Role of staggered-array water jet on intensive quenching for heat treatment

Abstract

Water impinging jets have been widely used in quenching of hot steel plate. The role of staggered-array waterjet on intensive quenching is experimentally investigated at fixed jet Reynolds number of 35,000 and nozzle-to-plate distance of 100 mm. The time-and space-resolved heat flux and heat transfer coefficient can be exactly measured with 5 different staggered-array jet configurations ranged from SID = 3 to 8. The heat transfer characteristics were measured by a novel experimental technique that has a function of high-temperature heat flux gauge. The qualitative flow visualization showed complex flow patterns for staggered-array configuration, which exhibits a radial flow interaction issuing from adjacent water jets. The results show that the maximum area-averaged heat flux was observed at SID = 3. This is caused by the radial interaction between adjacent jets which affects different boiling heat transfer on a hot steel plate. The maximum cooling rate at the surface reaches nearly 600°C/sec during water jet quenching. This study is motivated by the fact that a new design of intensive quench process requires the role of staggered-array water impinging jet on its heat transfer characteristics. In case of intensive quenching process for heat treatment, the water jet quenching is nominally started from above the austenitic temperature of 900°C to the finish quenching temperature of 300°C at which the martensite formation starts. Finally the current study is to provide quantitative local and average heat transfer characteristics of the staggered-array water jet quenching. © 2015 ASM International®.