Product Specification

Surface Defects on Stainless Wire: Naming Them and Setting Limits

Surface quality is one of the few wire properties still agreed in words rather than numbers. That is where most disputes come from: two parties say "good surface" and mean two different things, and the argument only starts after the wire is on the machine.

This wire is supplied from 0.15 mm to 12 mm, annealed at 550-750 N/mm2, bright annealed, bright drawn or soap-coated. Where surface matters, a reference sample and a written limit are agreed before production, because a defect that is invisible in one lighting condition is obvious in another.

Four defect types account for most claims, and they do not have the same consequence. Knowing which one is in front of you decides whether it matters.

Product Specifications

The Four Defects That Matter

Die lines

Longitudinal marks that follow the drawing direction, caused by a worn or damaged die or by built-up metal in the bearing zone. They are continuous or repeated at a fixed interval, which is what distinguishes them from handling damage.

Scratches

Marks at an angle to the axis, from guides, capstans or handling. A scratch removes metal and leaves a sharp-edged groove; its direction and randomness are the clue that the cause is downstream of the die, not the die itself.

Slivers and rolled-in metal

Thin flaps of metal rolled into the surface, or fragments of built-up edge pressed in during drawing. A sliver is a lap, not a groove, and it behaves as a crack starter because it has a re-entrant edge.

Stain and heat tint

Discolouration from the annealing atmosphere or from inadequate pickling. On bright annealed supply it is a process signal, and on any part that will be visible it is a rejection at sight, even where the mechanical properties are unaffected.

What Each One Does in Service

Forming and cracking

On a bent part the outside of the bend is in tension. A die line or sliver on that face concentrates stress and becomes the fracture origin, while the same defect on a straight, statically loaded part is harmless.

Corrosion

A groove or lap holds residue and shields it from the cleaning agent, and it interrupts the passive layer. On a washdown part, a scratch on the product-contact face is a corrosion site before it is a cosmetic issue.

Appearance

On visible parts the finish is the specification. Bright annealed wire with a straw tint will be rejected by the end user even if every mechanical figure is inside the band.

Setting a Limit That Can Be Inspected

A reference sample first

Agree a physical sample that represents acceptable supply, signed by both sides. Words like "minor" and "slight" only become useful once there is a sample next to them.

Count, length and depth

A limit that can be checked has three parts: how many defects per metre, how long each may be, and how deep. Even an approximate depth limit is better than no depth limit, because a shallow mark and a lap are not equivalent.

Lighting and viewing method

The same mark reads differently under directional light and under diffuse light. Fixing the lamp type, the distance and whether the wire is rotated gives two inspectors a chance of reaching the same verdict.

Applications

Visible frames and grilles

Bright annealed or polished wire in 2-8 mm where the surface is the product, and a tint or line is a rejection.

Woven mesh and filter cloth

Fine wire where a defect crosses the aperture or becomes a fault line in the woven panel.

Formed and cycled parts

Parts bent or flexed in service, where the defect sits on the tension face and decides fatigue life rather than appearance.

Product Advantages

• Defects named, not implied - die lines, scratches, slivers and tint are separated, because they have different causes and different consequences.
• Reference sample agreed - a physical standard both sides have signed, so "good surface" has a definition.
• Limits in three parts - count per metre, length and depth, instead of a single adjective.
• Inspection method stated - lighting and viewing method are fixed, since they change what is visible.
• Bright or coated supply - bright annealed for visible parts, soap-coated where the wire passes through guides.
• Traceable lots - heat number on every coil label, with surface condition recorded before packing.

Quality Control

Rod grade is verified before drawing. Die condition is checked on a fixed interval, diameter is measured inline, and surface is inspected against the reference sample before packing. Heat tint and stain are checked after annealing, and coil build is verified so that handling damage is not introduced at the last step.

Selection and Ordering Notes

1. State whether the surface is visible, functional, or on a tension face in a cycled part.
2. Agree a reference sample and attach it to the order.
3. Give the limit as count per metre, length and depth where the defect matters.
4. Name the finish: bright annealed, bright drawn, or soap-coated.
5. Provide sizes and annual volume for a tolerance and packing review.

Send the diameter, finish, visible or functional requirement and any surface limit for technical confirmation and quotation.