In the operation system of heavy mining machinery, although the flat washer of the crusher is a tiny part, it plays a crucial role in distributing the load, protecting the connection interface and maintaining structural stability. In the face of the combined working conditions of ore impact, dust erosion, chemical corrosion and extreme temperature changes, how to scientifically select materials and accurately evaluate the anti-corrosion performance has become the core issue determining the equipment maintenance cycle and operational safety.
The core consideration dimensions for material selection
The working environment of the crusher is highly destructive. When selecting materials for flat washers, five major dimensions need to be comprehensively evaluated: The mechanical strength must be able to withstand the pre-tightening force of the bolts and the impact load of the ore to avoid crushing and deformation; Corrosion resistance should be able to withstand the erosion of moisture, chemical agents and mineral exudates. Temperature adaptability needs to match the heat generated by equipment friction with the temperature difference of the climate. Electrochemical compatibility is required to match the material of the connected parts to prevent galvanic corrosion. Cost-effectiveness balances procurement costs with service life. These dimensions are mutually restrictive and need to be prioritized based on the specific materials to be crushed (metallic minerals, non-metallic minerals or construction waste) and the process conditions (dry or wet crushing).
Common material properties and applicable scenarios
Carbon steel alloy materials are the most widely used in the field of crushers. Ordinary carbon structural steel stamping gaskets are suitable for low-stress areas in dry environments, but without surface treatment, they will rust within 24 hours in a humid environment. Galvanized carbon steel, through the sacrificial anode protection mechanism, can provide a protection period of 3 to 5 years when the coating is intact, but the hardness of the coating is relatively low and it is prone to wear under vibration. The upgraded Dacromet coated carbon steel has extended its anti-corrosion life to 8-10 years. Its non-hydrogen embrittlement feature is particularly suitable for the connection parts of the mobile jaws of the crusher that bear impact loads. Moreover, the coating hardness can reach 6H, and the wear resistance is significantly improved. Hardened carbon steel gaskets with a hardness grade of 200HV or above, which enhance load-bearing capacity through quenching and tempering processes, are suitable for high-pressure stress areas such as main shaft bearing housings.
Among the stainless steel family, 304 austenitic stainless steel, with an alloy ratio of 18% chromium and 8% nickel, performs exceptionally well in scenarios where damp materials are crushed. It can resist the erosion of weak acids and weak alkalis and has a service life of over 15 years. For equipment processing sulfur-containing ores or using flotation processes, 316 stainless steel, due to the addition of 2-3% molybdenum, is immune to chloride and sulfide corrosion and is an ideal choice for the combined operation area of ball mills and crushers. However, it should be noted that the hardness of stainless steel is relatively low (usually ≤200HV), and in super-heavy equipment, it may be necessary to increase the thickness or combine it with hardening treatment.
Non-ferrous metal materials are irreplaceable in specific scenarios. Copper gaskets have excellent electrical conductivity and are used for grounding the crusher motor and connecting sensors. However, they have low strength and are prone to ammonia corrosion, so they need to be inspected and replaced regularly. Titanium alloy gaskets have a density of only 60% of steel but comparable strength. They can reduce weight in mobile crushing stations. Their excellent corrosion resistance stands out in sea sand crushing projects, but processing costs need to be taken into account in the budget. Aluminum alloy gaskets have limited application in the field of crushers due to their insufficient hardness and electrochemical activity, and are only suitable for non-load-bearing parts such as control cabinets.
Polymer composite materials are revolutionizing traditional designs. Nylon 6 (PA6) gaskets have self-lubricating properties. They can reduce the coefficient of friction by more than 50% in adjusting devices and sliding parts. Their wear resistance and vibration absorption capacity can buffer the impact of minerals, but their upper temperature resistance limit is only 120℃, making them unsuitable for high-temperature friction areas. Polyoxymethylene (POM) has excellent dimensional stability, with tolerances controllable within ±0.05mm, and is used in hydraulic adjustment systems for precise positioning. Polytetrafluoroethylene (PTFE) has extremely strong chemical inertness and is used as an isolation pad in the crushing of corrosive slurries to prevent contact corrosion between metals. However, its compressive strength is only 1/10 of that of steel, and the load must be strictly calculated.
