CN1169775A - A Sampling device for thermal analysis - Google Patents

Abstract

A sampling device for thermal analysis of solidifying metal, comprising at least one container intended to contain a sample quantity (30) of liquid metal during analysis, and at least one sensor (40, 220, 240) for thermal analysis, said sensor(s) being intended to be at least partly immersed in the solidifying metal sample quantity during analysis. The container comprises an inner wall (50), with an interior surface (60) intended to face the sample quantity during analysis, and an exterior surface (70); an outer wall (80), with an exterior surface (100) intended to face the ambient atmosphere, and an interior surface (90); said walls being joined at the mouth of the container whereby the exterior surface (70) of the inner wall (50) and the interior surface (90) of the outer wall (80) together define an essentially closed space (110).

Description

Sampling device for thermal analysis

The present invention relates to be used for the thermoanalytical sampler of metal solidification process, this device comprises: container, be used to put used liquid metal sample during the analysis; At least one is used for thermoanalytical sensor, and during analyzing, the sensor will be immersed in the test button that is solidifying.The invention still further relates to the sample receiver of above-mentioned sampler.Said apparatus and container are mainly used in the heat analysis of particularly carrying out in Cast Iron Production when producing compacted graphite iron castings (Compacted Graphit Iron) (hereinafter referred to as CGI iron).

Heat analysis is a kind of variation of passing through some melt substance of monitoring in the solidificating period temperature change, determines the microstructure of this material when solid-state, thereby determines the technology of its performance.The basic process of this technology is: from melt, take out sample, put it into test container, then utilize temperature-responsive means for example thermoelectricity occasionally pyrometer or known this class device recording of other those skilled in the art and working sample be in the solidificating period temperature over time.

When using hot analysis and Control molten material for example during the process of setting of cast iron, CGI iron or aluminium alloy, sixty-four dollar question be make test container and sample as far as possible piece ground near thermal equilibrium, and the controlled uniform and reproducible rate of heat dispation of assurance sample.The reason of making is in order can to measure the temperature variation during the phase transformation, for example to measure the mistake cold-peace crystallization latent heat that the stage generated of growing up in forming core stage and primary phase and time looks like this, and understanding these is very important to controlling some process of setting.

Document SE 350 606 has illustrated a kind of technology of setting up thermal equilibrium and reaching controlled rate of heat dispation, this technology contents comprises and sampling container being placed in the metal pool to be analyzed or with other heating container someway, so that at sampling container with wherein adorn between the sample, before beginning, thermoanalytical cooling procedure is issued to thermal equilibrium in the temperature higher than Tc.The container that is suitable for this kind technology is disclosed, and said vesse is made of graphite when being used to adorn melting aluminum, and uses ceramic material when being used to adorn melting iron.

Disclose another kind of hot analytical sampling container in DK-B-150 996, this container only is used for aluminium alloy.This container comprises a monkey of doing with steel plate, and the bottom of this crucible has the stopper of doing with heat insulator (for example core sand).

Except that said vesse, in this technology, also has other sampling receptacle of some similar types.A common drawback of these containers is, they make by following material or with following material as chief component, these materials are for example graphite, furans sand, core sand or fire cement; And well-known, these materials are difficult to processing.Their characteristic has caused existing job operation speed of production slow and have considerable quality problems.Though expectation provides various container characteristics, provide various different heat dissipation characteristics, so that produce the hot analytical sampling container that is suitable for different metal and alloy, but still impossible so far, seriously limited the scope of selecting in these characteristics because be used for producing the limited selection of the material of this container.Equally, the cooldown rate of sampling container should fully accurately and have repeatability, to satisfy thermoanalytical requirement, because the selection of available material behavior is very narrow, also is very difficult so a kind of like this container will be provided.

About the sampling container of immersion type, promptly when sampling, be immersed in the container in a large amount of deposite metals, also having an additional shortcoming is the danger that has thermal shock to break, particularly when container is used ceramic making.

Sampling container according to the art methods manufacturing also has the danger of polluting the deposite metal sample.

The purpose of this invention is to provide a kind of sampler, a kind of container that is used for this device particularly is provided, adopt this device can overcome above-mentioned shortcoming in type described in the foreword.

The sampler that utilization has the disclosed feature of claims 1 characteristic can reach this purpose.

