The influence of solution annealing heat treatment on the microstructure and hardness of Hadfield steel containing up to 3.16% chromium and 0.15% nitrogen was investigated.
Furthermore, the effects of chromium additions on the hardness and microstructure of austenitic manganese steels in the as-cast and heat-treated conditions have been studied. The true stress-true strain response of nitrogen alloyed austenitic manganese steel with chromium additions in the as-cast and heat treated conditions under compression loading was also studied. The microstructural observations on the as-cast and heat-treated steels with chromium additions revealed the stability of austenite phase in the as-cast state deformation with precipitation of carbides and carbonitrides on the grain boundaries. These precipitates increase by increasing true strain and chromium content.
2² factorial design was used to investigate the contribution effect of chromium additions and true strain on hardness of austentic manganese steel as cast and after heat treatment. The contribution of both chromium additions up to 3.16%, true strain rate up to 0.4, and the interaction combination effect of them were determined of cast and heat treated austenitic manganese steel. The regression models were built up to identify the hardness as function in chromium additions and true strain rate of both cast and heat treated austenitic manganese steel.

The effect of direct reduced iron (DRI) addition in metallic charge on the different steel making parameters and consumption figures have been studied. Data obtained from industrial heats carried out in 185-ton electric arc furnace (EAF) were used to study. The present study carried out in a wide range of DRI percentage, 0 - 50% of metallic charge, and the results have been statistically analyzed to correlate the percentage of DRI with the different consumption figures of electric energy, oxygen, coke and fluxing materials. In addition, the influence of DRI percentage on contents of tramp and detrimental elements affecting on steel quality has been also investigated.
The results reveal improving the steel quality by increasing DRI percentage, as the tramp elements (Cu, Sn, Ni, Cr) and detrimental elements (P, S) and also nitrogen, all decrease by increasing the percentage of DRI in the metallic charge. On the other hand, the increase in DRI percentage leads to increase in the consumptions (per ton of liquid steel) of electric energy, oxygen, coke and fluxing materials. Furthermore, the metallic yield decreases and the power on time and hence the tap-to-tap time increase as DRI percentage increases. With using higher DRI percentage in the charge, the yield strength and ultimate tensile strength of produced hot rolled bars of low carbon steel slightly decrease whereas elongation increases.

Factorial design was used to investigate the contribution effect of cooling rate of stage between rolling and coiling and cooling rate after coiling on grain size, pearlite lamellar spacing, mechanical properties and hardness of hot rolled narrow 65Mn strip. The contribution of both cooling rates before and after coiling process, and the interaction combination effect of both rates were determined for each measured property. The regression models were built up to identify grain size, pearlite lamellar spacing, mechanical properties and hardness as a function in cooling rates before and after coiling process.
It was found that the contribution effect of cooling rate before coiling on grain size growth, enlargement of pearlite lamellar spacing, Ultimate Tensile Strength (UTS) and elongation is negative with different magnitude and it has positive effect on Yield Strength (YS) and hardness. Cooling rate after coiling has negative effect on grain size growth, enlargement of pealite lamellar spacing and elongation while it has positive contribution on UTS, YS, and hardness. The interaction combination effect of both two rates has very small positive contribution on YS and elongation, it has small positive effect on grain size growth, enlargement pearlite lamellar spacing, and it has large negative contribution on UTS and hardness. Factorial design technique is a successful technique to analysis the effecting parameters.

This work aims at studying the change in constituent phases of High Manganese High Aluminum content steel through isothermal ageing and their effect on the plastic behavior of the produced steels. Optical and scanning electron microscope were employed for observing the significant change in microstructure at different heat treatment regime. XRD was applied to detect the major phases after isothermal process. Three samples with different phase consitituents were subjected to compression test. The results refer to the decomposition of γ-austenite into β-phase (B2, DO3), β-Mn, K-carbide is widely changed as a result of isothermal ageing process. The plastic behavior and strain-hardening property are improved linearly with k-carbide fraction. A bit enhancement of hardness has been observed with increasing k-carbide fraction after isothermal ageing process.

In virtual design of hot stamping, the reliable description of the material flow behaviour is an important input to ensure accurate estimations of the final shapes of parts. Currently, to characterise the hot stamping material’s flow behaviour at elevated temperatures, tensile and upsetting tests are available. The focus of this article is on the determination of the flow curves of manganese-boron steel at elevated temperatures based on upsetting tests. The measurement of material flow properties directly out of the upsetting tests still remains a complex task due to its non-uniaxial nature. Therefore, traditional methods to calculate flow curves out of such measurements are not necessarily appropriate. It requires a method which considers multi-axial stress states as well as non-uniform strain evolution. In that way the calculation of the flow curves is appropriate and it can provide reliable input for simulations of hot stamping. In order to interpret measurements and deduce flow properties more precisely, simulations using Finite Element Method (FEM) of the tests themselves are executed. Indeed in FE-models it is possible to account for complex boundary conditions such as non-uniform temperature fields, non-uniaxial stress states and friction between upsetting die and the specimen during the deformation. With use of inverse optimisation, based on the final geometry of the deformed specimen, Coulomb’s friction coefficient is estimated. It is demonstrated that an almost constant value of the friction coefficient is achieved, even after using many different types of strain hardening to describe the material behaviour in the FE-models. Finally, it is demonstrated that the deduced material flow curves with use of inverse optimisation are more accurate than that of the directly calculated out of experimental results.

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