Analysis of Microstructure Characteristics and Precipitation Behavior of Automobile Beam Steels Produced by Compact Strip Production

The microstructure characteristics and precipitation behavior of automobile beam steels produced by compact strip production (CSP) were investigated by use of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy. The result shows that the final microstructure is mainly composed of polygonal ferrite and small amount of pearlite, and the average ferrite grain size is about 3—6 μm. Small amount addition Ti to aluminium-killed steel can help to refine the microstructure and improve the mechanical properties. A large number of fine precipitates have been observed in automobile beam steels. The mean particle size is about 10—30 nm. Remarkable strengthening and grain refinement can be obtained by these nano-particles.