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Electroslag Remelting (ESR)

Electroslag Remelting (ESR)

Product catalog summary

Introduction to Electroslag Remelting (ESR)
Electroslag Remelting (ESR) is a process known since the 1930s, gaining recognition for mass production of high-quality ingots over the following decades. It is used for producing tool steels, superalloys, and heavy forging ingots up to 165 tons.

Process Technology and Characteristics
Unlike Vacuum Arc Remelting (VAR), ESR uses a consumable electrode dipped into a slag pool in a water-cooled mold. An electric current heats the slag, melting metal droplets from the electrode, which solidify at the mold's bottom. This process results in homogeneous, directionally solidified ingots with high structural integrity and surface quality, making it ideal for high-performance superalloys in aerospace and nuclear industries.

Process Control
ESR requires precise control of remelting parameters for consistent ingot quality. Modern ESR furnaces use computer-controlled automation for process management, including data acquisition and operator interfaces for visualization and control.

Metallurgy of the ESR Process
The ESR process cleans metal of impurities as droplets pass through the slag. The slag composition, typically involving calcium fluoride, lime, and alumina, is crucial for effective remelting. The process minimizes defects like tree ring patterns and freckles, ensuring high purity and structural soundness.

ESR Furnaces
Advancements in ESR furnace design focus on automation and coaxial current feeding to improve metallurgical properties. Variations include remelting under protective atmospheres and increased pressure to enhance nitrogen content in ingots.

Pressure Electroslag Remelting (PESR)
PESR introduces nitrogen into steel, enhancing properties like yield strength. The process operates under high pressure to retain nitrogen during solidification, crucial for producing advanced steel materials.

Process Variations
ALD has developed ESR variations including PESR, Inert Gas Atmosphere ESR (IESR), and Vacuum ESR (VAC-ESR), each offering unique benefits like reduced oxidation and improved cleanliness.

Furnace Types
ALD offers various ESR furnace designs, including pilot systems, stationary mold systems, ingot withdrawal systems, atmospheric protection systems, and pressurized/vacuum systems, catering to different production needs.

Applications
ESR is used for producing tool steels, die steels, ball-bearing steels, turbine and generator shaft steels, superalloys, nickel-base alloys, and cold rolls, serving industries like aerospace, automotive, and chemical.

Contact Information
ALD Vacuum Technologies provides contact details for offices in Great Britain, USA/Canada, Germany, China, and the Far East for further inquiries.

Catalog excerpts

EB_2011.qxd table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:12.00pt "Impact", sans-serif; } .font1 { font:25.00pt "Impact", sans-serif; } Electroslag Remelting (ESR) Electroslag Remelting Processes and Furnaces

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EB_2011.qxd table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:6.00pt "Impact", sans-serif; } .font1 { font:9.00pt "Impact", sans-serif; } .font2 { font:18.00pt "Impact", sans-serif; } 2 Electroslag Remelting ESR has been known since the 1930s, but it took approx. 30 years before it became an acknowledged process for mass production of high-quality ingots. The ESR technology is of interest not only for the production of smaller weight ingots of tool steels and superalloys, but also of heavy forging ingots up to raw ingot weights of 165 tons. Process Technology and...

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EB_2011.qxd table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:7.00pt "Arial", sans-serif; } .font1 { font:6.00pt "Impact", sans-serif; } .font2 { font:9.00pt "Impact", sans-serif; } 3 Slags for ESR are usually based on calcium fluoride (CaF2), lime (CaO) and alumina (Al2O3). Magnesia (MgO), titania (TiO2) and silica (SiO2) may also be added, depending on the alloy to be remelted. To perform its intended functions, the slag must have some well-defined properties, such as: ■ Its melting point must be lower than that of the metal to be remelted; ■ It must be electrically...

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EB_2011.qxd table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:6.00pt "Impact", sans-serif; } .font1 { font:9.00pt "Impact", sans-serif; } 165 ton ESR furnace. A fully coaxial furnace design is required for remelting of segregation-sensitive alloys in order to prevent melt stirring by stray magnetic fields. Shielding of the melt space with protective atmosphere has been the latest trend in recent years. Remelting under increased pressure to increase the nitrogen content in the ingot is another variation of ESR. ESR furnaces can be designed for remelting of round, square...

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EB_2011.qxd table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:6.00pt "Impact", sans-serif; } .font1 { font:9.00pt "Impact", sans-serif; } 5 Directional solidification must be ensured over the entire ingot cross-section and length to avoid interior defects, such as macrosegregation, shrinkage cavities and nonuniform distribution of inclusions. By maintaining the correct remelting rate and slag temperature, directional solidification can be achieved for ingot diameters as large as 2,300 mm. Accordingly, the ESR ingot is free from macro-segregation in spite of the large...

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EB_2011.qxd table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:6.00pt "Impact", sans-serif; } .font1 { font:8.00pt "Impact", sans-serif; } .font2 { font:9.00pt "Impact", sans-serif; } Remelting under Inert Gas Atmosphre (IESR) As a consquence of ALD's development work in PESR processing, ALD nowadays recommends to conduct the ESR process under a fully enclosed inert gas atmosphere at atmospheric pressure. This is a great step forward in freeing the ESR process from hydrogen pick-up prob-lem and the influence of seasonal atmospheric changes. In addition it allows remelting...

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EB_2011.qxd table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:6.00pt "Impact", sans-serif; } .font1 { font:8.00pt "Impact", sans-serif; } .font2 { font:9.00pt "Impact", sans-serif; } 7 Furnace Types ALD has developed five basic ESR furnace concepts: Pilot Systems for stationary and moving mold applications. These are particularly well-suited for experimental and pilot production, and for the perͭformance of high-versatility ESR operation at low investment cost. Stationary Mold Systems with two fixed remelting stations and one piv-oting furnace head. These are particularly...

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EB_2011.qxd table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:5.00pt "Arial", sans-serif; } .font1 { font:6.00pt "Arial", sans-serif; } .font2 { font:7.00pt "Arial", sans-serif; } .font3 { font:8.00pt "Arial", sans-serif; } .font4 { font:6.00pt "Impact", sans-serif; } .font5 { font:8.00pt "Impact", sans-serif; } .font6 { font:9.00pt "Impact", sans-serif; } .font7 { font:38.00pt "Impact", sans-serif; } Pressurized / Vacuum Systems Completely sealed Systems for ESR oprations under vacuum, inert gas, or increased pressure. These systems are particularly suited for producing...

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