Refer to the Part 1, p. 403 (April, 1954 issue of Tetsu-to-Hagané)

View full abstract

By the actual use of the Stiefel-Mannesmann piercer, the authors studied the effects of piercer plug contours designed in various ways upon the piercing phenomena from the practical points of view. The variations of piercer plug contours were, with the other factors kept constant, made upon two theoretical sections, namely reducing section and reeling section respectively. The results obtained were summarized as follows:
As we changed the plug contour in reducing section from the stumpy shape (Q type) into the acute shape (O type),
(1) The dimension of tubes became larger, with a slight increase of diameter and wall-thickness, while the elongation decreasad with the increased twist of tube surfaces.
(2) While the kM/sec. remained unchanged, the kM rose sensitively.
(3) The axial moving speed of tubes increased. The authors actually discovered from the recent test that the adoption of O type instead of Q type resulted in increase of the speed equal to that obtained by expansion of the roll inclined angle by approximately three degrees.
(4) As regards the variations of strain rate in the course of piercing operation, the peak-load considerably rose and the position of the peak moved towards the outlet side owing to the unreasonable deformation in the latter half of piercing operation.
(5) Both inside and outside defects of tubes tended to be formed.
When plugs of no reeling section were used, the wall-thicknesses of tubes tended to assume undulating shapes with the aggravation of non-uniformity. As outside diameter of tubes became lessened also, the elongation rate fell. The twists of tube surfaces decreased with a slight effect on the whole. the kM/sec, kW and axial moving speed fell. The highest strain rate in the course of piercing operation somewhat decreased and the distribution phase became sharp. Sensitive effects were seen upon the formation of inside defects of tubes. Especially defects tended to be formed when round billets were of inferior quality. Almost no effect upon outside defects was observed, but the defects still tended to increase.

View full abstract

he present study was made with a view to improve the properties of the surface of rolled carbon steel. This report treats of the results of fundamental experiments made on the influences of heating conditions, sorts of steel and alloying elements on the oxidation of carbon steel (C 0.06-0.40%) at high temperature in the air and on the surface state of carbon steel. The oxidation degree at high temperature increased with lowering of heating rate. Rimmed steel was more easily oxidized than kileed steel at high temperature. Effect of Si, C and Cu on oxidation rate of steel was recognized, but that of C and Cu was lower than in the case of Si. The process of forming scale on the surface of carbon steel was as follows: the blackish cloud on metal surface occurred due to oxide film formed at about 400°C and this film grew into black thick oxide film containing 54-63% FeO, then somewhat swollen thin scale mainly of Fe₂O₃ developed on the film grew into bluish black thick scale containing 41-42% FeO and thin scale sticks to the surface of the thick scale. The Ni and Cu in steel formed an alloy-layer remaining on the surface of steel withont causing any oxidation. An empirical formula showing the relation between temperature and oxidation degree of the samples at heating rates of 20° and 6°C/min was obtained, and the formula showing the interrelation among Cu and Ni contents in steel, oxidation degree and thickness of alloy-layer was presented.

View full abstract

The authors studied the effect of carbon, silicon and manganese contents on the aging of Ni-Cr-Co austenitic heat-resisting steel containing 15% Ni, 20% Cr and 15% Co.
The authors first examined the change of their hardness due to various heat treatments of each sample: i e, a solution-treatment and aging, and then observed the microstructure.
As the results of these experiments, they gave most moderate composition and heat treatment for Ni-Cr-Co austenitic heat-resisting steel, concluding that (1) C 0.3-0.4%, Si 0.5-1.0%, Mn 1.5-2.0%. (2) The solution-treatment at 1200-1250°C, and the aging temperature at 700-750 °C, the aging time being 6-12 hours.

