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Rust formation not only affects precision and surface roughness but also reduces service life, even rendering the bearing unusable.
Rust prevention for bearings is crucial, especially between processing stages. Bearings undergo pickling, cleaning, and grinding in the heat treatment workshop, followed by numerous other processes. When production is not done in a continuous flow, the finished products are stored in an intermediate warehouse. Therefore, bearing rings stored between processes must be rust-proofed.
Traditional methods using rust-preventive oils, similar to rust-preventive paints, and their shortcomings: Common methods for rust prevention between bearing processing stages include:
1. Immersion in rust-preventive tanks: Immersing the bearing rings in a 5% sodium nitrite and 0.6% sodium carbonate solution provides good rust prevention, but requires numerous rust-preventive tanks and other equipment, consuming significant space and making management inconvenient.
2. Coating with concentrated sodium nitrite solution: After cleaning, the products are immersed in a solution containing 15%-20% sodium nitrite and 0.6% sodium carbonate, and then stacked. This method has a short rust prevention period, generally only lasting 7-14 days. During the rainy season, due to the humid weather, it only lasts 2-3 days before needing to be retreated, requiring labor and money.
3. Oiling: Apply a rust-preventive oil similar to rust-preventive paint, just like a finished product. This method requires cleaning before proceeding to the next process, which is relatively troublesome.
Introduction to New Rust Prevention Process: Through collaborative research with relevant manufacturers and years of production practice, it has been shown that multiple improvements to inter-process rust prevention, particularly the spray-on method, yields better results. Initially, rust prevention for rollers was tested by rinsing semi-finished and finished products daily with a sodium nitrite solution. After 3 months, random inspections showed no rust. The spray-on method is now used for bearing ring semi-finished products with similar results. The spray-on rust prevention process is relatively simple, and the method is as follows:
1. Equipment Purchase and Construction: Based on the amount of semi-finished products to be stored, build an intermediate warehouse with a cement floor. A walkway of approximately 1.5 meters can be set up in the middle for the trolleys carrying the bearing rings. At the end of the passage, place a pool for storing a sodium nitrite solution. The solution formula is 5%-10% sodium nitrite plus 0.6% sodium carbonate. Construct a return drainage ditch on the ground, and then stack the bearing rings on the floor on both sides, leaving a 0.6m walkway between each stack. The intermediate storage area can be designed to be approximately 64m², with the sodium nitrite solution pool measuring 1m³.
2. Process Method: Rinse once daily in the morning with a sodium nitrite solution. The solution is pumped from the pool and routed through rubber pipes to a showerhead, rinsing the bearing rings like a spray. The rinsed solution flows back to the pool through the return drainage ditch. At the end of the return drainage ditch, on the upper layer of the pool, use a fine wire mesh and gauze to filter dust and dirt into the pool. The intermediate storage area should be kept clean. The solution in the tank is tested every two days, and replenished according to the results. The solution is replaced according to the different months: completely replaced every two weeks from April to September, and monthly from October to March of the following year.
Conclusion: Spray-spray rust prevention is convenient to manage and saves labor. Previously, two people were insufficient to complete rust prevention in the intermediate warehouse; now, one person can perform other tasks. The rust prevention effect is also significant. In March 2003, spray-spray rust prevention was used on over 4000 7002136 and 3620 rollers, and they have remained very shiny and rust-free for over a year. Furthermore, it significantly reduces chemical consumption. Previously, the roller workshop consumed over 4000 kg of sodium nitrite per month; now, only 200 kg is used, saving nearly half. Spray-spray rust prevention has been proven by relevant manufacturers in recent years to be very suitable for medium to large-sized, high-volume, long-cycle bearing semi-finished products.
