LONE STAR, Texas (AP) _ Lone Star Steel Co. will lay off more than half its work force because of collapsing world oil prices, imports and excessive inventories of oil drilling pipe.

Employment will fall to about 1,800 from the current 3,800, a spokeswoman said. At its peak in 1981, the company's manufacturing plant in Lone Star, north of Longview, employed 7,200 workers.

Officials said 35 to 45 workers will be laid off at the corporate offices in Dallas.

Company officials attributed the cuts to a depressed market for oil drilling pipes, tubes and well casings.

''Drilling is very depressed, and people aren't buying tubular goods,'' said Ike Kerridge, chief economist at Hughes Tool Co. in Houston. ''As long as people don't know what oil prices are going to do, they aren't going to drill.''

Last month, Lone Star announced it would lay off in March between 400 and 600 employees, or 10 percent to 15 percent of its work force.

''Before that action could occur, market conditions declined dramatically and everything worsened,'' said Judith A. Murrell, a Lone Star spokeswoman in Dallas.

Lone Star has recorded losses since 1983, reflecting the first decline in world oil prices. It reported a net loss of $117.1 million in 1985.

Many expected the layoffs.

''We've been through it all before, but you're still never ready for it,'' said Lone Star Mayor C.E. ''Nick'' Nichols.

Bob Hampton, president of the United Steelworkers of America local union, said, ''This time, we've been living with it and experiencing it and expecting it.''

Turitt Williams had worked at Lone Star Steel for 38 years, but Saturday was his last day. At 58, he says his benefits would be too small to live on, but he doesn't know where to begin looking for a new job.

''I'll be honest with you,'' Williams said. ''I don't have much to look forward to.''

Meanwhile, Lone Star residents have quit relying on the Lone Star plant to maintain the city's economic health.

''Everyone hopes the plant will return to full employment, but I don't think anyone in any of the area communities is going to sit around wringing their hands and waiting for that to happen'' said Mayo Lanagan, plant spokesman and president of the Lone Star Chamber of Commerce.

In the last year, a printing plant, an electronics assembly plant and a roofing manufacturer have opened in the area, employing about 500 people.

Lone Star has joined nearby Daingerfield and Hughes Springs to form the Triangle in the Pines Association to promote tourism in the area.

But residents still acknowledge the economy won't improve until the oil industry is healthy again.

''It is a terrible thing to wake up one morning and realize your destiny is in someone else's hands,'' said Steve Reese, president of Lone Star Steel Bank.