Hyundai Motor plans to more than double the proportion of high strength steel used in its vehicles starting with the upcoming new Sonata sedan, which will make its Korean debut in March, industry sources said Tuesday.

The revamped Sonata, in particular, will become the first Hyundai brand car to be almost 50 percent covered with high tensile steel frames. The carmaker has already applied the strength steel to some 40 percent of its latest Genesis luxury sedan.

As part of efforts to seek higher fuel efficiency and lower weight, Hyundai and its steel-making affiliate Hyundai Steel have teamed up to create high strength, light alloys that will help its vehicles lose about 10 percent in weight from this year.

The current ratio of high-strength steel used in Hyundai and Kia vehicles is at about 21 percent on average across its car lineups.

“The reduced weight will consume less fuel while elevating driving stability overall,” said a Hyundai official. “We are continuing research to apply different steel to different segment cars.”

Another source added, however, it was unlikely that the Hyundai-developed high-strength steel would be supplied to other carmakers due to production constraints.

Hyundai also buys steel from other steelmakers such as Korea’s POSCO and Japan’s Nippon Steel.

The Sonata, debuted in 1985, is one of the best-selling sedan models in Korea and has sold more than 3 million units in Korea alone.

With most specifications staying under the veil of secrecy, the upcoming seventh-generation version is expected to embrace the Fluidic Sculpture 2.0, an upgrade of the original Fluidic Sculpture design philosophy that was also applied to the new Genesis.

Following the Seoul unveiling in March, the carmaker plans to debut the car in the U.S. during New York Auto Show in April.

By Lee Ji-yoon (jylee@heraldcorp.com)