Wyniki wyszukiwania - BazTech

1

Hot Ductility of High-Mn Steel with Niobium and Titanium

Opiela Marek, Fojt-Dymara Gabriela

Advances in Science and Technology. Research Journal

|

2024

|

Vol. 18, no 3

200--213

EN

The work presents the results of research on the effect of deformation parameters on hot ductility of high-Mn austenitic steel with niobium and titanium. The investigations were carried out on steel with 0.05% C, 24% Mn, 3.5% Si, 1.5% Al, 0.030% Nb and 0.075% Ti. Hot static tensile test was performed using Gleeble 3800 thermomechanical simulator. Samples were deformed in a temperature range from 1050°C to 1200°C with a strain rate of 3·10-3 s-1. The reduction in area (RA), determined in the static tensile test, was the basis for determining the hot ductility of the examined steel. Reduction in area of examined steel decreases from 88% at the temperature of 1050°C to 59% at 1200°C. High hot ductility of the investigated steel is the result of the synergy of chemical composition optimization, properly conducted modification of non-metallic inclusions and formed fine-grained microstructure of dynamically recrystallized austenite. In addition to hot ductility, parameters characterizing susceptibility of studied steel to high temperature cracking were also defined, namely: ductility recovery temperature (DRT), nil ductility temperature (NDT) and nil strength temperature (NST) were determined. The values of these temperatures are 1240°C, 1250°C and 1270°C, respectively. This means that the temperature of the beginning of plastic deformation of ingots of this steel may be equal even slightly above 1200°C. In addition, the high-temperature brittleness range (HTBR) was determined, which is equal 30°C.

2

Effect of plastic deformation rate at room temperature on structure and mechanical properties of high-Mn austenitic Mn-Al-Si 25-3-3 type steel

Borek W., Lis M., Gołombek K., Sakiewicz P., Piotrowski K.

Archives of Materials Science and Engineering

|

2019

|

Vol. 96, nr 1

22--31

EN

Purpose: The aim of the paper is to determine influence of plastic deformation rate at room temperature on structure and mechanical properties of high-Mn austenitic Mn-Al-Si 25-3-3 type steel tested at room temperature. Design/methodology/approach: Mechanical properties of tested steel was determined using Zwick Z100 static testing machine for testing with the deformation speed equal 0.008 s-1, and RSO rotary hammer for testing with deformation speeds of 250, 500 and 1000s-1. The microstructure evolution samples tested in static and dynamic conditions was determined in metallographic investigations using light microscopy as well as X-ray diffraction. Findings: Based on X-ray phase analysis results, together with observation using metallographic microscope, it was concluded, that the investigated high-Mn X13MnAlSiNbTi25-3-3 steel demonstrates austenitic structure with numerous mechanical twins, what agrees with TWIP effect. It was demonstrated, that raise of plastic deformation rate produces higher tensile strength UTS and higher conventional yield point YS0.2. The UTS strength values for deformation rate 250, 500 and 1000 s-1 grew by: 35, 24 and 31%, appropriately, whereas in case of YS0.2 these were: 7, 74 and 130%, accordingly, in respect to the results for the investigated steel deformed under static conditions, where UTS and YS0.2 values are 1050 MPa and 700 MPa. Opposite tendency was observed for experimentally measured uniform and total relative elongation. Homogeneous austenitic structure was confirmed by X-ray diffractometer tests. Research limitations/implications: To fully describe influence of strain rates on structure and mechanical properties, further investigations specially with using transmission electron microscope are required. Practical implications: Knowledge about obtained microstructures and mechanical properties results of tested X13MnAlSiNbTi25-3-3 steel under static and dynamic conditions can be useful for the appropriate use of this type of engineering material in machines and equipment susceptible to static or dynamic loads. Originality/value: The influence of plastic deformation at room temperature under static and dynamic conditions of new-developed high-manganese austenitic X13MnAlSiNbTi25-3-3 steels were investigated.

3

Corrosion Resistance and Pitting Behaviour of Low-Carbon High-Mn Steels in Chloride Solution

Grajcar A., Grzegorczyk B., Kozłowska A.

