Improvement of Austenitic Hadfield Mn-Steel Properties By Thermomechanical Processing

Abstract

A thermomechanical processing technique is used to improve austenitic Hadfield Mn-steel wear properties. ASTM A128 grade C steel billets were sized and multi-pass hot rolled. Rolling has been successfully carried out up to an 80% reduction in thickness on four passes in the temperature range 1200 to 800 °C. The inter-pass time ranged between 9 to 13 seconds. The steel was then solution treated at 900, 1000 and 1100°C for 30 min. at temperature. Austenite grain size was measured and the carbide volume fraction was evaluated. The austenitic grains of the as-cast structure are surrounded by a network of carbides. The carbides have a lamellar structure and are richer in Cr and Mn than the austenitic grains. Austenitizing at 1100 °C was the optimum to dissolve the network of carbides. However, solution treatment at the higher temperature coarsens the austenite grains while decreasing the carbide volume fraction. By contrast, hot rolling creates finer grains and signficantly reduces the carbide content. Furthermore, hot rolling followed by solution treatment further decreases the carbide content and distributes them homogeneously. This process has a positive effect on both the mechanical and wear properties. High reductions by hot rolling of the Hadfield steel creates both deformation bands and a twinned structure. These twinning boundaries are considered as slip obstacles to provide strengthening. A thick sheet martensitic structure is created accompanying twinning. Moreover, solution treatment of the hot deformed steel leads to the formation of a thin martensitic structure.Résumé -On utilise une technique de traitement thermomécanique pour améliorer les propriétés d'usure de l'acier austénitique au manganèse. On a coupé et laminé à chaud par passes multiples des billettes d'acier ASTM A 128, de grade C. On a effectué le laminage, avec succès, jusqu'à une réduction de 80% de l'épaisseur, avec quatre passes dans la gamme de température de 1200 à 800 °C. La durée entre les passes était de 9 à 13 secondes. On a ensuite effectué un traitement de mise en solution à 900, 1000 et 1100°C, pendant 30 minutes à la température donnée. On a mesuré la taille de grain de l'austénite et l'on a évalué la fraction volumique du carbure. Les grains d'austénite de la structure brute de coulée sont entourés d'un réseau de carbures. Les carbures ont une structure lamellaire et sont plus riches en Cr et en Mn que les grains d'austénite. La température optimale d'austénitisation pour la dissolution du réseau de carbures était de 1100 °C. Cependant, le traitement de mise en solution à cette température plus élevée produit un grossissement des grains d'austénite tout en diminuant la fraction volumique de carbure. En contraste, le laminage à chaud crée des grains plus fins et réduit significativement le contenu en carbure. En outre, le laminage à chaud suivi par le traitement de mise en solution diminue encore plus le contenu de carbures et distribue ceux-ci de façon homogène. Ce traitement a un effet positif tant sur les propriétés mécaniques ...

Effect of progressive solid-solution treatment on microstructures, mechanical properties and impact abrasive wear behavior of alloyed high manganese steel

“…The austenite grains are refined. One report [25] pointed out that carbides are basically shows that holding at 950 °C for a period of time can ensure the dissolution of M 7 C 3 carbides. To prevent the coarsening of crystal grains, the temperature of the highest holding stage is set at 1100 °C [23], and the progressive solidsolution treatment route is shown in figure 1(c).…”

Microstructural Analysis and Tribology Behavior of a Medium-Mn Steel with Mo

“…Hardness in these steels is quite important because it allows qualitative estimation of the austenite decomposition in other constituents. The austenite of these steels is by far the softest constituent, and therefore any significant increase in hardness above 220-250 HB in the absence of cold working can be interpreted as due to the decomposition of austenite [1].…”

“…Manganese austenitic steels, also known as Hadfield steels, are among the ferrous alloys most used under severe wear conditions in the presence of impacts at low temperatures. There are numerous works evaluating the properties of these types of steel [1][2][3][4], the transformation phenomenon of retained austenite in martensite [5][6][7], and the influence of the service deformation processes on the properties and microstructure [8][9][10]. However, these steels suffer accelerated wear when the working temperature is above 100 • C due to carbide precipitation and subsequent loss of hardness.…”

High strain rate mechanical properties of austenitic manganese steel

“…Numerous theoretical and experimental studies have been performed to describe the process of shear localisation and to determine the factors governing the process. [12][13][14][15] Although various studies on low strain rate deformation resistance, work hardening mechanisms, strain aging, thermomechanical processing, formability characterisation, microstructural evolution and the superplasticity of high manganese steel have been carried out, [16][17][18][19][20][21] very little information is available regarding the mechanical properties and fracture behaviour of this material under high strain rate compression loading conditions. Accordingly, the purpose of the present study is to investigate the mechanical properties and fracture evolution of austenitic manganese steel in compression as a function of strain rate using the split Hopkinson bar.…”