For 5.6 grade bolts that need to pass a -20°C impact test (27J), what material should be used, and is heat treatment required?

According to the standard requirements, the elongation after fracture after machining is not low, indicating that the material must have plasticity. Lower hardness generally indicates better plasticity, and higher absorption of impact energy during plastic deformation.

Therefore, alloying is not necessary; low-carbon steel, such as 1018 or 1022, is sufficient. It can be produced using spheroidized steel or by wire drawing followed by annealing.

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