Synopsis:In the previous paper,the authors ascertained that when the steel samples containing Al or Mn were analysed by the vacuum fusion method,the O values decreased quantitatively with the increase of such elements.In this paper,the following are dealt with:(1)Relations between the above-mentioned phenomenon, the temperatures of the inner wall of the apparatus, of the Mo-hood covering the graphite crucible, and then the components (Fe,Al,or Mn) of the condensed film on the inner wall surface. (2)The analysis of the residues in the crucible revealed the increasing tendency of Mn and Al vaporization proportional to each content.On these experimental results, it is concluded that when the samples containing Al or Mn are molten, the vapour pressures of these elements are remarkably high comparing with other metals and so the vapourized quantities become larger.Consequently, a film containing Fe, Al or Mn is formed on the inner wall of the apparatus and adsorbs the extracted CO gas.Thus the 0 values determined are lowered.
Synopsis:The purpose of boron treatment is to improve the hardenability of steel by addition of small emounts of boron less than 0.005%, and to save the alloying elements, nickel, chromium, and molybdenum. In Japan, there have been some basic investigations about the boron steel, but little experience in producing it.In order to promote the use of boron steel successfully, the authors believed, it was necessary to study the influence of boron addition on the steels specified in Japanese Industrial Standards.Effect of boron addition on the grain size, critical temperature, hardenability and mechanical properties of ease-hardening and constructional steels in JIS specification were studied by the use of small ingots. The results obtained were as follows;(1) It was found that the full deoxidation and nitrogen fixing by proper addition of Al and was necessary to increase the hardenability and to avoid the grain-coarsening tendency.(2) Effect of boron on the case-hardenability decreased as the carbon content increased. Maximum hardenability was obtained at about 0.9% C, and it was necessary to control the carburizing condition to avoid higher carbon content.(8) In the carburizing tests, the boron-treated steels behaved in the same manner as in the non-boron steels. It is presumed that boron itself had no significant effect on the carbon content and distribution of the case.
SynopsisThe aUlhors made some eX/Jerimenls wilh resjICcl 10 Ilze nitrogen and carbon monoxide exlractions by Ilze vacuum Jusion method Jar Ihe analysis of gases in steels. As Jor the nilrogen gas, the varialion oj results in the rim oj analysis and the in.fluence q! alloying elemCllts were irwesligated to com/Jare willz tlze results obtained by clzemical analysis. On tlze other hand. the lowering tendency q! ox)'gen values in the pure iron by lite addition oj Al or Mn , relal;ng wilh the e./Ject oj M o-Izood, was studied. T emjJeralure measuremenls at Ihe inner wall surface oj Ihe Jurnace tube and the analyses oj the condCllsed lIletaLLic film on tlze surface and oj Ihe residual melals in the graphite crucible were also /Jerfonned. (1 ) Ascertained Ihat some elements like C r, V , M o and A I, Mn are hamiflll Jor the extraction oj nitrogen and carbon monoxide, res/Jectively. (2) Studied the cause and mechanism of the insllJficient nilrogen exlraction where its values are lower tlzan tlzose in tlze chemical analysis.(3) D iscussed the carbon monoxide adsolption mechanism oj tlze filill oj Ih e inner 1wLL mainly com/Josed oj Fe, Mn and AI. TIzCll it was Jound that tlze Mo-hood was considerably e./Jective in /Jreventil1g such a /Jhel1omenon.
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