Abstract: A method for preventing loosening of a bolt fastened to a metallic member coated with an anticorrosive paint film without removing the paint film. Anticorrosive painting is applied on a metallic member, and then the painted film is thinned by applying an urging pressure onto a bolt seat surface portion of the painted metallic member by means of a press rod. The bolt seat surface portion of the metallic member also may be flattened by applying an urging pressure on the bolt seat surface portion by means of a press rod or by machining the bolt seat surface portion before the anticorrosive painting is applied on the metallic member, and then the painted film is thinned by applying an urging pressure onto the above-mentioned bolt seat surface portion by means of a press rod.

Abstract: Conventionally, heat treatment was necessary in the final stage of producing nodular cast iron products to give the nodular cast iron with desired mechanical properties. This was necessary because of the loss of graphitization capability of the molten metal when it is being formed into nodular cast iron during the process of spheroidization, and the heat treatment is therefore required to decompose cementite formation and thereby promote graphitization. The process of producing nodular cast iron according to the present invention can achieve the promotion of graphitization and the increase in the number of graphite nodules, which are both important for the production of high-quality thin-shell cast iron products, through the synergetic effect of processing the molten metal with a graphitization agent such as SiC or CaC.sub.2 and of adding a graphite atomization agent such as Bi.

Abstract: Nodular cast iron having favorable mechanical properties, in particular a high impact strength at low temperatures, comprising: from 3.0 to 4.0% of carbon; from 1.5 to 2.3% of silicon; less than 0.3% of manganese; not more than 0.03% of phosphorus; less than 0.10% of chromium; from 0.02 to 0.06% of magnesium; and from 0.0015 to 0.0150 weight % of bismuth with the balance consisting of iron and inevitable impurities and the CE (carbon equivalent) value being from 3.9 to 4.6%. This material is characterized by a low silicon content. Adding from 0.5 to 2.0% of nickel thereto improves its tensile strength and yield strength. Preferably, from 0.005 to 0.03% of bismuth is added to this nodular cast iron in molten state so as to produce more than 300 graphite nodules per mm.sup.2. The remaining bismuth content is preferably from 0.0015 to 0.015%, more preferably from 0.0015 to 0.004%.