Influence of bearing steel material on turntable bearing
The wide application of slewing bearings requires the production industry to continuously innovate product forms and improve product performance in product design. Because it’s main performance is closely related to product material selection, there are multiple considerations in manufacturing and material selection. Today, the editor will analyze and explain the influence of bearing steel materials on slewing bearings.
According to the working conditions of the slewing bearing, the material is selected. The slewing bearing that works at room temperature uses chromium bearing steel. The working temperature is higher than 150℃ and lower than 250℃, chromium bearing steel is also used, but it needs special heat treatment (200℃ or 300℃ tempering is required); According to the size of the impact load, the slewing bearing with strong impact load is generally selected. Do not use chromium bearing steel, most use high-quality carburized structural steel, impact-resistant tool steel or quenched and tempered structural steel.
The quality of steel determines the fatigue life and reliability of slewing bearings. Therefore, how to improve the performance of metal materials is an important entry point for the improvement and innovation of slewing bearings. The purity and uniformity of steel depend on the level of metal smelting and processing technology.
The bearing has the characteristics of long life, high accuracy, low heat generation, fast speed, good rigidity, low noise, and high wear resistance. Therefore, bearing steel is required to have: high hardness, uniform hardness, high elastic limit, and high contact fatigue. The strength of the atmospheric lubricant, the necessary toughness, a certain degree of hardenability and corrosion resistance. In order to meet the above performance requirements, the uniformity of the chemical composition of the bearing steel, the content and type of non-metallic inclusions, the size and distribution of carbides, and decarburization are strictly required. Bearing steel generally develops in the direction of high quality, high performance and diversification. Bearing steels are classified into high-carbon chromium bearing steels, carburized bearing steels, high-temperature bearing steels, stainless steel bearing steels and special bearing materials according to their characteristics and application environment.
Due to the characteristics of bearing steel, the requirements for smelting quality are much stricter than general industrial steel, such as the chemical composition, purity, structure and uniformity of the steel. Strict chemical composition requirements the general bearing steel is mainly high-carbon chromium bearing steel, that is, a hypereutectoid steel with a carbon content of about 1%, 1.5% of chromium, and a small amount of manganese and silicon. Chromium can improve heat treatment performance, improve hardenability, structure uniformity, tempering stability, and can also improve steel’s rust resistance and grinding performance. But when the chromium content exceeds 1.65%, after quenching, it will increase the retained austenite in the steel, reduce the hardness and dimensional stability, increase the unevenness of carbides, and reduce the impact toughness and fatigue strength of the steel. For this reason, the chromium content in high carbon chromium bearing steel is generally controlled below 1.65%. Only by strictly controlling the chemical composition of the bearing steel can the structure and hardness that meet the bearing performance be obtained through the heat treatment process.
For general use occasions, ordinary bearing steel smelted in acid open hearth furnace or alkaline electric furnace is often used. With the continuous improvement of smelting methods, new smelting methods such as current remelting, vacuum smelting, and electron beam furnace smelting have emerged. The life of the slewing bearing made of bearing steel smelted by the above method has been correspondingly improved.
Due to the continuous changes in bearing working conditions, especially the rapid development of science and technology, the working environment of machines has become more and more complicated. For example, the speed of the shaft is getting faster and faster, the load is getting heavier and the working temperature is getting higher and higher, the bearing becomes more and more complicated (except for gravity, there is also multidirectional thrust). All of these require the bearing to be competent, and the support shaft can operate stably as required. Therefore, bearing steel must keep up with the development of the times and technology in terms of strength, rigidity, wear resistance, hardness, uniformity of physical and mechanical properties, and contact fatigue strength function.