OREGON ALUMINUM SMELTER INCREASING OUTPUT Northwest Aluminum Co said it will open a second pot line in mid-May, bringing the smelter here to 80 pct of its production capacity. Northwest Aluminum President Brett Wilcox, who leased the 30-year-old smelter from Martin Marietta Corp., said production would increase from around 45 tons a year at present to just over 70 tons. Martin Marietta closed and mothballed the smelter in 1984. Northwest Aluminum reopened it last December. Wilcox said a good aluminum market and several months of successful operation led to the decision to expand production.