Tungsten Carbide Soft Scrap Specification — Powder, Grinding Sludge and Swarf

In the hardmetal trade, hard scrap means sintered solid carbide components and soft scrap means everything tungsten-bearing that is not sintered solid: pressed but unsintered green compacts, spray-dried and ready-to-press powder, reclaim powder, grinding sludge, swarf and the fine residues collected from finishing operations. The distinction is fundamental. Hard scrap is a solid, dry, dense, stable article; soft scrap is a fine or semi-liquid material whose tungsten is dispersed through a matrix of coolant, abrasive and metallic fines.

Soft scrap is generated mainly inside the hardmetal industry itself and in the shops that grind it. Carbide manufacturers produce powder and green-state rejects; tool grinding and regrinding operations produce sludge and swarf as the wheel removes carbide from the workpiece; finishing and polishing produce fines. Because grinding removes material from both the carbide and the wheel, sludge always contains abrasive as well as carbide.

The processing route also differs. Solid carbide can be recovered through routes that exploit its integrity as a sintered article; fine and wet material generally requires chemical or hydrometallurgical treatment, and its value depends on the concentration of recoverable tungsten in the dry mass rather than on the appearance of the material. This is why the commercial questions asked about soft scrap — moisture, dry weight, abrasive load, oil content — are almost entirely different from those asked about hard scrap.

One consequence deserves emphasis at the outset: no meaningful commercial assessment of soft scrap can be made from photographs alone. Two visually identical drums of grey sludge can differ substantially in dry tungsten-bearing content. Assessment requires sampling.

Soft scrap presentations vary from free-flowing dry powder to saturated paste, and the presentation drives everything about handling:

Soft scrap is identified by physical state and by origin rather than by piece recognition. The most useful single indicator is unexpected weight: tungsten-bearing powder and sludge are far heavier than their volume suggests, and a small pail that is hard to lift is a stronger indicator of tungsten content than colour, which is grey across almost all grinding residues regardless of what was ground.

Establishing origin is therefore central. Sludge from a shop that grinds only carbide is a very different material from sludge from a shop that grinds carbide and high speed steel on the same machines, where the residue is a blend of carbide fines and steel fines. Where mixed grinding occurs, the material should be described as such rather than as carbide sludge.

The other identification task is separating the tungsten-bearing fraction from what surrounds it. Grinding wheel abrasive, wheel bond material, coolant, oil and water all form part of the delivered mass. A simple drying and settling check on a sample gives a far better picture than any visual assessment of the drum.

Evaluation of soft scrap turns on the dry, tungsten-bearing fraction and on how difficult the surrounding matrix makes recovery. The factors below are the ones that actually move a discussion:

In soft scrap the boundary between contamination and matrix is blurred: coolant and abrasive are not accidental additions, they are inherent to how the material is generated. What matters commercially is how much of the delivered weight is not recoverable tungsten-bearing solid, and how that is established.

Soft scrap packaging has to solve two problems that hard scrap does not: containment of a fine or wet material, and prevention of leakage in transit. Sealed, sound packaging is not a presentation preference here — a leaking drum of wet sludge is a transport and yard problem before it is a commercial one.

Segregation should follow generation. Powder, dry swarf and wet sludge behave differently in processing, and lots that combine them in the same package are harder to sample and harder to value than lots kept apart at source.

Fine and wet materials attract more transport scrutiny than solid articles. Packaging integrity, containment of free liquid and correct description of the material are the practical requirements, and container plans must account for the fact that a small number of drums reaches payload limits.

As-received weight and dry weight can differ materially for wet sludge. Which basis governs the transaction, when it is determined and by whom must be settled in the contract rather than assumed.

Import controls for powders, sludges and residues are frequently stricter than for solid scrap of the same metal family, and they differ by destination. These requirements must be confirmed per shipment by the importer before contracting.

Soft scrap is the stream where handheld surface screening is least informative and formal sampling most important. XRF pointed at a heap of wet sludge reads the surface of whatever is presented at that spot — an abrasive-rich crust, a wet skin, or a locally concentrated pocket — and no such reading represents the drum, let alone the lot.

A workable approach is incremental sampling across drums and depths, combining increments into a composite, and determining moisture by drying before any elemental figure is discussed. Elements commonly of interest are tungsten and cobalt for the recoverable fraction, iron for steel fines from mixed grinding, and nickel and chromium where nickel-bound grades or alloy steels are involved.

Nautica does not operate its own laboratory. Where analysis is required, it is performed by a laboratory or inspection company the parties appoint and agree in the contract.

Powders, sludges and residues are frequently described and controlled differently from solid metal scrap. Classification depends on the actual composition, the physical form as shipped, the moisture and matrix content, the destination country and the interpretation of the competent customs authority there.

Some destinations apply additional import controls, prior notification requirements or restrictions to fine and wet residues that do not apply to solid scrap of the same metal family.

Nautica does not assign a definitive tariff code for soft scrap in advance. Importers must confirm the applicable classification and any import permit, notification or waste-shipment obligation with their customs broker or the competent authority before contracting.