CN code 681591 covers articles of stone containing magnesite, dolomite or chromite, classified as magnesia-based refractory materials. These products are distinguished by outstanding thermal and chemical resistance, making them indispensable in industrial processes that operate at extremely high temperatures over long campaign periods. Magnesite as a raw material provides structural stability when in contact with basic slags and molten metals, which is critical in steelmaking furnace applications. Dolomite-based refractories enhance resistance to chemical corrosion from aggressive slags, while chromite additions improve mechanical strength and thermal shock resistance under fluctuating temperature conditions. These products are manufactured in various shapes including bricks, blocks, plates, special precast shapes and monolithic elements produced by ramming or casting techniques. The quality of the mineral raw material and the precision of the high-temperature firing process are decisive factors determining the performance characteristics of the finished product during intensive industrial service. Periclase, the sintered form of magnesia, is the primary crystalline phase providing the essential high-temperature properties to these refractory grades.

Refractory articles containing magnesite, dolomite and chromite are widely used across the steel, cement, glass and ceramics industries where process temperatures exceed what conventional materials can withstand. In steelworks and electric arc furnaces they form the working lining that requires planned replacement due to intensive wear from liquid metal and molten slag contact over each campaign. Ferroalloy furnaces, basic oxygen converters and open-hearth furnaces demand materials of the highest chemical purity and structural homogeneity to resist aggressive process conditions. In the cement industry, magnesia-based materials are essential in the burning zone of rotary kilns where temperatures routinely exceed 1400 degrees Celsius and thermal cycling is continuous. The glass and ceramics industries employ these refractories as linings for tunnel kilns and shaft kilns operating under continuous production schedules. The petrochemical sector uses magnesia refractories in steam reformers and hydrocarbon cracking furnaces. The lime burning industry relies on dolomite linings in shaft and rotary kilns. Selecting the correct refractory grade is critical for the service life of industrial installations and uninterrupted production continuity.

CN code 681591 covers stone articles containing magnesite, dolomite or chromite that do not fall within other more specific subheadings of Chapter 68 of the Combined Nomenclature. When importing these goods it is essential to correctly identify the mineral composition, as the percentage content of individual components determines classification within the appropriate subheading and applicable duty rate. Customs documentation should include a technical specification declaring the percentage content of MgO, CaO and Cr2O3, certified by an accredited analytical laboratory. These goods may be subject to chemical safety inspections under the REACH regulation, especially for chromite-containing articles where the chemical valence state of chromium must be confirmed. Hexavalent chromium is classified as a substance of very high concern and is subject to strict import controls. Importers should hold up-to-date chemical composition certificates issued by accredited laboratories and retain them for post-clearance audits. Tariff classification requires analysis of both the production process and the intended end use of the article, as this may influence applicable preferential tariff rates. When classification is uncertain, importers may apply for a Binding Tariff Information decision from the competent national customs authority before the first import consignment arrives.

Refractory articles of magnesia, dolomite and chromite under CN 6815 91 carry a 0% EU duty. Used in metallurgy and ceramic industries.