The quality of the heat treatment is directly related to the quality of subsequent processing and eventually affect the performance and life of parts, while heat is energy guzzler and polluters machinery industry. In recent years, with the advancement of science and technology and its development in terms of the application of heat treatment, heat treatment technology is mainly reflected in the following aspects:
(1): Heat treatment: waste water formed during heat treatment, polluting emissions, waste salt, dust, noise and electromagnetic radiation on the environment etc. Solve the heat problem of environmental pollution, the implementation of clean heat (or green heat) is one of the direction of the development of heat treatment technology developed. In order to reduce SO2, CO, CO2, and cinder dust emissions, has basically put an end to the use of coal as a fuel, the amount of heavy oil less and less in favor of the majority of light oil, natural gas is still the best fuel. Furnace waste heat utilization has reached a high degree of optimization and air burner structure - strictly controlled to ensure that the fuel ratio combustion reasonable premise that NOX and CO reduced to a minimum; the use of gas carburizing, carbonitriding and vacuum heat treatment technology to replace the salt bath treatment to reduce waste and toxic pollution of CN- containing water; water-soluble synthetic oil instead of part of the quenching quenching oil, the use of biodegradable vegetable oil instead of part of the mineral oil to reduce oil pollution.
(2): Precision heat: precision heat treatment has two meanings: one is based on the requirements of parts, materials, structure size, the use of physical metallurgy knowledge and advanced computer simulation and testing technology, optimize the process parameters to achieve the required performance or to maximize the potential of materials; on the other hand is fully guarantee the stability of the process optimization, and product quality dispersity small (or zero) and heat distortion zero.
(3): Energy-saving heat: scientific production and energy management is the most efficient use of energy has the potential factors that a professional heat treatment plant in order to ensure full capacity, full equipment capacity is scientific management options. In terms of heat energy structure, preference primary energy; full use of waste heat, waste heat; using low energy consumption, long cycle process instead of a short period, a large energy-consuming processes.
(4): no oxidation heat treatment: protective atmosphere by using alternative heating oxidizing atmosphere heated to precisely control the carbon potential, nitrogen potential of controlled atmosphere heat after heat treatment improved the performance of the parts, heat treatment significantly reduced defects such as decarbonization, cracks, etc. finishing allowance reduced after heat treatment, to improve the utilization efficiency of the material and machining. Vacuum heating gas quenching, vacuum or low pressure carburizing, nitriding, nitrocarburizing and boron penetration can significantly improve quality, reduce distortion and improve life.
Bearing parts heat treatment quality control in the whole machinery industry is the most stringent. Bearing heat treatment in the past 20 or so years has made great progress, mainly in the following areas: basic theory study heat; heat treatment process research and application of technology; the development of new heat treatment equipment and related technologies.
A high carbon chromium bearing steel annealing: ball annealing carbon chromium bearing steel is to obtain a uniform distribution of the fer-rite matrix with fine, small, uniform, organized a round carbide particles for subsequent cold and final The quenching and tempering for tissue preparation. The traditional ball annealing process is slightly above Ac1 temperature (eg GCr15 is 780 ~ 810 ℃) after incubation with the furnace cooled slowly (25 ℃ / h) to below 650 ℃ cooled baked. The process heat for a long time (20h or more), and after annealing carbide particles uneven, cold and final micro structure and properties of quenched and tempered later. After that, according to the characteristics of super cooled austenite transformation, development isothermal ball annealing process: rapid cooling after heating to a certain temperature range below Ar1 (690 ~ 720 ℃) isothermal, isothermal austenite to complete the process transformation of fer-rite and carbides can be directly after the transition is completed cooled baked. The advantage of this process is to save the heat treatment time (the whole process about 12 ~ 18h),; tissue treated in small uniform carbide. Another time-saving process is repeated ball annealing: first heated to 810 ℃ cooling to 650 ℃, and then heated to 790 ℃ to 650 ℃ baked cooled cooling. Although this process can save some time, but the process operation is more complicated.