How much does the manganese content (such as Mn13, Mn18) in the rolling mill wall material affect the wear resistance? How to choose when crushing materials of different hardness?

In the material selection of the cone crusher bowl wall, high manganese steel dominates due to its unique work hardening characteristics. Among them, traditional high manganese steel represented by Mn13 (manganese content of 11% to 14%) and ultra-high manganese steel represented by Mn18 (manganese content of 17% to 19%) are two widely used types. The difference in manganese content directly affects the work hardening ability, surface hardness, and impact toughness of materials, thereby determining their wear resistance performance when dealing with materials of different hardness.

1、 Work hardening mechanism: the core of wear resistance of high manganese steel

The wear resistance of high manganese steel does not come from the initial hardness of the material, but from the work hardening phenomenon triggered by impact loads during its service. The high manganese steel matrix after water toughening treatment has a single austenite structure with an initial hardness of about HB200, and does not have significant wear resistance. When subjected to severe impact or high pressure compression, plastic deformation occurs on the surface, resulting in high-density dislocations and deformation twinning in the microstructure. The hardness can be increased to HB500 or above, while the inner layer maintains excellent toughness, forming a "hard on the outside and tough on the inside" structure. This characteristic enables high manganese steel to withstand large impact loads without breaking, and even if worn to a very thin thickness, it can still maintain sufficient load-bearing capacity.

The level of work hardening ability directly determines whether high manganese steel can form a sufficiently thick hardening layer during use. If the depth of the hardened layer is insufficient and the surface hardness does not reach the expected value, the wear resistance will significantly decrease.

2、 Comparison of Wear Resistance between Mn13 and Mn18

1. Basic differences in chemical composition

Mn13 and Mn18 belong to the category of austenitic high manganese steel, with the core difference being the manganese content. The manganese content of Mn13 is usually controlled at 11% to 14%, and the carbon content is 0.9% to 1.35%. It is a typical grade of ZGMn13 series in GB/T 5680 standard. Mn18 belongs to ultra-high manganese steel with a manganese content of 17% to 19%. In most industrial applications, 1.5% to 2.5% chromium element is added in the form of Mn18Cr2 to improve hardenability and wear resistance.

It is worth noting that the higher the manganese content, the better. Under low impact wear or pure wear conditions, traditional Mn13 may not be able to fully trigger martensitic transformation, and its wear resistance may not be high. This indicates that the work hardening ability of high manganese steel depends not only on the manganese content, but also closely related to the impact energy level.

2. Wear resistance performance under impact conditions

The impact abrasive wear test provides quantitative comparative data on the wear resistance of Mn13 and Mn18. After 60 minutes of wear under low impact energy conditions, the wear resistance of Mn18 is significantly better than that of Mn13, and its wear surface hardness shows a slow increasing trend over time. At a higher impact energy (3.0J impact energy), the wear resistance of Mn18 is about 1.5 times that of Mn13, and the wear surface hardness can be increased to HB440 in a short period of time. This means that Mn18 can complete surface hardening in a shorter time and maintain a thicker hardened layer when subjected to sufficient impact loads.

From the perspective of the depth of the hardened layer and the degree of improvement in wear resistance, Mn18 has a deeper hardened layer under the same impact conditions, and its wear resistance is improved by about 30% compared to Mn13. This improvement has engineering significance for high impact frequency crushing scenarios, such as large cone crushers processing hard rocks.

3. The synergistic effect of carbon content and work hardening

Carbon and manganese jointly affect the work hardening ability in high manganese steel. The research results indicate that increasing carbon content and reducing manganese content can enhance the work hardening ability of austenitic manganese steel. Under non strong impact conditions, the work hardening ability and service life of high carbon medium manganese steel are better than those of ordinary high manganese steel. This conclusion suggests that the wear resistance advantage of Mn18 depends more on the overall design of its alloy system, rather than simply increasing the manganese content.

If the manganese content is less than 11%, a stable austenite matrix cannot be formed, and work hardening cannot be triggered after impact, resulting in a sudden drop of wear resistance by more than 50%; If the carbon content is higher than 1.4%, network carbides will precipitate. Although the hardness increases, the brittleness of the matrix increases, and it is prone to cracking and peeling during wear, which actually shortens the service life.

3、 The influence of material hardness on wear resistance

1. The correlation between material hardness and liner wear

The hardness of the material is an important parameter that affects the wear rate of the rolling mill bowl wall. As the hardness of the material increases, the extrusion force required for crushing increases, and the chiseling stress and contact stress borne by the lining surface correspondingly increase. For high manganese steel, this working condition is precisely conducive to the formation and maintenance of the work hardening layer.

Taking hard materials such as broken basalt (Mohs hardness 6-7) and granite (Mohs hardness 5-7) as examples, the impact energy generated during the crushing process is relatively high, and the work hardening on the surface of high manganese steel can be fully developed. The hardness of the hardened layer can reach HB500 or above, and the wear resistance potential can be well utilized. When the hardness of the material is low (such as limestone with a Mohs hardness of 3-4), the crushing process is mainly based on cutting and grinding, with insufficient impact energy, insufficient work hardening of high manganese steel, and limited wear resistance.

