Study of Finished Surface Damage in Turning Maraging Steel

• Main Authors: ChengWei,Li, 李政衛
• Other Authors: 廖運炫
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/63945297236237814556

碩士 === 國立臺灣大學 === 機械工程學研究所 === 90 === Maraging steel, which exhibits combination of strength and toughness, is an alloy steel of low-carbon martensite hardened by precipitation. The scale-surface damage often remains on freshly machined surface when solution-treated and aged 18﹪Ni maraging steel is machined. This kind of damage downgrades the quality of the machined surface. It is found from experiment that scale-surface damage is attributed to the “built-up edge”, which is generated under certain cutting speed ranges in machining process. Formation of built-up edge causes an increase of tool nose radius, and the chip thickness is reduced as a result. The residual material is squeezed between the flank face of tool and the machined surface of workpiece, when chip thickness close to trailing edge is less than the minimum undeformed chip thickness under high temperature and stress. The “squeezing” thereafter leads to burrs formed on the feed mark ridges and scale-surface damage caused on the freshly machined surface. In addition, the saw-tooth chip that has the specific chip edge serration is formed with an increase of cutting speed. The serration at the free surface of chip causes unbalanced stress on the tool resulting in the happening of outer metal chip notch wear.