A 200 HB manganese liner can outlast a 60 HRC high-chrome part in coarse crushing, then lose to it in fine abrasion. Both readings are correct. Hardness answers a narrower question than wear life.
This guide to crusher wear part hardness testing explains those results: the scale, the test location, and what the number says about manganese, high-chrome and martensitic grades.
A Hardness Number Is a Test Result, Not a Ranking
Hardness measures resistance to an indenter. Wear resistance depends on the abrasive, contact pressure, impact angle, particle shape, toughness and surface deformation.
A 60 HRC high-chrome bar may chip in a high-impact rotor where a 200 HB manganese bar work-hardens and holds shape. In low-impact fine abrasion, the high-chrome bar may run longer because its carbides resist scratching.
Compare heats within one family, in the same condition and test location. Do not rank manganese against white iron.
The Scales You Will See on a Casting Report
HB uses a ball indentation. The larger indent averages a coarse structure, which suits manganese and heavy sections; very hard white iron can deform the ball.
HRC uses a diamond cone. It suits high-chrome and martensitic parts, but is less reliable above about 60 HRC or on a thin case. Take several readings.
HV uses a diamond pyramid at low load. It maps carbides and case depth; it is not a bulk acceptance test.
Conversions are approximate. If the drawing calls for HB, ask for HB.
Typical Hardness and Toughness by Material Family
These are broad ranges, not a specification. Chemistry, section size, heat treatment and test location move them.
| Family and typical composition | Hardness as supplied and in service | Typical notched-bar toughness at room temperature |
|---|---|---|
| Mn13, about 1.0-1.4% C and 11-14% Mn | About 170-230 HB; work-hardens to roughly 350-500 HB | High, often above 100 J |
| Mn18, about 1.1-1.4% C and 17-19% Mn | About 170-230 HB; work-hardens to roughly 350-500 HB | High, often above 100 J |
| Mn22, about 1.1-1.4% C and 21-24% Mn | About 170-230 HB; work-hardens to roughly 350-500 HB | Very high, often above 100 J |
| High-chrome iron, about 2-4% C and 12-28% Cr | About 55-65 HRC; little change in service | Low, often below 20 J |
| Martensitic steel, about 0.2-0.5% C with Cr and Mo | About 35-50 HRC; tempering and service can soften it | Moderate, often tens of joules |
The ranges are wide because the families are wide. More carbon and a different carbide network can push high-chrome iron to the top of the hardness range and the bottom of the toughness range. Broadly, manganese grades suit impact, high-chrome suits low-impact abrasion, and martensitic grades suit mixed duty.
Why Manganese Reports Look Soft
Austenitic manganese steel arrives at roughly 170-230 HB. That is the starting condition, not a defect. Under impact and compression the surface work-hardens to roughly 350-500 HB while the core stays tough.
An incoming hardness test is therefore a poor predictor of wear life. A part that never sees enough impact may not harden, and smooth abrasive duty can wear it faster than a harder material. The crusher wear parts materials guide covers selection; the report confirms the condition supplied.
Mn13, Mn18 and Mn22 are not a hardness ladder. Higher manganese generally improves toughness and austenite stability, not the as-supplied number. Choose by impact severity, section size and cracking history.
Impact Toughness: The Number That Predicts Breakage
The notched-bar impact test, usually reported as Charpy V-notch energy in joules, measures energy absorbed before fracture. A wear part needs enough toughness for tramp metal, oversize feed, start-up shocks and the impact angle of the duty.
Austenitic manganese absorbs a large amount of energy and retains much of that toughness at low temperature. High-chrome iron is hard but brittle by contrast. Martensitic steel sits between, and the result depends on tempering.
Read the test conditions:
- Specimen and notch. A standard specimen has a defined size and notch.
- Temperature. Room-temperature toughness does not describe a cold plant; martensitic grades can lose toughness as temperature falls.
