FLSmidth RXL306-0003 Cone Crusher Eccentric Bushing: Centrifugally Cast C93700 Bronze

Technical Specifications

Engineered to withstand extreme cyclical impact loads, the FLSmidth RXL306-0003 Cone Crusher Eccentric Bushing is manufactured via high G-force centrifugal casting using ASTM B505 C93700 high-leaded tin bronze. This critical drivetrain component features a concentricity of 0.02mm and an Ra ≤ 0.8μm surface finish, ensuring immediate hydrodynamic oil film generation. With a controlled hardness of 65-85 HBW, it delivers superior particulate embeddability, directly preventing main shaft scoring and extending maintenance intervals in severe hard-rock crushing applications.

FLSmidth RXL306-0003 Cone Crusher Eccentric Bushing Yonsmen Warehouse

Detailed Introduction

Tribological Challenges in Extreme Crushing Environments

Unscheduled downtime caused by eccentric bushing seizure or main shaft galling represents a primary operational bottleneck in high-tonnage hard rock crushing circuits. The extreme radial forces generated during the eccentric rotation phase place immense pressure on the boundary lubrication layer. The FLSmidth RXL306-0003 Cone Crusher Eccentric Bushing is engineered specifically to act as the ultimate fail-safe wear interface. By optimizing the metallurgical structure and maintaining rigid machining tolerances, this component prevents metal-to-metal transfer during high-load, low-speed startup phases or under momentary losses of lubrication pressure.

Metallurgical Matrix: ASTM B505 C93700 / DIN 1716 G-CuPb20Sn

The operational lifespan of an eccentric bushing is fundamentally dictated by its alloy composition. The FLSmidth RXL306-0003 utilizes a highly specialized High Leaded Tin Bronze, strictly conforming to ASTM B505 C93700 and DIN 1716 G-CuPb20Sn standards. The precise alloying ratio of 18-23% Lead (Pb) and 5-7% Tin (Sn) creates a dual-phase microstructure. The tin content alloys with the copper to create a robust, high-yield-strength matrix capable of absorbing the severe compressive forces of the crushing stroke.

Conversely, the high lead content does not alloy but instead disperses uniformly throughout the crystalline structure as microscopic pools. Under conditions of boundary lubrication—such as cold starts or temporary oil starvation—this dispersed lead acts as a solid lubricant. It smears across the Ra ≤ 0.8μm running surface, creating an emergency sacrificial film that drastically lowers the coefficient of friction and prevents catastrophic seizing against the steel main shaft.

Embeddability and Hardness Control (65 – 85 HBW)

A common engineering misconception is that harder bushings yield longer service lives. In the harsh, particulate-heavy environment of a crushing plant, a bushing that is too hard will inevitably score the main shaft—a component that costs significantly more and requires days to replace. The FLSmidth RXL306-0003 Cone Crusher Eccentric Bushing is heat-treated and normalized to maintain a strict hardness window of 65 – 85 HBW.

This specific hardness rating is optimized for maximum embeddability. When microscopic silica dust or metallic wear debris bypasses the primary dust seal and enters the lubricating oil, the 65-85 HBW surface allows these abrasive contaminants to embed safely deep into the bronze wall. This isolates the sharp edges of the contaminants, protecting the highly polished surface of the main shaft from abrasive grooving and extending the life of the entire eccentric assembly.

Centrifugal Casting: High G-Force Densification

Standard static sand casting methods frequently suffer from microscopic porosity, gas inclusions, and uneven grain boundaries, all of which act as stress concentrators under cyclical loading. To combat this, the FLSmidth RXL306-0003 is manufactured using a horizontal centrifugal casting process.

By rotating the mold at high velocities, the molten C93700 bronze is subjected to high G-force densification. The heavier copper, tin, and lead elements are forced radially outward to form a highly dense, uniform outer wall, while lighter impurities, oxides, and gases are forced to the inner bore. This inner layer of impurities is subsequently machined away during the roughing phase. The resulting metallurgical structure exhibits exceptionally high tensile strength, zero micro-porosity, and a strictly uniform lead distribution, ensuring consistent wear rates across the entire vertical length of the bushing.

Machining Precision and Hydrodynamic Lubrication

The transition from boundary lubrication to full hydrodynamic lubrication is the most critical phase of crusher operation. To facilitate the immediate generation of a stable oil wedge, the FLSmidth RXL306-0003 Cone Crusher Eccentric Bushing is CNC machined to ISO 2768-mK tolerances with a maximum concentricity deviation of just 0.02mm.

This ultra-tight concentricity ensures an even distribution of the oil film thickness, preventing localized pressure spikes that can fracture the oil film. Furthermore, the critical running surface is finished to an Ra ≤ 0.8μm. This surface finish minimizes microscopic asperities (surface peaks), ensuring that the fluid film thickness remains greater than the combined surface roughness of the bushing and the shaft, entirely eliminating metal-to-metal contact during steady-state operation.

Installation Protocol and Thermal Dynamics

The installation of the FLSmidth RXL306-0003 requires strict adherence to thermal expansion principles. Because the coefficient of thermal expansion for C93700 bronze is significantly higher than that of the cast steel eccentric, an interference fit must be executed precisely. The bushing must be supercooled using liquid nitrogen or dry ice, shrinking its outer diameter to drop freely into the eccentric bore.

Forcing the bushing via hydraulic pressing at ambient temperatures will inevitably shear the outer bronze wall, compromising the interference fit and leading to a spun bushing during crushing operations. Once normalized to ambient temperature, the bushing expands, creating a locked fit.