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How Borates Enhance Refractory Application

:: Thursday, August 25, 2022 :: Posted By Maryam Moravej

Borates are widely used to enhance the properties of many materials crucial to modern products—from increasing glass durability to promoting adhesion between glazes and metal substrates to creating hard, corrosion-resistant alloys.

But borates also positively impact the processes that produce these materials.

In refractory-based manufacturing—such as metallurgy and glassmaking—borates can extend service life and reduce maintenance of essential production equipment.

Borates can:

  • Fight corrosion caused by oxidation
  • Act as a binder
  • Reduce the stress materials experience from temperature fluctuations

This gives manufacturers greater control over the longevity of production materials, enables safer working environments, and keeps production running efficiently.

How borates are used in refractories and production environments

Refractories are materials used for developing a range of industrial furnaces, kilns, and other production configurations that operate at high temperatures.

The refractory industry uses borates in the manufacturing of articles (crucibles) and as a component in mixtures (unshaped refractory products).

Borates are used most in metallurgy for refractory applications, including:

  • Carbon-bonded bricks
  • Dolomite refractories
  • Graphite crucibles
  • Gunning and patching compounds

Carbon-bonded bricks in steel manufacturing

In response to stricter steel production process requirements, steel manufacturers are using carbon-bonded bricks because of carbon’s thermal stability and ability to prevent wetting by metal and slag.

However, steel melts subject carbon to harmful oxidation. Producers must fight this effect with antioxidants. They typically turn to boron compounds because of their high melting point and high sensitivity to oxidation.

Even a small amount of boron (1 wt %) can reduce carbon oxidation in refractory bricks.

Dolomite refractories

Boric acid is used as a stabilizer in dolomite refractories manufacturing. Dolomite refractories are found in open-hearth steel furnaces and the lining of basic oxygen furnaces.

To produce dolomite bricks, you need dicalcium silicate. During the high-temperature manufacturing process, dicalcium silicate dehydrates—an inversion effect which causes the volume to increase 10%.

Such a significant inversion causes the bricks to disintegrate into a powder. Boric acid prevents this inversion from occurring.

Graphite crucibles

Manufacturers who make specialized metal and alloy castings use graphite crucibles during production. These crucibles are constantly subjected to intense heating and cooling cycles.

If left untreated, the crucibles may start to crack and leak. Corrosion caused by oxidation can also become an issue. To prevent these harmful conditions, manufacturers can dip graphite crucibles in a Neobor®/boric acid solution or coat them in a ceramic mixture containing anhydrous borates.

Gunning and patching compounds

Basic refractories in steel furnaces may apply borate-infused gunning and patching compounds to extend equipment life.

Refractory ramming mass

Refractory lining (so called ramming mass) is used in induction furnaces for melting cast iron and different alloy steels. The performance of refractory lining has a direct impact on furnace performance and borates play an important role in the manufacturing of ramming mass. Boric acid is added as a binding agent to the refractory lining to provide adhesion and strength. Alternatively, boric oxide is added as a sintering agent to produce a faster sintering cycle through reacting with silica particles to produce low a melting point glassy phase which fills the interstitial holes between silica grains.

Reduced glassmaking refractory corrosion

Glassmaking refractories experience an indirect—yet important benefit—when borates are used in production.

If a borosilicate glass manufacturer uses an anhydrous borate, such as Dehybor®, less volatile emissions are released during glass batch melting. As a result, the glass refractory experiences reduced corrosion, which extends the lifetime of the furnace—saving maintenance and replacement costs.

Extending refractory environments with borates

Where furnaces and linings are subjected to high stress, borates can help save manufacturers time and money.

By using borates, you can avoid costly downtime for equipment maintenance, reduce consumption of raw materials, and lower waste production.

Interested in learning more?

Want to know how borates can help extend the life of your refractory materials? Contact our technical experts! They can provide the support, documentation, and sample guidance you need to assess borates for your unique refractory.

Resources

U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 500 customers with more than 1,700 delivery locations globally. We supply 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles.  Learn more about Rio Tinto.

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