Anti-corrosion performance evaluation system
Scientific assessment needs to go beyond surface observation and establish a three-level testing standard. Level 1: The laboratory accelerated test adopts neutral salt spray test (NSS) to simulate a humid environment. Ordinary galvanized gaskets show white rust after 72 hours, while samples treated with Dacromet can withstand more than 1000 hours. The copper-accelerated acetic acid salt spray test (CASS) is more rigorous and is suitable for evaluating equipment parts for processing acidic ores. Level 2: Electrochemical testing measures the corrosion current density through polarization curves to quantify the corrosion rate of materials in specific media. The corrosion current of 304 stainless steel in A slurry simulation solution with pH=4 is approximately 2μA/cm², while that of 316L can be reduced to below 0.5μA/cm². Level 3: On-site hanging piece test involves installing the specimen in the crushing chamber and measuring the weight loss and morphological changes every three months to obtain real working condition data. A case of an iron mine shows that the annual corrosion rate of untreated Q235 gaskets reaches 0.8mm, while that of 250HV Dacromet gaskets is only 0.02mm. It is estimated that their service life exceeds the major overhaul cycle of the equipment.
The microstructure of surface treatment determines the anti-corrosion effectiveness. The thickness of the hot-dip galvanized coating can reach 50-80μm, but high temperatures may cause hydrogen embrittlement of the substrate. The electro-galvanized coating is uniform but only 5-15μm thick, relying on the passivation film to seal the pores. The flaky zinc-aluminum sheet superimposed structure of the Dacromet coating forms a shielding effect. Combined with chromate passivation, even if scratched, it can inhibit the spread of rust through electrochemical protection. The newly developed chromium-free Dacromet technology is more environmentally friendly and meets the requirements of green mine construction, but its long-term protective capacity needs to be verified.
Technical list for procurement decisions
When formulating the specification sheet, five technical parameters need to be clearly defined: Material grade and standard (such as GB/T 96.1, DIN 7349), hardness grade (it is recommended that crushers with a hardness of 200HV or above be preferred), surface treatment type and salt spray test duration, dimensional tolerance (inner diameter tolerance should be controlled within +0.1/-0mm to ensure smooth assembly), batch quality inspection report (including hardness test, salt spray test, metallographic analysis). For key parts, the supplier can be requested to provide finite element analysis verification to confirm the stress distribution of the gasket under the maximum bolt preload and impact load, ensuring that the edge compressive stress is less than 80% of the material’s yield strength.
The delivery and acceptance shall be carried out through four inspections: full inspection of the first piece’s dimensions, sampling hardness testing for each batch (the number of samples shall be in accordance with AQL 1.0 standard), surface film thickness measurement (magnetic thickness gauge accuracy ±1μm), and verification of the salt spray test report. For continuous orders, it is recommended to conduct a third-party corrosion performance audit once a year to ensure process stability. The packaging should be sealed with VCI vapor phase anti-rust bags to prevent salt spray erosion during sea transportation.
The material selection and anti-corrosion assessment of the flat gasket of the crusher is a systematic project, which requires a deep integration of material science, corrosion engineering and equipment working conditions. By establishing a data-driven material selection model and a strict supplier technical review mechanism, the risk of unplanned downtime can be significantly reduced, the parts replacement cycle can be extended to the planned major overhaul window of the equipment, and the optimal cost throughout the entire life cycle can be achieved. Under the major trend of green manufacturing and intelligent operation and maintenance, suppliers with verifiable anti-corrosion data and mechanical performance tracking capabilities will provide more reliable connection guarantees for mining enterprises.
Post time: Nov-27-2025