Choosing Manganese Content in Hadfield Steel: Where Mn13, Mn18 and Chromium Fit

The wear resistance of Hadfield manganese steel does not come from its initial hardness but from work hardening in service. That means higher manganese is not automatically better — what matters is whether impact energy is sufficient. After 40 years of selection experience since the 1980s at Grand Heavy, the Mn13 versus Mn18 question is not about which is more wear resistant, but which one the duty can actually work-harden. This guide sets out the relationships between manganese, carbon, chromium and impact energy, with a selection table by hardness band.

图：大美智造圆锥破耐磨件实物——每批随附材质成分单与热处理过程记录，可按工况匹配材质

I. Work Hardening: the Basis for Understanding Manganese Content

The wear resistance of Hadfield steel does not come from the hardness as supplied, but from work hardening triggered by impact loading in service. Understanding this is what makes sense of why higher manganese is not automatically better.

• Initial state: after water toughening the matrix is single phase austenite with an initial hardness of about HB200, which offers little wear resistance;
• Under load: severe impact or high pressure causes plastic deformation at the surface, generating dense dislocations and deformation twins, raising hardness above HB500;
• Structure achieved: a hard outside, tough inside configuration — the hardened surface resists abrasion while the core keeps its toughness, so even a thin worn part still carries load without breaking;
• Key consequence: the depth and hardness of the work-hardened layer determine wear resistance. Whether it forms, and how deep it goes, depends on whether impact energy is sufficient.

Chemical composition of Mn13 and Mn18

The role of chromium: adding chromium improves hardenability and wear resistance and compensates for the weakness of conventional Hadfield steel in pure abrasion duty where impact is insufficient. That is why Mn13Cr2 and Mn18Cr2 are often used in the intermediate band — abrasion is real but impact is not strong.

Two limits on manganese and carbon

• Lower manganese limit: below roughly 11 percent Mn, a stable austenitic matrix cannot form, work hardening is not triggered properly under impact and wear resistance falls clearly;
• Upper carbon limit: above roughly 1.4 percent C, network carbides precipitate. Hardness rises but the matrix becomes brittle, so the part tends to chip and spall in service, shortening life;
• Interaction: carbon and manganese together govern work hardening. Research indicates that raising carbon and lowering manganese can improve work hardening in austenitic manganese steels, and in non-severe impact duty a high carbon medium manganese steel may outperform conventional Hadfield steel. Mn18 therefore relies on the overall alloy design, not on the manganese number alone.

II. Impact Energy: the Variable That Decides Mn13 versus Mn18

Impact abrasion wear testing points to one consistent conclusion: the higher the impact energy, the clearer the advantage of Mn18.

• At low impact energy: Mn18 still outperforms Mn13, with surface hardness rising slowly over time;
• At higher impact energy: the advantage widens and surface hardness can reach about HB440 quickly, meaning Mn18 completes surface hardening sooner and sustains a thicker hardened layer;
• Hardened layer depth: under the same impact conditions Mn18 develops a deeper hardened layer and clearly better wear resistance, which matters for high impact frequency duties such as large cone crushers on hard rock;
• The reverse conclusion: in low impact, cutting and rubbing dominated duty (for example crushing limestone) impact energy is insufficient, so Mn13 and Mn18 perform similarly and neither reaches its potential — paying extra for Mn18 buys little.

Impact energy is not an abstract concept: it relates directly to lump size, crusher speed and discharge setting. Crushing large hard rock at high speed gives high impact energy and Mn18 can deliver; with an even feed and steady operation, Mn13 may be the better value.

Note: the comparative figures above come from published industry impact abrasion wear testing and are used to show the trend. For the difference under your own duty, a side-by-side comparison test is the reliable basis.

图：金相试样与硬度打点对比——高锰钢耐磨性来自加工硬化，硬化层深度取决于冲击功是否足够

III. A Field Lesson: Mn18 on Medium Hardness Duty Cost More per Tonne

A quarry crushing medium hardness sandstone bought Mn18Cr2 bowl liners on the reasoning that a higher grade must wear longer and is worth the extra cost.

In practice, the unit price was much higher but the life gain was limited, so the cost per tonne was worse than the original Mn13 solution. The plant could not understand why the better material did not pay.

We ran three checks:

• 1. Impact energy level: the line had a fairly even feed and steady chamber operation, so it was a medium impact duty, outside the band where Mn18 excels;
• 2. Material hardness: sandstone is medium hardness (about Mohs 4 to 6), where Mn13 already work-hardens reliably and offers good value;
• 3. Cost per tonne: Mn18Cr2 costs noticeably more, and the life gain was not enough to offset it — on cost per tonne, Mn13 was better.

The upgrade did not add up on that line. We recommended returning to Mn13 (with Mn13Cr2 where lump size and impact are higher) and putting the saved budget into improving feed evenness and optimising spare parts inventory.

Almost simultaneously, a granite line we serve showed the opposite: it had used Mn13 and the liners wore quickly with localised spalling; switching to Mn18Cr2 gave a deeper hardened layer, clearly longer life and a lower cost per tonne — that upgrade did pay.

The difference between the two lines was not material quality but whether impact energy and material hardness fell inside the band where Mn18 excels. The rule: choose manganese content by impact energy and material hardness first, price second; Hadfield steel is not a case of more expensive being better, it must match the impact energy.

IV. Manganese Selection Table by Hardness Band (Save This)

Four questions to answer before selecting

Related reading: GB/T 5680 explained, cone crusher liner material selection, the liner material decision matrix, granite crushing wear parts and titanium carbide liner metallurgy.

