High temperature phase chemistries and solidification mode prediction in nitrogen-strengthened austenitic stainless stee
- PDF / 3,578,210 Bytes
- 13 Pages / 594 x 774 pts Page_size
- 51 Downloads / 201 Views
I.
INTRODUCTION
NITRONIC 50 is a nitrogen-strengthened austenitic stainless steel, developed as a substitute for 304 and 316-type stainless steels in applications where strength and corrosion resistance were of primary importance.~ Mechanical property data on Nitronic 50 (originally designated 22-13-5 and termed XM-19 by ASTM) have been compiled by several authors, 2'3'4 and recent work by Espy 5 dealt with the weldability of Nitronic 50 and Nitronic 50W, the latter a matching weld filler metal. One measure of the weldability of a stainless steel is its tendency to hot crack, which is influenced by the amount 6 and distribution 7 of delta ferrite in the weld. These, in turn, are related to the solidification mode of the particular stainless steel, and recent papers 8-H have sought to characterize the solidification of 300-series stainless steels. In general, it has been found that welds which solidify as primary deltaferrite are more resistant to hot cracking than welds which solidify as primary austenite. 8'~2'Z-~ Few data exist on high temperature phases in Nitronic 50 and Nitronic 50W although some characterization of phases formed in the temperature range of 600 to 1150 ~ has been done.14 The solidification modes of these alloys have not been established, and predictions of solidification modes using the Fe-Cr-Ni ternary diagrams, as has been done for stainless steels of near-ternary compositions, ~5~J6 could be inaccurate because of the other alloying elements. The present investigation considers the chemistry and distribution of major and minor phases up to the solidus temperatures of both alloys, and relates these data to the solidification modes experienced during welding.
ANN M. RITTER and MICHAEL F. HENRY are Staff Metallurgists, General Electric Corporate Research and Development, Schenectady, NY 12301. WARREN F. SAVAGE is Professor and Director of Welding Research, Department of Materials Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180. Manuscript submitted December 21, 1982.
METALLURGICAL TRANSACTIONS A
II.
EXPERIMENTAL PROCEDURE
Two heats of material were used for this study, one of Nitronic 50 (N50) and one of Nitronic 50W (N50W). The composition of the N50 alloy conformed to specifications for ASTM XM-19, which require a maximum carbon level of 0.045 pct, and the composition of the N50W alloy conformed to a General Electric Company specification. The weld filler alloy, N50W, has increased Cr and Mn and decreased Ni, relative to N50. The alloys were vacuum induction melted, and poured under 1 atmosphere of nitrogen. The compositions of the heats are given in Table I. Differential thermal analysis (DTA) curves obtained on both alloys were used to measure the liquidus and solidus temperatures. The samples used for the phase study were 0.010 inch thick and contained about 84 pct cold work. They were heat treated in a box furnace under an argon atmosphere, and with the exception of a few low temperature ages, were heat treated in the cold-worked condition. The sample coupons were hea
Data Loading...
