturing for Lightweight Vehicles (Second Edition), Woodhead Publishing, 2021, Pages 39-95, ISBN 9780128187128, https://doi.org/10.1016/B978-0-12-818712-8.00002-1.