Effect of Tempering Temperature on Microstructure and Mechanical Properties of Bainitic Railway Wheel Steel with Thermal Damage Resistance by Alloy Design

Abstract

Thermal damage is one of the principle modes of wagon railway wheels. A new bainitic railway wheel steel with high thermal damage resistance and good combination of strength, plasticity, and toughness was developed. Microstructure and mechanical properties of the new steels in a tempered condition at different temperatures were examined. Microstructures were observed using scanning electron microscope and transmission electron microscope. Mechanical properties were evaluated by tensile, hardness, and Charpy impact tests with a simultaneous comparison to pearlitic railway wheel steel. The characteristic of retain austenite and V(C,N) were measured through X-ray diffractometry and energy disperse spectroscopy. The results indicate that this new bainitic wheel steel presents a submicron-sized carbide-free bainite morphology and preferable integrated mechanical properties when tempered at 280–360 °C. Precipitation strengthening plays an important role for the high strength, since a two-time-strengthening mechanism of the yield strength led by precipitation has been found at 280–360 and 480–560 °C, respectively. Compared with a pearlitic railway wheel steel, bainitic wheel steel tempered at 320 °C has a 10% higher yield strength, five times higher impact toughness, and much better thermal damage resistance, which is a promising railway wheel material for higher speed or heavier axle-load service conditions.

Algorithms to Estimate the Ductile to Brittle Transition Temperature, Upper Shelf Energy, and Their Uncertainties for Steel Using Charpy V-Notch Shear Area and Absorbed Energy Data

“…In the early 1900s, various impact tests were developed, originally to test the quality of armor plate and boiler steels, and the ASTM E23 method for Charpy impact testing procedure was tentatively released in 1933 [1]. The use of Charpy testing has expanded greatly, and examples of industries that rely on Charpy testing today include shipbuilding [7][8][9], nuclear power [10,11], armor [12], rail [13,14], construction [15], steam turbine [16], piping and pressure vessel [17][18][19], liquified natural gas storage [20], hydrogen storage [21], additive manufacturing [22], aluminum alloy development [23], and composites [24]. The principles and methods described in this paper are relevant to many critical structural applications but will be analyzed and discussed with respect to steel line pipes widely used in natural gas and hazardous liquid pipelines.…”