Development of bainitic rail steels with potential resistance to rolling contact fatigue

Abstract

Rails are a major capital and maintenance cost for railways in North America. While manufacturers produce clean steels with high quality, most rails made today retain the basic carbon–manganese chemistry of traditional pearlitic rails. This paper describes the development of a bainitic rail steel with potential additional resistance to rolling contact fatigue damage. It is shown that rails can be produced in bainitic steel without the need for complex heat treatments after rolling, and that bainitic rails can have higher hardness and fracture toughness than pearlitic rails. Although small‐ and full‐scale tests indicate that the wear performance of bainitic steel depends considerably on test conditions, the indication is that bainitic steel rails can have significantly better rolling contact fatigue performance compared to pearlitic rails. Reasons for the superior fatigue performance are not fully understood, although a number of hypotheses exist. A conclusion is that continued research would be useful to understand quantitatively the physics and metallurgy of wheel/rail contact.

Mechanical and fracture behavior of bainitic rail steel

“…The low carbon bainitic steels have high toughness, impact resistance and rolling contact fatigue resistance. The mechanical properties of some bainitic and pearlitic steels reported in the literature [3,4,6,10,11] are shown in Table 2. To elucidate the data in Table 2 further, an assumption is made to calculate the toughness of the steels given in Table 2.…”

“…Bainitic steels usually contain 0.15-0.45% carbon, 0.3-2.0% man- ganese, 0.15-0.2% silicon, 0.5-3.0% chromium, and at least one element from molybdenum, nickel, copper, niobium, vanadium, titanium or boron. The compositions reported in various publications [2][3][4][5][6][7][8][9] are summarized in Table 1.…”

Analysis of softening zone on the surface of 20Mn2SiCrMo bainitic railway switch

“…It has been demonstrated in many previous studies that comparing with pearlite steels, steels with a proper bainite microstructure exhibit better combination of strength, toughness, superior contacting fatigue resistance as well as abrasive resistance [2][3][4][5][6][7][8][9][10]. Therefore, bainitic rails, including turnout, have attracted great attention in the last decade [11][12][13][14][15][16][17] As mentioned above, the turnout has a unique shape which requires special manufacturing process. During the turnout fabrication process, softening zone usually forms at the turnout surface, which will significantly reduce the turnout's wearresistance ability, results in a shortened service life.…”

Fracture and fatigue crack growth analysis of rail steels

“…Kristan, private communication, 2003) is given in Table 1. According to Sawley and Kristan [2003], J6 bainitic steel has a carbide-free structure with lath ferrite and interlath austenite in the as-rolled condition. Specimen geometry.…”