CA1039532A - Immersion sampler for molten material having a venturi entrance passage - Google Patents

Abstract

ABSTRACT

An immersion molten material sampling device of a type usable to obtain a sample of molten steel from a furnace. The device includes a sec-tional mold structure having a vented sample receiving cavity and an entrance passage for molten material to flow into said sample receiving cavity. The entrance passage is characterized by the inclusion of a venturi which minimizes red stance to flow and effects smoother flow of molten material into the sample receiving cavity. The venturi throat which is surrounded by thick wall structure of the mold acts as a thermal valve to prevent loss of sample from the sample receiving cavity by maximizing heat removal from the molten material through heat conduction to the thick wall structure of the mold surrounding the throat. The resulting high heat conduction away from the molten material at the venturi throat, once the molten material has stopped flowing into the sample cavity, causes the material in the throat to freeze first thus trapping the sample inside the sample cavity to prevent loss of molten material therefrom during removal of the device from a bath of molten material. The body of the sampler is preferably of the split mold type with a gasket of porous material between the mold halves to provide more uniform venting for the sample receiving cavity.

Description

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This invention relates to apparatus for obtaining a sample of molten material.
For a long time there has been a continuing effort, particularly by individuals associated with the steel industry3 to provide a satisfactory method and apparatus for the collection of solidified samples of molten - material to be used for constituent analysis. Samples have been obtained by - pouring molten material into a mold having a cavity configuration of a desired shape. Samples have also been obtained by immersing the closed end of a metal or heat-resistant glass suction tube or a mold of more complex -configuration into a bath of molten material so that upon destruction of an end closure molten material would be sucked up into the device. Suction was achieved either by connection to suction producing means or using a sealed evacuated device. There have also been utilized immersible mold structures having a top, bottom, or side entrance passage to a cavity of a desired shape, the cavity of the mold being filled by inflow caused by gra~ity or by t~e hydraulic head of the molten material. In these latter modifications the sample receiving cavity must be vented to atmosphere.
It has long been known to obtain samples comprised o~ a head portion of any desired shape attached to a stem portionO It is also known in the prior art to employ samplers comprised of split mold structures wherein the mating parts of the mold when placed toge~her form a sampler having one or more sample receiving cavities, one or more vent passages for -~
venting the cavity or cavities to atmosphere and an entrance passage the ;
; normally open end of which is temporarily closed by ~ destructible ~aterial to prevent ingress of slag which may exist in a bath of molten material by maintaining the entrance passage closed until the sampler has been immersed into a molten bath below the level of any slag existing therein. A relative-' ~:
ly recent patent disclosing many of the foregoing features is United States Patent 3,646,816 issued to Hance et al and assigned to the same assignee as the present application.
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Samplers of the type where the molten material enters the sampler through a passage having its opening in an end face at the immersion end of a mold have certain advantages, however, considerable difficulty has been experienced with such samplers due to run-out of the material being sampled as the sampler is withdrawn from a bath of molten material thus resulting in the samples being hollow or tubulated instead of solid all the way through.
Some difficulty has also been experienced with split mold samplers in that molten material tends to run between the mold halves, which are almost always slightly warped. This results in the production of unwanted flashing on the edges of the sample.
In order to prevent loss of gas from the sample cavity of a mold structure it is known as taught in United States Patent 3,315,529 to include, in an evacuated apparatus for taking samples from melts, a multi-part mold structure having a cooling jacket disposed about wall structure defining a sample receiving cavity and wall structure defining a cavity which is a portion of the flow passage which conveys molten material to the sample receiving cavity. A metal plate or disk is secured between the mold sections the walls of which define the above cavities~ This platle has a through passage which provides a narrow or restricted path for the flow of sample to the sample cavity. The through passage opening is provided with sharp edges, by using any of several configurations illustrated in the patent~ and the plate and its parts tinned or covered with a non-gassing fluxing agent so that upon solidification of the molten material in the sample cavity the ;
material closes around the disk and will weld itself thereto particularly if the above mentioned sharp edges are provided.
It is also taught in French Patent 1,436,377 to provide the tube - of an evacuated glass tube type of sampler with a narrowing in order to re-- duce the speed of circulation during the aspiration of the liquid and to ensure the formation of a compact sample, free of hollow areas. United States Patent 3,455,164 teaches the use of sampler bodies made of a porous :- -, 1~3953Z ~ ~
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shell molded sand. Such materials while satisfactory for some applications are not suitable for use in a sampler wherein it is required to exclude substances from the sample which are given off by the resin coated binder materials utilized in the shell molding process.
Applicant has discovered that a totally expend-able immersion sampler device of the split mold type can be constructed which includes means to prevent the form-- ation of unwanted flashing on a sample while enhancing . 10 venting in a manner to promote a uniform fill, and means --~
further promoting uniform fill and at the same time functioning to prevent run-back, i.e. loss of sample from -the sample receiving cavity of a mold upon withdrawal of the sampler from the bath of molten material and which ;~
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does not require the use of a cooling jacket to cool an -orifice plate and the walls defining cavities of a mold to promote freezing of the sample.

