Abstract
Two grades of stainless steels, wrought round bars of type 347 alloy and Croloy 16-8-2 Cr-Ni-Mo alloy, were subjected the RPI hot ductility test by the authors' experimental apparatus and the following results were reached:
(1) The investigation showed that the hot ductility curves of both grades obtained by the experimental apparatus agreed satisfactory with those reported by Nippes RPI.
(2) Both grades studeid showed that the prior thermal history markedly affected the hot ductility. In general, short exposures to a temperature 1340°C caused a significant reduction in the hot ductility measured at temperatures during the cooling portion of the thermal cycle. The hot ductility of type 347 during the cooling portion was for inferior to that of 16-8-2 Cr-Ni-Mo alloy at testing temperatures between 1200°C and 1300°C.
(3) Microscopic observation indicated that this phenomenon was closely related with embrittlement due to grain boundary liquation, and the degree of embrittlement of type 347 was for greater than of 16-8-2 Cr-Ni-Mo alloy.
(4) Microscopic observation also showed that the fractures of both grades tested were of intergranular type when heated above 900°C.
(5) The values of hot ductility of type 347 during the coling portion of the thermal cycle showed considerable scatter, while that of 16-8-2 Cr-Ni-Mo only appreciable.
