THE FUNDAMENTAL FACTORS INFLUENCING THE BEHAVIOR OF WELDED STRUCTURES: THE EFFECT OF SUBCRITICAL HEAT TREATMENT ON THE TRANSITION TEMPERATURE OF A LOW CARBON SHIP PLATE STEEL
An investigation was made to determine the impact transition temperature and hardness changes attendant to the quench-aging of Project Steel "C" a semi-killed ship plate steel. Aging temperatures extended over the range from 35 deg to 1100 deg F after water quenching from 1300 deg F. Both impact and hardness tests revealed that this steel can be severely embrittled by the quench-aging mechanism. With aging temperatures up to 350 deg F, characteristic aging curves were obtained, i.e., the peak embrittlement and the time to attain this peak decreased with increasing aging temperature. For room temperature aging this peak amounted to a 90 deg F increase in transition temperature and 25 points increase in Rockwell B hardness above that of a series air cooled from 1300 deg F (unembrittled condition). Specimens aged above 350 deg F "overaged" so rapidly tht no peak in the aging curve could be detected. Metallographic examination of quench-aged specimens at 2000X showed that a two-stage precipitation reaction was operative. At low aging temperatures the precipitate was detected as a mottling of the ferrite grains; at higher aging temperatures, where an "overaged" condition was rapidly reached, the precipitate had grown so as to be resolvable. It is believed that the quench-aging phenomenon is responsible for the brittle zone previously found in the subcritically heated region in weldments of this and similar ship plate steels. This study suggests that a low temperature postheat at 650 deg F (the solution temperature below which quench-aging effects are absent) would lead to rapid overaging in the brittle zone of ship plate weldments and thus largely eliminate the embrittlement.
Case Western Reserve UniversityDepartment of Civil Engineering
10900 Euclid Avenue
Cleveland, OH USA 44106
Ship Structure CommitteeNational Academy of Science, 2101 Constitution Avenue, NW
Washington, DC USA 20418
- Evans, E B
- Garibotti, D J
- Publication Date: 1953-10-30
- Features: References;
- Pagination: 25 p.
- TRT Terms: Brittleness; Defects; Heat affected zone (Metals); Metal heating; Plate bearing test; Transition point; Welds
- Identifier Terms: Ship Structure Committee
- Uncontrolled Terms: Heat treatment; Weld defects
- Old TRIS Terms: Weld crack prevention
- Subject Areas: Marine Transportation; Materials;
- Accession Number: 00331005
- Record Type: Publication
- Source Agency: Ship Structure Committee
- Report/Paper Numbers: SSC- 61 Prog Rpt.
- Contract Numbers: NObs-45470
- Files: TRIS
- Created Date: May 21 1981 12:00AM