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Metal Casting Technologies : March 2010
30 www.metals.rala.com.au TECHNICAL FEATURE and fluidity. Lime (CaO) is added to for sulphur removal. Alumina is added to the slag to increase the electrical resistivity. The mixture of Calcium Fluoride (70%) and Alumina (30%) is the commonly used slag in the ESR process4. The ESR process has now become an accepted method of producing high quality ingots in a variety of steels and alloys. A variety of steels and alloys are processed by ESR process. These include ball bearing steels, high speed steels, low alloy high strength steels, super alloys, etc. In the current experiment, an electrode will be prepared from the waste chips. ESR of chips electrode will be carried out. Alloying addition will be done in the ESR process itself. The ingot will be characterized. Experimental work Electrode preparation Mild steel chips formed during machining were collected. The chips were washed in kerosene properly and dried. A hollow mild steel tube was taken and its open end was hammered to make it closed. The dried chips were rammed inside a hollow mild steel tube of 40 mm diameter. Ramming was done manually by a steel rod of 25 mm diameter. Holes were drilled on the tube surface to allow any gases to pass. The electrode holder is a 40 mm diameter mild steel rod. At the top of this a steel plate is welded. A copper flat plate is fitted on this plate. The copper plate has a tapered hole for an electrical contact. The cathode end of the ESR unit has a solid copper tapered end. This fits properly on the electrode holder copper plate. The mild steel hollow tube is welded to the lower end of the electrode holder. A hollow 6 mm inner diameter tube is filled with alloying elements and slag powder. The tube cross section is changed at 20 mm distance by mechanically hammering. This will prevent fall of the alloying elements at one time during the start of the process. This tube is welded along the length of the 40 mm hollow tube. A 3 mm diameter commercial purity aluminium wire is tied on the 40 mm hollow tube for deoxidation purpose. Figure 2 shows the prepared electrode. The average sulphur percentage (chips 0.03, hollow tubes 0.04, 0.03) was 0.033. Preparation of flux Acid grade Calcium fluoride (CaF2) and Alumina (Al2O3) in 70:30 weight ratio were mixed thoroughly. The liquidus temperature of the flux of this composition is about 12500C5. The mixture THE ESR PROCESS HAS NOW BECOME AN ACCEPTED METHOD OF PRODUCING HIGH QUALITY INGOTS IN A VARIETY OF STEELS AND ALLOYS Fig. 3 Fig. 2
Media Kit 2010