The main differences between the model codes A2 and A4 of stainless - steel washers are as follows:
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Material Composition
- A2: It represents 304 - type stainless - steel material. Its main components are chromium (Cr) and nickel (Ni), generally containing about 18% chromium and about 8% nickel. It has good corrosion resistance and oxidation resistance.
- A4: It represents 316 - type stainless - steel material. Based on 304, molybdenum (Mo) element is added. It usually contains about 17% chromium, about 12% nickel and 2% - 3% molybdenum. This makes the corrosion resistance of 316 stainless - steel, especially the resistance to chloride corrosion, significantly better than that of 304 stainless - steel.
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Performance Characteristics
- Corrosion Resistance: A2 washers are suitable for general environments, such as indoor environments and some places without special corrosive media. Due to the presence of molybdenum element, A4 washers have stronger corrosion resistance and are especially suitable for corrosive environments such as marine environments, chemical industries and high - humidity conditions.
- Strength: The numbers after A2 and A4, such as “-70” and “-80”, indicate the performance grade of the product, and the number is 1/101 of the nominal tensile strength. Under the same performance grade, the mechanical properties such as tensile strength of A2 and A4 washers are basically the same. However, due to the composition characteristics of A4 material, its strength retention in some special environments may be better.
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Application Scenarios
- A2: It is often used in general mechanical manufacturing, indoor parts of building decoration, electronic equipment and other fields where the requirement for corrosion resistance is not particularly high. For example, in ordinary furniture assembly and the fixing of general electronic - equipment casings, A2 stainless - steel washers can meet the use requirements.
- A4: It is widely used in industries such as chemical, pharmaceutical and food processing, as well as in coastal buildings and shipbuilding. For example, in the connection parts of chemical reaction kettles and seawater desalination equipment, A4 stainless - steel washers can resist the erosion of corrosive media and ensure the safe and stable operation of the equipment.
- Product Cost: Due to the presence of molybdenum element in A4 material and the different requirements for nickel content, its production cost is usually higher than that of A2 material. Therefore, the price of A4 stainless - steel washers is generally more expensive than that of A2 stainless - steel washers. When choosing, it is necessary to comprehensively consider the specific use environment and cost budget.