ArcelorMittal’s extensive product offering includes a MartINsite® line, with tensile strengths ranging from 900 MPa to 1700 MPa, which helps today’s automakers shed weight from simpler shapes that can be manufactured by roll forming. Usibor®, a press hardened steel grade, supports weight reduction in more advanced shapes that require higher tensile strength. And, S-in motion offers weight reduction solutions for 43 key vehicle parts for the front, side and rear body structure plus additional solutions for hang-on doors, chassis and exhaust parts.
Typically produced using low carbon content, CS is used in applications with more limited forming requirements.
A specification of steel with excellent formability characteristics which is recommended for difficult forming applications. DDS is also available in standard and extra low carbon forms. It is sometimes produced using ultra low carbon (ULC) or interstitial free (IF) steels.
A highly formable specification of steel ideal for the most difficult forming applications where other steels lack sufficient ductility. This product is produced using IF steel, requiring the use of a degasser in steelmaking as well as close control of alloy additions.
These specifications are unique in that they are designed to increase yield strength after the paint curing process, providing the benefit of both superior formability over traditional high strength steels and higher part strength than previously described specifications. They acquire their added strength via the amount of strain generated in the part during stamping, and through the time and temperature inherent in the paint curing process.
HSLA specifications offer higher strengths for applications where forming requirements are not as severe as previously described specifications. The product is sold to guaranteed mechanical properties of yield strength, tensile strength and elongation. The strength is obtained not only through carbon and manganese but also through the addition of one or more microalloys (Cb, Ti, V) coupled with controlled processing.
Carbon steels containing more than 1.2 percent up to approximately 1.8 percent manganese are referred to as Carbon Manganese steels. The manganese content in carbon steels is increased for the purpose of increasing depth of hardening and improving strength and toughness.
DP steels offer an outstanding combination of strength and initial drawability as a result of their microstructure, in which a hard martensitic or bainitic phase is dispersed in a soft ferritic phase. These steels have high strain hardening capacity. As a result, finished part mechanical properties, especially yield strength, are superior to those of the initial blank. These steels have excellent fatigue strength and good energy absorption capacity, making them suitable for use in structural parts and reinforcements.
TRIP steels offer an outstanding combination of strength and ductility as a result of their microstructure. They are suitable for structural and reinforcement parts of complex shape. The microstructure of these steels is composed of islands of hard residual austenite and carbide-free bainite dispersed in a soft ferritic matrix. Austenite is transformed into martensite during plastic deformation, making it possible to achieve greater initial elongations. High strain hardening capacity and high mechanical strengths lend these steels excellent energy absorption capacity. TRIP steels also exhibit a strong bake hardening effect following deformation, which further improves their crash performance. TRIP steels are particularly well suited for automotive structural and safety parts such as cross members, longitudinal beams, B-pillar reinforcements, sills and bumper reinforcements.
(PHS) – Usibor®
PHS are designed to be heat treated and then quenched during the hot stamping process. The mechanical properties of the final part make significant weight savings possible. The very high yield strength of these steels after heat treatment and hot stamping make them suitable for anti-intrusion components such as fender beams, door reinforcements and B-pillars. Usibor® has an aluminum-silicon pre-coating and was developed to protect the metal from oxidation (scale) and decarburization during the hot stamping process. The coating offers excellent resistance to oxidation resulting from the hot stamping heat treatment process. Final parts using this forming technology have improved corrosion resistance after painting.
ArcelorMittal’s martINsite® ultra high strength steels consist of fully martensitic microstructures offering some of the highest strength levels available in the marketplace. These steels offer much higher strengthto-weight ratios than conventional cold rolled steels. Although limited in formability, alternative available manufacturing technologies such as roll-forming are used to fabricate these grades. Typical applications for martINsite® grades
ArcelorMittal offers a wide range of Mild steels. Depending on the formability requirements the appropriate sheet steel grade may be selected. Steel grades range from Commercial Steel (CS), which have the reasonable formability to grades like Extra Deep Drawing Steel Plus (EDDS Plus) which offers superior formability.
All of these grades are low carbon grades. Some of the highly formable steels contain ultra-low levels of carbon and are fully stabilized with microalloying elements like titanium and/or niobium.
These steels are also commonly known as interstitial-free steels, i.e. these steels have no free, interstitially available, carbon or nitrogen.
These steels are the most widely used grades in the automotive industry. They offer excellent formability and can be used for a range of parts from simple small brackets to complicated shapes like wheelhouses and floor-pans. The lower strength of these steels, can limit their applications where dent resistance, durability and high strength requirements are essential. These grades have excellent manufacturability and can be easily joined using conventional welding techniques. Except for CS, all others grades are available as exposed quality steels, also.
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