View full abstract

(1) The author made clear for the first time that the properties of the ball-bearing steels are influenced by raw melting materials even when they have the same chemical compositions, C, Si, Mn, P, S & Cr as specified; that is, the samples made of the armco iron as the raw materials for melting show lower hardness after annealled, more shallow-hardened depth by Jominy test after quenched, and higher ring rushing strength in comparison with the samples made of the return-scraps in plant. (2) With the presumption that these differences of the properties would be caused by small quantity of the contained impurities, N, Ni & Cu, due to the raw materials for melting and also by Sn, Pb & As, by comparing the contents of the impurities in both samples, the author added these impurities artificially to the samples made of the armco iron as the raw material for melting and tested the relation between these added quantities and the changes of the properties. (3) According to the results tested 3 times, changing N in about 0.003-0.025%, the hardness after annealled, hardened and tempered increases a little and the ring crushing strength after hardened and tempered decreases generally with increase of N. (4) By increasing each of Ni and Cu up to about 1.0%, the transformation temperature decreases distinctly with the former. but it does not clearly with the latter. However, both of them make increase of the hardness after spherodizing annealled. Concerning to the ring crushing value, a little increase can be seen in some of the former but monistic change is not recognized, and in the latter, some decreases or no monistic change are acknowledged. (5) According to the results tested with addition of each Sn, Pb & As up to about 1.0%, the transformation temperature increases a little by Sn & As, but is not infiuenced by Pb, and the hardness after spheroidizing-annealed is not influenced by Pb at all, is made a little higher by As, and is raised up most markedly by Sn. The hardness after hardened and tempered shows the inclination for a little increase in each case. The ring crushing strength decreases most remarkably by increase of Sn, and great difference in the declining extent of the crushing value is not observed between As and Pb increased until about 0.3%, but the decline of the value is seen more remarkable with As than with Pb when added more than the above. (6) The changes of microstructures by addition of the said impurities were investigated, and further electron-microscopic study or research by special etching method were carried out on some cases. (7) As mentioned above, proving with the numerical values resulted from the concrete tests that the properties of the samples made of the armco iron as the raw material for melting approach generally to those of the samples made of the return-scrap in plant when we added artificially the impurities, N, Ni and Cu, or Sn, Pb and As to the-samples from the armco iron, it made the initial step to clear the problems influenced by raw materials.

View full abstract

When 1g of steel (Al content<0.2%) is dissolved with 20cc of dilute H₂SO₄ (1+9) and 5cc of H₂O₂ (30%) metallic Al and AlN in steel dissolve comletely simultaneously with iron matrix, while Al₂O₃ remains in residue. According to Beeghly's research, AlN in steel is not dissolved at all with Ester-Halogen reagents and is found quantitatively in the residue.
The authors, on the basis of these properties, have determined metallic Al, AlN and Al₂O₃ in steel separately.
It requires about three hours in case of applying this method and the results obtained have shown good reproducibility. Then, some investigations applying this determination method, have been made on metallic Al, Al₂O₃ and AlN in Thomas steel.

View full abstract

In order to determine nitrogen in iron and steel by distillation method, the author used an apparatus that consisted of two parts, i.e., a dissolving part and a distilling part, both in exact and rapid determinations.
The author designed a new simple apparatus for rapid determination of nitrogen by distillation method for iron and steel, and also for organic nitrogen. The dissolving part and the distillating part are combined to a block made of hard glass. Samples which were expected to have a large nitrogen content in acid-insoluble residue, were not suitable for analysis, because this was so designed as the sample held in the Kjeldahl flask was dissolved and distilled continuously without being taken out of the flask in order to divide residue from solution, and therefore the nitrogen content in residue could not be read.
The results obtained by tbis apparatus showed a good agreement as compared with those determined by the standard method, as shown in Table 1.

View full abstract

Since 1949 the ultrasonic testing have been successfully applied to steel plants, ship buildingyards and railroad-maintenance shops etc. in Japan. The authors described the present stage of the testing method from the standpoint of steel makers, presenting the examples of application to detecting various kinds of defects and failures lie inside of steel products, such as ghost-line defects, flakes, shrinkage hole, large nonmetallic inclusions, fatigue cracks and internal tears etc. of steel forgings, castings and welded goods. The influences of primary structure, grain size and microstructure on the attenuation of ultrasonic energy in these materials were also described.
In order to utilize this method for material inspection, it is necessary to collect the actual example of individual test on the relation between oscilloscope pattern and true state of defects. At this juncture of the state of Japan, therefore, it is not yet ripe for setting up the standard of inspection without enough preparation of actual data, especially it must be attended not to use it carelessly for the trade of manufactures with commercial purposes. And it is more important to apply it to the incessant improvement of products as well as keeping correct records and the accumulation of the informations on it. When it is dealt with between a maker and an user, it must be taken for thoroughly from the technical point of view without a slight mingling of the preoccupied commercialism.

View full abstract