The main purpose of carburizing heat treatment for aluminum alloy automotive parts is to achieve good fatigue resistance and wear resistance of the parts, ensuring the reliability of their performance. The heat treated parts strengthened by carburization and quenching include differential gears of automotive drive axles, gear parts of transmission shafts, gear parts of steering shafts, engine piston pins, and gear parts.
The carburizing heat treatment equipment for automotive parts mainly includes box type multi-purpose furnaces, single row, double row, and multi row continuous furnaces, vacuum (low-pressure) carburizing high-pressure gas quenching furnaces, etc. Over the past decade, the important symbol of the development of carburizing heat treatment technology is the application of sensing technology and computer technology in production. The carburizing heat treatment process parameters, such as temperature, time, carbon potential, quenching process, and action program, can be fully automatically controlled by the system. Even based on the technical requirements, material grades, and characteristics of the parts, the process can be automatically generated to achieve intelligent control.
Quenching and tempering heat treatment
The quenching and tempering heat treatment of automotive parts can be divided into protective atmosphere quenching and tempering heat treatment and general quenching and tempering heat treatment. Protective atmosphere heat treatment can ensure that the parts will not produce surface oxidation, decarburization and other defects during the heat treatment process, ensuring the surface quality of the parts. When the working surface of the parts after quenching and tempering treatment requires subsequent processing, general heat treatment is used. According to the quality and size of the parts, the quenching and tempering heat treatment equipment includes mesh belt furnace, casting chain furnace, material tray (basket) push rod furnace, bracket furnace, suspended continuous furnace, etc.
Induction heat treatment
Compared with general furnace overall heating heat treatment, induction heat treatment has the following characteristics:
(1) According to product performance requirements, only surface or local heating is applied to the parts, and surface or local strengthening is implemented, thus it is an energy-saving heat treatment.
(2) The production process is pollution-free and undergoes clean heat treatment.
(3) Induction heating has a short heating time and fast speed, which is conducive to refining the quenched structure and obtaining a strengthening effect with excellent wear resistance and torsional bending fatigue resistance.
(4) The induction quenching device can be conveniently installed on a production line, facilitating production management and reducing logistics costs.
(5) Induction quenching production has a fast pace, high efficiency, and can achieve complete automation.
The characteristics of induction heat treatment make induction quenching technology widely used in the production of automotive parts. At present, the automotive parts that implement induction hardening mainly include automotive shaft parts that transmit power torque, such as crankshafts, half shafts, spline shafts, transmission shafts, camshafts, and various pin shaft parts.
Forging waste heat heat treatment
Most automotive structural parts are formed using hot forging technology. How to utilize forging waste heat to implement heat treatment of blanks is an important energy-saving measure. If forging waste heat isothermal annealing and forging waste heat quenching are used, the necessary structure and hardness for subsequent processing can be obtained, eliminating the energy consumption of reheating and heat treatment, and the energy-saving effect is very significant. The parts that use forging waste heat for heat treatment include various types of gear blanks, front axles, steering knuckles, rocker arms, spline shafts, crankshafts, connecting rods, etc. In order to ensure the uniformity of microstructure and hardness in the waste heat annealing of gear blanks, it is necessary to strictly control the final forging temperature, intermediate cooling process, isothermal temperature, etc. To ensure the strength and toughness of parts quenched by waste heat, in addition to direct quenching process, pre cooling to 550-650 ℃ can also be used to complete pearlite transformation and then reheat to austenitization temperature. The main purpose is to refine the organization and achieve good toughness performance.
Annealing free cold heading steel and non quenched and tempered steel
Generally, in order to ensure the cold forming performance of cold heading steel, the material needs to undergo spheroidization annealing treatment in advance. The so-called annealing free cold heading steel refers to adjusting the chemical composition of the cold heading steel, controlling the rolling and cooling technology during the rolling process, making the pearlite partially spheroidized and deformed, reducing the deformation resistance during the cold forming process, and can be directly used for cold heading forming. Due to the absence of spheroidization annealing, it not only has significant energy-saving effects but also shortens the production cycle, making it an energy-saving and economical new material.
Non quenched and tempered steel, due to the addition of trace amounts of strong carbon (nitrogen) compound forming elements (V, Nb, Ti, etc.) in the steel, undergoes precipitation strengthening and grain refinement during forging and controlled cooling after forging. Its strength and toughness performance can reach or be close to that of quenched and tempered steel, and it eliminates the need for quenching and tempering heat treatment, reduces a large amount of energy consumption, and has good processing performance. It has received attention from many domestic and foreign automobile manufacturers. Such as Mercedes Benz and Volkswagen from Germany, Volvo from Sweden, Aust in from the UK, and G. from the United States M. Ford Motor Company and Italian Fiat Motor Company extensively use non quenched and tempered steel to manufacture important components such as engine crankshafts, connecting rods, and front axles. Japan is at the forefront of the world in the research and application of non quenched and tempered steel. For example, Mitsubishi Motors uses almost all non quenched and tempered steel for its steering and transmission systems, while Nissan and Mitsubishi Motors use almost all non quenched and tempered steel for their crankshafts and connecting rods. For over a decade, Dongfeng Motor Company has been using non quenched and tempered steel to produce crankshaft, connecting rods, front axles, steering knuckles, and other parts of automobiles. With an annual consumption of tens of thousands of tons of non quenched and tempered steel, it has produced millions of automotive parts such as crankshafts, connecting rods, and front axles, achieving significant economic and social benefits.
Automotive parts heat treatment application equipment
Heat treatment has become an indispensable and increasingly important processing method in modern industry. Therefore, the development of induction heating equipment is also growing day by day. Choosing good heating equipment can make work more efficient and efficient. The commonly used heat treatment equipment for automotive parts in industry includes the following types.