熔銑のサンプリングに關する工場實驗

Abstract

This experiment was performed in the blast furnace plant of Kamaishi Works, Fuji Iron & Steel Co., in order to inspect whether the current sampling method of molten pig iron was adequate or, not, and then to decide the best method. In ordinary practice two samples were taken at each tap.They were called "A" sample and "B" sample, the former was ladled on the cast-house runner and the latter was ladled at the casting machine and the grading of pig iron for sale was defined by analytical value of the "B" sample.It was requisite to ascertain the difference of analitical value of compositions between "A" and "B" samples and the changes of molten pig compositions according to the stages of tapping, especially about Si, Mn contents.So as to attain this purpose both "A" and "B" samples were taken from each hot metal ladle at each tap, and was sent to the test-room. The results of this experiment, obtained by several statistical methods were as follows:-1) There was no significant difference in analytical values of Si, S and Mn contents between "A" and "B" samples, and so abolition of "B" sample must be considered.2) There was no significant change of compositions according to the time of tapping except Si as foundry pig and S as open hearth furnace pig.3) As for the each tap of foundry pig, Si content was observed to be low value comparatively at first, and increased gradually. During this stage Si content approached to the average value at about 3/7, and showed maximum value at about 5/7 of all stages of tapping, and then decreased again a little toward the end of tapping.4) As for each tap of open hearth furnace pig, S content was observed to be almost constant value at first, but decreased slightly in the last 1/3 stage of the tapping.5) That is to say, the "A" sampling of daily work was adequate for the most part, because it was taken at the third ladle among seven or eight ladles that were required one tap, however as the types of changes of Si contents of foundry pig varied somewhat each time, it was more trustworthy to take two samples at the second and fourth ladles and analyse the mixed sample of them. As to the open hearth furnace pig, it was safe for consumers to determine the S following the aforesaid sampling.