Yasutaka Okada

Effect of Heat Treatment on the Susceptibility to Stress Corrosion Cracking of Alloy 600

It was shown that a modified Huey test, i.e., a 24-h immersion in boiling 40% HNO3, is able to exactly detect the susceptibility to intergranular corrosion of Alloy 600, which is correlated with intergranular stress corrosion cracking (IGSCC) behavior in high temperature water containing small amounts of chloride ions. Chromium content at the regions adjacent to grain boundaries in sensitized Alloy 600 was analyzed as ~3% by the measurement of magnetic susceptibility.Heat treating Alloy 600 at low temperatures, e.g., at 700°C for 15 h, improves the IGSCC resistance to both high temperature water and caustic solutions by constructing suitable microstructures resistant to sensitization, in which chromium carbides precipitate predominantly in the matrix instead of grain boundaries.

Role of alloying elements on machinability of plastic-molding steels

Abstract The influence of silicon and other alloying elements of plastic-molding steels on machinability in face-milling and ball-nose end-milling was investigated. Increase of silicon content decreased the adhesion of chips to a tool and as a result, tool life increased in a dry cutting condition. Vanadium had a similar effect, especially at relatively low cutting speed. To understand these phenomena, the chip surface was analyzed. From these results, it is proposed that low melting temperature oxides of the Fe–Si–O and Fe–V–O systems are formed on the chip surface of high-silicon steel and vanadium-added steel; these oxides lubricate the interface between chip and tool. On the other hand, manganese and chromium that on believed to are form the Fe–Mn–O and Fe–Cr–O oxide film of high melting temperature reduced the lubrication effect. Carbon also decreased tool life due to an increase of pearlite, while the addition of sulfur did not influence tool life.