US2491512A - Process for testing molding sand and apparatus therefor - Google Patents

Description

Dec. 20, 1949 w. H. MOORE 2,491,512

PROCESS FOR TESTING HOLDING SMID AND APPARATUS THEREFOR Filed lay 16, 1946 4 Shuts-Sheet 1 D66. 20, 1949 w, H, MOORE 2,491,512

raocn g ron TESTING MOLDING SAND APPARATUS THEREFOR 4 Sheets-Sheet 2 Filed May 16, 1946 INVENTOR.

Dec. 20, 1949 w. MOORE 2,491,512

PROCESS FOR TESTING MOLDING SAND AND APPARATUS THEREFOR Filed lay 16, 1946 4 Shoets-Shet s km! Imam M 75 m [a Q Mar nun-ml m 700 u ICTM ma 8' 4 511% am gammy punm or mums I silk! ES cum/x ummmv xm') RWEWW peroemrrmv 0/ Wales Pea-Wm M Iva/5M5 COMPEQ'JSIOII li /85. PER 50. 1M INVENTOR.

Patented Dec. 20, 1949 PROCESS FOR TESTII-IG MOLDING SAND AND APPARATUS THEREFOR William H. Moore, Cleveland Heights, Ohio, assignor to Meehanite Metal Corporation, a corporation of Tennessee Application May 16, 1948, Serial No. 670,219

Claims. (Ci. 73-116) My invention relates to material testing, and testing devices in general, and more particularly to a process for determining the toughness of molding sand in' terms comparable to the determination obtained by multiplying the compression strength of the sand by the deformation of the sand under the compression load, and apparatus for carrying out the process.

2 by the toughness, it is important to control the toughness.

Toughness in a molding sand has the same meaning that it has many other material. For instance, glass is not tough because it can be fractured by a slight blow although .it is capable of supporting quite a heavy load if the conditions are right. On the other hand, pure rubber is not tough because, although it cannot be fractured readily, it changes shape very easily because it has no rigidity. A material which can be deformed appreciably but yet is capable of withstanding heavy loads without deformation is a tough material.

In the art of sand casting metals, a certain amount of toughness is required in the foundry sand in order that the sand can deform without breaking. For instance, in closing a foundry mold, a projecting ledge of sand may be fractured and fall into the casting cavity if the sand had a low toughness, whereas a sand with a high toughness will merely change its shape and accommodate itself to the closing operation. In the same way, a projecting ledge or rough spot on a pattern would cause the sand to tear away when the pattern is withdrawn from the mold. With a tough sand, the sand will deform and remain in position so that it can be pushed back into place readily when the pattern has been withdrawn.

During the actual casting operation, the blow from the falling metal entering the mold through the gate would fracture a sand of low toughness and cause loose sand particles to be included in the final casting. A sand of reasonable toughness will be able to accommodate itself to the ferrostatic pressure of the metal without deforming. In the 0-30% clay range. the degree of toughness of the molding sand varies with the amount and type of clay bond in the sand, all other conditions being equal. Thus, the toughness value is an indication of the amount of clay bond in the sand. Too high a clay bond will lead to scabs, buckles, blows and similar casting defects, whereas too low a clay bond will lead to washes, cuts, drops, mold peeling and so on. It is therefore extremely important to control the amount of clay bond in the-sand, and as this is reflected The present accepted method of measuring sand toughness is an indirect one. The compression strength is multiplied by the deformation and this answer times 1000 gives what is known as the resilience or toughness. This is essentially a method depending on accurate laboratory readings as in multiplying two figures together, any error in one of the readings becomes multiplied.

In addition to this, it is not practical to obtain an index of toughness by the present means in the case of a dried sand, a baked core, or where it is desired to know the toughness of a sand at elevated temperatures. This is because at high temperatures (temperatures at which metals are cast) we cannot measure-the deformation under load because it is affected by expansion of the sand itself due to the influence of heat.

Therefore, an object of my invention is to provide a process for determining the toughness of molding sand.

Another object of my invention is to provide a process for determining the toughness of molding sand in terms comparable to the determination obtained by multiplying the compression strength of the sand by the deformation of the sand under the compression load.

Another object of 'my invention is to provide I a process for measuring the toughness of any sand whether green, dried or baked, at room temperature, or at temperatures corresponding to the metal casting temperature, or at any intermediate temperature.

Another obiect of my invention is the provision of a process for measuring the residual toughness or retained toughness of a molding sand that has been subjected to casting conditions.

