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Volume 20, Issue 1
Displaying 1-7 of 7 articles from this issue
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T. Naka1951 Volume 20 Issue 1 Pages 2-8
Published: 1951
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESS -
T. Kobayashi1951 Volume 20 Issue 1 Pages 9-13
Published: 1951
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSFrom the result that the back reflection patterns obtained from the surfaces of shrihkage cracks in various mild steel arc welds show the mergence of Kα doublets to continuous broad lines as shown in Photo. 1, which indicates large lattice distortions, it was first asumed with the ordinary knowledge on physical metallurgy that these shrinkage cracks did riot ctake place above the A3 transformation temperature.
In order to prove the assumption, back reflection photograms from the fractures of weld metals broken by applied loads at various temperatures, viz from room temperature to 900°C, were taken. The results show that the extinguishment of Kα doublets is seen in the specimens broken at 500°C or below irrespective of the modes of breaking, as in Photo. 3 and 4. From these results, it was concluded that many of the blued cracks took place at temperatures from about 300°C to 600°C.
And the author introduced the X-ray back reflection photography as a new method for the determination of cracking temeperatures of mild steel arc welds during cooling.View full abstractDownload PDF (1635K) -
I. Onishi, Y. Kikuta1951 Volume 20 Issue 1 Pages 14-20
Published: 1951
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSA greater part of arc atmosphere is formed by covering materials of electrodes, and it gives noticeable influences upon the properties of deposited metal.
The authors studied the components of arc atmosphere and their effects upon the deposited metal by means of specially designed equipments, using a number of electrodes covered with different cellulose percentages. As the standard type electrode, illuminate type coated electrodes were used, their cellulose contents being 0, 4, 8, 13, 20 and 25 percents by weight.
The results of analysis reveal that the arc atomosphere as generated in closed vessed is composed of CO, CO2, H2, O2 and H2O. Quantitative ratio between these components markedly varies with the increase of cellulose percentage, and, in spite of excess oxygen, it approaches to the equilibrium constant of water gas reaction.
Increase of cellulose percentage also results in more siliceous as well ass glassy and porous slags, while C, Mn, Si and S in deposited metal were found to be little affected by the cellulose coating.View full abstractDownload PDF (531K) -
The nature of ice flower like structure and the effect of cooling velocityM. Okada, I. Iwasaki1951 Volume 20 Issue 1 Pages 21-25
Published: 1951
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSArc welding technique has reached a considerable stage of development and is now extensively utilized. However even at present certain defects are found in the process. In order to increase the reliability of the arc welding process, we must make an effort to eliminate these defects and reduce their effects as much as possible by thorough and careful study.
The occurrence of ice flower like structure is one of the serious defects which are apt to be found in welded parts. Particularly, it often appears in the welded part of thick plate.
Ice flower like structure may be defined as follows :
Ice flower like structure is formed by very fine columnar crystals, standing side by side, similar to ice flower in earth crevices, and it usually contains many micro-blow holes and fine particles of refractory material between the crystals. Ice flower like structure is often found in the fracture of deposited metal.
Ice fllower like structure is generally formed by almost fine columnar crystals, having micro-blow holes and refractory oxide particles between their boundaries. An example is shown in Fig. 1. When the deposited metal is rapidly cooled, the fine columnar crystals are formed side by side, and the micro-blow holes are formed by the gas evolved from the deposited metal during solidification. The dispersed oxide particles in ice flower like structure are mostly refractory deoxidation products. From these facts, it is considered that the period of formation of ice flower like structure is during the solidification process of deposited metal.
On cooling from molten state, the separation of gas and formation of stress of ice flower like structure are similar to white spot formation in ingot. But there is remarkable difference between the periods of their formation and the characteristics of their shapes.
Ice flower like structure is different from fish eye in such points as the period of formation, location and shapes.
The cooling velocity is closely connected with the volume of the deposited metals, which in turn is closely related with the formation of the ice flower like structure. When plenty of metal is deposited, the cooling velocity becomes comparatively low, accordingly ice flower like structure is not formed. On the other hand, when less metal is deposited, the cooling velocity becomes comparatively high, therefore ice flower like. structure is formed.
We examined the formation of ice flower like structure by the various experiments. As a result, we pointed out the fact that the cooling velocity is one of the factors of its formation.View full abstractDownload PDF (5571K) -
Effects of chemical composition on the formation of ice flower like structureM. Okada, Y. Wakabayashi, Y. Kondo, Y. Hayashi1951 Volume 20 Issue 1 Pages 25-31
Published: 1951
Released on J-STAGE: December 10, 2009
JOURNAL FREE ACCESSReferring to ice flower like structure, many studies and contributions have been widely announced and published. Cooling velocity, existence of, impurities, stresses, deoxidizing condition, embrittle-ment and shapes of bead are said to be the main factors of tits formation. Some of these are acceptable as the factors, but they are not sufficient to explain the formation of ice flower like itrructure.
This report refers to the effect of the chemical composition of the deposited metal and the cooling velocity.
The first experiment was to investigate the influence of chemical compositions of core wire upon the formation of ice flower like structure. Considering the experimental results, Si-rich core wire, with the same coating materials used for any content of Si, can be said to have more tendency to form ice flower like structure.
The second experiment was performed using approximately 60 kinds of coated electrodes for mild steel. The relation between the chemical compositions of the deposited metals and the forma-tion of ice flower like structure was studied. Figure 5 indicates the value of Mn, Si and C of Table 5 and other references. It was certified that the ice flower like structures are frequently formed when the deposited metal is rich in Si as compared with Mn and C.
Next, further investigations were performed using the electrodes coated with different amounts of these elements (Si-Mn-C). The relation as shown is Fig. 9 was obtained. Considering from the results, it was clarified that Si-rich coating materials give rise to ice flower like structure.
Moreover, a few results were given as supplement to the first report concerning the influence of the cooling velocity upon the formation of ice flower like structure. The proper cooling velocity to produce the columnar crystals is essential for the formation of ice flower like structure.View full abstractDownload PDF (3557K) -
[in Japanese]1951 Volume 20 Issue 1 Pages 31-39
Published: 1951
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (922K) -
1951 Volume 20 Issue 1 Pages 40
Published: 1951
Released on J-STAGE: June 12, 2009
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