DE2457678A1 - Horizontal runner channels for filling foundry moulds - with increasing runner section to compensate for frictional losses - Google Patents

Abstract

Casting systems have horizontal distribution channels or runners, which possess >=1 slightly conical sections which increase in the direction of travel of the melt and, after each runner-branch, there is a stepped redn. in the cross section of the main runner which then increases continuously (i.e. up to the next runner-branch). The coninicity of each section of the main runner between the runner-branches is pref. proportional to the frictional losses in the energy of the melt flowing along the runner, the geometric configuration of the runner profile compensating for the frictional losses. Improved filling of foundry moulds and therefore better quality castings are obtd.

Description

Casting systems with horizontal distribution runs.

Casting systems with horizontal distribution runs, their design and dimensioning a pre-selectable and constant distribution of the outflow quantity Guaranteed on the individual gates have long been very worthwhile if even their absence has hardly been noticed, even in specialist circles. Because at The current state of the gating technique referred to here can be the uniform or division of the outflow according to the desired proportions from several simultaneously acting gates on an elongated pouring runner not yet as reached, not even as through calculations or experiments animals can be viewed within easy reach. This state of the art is at two Examples briefly presented.

Fig.1 shows a normal horizontal run with a constant cross-section and several equally large and identically shaped gates on one longitudinal edge the casting lead.

It is now from very old and also from the most recent experiments ten known that the equality of the gates is by no means the equality of the real ones Partial outflow ensures. Rather, it has been found again and again that these amounts are very different and that they are moreover in the course of filling the forms commute back and forth quite considerably. The so-called "pulling" of the individual cuts is therefore both spatially unequal and temporally irregular. The irregularities become larger, the more space and metal-saving the barrel cross-section in the Ratio to the sum of the gate cross-sections is dimensioned. This depends on the then resulting increase in flow resistance in the course.

Fig. 2 shows a similarly long-known proposal for a uniform or to achieve a defined distribution of the current.

Here is the cross-section of the distribution run after each cut reduced by a fraction, which corresponds to the number of gates, if these are dimensioned to be equal to each other. The cuts should be arched be derived from the run. With such an arrangement, the "pendulum" prevented, but the larger flow resistances - compared to Fig. 1 - in the narrower sections of the run still cause a considerable disproportionality the distribution of quantities. The frictional resistance in each section is known the greater the the smaller their Que cut or hydraulic diameter and the greater their length. Furthermore, it changes proportionally with the square the flow rate, which, however, cannot be specified a priori. True is the extent of the unevenness that occurs in the individual case here fairly easy to determine by recalculation. Much more difficult, however and for the practitioner in the company the way to remedy them is not viable via a pre-calculation of those cross-sectional reductions from paragraph to paragraph - and the corresponding of the cuts, which are then of different sizes - that are required so that each gate brings the same or the subset intended for it. Such calculations can only be carried out through lengthy trial and error. Possible systems of analytical equations are even more difficult to resolve and can can hardly be used without a computer. From one from the inventor to the study of another Construction elements of the cutting technique, the so-called "climbing run", more recently = thing The knowledge gained a new conception for the mastery of the problem of long runs with several gates. This is first shown schematically in fig.

As usual at the beginning, the course has a constant cross-section, zd but also only up to the first gate as in Fig.2. After this gate its cross-section is also reduced by a proportion which corresponds to the outflow proportion which should flow out of this first section. But then the cross-section remains the section of the run that begins here is no longer constant, as in Fig is widened in a straight conical width up to the second gate. here a next reduction is made at the cross-section of the barrel that has become larger again made. Their size is measured again according to the fraction which they the outflow amount intended for the second gate from the remaining amount still arriving that is, for example, with a total of four cuts of the same target amount, one third; because a third of three quarters is a quarter of the whole. Now will turn the continuation of the barrel widens conically up to the third gate.

Here - to stay with the example - there is a reduction in cross-section by half (1/2 of 1/2 = 1/4). And that leaves for the last leg a quarter of the total left. This last laustüek is also analogous and way conically widens and then becomes the gate itself by means of an arc-shaped Redirection. Thus, each subsequent gate has a larger cross-section than the previous. And it is in line with this this new concept, that one also expands these arc cuts consich. If now such arrangements should "work" as much as possible, as it is intended, then one will indispensable: The influence of course also in such or similar conical If friction is still present and is quite unavoidable, this "puncture" do not affect it, as is still the case with the measures shown in Figure 2.

