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Multi-method to prevent 65Mn spring circle white point problem
The 65Mn spring washer, made from high-strength steel wire, is widely used in various applications due to its excellent elasticity and durability. In China, 65Mn is one of the most commonly used materials for spring washers. However, this material has a significant drawback: it has poor corrosion resistance. To improve its anti-rust properties, galvanization or cadmium plating is typically applied. Unfortunately, these surface treatments can lead to hydrogen embrittlement, which weakens the mechanical properties of the parts and increases the risk of failure.
To address this issue, changing the material of the spring washer is an effective solution. By using special stainless steel materials instead of 65Mn, it is possible to eliminate the need for galvanizing or cadmium plating, thereby reducing the risk of hydrogen embrittlement. One successful example is the development of stainless steel spring washers using 1Cr18Ni9Ti material by the Shanghai Spring Washer Factory. These washers have been successfully applied in the aerospace industry, where reliability is critical. Over the years, many aviation manufacturers have adopted this type of stainless steel washer, and no issues such as hydrogen embrittlement, loss of elasticity, or rust have been reported. Our institute also implemented similar stainless steel washers in a key project, and no quality problems have arisen so far. Therefore, it is recommended that other products still experiencing hydrogen embrittlement issues consider replacing 65Mn with stainless steel washers.
Currently, the range of stainless steel spring washers available in China is still limited, but there are established standards for their use. For example, QJ2963.2-1997 "Special Spring Washer Standard Stainless Steel Spring Washer" can replace GB/T93-1987 "Standard Spring Washer," and QJ2963.3-1997 "Light Stainless Steel Spring Washer" can replace GB/T859-1987 "Light Spring Washer." These alternatives offer better corrosion resistance without requiring galvanization or cadmium plating. While most commercial spring washers are still made from 65Mn, the presence of surface treatments like galvanization makes complete hydrogen elimination difficult. As a result, the possibility of hydrogen embrittlement still exists. Therefore, when the product's anti-rust requirements are not strict or the washer is used in a controlled environment, such as inside a sealed compartment, it is advisable to avoid galvanizing or cadmium plating and opt for alternative treatments like oiling or surface oxidation to prevent hydrogen embrittlement.
In addition to material changes, another approach to preventing bolt loosening is the use of rubber-proof anti-loose components instead of traditional spring washers. Previously, spring washers were the standard choice, but with advances in adhesive technology, products like Loctite and Iron Anchor have become popular solutions. Some aviation manufacturers have successfully replaced spring washers with thread-coated rubber anti-loose systems, and no quality issues have been found after testing. Our institute also implemented this technology in a key project, and it performed well under rigorous testing. The application of thread coatings involves gluing the screw on-site before assembly, which requires careful cleaning and proper screwing speed. However, this method allows for greater flexibility in selecting thread strength based on different connection conditions, such as load, detachability, and structural design.