Energy shortage has become a prominent problem restricting the sustainable development of China's automobile industry. Considering the social and economic benefits, cars with low energy consumption and low emissions are the final demand for the development of a conservation-oriented society. Lightweight technology is an important means of energy saving for heavy vehicles. Heavy duty vehicles using variable section less leaf springs can reduce the mass of the spring assembly by 30% to 50%. Since the weight of leaf spring is inversely proportional to the square of the design full load static stress, developing materials with higher toughness to improve the design full load static stress of leaf spring is the most effective way to achieve the lightweight of leaf spring. The improvement of design full load static stress of leaf spring requires higher material and manufacturing process. This paper mainly describes the technical scheme of niobium plate spring material, material trial production and performance test, material structure and strengthening and toughening mechanism and other fatigue performance research and application, mainly through the bench and road test of fewer sheet springs. It is proved that the niobium material has high strength, high plasticity and good rolling property, which makes it a good material for less sheet spring used in heavy vehicles.
The research data show that the fuel consumption of commercial vehicles decreases by 4%~6% when the readied quality of commercial vehicles decreases by 10%, and the automobile plate springs account for 5%~7% of the dead weight of passenger and cargo vehicles. Therefore, the lightweight of commercial vehicles is of great significance to save materials, save energy and further reduce transportation costs. According to the current development situation of the domestic automobile market, in the next few years, the domestic demand for plate spring steel will be more than 1.25 million tons.
The development trend of plate spring steel is not only high strength and toughness, but also high fatigue life, high hardenability, excellent elastic damping resistance and good economy. The mechanism of alloy strengthening mainly includes microstructure strengthening and precipitation strengthening. Microstructure strengthening can improve the strength of steel plate by adding a certain amount of hardenability elements, combining controlled rolling and controlled cooling to obtain the transformation microstructure of medium and low temperature. This kind of steel has excellent comprehensive performance, but the production cost is high due to the addition of precious alloy. Precipitation strengthening mainly adds high titanium and micro niobium vanadium microalloying elements, and strengthens ferrite matrix through carbonitride precipitation, thus improving the strength. Precipitation strengthening steel has lower cost and better formability, but its toughness is slightly worse than that of low carbon bainite steel.
