Enhanced steel grade meets demanding needs

Stainless steel producer Columbus Stainless, based in Middelburg, Mpumalanga, has improved on the “workhorse” 3CR12 utility steel by adding the high-strength 3CR12HP400 version to meet the requirements of demanding applications.

The 3CR12HP400 offers the necessary corrosion resistance, along with the high-strength property requirements of a utility grade, says Columbus Stainless technical customer services manager Sean du Toit.

Columbus Stainless started 3CR12HP400 development in 2015, introducing it to the market in 2017. It is ideal for any applications that require corrosion resistance and higher strength as it offers minimum proof strength of 400 MPa, compared to the minimum strength of 280 MPa offered by 3CR12 steel.

“This was achieved by a combination of chemistry modification and rolling practice adjustments,” says Du Toit.

He adds that 3CR12HP400 steel provides an opportunity to save costs by being able to use thinner gauges on applications that would ordinarily use thicker gauges of alternative materials.

Du Toit recommends Columbus’ 3CR12HP400 product for utility applications in the mining and energy industries in Africa. He adds that the company’s duplex 2205 and lean duplex 2304 grades are also ideal for projects in mining and energy, specifically for processing equipment.

The 3CR12 grades are used for mining roof-support structures. Corrosion attack compromises the integrity of alternative-grade support structures. The 3CR12’s inherent corrosion-resistance ensures a longer-lasting support structure, he explains.

By ensuring a longer-lasting support structure, mining operations can also benefit from 3CR12’s being a more economic life-cycle cost solution for mining roof-support application.

Meanwhile, stainless steel is corrosion resistant, owing to a thin passive film on the surface, which helps to reduce maintenance of the surface.

“Unlike protective coatings on carbon steels, this passive film is self-healing in most environments, and corrosion resistance will be restored in a reasonable time if it is mechanically damaged,” Du Toit elaborates.

Stainless steel is generally used in its uncoated condition, although colour coatings or paint can be applied for aesthetic purposes.

However, in applications where aesthetics are not important, such as ore handling, stainless steel can be used with mill scale on its surface to provide an extra layer of abrasion resistance.

Further, in its uncoated condition, stainless steel is ideal for recycling, and Du Toit enthuses that this benefit is used optimally at Columbus, with newly melted products containing more than 70% recycled content. This makes stainless steels a highly sustainable product.

The resistance of the passive film on stainless steel is determined by the composition of the stainless steel; therefore, Columbus offers a variety of stainless steels that can handle various environments, Du Toit notes.

Consequently, the company can respond to market demand by offering such variety.

The company has introduced temper rolled 301L with high strength and corrosion resistance that is ideal for passenger rail cars, while grades, such as 436 and 444, have been added to ensure longer life in automotive and water applications. For high-temperature applications, types 1.4841 (310Si) and 347 are now available.

Further, Du Toit says, “Columbus has the necessary set of skilled people to develop stainless steel grades required for specific applications”.

To address skills shortage in the corrosion control and coatings sector in South Africa, the company provides bursaries for tertiary studies in engineering, business and science.

It also maintains in-house training programmes for learner-steelmakers, apprentices and technicians, in addition to engineering training programmes and skills development pro- grammes.

This enables Columbus Stainless to contribute to the development of talent to continue innovating and maintaining high standards in the stainless-steel industry.