Low Nitrogen Partial Pressure Research Articles

非消耗電極式アーク溶接におけるステンレス鋼溶接金属の窒素吸収について

Using an arc atmosphere controlling chamber, effects of the welding conditions and atmosphere on the nitrogen content of the stainless steel weld metal by gas tungsten arc welding were investigated in comparison with those on the iron weld metal. The results are as follows:(1) The temperatures of stainless steel and iron molten pools were measured as about 1530°C and 1630°C, respectively.(2) The nitrogen content of stainless steel weld metal decreased with increasing the welding current, as well as that of iron weld metal.(3) The nitrogen content of stainless steel weld metal hardly depended on the arc length, as well as that of iron weld metal.(4) The nitrogen content of stainless steel weld metal increased with increasing the travel speed, while that of iron weld metal hardly depended on the travel speed.(5) The nitrogen content of stainless steel weld metal increased with the nitrogen partial pressure at low nitrogen partial pressure region, and was constant at the nitrogen partial pressure region above 0.2 atm in N2-Ar gas mixture atmosphere, as well as that of iron weld metal.(6) The nitrogen absorption by stainless steel weld metal was discussed with equilibrium data.

Effects of nitriding at low nitrogen partial pressures on yield and fatigue in some stainless steels

AbstractNitriding stainless steel at nitrogen partial pressures from 0·25 to 0·95 atm and temperatures from 980 to 1160 C resulted in selective internal nitridation of the strong nitride-forming elements, Ti and Cr. Titanium nitride ahrays formed in Tibearing steels, but chromium nitride only for nitriding conditions helmr the Cr2N Solvus. A nitrided case could, therefore, consist of up to three zones, one of nitrogen in solid solution, one of precipitated TiN, and one of Cr2N or mixed rhromium-titanium nitride, depending on nitriding conditions and composition. The case was the shallmrer the greater the intervention of internal nitridation in the diffusion process. Swiace hardness, strength, and fatigue endurance were usefully increased by nitriding. The strengthening was wholly attributed to nitrogen in solid solution, the precipitates being too coarse to contribute. Thus, tensile andfatigue strengthening were directly related to case depth, which, in turn, was optimized by nitriding Ti-free steels with...

Diffusion of Nitrogen through Zr–Al Alloys in Vacuum

Sorption of nitrogen by a Zr–Al alloy has been measured at constant temperatures at 300 °C and 500 °C and for nitrogen pressures in the range 10−6 to 1 Torr. The pumping speed of the Zr–Al alloy for nitrogen decreases as the nitrogen pressure is increased and increases with temperature. For a constant nitrogen pressure the pumping speed tends to decrease with time owing to increase in surface concentration. After sorption has been completed the pumping speed can be partially or entirely restored to its initial value by maintaining the active surface at the operating temperature under a low nitrogen partial pressure, e.g., 10−6 Torr. During this recovery process nitrogen compounds at the surface migrate towards the interior of the Zr–Al alloy. The data obtained facilitate, at least qualitatively, the measurement of the diffusion of nitrogen from the surface to the bulk metal as a function of time at constant temperature. The data can also be used to predict the behavior of Zr–Al based getter pumps during and after high throughput applications.