Yet another object of my invention is the provision of apparatus to fracture a specimen of molding sand in shear, and measure the work required to fracture the specimen.

Another object of my invention is the provision of apparatus to position a specimen of molding sand in the path of swing of a pendulum, whereby the pendulum may strike the specimen and fracture the specimen in shear, with provisions for measuring the work required by the pendulum to fracture the specimen.

A still further object of my invention is the provision for apparatus to position a specimen of molding sand in the path of swing of a pendulum, the provision of a heating furnace to raise the temperature of the molding sand prior our:

3 to being tested, and the provision of a calibrated scale to indicate the amount of work required by the swinging pendulum to fracture the specimen in shear.

Another object of my invention is the provision of a swinging pendulum testing device for testing molding sand specimens, and a heating furnaceassociated therewith to heat the specimen outside of the path of swing of the instrument pendulum arm, and the provision of means to move the specimen from the heating zone of the furnace into the path of swing of the pendulum arm, in order that the specimen may be heated and fractured quickly without the loss of any substantial amount of heat from the specimen.

' Other objects and a fuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure l of the drawings is a perspective illustration of my improved testing apparatus capable of carrying out my testing process;

Figure 2 is a greatly enlarged illustration of a suitable type of removable heating furnace to be used in connection with the apparatus illustrated in the Figure 1, a portion thereof being broken away to show the interior construction;

Figure 3 is an enlarged perspective view of the pendulum striker at the moment of impact with the specimen;

Figure 4 is a perspective view of an alternative type of equipment provided in accordance with my invention, and capable of carrying out my improved testing process, the heating furnace being attached below the table of the testing instrument and having a portion thereof broken away to illustrate the construction of the interior thereof;

Figure 5 is a broken away portion of the furnace illustrated in Figure 4 and illustrating the position of the specimen within the furnace for heating prior to being tested;

Figure 6 is a curve of toughness in units plotted against percentage of moisture in a given molding sand as measured by correct measurement on my improved testing equipment by my improved testing process;

Figure 7 is a curve similar to that of Figure 6 as obtained by multiplying the compression strength of the molding sand by the deformation of the molding sand under the compression load, and multiplied by one thousand for the purpose of eliminating decimal scales;

Figure 8 is a graph illustrating the deformation of the particular illustrative molding sand under the compression load indicated in the Figure 9;

Figure 9 is a graph illustrating the compression strength of the particular molding sand as plotted against moisture contents; and

vFigure 10 is a graph illustrating the results obtained by my improved process and apparatus as used to determine the degree of toughness of a particular type molding sand as indicated in the title under the influence of increased temperature.

With reference to the drawings, I illustrate a preferred embodiment of my apparatus to carry out my improved testing process. Essentially, it comprises a specimen holder 23, a swinging pendulum 26, a striker 2|, an idle pointer 25, and a scale 24 which is calibrated according to the weight of the striker 2| and the length of the pendulum 26. For convenience, I have provided a base Ill to which I have mounted two upright sion load, and the result multiplied by one thouhers I! are suitably attached to the upright support arms II and are employed to support the graduated scale 24, as well as the pendulum with the striker 2| thereon and the idle pointer 25. The pendulum 26 and the idle pointer 25 may be mounted in any suitable well-known manner, and are illustrated as being mounted upon a pivot member 21. The pendulum 26 is freely swingable about the pivot 21, and is counterbalanced by means of a counterbalance 28. The idle pointer 25 is so mounted upon the pivot 21, that the idle pointer will remain in any position or angle to which it may be moved. Therefore, by the provision of a contact member 3 I, on the idle pointer 25, the pendulum 26 may contact the member 3| and move the idle pointer 25 in a clockwise direction. Thus, the idle pointer 25 will be moved along the scale 24 a distance according to the resistance offered by the specimen l3 to the free swing of the pendulum 26 and the striker 2 I. That is, inasmuch as the pendulum 26 and the striker 2| will possess a potential energy when held in the position illustrated in the Figure l, the amount of energy released by the free swing of the penduluin and the striker may be calculated by the weight of the striker and the distance through which it swings- However, I have found it convenient to graduate the scale 24 in suitable arbitrary toughness units comparable to the units normally-obtained by the well-known methods of toughness testing used today; namely, by multiplying the compression strength of the sand by the deformation of the sand under the compressand. Therefore, a direct comparison or reading may be obtained without calculation. In order to position the striker 2| and the pendulum 26 at a fixed determinable position prior to each test, I have provided for a releasing mechanism 22 to hold the pendulum and striker in the position illustrated. The pendulum and striker may be released to travel through the arcuate path by pulling the release 22. For convenience, I have adopted a length for the pendulum 26 from the pivot 21 to the striker 2| of 50 cms. The striker 2| is detachable and can be altered to suit the sand being tested if necessary. That is, the pendulum arm 26 is threaded on the end thereof and the striker 2| held in place by means of a nut 32. Thus, with a sand of high toughness, a heavier weight would be used to make sure the specimen is completely fractured on releasing the pendulum.

