Ores are mixtures of rock and minerals from which metal oxides, non-metallic minerals, or coal can be extracted. Once the ores are removed from the earth, they are processed mechanically – crushed, sorted, ground, screened, decanted, filtered, and dried –before undergoing a metallurgical process to refine them into the final product. Metallurgical operations include hydrometallurgy or pyrometallurgy coupled with final refining by electrolysis (electro-refining or electrowinning).
These metallurgical processes are complex chemical reactions occurring in tough operating conditions, and every location is different due to the residuals found in the process water. Several corrosion mechanisms are often at work simultaneously.
The mining industry has come to depend on Sandmeyer Steel Company for a wide variety of stainless steel plate and plate products. Our materials are used in the fabrication of mining screens, fluidized bed boilers, heat exchangers, tanks, vessels, pipes, pumps, clarifiers, mixers, chutes and hoppers, dryers, kilns, furnace parts, cathodes, filters, conveyors, and coal trailers and railcars.
The hydrometallurgy process usually involves three steps: (1) leaching, (2) solution concentration and purification, and (3) the final metal refinement. 304L/304, 316L/316 and 317L/317 have been, historically, the go-to materials for this process. However, in leaching tanks, superaustenitic 904L and super duplex 2507 are finding increased usage. In heaters and flash vessels, material selection will depend on the salinity and quality of the process water. When chloride levels are high, superaustenitic SSC-6MO can replace titanium or nickel alloys. When chloride levels are low, or in cooler operating temperatures, duplex 2205 works well. In drying applications, 904L and SSC-6MO are popular choices. 2507 is often specified for improved wear resistance and extra resistance to localized corrosion.
In pyrometallurgical processes, the minerals and ores undergo a thermal treatment, bringing about a physical and chemical transformation into valuable metals. Sandmeyer can offer a wide range of heat-resistant stainless steels and nickel alloys offering high temperature resistance, strength, and oxidation resistance, such as 309S/309H/309, 310S/310H/310, and 330.
In the roasting process, materials must withstand the presence of sulfuric acid from SO2 gas downstream. Highly alloyed superaustenitic materials like 904L and SSC-6MO are used in these areas. Our duplex alloys are often used for filters and precipitators.
In the final electrolysis mineral refining operation, both 316L/316, 2205, and 2304 are used for cathode plates.
Duplex grades LDX-2101®, 2205, 2304, and 2507 are finding increased use as cost-effective substitutes to the austenitic grades for thickeners and storage tanks in copper mines.
410 and 410S plates and plate products are used extensively in the coal industry. Applications include coal filters, conveyor systems, sieve bend holders, over the road trailers, and railcars.
Finally, nickel alloy 330 is used extensively in the manufacturing of perlite furnaces for its heat resistance.