The proposed continuous and rectilinear approach serves this very purpose conical Wiedee-enlargement of the barrel after each paragraph by putting it in a targeted Way is done.

This is because mathematical evidence can be provided that that the energy consumed by the turbulent friction in conical runs is continuous and equivalent from the flow energy present at the beginning of the cone section is set free if the cone is part of an imaginary square pyra = is mide, whose arbitrary side of the square corresponds to the length of the pyramid that belongs to it (Height to the top) behaves like the coefficient of friction of the turbulent flow "lambda to 4.0. The numerical value for" q "that comes into consideration here is after including = Common measurements between 0.032 and 0.040, with further deviations possible are. So it should be checked in practice. If the corresponding Conicity 1: (4 /) on = is held, then there is no back pressure in the barrel, like it occurs with a smaller or completely absent taper, and it arises also no static overpressure in the course of the flow, as is the case with a too large conicity is set free. The same applies to running routes, taken from a cone or a rectangular pyramid, and in general in all runs whose profiles consist of a common point (pole) radiate. The practitioner will prefer rectangular or trapezoidal cross-sections, also double trapezoids, which, however, should not be chosen overly must for all profiles deviating from the square in the basic relation given above "lambda" to 4.0, the value 4.0 can be redefined. It splits for rectangular Profiles in two values, of which the smaller (larger conicity) the longer Rectangular side is assigned and the larger value (smaller conicity) the shorter Page. With an aspect ratio of 2 to 1 and tA = 0.036, for example, the sides / heights = Relation for the longer side like "\" "h" to and for the shorter one shorter Side like "A":: 6/3, which means 1.35 in other words and numbers for the long side ß and for the short 0.675 ° / conicity means. Since the computational determination the respectively applicable = the relationships from the principle that defines the invention the optimal avoidance of static pressure in the barrel - to be more precise: from Increases or decreases in the static pressure in the course of the flow in the course - as a pure engineering task may be considered and not the content of the invention the presentation of "evidence" etc. can probably be dispensed with.

These relationships get a little more complicated when you go to the Simplification of the model production for the individual barrel = stretch their conicity only in one dimension, i.e. only in the length (width) of the rectangular profile - like done in Fig.3, or only in height (depth). This then becomes the slim one Wedge instead of the slender pyramid for the theoretical basic shape.

The formulas, reference numbers, can also be used for such designs and set up diagrams, which then once and for all have their definable scope to have. For example, for a square as the starting cross-section and "A" = 0.036 for the only widening side of the rectangle a total x-cone must be maintained th of approx. 2.2%. With an initial rectangular cross-section of 2: 1 this would be 3.2 '> to be used if the longer side is widened, but this is made up of several Reasons is not favorable.

On the other hand, it is only 1.7% conicity if one ver = the narrow side broadens. The resulting deviations from the ideal image of the flow process in a pyramid - namely low and limited coming and going again static pressures or low overall back pressure - remain almost imperceptible to this The often greater shortcomings of the previous manipulations are shown in Fig.1 or Fig.2, so that they can be tolerated. But if you want to correct it, you have to easy effort to find the direction and extent of small corrections.

For the sake of completeness it should be said that as theoretical Basic shape of the running routes, combinations of pyramids and wedges are also conceivable are. But they are both practical - in production - and theoretical - in terms of mathematical handling - even more complicated and cannot do any further Offer advantages. Furthermore, one could go beyond what has been presented so far for the purpose of completely exact equilibrium of friction and decrease in kinetic energy to the straight line Leave the cone leave and move on to curved surfaces. So much However, effort will hardly ever be necessary to achieve the goal invention. It is therefore recommended for the practical handling of the same, depending on the situation opting for a pyramid or a wedge and sticking to a straight conicity.

