New Steel Grades for Deep Carburizing of Windmill Transmission Components

摘要

However, while low pressure carburizing (LPC) is now well established for smaller components and conventional conditions (up to 980°C), a number of difficulties are expected when considering high temperature LPC of large components. First, conventional carburizing steels will undergo extensive grain growth during an exposure to 1050°C for 20 hours; while there are solutions to avoid the problem for shorter durations, there are no materials adapted to such heat-treatment durations. Second, the long exposure at high temperature means that the possibility of significant creep deformation should be considered. And third, the hardenability of the material commonly used for wind turbine gears (18CrNiMo7-6) may not be sufficient when switching from oil to gas quenching. The present work attempts to address these issues. On the basis of theoretical alloy design, numerical modeling and experimental work, two purposely designed steel compositions were industrially cast. They were used to manufacture large wind turbine gears and extensively tested. Experimental results are compared to those obtained with a standard 18CrNiMo7-6. Based on a full analysis of the possible production routes, a cost benefit of 20% is estimated by switching from the actual to the newly developed manufacturing route.