釣鉤の熱處理と破斷荷重

Abstract

In order to study and to improve the manufacturing process of the fish-hook, for which old proprietary experience has hitherto been consulted, we have carried out some experiments in the Physical Laboratory of the Imperial Fisheries Institute under the guidance of Dr. M. TAUTI. By means of a specially designed electric furnace, various thermal treatments were applied on about 3, 000 raw materials of similarly shaped bonito-book of 3, 4•5 or 5•4cm. in length, the heating temperature θ1 and the duration t1 having been changed in the range of 730° ?? -900°C and of 60 to 226 minutes respectively, while those of the annealing θ2 and t2, in the range of 200°-400°C and of 2-27 minutes respectively. Then, the breaking load, W, and the deforma-tion of the book were measured by means of Mori's tensionmeter also specially devised. The results are summarised as follows: - (1) In the range of θ1 of 780°-820°C and of θ2 of 250°-300°C, both of which are compara-tively high for 3cm. -hook and low for 4•5cm. or 5•4cm. -hook, a maximam breaking load, Wmax., was obtained. (2) The most favourable points of t1 and t2 are 60 minutes and 2-4 minutes for 3cm. -hook, 160 minutes and 3-6 minutes for 4•5cm. -hook and 226 minutes and 4-8 minutes for 5•4cm. -hook, respectively. (3) Under various thermal conditions adjusted according to the law of similitude, in general, W varies as the second to fifth power of the size of the hook, d, but, for θ2, as high as 350°C and t2 above 10 minutes, we see that W is proportional to d2 approximately. (4) Taking into consideration the degree of deformation of the samples, the change of a quantitative measure of the plasticity η owing to the increase of θ2 and t2 is as shown in Table 3. (5) If we combine the results (1) and (2), we may be able to find a more excellent manu-facturing process of the hook than before.