Keep production flowing in fusion-manufactured display glass

The proliferation of smartphones and tablets has created huge global demand for display glass, and the fusion process is one common method for achieving the required quality. With many manufacturers operating around the clock, using a long-life and durable heating solution is essential.

CaptionTakashi Yamashita, Technical Engineer, Kanthal.The fusion – or overflow – process involves pouring molten glass into a refractory trough and letting it overflow down both sides. The two flows then fuse together at the base of the trough before flowing down to form a thin layer of glass. Because the glass fuses together in mid-air, with zero contact with any objects or surfaces, the process is able to achieve an exceptionally smooth and pristine surface on both sides. It can be used to produce glass thickness from two millimeters down to 100 microns.

Between the melting furnace and the refractory trough, the molten glass passes through a forehearth furnace. “Temperature uniformity on these furnaces is critical for the quality of the finished product,” says Takashi Yamashita, Technical Engineer, Kanthal. “Despite the high temperatures – typically around 1,200-1,500°C (2,200-2,700°F) – it needs to be well controlled and evenly distributed across the molten glass, so that it flows and fuses together for a smooth finish.”

The fusion process in brief

The fusion process (also known as the overflow process) involves pouring molten glass into a refractory trough and letting it overflow down both sides. The two flows then fuse together at the base of the trough before flowing down to form a thin layer of glass. Because the glass fuses together in mid-air, with zero contact with any objects or surfaces, it has an exceptionally smooth and pristine surface on both sides.

High power, high resistance

To keep up with strong global demand for display glass, manufacturers typically operate around the clock. Any downtime comes at a huge cost, so using long-life components is critical to their operations. When it comes to the forehearth furnaces, one of the biggest challenges to productivity is alkaline vapor, which can cause the heating elements to degrade.

Kanthal® Super molybdenum disilicide (MoSi2) heating elements and Globar® silicon carbide (SiC) heating elements can both deliver the high power required by manufacturers, as well as excellent temperature uniformity. Kanthal® Super in particular can be customized with a thicker 12 mm rod for even higher power output and deliver temperatures of up to 1,850°C (3,360°F). Due to its high-density structure, Globar® SG is more resistant to alkaline vapor compared with similarly sized elements.

We can adapt our heating elements to deliver even higher power and longer life depending on the furnace conditions.

“Because of our wide experience in this field, we can adapt our heating elements to deliver even higher power and longer life depending on the furnace conditions,” says Yamashita. “Our high-density elements have proven they can last longer in the harsh conditions found in the fusion process. In some cases, we have seen them last twice as long as conventional elements.”

Four benefits of Kanthal® Super heating elements and Globar® SiC heating elements in fusion processes

  1. Excellent temperature uniformity: Electric heating delivers a precise and even distribution of heat across the molten glass, to ensure a high-quality finish to the final product.
  2. High power: Kanthal’s elements can deliver the required power needed and even be customized with thicker rods for high temperatures.
  3. Durable: Globar® SiC heating elements are made with high-density material, making them more resistant to alkaline vapor and more resilient to the harsh conditions inside furnaces.
  4. Extensive experience and support: Kanthal has decades of experience working with electric heating in industrial processes. Its experts can offer technical assistance and customizations to deliver the optimal heating process.

Connected products

Here you can find the Kanthal product offering

Kanthal® Super

Kanthal® Super

Robust electric molybdenum disilicide (MoSi₂) industrial heating elements - designed for high temperatures, superior performance, extended lifespan, and unmatched flexibility. 

See product details
Globar® SiC heating elements

Read more

Our latest articles

A global heating partner you can trust

A global heating partner you can trust

Kanthal can not only provide a broad range of electric heating solutions but can also support its customers globally through the transition.

Read more
Higher quality and improved economics in the glass industry

Higher quality and improved economics in the glass industry

Kosta-Boda is famous throughout the world for the artistic excellence and technical quality of its crystal glass and crystal artware. Kosta-Boda traces its history back to the 18th century. An electrically heated feeder with Kanthal® Super molybdenum disilicide (MoSi2) heating elements has been playing its part in maintaining the superb quality of Boda products

Read more
Can heating element choice improve furnace efficiency?

Can heating element choice improve furnace efficiency?

The choice of heating element has a significant impact on the overall energy efficiency of a furnace, but it is not the only factor. In fact, if other considerations are not taken into account, the savings achieved from an energy-efficient element can quickly disappear.

Read more