High chrome white irons (HCWI) are renowned in mining ore processing plants for their hard-wearing, abrasion-resistant qualities. They have proven ideal for highly durable mill liners and for protecting ore chutes.
Johannesburg-based Mitak is one of the largest dedicated HCWI foundries globally. “Mitak was established in 1973 and, over the years, we have developed a great understanding of the HCWI alloy range,” says Mitak business development director Graham Anderson.
In mining, two of the harshest applications for cast components are in mill linings and in ore-handling chute linings. Both are typically subject to extreme levels of erosive, corrosive and gouging wear. Over the decades, Mitak has developed a range of singularly effective HCWI alloys suited to these conditions.
Mitak has built the quality of its HCWI products on the expertise of its metallurgical and production teams. As such, it specialises in abrasion-resistant solutions and possesses extensive knowledge in the area of corrosion retardation. The company manufactures liners for use in wet or dry milling applications, for ball, rod and fully autogenous grinding mills.
“Over the past 45 years, we have manufactured nearly 500 sets of mill liners and, in the process, built up a vast reservoir of expertise for a range of comminution and materials handling applications and enabled the development of specialised alloys that meet world-class mill liner standards,” Anderson says.
Employing more than 500 people, Mitak currently casts more than 850 t/m, with the capacity to cast up to 1 000 t/m. It is one of the few foundries in the world that can cast HCWI castings weighing up to 18 t finished mass.
“A major advantage offered by Mitak is that we are a ‘one-stop’ supplier. The entire manufacturing process, from pattern-making, casting, machining, heat treatment and inspection, is carried out at the Alrode site. This allows for stringent quality control at every step of the process,” he explains.
These manufacturing processes are supported by Mitak’s considerable metallurgical and application knowledge.
“At Mitak, we have the ability to reverse engineer existing liners with the use of the latest laser and optical equipment. The company can then render the liners as solid models and supply full digital assemblies of the mill,” he adds.
More cutting-edge technology assists Mitak in the manufacture of the patterns and the company has invested in one of the country’s largest computer numeric-controlled, five-axis pattern millers, which ensures the pattern exactly matches the solid model from which it is derived. Mitak also has the capability to manufacture patterns with great accuracy using additive printing processes.
“We further employ some of the latest advancements in moulding and heat treatment to manufacture the cast components, which ensures the correct level of quality and that the casting concerned mates accurately with existing components,” Anderson continues.
Finally, Mitak uses the latest digital technology to check the parts after they are cast.
The development team also conducts ongoing research into new applications for HCWI as well as new techniques to improve the wear-resistance and mechanical strength of the liners it produces.
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