It is still necessary to adapt the design and solution to describe the cuts or the exits, because new errors are possible here must be avoided. In Fig.i and Fig.2 the two ways are already shown, which are primarily available for selection. The arched diversion is theoretical and most easily overlooked by calculation, as shown in Figure 3. The conicities in this drawing are exaggerated for better clarity what also applies to the other illustrations. The arched exit must be made every time begin with the cross-section by which the barrel cross-section just ver = has been reduced. It must by no means be narrower or it must continue to be so will. Nor should it be bigger right from the start. On the other hand lies a gradual widening analogous to that of the conical running routes in the sense of the whole. Such may even go beyond that, albeit in turn not too strong. In Figure 4, truncated pyramids have been assumed for the running routes namely square ones. Because every following segment is here with a square begins, the larger and actually also square end cross section must first over a short distance into a volume with approximately the same increase in cross-section be transformed by beveling the upper surface down to the level of the smaller one Square with simultaneous additional widening of this area. So that results the profile of the drainage itself. The necessary bills are almost in your head executable. With this measure, unwanted shock losses are avoided here.

Unfortunately, such arched diversions have, among other things, the disadvantage more complex space requirements on the form area, which is known to be forever too narrow and scarce. Because of this, right-angled leads are often unavoidable. Fig.5 shows right-angled Gates as a variant of Fig.3. The flow to the following one now acts here Running distance reducing heel as a collision surface, whereby about half of the kinetic energy of the stopped partial flow is destroyed. Therefore the gate cross-section must now compared to the cross-sectional reduction of the run - as for 25 years at to the State-of-the-art technology - can be increased by around 40% so that there is no throttling of the deflected partial flow occurs.

What has just been said also applies to the version according to Fig. 6, which from Fig.4 arises when the tangentially attached arc passes through the right-angled Derivative is replaced.

Now, however, in practice - for many reasons - one pulls flat ones and low profiles in front of the portrait format, as shown in Fig.7. The current diversion can no longer be as direct and manageable perform as in Figures 5 and 6.

Therefore, the question of the "correct" cross-section enlargement must be asked again here be asked. It has not yet been fully clarified. You still have them in there hidden, even if only quantitatively minor, uncertainties and possible ab = Deviations between intention and reality are tolerated as acceptable in practice. Because many observations indicate that the gate cross section always must be greater than the associated reduction in the barrel cross-section. Self with the waiver of a direct partial joint, which can be seen in Fig local increase in internal pressure is replaced, which decreases again during the lateral drainage takes place under his influence, they consume with it coupled changes in direction in this partial flow also add energy. That in turn would lead to a reduction in the subset compared to the desired proportion lead and thus to the accumulation of an increased flow in the main stream, if one of the Partial flow did not want to allow a larger cross-section. After the previous Observations are to be seen as a minimum of around 25% magnification. One very precise adjustment of the "correct gate cross-section, which at State of the art according to Fig. 1 as well as according to Fig. 2 was practically almost impossible to implement is, under the conditions that have now been created, by means of the simplest of experiments easily and safely possible. But in most cases it is enough to stick to it anyway an average value of 32% 0 as the amount of enlargement for this species right = angular cuts. The target subsets can be achieved with a few fO-en scatter. The figs. 7 and 8 show the modifications of Figs. 5 and 6 from vertical to flat gate profiles, with one in Fig Variant is indicated with dotted lines. It is useful to adjust the length of the short intermediate distance over which the profile conversion of the barrel is carried out will, to the width of the flat to coordinate flat gates.

All this advice on the design and dimensioning of the individual cuts are not considered to be included in the scope of the invention, but merely as practical instructions for the proper use and handling of the inventive idea with the help of already known relationships. Attempted to treat the wrong way or even backward-facing cuts are omitted as uninteresting here been.

To understand and justify the figures in the claims 3), 4) and 5) it should be added that the same on one hand, unfortunately only sparse information in the relevant literature and our own back calculations Experiments based on assumed mean value for "lambda" of 0.036. Of this The starting point is a tolerance for delimitation and because of the possibility of control by a third up and down, i.e. plus / minus 0.012 taken.

It is further taken for granted that all figures can be added in mirror image, so in such a way that the cuts after both Sides of the run are branched off to simultaneously two identical or at least related to fill castings that are equivalent to their casting conditions.

And then of course the individual running routes become symmetrical formed to their vertical mid-plane. Also a quantity = moderately unequal Distribution on both sides is possible, where = to then the simple symmetry through a "proportional" must be replaced.

