Cold finished peeled and center-less ground bars

EFFICIENT CONVERSION FROM HOT ROLLED
Even if hot-rolled bars are manufactured to tight tolerances with a minimum of surface defects, the presence of mill scale detracts from appearance and can negatively affect certain mechanical characteristics such as bending fatigue. For this reason, many components manufactured from hot-finished round bar require extensive machining in order to improve surface finishing. Regardless of the final application, the distinctive features of the cold finished bars are tight tolerances and excellent surface finish; this means that your expensive machine fleet and qualified personnel can focus on precision machining or cold forming operations that are needed to transform bars into finished products; unqualified rough-machining steps are no longer necessary.

Since cold-finished bars are dimensionally much closer to the final product, less material needs to be purchased per component, often 10% less; simply put, the hot-rolled oversize stays at the steel mill.

Peeled bars: Qualisteel’s peeled bar (ABS Group) are roll straightened directly after the peeling operation, which, in addition to trimming of straightness, burnishes the bar surface and flattens asperities. This greatly improves surface smoothness so that the bars attain a polished appearance. Furthermore, the cold deformation of the extreme outer surface generates compressive residual stresses, which will be favorable for fatigue resistance in bending. Peeled bars from Qualisteel can in many cases be used directly as shafts and axles without any further processing. Double inspection (eddy current plus ultrasonic control prior and after peeling and reel straightening) plus careful dimensional control ensure a peeled bar with outstanding quality.

- Diameter range (Ø): 30 – 160 mm.
- Diameter tolerance: IT11 or upon request IT10 or IT9.
- Surface finish (Ra): Ra ≤ 1.0 μm.
- Ovality: max 50% of the diameter tolerance range, measured as the difference in diameter.
- Straightness: two levels are available as standard: <1.0 and <0.5 mm/m. Bars with better straightness can be supplied upon request.- Bar lengths (L): optional in the range 3 – 12 m. Length tolerance +100/-0 mm. Shorter lengths with tighter tolerances can be offered via saw cutting.
- Bar ends: standard mill ends are cut with abrasive disc. Cold-sawn ends can be supplied upon request.
- Chamfering: (one or both ends) available for bar diameters less or equal than 120 mm, with angles 30, 45 or 60°(α) and chamfered length between 1-5 mm (b) as required.
- Packing: bundled using steel bands with strips of reinforced paper under the bands. Each bundle is wrapped in plastic-coated paper for extra protection during transport. Other types of packaging and protection are possible.
- Identification: plastic tag on each bundle with information on order number, customer name, grade and condition, heat number, dimension, weight and number of bars.

Center-less ground bars: purchase of finished center-less ground bars is often a more convenient alternative to in-house grinding. An essential requirement for the manufacture of high quality ground bars is a excellent starting material with good dimensional tolerance, straightness and peeling. The result is a center-less ground product with close tolerances, excellent straightness, minimal out of roundness and fine surface. As it has already been pointed out, ground bars from Qualisteel are characterized by very low levels of residual stress which reduces the distortion risk in subsequent machining operations.

Center-less ground bars from Qualisteel are available in two types, rough ground and fine ground. Rough-ground bars are an excellent starting material for further processing, e.g. cold forming, or fine grinding and chrome plating. Fine-ground bars are used in applications with high demands on economy of manufacture and service performance (axles, drive shafts, bearing elements and other qualified machine components).