--Adequate Static and Dynamic Load Capacity: After undergoing quenching and tempering (quenching followed by high-temperature tempering), the core of the 50Mn material possesses sufficient strength and toughness. Furthermore, following surface induction hardening of the raceways, the surface hardness can reach HRC 55–62; the resulting hardened layer depth also fully satisfies the requirements for wear resistance and contact fatigue strength demanded by small and medium-tonnage equipment.
--Sufficient Toughness for Standard Operating Conditions: Although the low-temperature impact toughness of 50Mn is not as high as that of 42CrMo, its impact resistance is entirely adequate for the majority of small and medium-sized cranes operating under standard climatic and road conditions. Moreover, the suspension system inherent to the truck crane itself helps absorb a portion of the impact forces transmitted from the road surface.
This constitutes the most critical market factor driving the recommendation for 50Mn. Lower Material Costs: 50Mn features a relatively low content of alloying elements (primarily manganese); compared to 42CrMo—which contains expensive elements such as molybdenum (Mo) and chromium (Cr)—50Mn offers a distinct advantage in terms of raw material pricing.
--Mature and Stable Processing Technology: 50Mn exhibits good hardenability, though its critical hardening diameter is smaller than that of 42CrMo. For small and medium-sized bearings (typically with raceway diameters under 1.5 meters), the cross-section of 50Mn can be fully through-hardened during the quenching and tempering process. The associated heat treatment procedures are highly mature and yield high production success rates, thereby further reducing manufacturing costs.
--Maximized Cost-Effectiveness: Slewing bearings manufactured from 50Mn offer a service life and level of reliability sufficient to meet the operational demands of small and medium-sized cranes throughout their entire lifecycle. ARI bearing choose 50Mn that allows manufacturers to effectively control the overall manufacturing and maintenance costs of the complete crane unit—without compromising reliability—thereby enhancing our market competitiveness.
In the construction machinery industry, material selection adheres to a principle that combines "sufficiency for purpose" with "reasonable redundancy."
--Design Alignment:** For the slewing bearings used in small-to-medium tonnage truck cranes, the computational models are largely established based on the material properties of 50Mn steel. Within this tonnage range, selecting 50Mn in accordance with established standards fully complies with both design specifications and industry practices.
--Reasonable Redundancy: If a higher-strength material—such as 42CrMo—were selected for small-to-medium tonnage equipment, it would result in an unnecessary waste of material potential, despite offering a surplus of performance capacity. Unless the equipment is intended for long-term operation in extremely cold regions or is subject to specific overload conditions, the necessity for such "upward compatibility" is minimal.
This can be understood as follows: for a general-purpose truck crane with a lifting capacity of less than 25 tons, a truck crane bearing made of 50Mn steel represents a reliable, standard choice that has been thoroughly validated over time. ARI bearing usually Upgrades to 42CrMo becomes a more technically sound solution only when the equipment involves a larger lifting capacity (e.g., over 50 tons) or is required to operate continuously under harsh conditions characterized by extreme cold or high impact loads.
Therefore, the use of 50Mn steel is recommended for the small-to-medium slewing bearings. Although it may not offer the absolute highest level of performance, it achieves the most balanced and economically efficient equilibrium across the critical triad of "functional suitability, manufacturing cost, and process stability."
