Study of the Effect of Multiple Tempering on the Impact Toughness of Forged S690 Structural Steel

Abstract

During the production of forged metal components, the sequence of heat treatments that are carried out, as well as hot working, remarkably influences mechanical properties of the product, in particular impact toughness. It is possible to tailor impact toughness by varying tempering temperature and soaking time after hardening treatment, widening the application range of structural steels. In this work, we consider the effects of a second tempering treatment on the microstructural properties and impact toughness of a structural steel EN 10025-6 S690 (DIN StE690, W. n: 1.8931). The steel was first forged and quenched in water after austenitization at 890 °C for 4 h. After quenching different tempering treatments were performed, at 590 °C in single or multiple steps. The effect of these treatments was evaluated both in microstructural terms, by means of optical microscopy, scanning and transmission electron microscopy and X-ray diffraction, and in terms of impact toughness. The mechanical behavior was correlated with the microstructure and a remarkable increase in impact toughness was found after the second tempering treatment due to carbide shape change.

Effect of Intercritical Annealing and Austempering on the Microstructure and Mechanical Properties of a High Silicon Manganese Steel

“…The preparation of the thin foils was realized by mechanical grinding until thickness of 70 µm, followed by mechanical punching to obtain 3 mm diameter specimens. The final polishing and etching were performed electrochemically using a twin-jet polisher STRUERS TENUPOL-3 (Struers S.A.S., Milan, Italy), with 95% acetic acid (CH 3 COOH) and 5% perchloric acid (HClO 4 ) solution, at 45 V and room temperature [26,27].…”

The Impact of Interphase Precipitation on the Mechanical Behavior of Fire-Resistant Steels at an Elevated Temperature

“…The fire-resistance of steel is generally measured at 600 °C after being held at 600 °C for 3 h [ 21 , 22 , 23 , 24 , 25 , 26 ]. Generally, the ratio of yield strength at 600 °C to that at room temperature is used to evaluate the steel’s fire-resistance.…”

“…It is widely recognized that precipitation strengthening is an important approach to improve the strength of steel at elevated temperatures. The supersaturated precipitates in ferrite can effectively improve the fire-resistance of steel by precipitation during reheating [ 22 , 23 , 24 , 25 , 26 ]. However, it is difficult to simultaneously improve the strength of steel at room temperature and at elevated temperatures.…”

Hot-Rolling and a Subsequent Direct-Quenching Process Enable Superior High-Cycle Fatigue Resistance in Ultra-High Strength Low Alloy Steels

“…Recently, several studies have been actively pursued to control the mechanical properties by optimizing the DQ process conditions [ 9 , 10 , 18 ]. In some studies, attempts were made to control the mechanical properties of conventional steels through microstructure evolutions, such as carbide formation and retained austenite stabilization by utilizing heat treatment [ 20 ]. In other words, the DQ process is thought to be a novel process through which mechanical properties can be controlled only by changing the process conditions without any additional heat treatment.…”

“…Tensile properties and fracture toughness of direct-quenched steels have already been reported in the past [ 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Considering their superior properties of tensile and fracture toughness, DQ steels can be used in automobile and vessel parts, armored vehicle shells, and construction materials.…”