Process analysis of heat treatment of 65Nb steel log chipper using medium frequency induction heating power supply

The chipper knife, as we can see from its name, is mainly used for cutting. Therefore, during the working process, the chipper knife has to withstand huge friction. In order to improve its wear resistance, many manufacturers use medium-frequency induction heating power to heat treat chipper knives, and the effect is very good. Today, the editor will tell you about the medium frequency induction heat treatment process of 65Nb steel log chipper.

The quality of the chipper blade on the log chipper directly affects the production efficiency of the chipper and the quality of the chips. In the past, chipper knives were mainly made of 6CrW2Si steel, which had low durability and seriously affected the production efficiency of the chipper, becoming a key issue for paper mills. Since the introduction of 65Cr4W3Mo2VNb (65Nb for short) steel blades, years of production practice have proven that the results are good.

The chipper knife made of 65Nb steel has specifications of 817mmX147mmX12.7mm and weighs 9kg. The manufacturing process is: forging-rolling-annealing-machining-quenching and tempering-grinding. An intermediate frequency heating power supply is used for heat treatment. The induction heating temperature is 1120℃, the heating coefficient is 15-20s/mm, oil quenching, and tempering at 580℃X2hX2 times. The hardness after tempering is about 58HRC. When cutting masson pine logs with a diameter of 400-500mm, the service life is nearly twice that of a 6CrW2Si steel blade. The sharpness and chipping of the blade are better than imported knives.

Under normal heat treatment, the strength of 65Nb steel is increased by 40% and the toughness is increased by 4 times compared with M2 steel. This is because excess carbides are less and evenly distributed. During the tempering process at 540-560°C, dispersed MC and M2C carbides precipitate, resulting in secondary hardening, and the peak hardness can reach 62-63HRC. On the tempered martensite matrix, dispersed undissolved carbides are evenly distributed, which provides structural guarantee for obtaining high strength and wear resistance. The presence of a small amount of niobium compounds hinders the growth of austenite grains, improves hot workability and toughness. Depending on the working conditions of the chipper. The mature heat treatment process is: the suitable quenching temperature is 1100-1120℃, the tempering temperature is about 580℃, and the hardness after tempering is about 58HRC.