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~ ccording to the present invention, there is provided an immersion sampler cGmprising a split mold - body with mating parts which are recessed to define a sample cavity and a flow passage through which a sample of molten material can flow into the cavity when the : sampler is immersed in the molten material, and a gasket capable of withstanding the molten material between the mating parts for reducing the formation of flash on the : solidified sample, the gasket being sufficiently porous ~ :
to allow venting therethrough of gas from the cavity as the sample enters therein.
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Applicant's invention may best be understood by reading the following description together with reference to the various figures of drawing.
: The invention will now be described, by way of ji example only, with drawings in which , . Figure 1 is a side elevation partly in section ~. :
showing the relationship between the mold, a holder ~: therefor, a closure member, and a handle or manipulator used for immersing the mold in a bath of molten material, Figure 2 is a sectional view along the line 2-2 ` of Figure 1 with mold inserts omitted, Figure 3 is a sectional view taken along the `
line 3-3 of Figure 1 with mold inserts omitted, ' ~

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Figure 4 is a sectional view taken along the line 4-4 of Figure 1, ,, ; Figure 5 is an exploded side elevation of the sampler of Figures 1-4 showing the location of a porous gasket in accordance with applicant~s invention, and Figure 6 is a plan view of the gasket of Figure 5. `
Referring to Figure 1, there is shown an i ersion sampler device for obtaining a sample from a bath of molten material. A split mold - 11 only one-half lla of which is shown in Figure 1 is comprised of two - 10 identical halves which are assembled in face-to-face relation with or without a gasket as shown in Figures 4 and 5. The mold halves are preferably made ` of a ceramic material called cordierite which is composed of alumina, magnesia~ and silica. The mold halves may be cemented together with a refractory cement or otherwise secured in a manner which avoids leakage of molten material into any space between the halves which might exist should ; the faces of the mold halves not be perfectly flat. Generally the mold halves will be slightly warped so that either a cement or a gasket should be used. It has been found by applicant that by using a gasket made of a material which is porous that not only is leakage of molten metal into spaces between the mold halves prevented, thus avoiding flash or fins on the sample upon solidi~ication of the molten material, but that additionally more uniform venting of the sample cavity appears to be effected which results in a complete fill with varying amounts of superheat of the molten material. In view of the foregoing a gasket 20~ as shown in Figure 6 is inserted between the mold halves as shown in Figure 5. The gasket 20 is made of a porous material that will withstand exposure to the molten material of the bath. For obtaining samples of molten steel it has been found that a gasket about .01-.02 inch thick made of felted refractory fibers which is a material obtainable from Refractory Products Company, Mount Prospect~
Illinois under the trademark FIBERFRAX has been found suitable. After the .. ' ~

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gasket is properly placed and the mold ~lalves secured as by a piece of adhesive tape (not shown) a heat destructible cap 12 is affixed thereto.
For obtaining a sample of steel the cap :L2 is preferably thin-walled and of mild carbon steel so that it will quickly melt away after immersion into the bath. As is well known to those ski:Lled in the art such caps are utiliz~
ed to prevent the ingress of slag when the immersion sampler penetrates a slag layer as it is being inserted into the molten bath to obtain a sample therefromO Those skilled in the art have found it desirable sometimes to include a thin coat of paper, plastic, or other suitable material on the outside of the cap 12 to prevent slag from sticking to the cap. If slag sticks to the cap when the cap is destroyed slag might enter the sampler which, of course3 is undesirable. No such coat is shown on cap 12 since it per se is not always necessary and forms no part of applicant~s invention.
It is also to be understood that when no slag is present no fusible cap is necessary. `
= The sampler unit comprised of the assembly of the two identical halves lla of the ~old 11 with gasket 20 between them and the cap 12 is in-serted into the end of a protection tube 13 which may be made of cardboard, graphite, ceramic, or other suitable material and secured therein as by 20 means of any suitable adhesive to for~ a device ready for use. As those skilled in the art are aware, a sampler device as just described is with~
drawn from a supply thereof and pushed onto a manipulator or handle which may be in the for~ of a black iron pipe 14 of suitable length. In order to regulate the distance that the pipe extends into tube 13 it may be bent as at 14a. The binding action between a cardboard tube and the bend in the pipe, which is otherwise a loose fit within the cardboard tube, is sufficient to secure the sampler device on the pipe. Of course other means may be used as a tube stop an~ to secure the tube to a manipulator. -~
Since the mold halves lla are identical it is only necessary to describe one of them. The material of the mold halves may be any which will ~ . ... . ~ . ..

