Tungsten Carbide Scrap: Hard and Soft Scrap Types, Cobalt Binder and Recycling Routes

What Is Tungsten Carbide Scrap?

Tungsten carbide scrap is cemented carbide, also called hardmetal, that has reached the end of its use or failed inspection. Cemented carbide is not an alloy in the usual sense. It is a composite of very hard tungsten carbide grains held together by a softer metal binder, almost always cobalt, typically 6–12% of the weight in common grades. Some grades use nickel instead, for corrosion resistance or where a non-magnetic part is needed.

Cutting grades often also contain smaller amounts of titanium, tantalum and niobium carbides, which help at the high temperatures reached in steel cutting. Wear-part and mining grades tend to be straight tungsten carbide with cobalt. Cemented carbide has a density of about 14–15 g/cm³, nearly twice that of steel, and that weight is the first clue anyone in a yard uses.

What Are the Main Carbide Scrap Types?

Carbide scrap is divided first into hard scrap and soft scrap. Hard scrap is solid pieces of cemented carbide; soft scrap is powder, sludge and other fine material. Within each group, buyers separate the material further by shape, coating and contamination.

Where Does Tungsten Carbide Scrap Come from?

Tungsten carbide scrap comes from anywhere carbide tools and wear parts are used up, and from the plants that make them. Each source produces a recognisable mix, which helps a buyer understand a lot before it is weighed.

• Machine shops and tool rooms. Worn and broken inserts, end mills and drills, plus grinding sludge where tools are reground on site. Shops that machine titanium and nickel alloys for aerospace parts use carbide heavily.
• Tool regrinders. Tools that can no longer be resharpened, and the sludge from the regrinding itself.
• Mining, quarrying and drilling. Buttons from rock drill bits, cutting picks and drill inserts, usually still set in steel. Drilling tools from oil and gas work add another stream.
• Wire, tube and can making. Worn drawing dies, punches and rolls.
• Carbide producers. Pressing and sintering rejects, out-of-tolerance blanks and powder residues, often clean and of known grade.

Knowing the source tells you what to look for. Mining scrap brings steel bodies; machine shop scrap brings coatings, high-speed steel look-alikes and sludge; producer scrap is usually the cleanest of all.

Why Does the Cobalt Binder Matter?

The cobalt binder matters for three reasons: it is a second source of value, it decides which recycling route a lot can use, and it gives sorters a useful physical clue.

Cobalt is a costly metal in its own right, used in superalloys, magnets and battery chemicals, and recyclers recover it alongside the tungsten. A lot of high-cobalt mining and wear grades carries more of it than a lot of fine-grained cutting inserts. Binder content also changes the chemistry of recycling. The zinc process works by attacking the cobalt, so it depends on a metallic binder being present and reasonably consistent across the lot. Nickel-bound grades behave differently, which is why they are better kept apart.

Finally, cobalt makes most cemented carbide weakly magnetic. That does not separate carbide from steel, which is strongly magnetic, but it does help pick out ceramic and some cermet pieces, which are not. The magnet test article explains why a magnet is a first sort and not an identification. Cobalt as a metal in its own right is covered under cobalt metal scrap.

How Is Tungsten Carbide Scrap Recycled?

Tungsten carbide scrap is recycled in two main ways. Direct routes, of which the zinc process is the best known, break the carbide down while keeping the tungsten carbide and cobalt together. Chemical routes dissolve the scrap back to tungsten compounds and build new powder from scratch.

The Zinc Process

In the zinc process, clean hard scrap is placed in contact with molten zinc. Zinc reacts with the cobalt binder, the reaction products take up more volume than the cobalt did, and the carbide structure swells and breaks apart. The zinc is then removed by vacuum distillation and recovered for reuse, leaving a friable cake of tungsten carbide and cobalt that is crushed and milled into powder. Because the carbide and binder stay together, the product closely reflects the chemistry of the scrap that went in. That is why the route needs sorted, clean and grade-consistent feed.

Chemical Recovery

In chemical recovery, the scrap is oxidised and then leached, usually with an alkali, so the tungsten goes into solution as a tungstate. The solution is purified and turned into ammonium paratungstate (APT), the standard intermediate from which tungsten oxide, tungsten powder and new tungsten carbide are made. Cobalt is recovered separately. This route accepts almost anything that contains tungsten, including oxidised, coated, mixed and very fine material, at the cost of more energy and chemical processing.

Mechanical and Direct Reuse

Some carbide is crushed mechanically into coarse powder for uses such as hardfacing, and some worn tools are simply reground or rebuilt. These routes suit specific, clean material.

For a seller, the practical lesson is that clean, sorted hard scrap has more possible outlets than mixed material. The more of the sorting work you do, the more buyers can use your lot.

How Should Carbide Scrap Be Sorted and Prepared?

Sort carbide scrap by type, keep anything that is not carbide out of the bin, and keep soft scrap dry and separate. A buyer pays for carbide and deducts for steel, braze, oil, water and look-alike materials.

Density is the fastest check. A carbide end mill feels startlingly heavy next to a high-speed steel one of the same size. XRF then confirms tungsten and shows whether the binder is cobalt or nickel, and whether titanium or tantalum carbides are present. The guide to handheld XRF sorting covers how readings are taken on small pieces.

Carbide also needs to be kept out of other metals. Fragments of carbide tools in titanium turnings form dense inclusions when the titanium is remelted, which is why titanium buyers reject contaminated lots; see selling titanium scrap. The same applies to nickel alloy turnings, where carbide is unwelcome in a remelt, as described in how superalloy revert returns to the melt.

What Sets the Carbide Scrap Price per Kg?

The carbide scrap price per kg is set by how much tungsten and cobalt a lot contains, how cleanly it can be recycled, and the market for tungsten and cobalt at the time. No figure is given here, because it would date quickly and every lot is different.

• Hard or soft. Solid carbide carries far more tungsten per kilogram than sludge diluted with abrasive, coolant and steel fines, so hard scrap is valued well above soft scrap.
• Cobalt content. Higher-cobalt grades carry more of the second paying metal.
• Contamination. Steel shanks, braze, coatings, oil and water are weight the buyer does not want and has to remove.
• Sorting. A lot of one type, such as clean round tools, can go to more routes than a mixed drum.
• Quantity and market. The tungsten market, which is commonly referenced to APT, and the cobalt market move every offer.

The contained metal calculator shows how weight and content combine into contained tungsten and cobalt.

What Should You Send a Tungsten Carbide Scrap Buyer?

Send a tungsten carbide scrap buyer a description by type, an approximate weight for each type, photographs, and any readings you have. "Solid carbide end mills and drills, uncoated and coated mixed, about 200 kg, no HSS, readings on 10 pieces" gets a firmer response than "carbide scrap, mixed".

• Types and weights: solid round tools, inserts, buttons, wear parts, brazed tools and soft scrap listed separately.
• Binder: cobalt or nickel, if readings show it.
• Condition: coatings, attached steel, oil or moisture.
• For soft scrap: moisture and an analysis of tungsten and cobalt, because content varies widely.
• Location and whether the material will be exported, with the HS subheading 8101.97 for tungsten waste and scrap.

Mipra Steel, based in Mumbai, buys and supplies tungsten carbide scrap and other tungsten materials described by type and grade, and handles import and export enquiries. Related materials are on the pure tungsten scrap and ferro tungsten scrap pages, and the ferro tungsten guide explains why those three tungsten materials are kept apart. Paperwork for shipments is covered in documents for exporting alloy scrap. Send the details and we'll review your enquiry.

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