Metallographische Untersuchungen zur Ermittlung des Temperaturbereiches beginnender Aufschmelzungen von austenitischen mit Titan oder Niob stabilisierten Chrom‐Nickel‐Stählen

Abstract

Untersuchungen über den Gefügeaufbau austenitischer, größtenteils mit Niob/Tantal oder Titan stabilisierter Chrom‐Nickel‐Stähle mit 0,03 bis 0,09 % C, 17,2 bis 18,6 % Cr und 10,0 bis 11,0 % Ni bei Temperaturen oberhalb 1300 °C. Ermittlung des Temperaturbereiches beginnender Aufschmelzungen. Auswirkung eines Zusatzes von Niob/Tantal oder Titan. Verhalten der Sonderkarbonitride und Auftreten von Eisenniobid Fe2Nb.

Welding Metallurgy of Stainless Steels

“…Like chromium and molybdenum, niobium promotes the formation offerrite to the detriment of austenite. On the other hand, the causes for hot cracking phenomena in the heat affected zone during the welding of fully austenitic niobium containing chromium-nickel steel castings with low phosphorus and sulphur content are related by Dahl,DUren and MUsch [57] to niobium concentrations at the grain boundaries in the coarse cast structure which lead to the formation of low melting niobium and nickel phases which solidifY in part below 1160 0 C. Tamura and Watanabe [58] as well as SchUller [59] report that the formation of hot cracks in the heat affected zone of niobium containing austenitic steels can probably be attributed to a low melting eutectic of niobium carbide or niobium carbonitride with y phase. There is, however, a major difference to the effect of molybdenum and chromium.…”

“…The possible formation of low melting phases due to the presence of titanium have been investigated by Schuller [59] in 18/10 chromium-nickel steels. The first melting takes place at approx.…”

“…Therefore with (P + S) = 0.03%, the weld metal should show 4 FN, with (P + S) = 0.04% 8 FN and with (P + S) = 0.05% 12 FN, in order to achieve the highest hot cracking resistance. Niobium concentrations at the grain boundaries may lead to the formation of low melting niobium and nickel rich phases which even partly solidify below 1160 0 C. Tamura and Watanabe [58] and Schuller [59] report that the formation of hot cracks in the heat affected zone of niobium containing austenitic steels are probably caused by a low melting eutectic of niobium carbide or niobium carbonitride with austenite. 99 (page 155).…”

“…Whereas in the ferrite containing niobium alloyed weld metal with 5 FN niobium containing liquid phases amount to only to 0.3%, this content increases in fully austenitic weld metal with 0 FN to considerably higher values of around 1.5%. For practical applications, the possible scattering effect must be considered, as previously discussed at the end of section 5.3.2. The possibility of the formation of low melting grain boundary phases by the element titanium has been investigated by SchUller [59]. The low melting grain boundary phases represent niobium rich eutectics which promote hot cracking.…”

“…Laves phase, definition of 27,28,136,137, Liquation cracks 144,147 Liquid-solid interface [58][59][60][61][62] Low carbon martensitic steels 179 -mechanical properties of weld metal 182 -metallurgy of welding of 179 -practical welding of 181 -precipitation phenomena 185 Manganese 29 -influence on Fe-Cr-Ni system 29 -influence on hot cracking resistance 30,40,155,156,163,167,168,219,220 -influence on intergranular corrosion attack 114 -influence on nitrogen solubility 30 Martensite transformation of stainless steels 14,97 Martensite transformation of ferritic chromium steels 97-100 Mechanical properties of austenitic-ferritic dissimilar joints 238,239 -of austenitic-ferritic duplex weld metal 194,195 -of ferritic weld metal 176,177 -of fully austenitic weld metal [219][220][221] -of low carbon martensitic weld metal [182][183][184] -of stabilized austenitic weld metal [211][212][213] -of unstabilized austenitic. weld metal 204-206 Metallurgy of welding of austenitic-ferritic dissimilar joints 229 -of austenitic-ferritic duplex steels 186 -of austenitic steels 197 -offerritic steels 172 -of fully austenitic steels 214 -...…”