Archives of Metallurgy and Materials

|

2016

|

Vol. 61, iss. 2A

825--832

EN

Corrosion resistance of the X4MnSiAlNbTi27-4-2 and X6MnSiAlNbTi26-3-3 type austenitic steels, after hot deformation as well as after cold rolling, were evaluated in 3.5% NaCl solution using potentiodynamic polarization tests. A type of nonmetallic inclusions and their pitting corrosion behaviour were investigated. Additionally, the effect of cold deformation on the corrosion resistance of high-Mn steels was studied. The SEM micrographs revealed that corrosion damage formed in both investigated steels is characterized by various shapes and an irregular distribution at the metallic matrix, independently on the steel state (thermomechanically treated or cold worked). Corrosion pits are generated both in grain interiors, grain boundaries and along the deformation bands. Moreover, corrosion damage is stronger in cold deformed steels in comparison to the thermomechanically treated specimens. EDS analysis revealed that corrosion pits preferentially nucleated on MnS and AlN inclusions or complex oxysulphides. The morphology of corrosion damage in 3.5% NaCl supports the data registered in potentiodynamic tests.

4

Physical simulation of thermomechanical processing of new generation advanced high strength steels

Grajcar A., Kuziak R, Ozgowicz W., Gołombek K.

Computer Methods in Materials Science

|

2012

|

Vol. 12, No. 3

115--129

EN

The scientific aim of the paper is the comparative analysis of the hot-working behaviour and microstructure evolution of thermomechanically processed and controlled cooled three advanced high-strength steels (AHSS) used in the automotive industry. The hot workability of three selected steel grades with a various content of Mn and C being major austenite-forming elements was compared. Evaluation of the resistance for hot deformation was carried out on a basis of continuous compression, double-hit compression, four-step compression and seven-step compression experiments simulating conditions similar to industrial processes. It was found that the hot workability of the new generation of AHSS is very challenging due to high values of flow stresses required. However, it is possible to obtain fine-grained transformation products of supercooled austenite with a high volume fraction of retained austenite for low-alloyed steels or single-phase austenitic microstructure in the high-manganese steel. Thermally activated processes of microstructure restoration which enable for successive grain refinement and affecting final flow stress values were identified. Finally, the comparison of the microstructures characterizing the first, second and third generation of AHSS was carried out. Some similarities and differences concerning the hot deformation behaviour and microstructure detailes are indicated.

PL

Celem naukowym pracy jest analiza porównawcza obróbki plastycznej na gorąco i rozwoju mikrostruktury obrobionych cieplno-plastycznie oraz chłodzonych w kontrolowanych warunkach trzech wysokowytrzymałych stali stosowanych w motoryzacji (AHSS). Przedstawiono porównanie odkształcalności na gorąco 3 wybranych gatunków stali o zróżnicowanej zawartości Mn i C, będących głównymi pierwiastkami austenitotwórczymi. Oceny oporu kształtowania plastycznego dokonano na podstawie prób ściskania ciągłego, ściskania dwuetapowego, cztero-etapowego oraz siedmioetapowego symulującego warunki zbliżone do procesów przemysłowych. Stwierdzono, że odkształcalność na gorąco nowej generacji stali AHSS wymaga zastosowania dużej wartości naprężeń uplastyczniających. Możliwe jest jednak uzyskanie drobnoziarnistych produktów przemiany austenitu przechłodzonego o dużym udziale austenitu szczątkowego w stalach niskostopowych lub jednorodnej strukturze austenitycznej w stali wysokomanganowej. Dokonano identyfikacji aktywowanych cieplnie procesów odbudowy mikrostruktury austenitu pozwalających na sukcesywne jego rozdrobnienie oraz decydujących o końcowej wartości naprężenia płynięcia. Porównano uzyskane mikrostruktury stali charakteryzujące pierwszą, drugą i trzecią generację stali AHSS. Wskazano podobieństwa i różnice dotyczące odkształcalności stali na gorąco oraz szczegółów mikrostrukturalnych.