- Japan Foundry Engineering Society
- 鋳物 (ISSN:00214396)
- vol.24, no.4, pp.22-28, 1952
We have troubled ourselves about the pinholes of steel castings cast in green sand moulds, so studied the cause of the pinholes and made them clear to be in the relation to hydrogen gas.</br> We made efforts chiefly to examine the influeuces of green sand factors on the pinholes, casting the samples of molten steel in various conditions of green sand moulds. And after analysed hydrogen gas of the samples, we checked up the fractures of them whether there were pinholes or not.</br> The results obtained are as follows.</br> 1) It's proved that the pinholes of green sand mould castings are caused by hydrogen gas when it is contented over 8 cc.⁄100 gr. in the cast samples.</br> 2) When the clay % of green sand is 12% and moisture % is varried from 5% to 8%, hydrogen gas in cast samples increases with the increase of moisture, and the increased amounts are under 2 cc.⁄100 gr.</br> 3) When the moisture of green sand is 5% or 7%, and clay % is varried from 11% to 17%, hydrogen gas is most contented in the samples at about 15% of clay.</br> 4) Hydrogen gas shows some increases with the decrease of permeability from 400 to 140 A. F. A.</br> 5) The relation among moisture, clay and pinholes is cleared, and 5% moisture and 12% clay of green sand are standard % in order to get sound steel castings.</br> 6) The samples cast in green sand moulds are (3 c.c. ⁄ 100 gr hydrogen gas) more rich than samples cast in a copper mould from a ladle. Therefore the hydrogen gas in molten steel just before tapping must be kept under 4 c.c. ⁄ 100 gr, considering the increase of 1 c.c. ⁄ 100 gr during the interval from the furnace to the ladle.