To conduct an elevated temperature test, I

have provided a furnace 30 to be used in con- Junction with the apparatus illustrated in Figure 1. This furnace is shown in Figure 2. Essentially, the furnace comprises an inner tube member l6 and an outer shell 31. A peep hole 20 is provided in the shell 31. A p urality of heating elements l5 are provided within the furnace between the shell 31 and the tube l6, and maybe energized by any suitable method, such as by connecting with an electrical outlet. A heating element guide I4 is employed to position one end of the heating elements I5, and the other end of the elements are secured to the top of the furnace. A refractory'block 29 is secured to the base I of the apparatus as illustrated in the Figure l by any suitable means, and the guide I is designed to fit closely therewith. The shell 31 is insulated by insulating material IS in order to keep the shell 31 cool, and to conserve the heat energy. Further, a thermocouple I1 is prosupport members ll. Cross arm support memvided in conjunction with the furnace 30 and may be positioned upon the top of the furnace as illustrated, and connected to the interior of the tube It by thermocouple wires in any suitable manner. Also, I have provided for handles it to be positioned on either side of the furnace 30 for convenience of placing the furnace in position for heating, and for removing the furnace prior to testing the specimen.

In operation, a specimen l3 of the moldin sand is provided and placed in the holder 23.

The specimen l3 may be made up of green, dried or baked sand to correspond to the part of the mold to be tested. If a core sand or a dry sand is to be tested, it is of course baked first. The specimen and holder are then positioned in place by means of the refractory block 23. The furnace 30 is then positioned to enclose the specimen l3 and the holder 23 as illustrated in the enlarged view 01' Figure 2. The furnace temperature is then raised to the temperature to which the specimen I3 is to be subjected, and held in place for a standard soaking. It is then removed, and

the pendulum is released and the striker 2| caused to strike and fracture the specimen l3. As previously stated, a striker 2| is used of such weight and properly counterbalanced by the counterbalance 23, that more than enough energy will be available to break the specimen. Therefore, the striker 2| will carry past the holder 23 after the specimen II has been fractured. It is at this moment that the pendulum 23 contacts the member 3| of the idle pointer 25 and moves the idle pointer 23 along the graduated scale 24.

'Ihe toughness is then read directly off of the graduated scale 24. Of course, as before indicated, if a mathematical index of toughness is required, it is only necessary to multiply the weight of the striker 2| by the distance through which it swings after breaking the specimen.

In the above described mode of operation, the furnace is used to conduct high temperature tests. If a cold test is to be made, the heating step is merely omitted.

In the Figure 3, I have illustrated an enlarged view of the striker 2| at the moment it contacts the specimen l3. In this figure, it can clearly be seen, that the direction of travel of the striker 2| in relation to the longitudinal axis of the specimen II is transverse, or at right angles, thereto. Thus, inasmuch as the specimen i 3 is securely held in the holder 23, the stress placed upon the specimen i3 is entirely in shear. The striker 2| is of such length that a close clearance is provided between the top surface of the holder 23 and the face of the striker 2|. Further, a semicircular striking notch 38 is provided on the striker 2| to contact the specimen l3. Therefore, the blow delivered by the striker 2| is delivered with full force to the entire specimen l3 instead of a portion of the blow being absorbed by deforming the surface of the specimen.

Oftentimes it is desirable to test a molding sand specimen after it has been heated and allowed to cool to any lower temperature, or down to'room temperature. Therefore, when a .test of this nature is desired, I merely allow the speciwhereas if it is not tough enough, it will wash away during the actual casting operation.

By means of heating the specimen i3 to any desirable temperature by the furnace 30. I am able to test the reaction of the sand at any given distance from the contact surface between the molding sand and molten metal. That is, by this means I am able to accurately reproduce the operating conditions under which the sand will be subjected, and therefore obtain a correct knowledge as to the behavior of the sand on the interior of the sand body used, in that specimens can be made corresponding to the interior of the mold. Because only a relatively thin layer of sand is actually heated to the temperature of the metal during the actual casting operation, and the rest of the sand body is heated to lower and lower temperatures as the distance becomes further from the contact surface, a series of tests may be'made from the highest temperatureat the contact surface down to a lower temperature corresponding to a given distance from the contact surface. Thus. by running a series of tests at various temperatures upon a given molding sand composition,,I am able to accurately obtain the information necessary to predict the reaction of the molding sand under actual operating conditions.

