【正文】 rim (forging), spoke (steel or forgings), hub (castings or forgings) with three parts of the rough shape after welding process. After the final heat treatment after welding gear, the body part has good strength and toughness, some of the tooth with high bearing capacity. This normalizing or hardening after quenching the hardened gearrow table, the selection with the same hardened gears, but can control the carbon content of these steels in %, could face more barriers to take care of all aspects of performance. These materials are then quenched and the gear surface hardening line.3. Carburized hardened gear materialsThis gear blanks are forged, after carburizing and quenching, the strength and toughness and has good carrying capacity, and more stable performance. Generally use low Tianjin or low in Tianjin casehardened steel to manufacture. Selection of the problems that need attention1. Metallurgical qualitySoft or medium hard gear tooth failure is characterized by pitting spelling, plastic deformation or even broken tooth, hardened gears hardened layer occurs off or broken tooth. If the steel in the presence of more harmful gases and nonmetallic inclusions, the stress will be concentrated in the weak links or the small crack, as the origin of the various fatigue crack, leading to early failure of gear. Therefore, to ensure the quality of metallurgical materials is to avoid overloading the early failure of the important measures to gear one. Using a vacuum casting furnace melting, vacuum melting vacuum degassing process or double vacuum melting furnace and then electroslagremelting can greatly reduce the oxygen and hydrogen content. Nonmetallic inclusions will also be greatly reduced, but also to take measures to change the shape and size and distribution of inclusions in a good state test so that, after vacuum treatment .Material properties of the atmosphere than the melting of the material to to 1 times.2. The size of the original grain size and growth tendencies Heavy gear the selected material, though both are essentially finegrained steel, but some of the production process of the heating temperature higher than the fine grain nature of austenite grain coarsening temperature of the standards required (930 ℃), or in the heat of the actual operation does not occur inevitably local overheating.3. Harden ability used to ensure the H SteelIn recent years, foreign harden ability had introduced a more stable, with a more narrow harden ability guaranteed harden ability of steel that is H steel, to a fundamental stability in the quality heat treatment of gears. For example, in aviation, marine, automotive and other products had to switch gears H steel, required H Steel Can permeability of the bandwidth ≤ 6 HRC, oxygen content ≤ 20ppm, the original grain size 5. Simply H of steel is characterized by:(1) The reasonable properties that affect the harden ability of carbon and alloy element content of the cooperation。(3) To minimize carbon and alloy elements of the position segregation. At present there are some manufacturers in China had H of steel production.4. The choice of quenching performanceQuenching properties of the material hardening, including the extent and depth of hardened layer. Quenching properties of heavyduty gear choice points to the following three cases:(1) Softhardened gear tooth surface or in the quenching properties of materials: Due to the load conditions and gears asked each match is different, the hardness and strength gear requirements also vary. For example, soft and soft tooth with tooth surface, the small gear hardness generally HB240 ~ 280, large gear for the HB200 ~ 240。 much as possible to adapt to rapid heating surface quenching the various requirements, such as austenite faster, higher degree of uniformity, the heating temperature range to be wide. Quenching cooling rate to ease so. In general, the surface hardened gear materials, its position should be able to meet the quenching properties of the surface of Tianjin meet the technological requirements of fire.(3) Carburized quenching hardened gear materials performance: According to the heavy gear to withstand heavy load and the impact of certain characteristics of carburizing steel position should be based on the weak carbon atoms and noncarbon elements in the main to strong carbide element supplement. If the parts section of large, need to improve the quenching properties, shall be appropriately increased, such as Man, Ni and other weak carbide and noncarbon elements.2. Heavyduty gear blanks conditioning treatmentGear Blank conditioning treatment should be based on the technical requirements of gear, the selected material, the type of rough and final heat to determine the specific circumstances of technological measures. softhardened gear tooth surface or in preparation for rough treatmentFor this type of gear blank (casting or forging) preparatory heat treatment, hightemperature normalizing the microstructure, heat treatment and improve the ultimate cutting performance of high temperature annealing is more favorable than. The normalized heating temperature can reach 900 ~ 920 ℃ homogenization of austenite grain coarsening does not, do not need to take the second time after normalizing to refine grain. Surface Hardening Heat Treatment of Gear Blank preparationsSurface hardening and welding pieces of gear over rough castings forgings. The preparatory treatment included the original hightemperature normalizing to improve the processing performance of organizations and all looked down upon in the rough after quenching and tempering treatment, to adjust the gear for the bulk of the mechanical properties and surface hardening was well written organizational preparations. Quenched after going to meet the following two requirements:1. Body parts in plastic toughness sufficient basis to maximize strength, to enhance the overall performance of hardened l