During the early 1970s, Boliden grew through a joint-venture with the German company Preussag, which expanded the lead smelting and refining capabilities, and through the acquisition of the Swedish company Sala Maskinfabrik, which manufactured equipment for the mineral processing industry.
In 1976, Boliden introduced the Kaldo furnace, and the first flash smelting furnace for lead applying kaldo technology began operations at Rönnskär.
After the acquisition of the Danish metal recycling company Paul Bergsöe & Son in 1976, Boliden Bergsöe AB was established.
In 1981, Boliden acquired the company AB Arv. Andersson, which supplies electronic scrap and waste from computers for re-processing in the Rönnskär Kaldo furnace. In the same year, Boliden Contech was established to market and sell technology from Boliden's own mining, smelting and chemical operations.
In the spring of 1986, the Swedish conglomerate Trelleborg AB began acquiring shares in Boliden and by the end of 1987, Boliden was a wholly owned subsidiary of Trelleborg.
In 1987, Boliden acquired the Spanish mine company Apirsa. One year later, the Los Frailes orebody was discovered.
Between 1987 and 1992, Boliden acquired several manufacturing businesses producing brass and copper products in the Netherlands, Belgium, Great Britain and Sweden.
Following a discovery of the Sukhaybarat gold deposit in Saudi Arabia, a joint- venture was formed between Boliden and Petromin, a state-owned resource company. Gold production began in 1989 under Boliden's management.
In 1994 and 1995, Boliden made substantial investments in both the mining and smelting divisions. Garpenberg and Petiknäs were enlarged, and Rönnskär received a larger electrolysis plant.
In 1996, Trelleborg began a major corporate restructuring, which resulted in the sale of the Boliden group of mining, smelting and fabricating assets and services. The new company, Boliden Limited, was incorporated in Toronto and in 1997, the Company's shares began to trade on the Toronto and Montreal stock exchanges.