 |
|
Cold-heading wire for manufacture of fasteners is used in many fields and in extremely varying applications. Examples are the transport, building, chemical, electronics/computer and white goods sectors.
Product properties.
Optimum cold-heading properties place high demands on a controlled manufacturing of the wire. Surfaces free from defects, steel grades adapted to the product, tight compositional limits, low inclusion and impurity contents, correct mechanical properties, correct work-hardening rate, even adapted surface coatings and tight size tolerances are examples of important parameters. |
| Standard Steel grades | | Size, execution and tolerances |
| ASTM | Fagersta | Semifinished
Annealed & coated. | Adjust drawn
3-15% reduction |
| T430 | R250.11 | 1.5 - 12.5mm - h10 | 1.5 - 12mm - h9 |
| T302 | R320.14 | 1.5 - 12.5mm - h10 | 1.5 - 12mm - h9 |
| T302HQ | R575.11 | 1.5 - 12.5mm - h10 | 1.5 - 12mm - h9 |
| T304L | R350.20 | 1.5 - 12.5mm - h10 | 1.5 - 12mm - h9 |
| T304 | R350.10 | 1.5 - 12.5mm - h10 | 1.5 - 12mm - h9 |
| T321 | R359.10 | 1.5 - 12.5mm - h10 | 1.5 - 12mm - h9 |
| T305 | R390.21 | 1.5 - 12.5mm - h10 | 1.5 - 12mm - h9 |
| | |
Great importance must be attached to the selection of the correct residual lubricant film on the wire supplied in order to meet the varying friction conditions depending on the cold-heading process and the product form involved. In order to ensure good lubrication properties we can offer cold-heading wire with the surface finishes below. The various surfaces have been ranked in terms of lubrication efficiency and sensitivity to moisture pick-up respectively.
Copper coating.
An electrolytically deposited copper layer is produced in a continuous production line comprised of degreasing, nickel coating (for optimum adhesion of the copper layer), copper coating, surface coating and drawing,
Copper layer thickness.
Standard = 2 mm (approx. 20g/m2)
Extra thick: 3 mm (approx. 30 g/m2) |
| Name | Surface | Surface properties |
| | Lubrication efficiency | | Moisture sensitivity. |
| Cu | Copper only | 4 | | 5 |
| CuG | Copper + graphite | 5 | | 5 |
| CuM | Copper + Molybdenumdisulphide | 5 | | 5 |
| CuO | Copper + oil or grease | 5 | | 5 |
| CuS | Copper + stearate | 5 | | 4 |
|
| Degreasing. The copper surface layer is normally removed by treatment in nitric acid (HNO3) or in sulphuric acid+hydrogen peroxide (H2SO4+H2O2). |
Nonmetallic coating.
The nonmetallic coating on the annealed cold-heading wire in the semifinished condition consists of a chloride-free surface coating. Finer cold-heading wire sizes (<5 mm) are coated continuously in conjunction with the strand annealing operation. Heavier wire sizes are coated in coil form by dipping in a coating tank followed by drying in a drying oven. The nonmetallic coating of the wire consist of a lubricant film formed during the drawing process by a reaction between the surface coating and the lubricant at high pressure and temperature. |
| Name | Surface | Surface properties |
| | Lubrication
efficiency | | Moisture sensitivity. |
| VF | Surface coating on annealed wire | - | | 4 |
| XF | Standard = surface coating + synthetic lubricant | 3 | | 4 |
| XFO | Surface coating + oil/grease | 2 | | 4 |
| XFC | Surface coating + Ca-stearate | 3 | | 2 |
| XFK | Surface coating +Na- + K-stearate | 3 | | 3 |
| XFM | Surface coating + Na -stearate + Mo2S | 4 | | 3 |
|
Degreasing.
The nonmetallic coating can be removed by using an alkaline solvent or nitric acid (HNO3) . |
|
|