The raw material for wire mesh is called wire rod. Wire rods are available as low-carbon steel wire rods and stainless steel wire rods, typically supplied in coils. Their diameter ranges from 5 mm to 19 mm (commonly 6-9 mm). Before wire drawing, surface treatments such as pickling, rinsing, phosphating, rinsing again, soaping, and drying are performed to remove rust and iron oxide layers. These treatments also prepare the surface for subsequent drawing processes.
In the wire mesh industry, low-carbon steel wire rods with grade Q195 are widely used.
Wire Drawing Process
The process of reducing the diameter of a wire rod is known as wire drawing. Under the traction of the capstan on a wire drawing machine, the rod passes through the die hole of a drawing die, reducing its cross-sectional area, altering its shape, and meeting required dimensions, shapes, and properties. Wire drawing usually involves multiple passes, with individual reductions in cross-sectional area typically between 10% and 40%.
The primary dies used for wire drawing include fixed dies, roller dies, and rotary dies, with fixed dies being the most common. A fixed die is made from a single material, typically disk-shaped with a central hole. It remains stationary during the drawing process.
Hard alloy dies are widely used today. In addition to hard alloys, natural diamonds are also used for die-making; however, due to their scarcity and high cost, diamond dies are reserved for drawing alloy steel fine wires or ultra-fine wires.
Wire Drawing Categories
The First Drawing (Large Drawing): Reduces the diameter of 6.5 mm wire rods to 3 mm, 2.5 mm, or 2 mm.
The Second Drawing (Medium Drawing): Further reduces 3 mm, 2.5 mm, or 2 mm wires to 0.7 mm or 0.6 mm.
The Final Drawing (Micro Drawing): Produces even finer wires from the above dimensions.
During cold drawing, the structure and mechanical properties of the wire change, leading to work hardening. As cold deformation progresses, tensile strength, hardness, and elastic limit typically increase, while elongation and reduction of area decrease.
Annealing Process
When deformation reaches a certain level, the wire's cold workability diminishes significantly, necessitating intermediate heat treatment (annealing) to restore workability.
Annealing involves heating low-carbon or stainless-steel wires in annealing furnaces or tanks to a suitable temperature, holding them at this temperature, and then cooling them slowly. The annealed wires are then referred to as annealed wire.
Purpose of Annealing:
Reducing hardness and improving machinability.
Eliminating residual stress to stabilize dimensions and reduce deformation or cracking.
Refining grains, adjusting structures, and eliminating defects.
Simply put, annealing restores the internal molecular structure of metal wires, making them suitable for further drawing.
With this process, the basic raw material—wire rods—is transformed into wires of various diameters, ready for subsequent processing and manufacturing into wire mesh products.
