In order to measure the volume of evolved hydrogen, the weldments are usually immersed in a bath of mercury or glycerin, as called substitution method. The total hydrogen content, however, is measured smaller by using glycerin than by using mercury under same conditions. In this study, the volume of gaseous hydrogen (H2) and the evolved hydrogen (H) from hydrogenated steel specimen were measured by the substitution method, using mercury, glycerin, 6N-K2CO3 and ION-K2CO3 as collecting solution. The accuracy of the hydrogen measurements for various collecting solutions were discussed and the results were summerized as follows; (1) In the case of using glycerin, the experimental errors appeared easily. Above errors were mainly caused by absorbtion of hydrogen bubbles on measurement wall, remain and dissolution in glycerin. (2) The 6N-K2CO3 solution did not absorbed gaseous hydrogen, but absorbed the evolved hydrogen from specimen. (3) In the case of using 10N-K2CO3 collecting solution at 35°C the results obtained were satisfactory for determination of the evolved hydrogen in same manner as using mercury. (4) Hydrogen content can be measured with a high accuracy by using mercury, but point to which special attention should be paid is the health for the operator because of mercury vapour.
Hydrogen embrittlement of steel has been investigated both by tensile test and internal friction technique. Hydrogen was charged in specimens by cathodically electric method and high temperature method. High temperature method charged hydrogen in the specimens at γ-phase (950°C) and trapped within by following water quenching. And immediately after chargings, specimens were aged at various time intervals and measured the change in notch-tensile-strength at each aging time by tensile test. Hydrogen cold-work-peak height was measured at various aging levels. N.T.S. of materials decreases with increasing aging time, goes through its minimum and recovers to the value of the hydrogen-free materials. Hydrogen cold-work-peak height increases with increasing aging time, goes through its maximum and peak vanishes by long enough aging. Parallelism was found between the drop in toughness and the hydrogen cold-work-peak height. Further, there exists a linear relatioship between the two.
Hot pressure welding joints of aluminium and copper are studied to find the application as a transition piece for use in aluminium conductors of the electric power distribution facilities. In paticular, the effect of a long term exposure at elevated temperature on the weld joint is discussed and the change of mechanical and metallurgical properties due to the exposure is experimentally investigated. In conculsion, the good welded joints with little intermetallics can be easily obtained by this welding procedure, but three kinds of intermetallics (θ, η2, γ2) are observed at the weld interface after some exposure at elevated temperature, and the reduction of the strength at the weld is found as the growth of intermetallics reaches to about 1, u in width. Equivalent diffusion coefficient of the joint of aluminium and copper is calculated from micrographic determination of the width of intermetallics and applied to determine the estimated life at a working temperature as the electric conductor.
Cold cracking susceptibility of high strength steels is investigated from the view point of lower critical stress for cold cracking (σcr) by Implant Test Method. And the correlations between σcr and Pc-estimation for cold cracking which was established by Ito et al. are investigated. Results can be summarized as follows. (1) Lower critical stress for cold cracking (σcr) imp has good correlation with PCM value of steel, diffusible, hydrogen content and cooling time from peak temperature to 100°C during welding process. (2) (σcr) imp can be estimated by following formula. (σcr) imp=-242 PCM-22.5 log H+50 log t-3 (σcr) imp (kg/mm2); lower critical stress for cold cracking PCM (%); chemical composition for cold cracking susceptibility of steel PCM=C+Si/30+Mn+Cu+Cr/20+Ni/60+Mo/15+V/10+5B H(cc/100g); the value of diffusible hydrogen (JIS method) t(sec); cooling time of weld from peak temperature to 100°C.
In this report of a basic study for the residual stress measurement of a practical welded structure through X-ray, the authors derive the φ-sin2ψ method, named tentatively, in which the direction of incident X-ray can be selected arbitrarily, and then investigate to apply the present method to such the portion of a structure as where the direction of incident X-ray is confined by the shapes and arrangements of other members of a structure. Results are summarized as follows; (1) The present method involves the multiple regression analysis of the linear statistical model, in which diffraction angles for incident X-ray on an arbitrary direction is treated as a random variable, and from the solutions of the analysis, the expectations and confidence intervals of stresses are estimated on all directions at a measured portion. (2) The present method, where the direction of incident X-ray is not confined theoretically, can also be applied on such the geometrically confined portion in direction as above-mentioned, and then makes it possible to estimate the stress on any direction at a measured point with accuracy enough for practical usage. (3) For obtaining a more accurate stress at such the confined portion by the present method, it is necessary to increase degrees of freedom through increasing a number of informations of diffraction angle of X-ray, and also, to obtain the informations over the range of the incident angle of X-ray as wide as possible. (4) The apparent diffraction angle of strain-free crystals is treated as one of the partial regression coeffi-cients and estimated through multiple regression analysis.