Overview of Heat Treatment and Surface Strengthening Technologies for Bimetal Band Saw Blades
With the development of sawing to high efficiency, high hardness material, long life, low cost and automation, the bimetallic band saw blades not only require higher abrasion resistance and red hardness of the cutting edge, but also require the back material to have higher strength and good fatigue resistance to match. Therefore, it is of great theoretical and practical significance to study how to improve the fatigue resistance and sawing life of the back material in the ultra-high-temperature quenching and high-temperature tempering condition.
Numerical simulation of induction heating and oxynitriding surface strengthening process in the tempering process of bimetallic band saw blades heat treatment can solve the current situation that the overall life of the saw blade decreases due to the lack of fatigue performance of the back of the saw and the wear resistance of the tooth tip existing in the current bimetallic band saw blades.
Induction preheating in the saw blade tempering process can greatly improve its productivity. Through numerical simulation, it is found that the size of the coil and the distance between the coil and the saw blade in the induction heating have a greater impact on the induction heating efficiency and temperature distribution uniformity of the saw blade. When the distance between the saw blade surface and the coil is certain, the length of the runway-type coil is increased, and the heating temperature distribution becomes more uniform, and the heating rate increases significantly by decreasing the distance between the coil and the blade.
When the distance between the saw blade surface and the coil is certain, the length of the runway-type coil increases, the heating temperature distribution is more uniform, reducing the distance between the coil and the saw blade, the heating rate rises obviously, and the shorter the length of the runway-type coil is, the more uniform the temperature distribution is, under the condition of a certain current of induction heating, the thickness of the coil has a greater influence on the heating efficiency and the distribution of the temperature, and the smaller the cross-sectional area of the coil is, the higher the heating rate is, and the better the distribution of the uniformity of the temperature is. In the case of coil thickness of 5mm, the heating efficiency of the specimen is higher when the distance between the specimen and the coil is 4mm, and the temperature distribution is uniform, which is conducive to its continuous induction preheating. In the saw blade tempering process of oxynitriding treatment, oxynitriding treatment gas flow on the thickness and performance of oxynitriding layer has little effect, so the experiments used 60 drops/min ammonia drops, oxynitriding stage of the pressure change in the furnace chamber on the thickness of the nitriding layer of nitriding layer is not significant, as long as to maintain a little more than one atmospheric pressure can be.
Through the test, it was found that the sawback material obtained under the oxynitriding process at 550℃×3h had good hardness, and the friction wear test was conducted, and it was found that the coefficient of friction was small and very stable after it entered into the stable wear stage, and the wear form was mainly oxidative and ploughing wear, and the thickness of the compound layer on the surface was measured by the electron microprobe, and the oxidative layer thickness was about 5 μm, and the thickness of nitriding layer was relatively thin only 1-2%, and the thickness of nitriding layer was only 1-2%. The thickness of the oxide layer was about 5 μm, while the thickness of the nitrided layer was relatively thin, only about 1-2 μm. At the same time, the hardness of the tooth tip M42 high-speed steel after oxynitriding heat treatment was tested, and it was found that its hardness increased significantly under the processes of 580℃×3h and 550℃×3h compared with that before oxynitriding, and its hardness reached 1100HV especially under the process of 550℃×3h. Considering the comprehensive mechanical properties of the saw blade back and tooth tip, it was decided to determine that the final 550℃×3h is the best heat treatment and tempering oxynitriding process. Nitriding process.
With the rapid development of the national economy and the country's basic industrial demand for metal cutting continues to increase, bimetallic band saw blade future market development space will be more and more broad.
