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不锈钢钮扣用到不同牌号不锈钢材料，常规的201#,202#,848#。三者的合金成分差异，导致其铁磁性、导电性不同，进而被检针机识别的灵敏度不同。另外要说明的是，行业内检针 “级别” 并无统一标准，多是企业根据检针机灵敏度旋钮刻度的俗称，级别越高代表检针机灵敏度越高，能检测到的金属异物越小或金属特性越弱的物质。下面结合三种不锈钢的具体情况详细解释：

1. 201# 不锈钢（1Cr17Mn6Ni5N）该牌号属于低镍高锰型奥氏体不锈钢。其化学成分中，锰含量为 5.5%-7.5%、镍含量仅 3.5%-5.5%，铬含量 16%-18%。为了降低成本，它用大量锰替代镍，这种成分比例会让材料保留一定的弱磁性，且导电性处于相对较高水平。而检针机对铁磁性金属和导电金属都有感应能力，所以它容易被中低灵敏度的检针设备识别，仅能通过 3 - 4 级这种较低灵敏度的检针测试。常应用于装饰、浅拉伸件等对检针要求不高的场景。

2. 202#不锈钢（1Cr18Mn8Ni5N）它是 201 不锈钢的升级款，成分上调整了锰和镍的比例，锰含量提升至 7.5%-10%，镍含量也提高到 4.0%-6.0%，铬含量略增至 17%-19%。相比 201，其奥氏体组织更稳定，锰与镍的配比优化使得材料的铁磁性进一步减弱，导电性也有所降低。这就让它对检针机的感应信号更弱，所以能通过 4 - 6 级这种中等灵敏度的检针。它的适用场景比 201 稍广，可用于对耐蚀性和检针要求略高的浅冲件、餐具等。

3. 848# 不锈钢（推测为 1.4848 不锈钢）市面上并无通用标准的 “848” 不锈钢牌号，结合能过 8 级高灵敏度检针的特性，推测其为欧洲标准的 1.4848 耐热不锈钢。它的成分和 201、202 差异极大，铬含量达 23%-27%，镍含量 19%-21%，还含有 1.5%-2.5% 的硅。这种高铬高镍配比让它形成了极其稳定的奥氏体组织，几乎无铁磁性，同时特殊的合金比例也削弱了其导电性。而且它生产时多采用电弧炉 + 氩氧脱碳二次精炼工艺，能减少氧化物等杂质残留，进一步降低了被检针机识别的概率，因此可通过 8 级这种高灵敏度检针。该材质常用于高温炉辊、涡轮叶片等对材质纯度和稳定性要求极高，且可能接触食品、精密器械等对检针要求严苛的场景。

4. 亚洲钮扣生产的不锈钢材料在专业材料商工厂定制而成，易拉伸，易电镀。
   

综上来看，不锈钢过检针的级别本质是材料成分决定的金属特性与检针机灵敏度的匹配度。合金中镍、铬等元素占比越高、成分越稳定、杂质越少，越不容易被检针机感应，能通过的检针级别也就越高。

The core reason why different grades of stainless steel can pass different levels of needle detection lies in their differences in alloy composition, which result in variations in ferromagnetism and electrical conductivity—two key properties affecting detectability by needle detectors. It should be noted that there is no unified industry standard for "needle detection levels"; these are typically enterprise-specific designations based on the sensitivity adjustment scale of needle detection equipment. A higher level indicates higher equipment sensitivity, enabling the detection of smaller metal contaminants or materials with weaker metallic characteristics. Below is a detailed explanation of the three stainless steel grades:

1. 201 Stainless Steel (1Cr17Mn6Ni5N)

Classified as a low-nickel, high-manganese austenitic stainless steel, its chemical composition features 5.5%-7.5% manganese, only 3.5%-5.5% nickel, and 16%-18% chromium. To reduce costs, a large proportion of manganese is used as a substitute for nickel. This composition retains a certain degree of weak ferromagnetism and relatively high electrical conductivity. Since needle detectors can sense both ferromagnetic and conductive metals, 201 stainless steel is easily identified by low-to-medium sensitivity needle detection equipment, only capable of passing needle detection tests at the 3-4 level (lower sensitivity). It is commonly used in applications with low needle detection requirements, such as decorative components and shallow-drawn parts.

2. 202 Stainless Steel (1Cr18Mn8Ni5N)

An upgraded version of 201 stainless steel, it features an optimized manganese-nickel ratio: manganese content increased to 7.5%-10%, nickel content raised to 4.0%-6.0%, and chromium content slightly enhanced to 17%-19%. Compared to 201, its austenitic structure is more stable, and the improved manganese-nickel 配比 further reduces ferromagnetism and lowers electrical conductivity. This reduces the material's inductive signal to needle detectors, allowing it to pass medium-sensitivity needle detection at the 4-6 level. Its application scope is slightly broader than 201, suitable for shallow stamping parts, tableware, and other products requiring moderate corrosion resistance and needle detection performance.

3. 848 Stainless Steel (Presumed to be 1.4848 Stainless Steel)

There is no universally recognized "848" stainless steel grade in general standards. Based on its ability to pass high-sensitivity (Level 8) needle detection, it is presumed to refer to 1.4848 heat-resistant stainless steel (per European standards). Its chemical composition differs significantly from 201 and 202: chromium content ranges from 23%-27%, nickel from 19%-21%, and it also contains 1.5%-2.5% silicon. This high chromium-nickel ratio forms an extremely stable austenitic structure with nearly no ferromagnetism, while the specific alloy ratio also weakens electrical conductivity. Additionally, it is typically produced via electric arc furnace melting combined with argon-oxygen decarburization (AOD) secondary refining, which minimizes residual impurities such as oxides—further reducing detectability by needle detectors. Thus, it can pass high-sensitivity needle detection at the 8 level. This material is widely used in high-temperature furnace rolls, turbine blades, and other components requiring exceptional material purity and stability, as well as in scenarios with stringent needle detection requirements (e.g., food contact materials and precision machinery).

In summary, the needle detection level a stainless steel can pass is essentially determined by the compatibility between the material's metal properties (dictated by alloy composition) and the needle detector's sensitivity. Higher proportions of nickel, chromium, and other stabilizing elements, a more homogeneous structure, and lower impurity content result in weaker inductive responses to needle detectors, enabling the material to pass higher-level needle detection tests.