V. Insider Gotchas

• Believing higher manganese means more wear resistance: the most common misconception. Hadfield steel wears well through work hardening, and Mn18 needs sufficient impact energy to deliver; at low impact the two grades differ little;
• Ignoring the carbon limit: above about 1.4 percent C, network carbides precipitate. Hardness rises but brittleness rises too, so parts chip and spall;
• Using Hadfield steel on low hardness material: without enough impact the steel does not work-harden, and high chrome cast iron may be better;
• Judging by grade and ignoring heat treatment: inadequate water toughening (too fast a heating rate, insufficient holding, slow quenching) destroys the single phase austenitic structure and sharply reduces work hardening — a compliant chemistry is not enough;
• Judging an upgrade by the life multiple: the correct criterion is cost per tonne. On medium hardness, medium impact duty the life gain from Mn18 often does not offset the price difference;
• Ignoring uneven wear from feed segregation: uneven feed accelerates local wear, so even a correct grade can wear unevenly — a duty problem is not solved by changing material;
• Assuming the same grade performs the same everywhere: melting cleanliness, heat treatment parameters and foundry process cause noticeable life differences for the same grade, so supplier batch consistency matters as much as the grade itself.

VI. When Mn18 Is Not the Right Choice

• Medium to low hardness material at medium impact: Mn13 already work-hardens reliably, so the Mn18 upgrade usually does not add up;
• Low hardness, cutting and rubbing dominated duty: impact is insufficient, Mn13 and Mn18 differ little, and another material such as high chrome cast iron should be considered;
• Even feed with steady operation: impact energy is low, so the deeper hardened layer of Mn18 cannot be exploited;
• Wear dominated by chipping and spalling: check carbide precipitation and heat treatment quality rather than simply raising manganese;
• Untreated feed conditions (segregation, oversize, failed metal removal): unresolved duty cancels any benefit from a material upgrade.

Three actions: 1. Judge the hardness band and impact energy first and use the table to set the material direction; 2. Use cost per tonne to decide whether an upgrade pays, not the life multiple; 3. Confirm the supplier can provide material certificates and heat treatment process records so water toughening quality is traceable.

FAQ

• Q: Is higher manganese in Hadfield steel more wear resistant? A: No. Wear resistance comes from work hardening in service, and Mn18 needs sufficient impact energy to deliver. At low impact, or medium hardness with medium impact, the two grades differ little while Mn18 costs clearly more, so the cost per tonne may be worse.
• Q: What is the main difference between Mn13 and Mn18? A: In composition, Mn13 contains about 11 to 14 percent Mn (the typical grade in the ZGMn13 series of GB/T 5680) while Mn18 contains about 17 to 19 percent Mn and in industrial use usually adds about 1.5 to 2.5 percent chromium as Mn18Cr2. In performance, Mn18 develops a deeper hardened layer and wears better under high impact; at low impact the advantage is not evident.
• Q: Why is impact energy the key selection variable? A: Because work hardening must be triggered by impact loading. Impact energy relates directly to lump size, crusher speed and discharge setting. Large hard rock at high speed gives high impact energy and Mn18 can deliver; an even feed with steady operation gives low impact energy and Mn13 is better value.
• Q: How does carbon affect Hadfield steel? A: Carbon and manganese together govern work hardening. Above roughly 1.4 percent C, network carbides precipitate. Hardness rises but the matrix becomes brittle and the part tends to chip and spall, shortening life.
• Q: What does chromium do? A: Chromium improves hardenability and wear resistance and compensates for the weakness of conventional Hadfield steel in pure abrasion duty where impact is insufficient. That is why Mn13Cr2 and Mn18Cr2 suit the intermediate band where abrasion is real but impact is not strong.
• Q: What material suits low hardness material such as limestone? A: For limestone, gypsum and other material below about Mohs 4, crushing is dominated by cutting and rubbing, so impact energy is insufficient and Hadfield steel does not work-harden properly. Neither Mn13 nor Mn18 reaches its potential — high chrome cast iron or another wear alloy may be more suitable.
• Q: What quality assurance can Grand Heavy provide? A: Grand Heavy ships material certificates and heat treatment process records with each batch, provides test reports as agreed in the technical agreement, and supports side-by-side testing and failure analysis to confirm whether the material matches the duty. See also the liner material decision matrix.

VII. Final Verdict

Manganese content selection in Hadfield steel comes down to one phrase: not higher is better, but matching the impact energy. Three disciplines: 1. judge the hardness band and impact energy first, then choose the grade; 2. use cost per tonne to decide whether an upgrade pays, not the life multiple; 3. keep carbon below about 1.4 percent, manganese above about 11 percent, and make water toughening quality traceable. Mn18 has a real advantage in high impact hard rock duty, but applying it to medium hardness steady duty only raises cost with limited benefit. Foshan Grand Heavy Trading Co., Ltd. has built mining equipment and wear casting expertise for 40+ years, holds 20+ patents, partners with Central South University and Guangdong University of Technology, and is certified as a National High-Tech Enterprise [To be added: certificate number]. We serve CNBM, Conch Cement and clients across 6 overseas markets with 24-hour response from Guangzhou, Foshan and Changsha. Send us your material, lump size and equipment parameters and we will advise whether Mn13 or Mn18 fits.

Grand Heavy — Higher manganese is not better; it must match the impact energy!