A STUDY OF TRANSFORMATION CHARACTERISTICS OF WELD METALS AND BASE METALS
Abstract
A high-speed dilatometer is described for studying the continuous cooling transformation characteristics of steels which have been heated to various temperatures in the austenitic phase region at heating rates comparable to those encountered in a weld. Techniques were developed for protecting dilatometer specimens for decarburization at elevated temperatures. The continuous cooling transformation of Carnegie armor plate was studied dilatometrically at 1700 to 2450F. Photomicrographs illustrate the effect of maximum temperature on the transformation structures. Specimens which had been cooled at rates slower than the critical rate exhibited small-scale banding; banding had a more serious effect on hardenability as determined by the dilatometer technique than by other methods. With a progressively slower cooling rate, the nonmartensitic portions of the microstructure increased perpendicularly to the banding axis. The transformation behavior is presented in transformation isotherm diagrams which permit the calculation of the metallurgical structure for any cooling rate and maximum temperature. The beginning of transformation with continuous cooling is shifted to increasing temperatures and decreasing times in correspondence with the low hardenability and low-alloy content of the first regions to transform. The effect was particularly noticeable at the temperature denoting the initiation of martensite transformation. The most rapid grain growth occurred at 2100 to 2300F which was the region of greatest grain size contribution to total hardenability.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 25, 1953
- Accession Number
- AD0012974
Entities
People
- Edward C. Nelson
- Ernest F. Nippes
Organizations
- Rensselaer Polytechnic Institute