Abstract
Hardening and case hardening are among the most common types of heat treatment processes, which can be performed in either atmosphere or vacuum furnaces. These processes, followed by oil quenching, are carried out in batch sealed quench and continuous furnaces such as pusher, roller, or rotary hearth types. Atmosphere heat treatment technology and equipment was developed more than 60 years ago with little new product innovation or change since. However, in this time period the needs of manufacturing have changed dramatically, driven by global competitiveness and the drive for lower unit cost. As such the heat treatment solutions must be capable of achieving higher productivity (through shorter cycle times), increased flexibility (with respect to material and process/cycles) and meet higher product quality standards. In addition, today’s manufacturing requires absolute process reproducibility and integration with other manufacturing processes, all done using energy efficient and environmentally friendly equipment. The solution to this situation is modern vacuum furnace technology and vacuum equipment that easily adapts to stringent specifications and changing industry standards. In this discussion, two case studies of this technology are presented. The first includes a two-chamber sealed oil quench vacuum furnace to case harden a SAE 5120 component to a surface hardness of 61 HRC using a Low - Pressure Carburizing (LPC) process. The result was a 30% savings over traditional atmosphere carburizing integral quench furnace owned by a commercial heat treater. The second study involves the use of a three-chamber sealed oil quench vacuum furnace to case harden SAE 5115 steel automotive steering components to an effective case depth of 0.9 mm minimum and a minimum surface hardness of 60 HRC. Using LPC these parameters were easily achievable. By, using a three-chamber sealed oil quench furnace, the potential for up to 600 kg/hr throughput was demonstrated, while maintaining costs comparable to a traditional atmosphere style integral quench furnace. Together, both studies show that sealed oil quench vacuum furnaces can improve process time and quality over a traditional atmosphere integral quench furnace while maintaining the process costs needed to remain competitive.