冷間加工後の特殊鋼線に及ぼす低温燒鈍の影響に就て

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As is well known, tensile properties, especially the elastic limit of the cold-drawn steel wires increases remarkably, when subjected to the low-temperature heating after cold-drawing. There is, however, no definit study on the mechanism of the above mentioned problem, including further that on the change of properties of cold-drawn wires at room temperatures, for instance the strain-aging. There have been found a number of experiments which contradicted each other even in their results and in their formations of conclusion. The authors here investigated the effect of low-temperature annealing on mechanical properties of the cold-drawn Cr-V steel wire, the material for exhaust-value springs of aircraft engines, with special reference to the amount of reduction in cold-drawing and further more intended to know about the mechanism of coldworking relating to the low-temperature annealing. In the present report the experimental results containing some remarkable points are informed. The preparation of samples was as follows. Wires fully annealed at 700℃ for 1 hour were cold drawn through the "Dialloy" or "Tungalloy" dies applying a special solid lubricant at a considerably slow speed of drawing. The total amount of cold-reduction was given in Table 1. Samples of about 20cm length were taken from the cold-finished wires, all of them having the diameter of 2.6mm and subjected to the succesisve heating at different temperatures for varying hours in the electric tube furnace of ordinary atmospheric conlition. The material tested contained about 0.5% C, 0.5% Mn, 1% Cr and 0.2% V as the main elements. Therefore it may be suggested, that in the full annealing the quenching effect has accompanied as the result of air-cooling of annealed wire. In our cases, however, as is clearly illustrated in Fig 11., no such suggestion could hold true. Consequently, in explanation of the increase of hardness and strength due to the low-temperature annealing after cold-drawing of the steel wire no precipitation phenomenon could be introduced. The mechanical testing of the wire was performed first by investigating the recovery of elasticity accurately. And so the tension tester was equipped with a Martens' mirror extensometer and from the stress-strain curves gained the elastic limit and yield point were determined at the residual strain of 0.03% and 0.2% respectively. Besides, the "Vickers" hardness numbers were measured for all series of samples ; and Young's modulus of elasticity and torsional value for some series. The experimental results obtained and their explanation are presented in §3 with 6 Tables and 10 Figures, from which some remarkable points may be abstracted as follows. (1) As is shown in Fig 1, the general effect of cold-drawing is the increase of hardness and st rength and the decrease of pasticity, while, the elastic limit, unexpectedly, deviates more from the yield point and breaking strength as the amount of cold-reduction increases. (2) As for the samples with 19.6% and 47.8% cold-reduction, by annealing at 300℃ the hardness and strength come to maxima, while, the breaking strength, yield point and the elastic limit nearly coincide together and the elongation drops to minimum. (3) For the higher amount of cold-reduction, for in tance 75.0% or more, various properties were affected in different ways. Their maxima were shifted towards the higher temperature side when annealed for 1 hour, but the annealing for longer durations brought the maxima towards the lower temperature side. (4) Data on the relation between the amount of cold-reduction and the degree of increment of elastic limit, also the annealing temperature at which its maximum point occurred, as is given in Fig 8a., were of most significance so far as concerns our considerations. (5) The aging effect at room temperature and the effect of annealing time at elevated temperature were almost the same as expected. The changes of elastic modulus and torsional value due to the low-temperature annealing were somewhat useful for knowing the recovery of cold-worked materials before the beginning of recrystallization.
社団法人日本鉄鋼協会の論文
1940-04-25

冷間加工後の特殊鋼線に及ぼす低温燒鈍の影響に就て

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