Molybdenum Products for Glass Melting Electrodes (GMEs)

H.C. Starck Solutions has vast experience in the manufacturing and processing of high performance materials, including tungsten, molybdenum and their alloys. These advanced materials play a key role in the glass industry's challenging applications in feeding, melting, homogenizing, and shaping of glass products.

Advantages of Molybdenum

The electric glass melting development is predominantly based on the development of electrode materials. Indeed, there is only a limited choice of electrode materials available that are capable of meeting the electrical, mechanical, process, corrosion, and cost requirements of the glass melting process, of which molybdenum is the material of choice thanks to its outstanding properties.

The following properties make molybdenum offered by H.C. Starck Solutions an ideal material for electric heating in the glass melting process:

• Good machinability
• Reduces detrimental glass discoloring
• Superior corrosion resistance
• Low coefficient of thermal expansion
• High thermal and electrical conductivity
• Outstanding strength and stability at elevated temperatures up to 2000 °C

Capabilities of H.C. Starck Solutions

As a key supplier of refractory metals, H.C. Starck Solutions has sophisticated laboratories where it continually designs and makes innovative products and materials in close cooperation with customers for the future of the glass industry.

Electron Beam Melting

H.C. Starck Solutions employs the electron beam (EB) melting process for the production of MOLYMELT EB glass melting electrodes. Part of the raw materials used in the EB melting process is recycled molybdenum.

The process involves the bombardment of electrons in the furnace, resulting in the melting and deposition of the material into a water-cooled copper mould, where the material gets solidified into a round molybdenum ingot. The ingot is then forged and formed into the preferred shape.

Since the EB melting process is performed under high vacuum, elements that have melting points lower than molybdenum get volatilized, yielding the molybdenum over 99.95% pure and 100% dense.

Oxidation Resistant Coating

H.C. Starck Solutions constantly improves its coating processes to produce refractory metals such as molybdenum with superior oxidation resistance at high temperatures. These ceramic coatings cannot spall or separate as they are chemically bonded to the metal surface.

Since the coatings are produced through a chemical vapor deposition, they can be uniformly applied to all surfaces including the interior of thin tubes.

Recycling

Since sustainable development is one of the key guiding principles of H.C. Starck Solutions, the company helps customers recycle spent electrodes through its EB furnace.

Value-Added Product Solutions from H.C. Starck Solutions for the Glass Industry

Muride Coating

MURIDE coating provides protection against oxidation from flames, air, oxidizing chemicals and oxygen-rich atmospheres. The reliable and reproducible coating is completely compatible with molybdenum and can be applied on glass melting electrodes and other components used in the glass industry to give protection against oxidation during the crucial start-up period.

Since the coating is silica based, its dissolution has no coloration or other negative effects on the glass.

Stirrers

H.C. Starck Solutions supplies a wide selection of stirrers for homogenizing and feeding special glass melts. These stirrers meet the high requirements of the thermal and chemical uniformity of glass melts. The company produces stirrers for glass utilizing either tungsten molybdenum alloys or pure molybdenum.

Molybdenum Tubing

H.C. Starck Solutions offers tungsten and molybdenum fabrications for producing quartz tubing and for quartz melting. Using its extrusion experience, H.C. Starck Solutions fabricates large diameter molybdenum tubing ideal for quartz melting vessels, mandrels and orifice plates. Moreover, the company produces fabrications from molybdenum sheet with forged molybdenum internals.

Molybdenum Glass Melting Electrodes

H.C. Starck Solutions supplies high quality molybdenum glass melting electrodes for efficient glass melting and electric boosted melting. The combination of high-temperature strength and rigidity of molybdenum electrodes and the intrinsic electrical properties of molybdenum results in maximum operating efficiency.

The outstanding purity level of H.C. Starck Solutions' molybdenum electrodes (at least 99.95%) reduces detrimental glass discoloring, and provides high resistance to degradation and chemical corrosion. The company supplies a wide choice of electrodes for complex glass melting applications:

• Uniform recrystallized grains for creep resistance
• GMEs from 1.25" (32 mm) to 8" (203 mm) in diameter
• Bubble-free, low carbon electrodes
• Standard or tapered threads
• Machined or centerless ground surfaces for assurance of concentricity and straightness
• High purity (99.95% minimum)

Product Properties

Structure

Glass melting electrodes are generally supplied in the recrystallized condition. However, H.C. Starck Solutions can supply materials in the stress-relieved condition upon request.

Straightness

Maximum deviations from straightness will be 0.030 inch per foot (2.5 mm per meter), while maximum deviation in cut lengths will be +1/4", -0 inch (+6.35 mm, -0 mm).

Mass fraction in %
1) Information on testing methods available upon request.

Chemical Characteristics

The chemical composition of molybdenum powder utilized for glass melting electrode production shall conform to the following limits:

Length variations ± 5 mm / ± 0.2 inch

Surface Condition

H.C. Starck Solutions supplies glass melting electrodes with centerless ground or machined surfaces of3.25 µm or better. The company also provides glass melting electrodes as forged. It may be possible to remove minor surface defects by conditioning without compromising the dimensional tolerance.

Threading

European and the United States standard and special threads are available on either or both ends.

Quality Control

H.C. Starck Solutions monitors each step in its production cycle and its quality programs ensure the production of consistent and high-quality products. With highly qualified technical experts and ISO 9001 certified plants, the company develops products and processes to meet the demands of customers.

This information has been sourced, reviewed and adapted from materials provided by H.C. Starck Solutions.

For more information on this source, please visit H.C. Starck Solutions.