The container class of sampler is similar to Dewar type container, and in certain embodiments, in fact it is exactly Dewar type container, promptly is the rarefied double sheet container in space between two layers of walls, and the temperature conductivity of this container is very low.But generally do not find time in the space between the inside and outside wall of container, but more or less fill with adiabatic medium, and the inflation body is relatively good, preferably fills air.

The inwall of container is preferably done quite thinly and/or with the material of low specific heat capacity, so that make total thermal capacity of inwall reach need low-level.In addition, total heat-conduction coefficient of inwall is preferably very high, to guarantee in very short time reaching thermal equilibrium at wall and being injected between the deposite metal sample in the sampling container of being got.Because the thermal capacity of inwall is low, so it is also low to pass to the required heat of wall from sample for the temperature that makes specimen temperature and wall equates, and because total heat transfer coefficient height, will be very short so transmit above-mentioned heat required time.

Can adopt to have above-mentioned thermal property, simultaneously in materialsing deposite metal on calorifics and chemically all stable material inwall.The thermoanalytical type that will carry out and the metal or alloy that will analyze are depended in the selection of certain material.Usually select a kind of metal or alloy for use.Preferably select cheap and easy material processed for use, particularly select steel for use.

Yet if there is no can there be the advantage that is formed by inwall in outer wall.The heat that is shed by inboard wall outer surface necessarily can not allow it directly enter in the contiguous atmosphere in the external world, because such rate of heat dispation that just is difficult to realize controlled uniform and reproduction.Therefore the purposes of outer wall be with inwall together, between Liang Bi, form the space that its total heat transfer coefficient is very low, the i.e. space that its rate of heat transfer is very low.

Can change the rate of heat dispation of sampler by the thickness of selecting suitable medium and be full of this space wholly or in part and/or change this space, can change to various forms of heat and analyze desired values.Above-mentioned medium can be any known, suitable adiabatic medium, for example sand, vermiculite, mica, magnesium oxide, chlorite, various pottery and their potpourri, but better with gas ratio.The most handy air can not use in a large number because air is not spent.

The most of heat that passes to outer wall from the sampling container inwall transmits by heat radiation.Therefore just can regulate rate of heat dispation from the inwall to the outer wall by design containers, the surface area of its outer wall of container of design is relatively greater than the surface area of its inwall; In this respect, perhaps the distance between the inside and outside wall is an important parameter.In addition, can also change the heat radiation situation by changing surface color and/or surface smoothness.

When adopting the heat radiation of two agar diffusion method control samples of adorning, the gap between two glasss plays a part crucial.When finding time this gap or when filling with transparent fluid such as air, heat radiation will become a kind of important thermal conduction mechanism.Along with the rising of dress specimen temperature, the heat radiation effect is more and more important, because its effect is directly proportional with the biquadratic of absolute temperature.

Radiant heat transfer also is subjected to the restriction that character of surface is so-called radiance.The ideal surfaced radiator is referred to as black matrix, and its radiance is 1.But real surface will be launched less energy, and its radiance is between 0～1.

Change surface treatment method or from the teeth outwards coating just can significantly change this surperficial overall heat transfer amount.The metal covering of polishing has very low radiance, the heat of radiation minimum.Other possible surface treatment comprise scrub, burn into sandblast and chemical treatment.

Coating surface mainly presents the radiation feature of coating.Used for this purpose high temperature coating comprises based on aluminium oxide, magnesium oxide, zirconia, silit, silicon nitride, carbon, boron nitride and quartzy sintered ceramic or plasma sprayed ceramic.Some industrial existing casting coatings based on boron nitride, zirconium dioxide and carbon are also arranged, and this method can form radiation controlled (contron) coating well.

By changing the size and/or the shape of sampling container, also can control rate of heat dispation, thereby satisfy some thermoanalytical requirement, another advantage of the present invention is embodied, and in other words is exactly that deep draw can easily make container of the present invention have specific dimensions and/or shape with this professional known similar approach by for example adopting.Container is preferably cup-shaped, and its geometric configuration is that part is sphere at least, and its bottom is a semisphere, to guarantee at all direction Homogeneouslly-radiatings.In addition, sample must be freely hang and need not an estrade supporting, the homogeneity that this estrade can the overslaugh heat radiation.

