Hydrogen Embrittlement氢脆

What is hydrogen embrittlement?什么是氢脆？

Hydrogen atoms can enter high-strength steel during acid pickling, electroplating or phosphating, and also later from corrosion in service. Under tensile stress the hydrogen gathers at weak points in the steel and can cause a sudden brittle fracture — often hours or days after the fastener has been tightened, with no warning.高强度钢在酸洗、电镀、磷化等工序中会吸收氢原子，使用过程中的腐蚀也可能带入氢。在拉应力作用下，氢聚集在钢材的薄弱部位，可能导致突然的脆性断裂。断裂往往发生在拧紧后几小时甚至几天，事先没有任何征兆。

Which parts are at risk?哪些零件有风险？

• Parts with high hardness: the risk rises sharply above about 320 HV, i.e. property class 10.9 and higher硬度高的零件：硬度超过约 320 HV（即 10.9 级及以上）时风险明显增加
• Case-hardened parts such as tapping and self-drilling screws, spring washers and spring pins渗碳件及弹性件，如自攻螺钉、自钻螺钉、弹簧垫圈、弹性圆柱销
• Parts that are electroplated or acid-cleaned经过电镀或酸洗的零件
• Parts under high sustained tension in service长期承受高拉应力的零件

How to reduce the risk如何降低风险

• Choose a non-electrolytic finish for class 10.9 and above — zinc-flake coatings or mechanical plating do not introduce hydrogen in the same way. Electroplating class 12.9 parts is generally avoided.选用非电解表面处理：10.9 级及以上优先采用锌铝涂层或机械镀，这类工艺不会像电镀那样引入氢。12.9 级零件一般不建议电镀。
• Bake after plating — if electroplating is required, a de-embrittlement bake (typically around 200 °C for several hours) is carried out as soon as possible after plating. Baking reduces the risk but cannot guarantee it is eliminated.电镀后除氢：如必须电镀，应在电镀后尽快进行除氢烘烤（通常约 200 °C、保温数小时）。烘烤可以降低风险，但不能保证完全消除。
• Clean without acid — use shot blasting or alkaline cleaning instead of acid pickling for high-hardness parts.避免酸洗：高硬度零件改用喷丸或碱性清洗。
• Specify and test — call up ISO 4042 for electroplated fasteners, and verify with a sustained-load test such as ISO 15330.明确要求并验证：电镀紧固件按 ISO 4042 提出要求，并可用 ISO 15330 等持续加载试验进行验证。