Abstract: Disclosed is a corrosion resistant steel having good machinability with sufficient corrosion resistance in the ordinary indoor circumstances and suitable for manufacturing shafts of various small motors and OA-machines. The steel comprises, by weight %, C: 0.005-0.200%, P: up to 0.05%, Cu: up to 2.0%, Ni: up to 2.0%, Cr: 2.0-9.0%, one or both of Ti and Zr: in such an amount as [Ti%]+0.52[Zr%]: 0.03-1.20%, one or both of S: 0.01-0.50% and Se: 0.01-0.40%, N: up to 0.050% and O: up to 0.030%, the balance being Fe and inevitable impurities. The steel is characterized by the inclusion therein, which are Ti-based, Zr-based or Ti—Zr-based compound or compounds containing C and one or both of S and Se.

Abstract: A free-cutting Ni-base heat-resistant alloy excellent in the high-temperature strength and corrosion resistance was proposed. The alloy contains Ni as a major component, 0.01 to 0.3 wt % of C and 14 to 35 wt % of Cr, and further contains at least one element selected from Ti, Zr and Hf in a total amount of 0.1 to 6 wt %, and S in an amount of 0.015 to 0.5 wt %. The alloy has dispersed in the matrix thereof a machinability improving compound phase, where such phase contains any one of Ti, Zr and Hf as a major constituent of the metal elements, essentially contains C and either S or Se as a binding component for such metal elements. The alloy also satisfies the relations of WTi+0.53WZr+0.27WHf>2WC+0.75WS and WC>0.37WS, where WTi represents Ti content (wt %), WZr represents Zr content (wt %), WHf represents Hf content (wt %), WC represents C content (wt %) and WS represents S content (wt %).

Abstract: A medium-carbon steel is provided having a dispersed fine spherical graphite structure, having high mechanical strength, good processability, and good machinability, and having fine ZrC functioning as nucleation sites for graphite. The medium-carbon steel having a dispersed fine spherical graphite structure is manufactured by providing a composition containing 0.1 to 1.5% Si, 1.0% or less C, and 0.01 to 0.5% Zr. After the composition or a material of the composition (ingot) has been hot-rolled, or after the hot-rolled steel has been heat-treated at 750 to 1300° C. for 0.5 to 10 hours (solution heat treatment) after hot-rolling, or after the hot-rolled and heat-treated steel has further been water-quenched to deposit fine ZrC particles in the matrix, the steel is subjected to graphitization treatment by heat-treating at a temperature of 740° C. or below for 0.5 to 100 hours to grow graphite using ZrC as the nucleation site.