The particle size distribution of the material also affects the wear of the rolling mill bowl wall. Uneven feeding particle size or feeding segregation can accelerate local wear of the lining plate, and even if the material selection is reasonable, uneven wear may occur due to improper working conditions.

2. The guiding significance of material hardness in material selection

The hardness of materials can be divided into three levels: low hardness (Mohs hardness<4), medium hardness (Mohs hardness 4-6), and high hardness (Mohs hardness>6). There are differences in the applicability of Mn13 and Mn18 for materials of different grades:

Low hardness materials: During the crushing process, the impact energy is low, and the work hardening of high manganese steel is insufficient. The actual wear resistance difference between Mn13 and Mn18 is limited, and the wear resistance is difficult to fully exert. It may be more suitable to use high chromium cast iron or other wear-resistant alloy materials.

Medium hardness material: The impact energy is at a moderate level, and Mn13 can trigger work hardening relatively stably, with outstanding cost-effectiveness advantages.

High hardness material: With high impact energy, Mn18's advantages in hardened layer depth and wear resistance can be well reflected, making it suitable for handling high impact frequency and strong chiseling wear conditions.

4、 Suggestions for material selection under different hardness materials

Based on the impact energy conditions, material hardness, and equipment operating characteristics, the selection of rolling mill wall materials can be carried out according to the following framework:

Typical Material Types Applicable Material Selection Basis

Insufficient work hardening of low hardness materials such as limestone, gypsum, high chromium cast iron, or alloy steel makes it difficult to fully utilize the advantages of high manganese steel

Medium hardness materials (moderate impact) such as iron ore and sandstone Mn13 have outstanding cost-effectiveness, meeting conventional crushing needs

Medium hardness material (strong impact), iron ore (large block size), Mn13Cr2, chromium element enhanced matrix for wear resistance and improved toughness

High hardness materials (strong impact) basalt, granite, quartzite Mn18/Mn18Cr2 have a deep hardened layer and improved wear resistance by about 30% to 50% compared to Mn13

High hardness+strong abrasive materials, high silica, diabase Mn18Cr2 or bimetallic composite ultra-high manganese steel matrix+synergistic effect of hard alloy inserts

Mn13Cr2 and Mn18Cr2 add chromium element on the basis of traditional high manganese steel, which compensates for the insufficient toughness of traditional high manganese steel under pure wear conditions and can effectively extend the service life of wear-resistant parts. When the material has extremely high hardness and strong abrasion resistance, bimetallic composite materials are an alternative solution worth considering. This method uses high manganese steel or ultra-high manganese steel as the matrix, and embeds hard alloy or ceramic particles on the working surface to make the worn surface have higher wear resistance, while the non worn surface maintains excellent plasticity and impact toughness.

5、 Precautions in actual selection

1. The quality of heat treatment that cannot be ignored

The performance of high manganese steel rolling mill bowl wall depends not only on its chemical composition, but also on the heat treatment process, which is equally crucial. Castings must undergo water toughening treatment (heating at approximately 1050 ℃ and quenching with water), and the mechanical properties after water toughening treatment should meet the standard requirements. If the heat treatment is improper (such as too fast heating rate, insufficient holding time, or insufficient quenching cooling rate), even if the chemical composition meets the requirements, single-phase austenite structure cannot be obtained, and the work hardening ability will be greatly reduced.

2. Applicable boundaries of composite materials

The bimetallic composite material achieves a synergistic effect of hardness and toughness by embedding hard alloy or ceramic particles in the high manganese steel matrix, and has a certain lifespan advantage when dealing with extremely high hardness materials. However, it should be noted that the cost of composite materials is significantly higher than that of single high manganese steel, and an economic evaluation should be conducted before selection, based on the comprehensive judgment of ton processing cost.

3. Actual measurement of impact energy

'Impact energy' is not an abstract concept, but a physical quantity directly related to material block size, crusher speed, and discharge port settings. When selecting, a comprehensive judgment should be made based on the particle size distribution of the feed, equipment operating parameters, and actual working conditions. If large hard rocks are broken and the equipment speed is high, the impact energy is large, and the wear resistance advantage of Mn18 can be well utilized; If the feeding particle size is uniform and the equipment runs smoothly, the cost-effectiveness of Mn13 may be more suitable.

4. Wear pattern and material calibration of lining plate

Even if the same grade of high manganese steel is chosen, there may be significant differences in the actual service life of products from different casting manufacturers due to differences in smelting purity, heat treatment parameter control, casting processes, and other aspects. Establishing a liner wear record system (recording the operating time, processing tonnage, and wear morphology of each batch of liners), and reverse tuning material selection and casting process parameters through data accumulation, is an effective management method. If surface peeling occurs instead of normal wear when crushing high hardness materials, the material should be checked first to determine if it is qualified, and then judged if it is a mismatch between the working conditions and material characteristics. If the material is qualified but the impact energy is not sufficient to trigger sufficient work hardening, it may be considered to adjust the particle size distribution of the feed or use Mn18 material instead.