Worm is a vital Section of device Instrument rotating elements. Worm spiral surface area and worm equipment tooth area slip somewhat when Performing, that's easy to wear. As a result, the worm will usually carburizing quenching remedy to get higher hardness to forestall worm spiral surface area don. Worm pieces involve high precision, And so the processing engineering is sophisticated and extended. If there is any dilemma in the course of processing, it's going to trigger large reduction. A style of worm pieces inside our enterprise appeared grinding cracks in the course of grinding, resulting in parts scrapped, very seriously influencing the production program.
one. Worm product and most important process movement
The worm material is 20CrMnTiH and the heat treatment method necessitates carburizing and quenching that has a depth of 1.1-one.5mm in addition to a floor hardness of 58HRC soon after quenching.
Blanking→Forging→Normalizing→Rough machining→Anxiety relieve→Fantastic machining→carburizing→Carbon get rid of on the thread→Quenching→Rough grinding→Exam→Growing older→High-quality grinding
Heat treatment approach: Forging normalizing→ Carburizing →Quenching →Reduced temperature tempering →Straightening→Strain aid→Small temperature getting old.
Just after carburizing and quenching, the carburized depth layer is one.32mm as well as floor hardness is 59 to 60HRC.
2. Crack phenomenon description
Immediately after tough grinding, the crack appears about the tooth surface area on the worm. The cracks are extremely great, linear and shallow in depth. The shape from the cracks is generally called "hairline". The cracks are usually not parallel and scattering traces.
three. Evaluation of grinding cracks
It is obviously diverse from prevalent quenching cracks. The quenching cracks are thick and deep, and the volume of cracks is small. It only occurs around the grinding surface area, and also the amount is massive, the depth is shallow, though the depth is largely precisely the same. The lighter types are stripe cracks perpendicular to or nearly perpendicular on the grinding way. The worm tooth area is usually a spiral floor.
While in the grinding strategy of heat-treated elements, the instantaneous higher temperature within the grinding zone can attain 400-1500 ℃ because the grinding wheel is blunt, the grinding depth is just too deep plus the cooling is insufficient. Consequently, the grinding burn off manifest, causing the modifications of surface area microstructure, microhardness, residual stress and mechanical properties from the elements.
The formation of cracks is connected with the hardness of your workpiece. Even though the workpiece with hardness lower than 55HRC could be burned, the event of grinding cracks is uncommon. The workpiece with hardness over 60HRC will drastically boost the potential for crack. The measured hardness from the component is fifty nine ~ 60HRC, which considerably improves the inclination of grinding cracks. Within the a single hand, when grinding problems are incorrect or grinding is not regular, grinding area will To begin with variety a robust burn up center, causing uneven thermal worry. In alternate superior temperature and rapid here cooling, the stress benefit gradually greater. Once the tension exceeds the fabric power Restrict, the grinded floor will create cracks. Conversely, the retained austenite during the floor carburized and quenched construction will likely be remodeled into new martensite through the influence of powerful grinding heat and also the cooling of coolant throughout grinding, which will induce the community volume enlargement over the area in the part, raising the tensile anxiety on the floor from the section and cause stress concentration. Continual grinding will simply speed up the grinding crack era.