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Vacuum heat treatment of steel ring

GCr15SiMn steel ring is a kind of wear-resistant accessory on concrete pump truck. Because it has been in contact with wet cement sand and gravel particles such as concrete for a long time during operation, is worn by abrasive particles and eroded and corroded by concrete slurry, and the service environment is harsh, the selected material is steel for overall quenching, which requires sufficient hardenability, high hardness, wear resistance, and certain corrosion resistance, In order to avoid the impact on the construction progress due to frequent disassembly and assembly caused by early failure. Reasonable selection of materials and correct heat treatment are of great significance for prolonging the service life of these parts.

In order to minimize deformation and oxidative decarburization, the GCr15SiMn steel ring must be heat treated by vacuum quenching. Vacuum heat treatment does not oxidize, decarburize or increase carbon. After treatment, the workpiece surface is bright, with small deformation and long service life. Since all quenching operations are completed in a closed furnace, the degree of mechanization and automation is high, the labor intensity of workers is low, and there is no pollution to the environment.

The steel ring body is made of chromium bearing steel GCrl5SiMn, which has a complex shape and can be divided into two types: mountain shape and groove shape. Each type of steel ring body has multiple dimensions and specifications, and the shape is shown in the figure below. The shape of the mountain shaped steel ring is similar to that of the multi-layer pagoda, and the maximum outer diameter of the lower end φ 270mm, the diameter gradually decreases from bottom to top, forming 3 steps; The maximum outer diameter of grooved steel ring is φ 315mm, inner diameter φ 238mm, there are deep grooves at the internal steps, with groove width and depth of 10.15 and 14 mm respectively.

Processing technology of steel ring:

The processing procedure of the steel ring body is rolling forging → spheroidizing annealing → semi finishing → vacuum quenching and tempering → grinding the end face, inner diameter and positioning hole diameter. Effective dimension of vacuum quenching furnace is 900mm × 600mm × 600mm。

There is a large difference between the shape of the hill shaped and groove shaped steel rings. Each type has multiple specifications. The parts to be hardened are the inner hole and the outer circle. There is no hardness requirement for the upper and lower end faces. Therefore, the furnace is loaded by stacking the workpieces horizontally. In order to reduce heat treatment distortion, two-stage preheating is adopted during quenching and heating, and the vacuum heat treatment process is shown in the figure. The steel ring shall be tempered in time after quenching, and the twice tempering process shall be adopted to fully remove the stress and complete the structural transformation. After two times of tempering, the hardness of the two steel rings is 58-62HRC, meeting the customer’s technical requirements.

After quenching and tempering, the non matching parts of the inner and outer diameters will not be processed any more, and only the matching surfaces such as the end face, the matching parts of the inner diameter and the locating hole diameter will be ground. For the mountain shaped steel ring, the reserved amount before quenching can be used to increase the internal and external diameter to improve the distortion and reduce the post-processing. However, due to the expansion and contraction of the internal and external diameters of the grooved steel ring and its large ovality, the allowance for the internal and external diameters should be increased to ensure that the distortion does not exceed the tolerance after quenching.

Heat treatment equipment selection: The VOGQ series vacuum heat treatment furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment process of tools and dies. Good temperature control accuracy and uniformity ensure the effective implementation of the vacuum heat treatment process. SIMUWU focuses on the manufacturing 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 gas quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.