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withstand immersion into the molten baths at the usual bath temperature and -~
~hich ~ill not conduct heat in a manner to prevent filling of the mold.
When taking samples of molten steel the material must withstand temperatures up to and in excess of 3,000 Fahrenheit in which case the ceramic mentioned above is suitable. The mold piece lla may include a recess llb at the - immersion end thereof. The term "immersion end" as utili7ed throughout the specification and claims is intended to refer to that end of the immersion sampler which first enters the bath of molten material. As viewed in Figure 1 it is the lower end facing cap 12. The recesses llh together form 10 a countersunk part of a mold which can be utili~ed to support a disk 17 to ~
close an entrance port llc and may be of any material which may be melted -- by the heat of the bath. The disk can be of a material which will melt and thereafter mix with the molten material which enters the mold structure.
As well known to those skilled in the art it is sometimes desirable to utilize a deoxidizing material, for example aluminum, to kill a sample of steel as it enters the mold. For this purpose it has been found desirable to make disk l? hat-shaped, as shown, so that it will extend into the entr-ance port of the mold. The reference number llc designates the entrance port which, in the device illustratedg is a part of the flow passage for material enterjng the mold. Wall portions of the mold are constructed and arranged to form a venturi lld. As defined in Websterls New International Dictionary, Second Edition, Unabridgedg Published 1954, a venturi t`ube or - venturi 1, as used in hydraulics is defined as a short tube~ inserted in a pipe line, whose internal surface consists of two truncated cones connected at the small ends by a very short cylinder called the "venturi throat"O In applicant's specification and claims the term "venturi" is employed with reference to the cone shaped sections connected by the short small diameter passage which when the mDld halves are assembled form the venturi lld having a venturi throat lld' The function of the venturi tube org as commonly designated, the venturi in accordance with applicant's invention is to - . . .
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minimi~e resistance to the inward flow of molten material to the sample cavity and effect a reduction in the pressure of the inwardly flowing material. The venturi throat functions as a thermal valve to help prevent ` back-flow of the molten material. The thicker wall structure of the body in the region of the throat maximizes removal of heat from the molten material in a manner such that when the inward flow ceases the material free~es in the throat thus trapping the sample inside the sample cavity. Applicant has also found from an inspection of cast samples obtained from samplers constructed in accordance with his invention that the venturi appears to 10 effect a marked reduction in splash as the molten material enters the sample --receiving cavity thus producing more homogeneous samples. The end of the venturi opposite the immersion end opens into the sample cavity comprised of the sections lle and llh of the mold.
Those skilled in the art are aware of the fact that for various reasons the shape of the sample cavity i9 a matter of choice and may be of almost any conceivable configuration. As shown in United States Patent

2,970,350 the cast sample may be in the form of a head and stem obtained from a mold such as is depicted in Figure 2 of that patent or as indicated in the description of Figure 4, column 3, lines 58-62, of that patent~ "The 20 mold body 4, which.~....... ~ is provided with a hollow space or mold cavity 5 which may contain various inserts for the purpose of producing castings of complex configuration." While for applicantls purpose a ceramic mold is preferred it is believed clear that the shape of the sample to be cast may he of any desired configuration and other materials may be used for the mold as a matter of choice to suit the application. ;
Still referring to Pigure 1, a semi-circular recess lle in each mold half joins with a flat bottomed somewhat oval recess llh. These recesses cooperate with similarly recessed portions of the other mold half~
when the mold halves are assembled, resulting in a sample receiving cavity which produces a sample piece comprised of a flat head-like portion affixed . , . .

