Features of Austenite Formation in Low-Carbon Steel during High Speed Heating Induced by High-Speed Deformation
- PDF / 868,456 Bytes
- 5 Pages / 594 x 792 pts Page_size
- 27 Downloads / 179 Views
620.186.1:621.7.004.2
FEATURES OF AUSTENITE FORMATION IN LOW-CARBON STEEL DURING HIGH SPEED HEATING INDUCED BY HIGH-SPEED DEFORMATION V. I. Zeldovich,1 N. Yu. Frolova,1 A. E. Kheifets,1 I. V. Khomskaya,1 V. M. Schastlivtsev,1 and E. V. Shorokhov2 Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 20 – 24, May, 2020.
An experiment is performed for explosive convergence (collapse) of a cylindrical shell of low carbon steel with a ferrite-perlite structure. It is revealed that during ultra-rapid heating caused by high-speed deformation austenite formation occurs in an unusual sequence: first, free ferrite is converted, then pearlite. The decrease in free ferrite transformation temperature is explained by action of high pressure, as well as by varying degrees of heating steel structural constituents. An effect of barothermal quenching is observed, as a result of which a pearlite-martensite structure forms.
Key words: low carbon steel, austenite formation, high-speed deformation, ultra-rapid heating, barothermal quenching, pearlite-martensite structure.
using explosive energy. The aim of the present work is use of impact wave energy in order to accomplish ultra-rapid heating, caused by high-speed deformation, and analysis of the transformations that occur under these conditions.
INTRODUCTION Formation of austenite within steel with a ferrite-pearlite structure is diffusion transformation since from ferrite with about 0.02 wt.% C and cementite with 6.7 wt.% C austenite forms, whose carbon content depends on the amount of carbon in the steel. Transformation proceeds as disordered without an orientation for phases. Austenite generation under normal conditions commences in areas with an increased carbon concentration: at pearlite/ferrite boundaries and ferrite grain boundaries [1]. During laser heating of hypoeutectoid steel at a rate of 103 – 104 K/sec austenite forms first within areas of pearlite sections, and in armco iron cementite inclusions are enveloped located at the boundaries of ferrite grains [2], i.e., the process has signs of diffusion transformation. However, in another work [3] with laser heating a case was observed of diffusionless martensite-like formation of austenite in ferrite platelets of eutectoid steel pearlite. It has been concluded [4] that in order to implement a shear diffusionless mechanism for austenite formation within pearlite fast heating rates are required, which are not always achieved with laser treatment. These rates may be obtained 1 2
METHODS OF STUDY Experiments for convergence (collapse) of metal cylindrical shells under action of an explosion open up a unique possibility to accomplish high-speed plastic deformation with a small degree of reduction. Since deformation proceeds in a quasi-diabatic fashion, mechanical deformation energy is converted into heat, and the metal experiences significant heating at an ultra-high rate. These extreme conditions of deformation heat treatment may lead to preparation of new structural conditions, not available with st
Data Loading...
