Cast High Chrome Balls
High chromium cast grinding balls in grades from Cr12 to Cr26 for abrasive grinding in cement, coal and mineral processing mills Get In ContactNeed grinding media that stands up to abrasive, fine grinding? William Boulton supplies cast high chrome balls for ball mills in cement, coal, power generation and mineral processing. With more than 10% and up to 30% chromium, these balls are full of hard chromium carbides that resist abrasion far better than ordinary steel, so they wear slowly and keep their size and shape for longer.
Our high chrome grades run from Cr12 to Cr26, with lower chrome grades for less demanding duties, so you can choose the balance of wear life, toughness and cost per tonne ground that suits your mill.
Not sure which chrome grade you need? Call our team on 01782 816158 or send us your mill details.
Built for abrasion
Hard chromium carbides held in a hardened martensitic matrix give exceptional resistance to abrasive wear.
Four high chrome grades
Cr12, Cr15, Cr20 and Cr26, so the alloy can be matched to how abrasive your grinding duty is.
Low breakage
Every grade is specified for impact value and drop test performance, with a breakage rate below 1%.
Expert support
Our engineers help you choose the grade, size and charge make-up, and support you once the balls are in your mill.
What are cast high chrome balls?
Cast high chrome balls are grinding balls cast from high chromium iron, an alloy of iron with roughly 2–3.3% carbon and more than 10% chromium. You may also see them called high chrome cast steel balls, high chromium cast iron balls or high chrome white iron balls.
Their wear resistance comes from their microstructure. As the alloy solidifies, chromium and carbon combine to form very hard chromium carbides, known as M7C3 carbides. Heat treatment then turns the surrounding metal into hard martensite, which supports the carbides and holds them in place. The result is a ball that resists abrasive wear much better than forged steel, particularly in fine and dry grinding.
The trade-off is toughness. High chrome balls are harder but more brittle than forged steel, so they work best where abrasion, rather than heavy impact, is what wears your media out.
Where high chrome balls work best
Cement, coal and power generation
High chrome media made its name in cement plants, where dry grinding is highly abrasive and wear rates can be several times lower than with steel balls.
- Finish mills – grinding clinker and gypsum to cement fineness, especially in the fine grinding chamber of two-chamber mills.
- Raw mills – grinding limestone and other raw materials into kiln feed.
- Coal mills – grinding coal for kilns and power stations, where resistance to both wear and corrosion pays off.
- Slag grinding – grinding blast-furnace slag, a highly abrasive material.
Mining and mineral processing
In wet grinding, media is worn by abrasion and corrosion together. High chromium alloys resist both, which is why high chrome balls are widely used in secondary ball mills and regrind mills on ores such as copper, gold, iron, lead–zinc and phosphate.
There can be a metallurgical bonus too. Forged steel corrodes in the mill and releases iron into the slurry, which can coat sulphide minerals and hold back flotation. High chrome media is more electrochemically inert, and plant studies have linked it to cleaner mineral surfaces, lower reagent use and better flotation recoveries. The effect varies from ore to ore, so it is worth testing on yours.
For high-impact duties such as SAG mills, tougher forged steel SAG balls are usually the safer choice.
How cast high chrome balls are made
- Melting – selected steel scrap is melted with chromium and other alloying additions in a medium-frequency electric furnace.
- Alloy control – the melt is micro-alloyed and its composition checked before casting.
- Casting – the metal is poured into ball moulds at a controlled temperature, which helps to minimise sand inclusions, porosity and other casting defects.
- Heat treatment – after cleaning, the balls are quenched and tempered to refine their structure, relieve internal stress and develop hardness and toughness.
- Checking – spectrometric chemistry checks can be carried out before and after melting and on semi-finished and finished balls.
High chrome or forged steel?
- Wear resistance – high chrome usually wins in abrasive, fine and dry grinding, often by a wide margin.
- Toughness – forged steel wins where impacts are heavy, such as SAG mills, large-diameter mills and coarse grinding chambers.
- Corrosion – high chromium alloys corrode far less in wet grinding, which can also benefit flotation.
- Cost – high chrome usually costs more per tonne to buy, but a lower wear rate can mean a lower cost per tonne ground.
Not sure which suits your mill? Compare our forged steel grinding balls, or ask us to help you work out the cost per tonne ground for each.
High chrome grades and technical data
Choose from four high chrome grades. In our range, impact values rise with chromium content, from more than 3.5 J/cm² for Cr12 to more than 7 J/cm² for Cr26, and higher chromium levels also improve corrosion resistance. The right grade depends on how abrasive your material is, how much impact the balls take and whether you grind wet or dry.
