Quote from How to make it in Brass - Copper Development Association
250-300°C - 482-572°F
stress relief
When cold worked brass is progressively heated, the first effect, at about 250°C, is for the internal stresses to be relieved. This prevents stress corrosion cracking subsequently occurring and also minimises the amount of distortion which may occur during machining. This low temperature heat treatment, which should be applied for 1⁄2 to 1 hour, is known as ‘stress-relief annealing’ and has little, if any, measurable effect on the mechanical properties of the material. The improved strength due to the cold working is therefore retained.
In order to relieve internal stresses without loss of properties a low-temperature anneal such as 1⁄2 to 1 hour at 250-300°C should be used, dependent on section size.
400°C -752°F
As the temperature is increased further, a rather more fundamental change occurs at about 400°C and above and the material starts to ‘anneal’ or soften with time at temperature. The strengthening effect of the cold working is progressively lost, until at about 500°C the alloy is in the fully annealed condition. Restoration of the cold worked properties can then only be achieved by further cold work.
500-550°C 932-1022°F
In order to fully soften most brasses, heat to 500-550°C for 1⁄2 to 1 hour at temperature, then either air cool or, especially for alpha alloys, ensure that excessive grain growth is prevented by a quench or rapid furnace cool.
550°C -1022°F
‘Flash’ annealing can be carried out at higher temperatures for considerably shorter times, but care is
needed to avoid excessive grain growth.
900-940 °C- 1652-1724 °F melting point of brass
source: Wikipedia