- Location. A cast-on coupon, a separately cast bar and a specimen cut from the part can differ.
- Scatter. Ask for the number of tests, the average and the lowest value.
High hardness with low impact is a warning. In a primary crusher it often shows up as a cracked liner rather than a worn one.
Where the Test Is Taken, and How to Read the Report
Hardness is not uniform through a casting. A high-chrome part can have a hard skin and a different core; a thick manganese section can cool more slowly. A portable tester on a curved, work-hardened face is not a laboratory test on a prepared coupon.
| Test location | What it shows | Common trap |
|---|---|---|
| Cast surface | Skin condition, chill effect, local carbides | A hard skin is not bulk hardness |
| Mid-section | Bulk hardness | Large sections can be softer or segregated |
| Cast-on coupon | Same heat and heat treatment as the casting | It must be attached and treated with the part |
| Separately cast coupon | Process control for the heat | It cools differently and may not represent a heavy section |
| Worn surface | The work-hardened layer in service | Curvature and preparation affect the reading |
For a large liner, ask for a traverse from surface to core with locations marked. A single value can hide a soft centre or an over-hardened edge.
A useful report states the scale and load, test location, number of readings, supplied condition, specimen source and any conversion. Our crusher parts quality documents checklist lists the wider set for a first article.
Matching the Number to the Operating Condition
Hardness becomes useful when read against the duty. The same alloy can be right in one position and wrong in the next.
| Duty | Dominant wear | Role of hardness | Role of toughness | Typical starting family |
|---|---|---|---|---|
| Primary jaw, hard abrasive rock, large feed | Impact plus abrasion | Incoming hardness matters less than work hardening | Must survive oversize and tramp metal | Mn18 or Mn22 |
| Cone secondary or tertiary, abrasive rock | Abrasion with moderate impact | A harder grade may help if impact is low | Avoid a brittle grade under shock loads | Mn18, or high-chrome where impact is low |
| HSI in concrete or asphalt recycling | Impact plus abrasion | Supports wear life | Critical: rebar and unbreakable material cause breakage | Martensitic or manganese |
| HSI in abrasive limestone, low impact | Abrasion | High hardness is useful | Lower impact demand, but start-up shocks remain | High-chrome |
| VSI in manufactured sand | High-speed abrasion | Carbide volume and hardness matter | Moderate, but rotor balance and fit still matter | High-chrome or a composite part |
The HSI blow bar range shows the point: one rotor can need a different bar material when feed changes from limestone to demolition concrete. Feed size, moisture, closed-side setting, throughput and tramp-metal history change the wear mode more than a few points of hardness.
Hardness Is Not a Substitute for a Wear Trial
A test report tells you what the supplier made; a wear trial tells you what the duty does. Run a controlled trial on one position: record part identity, tonnage or hours, feed, wear profile and failure mode. That record gives the next quote a real basis and shows whether the problem is wear, fracture or fit.
FAQ
Why does a manganese liner show only about 200 HB if it wears well?
That is the as-supplied condition. The surface work-hardens to roughly 350-500 HB under impact while the core stays tough.
Is a higher HRC always better for a crusher wear part?
No. Higher hardness usually means lower toughness, and a brittle part can fail before it wears. Match the balance to impact severity and feed size within a family.
Can I convert HB to HRC and compare the numbers directly?
Only as a rough indication. Conversions are approximate and depend on material and test conditions. A converted number is not a measurement.
Where should hardness be measured on a large liner?
At marked positions from surface to core, on a prepared surface. A cast-on coupon from the same heat and heat treatment helps; one reading on a curved face is not enough.
What impact toughness should I specify?
There is no universal value. State the duty, minimum energy at the service temperature, specimen type and test location, and ask for both average and lowest results.
Request a Quote for Crusher Wear Part Castings
Send your drawing, crusher position, feed conditions, current wear life and any hardness or impact requirements through our contact page to request a quotation. We will review the material and test requirements against the duty before quoting.
