Improvements in Casting Quality Through Replacement of Feeding Systems in Gravity Casting Process

Through the research work, all of its previously set objectives were achieved. The construction of the metal sleeve for ceramic protection was appropriately designed and manufactured to mechanically and thermally prevent damage to the ceramic during production itself. In the preparation of the melt from AlSI10 Mg, the findings are that the degassing and modification process of the melt is of key importance for appropriate melt quality. With the Impeler MTS 1500 device, which enables a speed of 700 rpm, by rotating the rotor you achieve in the melt a so-called 'vortex' or a funnel is created in the middle.

Problem

Through the research work, all of its previously set objectives were achieved.

Solution and Method

The construction of the metal sleeve for ceramic protection was appropriately designed and manufactured to mechanically and thermally prevent damage to the ceramic during production itself. The positioning of the lugs for fixing the metal protection in the upper half of the tool was also appropriately manufactured. There was no loosening in the screw connection between the casting tool and the metal sleeve, as certain vibrations come from the hydraulic system when closing and opening the casting tool in connection with the thermal shrinkage of the casting tool. The venting system was also appropriately manufactured, so that during crystallisation it vented into the space all gases that were trapped in the feeder, thereby reducing the possibility of gas porosity formation in the casting.

The design for the ceramic was appropriately selected, particularly the good choice of a tight fit with the protective metal sleeve in the most exposed lower part, which is also the most thermally stressed due to the greatest mass of the feeder, and in this area there are the greatest mechanical stresses. The choice of type and kind of ceramic was appropriately selected, as it withstood casting without damage. In casting simulation, it is particularly important that you set process parameters that are as close as possible to the actual state.

However, it is also necessary to have good knowledge of all processes that are involved and have an influence on casting quality. Here I am primarily thinking of the wear of insulating foundry coatings, which have a key influence on achieving metallurgical soundness as well as the visual quality of the casting. In the actual process, these coatings wear out due to mechanical wear and lose the appropriate properties with which they ensure appropriate conditions for the melt and ultimately the soundness of the casting.

You cannot insert such deviations into the simulation. In the manufactured simulation, the final simulation data were very comparable with the actual state.

Results

In the preparation of the melt from AlSI10 Mg, the findings are that the degassing and modification process of the melt is of key importance for appropriate melt quality. With the Impeler MTS 1500 device, which enables a speed of 700 rpm, by rotating the rotor you achieve in the melt a so-called 'vortex' or a funnel is created in the middle. This mechanical phenomenon causes all impurities and hydrogen to be expelled to the surface from the entire quantity of melt that is in the transfer ladle, with the help of inert argon gas and cleaning salts. To achieve appropriate quality of material structure, the main influence is from the chemical elements strontium and titanium-boron, which must be handled carefully so as not to add too little or too much content, because they also have negative effects in both directions.

They have an influence on the size of the crystal grain and fine-grained structure. From the manufactured thermal analysis, all results were within the limits of quality requirements or prescribed standards. The chemical analysis, which was manufactured for the casting batch of the research work, was in accordance with the standard for AlSI10Mg alloy. The gassing index, samples that were taken from the holding furnace every 2 hours, were within the limits of the set target or requirements according to the standard.

The findings in tool preparation are that it is very important to constantly maintain the insulating foundry coating in the casting process. This begins to wear out over time. The main reasons for this are the solidification of the melt as it transitions from liquid to solid state, and when separating the casting from the mould. Process parameters were computer-controlled, which means that in the event of temperature deviation outside the tolerance range, the line would stop, or the cause would be the temperature of the tool or melt. During casting there were no stoppages, therefore very good conditions were achieved in the manufacture of castings and there was no side negative effect on the subsequent quality of the casting.

When examining the soundness of castings on the X-ray device, the findings were that with the ceramic feeder the desired result was achieved, and this was confirmed with a 100 per cent yield of quality good castings. With the metal feeder, an even better result was achieved than expectations or what the manufactured simulation showed. The main reason for the better result on metal feeders is that metal, in connection with additional applications of insulating foundry coating, has lower thermal conductivity than was given in the simulation.

With additional coating of insulating coating in the metal feeder, we can also cause a negative effect, as with an excessively thick layer of insulating coating we reduce the volume of the feeder and thereby cause a negative effect. For a repeatable stable process and quality good casting, the choice of ceramic feeder is the correct solution. The basic assertions proved to be correct regarding product conformity and tool construction. Process parameters are a key factor for product quality and these must be 100 per cent controlled with different levels of monitoring and automated so that in the event of deviation they stop the operation of the device, machine or tool.

In simulations, it is particularly important that the team involved in manufacturing the simulation accurately knows all processes, where there are potential possible deviations and there is no constantly repeatable process. In this way, it is enabled that the most accurate actual data are inserted into the simulation, which will be important later in the process. The key findings of his research work are that by using a ceramic feeder and selecting appropriate construction and a previously well-manufactured casting simulation, we achieve significantly better quality results in foundry work with more complex castings.

This reduces our large costs through scrap and labour costs.