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Vacuum Heat Treatment Furnace

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Precision gear vacuum heat treatment process

With the rapid development of science and technology, the development of CNC machine tools and high-precision machine tools has accelerated. The working load of the machine tool is heavy, the movement speed is fast, and the precision of the parts is required to be higher. Therefore, higher requirements are put forward for the material and heat treatment of the machine tool parts. Machine tool gears require smooth transmission, high strength, deep hardening, wear resistance and good dimensional stability. At present, the tooth-making methods of machine tool gears (induction heating and quenching, carburizing and quenching, and nitriding processes) are difficult to adapt to the technical requirements of machine tools in the new era. Therefore, vacuum quenching and low temperature vacuum tempering are used.

Vacuum heat treatment process:

Due to the extremely small dimensional changes before and after the gear heat treatment, it may be difficult to meet the requirements if the conventional salt bath furnace is used for heating and quenching. Therefore, a pre-heat treatment process and a micro-deformation vacuum heat treatment process must be selected.

Vacuum heat treatment has the advantages of high quality, low energy consumption, and no pollution (or less pollution), which can effectively prevent gear defects, improve surface roughness, and reduce friction coefficient. The vacuum heating is carried out in the form of radiation, the heating is slow, the furnace temperature is uniform, the product deformation is small, and it also has a dehydrogenation effect, which is conducive to improving the precision of the gear.

Process flow

The main process is as follows:

Forging-vacuum annealing-rough turning-normalizing-high temperature vacuum tempering-finishing-hobbing-rough drawing keyway (leave 0.5~1mm processing allowance)-stress relief-fine drawing keyway (to size)-vacuum quenching, vacuum Tempering – Grinding inner hole.

Pre-heat treatment process

The original structure state and streamline distribution of the gear before vacuum quenching not only affect the strength and toughness of the gear, but also mainly affect the deformation after heat treatment. Therefore, the blank must be pre-heat treated, and the specific process is as follows:

Micro-deformation vacuum quenching process

Vacuum quenching is one of the key processes for gears to obtain good performance and small deformation. The heating method, heating temperature, holding time, vacuum degree, furnace charging method and cooling method have a direct impact on the performance, surface quality and deformation of the gear:

(1) Quenching heating temperature and holding time are the key to obtain the required mechanical properties and achieve micro-deformation of the gear. In order to reduce the thermal stress as much as possible, a stepwise heating method and a lower quenching heating temperature should be adopted, and the holding time should be sufficient.

(2) Furnace loading method.

In addition to adopting step heating to achieve uniform heating in the process, in terms of workpiece placement, try to make all parts of the gears heat up synchronously to avoid excessive radiation heat transfer on the shady side, so that the distance between the gears and the radiation heat source is even. In addition, in order to reduce the elliptical deformation of the gears, they all adopt the form of laying flat and empty.

(3) Vacuum degree.

Heating, heat preservation and cooling in a vacuum state can make the parts obtain special effects that other heat treatments do not have. The surface of the workpiece is bright and free from oxidation and decarburization, and the workpiece has the functions of vacuum deoxidation and surface purification. Under the rough vacuum of 133Pa, heating and heat preservation, there is no series of problems such as evaporation of alloying metal elements.

(4) Quenching and cooling.

Oil cooling under low vacuum backfilled with nitrogen to 66.6Pa. In order to reduce deformation, it is necessary to achieve uniform cooling and uniform structural transformation of the workpiece. In addition to mechanical stirring of the quenching oil during operation, the up and down movement of the workpiece must also be increased.

The specific process is as follows:

The gear after vacuum heat treatment has high processing precision, good mechanical properties and long service life, and is a very high-quality gear product.

Vacuum furnace equipment selection: VOGQ series oil quenching furnace and RVT series vacuum tempering furnace produced by SIMUWU company are high-quality products for gear vacuum heat treatment process. Good temperature control accuracy and temperature control uniformity ensure the effective vacuum heat treatment process. SIMUWU company focuses on the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.