However, with regard to these groups of steels, where a full annealing temperature will be in the region of 1470°F, the steel should be fully annealed at approximately 1600°F so that it will achieve is lowest hardness after annealing.
The grain size will be of a prime consideration with the higher annealing process temperatures. The grain size will be controlled both by time and temperature. Obviously, in order to achieve a fine grain structure during the annealing process, the soaking time should be a short as possible and the selected process temperature as low as can be accomplished. This will assist considerably in achieving a fine grain structure after completion of the annealing process.
So, the selected annealing temperature will most assuredly produce the fine grain structure and a greater hardness upon hardening and cooling.
It is advisable to full anneal high-speed steel if any dimensional error has been made or if there is a need to reprocess the steel for further machining.
The process of annealing will prepare the steel for its further machining, and the final austenitizing will also assist in producing a grain-refining effect. If the steel is of the T series (Tungsten) this will not apply.
It is mandatory that the T series be subjected to a full annealing cycle to prepare it for re-machining for further working. If the steel is re-hardened without a full anneal process, the T series is most likely to produce a very coarse grain structure. The abnormal grain-size structure will then depend on the selected austenitizing temperature.