Model investigations on liquid velocity induced by submerged gas injection in steel bath

The technique of dissolution rate measurement is used to determine the liquid velocity induced by different locations of submerged-lance gas injection. As a result of the study the equations are proposed to calculate the liquid velocity for any location of submerged lance. It has been shown that off-centre lance location increases considerably the potential of submerged gas injection in terms of attaining the uniform liquid velocity in the bath and decreasing the total dissolution time of the additive.     

Residence time distribution of steel melt due to argon shrouded stream pouring in a tundish

The effects of shroud diameter, air rate and submergence depth on the residence time distribution of steel melt due to argon shrouded stream in a tundish are studied through a cold model by the impulse response technique using a micro-computer. All the above parameters are found to influence the proportion of surface/bottom flow and the residence times of the volumes of fluid before exiting the tundish. The effect of flow pattern on residence time is analysed in terms of the ratio peak time/delay time and the variance/square of mean residence time. Lastly, a relationship is derived between the different volume fractions and the residence time.     

Mixing-time correlation in top gas stirred melts

An experimental study is conducted to study the factors affecting the mixing-time of a top gas stirred metal bath in absence and presence of melting scrap by a chemical decolouration model method. The results obtained on mixing-time are presented and discussed. Mixing-time results are correlated successfully with the modified Froude number.     

Modelling of submerged gas injecting lance design parameters

Submerged gas injecting bottom lance design parameters are modelled by applying the theory of compressible flow of gas under irreversible-adiabatic conditions. Using the criterion of onsetting the jetting mode of injection of gas into liquid the lance design paramters such as upstream stagnation pressure and Mach number, length of the lance for a given diameter and material, gas injection rate etc. are determined. Nomograms are presented to determine the above mentioned lance design parameters. The derived parameters are discussed in relation to submerged gas injection practice.     

Study of fluid flow in tundishes due to different types of inlet streams

Flow pattern and residence time distribution induced by different methods of pouring of molten steel into a tundish are studied by means of a water model with and without flow modifiers (FM). It was found that the submerged stream without FMs produces short circuiting and argon shrouded stream leads to excessive surface directed flow of liquid in a tundish. Open stream pouring generates surface turbulence and does not produce short circuiting. The effect of FM is found to be different for different methods of pouring, e.g. dam eliminates short circuiting and produces surface directed flow for submerged stream, whereas weir limits the surface turbulence within the inlet region for open stream pouring. Dam is found to reduce the dead volume for argon shrouded pouring.     

Dynamic variations of lance distance in impinging jet steelmaking practice

The behaviour of a free gas jet is used to study the dynamic variations of lance distance to supply oxygen in impinging jet steelmaking practice. It is shown that the dimensionless momentum flow rate within the jet describes satisfactorily the plant data on variation of lance distance to supply oxygen. Correlations are proposed to determine the lance distance to supply oxygen and its variation during the blow.     

Studies on the behaviour of mist jet and its cooling capacity of hot steel surface

The present study is concerned with the design of mist nozzle to produce air/water mist jet, and to investigate the behaviour of mist jet and its capacity to cool the hot steel surface. The behaviour of the mist jet is studied by collecting water at different axial distances. Radial water flux profile is correlated with a Gaussian type of distribution function under a wide range of experimental conditions. Maximum water flux in the mist jet is correlated with the downstream axial distance and water-loading ratio. Water-loading ratio is found to influence water flux more strongly than axial distance. Radius of the mist jet is correlated with the downstream distance. It is found that the mist jet cools a crack-sensitive steel without Cracking and, at the same time, produces a martensite type of structure.     

Model studies of slag carry-over during drainage of metallurgical vessels

Mechanism of slag carry-over during drainage of metallurgical vessel is studied in a physical model. Vortex and drain sink formation are found to be the main mechanism of carry-over of slag to the underlying vessel. Empirical equations are obtained to determine vortex and drain sink height under a wide range of draining conditions. Macroscopic mass and energy balance are used to determine vortex time. The vortex time is discussed in relation to the synchronization of the ladle change-over time during sequence casting.     

Friction and wear properties of steel backed Al-10Sn-4Si-1Cu metallic strips prepared via spray atomization-deposition-rolling route

In various load bearing structural applications related to automotive industries, steel backed aluminum alloy strips are considered. For such applications, it is desired to design appropriate alloy composition for metallic strip so that good tribological properties can be achieved. In our ongoing efforts to accomplish this aim, we have recently fabricated a steel backed Al-10Sn-4Si-1Cu bearing strip, which is prepared by spray depositing the molten bearing alloy on a steel substrate, followed by warm rolling of the resulting laminated strip to different thickness reductions up to 80%. The tribological performance of the steel backed Al-10Sn-4Si-1Cu strips is evaluated against the bearing steel. While the recorded steady state coefficient of friction (COF) does not show any noticeable difference (varying in the range of 0.6-0.7) with respect to difference in warm rolling conditions, the fretting wear rate (10-26 × 10^− 5 mm³ N^− 1m^− 1) of the steel backed and warm rolled strips exhibits a systematic decrease in wear rate with increase in amount of warm rolling. SEM-EDS analyses reveal the oxidative wear and the extensive cracking of alumina rich tribolayer as the dominant material removal mechanisms. The tribological properties of the spray deposited and 80% rolled steel backed Al-10Sn-4Si-1Cu bearing strip is compared with those of a commercially available Al-Sn based sleeve bearing under identical fretting conditions.     

Experimental study of the effect of gas injection parameters on the bath mixing intensity induced during steelmaking

The present study is concerned with the evaluation of the bath-mixing intensity induced by gas injection during steelmaking. The rate constant for the process of mass transfer between the two cold-model simulated immiscible liquids (water/oil) is employed as the criterion of judgement of bath-mixing intensity. Gas is either injected from the bottom alone or simultaneously from top and bottom. Bath-mixing criterion is successfully correlated with the mixing power. Increase in bottom injection rate is found to increase the rate constant. In the simultaneous injection lance distance, and top and bottom gas-injection rates are shown to be the relevent independent dynamic parameters. From the comparison of the rate constants between pure bottom and simultaneous injection and pure top and simultaneous injection, it is asserted that the simultaneous injection provides more operational flexibility, better control of slag formation and refining rates as per blow requirements and steel grades. However, some minimum gas is required to realize the operational benefits.