The Use of Water Spray Quenching for Long Steel Bars

As most steels must be cooled at controllable cooling rates, i.e., rapidly at the start of quenching and slowly at the finish for minimum distortion and cracking, liquids with relatively high boiling points and low specific heats are often desirable especially when dealing with long round bars where low-distortion quenching is so important. Oils and polymeric solutions often satisfy these requirements more closely than water. However, these quenchants are more expensive and their use encounters more difficulties and impact on the environment. Economic considerations require the elimination of the post heat treating straightening of parts. Having this in mind, CAN-ENG has developed a water spray quench system that satisfies both optimal performance and cost. This quench system incorporates controlling of the operation parameters, such as flow rate, velocity and temperature of water, quench time, linear and rotational speeds of parts (bars), depending on the part diameter and length. The paper outlines the design features of the system and presents some results of field tests carried out as part of tuning-up the operation parameters and investigating the physical phenomena taking place at steel quenching under conditions of intensive cooling (spray quenching). The system was found to be efficient in low-distortion heat treating of steel bars over wide ranges of diameters and lengths.