The effect of heat treatment on the properties and structure of molybdenum and vanadium dual-phase steels
- PDF / 4,150,496 Bytes
- 11 Pages / 594 x 774 pts Page_size
- 69 Downloads / 193 Views
A
significant amount of research has been conducted on the relationship between the properties and microstructure of dual-phase alloys (e.g., Refs. 1 and 2). The processing, properties and deformation characteristics of hot-rolled, intercritically-annealed molybdenum and vanadium alloys have recently been studied.3,4 However, a systematic study of the effect of annealing temperature, time and cooling rate on the fine structure and mechanical properties of those dual-phase steels has not been made. Tanaka et al 5 studied the effect of alloying elements and cooling rate on the formation of the dual-phase structure in chromium steels, and microstructure maps were used to show the effect of cooling rate on microstructure in dual-phase steels? Transmission electron microscopy of the fine structure of dualphase steels has been conducted by many investigators. s-t~The structure was characterized as consisting of regions of high dislocation density close to the ferritemartensite interfaces and regions of low dislocation density in grain interiors? Indeed, various investigators have attributed the low yield strength and the continuous yielding chracteristics of dual-phase steels to the mobile dislocations generated by the volume expansion accompanying the transformation of austenite to martensite during cooling from the annealing temperature. 8 Rigsbee and VanderArend 8 reported a minimum in the yield strength of a Cb-V dual-phase steel at 4 to 5 pct martensite. A minimum cooling rate at which the yield strength and the yield-to-tensile ratio diminished and at which the yield point elongation went to zero was found in chromium dual-phase steels) This minimum cooling rate was also found for a vanadium dual-phase steel and was attributed to the formation of A. R. MARDER is Senior Scientist, Research Department, Bethlehem Steel Corp., Bethlehem PA 18017. Manuscript submitted November 25, 1980.
pearlite) The study described in the present paper correlated the mechanical properties of vanadium and molybdenum dual-phase steels with the microstructure determined by light and transmission electron microscopy. EXPERIMENTAL PROCEDURE Hot band, 2.54 mm (0.10 in.) thick, of the vanadium and molybdenum compositions listed in Table I were pickled and cold-rolled to 1.27 mm (0.05) in.) or 0.76 mm (0.03 in.) in the laboratory. Data from a base Mn-Si dual-phase alloy, 1.01 mm thick (0.04 in.), was used for comparison. H After cold rolling, tensile blanks were cut and heat treated for 1 and 3 min at the following temperatures: 760 ~ (1400 ~ 788 ~ (1450 ~ 816 ~ (1500 ~ and 843 ~ (1550 ~ A chromelalumel thermocouple was flash-welded to the center of the grip region of each specimen to record the complete thermal profile during heat treatment. Specimens were cooled from each temperature at the following rates: 2~ (3.6 ~ 5~ (9 ~ 10 ~ (18 ~ and water quenched. The water quench rate was approximately 600 ~ (1080 ~ The cooling rate was determined between the annealing temperature and 260 ~ (500 ~ Standard tensile testing and metallography were co
Data Loading...
