Hiroshi Sawamura

A Stduy on the Heat Treatment of Cr-Mo Steel (Second Report)

Rectangular specimens and chain link plate specimens were taken from a cold rolled Cr-Mo steel plate. Various factors that affect the elongation of these specimens were investigated. These factors are as follows:1) Quenching temperature, 2) Holding time at quenching temperature, 3) Tempering temperature, 4) Coloring temperature and time.The elongation of specimen was measured by means of a jig boring machine having the precision of 10-3mm. The obtained results are summarized as follows:(1) Quenched rectangular specimen without annealing pretreatment scarcely shows any bending.(2) Quenching temperature and the holding time have the greatest effect on the change of elongation of the rectangular specimen.(3) The effect of tempering and coloring treatment on the elongation of the rectangular specimen is quite similar to that in the case of the annealed specimen, which was shown in the previous report.(4) The average value of the contraction of the rectangular specimen given by the whole tratment is 2.8×10-3mm/cm.(5) Quenching temperature has the greatest effect on the change of the elongation of the chain like plate specimen.(6) Tempering temperature is more sensitive to the elongation in this case than in the case of the rectangular specimen, and, therefore, the variation of tempering temperature must be kept as small as possible.(7) The change of the condition of coloring treatment does not show any significant effect on the elongation of the specimen.(8) Chain link plate specimen is deformed irregularly by the whole treatment.(9) The average value of the contraction of chain like plate specimen given by the whole treatment is 2×10-3mm/cm in the direction of the longest axis.

INVESTIGATION ON ACID-RESISTANT HIGH-SILICON IRON (III): Effects of Cooling Rate and Annealing on Mechanical Properties and Corrosion Resistance@@@機械的性質および耐蝕性におよぼす冷却速度と焼鈍の影響

Synopsis: The effects of the cooling rate and annealing on the mechanical properties and corrosion resistance of castings of acid-resistant high-silicon iron were studied. The variations in cooling rate bring about great changes in graphite structure and influence mechanical properties but hardly the corrosion resistance. It seems that the annealing of castings is important only with respect to the relief of internal casting stress.

On the Schnadt Impact Test of Higth Strengh Low Alloy Steels by

Four kinds of Si-Mn high strength low alloy steels were hot rolled into plates of 12 and 22 m/m in thickness. Schnadt impact test was carried out in the range of temperature from -80 to 97°C to investigate the effect of the degree of reduction in plate thickness, gas cutting, shearing, welding, and chemical composition on the transition temperatures and impact properties of these plates.The results obtained are as follows;1) Schnadt impact properties of the specimens taken from the thin plates are generally superior to those of the specimens taken from the thick plates.2) Gas cutting seems to reduce the notch sensibility of the plates which is rather advantageous, while the sheared surface has the trend to be notch sensible. Weld metal used is excellent in toughness.3) Suitable contents of aluminum and nitrogen in the form of aluminum-nitride seem to have a good effect on the impact properties of steel plates. Attention should be paid, therfore, in the deoxidation of molten steel to leave a small content of metallic aluminum in the steel.4) The temperature of complete brittleness (i.e. Bifractance defined by Schandt) of the specimens is lower than -15°C when the Venant number is assumed to be 20, while that of full plasticity (Octafractance) lies in a relatively high temperature range. This tendency is more conspicuous in the thick plates.5) Transition temperature is lowered as the number of Venant is increased. Transition temperature of the thin plates is lower than that of the thick plates.6) These results show that the test plates belong to high or moderate class of high strength low alloy steels when compared with the various foreign types of steels of the same kind.

INVESTIGATION ON CAST IRON HAVING REFINED GRAPHITE PRODUCED BY MELTING CAST IRON COVERING WITH SLAG CONTAINING TiO 2 (IX): Investigation on the Net Structure and the Estimation of Micro-Hardness of S-H Cast Iron@@@S-H鋳鉄の網目組織ならびに微小硬度測定

portion) was consisted of eutectic graphite structure. Both the micro-hardnesses of boundary-line and meshy portions were estimated. The results proved that the hardness of boundary-line portion was about 1.5~2.7 times of meshy portion. The authors presumed that one of the major reasons of the greater wear-resistance of S-H cast iron was based upon the following characteristics: 1. The existence of a unique net structure of S-H cast iron. 2. The presence of a boundary-line portion of greater hardness in the matrix of eutectic