Al-killed Steel Research Articles

微量Nb, V処理鋼の機械的性質と破壊の様相について

A study was made on the strengthening phenomena and fracture behaviours in alminium or Ca-Si killed low carbon manganese steels with small amounts of Nb, V or Nb-V addittion. It was found that the addition of Nb, V, or in combination of these elements produced an additional strengthening due to the fine carbonitride precipitation above the strength level presumed from the refined grain size, and this was controlled by the various heat treatments. The yield strength increment in the Nb-V, -and Nb-V-steels can be divided into the two terms, i. e. grain refinement and friction stress increment, the contribution of these two depends on the kinds of the steels and heat treatment. In Al-killed steels the impact transition temperature was generally lower than that of corresponding Ca-Si killed steels. The impact transition characteristics seem to be classified into four groups by the yield strength against the strengthening mechanism, and a linear dependence of the transition temperature on the friction stress increment has been found. A good combination of strength and toughness was obtained in the steels strengthened by the balanced effect of both the grain refinement and the friction stress factor. Finally, the fracture appearance of impact specimens was examined by microfractography.

アルミニウムキルド鋼薄板の二段焼鈍の研究

Recrystallizaticn textures of Al-killed steel sheets cold-rolled to 60, 70 and 80% reductions in thickness and finally heat-treated by various combinations of 1st-stage and 2nd-stage annealings were examined by X-ray diffraction method and optical microscopy.The time of the 1st-stage annealing was kept to 40 min, and the pole densities of (222), (110) and (200) parallel to the sheet plane after the 2nd-stage annealing were measured as functions of the 1 st-stage annealing temperature. The maximum densities of (222) after the 2nd-stage annealing.at 650°C for 1 hr could be obtained in the 70% rolled sheet by the 1 st-stage annealing at about 480°C and 575°C. These two maxima were termed as 1st-peak and 2nd-peak respectively. The 1st-peak temperature (480°C) was independent on the cold-rolling reduction in the range between 60 and 80%, but shifted to a higher temperature when a higher 2nd-stage annealing temperature was adopted.The maximum elongation ratio of the recrystallized grains after final annealing could be related to the maximum density of (222), whereas the maximum size of the recrystallized grains was found to correspond to the minimum in the (222) pole density.These results were discussed by relating the recrystallization process with the process of clustering of Al and N which inhibits the nucleation of recrystallized grains with some ranges of orientation.

Control of Sulfide Shape in Low Carbon Al-Killed Steel

Control of Sulfide Shape in Low Carbon Al-Killed Steel

On Brittle Fracture Initiation (Second Report)

In the first report, one of the authors succeeded in the brittle fracture initiation at low stress levels from the notch without any additional factors such as the welding residual stress, the impact stress and the metallurgical embrittlement etc. by using the deep notch test.In this paper, firstly, a review of the fundamental theories of fracture initiation and the theoretical extension of the results of deep notch test to the brittle fracture initiation characteristics for an infinite plate were made.Secondly, the following fundamental experiments on brittle fracture initiation were conducted : (1) Classification of zones for fracture initiation. (2) Applicability of the Griffith-Orowan energy condition. (3) Size of yield zone around the tip of notch. (4) Effect of plate thickness.Next, the brittle fracture initiation characteristics for various steels such as the mild steel, various high strength steels including HT 60, HT 70, HT 80, HT100, and various low temperature steels including 2.5% Ni, 3.5% Ni, 9% Ni steels and Al-killed steels quenched and tempered with the yield strength of 33, 37, 58 kg/mm2 were evaluated.Lastly, the correlations between the brittle fracture initiation temperature for a crack length of 10 mm under a stress level of σy/2.56 and the transition temperatures in various large and small size brittle fracture tests were investigated.

Continuous Casting Steel Slabs

A description of the plate-type mold developed by Bohler Bros, for wide slabs. Also given are details of experiments on the continuous casting of heats of rimming low-carbon steels, Al-killed steels, and austenitic Cr-Ni steels and their hot and cold rolling into strip and sheet.

On the Behavior of C and N in Al-Killed Steels during Isothermal Treatment

On the Behavior of C and N in Al-Killed Steels during Isothermal Treatment

Alキルド極軟鋼の恒温処理におけるN, Cの挙動

Alキルド極軟鋼の恒温処理におけるN, Cの挙動

軟鋼の拘束熔接時に発生する母材割れに関する二三の実験

The under-bead-crack is often seen on the high carbon and the alloy steels. But on the mild steel, if the constraint is severe for welding, mother-metal-crack is caused not only immediately under bead but at heat affected and not affected zones. In this research, using semi-killed, Si-killed and Al-killed steels, the crack sensitivity test in which a specimen is extended in the direction of the thickness of plate by the shrinkage of weld metal and the constraint was performed. And the mother-metal-crack of the mild steel was examined from the points of view of the hardenability and the cleanliness of material and the condition of constraint.

Alキルド鋼の結晶粒成長の阻止粒子について（第3報）細粒性と異常成長の機構について

In the previous reports, the authors studied the various characteristics of the behaviour of grain growth of Al-killed steel within γ-range by using high temperature oxidation colouring method and an emission type electron-microscope. In this report a further investigation was made about the resultant characteristics and the following results have been obtained: (1) The inhibitor of grain growth of fine-grained Al-killed steel is the very small particles of aluminum nitride, and the growth of Al-killed steel is very much affected by the size and distribution of the inhibitor particles. (2) To maintain fine grain, it is necessary for the specimen to contain 10∼25×10−4% of aluminum nitride in the terms of N2 quantity at the maintenance temperature, and if this nitrogen is reduced to 1∼5×10−4% by dissolving into the matrix, the steel changes into a uniform coarse grain structre. (3) The above-mentioned necessary quantity of N2 changes more or less according to the variation of soaking temperature and is only slightly affected by the size and distribution of nitride particles. (4) Grain coarsening occurs in the process while the inhibitor particles are dissolved and consumed into the matrix, and arises from the local inequality of the particle size and distribution.

オーステナイト粒の新現出法とAlキルド鋼の結晶粒成長の阻止粒子について（第1報）オーステナイト粒子の成長挙動とAl窒化物のγ鉄への溶け込み

There are ever so many representation methods of austenite grains, but they have, in general, some limitation when applied to practical use in some or other cases of chemical compositions of steel. Moreover, there was no trustworthy and versatile method of invesitgating the behavior of grains at high temperature where their actions are very remarkable. The method described here is, however, versatile enough to be used in this field of science. When the specimen is kept in inert atmosphere of high temperature, corrosion by evaporation will be noticed most conspicuously at the grain boundaries, and owing to the evaporation and rearrangement of grain surface atoms, surfaces characteristic of and inherent to crystal will be exposed. Each surface has a fixed resistance to the oxidation according to its orientation, respectively, so that when oxydized by a small quantity of oxygen the surfaces take various colors of their own. By using this method we have the advantage of observing austenite grains treated at an arbitrary temperature and duration. The present authors studied the behavior of the growth of low carbon steel grains by means of this method and noticed the pronounced correlation between the coarsening of fine grains of Al-killed steel and the solubility of AlN into γ-iron.