[According to a report by the US Navy Metal Processing Center on June 6, 2016] In order to reduce the total cost of the "Virginia" class submarine (VCS), the US Navy has replaced the Block IV propulsion shaft material with 625 alloy, which has A nickel-based alloy with good corrosion resistance but difficult to process. In order to reduce the impact on costs and production schedules, the Navy Metal Processing Center (NMC) led a comprehensive task force to solve the processing problems of these components. The comprehensive task force investigated new processing tools, cooling technology and other improvements. The members of the task force also include the Maritime Systems Command, BAE Systems, and the National Defense Manufacturing and Processing Center.
NMC first conducted small-scale tests and formulated a set of preliminary processes, including welding cap removal, rough machining, finishing, etc., and then carried out a large number of experiments to obtain the optimal process parameters. Considering the service life and replacement time of each tool, the processing efficiency of the optimized process (including tools, depth, speed and replenishment parameters, etc.) is increased by 2-3 times compared with the traditional processing technology. After that, the optimization process was verified in larger sizes. In addition, experiments have shown that the new process can be used to turn 625 alloy internal threads, with certain improvements in cost and quality.
The project aims to use the new technology for the production of the propulsion shaft of VCS Block IV. In April 2015, BAE Systems has partially adopted 625 alloy on the propulsion shaft assembly of Block III. BAE is also continuing to develop other tools for new drilling machines. 625 alloy internal thread turning will begin commercial applications on Block IV.
This new process will increase the productivity of 625 alloy propeller shafts and reduce production costs. According to preliminary estimates, the processing time and cost of 625 alloy will be three times that of HY steel. By adopting more efficient processing techniques, it is expected to save US$6 million in the next five years. By shortening the critical processing time by about 150 days, the new process will greatly reduce the lag in component production, and the risk of ship delivery delays causing costs to increase at a rate of 85,000 US dollars per day.
(China Ship Information Center Munan Zheng Yizhen)