Carburizing and quenching are critical operations in the manufacturing of hardened gears. As one of the oldest gear makers in China, Nanjing High Accurate Drive Equipment Manufacturing Group Co., Ltd (hereinafter referred to as NGC) is one of the few companies which started making hardened gears in the earliest time. As early as in 1993, NGC led the drafting of YB/T 050-1993 YNK Gear Reducer for Metallurgical Application) of China metallurgical industry standard, and it played quite a positive role in localization of hardened gears.
Top ranking heat treatment equipment
In the recent years, NGC made great progress in deep carburizing and quenching process. In the heat treatment workshop of one subsidiary of NGC (Nanjing High Speed & Accurate Gear (Group) Co., Ltd, hereinafter referred to as Nanjing High Speed & Accurate), furnaces of deep carburizing and quenching are mainly from AICHELIN, including VBEK400/200 large pit-type gas carburizing furnace, 2 sets of VBEs 280/250 large pit-type gas carburizing furnaces, MRE10-280/200 large pit-type gas carburizing furnace and RJJ160/550 large pit-type gas carburizing furnace. All of these equipment are controlled by German DEMIG4008 Carbon Potential Control Expert System. This advanced system is stable, with temperature control precision of ±1℃, carbon potential control precision of ±0.02%Cp and furnace temperature uniformity of ±5℃, carbon potential uniformity of 0.05%Cp.
Advanced heat treatment process
Climbing up the Summit Step by Step, Striving after the Perfection Bit by Bit is the corporate spirit of NGC. For years, NGC has been focused on development and innovation of product, technology and manufacturing process, etc. In order to improve our heat treatment technology to world top level, all the staff in the heat treatment workshop of Nanjing High Speed & Accurate put as much effort as they could and finally made a great progress in deep carburizing and quenching process. Pre-carburizing, buffering-carburizing, circular heating carburizing and other new techniques were used for big module gears made of 17CrNiMo6 and 20CrMnMo, delivering heat treatment quality of Grade ME in ISO6336. Procedure for protecting welding seams on welded gears during carburizing has been upgraded for three times, as a result we can manufacture gear part of this type as big as with a diameter of 3800mm. BTL variation of the large ring gear (Ф3000) on the first stage of MFY gear reducer for central drive mill caused by heat treatment deformation is controlled to be less than 0.5mm. Carburizing may last as long as 240 hours, and the case hardening depth can reach 8mm without reworking.