スプリング用素材の表面処理工程における水素量と遅れ破壊との関係

Abstract

Without surface treatment carbon steel rusts, and drastically reducing its lifetime. Springs of carbon steel are thus generally zinc-plated or painted to prevent anticorrosion and thus maintain their function. Such treatment results in considerable hydrogen absorption, however, causing hydrogen brittleness and consequent intergranular fracturing and delayed fracturing. Because the rate of hydrogen diffusion is so high, quantitative analysis is extremely difficult, so that much remains to be clarified in the relationship between hydrogen content of the steel and delayed fracturing at the various stages of zinc-plating.It was therefore decided to investigate the relationship between the amount of hydrogen absorption and the delayed fracturing of carbon steel springs, with emphasis on pickling, zinc-plating thickness and baking.Results were as follows.(1) Hydrogen content increased during pickling and zinc-plating.(2) When zinc-plating thickness was adequate, no significant decrease in the total amount was produced by baking.(3) Delayed fracturing was influenced by structure, and did not occurr in specimens subjected to Austempering.Breakage rates were reduced to 0% in the lower hardness range.