AUSTENITE – FERRITE TRANSFORMATION TEMPERATURES OF C MN AL HSLA STEEL

The article is aimed to investigate a shift of transformation temperatures of C-Mn-Al HSLA steel with different cooling rates. The transformation temperatures from austenite to ferrite have been determined by dilatometry using thermal-mechanical simulator Gleeble 1500D. To define the start and finishing temperatures of the austenite-ferrite transformation intersectional method was used. Effect of cooling rate on transformation temperature has been evaluated for 0.17, 1, 5, 10, 15, 20, 25°C.s-1. There was found out that rising the cooling rate results in moving transformation temperature range to lower temperatures. The transformation temperatures have been also compared with temperatures calculated using equations of several authors. Some of them have considered cooling rates only. Cooling rates have effect on final microstructure. The effect has been evaluated by measuring hardness (HV10) relating the cooling rates from 0.17 to 25°C.s-1. Increasing cooling rates resulted in increase of hardness. Moreover, Thermo-Calc software was used to determine the Ae3 and Ae1 equilibrium temperatures. Equilibrium transformation temperatures Ae3-Ae1 were higher than experimentally measured by dilatometric method using Gleeble 1500D.

STUDY OF THE MICROSTRUCTURE OF MARTENSITE-BAINITE STEELS AND NICKEL ALLOYS WHEN MODELING HEAT TREATMENT MODES USING A DILATOMETRIC METHOD

We present the results obtained using the equipment available at the Center for collective use “Composition, structure, properties of structural and functional alloys” NRC “Kurchatov Institute” — CRISM “Prometey”: DIL 805A/D (TA Instruments) and DIL 402C (Netzsch) dilatometers. Dilatometric analysis which provides determination of the temperature coefficient of linear expansion and the temperature of phase transitions, as well as evaluation of the transformation kinetics, can also allow simulation of heat treatment modes to identify the size of the former austenitic grain using vacuum etching and conduct the research aimed at improving the technology of thermal and thermomechanical processing (TMO) of steels and alloys. The experiments were carried out both in vacuum and in dynamic helium atmosphere. The main methodological difficulties that we have faced with are described. For steels of martensite and martensite-bainite class (38KhMA, 38KhN3MFA, 20Kh3NMFA) conditions of vacuum etching in the chamber of the dilatometer are specified. The efficiency of the method for martensite-bainite steels in determination of the grain size compared to traditional methods of etching is deminstrated. The effect of thermodeformation parameters on the size of austenitic grain is estimated. When modeling the heat treatment modes by the dilatometric method, the microstructure of KhN55MVTs nickel alloy was also analyzed. Changes in the size and morphology of the grain structure at different stages of heat treatment are revealed. The obtained results were used to adjust the current modes of heat treatment and obtain a uniform fine-grained structure. The combined application of dilatometric and metallographic analyzes after vacuum etching of the material decreases the production costs attributed to obtaining the desired microstructure upon thermal and thermomechanical processing of the products and blanks.

Density Of The Copper-Rich Cu-Pb-Fe Alloys

Density of the copper-rich corner of the ternary Cu-Pb-Fe alloys was determined with the dilatometric method. Investigated alloys had constant copper content equal to 0.9, 0.8 and 0.7 mole fraction, and varied iron concentration up to 0.1 mole fraction. A model predicting the density of ternary solution from knowledge of density of pure component and the excess of molar volume for limiting binaries is proposed.