Simple Solutions That Work! Issue 12

13 BACK TO BASICS Continued on next page and is something to be aimed for, it can quickly hit several practical constraints. Do you have the necessary distance under the furnace spout to fill such a tall ladle? There is always the question of stability with small open top deep treatment ladles. Having a tall narrow shell, can make an empty ladle unstable, especially when you consider the typical foundry floor. We’ve often added stabilizer feet to small ladles for this reason. A 4 ft tall ladle with a top diameter of less than 24” (not including the lining) or a ladle that stands over 3 metres (10 ft) high can present challenges to access the additives pocket for cleaning and repair. DETACHABLE BASES Detachable base sections on ladles go a long way to helping with the refractory maintenance and greatly help when it comes to the additives pocket. A lot of the academic information covers the design of the additives pocket, what size and shape it needs to be to achieve optimum efficiency. This information seldom considers how the ladle manufacturer will actually fabricate such a pocket or how the foundry will be able to maintain and charge it. We have frequently discussed with foundries what works for them and then how we can make it. It often seems to be a trial and error process to achieve the optimum size. Therefore, having a detachable base section allows adjustment to the additives pocket if practical results from the foundry suggest that changes need be made, and without the need to carry out major modifications on the complete ladle. With respect to the refractory, the additives pocket is likely to get the most wear so a detachable base also enables the foundry to have spare, pre-prepared base sections, that can be quickly exchanged, without the need to wreck out the complete ladle lining. I’ve also found that, especially with small deep treatment ladles having a shaped base pocket helps reduce the volume of refractory in the base. If you simply create the pocket in the refractory, you can end up with a large amount of refractory that is doing nothing other than be a pain to remove and require a lot of pre- heating. However, other compromises may have to be made, as I’ve said height can be an issue for example if your furnace spout height is only 3’-6” from the floor and a 2:1 ratio ladle has a height of 4 ft. With regard to the open top (sandwich ) type treatment ladles, we try to make the ladle shell as close to the 2:1 ratio as is practical but we’ve often had to compromises and design ladles with smaller ratios, say 1.5:1 so that the ladle can fit under the furnace spout. At the other end of the scale a 20 ton capacity open top treatment ladle, with a 2:1 H: D ratio is going to be a very tall ladle and brings its own handling problems. Feedback from foundries show that acceptable results can still be achieved with a reduced ratio. It’s also my experience that there is more flexibility with the shell ratio when it comes to the covered treatment ladles; the tun-dish and teapot spout type. Foundries have achieved good consistent treatment results with covered treatment ladles that have a shell ratio of 1.5:1 or lower. FREEBOARD It is standard practice to design treatment ladles with an extended freeboard (the distance from the top of the metal to the rim of the ladle). This is to contain the treatment reaction which can be quite violent. The violence of the reaction is dependent on the choice of additives and the treatment reactions that I witness today do seem a lot less violent than they used to be, but we still think that it is advisable to have the extended freeboard. There are no hard and fast rule about this, but it does seem to be the case that the freeboard can be reduced over what we used to have.