Worm is a crucial Section of machine tool rotating pieces. Worm spiral floor and worm gear tooth floor slip somewhat when Functioning, that's simple to don. Hence, the worm will often carburizing quenching cure to acquire higher hardness to prevent worm spiral area don. Worm areas call for significant precision, Therefore the processing technology is elaborate and prolonged. If there is any issue for the duration of processing, it will eventually induce major decline. A form of worm pieces in our business appeared grinding cracks for the duration of grinding, causing pieces scrapped, very seriously impacting the manufacturing routine.
one. Worm product and primary procedure flow
The worm product is 20CrMnTiH and the warmth therapy involves carburizing and quenching that has a depth of 1.1-one.5mm plus a surface area hardness of 58HRC right after quenching.
Blanking→Forging→Normalizing→Tough machining→Strain decrease→Fantastic machining→carburizing→Carbon get rid of about the thread→Quenching→Tough grinding→Take a look at→Getting old→Fine grinding
Heat procedure system: Forging normalizing→ Carburizing →Quenching →Reduced temperature tempering →Straightening→Worry relief→Very low temperature getting older.
Following carburizing and quenching, the carburized depth layer is one.32mm and the surface hardness is 59 to 60HRC.
2. Crack phenomenon description
After rough grinding, the crack appears about the tooth floor of the worm. The cracks are quite great, linear and shallow in depth. The shape from the cracks is normally identified as "hairline". The cracks are usually not parallel and scattering strains.
three. Evaluation of grinding cracks
It is obviously various from typical quenching cracks. The quenching cracks are thick and deep, and the volume of cracks is modest. It only occurs around the grinding surface, and the selection is significant, the depth is shallow, but the depth is essentially the identical. The lighter kinds are stripe cracks perpendicular to or almost perpendicular to the grinding course. The worm tooth area is often a spiral surface area.
Inside the grinding technique of warmth-taken care of pieces, the instantaneous large temperature inside the grinding zone can get to 400-1500 ℃ since the grinding wheel is blunt, the grinding depth is just too deep as well as cooling is insufficient. Due to this fact, the grinding melt away take place, causing the modifications of surface area microstructure, microhardness, residual tension and mechanical Homes of your elements.
The development of cracks is relevant to the hardness of your workpiece. Although the workpiece with hardness a lot less than 55HRC could be burned, the occurrence of grinding cracks is rare. The workpiece with hardness earlier mentioned 60HRC will considerably boost the possibility of crack. The calculated hardness of your section is fifty nine ~ 60HRC, which greatly increases the inclination of grinding cracks. About the a single hand, when grinding disorders are incorrect or grinding isn't typical, grinding surface will firstly form a powerful burn off center, leading to uneven thermal anxiety. In alternate higher temperature and immediate cooling, the strain value gradually enhanced. When the pressure exceeds the material click here power Restrict, the grinded area will generate cracks. However, the retained austenite from the area carburized and quenched construction are going to be transformed into new martensite with the impact of intense grinding heat and also the cooling of coolant through grinding, which will trigger the regional quantity growth to the area of your component, growing the tensile anxiety within the surface area in the element and cause pressure concentration. Steady grinding will very easily accelerate the grinding crack technology.