An overview of Trafilerie Fratelli Rotta’s wire drawing processes

Trafilerie Fratelli Rotta has been producing low, medium, and high carbon steel wires for over sixty years. Based in the historical wire district of Lecco, Italy, the company serves a broad spectrum of industrial sectors.

Through continuous monitoring of all production steps, Trafilerie Fratelli Rotta ensures consistent performance and adherence to quality requirements. Here is a short overview of the primary process stages.

Raw material

Production starts with certified wire rod featuring carbon content between 0.04% and 0.88% and diameters ranging from 5.5 to 17 mm. The carbon content and initial diameter directly influence the final mechanical properties of the wire, such as malleability and tensile strength.

Drawing on technical documentation and decades of metalworking experience, Trafilerie Fratelli Rotta selects the most suitable wire rod for each order, guaranteeing uniformity and reliability of the finished product.

Pickling and surface preparation

The rolling of wire rod leaves residual impurities on the surface. Therefore, the first step performed by Trafilerie Fratelli Rotta is a chemical cleaning process known as pickling. This treatment removes oxides and mill scales formed during rolling. The material is immersed in sulfuric acid and can then undergo phosphating and lime passivation, operations that improve surface cleanliness and lubrication.

The entire process is managed by an automatic PLC system that controls immersion time, temperature, and solution concentration. The company’s tanks are also equipped with fume extraction and filtration systems that ensure operational safety and minimal environmental impact.

Wire drawing

We now come to the actual wire drawing phase. During this process, the wire rod is pulled through a series of drawing dies with progressively smaller diameters. As it passes through each die, the metal’s grain is flattened and elongated, increasing its tensile strength while reducing its diameter.

Trafilerie Fratelli Rotta operates several production lines capable of manufacturing wires with diameters ranging from 0.8 to 16 mm, in SL, SM, SH, DM, and DH classes, in compliance with EN 10270-1. During drawing, the wire is lubricated with powder or oil, while rapid cooling systems ensure dimensional consistency and metallurgical quality.

Heat and surface treatments

Depending on application requirements, the wire may undergo specific thermal or surface treatments:

- Stelmor cooling, a standard method that preserves material structure and improves mechanical properties, ideal for medium and large diameters.
- Patenting, performed before or between drawing stages to relieve internal stresses and increase strength, particularly effective for fine wires.
- Annealing for formability, used for wires intended for cold heading or case hardening, reduces hardness and increases ductility.
- Galvanizing, which provides a variable-thickness anti-corrosion coating depending on the final application.
- Phosphating, performed after pickling, creates an insoluble crystalline coating that acts as a lubricant during drawing.

Testing and quality control

Each batch undergoes dimensional and mechanical inspections. Measuring and tensile testing equipment is periodically calibrated to ensure precision and repeatability.

The inspection certificate supplied with each delivery reports:
- actual diameter and tolerances;
- tensile strength and yield point;
- chemical composition;
- zinc coating weight (if applicable);
- number of twists and tensile test results.

The tests include micrometer diameter measurement, controlled tensile testing, and elongation and reduction analysis to assess ductility and in-service behavior.

Packaging and delivery

Packaging is carried out according to customer specifications: coils, spools, rolls, reels, or metal bobbins, with customized sizes and weights. Each unit is labeled, traceable, and supplied with an inspection certificate. Delivery can be made using the customer’s transport, a dedicated carrier, or directly by Trafilerie Fratelli Rotta.

Applications

The wires produced by FRT are used in a wide range of sectors: automotive, furniture, agriculture, metalworking, and food industries.

Main applications include springs, cables, protective sheaths, high-pressure reinforced tubes, cold-formed components, and rolled products.

Thanks to continuous process control and ongoing technological development, Trafilerie Fratelli Rotta remains a benchmark in the steel wire drawing sector, offering reliable solutions that meet the quality standards required by European industry.

For further technical details or specific inquiries, the Trafilerie Fratelli Rotta team is available for personalized consulting.