Abstract
When machining hardened steel (⩾45 HRC) with polycrystalline cubic boron nitride (PCBN) tooling, the cutting speeds used produce high temperatures in the primary shear zone, which are sufficient to plasticize the workpiece. The paper initially reviews the effect of workpiece hardness and cutting speed on chip formation, workpiece surface integrity and cutting forces. Equations are detailed for determining the primary shear zone temperature, the proportion of heat conducted into the workpiece and the shear flow stress. Following on from this, experimental work is presented involving the orthogonal machining of AISI H13 hot work die steel with PCBN tooling. Tests were carried out over a range of cutting speeds with workpieces of different hardness, in order to provide cutting force, shear angle, chip morphology and primary shear zone thickness data. The shear flow stress decreased with increasing cutting speed and/or workpiece hardness. With the AISI H13 heat treated to 49±1 HRC, the stress magnitude changed more significantly with cutting speed and the proportion of heat conducted away from the workpiece approached 99 percent at 200 m/min. Shear localized chips were produced with white unetched layers due to intense heat generation followed by rapid cooling.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.