Given the renewed optimism and focus on the U.S. steelmaking industry, many of these operations are exploring converting to cleaner, more environmentally friendly induction melting technologies. Electric arc furnaces are the standard for steel melting and refining. EAFs are typically high capacity, forgiving furnaces that take large, dirty, and less expensive scrap and produce up to 100 tons per hour. Although EAFs are less expensive to maintain than induction furnaces (IF), in the short term, disadvantages include greater dust volume and oxidation loss, high noise levels, ongoing electrode cost and power line disturbances.
Induction melting uses no electrodes and are more environmentally friendly. In addition, induction furnaces, typically smaller in size, now provide greater capacity. With a growing demand for steel products, a greater environmental focus, and the increased capacity of induction furnaces, the previous gap between the two furnace types is rapidly narrowing.
When considering melt furnaces types, there are several factors involved, the top three of which are the rising cost of electrodes, electricity load and pollution control.
1. Rising electrode cost. A major concern for factories with EAFs is the skyrocketing prices of graphite electrodes — a necessary component for their operation. Due to a lack of global suppliers, the cost of electrodes is increasing exponentially and not expected to decrease again. Recently as low as $1 per pound, they are currently $16 per pound and the cost continues to skyrocket.
Although many EAF users hold out that electrode costs will decline, it’s difficult to deny that is one of the most common reasons that mills are considering an induction alternative.
Induction technology does not use electrodes. Instead, an electromagnetic field created within the furnace induces melting. This field has other advantages besides saving on the cost of electrodes. It allows for better alloy control as it has an inherent stirring capability, which helps additives integrate more completely into the melt.
2. Electricity load. To date, induction technologies for steel have been more popular outside the U.S., where electric utilities are prone to brownout and blackout conditions. Induction furnaces have greater stability in their current draw compared with the high charge necessary for an EAF. With induction, steel mills can heat the steel quickly, bring it to an exact temperature, and easily maintain that temperature.
In the U.S., where the power grid is more stable, most use arc furnaces, which require a low initial capital outlay, have low maintenance costs in real dollars, and have considerable output based on their huge size. However, lately induction furnaces in the U.S. are seeing an increase in use mainly for energy and environmental reasons, as well as to increase capacity.
3. Pollution control, Estimates are that the steel industry spent more than $7 billion for environmental control over three decades to adhere to national standards requirements. Annually, iron and steel plants spend approximately 15% of their capital expenditures on environmental projects.
In steelmaking, emissions are generated during charging, melting, refining, tapping, and slag handling. Under the Clean Air Act, U.S. EPA established maximum achievable control technology (MACT) standards to control these hazardous pollutant emissions. The EPA also established strict ambient-air quality standards for fine particulate matter and gases that contribute to urban smog. Title V of the Clean Air Act tightens administrative control and monitoring requirements for the industry as well.
Dust generation is the major concern for all steel furnaces. EAFs and their high-energy operations tend to generate large quantities of dust, resulting in a high cost for dust removal. Dust collection is still necessary with coreless induction furnaces, however, at an approximately 85% lower rate.
Along with a lower capital investment, reduced emissions inside and outside of the mills and friendliness to shaky power grids, the use of induction furnaces for steelmaking allows for better temperature control and lower metal losses.
However, induction furnaces require smaller, cleaner, scrap, both of which are more expensive, and while induction furnaces are more efficient and cost-effective in the long-run, there is significant initial cost to convert from an EAF to an IF.
To a steelmaker in Indonesia, it was clear that to stay competitive and offset low margins it would need to reduce operating costs and raise productivity and efficiency. Together, Inductotherm and the steelmaker created a master plan based on best practices for each of its locations. Replacing five 40T EAF systems with 12 IFs, in sizes ranging from 15T to 40T, the company was able to balance cost and quality effectively while achieving cleaner steel that reduced refining requirements.
Large steelmakers also are considering induction technology to improve productivity and handle excessive emissions, to comply with MACT requirements. A major iron foundry operating six EAFs with a capacity of 13-15 mt/heat each (85 tons of ready-to-pour molten metal) determined that it wanted to update its melt department to maintain competitiveness. Based on extensive research of all equipment available, this iron foundry chose the coreless induction furnace and installed three 20-mt steel shell coreless furnaces with back tilting for slag removal, integral closed-capture fume collection covers, and refractory push out systems.
With this new system, this large iron foundry was able to save $45/ton shipped.
It is impossible to point to EAF or IF technology and assert that it is hands-down the best. Instead, it is most important to understand the business goals in regard to operating costs, productivity, efficiency and environmental requirements, and then research the path that delivers on those goals.
It is also important to grasp that there are many variables, including the escalating cost and shortages of electrodes, expanding environmental concerns, and the political moves underway to address a global trade imbalance. All of these factors have an impact on steel or iron production and its cost.
What should be clear is that both methods will coexist for a long time to come, although the gap will continue to narrow as induction benefits continue to be recognized.
Learn more by visiting Inductotherm Corp., www.inductotherm.com