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to a round stem. As known to those skilled in the art it is customary, in order to proYide the round stem of the sample with superior surface charac-teristics and promote the flow of molten material into the cavity portion formed by the recess llh, to include a tubular element 15 of heat resistant glass, quartz, or a suitable ceramic, such as corderite which may be dis-posed in the recesses lle and secured therein as by the use of a refractory cement. In order that air and gas may escape t`rom the mold as the molten material enters the mold venting means is provided. For this purpose a groove lli is included in each mold half whichg when the mold halves are assembled, results in the formation of a passage of small diameter which serves together with the porous gasket 20 as means for venting the sample cavity and hence the entire mold. To maintain the mold halves in proper alignment it will be found desirable to provide in each mold half a projec-tion such as a rib llf and a recess llg of complementary shape. The projec-ting rib llf is best secn in Figure 2~ the recess llg of complementary shape is best seen in Figure 3 and the manner in which the ribs and recesses co-operate is best illustrated in Figure 4.
While mention has already been made of the possibility of supp- ;-~
- orting a disk of deoxidizing material such as aluminum in the recess llb, ;
it is to be understood that the amount of aluminum to be used has been found to be somewhat critical. Too much not only spoils the sample for spectro~
- graphic analysis but also appears to cause loss of sample due to run-back.
Too small an amount of aluminum results in incomplete deoxidation of the sample. Applicant has found that using a mold having a configuration in accordance with his invention as shown and wlth dimensions such that the weight of a steel casting obtained from the mold is about 87 gramsg for this weight of steel the weight of the aluminum should be about 0.2 gramsO If the weight of the aluminum in disk 17 needs to be augmented this can be - accomplished by adding a quantity of deoxidizing material 16, such as alum-inum foil, a small disk~or the equivalent weight needed in some other form in ''',:. ' - .' - '.''' . ,.' : ' . : ~ ., - ::

~39532 one of the end portions of the venturi lld, as shown in Figure 1.
The immersion sampler device as above described employs low cost materials and is relatively inexpensive to manufacture. It is easily broken open to retrieve the desired sample. The device used for illustrative purposes contemplates a mold body approximately five inches long and having - a diameter such that it may be cemented into a cardboard tube having an inside diameter of about one and five-sixteenth inches and a wall thickness of about one-quarter to three-eighths of an inch.
While in describing applicant's invention specific materials have been referred to and a sample cavity having a shape to produce a ping-pong paddle-shaped sample has been illustrated, it is clearly to be under~
stood that more than one sample cavity may be fed through a single venturi and other changes may be made without departing from the scope of applicant~s invention. Accordingly, the invention is to be limited only by the scope of the appended claims.

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Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An immersion sampler comprising a split mold body with mating parts which are recessed to define a sample cavity and a flow passage through which a sample of molten material can flow into the cavity when the sampler is immersed in the molten material, and a gasket capable of withstanding the molten material between the mating parts for reducing the formation of flash on the solidified sample, the gasket being sufficiently porous to allow vent-ing therethrough of gas from the cavity as the sample enters therein.

2. An immersion sampler according to claim 1, wherein the gasket is a felt of refractory fibres.

3. An immersion sampler according to claim 1 or 2, wherein the flow passage is shaped as a venturi passage.

4. An immersion sampler according to claim 1 or 2, comprising de-oxidizing material disposed in the flow passage.

5. An immersion sampler according to claim 1 or 2, comprising a closure of heat destructible material closing the entrance to the flow passage.

6. An immersion sampler according to claim 1, wherein the mold body is fitted into the end of a tube of heat resistant material.

7. An immersion sampler according to claim 6, wherein the tube is a cardboard tube.

8. An immersion sampler according to claim 1 or 2, wherein the flow passage is shaped as a venturi passage and comprising deoxidizing material disposed in the flow passage.

9. An immersion sampler according to claim 1 or 2, wherein the flow passage is shaped as a venturi passage and comprising a closure of heat destructible material closing the entrance to the flow passage.

10. An immersion sampler according to claim 1 or 2, wherein the flow passage is shaped as a venturi passage and comprising deoxidizing material disposed in the flow passage and a closure of heat destructible material closing the entrance to the flow passage.

11. An immersion sampler according to claim 2, wherein the mold body is fitted into the end of a tube of heat resistant material.

12. An immersion sampler according to claim 11, wherein the tube is a cardboard tube.