Worm is an important Portion of device Resource rotating sections. Worm spiral area and worm gear tooth surface slip rather when Operating, that is easy to don. For that reason, the worm will usually carburizing quenching treatment to acquire higher hardness to forestall worm spiral surface area put on. Worm pieces call for large precision, And so the processing technological know-how is advanced and extended. When there is any dilemma in the course of processing, it will bring about large decline. A type of worm sections in our corporation appeared grinding cracks in the course of grinding, causing components scrapped, very seriously impacting the creation plan.
1. Worm content and most important course of action move
The worm content is 20CrMnTiH and the warmth treatment method calls for carburizing and quenching using a depth of 1.1-1.5mm along with a area hardness of 58HRC just after quenching.
Blanking→Forging→Normalizing→Rough machining→Pressure decrease→Great machining→carburizing→Carbon take out to the thread→Quenching→Tough grinding→Check→Aging→Great grinding
Warmth remedy method: Forging normalizing→ Carburizing →Quenching →Low temperature tempering →Straightening→Tension reduction→Small temperature growing old.
Just after carburizing and quenching, the carburized depth layer is one.32mm and the floor hardness is fifty nine to 60HRC.
2. Crack phenomenon description
Immediately after rough grinding, the crack appears on the tooth floor with the worm. The cracks are quite high-quality, linear and shallow in depth. The form with the cracks is usually termed "hairline". The cracks are certainly not parallel and scattering lines.
three. Assessment of grinding cracks
It is obviously diverse from popular quenching cracks. The quenching cracks are thick and deep, and the number of cracks is little. It only occurs around the grinding surface area, and also the quantity is huge, the depth is shallow, but the depth is basically the same. The lighter kinds are stripe cracks perpendicular to or approximately perpendicular towards the grinding path. The worm tooth surface area is often a spiral surface.
Inside the grinding strategy of heat-taken care of pieces, the instantaneous superior temperature in the grinding zone can attain 400-1500 ℃ because the grinding wheel is blunt, the grinding depth is simply too deep as well as the cooling is inadequate. Because of this, the grinding burn up occur, leading to the improvements of more info floor microstructure, microhardness, residual anxiety and mechanical properties of your areas.
The development of cracks is linked to the hardness from the workpiece. Although the workpiece with hardness below 55HRC may be burned, the prevalence of grinding cracks is scarce. The workpiece with hardness over 60HRC will considerably improve the opportunity of crack. The measured hardness in the section is 59 ~ 60HRC, which greatly increases the inclination of grinding cracks. Over the a single hand, when grinding conditions are inappropriate or grinding is not really normal, grinding area will First of all sort a strong burn off Centre, causing uneven thermal worry. In alternate superior temperature and fast cooling, the anxiety price progressively enhanced. If the stress exceeds the fabric energy limit, the grinded area will develop cracks. However, the retained austenite from the surface carburized and quenched framework will probably be transformed into new martensite via the impact of powerful grinding warmth and also the cooling of coolant throughout grinding, which will induce the community volume enlargement within the area on the component, raising the tensile anxiety within the surface in the part and lead to strain concentration. Continual grinding will quickly accelerate the grinding crack technology.