Vacuum Furnaces: Achieving Material Purity with SHJLPACK Technology

Vacuum furnaces, a specialty of SHJLPACK, are critical for producing high-purity materials essential in modern industries. By employing vacuum technology for heat treatment and melting, these furnaces are indispensable in sectors like aerospace and automotive. SHJLPACK vacuum furnaces ensure efficient degassing, precise alloy composition, and superior material quality, significantly enhancing manufacturing processes and product performance.

General Information on Vacuum Furnaces

Vacuum heat treatment and vacuum melting techniques are increasingly vital in modern material processing. They enable the creation of materials with properties unattainable through other methods. Vacuum metallurgy is crucial for processes like steel degassing, vacuum remelting, and precision casting, leading to high-quality castings with controlled material composition and enhanced casting quality. As technology advances, vacuum processing equipment is meeting new demands, evolving towards continuous process chains in a medium vacuum. This shift not only facilitates the development of innovative products but also significantly lowers production expenses.

These technologies are particularly effective in processing precious metal scrap, where the value of the materials justifies the equipment investment. Vacuum technology is also essential for creating high-technology and high-temperature precision steel alloys and precious metals that require exceptional purity and minimal contamination. Utilizing vacuum techniques allows for the creation of materials with fine-grained, focused, and single-crystal structures, enabling precise control over the final material properties. These advancements are crucial for high-tech sectors like aerospace, aviation, and automotive, where enhanced material strength and reliability are paramount for technological breakthroughs.

Advantages of Vacuum Melting Furnaces

Vacuum remelting is a secondary metallurgy process used to refine metals and achieve specific chemical compositions at controlled temperatures in a liquid state. Vacuum technology is indispensable for producing special alloys that cannot be made in open air or inert atmospheres due to their high reactivity to oxidation.

SHJLPACK vacuum furnaces offer several key advantages:

• Prolonged Exposure in High Vacuum: Enables extended processing time in a high vacuum environment.
• High Degree of Degassing: Effectively removes gases from molten metals, improving material quality.
• Controlled Furnace Content: Allows for partial removal and active influence on refining processes at any stage of melting.
• Precise Monitoring and Control: Facilitates real-time monitoring and adjustment of melt temperature and chemical composition throughout the process.
• High Purity Castings: Eliminates non-metallic inclusions, resulting in exceptionally pure castings.
• Rapid Heating and High Performance: Direct heating of the melt ensures quick and efficient heating cycles, leading to high throughput.
• Homogeneous Melt: Active mixing of the metal ensures uniform melt composition.
• Versatile Raw Material Input: Accommodates various forms of raw materials, including lump materials, briquettes, and powders.
• High Efficiency and Environmental Cleanliness: Offers energy-efficient operation with minimal environmental impact.

Compared to electric arc furnaces, vacuum induction furnaces (VIF) offer distinct advantages. The constant stirring of the melt in a VIF, characteristic of induction melting, promotes uniform mixing. While some metallurgical processes like dephosphorization and desulphurization are limited in VIF, vacuum remelting excels in processes requiring reduced pressure to manage reactions involving carbon, oxygen, nitrogen, and hydrogen. The ability to remove volatile elements such as mercury, tellurium, selenium, and bismuth is a significant practical advantage of VIF technology provided by SHJLPACK.

Applications and Processes

Vacuum furnace technology is crucial for obtaining special alloys. Many materials and special alloys can undergo treatments in induction melting furnaces to eliminate unwanted impurities. Sublimation during vacuum induction remelting can significantly reduce undesired elements. This makes induction melting the preferred method for producing ultra-pure alloys.

The degree of vacuum required for sublimation refining varies depending on the metal and smelting process, typically ranging from 10^-1 to 10^-3 mbar.

To achieve pure melts, SHJLPACK vacuum furnaces integrate various processing methods:

• Atmosphere control with minimal leakage and desorption.
• Selection of stable refractory materials for crucible linings.
• Electromagnetic stirring for mixing and homogenization.
• Inert gas purging.
• Precise temperature control to minimize crucible reaction with molten metal.
• Slag removal and melt filtration during casting.
• Casting through a chute or intermediate ladle to prevent oxidation.

For demanding applications, such as turbine blade production, materials from vacuum induction remelting may require further processing. Subsequent remelting or directional solidification can be applied using additional casting chambers integrated with SHJLPACK VIF systems. For even stricter purity requirements, materials may undergo multiple refining stages, such as triplex refining, combining successive induction vacuum remelting, electroslag remelting, and arc remelting.

Modern Vacuum Furnace Technology

New generation vacuum induction furnaces from SHJLPACK are designed for efficiency and compactness. They feature smaller melting chamber volumes and modular designs that allow for integration with various chambers for loading, casting, and product removal. These modern VIFs offer enhanced functionality and cost-effectiveness. The modular design allows for quick reconfiguration, and casting is typically performed using a ceramic chute to transport molten metal into the filling chamber while removing nonmetallic inclusions.

The reduced vacuum chamber size minimizes pumping time and power consumption, improves atmosphere control, and allows for quick exchange of furnace elements, such as crucibles, minimizing downtime. This design offers high flexibility in casting methods and reduces contamination risks. SHJLPACK's new generation VIF technology provides an economically viable solution for producing a wide range of metals, alloys, and precision components in controlled gaseous atmospheres.

Further advancements in vacuum technology are leading to combined processes of melting, casting, and forging, eliminating the need for additional heating and conversions, akin to continuous casting with simultaneous rolling. This innovative method involves melting metal in a vacuum chamber directly above the die-casting mold. Sensors, gas pressure control, and ultrasonic vibrations are employed to refine the melt and facilitate mold filling. The molten metal enters the die-casting mold, which moves to meet the melt, promoting rapid crystallization and a fine-grained, dense product structure due to ultrasonic treatment.

This technology enables the creation of complex shapes directly from the melt, such as turbine blades, nozzles, and automotive valves, from both standard and hard alloys with minimal machining required. The resulting structure rivals that of forged metal in quality, being fine-grained and non-porous. This significantly reduces material waste and machining costs, while achieving high manufacturing precision.

The Vacuum Melting Process Sequence

In SHJLPACK vacuum furnaces, molten metal is produced in a water-cooled crucible using an inductor. Argon gas is introduced into the chamber. Once the melt reaches the desired temperature, a sensor triggers a valve, and molten metal flows through a ceramic channel into the mold. Simultaneously, a vacuum pump evacuates the lower chamber, drawing the molten metal into the mold under gravity and pressure. An ultrasonic transducer activates upon mold filling, enhancing mold wettability, degassing the melt, and promoting fine-grained casting structure through increased nucleation. This efficient method is known for producing uniform, high-quality metal castings with superior mechanical properties, all while being environmentally friendly, economical, and compact.

This process is highly versatile for manufacturing complex shaped parts from reactive metals, hard alloys, and composite materials, including those reinforced with carbon, tungsten, or boron fibers. The potential applications are vast, spanning aerospace, shipbuilding, automotive, nuclear power, medicine, and specialized equipment industries, highlighting the broad impact of SHJLPACK's vacuum furnace technology.