Steel Teeming Ladle and its Refractory Lining Nov08

Steel Teeming Ladle and its Refractory Lining...

Steel Teeming Ladle and its Refractory Lining Steel teeming ladle (STL) is needed in a steel plant to contain and transport liquid steel from the steel making furnace to the casting facility. These days STL is used in a significantly more complex manner than the older steel melting shops where ladles were used simply to transport liquid steel from a steel making furnace to the ingot moulds. Other functions carried out in the STL are temperature control, deoxidation, additions of carburizer and ferro-alloys and inclusion floatation. In the recent past, the demand for various grades of steel with stringent specifications has increased considerably. These steels are produced using secondary refining processes. The lining of the STL must withstand increasingly severe service conditions associated with the secondary refining processes. These severe conditions are longer holding time, higher liquid temperature and arc/chemical heating. Rinsing with inert gas and degassing of the liquid steel, alloying and use of synthetic slag also accelerate the wear of lining. Because of these activities the demand on the quality of STL refractories has increased very much. In present day steel melting shops STL functions as traveling components of skimming, rinsing, reheating, and degassing processes. The exposure time for a given heat in these shops has expanded from two to five times of the time earlier needed for ingot teeming. STL is also required to conserve heat by minimizing heat loss during transport and during the various process steps. In this regard, significant developments have been made to properly preheat ladles prior to the first heat, and to cycle ladles on subsequent heats in a manner to minimize heat losses. STL is designed to be heat resistant and strong. Also it is necessary to heat insulate the ladle. Proper heat insulation is...

Argon Rinsing of Steels Oct26

Argon Rinsing of Steels...

Argon Rinsing of Steels Gas rinsing process is a method where rinsing of liquid steel in the teeming ladle is carried out through injection of inert gas into the steel bath. Argon (Ar) gas is preferred for rinsing since it is not only inert in nature but its solubility in steel is also very low. Rinsing results from the expansion of gas due to heating and decrease in pressure as the gas rises. The Ar rinsing of liquid steel is carried out for obtaining homogenous temperature, composition, and promotion of slag metal refining reaction.  The Ar rinsing of liquid steel is reported to be an excellent process for floatation and separation of non-metallic inclusions. The liquid steel after tapping is stratified in the teeming ladle due to the additions of the ferro alloys and the carburizer in the teeming ladle at the time of tapping of the steel. This stratified steel is agitated by purging of Ar gas in the Ar rinsing station. Ar gas purging through the liquid steel bath help generate enough bath turbulence to effect rapid thermal homogenization. Stirring with Ar also enhances mixing rate for chemical additions. Different variables for argon rinsing include gas purging rate, amount of liquid steel (heat size), amount of superheat available in the liquid steel, amount of carry over slag, amount of synthetic slag or ladle covering compound added, amount of mixing needed for chemical additions. Experienced operators and metallurgists recognize the importance of accurate and consistent Ar gas rinsing in the teeming ladle. Clean steel and good castability in the continuous casting machine (CCM) depend on a consistent and gentle rinse stir. A good Ar rinsing control system at the Ar rinsing station facilitates reproducible and accurate argon rinsing rates and durations. Ar gas can...

Combined blowing process in converter steel making Apr30

Combined blowing process in converter steel making...

  Combined blowing process in converter steel making Inhomogeneities in chemical composition and temperature are created in the melt during the oxygen blow in the top blown converters due to the lack of the mixing in the metal bath. There is a relatively dead zone directly under the jet cavity in the converter. The necessity to improve the steel making process in the top blown converter has led to the development of the combined blowing process. The first combined blowing practice to be commercially accepted was the LBE (Lance Bubbling Equilibrium) process developed by ARBE-IRSID. This process is much more closely related to the BOF process in that all the oxygen is supplied from the top lance. The combined blowing aspect is achieved by a set of porous elements installed in the bottom of the converter through which argon or nitrogen is blown. In LBE process the nitrogen gas is typically used almost exclusively for the majority of the blow in the range of 3 -11 N Cum/min. However in the later part of the blow when nitrogen absorption can create a problem, argon gas is used for stirring. In addition, argon is used almost exclusively as the inert gas for post blow stirring, at this time the rate is increased to 10-17 N Cum/min. The process is shown in Fig.1. Fig 1 Combined blowing processes The profile of a porous element is shown in Fig 2   Fig 2 Profile of a porous element for the LBE process The bottom buildup and the subsequent loss of the porous element is the major problem associated with this process. The difficulties in maintaining the LBE elements operational have led to pursue the application of the non cooled tuyeres. Here also the oxygen is delivered through...