Prakt. Met. Sonderband 38 (2006) 305 
MICROSTRUCTURE AND MECHANICAL CHARACTERIZATION 
OF QUENCHED AND TEMPERED GS 35 CrMoV 10 4 CAST 
ALLOYS FOR ELECTRIC POWER GENERATORS 
J. F. Alvarez-Antolin*, J. Asensio-Lozano*, J. T. Panta-Mesones** 
* Department of Materials Science and Metallurgical Engineering, The School of Mines, 
Oviedo University, c) Independencia, 13, 33004 Oviedo, Spain. 
LI ** Faculty of Mines, Metallurgy and Materials, National University of Trujillo, Avenida Juan 
Pablo Il, Trujillo, La Libertad, Peru. 
$20 ABSTRACT 
> Temp. This paper presents a study of the microstructural and mechanical characterization of the 
GS 35 CrMoV 10 4 alloy employed in the manufacture of sand-cast “poleshoes” for 4-pole 
synchronous electric power generators working at a frequency of 60 Hz. In addition, the 
most appropriate treatment for ensuring compliance with the technical specifications 
defined in DIN Standard No. 1.7755 has been designed. 
1. INTRODUCTION 
The aim of the study was twofold: i) to determine by means of forensic analysis the 
reasons that justify why three poleshoes denoted as “5”, “9”, and “10”, manufactured in GS 
35CrMoV 10 4 steel [1] (measuring 1640 mm x 275 mm x 127.5 mm), normalized at 
900°C for 3 hours, quenched in oil, and subsequently tempered at 650 °C, present 
abnormally low values of hardness as determined by the Charpy Test at 20 °C; and ii) to 
design the most appropriate treatment for ensuring compliance with the technical 
specifications, Tables | and Il. To do so, a study of the microstructural evolution from the 
as-cast state of 2 poleshoes, denoted as “A” and “B”, was carried out, after successive 
thermal treatments. 
2. EXPERIMENTAL PROCEDURE 
Chemical analysis of poleshoes “5”, “9”, “10”, “A” and “B” was determined by means of 
emission spectroscopy (Quantovac). The results obtained are the mean of 3 
determinations and are expressed in % weight, Table |. 
Charpy tests were carried out on V-notched samples with a resistant section of 80 mm? 
extracted from poleshoes “5”, “9”, and “10” at room temperature, Table V. 
Metallographic observation, followed by a micrographic study, was carried out on 
cylindrical samples obtained from poleshoes “5”, “9”, and “10”, Figure 7.Poleshoes “A” and 
“B", in the as-cast state, were subjected to a thermal treatment consisting of a double 
normalizing, both at 900 °C for 3 hours, followed by water quenching from 900 °C and