The inside surface of container inner wall preferably is coated with layer protective layer, and above-mentioned wall is fused when preventing that above-mentioned wall from running into the liquid metals sample.This protective finish also can be coated on the outside surface of outer wall, particularly the time wants to make container to be immersed under the situation in the red-hot liquid in sampling.Protective finish can be a for example aluminium oxide of refractory oxides.Though the sampler in the basic embodiment of the present invention includes only container and a Thermoanalytic sensor of above-mentioned double-walled shape, but generally comprise also that certain type sensor support, the purposes of this supporting member are that sensor is positioned on the position when analyzing certain part at least.Supporting member can be the top cover form, is used for covering during analyzing the opening of sampling container, is subjected to external interference to avoid sensor sample system.If avoid the surface contact ambient atmosphere of deposite metal sample, can load onto the device of carrying inert gas on the then above-mentioned top cover, this inert gas can also optionally be heated.

Thermoanalytical sensor generally is a thermopair, but the invention is not restricted to this.Any sensor that is suitable for heat analysis curing metal all can constitute parts of the present invention.

The heat analysis that sampler carries out when preferably being applicable to the open method production of US-A-4 667 725 (B ≌ ckerud) CGI iron.In this embodiment, device comprises two temperature-responsive means or sensor, and one of them is placed on the center of sample, and another position in molten material is near the inside surface of container inner wall.If applying protecting coat then preferably is coated with disclosed the sort of coating among the WO92/06809, promptly this coating comprises a kind of material in this embodiment, and this material can reduce the concentration near fusion element magnesium in the melt of chamber wall, reduces at least 0.003%.A kind of coating in above-mentioned back comprises for example oxide of silicon, manganese or the iron of at least 10% weight, or the oxide of the potassium of at least 0.5% weight and sodium.

In particularly preferred embodiment, design the device of when producing CGI iron, using and comprise: the protection tube of end seal, this pipe is immersed in the metal that is solidifying when analyzing; First thermocouple vacuum ga(u)ge, the hermetic terminal of this vacuum meter close aforementioned tube when analyzing, and can be inserted in this protection tube with taking out; Second thermocouple vacuum ga(u)ge, this vacuum meter also can be inserted in this protection tube with taking out.These two thermopairs separate enough distances, carry out heat interchange to subtract as far as possible during analyzing between this thermopair.The advantageous particularly part of this embodiment is that this thermopair can repeat to make and carry out side amount many times, rather than just consumes in an analysis operation.This container is preferably about vertical axis symmetry substantially, and the end seal pipe is coaxial with above-mentioned vertical axis, so just can reduce to occur when sample solidifies and cause stereomutation the problem of the thermopair of close inwall of side force impact.

Describe the present invention with reference to the accompanying drawings in detail, these accompanying drawings are:

Fig. 1 is the schematic, cross-sectional diagram by the sampler of the basic embodiment of the present invention;

Fig. 2 is its a part of sectional elevation of sampler that is used for the embodiment of CGI iron production by of the present invention;

Fig. 3 also is a sectional elevation, and a special preferred embodiment of the present invention is shown, and this embodiment also designs for the production of CGI iron, and the end seal protection tube of a thermopair is housed.

Sampler 10 shown in Fig. 1 comprises: the sampling container 20 of bowl-type, wherein be equipped with the motlten metal sample 30 that is solidifying; Be used for thermoanalytical temperature-responsive sensor 40.The vacuum meter 45 that is the sensor 40 of thermocouple assembly under the present embodiment situation is immersed in the sample 30.Container 20 is made of inwall 50 and outer wall 80, and two walls are made by sheet steel, have living space 110 between this two layers of walls, and this space is made of the outside surface 70 of inwall 50 and the inside surface 90 of outer wall 80.Weld seam 130 is used to be connected the inside and outside wall of container 20 peristomes.Weld seam 130 can be continuous weld seam or spotweld.Perhaps inside and outside wall can not weld, and uses the crimping combination, or replenishes the method joint of welding with crimping.In the embodiment shown, on the outside surface 100 of the inside surface 60 of inwall 50 and outer wall 80, coat 92/06809 described protective finish, when running into red-hot liquid metals, fuse to prevent sheet steel by Wo.Sensor 40 is connected in hot assay determination device (not shown) by cable 120, and measuring-signal is transported to the above-mentioned determinator that is used to analyze from measure portion 45 by this cable.

