At its Finnish plant in Åminnefors, Lesjöfors manufactures heavyweight hotcoiled springs that weigh between five and 300 kilograms and are used in such applications as valves, industrial robots, high-voltage engineering, train carriages and crushing equipment. Lesjöfors is now investing in an induction furnace to replace the plant’s old gas furnace, a change that is expected to reduce the company’s environmental impact.
The capacity of the plant is extensive and approximately 1,500 tons of steel were used in its manufacturing operations in 2008. The plant’s steel is delivered in bars that are heated and coiled into springs. The steel material is heated to about 900 degrees Celsius, which means that the steel exceeds its hardening temperature. This step is necessary to ensure that the finished springs are extremely strong and durable. In the past, this heating process was conducted in a gas furnace, but in 2008, Lesjöfors decided to invest in a new technology.
“The old furnace was worn and needed to be updated. We also needed to expand our capacity, so we decided to invest in an induction furnace instead,” explains Dan Manninen, Managing Director of Oy Lesjöfors Ab.
During induction, the steel material is fed through a spool through which power is simultaneously conducted. A magnetic field around the spool heats the steel material. Use of this new technology has cut gas consumption at the plant in half, thereby reducing emissions of greenhouse gases. Although induction also results in increased electricity consumption, the plant’s energy consumption has nonetheless decreased in relation to its production volumes as a result of several investments being made, including an investment in increased automation at Åminnefors.
“Induction is efficient since heat is only produced while the steel material is being fed through the spool,” explains Dan Manninen. “This level of precision cannot be achieved with a gas furnace, which needs to be in operation continuously and often runs on idle.
“Another advantage is that the capacity of the entire plant has now increased by 20 to 30 percent,” continues Dan. “These investments will also enhance our quality level since induction technology improves the surface properties of the steel.”