Imagine the weight of 24 elephants bearing down on a tiny spot the size of a postage stamp.

That’s how much pressure Nippon Steel Corp.’s strongest metal can withstand. The firm is pushing the envelope in order to stay relevant as the auto industry, its most important customer, goes through major changes.

Steel has been the main material in cars since Henry Ford started mass producing them a century ago. But the heavy metal is falling out of favor because automakers can’t meet new fuel efficiency standards or build long-range battery-powered cars without shedding precious pounds. Several years ago, Ford Motor Co. decided to build its best-selling F-150 pickup truck mostly out of aluminum — and steel-makers have been panicking ever since.

That’s why Nippon Steel opened a research department last April to come up with tricks for making car parts lighter, using advanced grades of the material it’s been smelting for 118 years. In January, the firm unveiled the results of the new approach; an all-steel car body, built in-house, which it says cuts weight by 30 percent, putting it on par with aluminum.

“There’s this idea out there that steel is an old-fashioned material, but it’s not true,” Nippon Steel’s laboratory research head, Nobuhiro Fujita, said last week at a briefing in Yokohama.

For years, cars have actually been gaining weight, not losing it, adding about 880 pounds (400 kg) in the last two decades alone, according to automotive consultancy A2Mac1. Beefier beams and pillars for added crash protection and more amenities like power seats have been the main culprits, along with popularity of behemoth pickup trucks and SUVs.

But now tighter emissions rules are forcing manufacturers to consider dieting. Even in North America, where fuel efficiency targets are less ambitious than in Europe and China, the curb weight of new vehicles will drop about 7 percent, or 270 pounds (122 kg), between 2015 and 2025, according to market researcher Ducker Worldwide.

The pressure will only increase as automakers produce more electric cars because batteries aren’t powerful enough to carry extra weight and still propel cars for long distances.

Over time, this will mean more aluminum, more exotic materials like carbon fiber and magnesium — and less steel. By 2025, steel will account for only 62 percent of the weight of the average new vehicle, down from 70 percent in 2015, according to Akihito Fujita, a New York-based consultant at Nomura Research Institute America Inc. “The move away from steel is inevitable,” he says.

No one will feel the pain of those changes harder than Nippon Steel. Competition with lower-cost rivals in China has made it more difficult to make money selling construction materials and the firm now relies on the auto industry to buy about 30 percent of its output, according to Takeshi Irisawa at Tachibana Securities Co. in Tokyo. Nippon Steel doesn’t disclose the numbers in its financial reports.

“They don’t have any replacement for cars,” the analyst said.

Still, aluminum has made fewer inroads than expected since the release of Ford’s F-150 pickup in 2015. General Motors Inc. mocked the material’s durability in TV ads that showed the F-150’s aluminum truck bed cracking when heavy objects were dropped into it.

Another blow came in 2017, when Tesla Inc. switched to steel for the body of its first mass-market car, after using aluminum on earlier luxury vehicles. Nissan Motor Co. also chose a mostly-steel body for its Leaf, which is the world’s best-selling electric car. Toyota Motor Corp., a key Nippon Steel customer, has done the same for its plug-in hybrids.

“We have to keep costs down,” Toyota’s head of advanced R&D, Shigeki Terashi, said last month.

To persuade auto customers to stick with them, though, Nippon Steel is trying to show that steel can also be a weight-saver, if it’s superstrong and used cleverly.

The car body it exhibited at a Tokyo trade fair in January cuts weight by 30 percent using a half-dozen different grades of the metal. The strongest has a tensile strength of 2,000 megapascals, which means it can withstand 290,000 pounds (131,542 kg) of pressure per square inch — several times more than the advanced steel commonly used in cars today — without breaking.

Nippon Steel’s engineers also found ways to redesign components so they could be made with less material. For example, they used a combination of thinner body panels and reinforcement bars to shave 20 percent off the weight of door modules, without sacrificing strength.

The next goal is to prove that high-grade steel can be used to cut the weight of car bodies by half.

That may require some compromise, though, since steel can only get so strong or light. To push the limits, Nippon Steel is experimenting by mixing small amounts of plastics with the metal it’s been producing for decades.

“We want to do the most we can with steel,” said Fujita, the company’s laboratory head, “but we’re not taking the competition for granted.”

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