Open-die forging and ring-rolling products manufacturer Frankwen Forge has been operating its new gas carburising facility for almost a year, following its commissioning in April 2025 after an 18-month construction period.

The investment was undertaken to meet growing demand from South African gear and pinion manufacturers and to expand the company’s heat treatment capability at its existing Benoni site.

Established in 1981, Frankwen Forge has made several capital investments over the years, including in machining capacity, to broaden its service offering and support an increasingly integrated manufacturing model.

While similar facilities exist locally, the company’s carburising plant is among a limited number that are available to the external market. A 2 000 m² building at the Benoni operation was repurposed for the installation, adding significant heat treatment capacity to the existing forging and machining operations.

The objective was to service existing forge customers while also attracting new clients requiring precision carburising.

“The new plant includes three vertical, electrically powered furnaces, each 2 m in diameter and 5.6 m long, with sealed retorts to ensure precise atmospheric control,” says Frankwen Forge director and GM Donovan Traube.

“The facility also houses a 60 000 ℓ oil quench tank, equipped with four agitation pumps for consistent quench performance. Additional infrastructure includes an on-site nitrogen generator and full backup power capability.”

Carburising is a case-hardening process used to increase the surface hardness and wear resistance of low-carbon steels by diffusing carbon into the component surface at elevated temperatures.

“Frankwen’s carburising process begins with cleaning and, where specified, masking components with stop-off paint. Components are then gas carburised to the required case depth, followed by controlled cooling, oil quenching, tempering and optional cryogenic treatment. Final inspection includes hardness testing, microstructural evaluation and case-depth verification using Vickers hardness measurements,” Traube explains.

The plant is primarily configured to process 655M13 (EN36B) and 17CrNiMo6 materials for applications in the gear manufacturing sector, with furnace capacity allowing for the treatment of about 40 t of components a month. Carburising cycle times vary depending on the specified case depth.

Frankwen Forge supplies forged components to original- equipment manufacturers and end-users in the mining, rail, heavy industrial equipment and power transmission sectors. The company specialises in high-integrity forgings produced from carbon, alloy and stainless steels, with a focus on long product forms such as shafts, bars, gear blanks and rolled rings.

The business has developed a vertically integrated production approach that combines billet preparation, forging, heat treatment and rough or finish machining on a single site. This enables improved control over product quality, process traceability and turnaround times.

The forging operation is supported by hydraulic presses and heavy-duty forming equipment capable of producing components of up to 10 t, with both standard and custom- forged solutions supplied to client specifications.

In-house metallurgical capabilities include hardness testing, grain structure verification, dimensional inspection and mechanical testing. These services are supported by Franktech, a sister company and South African National Accreditation System-accredited laboratory located on site.

The addition of carburising treatment extends the company’s ability to supply fully processed components that meet both mechanical property and surface hardness requirements within a single production environment.

Frankwen Forge continues to work closely with downstream manufacturers and end-users to ensure specification compliance and consistent product performance, while pursuing opportunities in specialised forged components for the mining and industrial sectors.