Conductive copper containing about 0.02 to 0.05% oxygen, in which impurities are rendered harmless as oxides. Its conductivity is high, but heating in a hydrogen-containing atmosphere causes hydrogen embrittlement.
Japanese name: タフピッチ銅
Tough-pitch copper appears in 1 practice question across 1 topic, including Nonferrous metals and alloys.
Field: Nonferrous metals and alloys
Answer: A. Hydrogen that enters reacts with Cu₂O to form steam, which creates high-pressure cavities and cracks at grain boundaries, so oxygen-free copper or phosphorus-deoxidized copper is used
Hydrogen that diffuses into copper reacts with Cu₂O at grain boundaries and elsewhere as Cu₂O + H₂ → 2Cu + H₂O, and because water molecules cannot diffuse through copper, they create high-pressure cavities at grain boundaries that lead to cracking. This is called hydrogen embrittlement of copper (hydrogen sickness). The remedy is to use oxygen-free copper, which contains almost no oxygen, or phosphorus-deoxidized copper. Residual phosphorus lowers the conductivity of phosphorus-deoxidized copper, so oxygen-free copper is used where high conductivity is needed. Copper does not form stable hydrides, so the option blaming hydrides is wrong. Nor is the embrittlement caused by melting of Cu₂O; adding more oxygen only increases the source of steam.
Al-Li alloy Alclad Beryllium copper GP zone Temper designation γ'' phase