In the Figure 4 of the drawing, I illustrate a second embodiment of my invention in which the furnace 33 is positioned below the base It. By this construction, I am able to more quickly move the specimen it from the heat of the furnace to a position to be contacted by the striker 2|. In this embodiment, the furnace 3|) is provided with a furnace tube 3| extending from the top to the bottom thereof. In other respects, the furnace itself is essentially the same, employing an outer shell 31, insulating material i9, and heating elements l6. However, as will be evidenced, I have provided for a movable support 33 comprising a tubular member into which the specimen holder 23 may be inserted. Thus, the specimen l3 may be mounted in the holder 23 and moved to the central heating area of the furance 3|), as illustrated in Figure 5. The thermostat l1, mounted upon the base ill, will indicate when the temperature of the furnace is of the proper selected value, and after a suflicient period of soaking, the movable support 33 may be moved upwardly to move the specimen into the path of swing of the striker 2|. I have provided in this modification of my improved apparatus, for a guide member 35 to accurately position the holder 23 and the specimen l3 in the line of travel of the striker 2 i. The guide 35 may be held upon the base ill by any suitable means such for example as the bolt 36. This improved embodiment of my apparatus may be mounted as a bench with the furnace 30 suspended below the base III in an out-of-the-way position.

Prior to my invention, the toughness of a sand at elevated temperatures could not be measured by any other means than the described computation method, which comprises the multiplying of the deformation by the compression load, and multiplying the result by one thousand. The measurement of compressive strength at high temperatures is done by means of a dilatometer, which is essentially a laboratory measurement requiring more than average skill on the part of the operator, and requiring strict attention to detail to make all tests comparable and reproducible. With my improved apparatus and process for treating the toughness, comparable and rt ,)IOdl10ib1 tests are simple and convenient to make.

To indicate how far the sand toughness indicator apparatus and the process used for testing the sand is a, measure of the toughness of the sand is the accepted sense of the work, I have included typical curves in the Figures 6 to 9. The curves in the Figures? to 9 are obtained bythe well known method used today of obtaining the compression strength of the sand and the deformation of the sand under the compression load, and multiplying these two results together to obtain a unit of toughness. To illustrate, the graph in the Figure 9, which is entitled "Compression in lbs. per sq. in., is the result of plotting the compression strength of a particular sand against moisture content. The compression strength is indicated along the vertical axis of the graph, and the percentage of moisture of the molding sand is indicated along the horizontal axis. In the Figure 8, which is entitled Deformation in inches, the deformation of the same sand has been plotted against the moisture content. In

eter standard specimen with a 100 gram striking weight and a 50 cm. striking height. For regular testing, I prefer a 1 /8 inch diameter specimen.

Although I have described my invention with a certain degree of particularity in its preferred form, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. Apparatus for determining the toughness of molding sand interms comparable to the determination obtained by multiplying the compression strength of the sand by the deformation of the sand under the compression load, comprising a this graph, the deformation in inches is plotted on the vertical axis and the percentage of moisture is plotted along the horizontal axis. In the Figure 7, which is entitled Resilience in units or toughness (compression deformation X 1000), the compression strength is multiplied by the deformation and plotted against moisture content. In this graph, the vertical axis is the unit obtained by multiplying the compression by the. deformation by 1000, and the horizontal axis is again the percentage of moisture in the molding sand. The units are multiplied by 1000 forthe purpose of eliminating the decimal in the graph scale. Particular attention is called to the highest peak of toughness obtained by this method. This point is illustrated on the graph by the reference character M.

The Figure 6 is entitled Toughness in units, direct measurement on sand, toughness indicator, 1000 gm. striker 2" dia. specimen, and is a graph obtained by testing the same molding sand as was tested to obtain the graph illustrated in the Figures 7 to 9. In this figure, the vertical axis is an arbitrary scale of toughness and the horizontal scale is again the percentage of moisture in the molding sand. In the tests used to obtain this graph, the sand was tested exactly as described in the foregoing discussion of my invention. It will readily be seen, that the comparison between the graph obtained by my improved method and apparatus is amazingly similar to that obtained by the described mathematical com utation. The point of maximum toughness is illustrated in the Figure 6 by the reference character 40. This point very closely confpares to the maximum point illustrated in the Figure '7 by the reference character 4|.

