Wire rod production is a specialized steel rolling process that transforms semi-finished steel billets into long, thin rods wound into coils. These rods are widely used in construction, fasteners, springs, bearings, and as raw material for wire drawing.
The process begins with heating steel billets in a reheating furnace to a uniform rolling temperature of about 1100-1250C. The hot billets then pass through a series of rolling mills-roughing, intermediate, and finishing stands-where their cross-section is progressively reduced and elongated to the desired wire rod diameter, typically between 5.5 mm and 16 mm.
Wire Rod Production Process
The wire rod production line typically involves several key stages, transforming raw material into finished wire rods. Here's a breakdown of the process:
Material Preparation:
The process begins with steel billets, which are typically square in cross-section and a few meters long. These billets are inspected for defects before being loaded into a reheating furnace.
Reheating:
The billets are heated to a specific rolling temperature, usually around 1000-1200°C, in a reheating furnace. This makes the steel malleable enough to be shaped.
Roughing Mill:
Once heated, the billets are passed through a series of roughing stands. These stands have progressively smaller grooves that reduce the cross-sectional area of the billet and increase its length. The shape might transition from square to oval or round.
Intermediate Mill:
After the roughing mill, the elongated steel (now often referred to as a bar) enters the intermediate mill. More rolling stands further reduce the cross-section and refine the shape.
Finishing Mill (Wire Rod Mill):
This is the crucial stage for wire rod production. The finishing mill consists of numerous rolling stands, often arranged in a compact block (e.g., a "no-twist" mill), that rapidly reduce the bar to the final desired wire rod diameter. This section operates at very high speeds.
Cooling and Laying Head:
As the wire rod exits the finishing mill, it's moving at incredibly high speeds. It then passes through a controlled cooling section, often using water, to achieve specific metallurgical properties. After cooling, the wire rod enters a "laying head" which forms the continuous rod into rings, laying them down onto a cooling conveyor.
Cooling Conveyor:
The rings of wire rod are then conveyed through a controlled cooling section, often in open air or with forced air, to further cool them to ambient temperature. This controlled cooling is critical for achieving the desired microstructure and mechanical properties of the wire rod.
Coiling and Compacting:
Once cooled, the wire rod rings are collected, compacted into coils, and tied with straps to maintain their shape.
Inspection and Storage:
The finished wire rod coils are then inspected for quality, dimensions, and surface defects before being moved to storage or directly to the next processing stage (e.g., drawing into wire).
After rolling, the hot wire rod is guided to a controlled cooling system (such as the Stelmor line), where air cooling ensures uniform mechanical properties and prevents surface defects.The rod is then passed through a laying head, which winds it into loose rings and forms large coils.
Once cooled to room temperature, the coils undergo inspection, strapping, and packaging before being delivered to customers. Modern high-speed wire rod production lines can achieve speeds exceeding 100 m/s, ensuring high efficiency, consistent quality, and the ability to produce a wide range of steel grades.
