Effect of Water Temperature on Cooling Capacity in Water Cooling of Hot Steels

Abstract

In water cooling of hot steels, a cooling capacity (H) is influenced by water temperature(θ_w). The authors analyzed the effect of water temperature on the cooling capacity by using the data of authors' and other reseachers' experiments. The coefficient of water temperature Rb [°C^-1], which is the contribution factor of water temperature to the cooling capacity, is defined as Rb=[H(θ_b+Δθ)-H(θ_b-Δθ)]/[H(θ_b)×2·Δθ], where θ_b and Δθ are basic temperature and temperature difference from θ_b, respectively. By introducing the idea of Rb, the effect of θ_w on H in many experiments has been analysed systematically. The mian results obtained are as follows:
1) The values of R_{θb, 5} (θ_b:30, Δθ:5), which correspond to the typical temperature of cooling water in production mills, exist within the range of -0.01 to -0.02°C^-1. This result means that the values of H change_??_(1 to 2)% with ±1°C variation of θ_w.
2) The absolute R_{θb, 5} -value of laminar coolings is larger than that of spray coolings.
3) It seems that the values of Rb are influenced by sizes and surface conditions of a steel to be cooled, flow conditions of cooling water on a cooled surface, and so on.