By the low temperature annealing treatment of high grade cast irons for the release of casting stress, the degradation of the qualities of irons must be avoided. The purpose of this research is that the effects of the melting condition and the relation between manganese and sulphur to the low temperature annealing treatment are investigated. The annealing of the specimens was carried out at 500°, 550° and 600°C for 6 hrs and then the specimens were cooled in a furnace. The results obtained are summarized as follows ;
  (1) In as-cast and in annealing state, the mechanical properties of the cast irons by oxidizing refining are much lower than those of the cast irons by reducing refining.
  (2) In the plain high grade cast irons, the velocity of decomposition of carbide in annealing at 600°C for 6 hrs is higher than that in annealing at and below 550°C. Therefore, because of the softening of pearlite matrix, the tensile strength and the hardness of specimens treared by the former procedure are much lower than those of specimens treated by the latter procedure. The lower the manganese content is, the larger becomes this tendency and the amounts of 0.80 to 1.00 per cent manganese is effective to prevent this tendency.
  (3) The rate of graphitization of the specimens prepared by reducing refining is maximum, when it contains 0.06 per cent sulphur and by this rapid graphitization, and the mechanical properties of this spceimens is reduced.
  (4) The rate of graphitization of the specimens prepared by reducing refining which contain 0.06 per cent sulphur is comparatively low and, as compared with the mechanical properties of the specimens prepared by reducing refining which contain 0.03 per cent sulphur, those of the former specimens are better.

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  The relationship between wear and Ti content of the cast iron, produced through the process of Ti-slag treatment in investigated. The results are summerized as follows.
  (1) As Ti content increases, is hardness of the cast iron decreases gradually.
  (2) Flake type graphite is observed when 0.02%Ti is contained in the cast iron. And 0.12%Ti, flake mixed with eutectic type one, and when 0.23%Ti, eutectic type one with cell structure are observed.
  The increase of Ti content accelerates the decomposition of matrix pearlite to ferrite and graphite.
  When Ti content is 0.38%, the ferrite occupies nearly more than 50% of the matrix.
  (3) From the results of this study, in the range of 0.23%∼0.29%Ti, the cast iron proved to have the best wear resistant property, especially under the severe condition where the lubricated oil film is early to be broken.
  (4) The phenomenon mentioned above is again confirmed from long running wear experiment.

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  This report is on the study of the properties of the surface heating type air generator in cupola.
  This apparatus is a cylindrical container which is vertically divided to two rooms filled up with fire bricks or steel plates.
  Exhaust gas from the cupola burns in the combustion chamber and passes through the one side of these rooms to heat these filling up, and the fresh air supplied for cupola is heated by these goods while passing through the other side.
  At regular intervals, we change the supply of exhaust gas and fresh air to these rooms at alternately, then we can obtain the hot air constantly.
  Our experiment result in tailure; the temperature of the hot air did not rise over 200°C, because of the small area of the heating surface and low heating temperature of the filling up.
  But we can see the great utility of this apparatus as the heat exchanger on cupola.
  When we use this apparatus, we must take care of the following :
  1) To use the high pressure blower which has enough capacity to the drop of air pressure in the generator and cupola etc.
  2) To design the generator which has relatively large area and low height to reduce the pressure loss of the supplying air by low velocity and short pass.

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  The Authors made a series of experimental investigations for the purpose of obtaining data which would be useful to find a way preventing metal penetration into the cores of large steel castings. The size of the core tested was 25mmφ 60mm. the test casting, each of which had three cores to be tested near its bottom, was 130mm in diameter and 380mm in depth. The pressure of molten metal on the cores was exerted by a device connected with a compressed air system and wad kept sonstant for sheduled time at a scheduled pressure value; namely ; 0.2, 0.4, 0.8 or 1.0kg/cm². Results obtained are as follows:-
  1) Penetration of the depth of more than 10mm took place always in a few second after the metal pressure exceeded a certain value which was controlled by the conditions of experiment provided that the temperature of the core was higher than the solidus point of the cast metal.
  2) Core wash could not prevent penetration when the metal pressure was as high as 1kg/cm².
  3) The depth of metal penetration was plotted against the metal pressure and the core hardness, where the sand grain size distribution was concentrated to anyone of 28, 48, 100 or 200 mesh.
  4) Similar plots ware obtained for several kinds of practical core sand mixture, where the sand grain size distribution was more broad and complicated.

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