Microstructural changes in As— Cast M2

High speed steels have a complex carbide pattern in the as-cast state which has to be modified to achieve the desired properties of adequate toughness, hot hardness, and wear resistance. The effects of hot forging and postdeformation annealing on carbide distribution and morphology in M2 grade high speed steel were studied, and it was shown that hot forging accelerates the spheroidization rate of M₆C carbide with little effect on coarsening. The mechanism responsible for such acceleration is dominated by mechanical disintegration of M₆C carbide plates, while diffusion-controlled spheroidization was not significant. For MC carbide particles, coarsening was the dominant mechanism, but it was not possible to ascertain whether diffusion had been unaffected by deformation or even increased by a factor that could be as high as 10,000 times. Annealing after deformation accelerated spheroidization which was attributed to the damaging of carbide plates during forging rather than an increase in diffusion rate, since the matrix was almost substructure-free in the annealed condition,i.e., lack of short-circuiting paths for diffusion.     

锗富集物中硫、砷及二氧化硅的控制

针对高硫、砷二氧化硅等优劣质原料中提取锗的过程中出现的质量问题，进行了除硫、砷及硅的研究。结果表明，采用高温除硫、氧化除砷及二段除硅效果显著，从而确保了锗富集物的质量达标。     

Pressure oxidation kinetics of orpiment (As2S3) in sulfuric acid

Pressure oxidation kinetics of a massive orpiment (As₂S₃) sample in sulfuric acid solution were systematically investigated. The effects of temperature (170 to 230 °C), mean particle size (48 to 125 μm diameter) and oxygen partial pressure (345 to 1035 kPa) were evaluated. Oxidation rates were found to be affected significantly by changes in temperature and particle size, but were relatively insensitive to changes in oxygen partial pressure. Kinetics appear to be controlled by product layer diffusion over the temperature range of 170 to 210 °C, due to the formation of elemental sulfur on particle surfaces. However, Arrhenius activation energies over this range are large (> 40 kJ/mol) and increase with decreasing temperature, perhaps reflecting the kinetics of sulfur oxidation rather than diffusion. Above 210 °C the rate-controlling step is a surface reaction with an activation energy of approximately 33.8 kJ/mol. The reaction order at 210 °C is approximately 0.2 with respect to oxygen partial pressure.