MARTENSITIC HIGH CHROMIUM HEAT RESISTANT STEELS
Abstract
Experiments were conducted to determine the effect of longer treatment at high temperature on the hardening characteristics of high-Cr steels. Solution treatments of 2, 4, and 8 hr were employed at each of the 3 austenitizing temperatures for 15 steels representing Cr levels of 18, 21, and 24%; Ni levels of minimum, 2, and 3%; N contents of minimum % and .01 x % Cr; and C ranging from 0.23 to 0.56%. Response of hardness levels to length os solution treatment was negligible. Six-hr tempering treatments were superior to 1 hr. Studies were made of structures produced by variations in Ni and N additions to a 0.35%C, 21.0% Cr base alloy. Marked changes in primary ferrite were observed for 4 combinations of 0.12% and 2.17% Ni with 0.06% and 0.23% N; the low-Ni, low-N alloy was more than 75% -structure at 1900 deg F. The high-Ni, high N alloy was austentic at all solution temperatures. Within certain ranges, Ni and N appeared to be nearly equivalent to C in its stability to change phase relationships. Excess carbides were present in nearly all instances. Tensile tests were made on 3 alloys of the 21% Cr group; the low N grades displayed inadequate yield strenght at 2 hardness levels, and unsatisfactory ductility at the higher level. A 2% Ni, low-N alloy resisted softening by tempering treatments at 1100 and 1200 deg F, and showed high yield strength but little ductility.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 29, 1953
- Accession Number
- AD0017303
Entities
People
- John A. Fellows