EFFECT OF SOLUTION TREATMENT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AUSTENITIC MANGANESE STEEL

• Main Author: Dwi Anggoro, Adimas
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/79527
• Institution: Institut Teknologi Bandung

The austenitic manganese steel has high strain hardening properties and the ability to harden under static, dynamic, and impact loading so it is widely used as a turnout crossing component in the railway industry. However, austenitic manganese steel in the as-cast condition is very hard and brittle due to the presence of carbides, hence it is should be heat treated to get optimum mechanical properties so that the pre-harden process can be done and the required mechanical properties as the turnout crossing can be obtained. In this study, the austenitic manganese steel samples were made by casting process with the chemical composition according to the ASTM A 128 Grade C. To determine the heat treatment effects on the microstructures and mechanical properties of the austenitic manganese steel, solution treatments were carried out at various austenitization temperatures and holding times, and with double solution treatment. Results showed that microstructures of the austenitic manganese steel consist of a stable austenite phase and the solution treatment process caused carbide compounds to dissolve in the austenite matrix. Solid solution strengthening and less carbide in the austenite matrix after solution treatment led to an increase in the yield strength, fracture strength, tensile elongation, and impact strength, but caused a decrease in the hardness. The best mechanical properties were found in the HT3 sample with a combination of the yield strength, 433 MPa; tensile strength, 671,4 MPa; tensile elongation, 22,7%. However, because the chemical composition of the austenitic manganese steel that has been made contains only 10,61% Mn and was below the minimum standard requirements, the obtained mechanical properties were still lower than the minimum target: yield strength, 445 MPa; tensile strength, 885 MPa; tensile elongation, 38%. During tensile plastic deformation on the solution-treated samples, the suspected twin deformation mechanism occurred so that increased the austenite microhardness due to strain hardening. The amounts of strain hardening were not uniform between the austenite grains and they were influenced by the grain orientation and the direction of tensile loading.