Amcast Industrial Corp. is pumping more than $150 million into plant expansion and acquisitions to take advantage of the growing popularity of aluminum castings in Europe. Officials at SAE say they expect the company's purchase of Speedline SpA of Italy and the construction of four new manufacturing plants and expansion of six others to improve its ability to meet future demand from automakers in North America and Europe. Amcast produces a variety of castings including wheels, differential casings, steering knuckles, suspension and brake components. The company cites statistics showing an increase of aluminum usage in passenger cars between 1991 and 1996 of nearly 60 lbs. (27 kg) per vehicle, plus its own increase in automotive sales from less than $100 million in 1993 to more than $450 million this year as reason for optimism.