Estimatin of Recrystallized Grain Size under Continuous Annealing of Cold-rolled .BETA. Titanium Alloy Strips.

Abstract

We have investigated the behavior of the recrystallization and the grain growth of a cold-rolled Ti-15V-3Cr-3Sn-3Al and proposed a method for estimating the grain size after recrystallization during a continuous annealing process. The estimation of the grain size recrystallized under continuous annealing has been carried out by sequentially integrating, step by step, each increment of the isothermal grain growth at each temperature.The observation of the microstructure reveals that the grain size recrystallized under isothermal annealing, D(T, τ)/μm, can be indicated by D(T, τ)=0.80×104τ0.24 exp(–1.50×104/RT), where T and τ are the annealing temperature and time, and R is the gas constant. The estimate of the grain size recrystallized under a continuous heating process is in good agreement with the actual grain size. In addition, the grain size of the Ti alloy produced on the production line also agrees well with the calculated results using the temperature and passing time period of the continuous annealing line. This estimation provides good information for controlling the grain size after continuous annealing and leads to the production of finer-grained Ti-15V-3Cr-3Sn-3Al coils than have ever been obtained before.