低炭素鋼の熱間および冷間加工特性におよぼす鉛の影響

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Preliminary studies have shown that the hot-workability of a low carbon steel appears not to be deteriorated by the addition of lead if the lead particles included in the steel are finely dispersed and uniformly distributed. Concerning the cold-workability, it has been shown qualitatively that the work hardening rate in the near-surface zone of a steel rod during cold-drawing could be decreased by the addition of lead, although quantitative data on this effect have not been reported. In the present investigation, the effect of lead addition on the hot-and cold-workabilities of low carbon steels prepared from the same heat has been studied. The test for hot-workability was made with a hot torsion testing machine, while, as industrial scale tests, the hot-tubing test with a Mannesmann plug mill and the hot-extrusion test by the Ugine Sejournet process were performed. Cold-workability was estimated from the work hardening characteristics of the steel under tensile or compressive deformation and the tensile properties after strain ageing were observed. The drawing forces for cold plug drawing in the cases of leaded and non-leaded low carbon steels which were hot-finished were compared. Tensile and Charpy impact tests were made on cold-drawn and aged steel tubes and the variation in Charpy transition temperature was observed on the test pieces taken in the longitudinal and transverse directions of the tubes. The following results have been obtained : (1) The hot torsion test has shown that the twisting number to failure was decreased by the addition of lead, whereas the industrial tests by the Mannesmann and the Ugine Sejournet processes have shown that the hot-workability of low carbon steels was not deteriorated appreciably by the addition of lead. (2) The drawing force or the compressive force in the cold-working of steel could be decreased by the addition of lead. (3) The work hardening rate during tensile deformation and the hardness after strain ageing were found to be decreased by the addition of lead. These phenomena can be interpreted as caused by the lubrication effect of lead. (4) The Charpy transition temperature was raised by cold-drawing, showing a peak at a medium reduction in both the test pieces taken in the longitudinal and transverse directions of the material. In the cold-worked steels aged at room temperature or at 250℃, the reduction giving the maximum transition temperature appeared to correspond to the degree of strain at which the locking force on dislocations by interstitial atoms reached the maximum value, while this reduction shifted to a higher reduction by the lubrication effect of lead. In the steels over-aged at 650℃, the largest recrystallized grain size was observed at the reduction giving the highest transition temperature.
社団法人日本鉄鋼協会の論文
1964-12-01

低炭素鋼の熱間および冷間加工特性におよぼす鉛の影響

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