New Generation Steel for Fuel Saving

By: Mayur M Chauhan. Dy. Manger. Application Engineer, Essar Steel Ltd.

Abstract

The demand by the automotive industries to meet the environmental concerns such as global warming, CO₂ emission etc., require advanced materials which offer the best fuel efficiency. Among the metallic materials, which would meet demands of auto industries, steel has a good combination of strength, forming and drawing characteristics. Therefore, steel has been proved to be the only choice available as of yet. The exhaustive research analysis by ULSAB (Ultra Light Steel for Auto Body) /ULSAC (Ultra Light Steel for Auto Concept) has demonstrated that steel is the only material suited to meet demands of properties for auto applications and offers the possibility of weight-saving potential which results ultimately in fuel savings. The reduction in sheet thickness by use of high strength steel is being increasingly adopted as an effective means for weight reduction because of the cost and fuel savings. Why is new generation steel required for fuel saving ? Vehicle weight tends to increase from year-to-year due to added features in modern cars. As the current trend toward enhanced comfort, pollution control and safety shows no sign of abating, careful attention should be paid to weight increase, which has a direct impact on fuel consumption, especially in urban driving conditions and over short journeys, characterized by numerous acceleration/deceleration phases and stop/starts. A 10% drop in overall vehicle weight produces a drop of 5-6% in fuel consumption.

Fig 1: Class of steels available varying as a function of Yield Strength and %EL. Some of the high strength steel to meet the above requirements are as per Fig.1. The substitution of conventional low carbon steel (mild steel) by high strength steel (HSS) is increasing due to their following advantages:

• 8-12 % weight reduction and ultimately lower fuel consumption

• Ensures safety – improvement of crash resistance

• Cost down by thickness reduction of sheet

• Improvement of dent resistance and fatigue strength

Advance high strength steels like Dual Phase Steel (F+M Steel) consists of hard Martensite phase in a matrix of soft ferrite. This has become most popular due to its versatility in terms of strength and formability. It offers significant weight reduction due to high strength levels ranging from 600 to 1400 MPa, Micro alloyed , high strength, low alloy steels may have yield strength that are 2-3 times higher than hot-rolled weldable carbon steels.

Fig.2 -The weight of components can be reduced sub statically by substitution high –strength for low-strength carbon-manganese steels (Source-SSAB Sheet Steel Handbook) HSLA steels are special grades that can be considered for substitution with commonly used plain carbon steels to realize substantial cost savings. HSLA substitution for some of the low strength alloys yields benefits through savings in cross-sectional area. Essar Steel with keeping this perception, has recently developed following high strength steel products,

Hot Rolled:

Cold Rolled:

These products are supplied to Major OEMs like Tata Motors, Hyundai, Mahindra and Mahindra, Asia Motor Works, Conclusion Lightweight vehicle design for fuel efficiency is a constant concern for automobile manufacturers and proceeds along a number of fairly well understood technology and engineering routes. However, lightweight vehicle design does address environmental considerations.