March Li is lead metallurgist and customer applications engineer for the power transmission division of Lufkin Industries LLC. He is responsible for various materials selection — including carbon and alloy steels, gray iron, ductile iron, aluminum alloys, copper alloys, etc.; heat treatment — normalizing/annealing, quenching, tempering, carburizing and nitriding; precise control of case hardening and disposition; welding; fatigue and fracture; and failure analysis. Li also provides metallurgical assistance to the product development of high-speed, low-speed and marine gearboxes (gears/pinions, shafts, housing and covers, etc.) for Lufkin's power transmission division, including gear repair in both the U.S. and abroad. (Bio last updated 2016-03-01 Contact Randy Stott, Managing Editor, with changes.)
Articles by March Li
- Practical Approach to Determining Effective Case Depth of Gas Carburizing (March/April 2016)
Effective case depth is an important factor and goal in gas carburizing, involving complicated procedures in the furnace and requiring precise control of many thermal parameters. Based upon diffusion theory and years of carburizing experience, this paper calculates the effective case depth governed by carburizing temperature, time, carbon content of steel, and carbon potential of atmosphere. In light of this analysis, carburizing factors at various temperatures and carbon potentials for steels with different carbon content were calculated to determine the necessary carburizing cycle time. This methodology provides simple (without computer simulation) and practical guidance of optimized gas carburizing and has been applied to plant production. It shows that measured, effective case depth of gear parts covering most of the industrial application range (0.020 inch to over 0.250 inch) was in good agreement with the calculation.