Sampler 200 parts of using when producing CGI iron are shown among Fig. 2, and the container that this device comprises is the same a kind of container in the device shown in Figure 1.Yet install 200 two sensors are housed, these two sensors dispose according to the explanation of above-mentioned US-A-4 667 725 basically: the vacuum meter 210 of the first temperature-responsive sensor 220 is placed on the center of sample 30, and the vacuum meter 230 of second sensor 240 then is placed on the position near the inside surface 60 of inwall 50.Sensor support 250 is used for making sensor 220,240 in place when analyzing.Sensor support 250 is connected in container by shank 255.When submergence, liquid metal is from flowing in the container between the above-mentioned shank.

Fig. 3 illustrates the part by the sampler 300 of advantageous particularly embodiment of the present invention.The same with device shown in Figure 2, device 300 also designs for using when producing CGI iron, this device need not two independent sensor and is only used a sensor element 310, this sensor element still comprises two thermocouple vacuum ga(u)ges 320,330, and these two vacuum meters dispose according to the explanation of US-A-4 667 725 basically.Sensor element 310 is inserted in the protection tube of being done by steel, pottery, glass or other any suitable material 340 removedly.Support unit 350 is used for carrying out making protection tube 340 fix in position when heat is analyzed.Similar with above-mentioned situation, support unit 350 is connected in container 20 by shank 355.

Be understood that, to above-mentioned sampler carry out appropriate change be in the professional knowledge scope of those skilled in the art and the scope of the invention in, and said apparatus only is not limited to when producing CGI iron or use during the cast iron of other form, also can use when producing other various metal.

Claims (9)

1. A sampling device for thermal analysis of metal solidification process, comprising: at least one container (20), which is used to contain the liquid metal sample taken during analysis; at least one sensor (40, 220, 240), the above-mentioned sensor is intended to be at least partially immersed in the solidified metal sample taken during the analysis; it is characterized in that the container comprises: an inner wall (50) having an inner surface (60) and an outer surface (70 ), the inner surface faces the sample during analysis; the outer wall (80), which has an inner surface (90) and an outer surface (100), which is in contact with the outside atmosphere; , thus the outer surface (70) of the inner wall (50) and the inner surface (90) of the outer wall (80) jointly form a substantially closed space (110). 2. A sampling device according to claim 1, characterized in that the device further comprises a sensor support (250, 350) which holds the sensor (40, 220, 240) in place during analysis. 3. Sampling device according to claim 1 or 2, characterized in that the closed space (110) contains a thermally insulating medium. 4. A sampling device as claimed in claim 3, characterized in that the thermally insulating medium is a gas or a gas mixture. 5. A container for a sampling device (10) for thermal analysis of solidifying metal, the container is used to contain a sample (30) of solidifying metal during analysis, characterized in that the container comprises: an inner wall (50) , the inner wall has an outer surface (70) and an inner surface (60), the inner surface faces the sample during analysis; an outer wall (80), the outer wall has an inner surface (90) and an outer surface (100), the outer The surfaces are exposed to the outside atmosphere; the walls are joined at the opening of the container so that the outer surface (70) of the inner wall (50) and the inner surface (90) of the outer wall (80) together form a closed space (14). 6. The container of claim 5, wherein a portion of the container is hemispherical. 7. A container as claimed in claim 5, characterized in that the inner and/or other surfaces are treated by scrubbing, etching, sandblasting or chemical treatment. 8. The container as claimed in claim 5, characterized in that, by sintering and adding alumina ceramics, magnesium oxide ceramics, zirconia ceramics, silicon carbide ceramics, silicon nitride ceramics, carbon ceramics, boron nitride ceramics or quartz ceramics methods for treating interior surfaces and/or other surfaces. 9. The container according to claim 5, characterized in that, the plasma sprayed alumina ceramics, magnesia ceramics, zirconia ceramics, silicon carbide ceramics, silicon nitride ceramics, carbon ceramics, boron nitride ceramics or quartz ceramics Methods treat interior surfaces and/or other surfaces.

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