The casting systems proposed here can be of particular advantage Education can be applied where - like temper = and steel mold foundries - The metal from the inlets first leads into so-called "printing ingots" which it only then flows over into the actual form. The "connections" of these Ingots on the mold usually have a much larger cross-section than it does for the filling process alone would be necessary because the printing pigs after finished Filling should still act as 1 "feeder". That the individual connections are not closer may be, than the bleed opening into the printing block, is clear from this the whole style of this description. But make the over = large connections Usually a meaningful amount = distribution totally impossible if not for them a casting system is connected upstream, which is largely independent independent of the connections clearly secures the desired, cheapest amount = distribution.

At the end of the description there should be one more possible misunderstanding be prevented. There was much talk of the crucial importance of the Avoidance of static pressure in the barrel and its individual sections. That relates of course, exclusively on the flow alone and that with it and from its permissible processes in the sense of Bernoulli's theorem. It is with that only a justified abstraction has been made from the overall event. Because with the filling of the form, of course, a continuous static runs Pressing in the gates and runs, which in the mostly vertical inlet channel propagates into it and the free height of fall that acts as a drive continuously reduced. All speeds eventually decrease to zero, while the static pressure in the horizontal run up to the specified maximum increases. However, this pressure is at all times over the entire length of the barrel out of the same size. The stream and its partial streams move through this pressure field through as if it weren't there.

The relationships between kinetic energies and frictional losses remain the same throughout the pouring system from the beginning to the end of pouring, so that all Operations proceed as described.

Claims (9)

Patent claims. 1) Casting systems with horizontal distribution runs, characterized in that that these runs at least one, but mostly several, weak in the direction of the current have conically flared sections, with one after each branched gate paragraph-like reduction of the cross-section it is taken, which is then again continuously enlarged. 2) casting systems according to claim 1), characterized in that the conicity of each individual section primarily the size of the generally with "lambda" designated coefficient in the known equation for the turbulent friction losses Metal flow is proportional and secondary to the geometric shape of the Running profiles is made dependent, in such a way that the continuously lost as a result of friction Energy in almost the same amount from the decrease in the kinetic energy of the flow can be replaced, which by their simultaneous reduction in speed is released as static energy. 3) casting systems according to claim 2), characterized in that the individual Running sections after the first cut in their basic geometric shape and Over their entire length - except for short transitions - excerpts from square Represent pyramids (truncated pyramids) whose square sides match the corresponding Increase in length by between 0.6 and 1.2% 0 of the same become larger. 4) casting systems according to claim 2), characterized in that the individual Running sections after the first cut in their basic geometric shape and Rectangular truncated pyramids over their entire length, except for short transitions represent, the larger side of the rectangle with the stump length by an amount larger which is between 0.30 and 0.64 ffi of the same, but multiplied by one Factor which is the quotient of the larger and the shorter side of the rectangle is formed by adding the size 1.0. 5) see sheet 2. 5) casting systems according to LMlspruch 2), characterized in that the individual running sections in their basic geometric shape and over their whole Length - except for short transitions - sections of chisel-shaped wedges of of constant thickness, where the variable side of their rectangular cross-sections with the associated partial length increases by a percentage of the latter, which is 1.2 units greater than the quotient of the variable and the constant rectangular side of the initial cross-section of the wedge = pieces, so by 2.6 to 1.6 fo for quotients from 1.4 to 0.4. These numbers are here as mean values, for each of which a spread of a third plus and minus is required is taken. 6) casting systems according to claims 1) and 2), characterized in that that for the formation of the individual running sections the Aus = management forms according to claims 3), 4) and 5) can be used in any order. 7) casting systems according to claims 3) to 6), characterized = characterized that the squares or rectangles are replaced by obtuse-angled, simple or equal-area Double trapezoids, symmetrical or asymmetrical, are replaced, with the mean values or the "weighted" mean values of the widths for the corresponding sides of the rectangle enter. 8) casting systems according to claims 3) to 7), characterized = net, that the individual sections of the run, including gates, form a vertical center plane are mirror-inverted symmetrically or mirror-inverted "proportional". 9) casting systems according to claims 3) to 8), characterized = characterized that their cuts are not introduced directly into the cast or cast, but indirectly via "printing ingots" or "feeders" connected in between or upstream. L e r s e i t e