Process Measures for Gear Crack of Grinding Machine

The more sensitive the material to the grinding crack, the more prone to cracks in the grinding, reduce the material to the degree of grinding crack sensitivity, the probability of grinding crack will be reduced, this sensitivity due to the carburizing heat treatment process specifications vary, can be changed by carburizing, quenching, tempering process for appropriate control and reduction. Therefore, the grinding machine gear will take the following measures, then the following together to understand the grinding machine gear crack process measures!

Reduce the quenching temperature of carburized parts: the gear processed by 20CrMnTi is carburized in 930, and the gear is directly quenched after carburizing. From the quenching temperature 860 down to 830, but also without changing the grinding conditions to eliminate the more serious grinding cracks. The surface carbon concentration should be appropriate, and the carbon concentration should be controlled within the range of 0.7 to 0.9. The carbon concentration distribution gradient should be smooth to ensure good surface strength and stress distribution. The carbon content of heavy-duty gears must be controlled at a lower limit, which is beneficial to control the size and shape of the carbide. When the carbon content is controlled to the upper limit, the tendency to form residual austenite is enhanced, carbides increase, surface oxidation and tooth root strength decrease. According to relevant information, the carbon concentration on the surface of heavy-duty gears in the United States has been controlled at about 0.65%.

The more inadequate the tempering, the higher the grinding crack sensitivity. Therefore, in order to improve the plasticity of the carburized quenching surface, balance or reduce the residual stress, improve the distribution of surface stress, it is necessary to carry out sufficient tempering. The probability of occurrence of grinding cracks can be reduced. Control the amount of residual austenite, to prevent the gear during grinding tissue conversion, resulting in a larger tissue stress, strictly control the residual austenite within 25%, the important gear control within 20%.

Grinding machine gears mainly control the size, quantity, shape and distribution of carbides to obtain dispersed particulate carbides, thereby improving the fracture strength of the material, reducing brittleness, controlling martensite grade, obtaining recessive crystalline and fine acicular martensite, coarse acicular martensite martensite grade three is better, and necessary technical measures are taken to control heat treatment deformation.

Technical Measures for Gear Processing of Grinding Machine

The average temperature of the contact area between the grinding machine gear and the tooth surface is generally 500-800, the temperature of the abrasive grinding point can reach 1000, and more than 80% of the heat is transferred to the gear. Due to the large amount of grinding heat generated during brushing, the tooth surface grinding area is subject to large thermal stress and thermal expansion and contraction deformation. When the grinding heat cannot be effectively controlled, the tooth surface is prone to grinding cracks and grinding, therefore, the focus of the process countermeasures in machining is how to reduce and control the grinding heat.

The grinding machine gear should reduce the tooth surface roughness during hob cutting, which should be controlled within Ra3.2 ~ Ra6.3. The common normal margin during hob cutting should be strictly controlled. It is not allowed to increase the hob cutting margin at will to minimize the thermal deformation error after heat treatment. The process requires that before brushing, the tooth surface must be planed with hard tooth surface rolling technology to make the tooth margin uniform, greatly reducing the tooth margin, I .e. greatly reducing the grinding heat, reasonable selection and matching of cutting parameters. The selection principle is that the grinding wheel has high speed, fast stroke and reasonable feed.

The choice of grinding machine gear is an important part of brushing. Whether the grinding wheel is selected appropriately has a great influence on the accuracy and efficiency of brushing. Improper selection of grinding wheel hardness, particle size and organization can easily cause tooth surface and grinding cracks. Therefore, we must choose from the following aspects:

Abrasive: (symbol PA) red chrome corundum, chrome corundum hardness close to white corundum, toughness is better than white corundum, toughness of steel with chrome corundum grinding. It is preferable because of its higher efficiency than white corundum, and the durability of the grinding wheel and the roughness of the grinding surface.

Binder: The material from which the abrasive grit is made. At present, the grinding wheel adhesive is basically a ceramic adhesive. The ceramic adhesive has stable performance, water resistance and heat resistance, can adapt to the grinding of various coolants, and is inexpensive.

Hardness: The harder the grinding wheel, the worse the porosity. The gap between the abrasive particles is immediately blocked by the abrasive particles during the grinding process. The grinding wheel with high hardness has poor self-sharpness, and the blunt abrasive particles are not easy to fall off, causing wear between the grinding wheel and the surface of the workpiece. The phenomenon affects heat dissipation, increases grinding heat, and produces cracks.

The above is the grinding machine gear crack process measures, if you need to know more, you can contact us at any time!