Repairing used gears by laser hardening and extending lifespan equivalent to or better than new gear
Tokyo, April 25, 2023 – Hitachi Construction Machinery Co. Ltd. (TSE: 6305, President and Executive Officer: Masafumi Senzaki, "Hitachi Construction Machinery") and the National Institute for Materials Science (President: Kazuhiro Hono, "NIMS") are pleased to announce that we have jointly developed a method for repairing the wear-damaged part of used gears by laser hardening*1 of the gear surface. Hitachi Construction Machinery and NIMS have also demonstrated that this method, which is used on gears that have been carburized by carbon diffusion to harden the metal surface, has the potential to extend the service life of the repaired gears as long as or longer than a new one.
*1 A technology for hardening metal by partial heating and cooling
Hitachi Construction Machinery will apply this method to the remanufacture of used gears from hydraulic pumps from April 2023, enabling an approximate 25% improvement in the rate of remanufacture and usage of gears destined for scrapping. In the case of a 20-ton hydraulic excavator, if remanufactured gears are always used instead of new ones during scheduled parts replacements, this method is estimated to have the potential to cut CO2 emissions generated in the manufacture of new parts by 13kg per excavator. The method is scheduled for application to mining machinery parts in future and for introduction at Hitachi Construction Machinery Group bases overseas that remanufacture construction machinery parts.
Hitachi Construction Machinery collects genuine used parts (e.g. hydraulic cylinders, hydraulic pumps and drive equipment) from customers when machines are repaired or parts are subject to scheduled replacement. The collected parts are then disassembled and serviced and supplied as remanufactured parts with the same function warranty as new parts. With long use, the gears, which are subject to heavy loads, become fatigued due to wear, residual stress*2, etc., resulting in deformation and breakage when they reach the end of their useful life. Hitachi Construction Machinery has demonstrated that, by applying a laser to the carbonized gear and partially modifying the surface structure to restore the hardness of the metal, which is one of the causes of malfunction, it is possible to extend the lifespan of gears as long as or longer than a new one.
*2 The stress generated inside an object when external force is applied. The stress remains even after the external force is removed, causing deformation and cracking.
This method was jointly developed by Hitachi Construction Machinery ’s Remanufacturing Division (Spare Parts and Service Business Unit) and NIMS’ Cryogenic Fatigue Group (Research Center for Structural Materials). Development of the method has been under way since 2020, following on from the toothed gear reusability evaluation method by x-ray radiation measurement, a collaborative project which was launched in 2019 and announced in May 2021.
Going forward, Hitachi Construction Machinery and NIMS will continue to contribute to efforts to reduce their impact on the environment.
- Sustainable Technology for Remanufacturing Carburized Steel by Laser Hardening
T. Kanazawa, M. Hayakawa, D. Vinas, Y. Tahara, N. Hata and M. Yoshimoto, Journal of Materials Research and Technology, 24, 2023, pp.39-48.
- May 20, 2021 MINS Web site Joint Development of a Toothed Gear Reusability Evaluation Method
About Hitachi Construction Machinery Co., Ltd.
Hitachi Construction Machinery Co., Ltd. (TSE: 6305), headquartered in Tokyo, Japan, is a construction machinery manufacturer. The company engages in the development, manufacturing, sales, and service operations around the world for hydraulic excavators, wheel loaders, road construction machines, and mining machinery. Hitachi Construction Machinery is strengthening its focus on value chain businesses other than new machinery sales, such as parts and services, rentals, used equipment, and parts recycling, and is utilizing digital technologies to provide deeper solutions at all points of contact with customers. Hitachi Construction Machinery employs approximately 25,000 people worldwide. In fiscal year 2021 (ended March 2022), the consolidated sales revenue was ¥1,025.0 billion and the percentage of overseas sales revenue was approximately 79%. For details, visit the company’s website.
Information contained in this news release is current as of the date of the press announcement, but may be subject to change without prior notice.