High chrome grades at a glance
| Grade | Chromium | Hardness | Impact value | Drop test (cycles) | Breakage rate | Microstructure |
|---|---|---|---|---|---|---|
| Cr12 | >10–14% | >58 HRC | >3.5 J/cm² | ≥12,000 | <1% | Martensite + carbide |
| Cr15 | >14–18% | >58 HRC | >5 J/cm² | ≥12,000 | <1% | Martensite + carbide |
| Cr20 | >18–23% | >58 HRC | >6 J/cm² | ≥12,000 | <1% | Martensite + carbide |
| Cr26 | >23–30% | >58 HRC | >7 J/cm² | ≥12,000 | <1% | Martensite + carbide |
Typical chemical composition (% by mass)
| Grade | C | Si | Mn | Cr | Mo | Cu | Ni | P | S |
|---|---|---|---|---|---|---|---|---|---|
| Cr12 | 2.0–3.3 | ≤1.2 | 0.3–1.5 | >10–14 | 0–3.0 | 0–1.2 | 0–1.5 | ≤0.10 | ≤0.06 |
| Cr15 | 2.0–3.3 | ≤1.2 | 0.3–1.5 | >14–18 | 0–3.0 | 0–1.2 | 0–1.5 | ≤0.10 | ≤0.06 |
| Cr20 | 2.0–3.3 | ≤1.2 | 0.3–1.5 | >18–23 | 0–3.0 | 0–1.2 | 0–1.5 | ≤0.10 | ≤0.06 |
| Cr26 | 2.0–3.3 | ≤1.2 | 0.3–1.5 | >23–30 | 0–3.0 | 0–1.2 | 0–1.5 | ≤0.10 | ≤0.06 |
Size, tolerance and weight guide
| Nominal diameter | Diameter tolerance | Approx. weight per ball | Approx. balls per tonne |
|---|---|---|---|
| 17 mm | ±1 mm | 20 g | 51,100 |
| 20 mm | ±1 mm | 32 g | 31,400 |
| 25 mm | ±1 mm | 62 g | 16,100 |
| 30 mm | +1.5 / −1 mm | 107 g | 9,310 |
| 40 mm | +1.5 / −1 mm | 255 g | 3,930 |
| 50 mm | +1.5 / −1 mm | 497 g | 2,010 |
| 60 mm | +2 / −1 mm | 860 g | 1,160 |
| 70 mm | +2 / −1 mm | 1.36 kg | 733 |
| 80 mm | +2.5 / −1 mm | 2.04 kg | 491 |
| 90 mm | +2.5 / −1 mm | 2.90 kg | 345 |
| 100 mm | +3 / −1 mm | 3.98 kg | 251 |
Weights are calculated for a solid sphere at about 7.6 g/cm³, a typical density for high chromium iron, and are a guide only. Other sizes are available on request.
Lower chrome grades, Cr8, Cr5 and Cr2, are also available for less abrasive duties. See our low, medium and high chrome comparison.
Technical values are typical catalogue data rather than a guaranteed contract specification. Final chemistry, hardness, impact value, tolerances, packing and test documentation are confirmed on the quotation and material certificate for each order.
Choosing the right chrome grade and ball size
There’s no single best grade for every mill. When we recommend one, we look at:
- How abrasive your material is – highly abrasive feeds such as slag and quartz-rich ores favour the higher chrome grades.
- How much impact the balls take – large balls in coarse grinding chambers and big-diameter mills see heavier impacts, so toughness matters more there.
- Wet or dry grinding – wet grinding adds corrosion, where higher chromium levels give extra protection.
- Flotation and downstream chemistry – in sulphide flotation circuits, media choice can affect recovery as well as wear.
- Cost per tonne ground – the best grade gives the lowest total cost, not the lowest price per tonne of balls.
In a two-chamber cement mill, for example, the coarse grinding chamber typically uses larger balls of around 50–90 mm and the fine grinding chamber smaller balls of around 15–50 mm. That fine chamber is where high chrome media’s abrasion resistance usually pays off most. Send us your mill details and we’ll recommend a grade and size distribution.
Have a question? Call us on 01782 816158 or:
Why choose William Boulton for high chrome balls?
William Boulton is a British engineering company based in Stoke-on-Trent, founded in 1852. Alongside our own process machinery, including ball mills, we supply a wide range of grinding media and the practical advice to get the most from it.
- The right grade for the job – we help you choose between high, medium and low chrome grades and forged steel, based on your mill and material.
- Technical support – our engineers support you with charge make-up, replenishment and optimising media consumption.
- Controlled production – controlled melting, casting and heat treatment, with spectrometric chemistry checks, for consistent quality.
- Global delivery – our network supports customers around the world with timely delivery.
- The full grinding media range – from forged steel grinding balls and SAG balls to ceramic grinding balls. View all grinding media.
Cast high chrome ball FAQs
What are high chrome grinding balls?
They are grinding balls cast from high chromium iron, with more than 10% and up to 30% chromium and around 2–3.3% carbon. Hard chromium carbides in a martensitic matrix make them highly resistant to abrasive wear.
What chromium content do I need?
It depends on how abrasive your material is, how much impact the balls take and whether you grind wet or dry. Our high chrome range runs from Cr12, with more than 10–14% chromium, to Cr26, with more than 23–30%. We’ll recommend a grade for your mill.
How hard are cast high chrome balls?
Our high chrome grades, Cr12 to Cr26, are heat treated to a hardness above 58 HRC.
Are high chrome balls better than forged steel balls?
For abrasive, fine and dry grinding they usually last much longer. For high-impact duties such as SAG mills and coarse grinding, tougher forged steel is often the better choice. The best option is the one with the lowest cost per tonne ground in your mill.
Can high chrome balls be used for wet grinding?
Yes. High chromium alloys resist corrosion as well as abrasion, which is why they are widely used in wet ball mills and regrind mills in mining. In sulphide flotation circuits they can also improve pulp chemistry compared with forged steel.
Can I use high chrome balls in a SAG mill?
Generally not. SAG mills subject the balls to very heavy impacts, and the more brittle structure of high chrome balls makes them prone to breaking there. We recommend our forged steel SAG balls instead.
What sizes are available?
We supply high chrome balls in a wide range of diameters for both coarse and fine grinding, including all the common sizes in our size guide above. Contact us for other sizes.
Do you supply high chrome balls outside the UK?
Yes. Our global network supports customers around the world with timely delivery and technical support. Contact us with your location and requirements.