Papers by Author: Chong Lin Wang

Abstract: Fe-4Ni-0.5Mo-1Cu powder was selected as raw material, pressed and sinter-hardened at 1135°C for 30 min with rapid cooling. The density varies in the range of 7.24-7.29 g/cm3. Its fatigue properties have been tested in axial loading of alternating tensile/compressive stress at R=-1 with a servo-pulse pump. The fatigue endurance limit was measured to be 260 MPa. The microstructure showed more homogeneous bainite and martensite. Neither Ni nor Mo rich areas were detected. Fractography displayed the fatigue cracks initiated from the pore areas near the surface. A nontypical ductile fatigue striation was found. More dimples occurred on fracture surface due to the plastic deformation, which can prohibit cracking propagation and improve its fatigue properties.

Abstract: X-ray analysis on iron ores and reduced iron powders revealed that around 60% acidinsoluble substances were hexagonal and tetragonal quartz, another 40% substances were sillimanite, alumina-silicate, an unnamed zeolite, all contained Si and Al. SEM images displayed that the particle size of them was in the range of 3~7 μm, which may be the initial source of the cracking in the sintered body. Statistics analysis showed that the Acid-Insoluble Content (AIC) for high-grade magnetite powder was (0.130±0.010) % during the latest five months. The predicting value for reduced iron powder from ore powders should be 0.179 %. However, the testing value for reduced iron powder was (0.192±0.014) %. The limited difference of 0.013% might imply rare pollution coming from the reduction and milling processes. The most important step for control AIC should be the separation process of iron ore powders.

Abstract: The error function can be calculated based on the Simpson method through a subroutine program. An integration program by FORTRAN language was made for diffusion equations of extended source with infinite extent and limited extent. The distribution curves of alloying elements could be driven from calculated results written in ASCII code. The results on some alloying elements such as C, Co, Cr, Mn, Mo, Ni and V’s diffusion in iron, showed the diffusion distance for Ni and Mo can only be 1~3 μm and more distance for Co at common sintering temperature of 1120°C. Increasing the sintering temperature up to 1300°C, distribution curve could be improved. To refine the particle size of the added elements down to a scale of micrometers is an effective way to get homogeneous distribution.