In the Figure 10 of the drawings, I have shown three curves obtained by my improved apparatus and process. This graph is a plotting of arbitrary toughness units along the vertical axis against the temperatureto which the specimen is raised before testing. This graph is entitled Temperature of test degrees Fahrenheit. The two broken line graphs represent repeat tests made on a cereal bonded core sand and are indicated as test No. 1 and test No. 2. These repeat test curves are shown to illustrate the reproducibility of the result in that the curves follow exactly the same trend in both cases. The full line graph is a graph obtained by testing a resin bonded core sand. All tests on this graph were made on a. inch diamswinging pendulum, a striker mounted on the swinging pendulum, a specimen holder for holding a specimen of molding sand, said specimen holder serving to holdthe specimen with a portion thereof extending from the holder, 8. heating furnace positioned outside the path of swing of said striker, a movable support to hold the specimen holder and specimen in a first position within the furnace, and a second position with the portion of the specimen extending from the holder located in the path of swing of the said striker, and means to release said pendulum to strike said specimen substantially immediately upon positioning of the specimen by said movable support to said second position, thereby permitting the specimen to be heated within the furnace and subsequently moved into position for testing, the toughness being determined by the work re quired of the swinging pendulum and striker to fracture the specime in shear.

2. The method of evaluating a molding sand for toughness particularly during the casting interval, comprising the steps of mounting the specimen in a holding device with a portion thereof extending from the holding device, thereafter applying heat of an intensity comparable to the heat radiated from the surface of the molten material to be cast and for a pro-selected period of time which is less than the pouring time required to pour a casting in a mold made of said molding sand, thereafter striking the portion of the specimen extending from the holding device with a transverse blow of predetermined magnitude substantially immediately at the end of said preselected period of time and with a speed to produce the fracture substantially instantaneously,

and determining the work required to fracture the specimen as a measure of the toughness.

3. Apparatus for determining the toughness of molding sand in terms comparable to the determination obtained by multiplying the compression strength of the sand by the deformation of the sand under the compression load, comprising a specimen holder for holding a specimen of molding sand, said specimen holder serving to hold the specimen with a portion thereof extending from the holder, a heating furnace, said furnace and specimen holder being relatively movable to a first position with the specimen within the furnace, said furnace and specimen holder being relatively movable to a second position with the specimen exposed out of the furnace, an impact member, means to move the impact member to strike the portion of the specimen extending from the specimen holder in said second position with a transverse blow of predetermined magnitude, means to hold said impact member against movement while said furnace and specimen holder are in said first position, and means to release said impact member for movement to strike the specimen after movement of the furnace and specimen holder to said second position.

4. Apparatus for determining the toughness of molding sand comprising a table, a swinging pendulum mounted above said table, a striker mounted on the swinging pendulum, a specimen holder for holding a specimen of moldingv sand, said specimen holder serving to hold the specimen with a portion thereof extending from the holder, a heating furnace below said table, said table having an opening therethrough, a movable support to hold the specimen holder and specimen in a first position within the furnace, and move the specimen holder and specimen through said opening to a second position with the portion of the specimen which extends from the holder being above the table in the path of swing of the said striker, and means to release said pendulum to strike said specimen substantially immediately upon positioning of the specimen by said movable support to said second position, thereby permitting the specimen to be heated within the furnace and subsequently moved into position for testing, the toughness being determined by the work required of the swinging pendulum and striker to fracture the specimen in shear.

5. Apparatus for determining the toughness of molding sand comprising an impact member, means to move said impact member along a fixed path, a specimen holder for holding a specimen of molding sand, said specimen holder serving to hold the specimen with a portion thereof extending from the holder, a heating furnace, a movable support to hold the specimen holder and specimen in a first position within. the furnace, and a second position with the portion of the specimen which extends from the holder located across the path of said impact member, and means to release said impact member to strike said specimen with a blow of predetermined magnitude, thereby permitting the specimen to be heated within the furnace and subsequently fractured by a transverse blow in a period of time related to the time required to an a casting mold made of said molding sand;

WILLIAM H. MOORE.

REFERENCES CITED The following references are of record in the file of this patent:

onrfnn STATES PATENTS Number Name Date 1,329,192 McAdam, Jr. Jan. 27, 1928 1,789,848 Skidmore et al. Jan. 20, 1931 2,279,368 Dietert Apr. 14, 1942 2,377,590 Talalay June 5, 1945

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