CN1014931B - Method of measuring solidification of molten steel and equipment for measuring solidification of steel ingots - Google Patents

Abstract

The present invention relates to a method for actually measuring the solidification of molten steel, particularly to a method for actually measuring the solidification of steel ingots and continuous casting blanks and a device for actually measuring the solidification of the steel ingots. When the steel ingots or the continuous casting blanks are cast, trace elements (or alloy) of which the melting points are lower than those of iron are added in a liquid core part of the steel ingots (or the continuous casting blanks) by the device (or a measuring bin), wherein the trace elements can easily generate sulfide in the molten steel; measured steel ingots or continuous casting blanks of complete solidification are dissected so as to carry out sulphur print, the solidification thickness, the solidification speed, the solidification rate and the solidification structure of the steel ingots or the continuous casting blanks are measured according to a sulphur print diagram. The device for actually measuring the solidification of steel ingots is composed of a top-pressing mechanism and an embedded section connected with the top-pressing mechanism.

Description

Method of measuring solidification of molten steel and equipment for measuring solidification of steel ingots

The invention belongs to a kind of method of surveying solidification of molten steel, particularly survey the method that steel ingot (rimming steel, semikilled steel and killed ingot) and continuous casting billet solidify and the device of actual measurement ingot solidification, be applicable to that the biography of steel ingot, continuous casting billet cast and steel ingot is put, in the heating, rolling production and scientific research.

Find to survey the method for bind steel ingot (rimming steel, semikilled steel and weight are greater than six tons of killed ingots that bind) concreting thickness, solidification rate, setting rate and consolidated structure so far as yet.

At present actual measurement continuous casting billet concreting thickness is after squeezing into continuous casting billet with aluminium sheet rivet or chromium steel rivet, according to aluminium sheet rivet or chromium steel rivet fusing situation carry out low power, X light analysis is calculated.This rivet method still has following weak point: 1, the thickness of the solidified steel squeezed into of rivet is limited, and this method is unsuitable for measuring the bigger steel ingot of concreting thickness; 2, the precision of measurement solidification of molten steel thickness is not high.After the chromium steel rivet of rivet method or aluminium sheet rivet are squeezed into continuous casting billet, to and spread two time courses through fusing and just can be diffused into liquid/solid phase interface, these two time courses will be longer than direct by the single time course of Liquid Phase Diffusion to liquid phase, so measuring accuracy is lower.Particularly aluminium, chromium steel rivet contain the concentration height of aluminium or chromium, and aluminium, chromium can reduce the solidifying point of the liquid phase part of steel more significantly, have therefore reduced the precision of surveying concreting thickness, setting rate; 3, when steel ingot or continuous casting billet are used the rivet method, the splash molten steel outward easily in steel ingot, continuous casting billet solidification layer rivet porch.Particularly in rimmed ingot, semi-killed ingot, gas is arranged, can form under the situation of pressure,, make operation site produce unsafe factor if having rivet to squeeze into then can take place to spray molten steel outward in the rivet porch.Simultaneously because ejection molten steel and gas, destroyed the physical condition of ingot solidification, influence the precision of measuring concreting thickness, speed, structure, also be difficult to again continuously accurately, measured truly different concreting thickness, speed, the structures in (moment in ingot mould and outside the ingot mould) constantly; 4, with low power and X-ray piecemeal analysis steel ingot, the chromium of continuous casting billet part, the content and the distribution of aluminium only, so complicated operation, heavy, especially bigger to large-scale steel ingot checked operation difficulty.

The present invention is directed to the problem of above-mentioned existence, the method of actual measurement solidification of molten steel has been proposed, particularly survey (micro-sufur printing spike) method and device thereof that steel ingot, continuous casting billet solidify, purpose is the high-precision molten steel of surveying continuously, particularly survey different concreting thickness, solidification rate, setting rate and the consolidated structures constantly of steel ingot with continuous casting billet, and it is easy and simple to handle, safe and reliable.

Method of the present invention and device thereof.

Fig. 1 is (micro-sufur printing spike) device of actual measurement ingot solidification.

Fig. 2 is four horizontal section sufur printings of the F * 7.2 ton rimmed ingot figure that adds micro-sulphur, nickel, chromium.

Method of the present invention is namely surveyed solidification of molten steel, particularly surveys (micro-sufur printing spike) method that steel ingot and continuous casting billet solidify. The method is in the steel ingot that do not bind (band heat-insulating shield killed ingot), continuous casting billet, adopt adding do not bind steel ingot, continuous casting billet of radio isotope or metal spike solidifies, and utilize sufur printing to measure on the quality inspection basis of steel ingot, the segregation of steel billet sulphur, sulfide distribution, be further development of the new method of utilizing micro-sufur printing spike steel ingot, continuous casting billet to solidify. This method is included in and adds metal or radio isotope in tested do not bind steel ingot and the continuous casting billet, and mensuration steel ingot, the segregation of the sulfide of steel billet self inside and the sulphur print of distribution, when being characterized in pouring into a mould steel ingot or continuous casting billet, utilize device of the present invention (or material cup), fusing point is low and generate easily trace element (or its alloy of sulfide in molten steel than iron, or radio isotope) joins in the liquid core segment of steel ingot or continuous casting billet, dissect then tested steel ingot or the continuous casting billet solidify fully and do sufur printing, measure and calculate the concreting thickness/setting rate of steel ingot or continuous casting billet/solidification rate and consolidated structure according to sufur printing figure. Before the cast steel ingot, fusing point is low and easily generate the trace element (or its alloy, or radio isotope) of sulfide in molten steel than iron, and the bottom cavity (5) that is positioned over apparatus of the present invention (also claiming " pre-embedding pressing device ") is inner; Then, according to the needs of measuring with 1 in this device or several ingot mould first half that is placed in tested steel ingot, make device inner bottom part cavity (5) place the liquid core position of steel ingot, in ingot mould, pour into a mould steel ingot, when ingot steel casting is complete bind after, this moment, bottom cavity (5) inner trace element melted; According to the needs of measuring; in ingot mould; outside the ingot mould; in the soaking pit; the several different moment that soaking pit is outer; utilize external force (such as the hand hammer hammer force; or the pressure on top surface of ingot stripper push rod; or the pressure on top surface of steel ingot furnace charging conveyer); 1 of roof pressure or several (when METHOD FOR CONTINUOUS DETERMINATION in ingot mould; outside the ingot mould; in the soaking pit; during the solidifying of the outer several different constantly steel ingots of soaking pit) upper end of the upper ejector pin (8) of pre-embedding pressing device; make the inner trace element that has melted of bottom cavity (5) in difference constantly roof pressure in the liquid core segment of tested steel ingot; said trace element refers to chromium/nickel/sulphur/aluminium or its alloy; or radio isotope; their fusing point is low and easily generate sulfide in molten steel than iron, and its micro-addition is generally the 0.0015%-0.0005% of tested steel ingot weight. In steel ingot liquid core, the sinking effect that termination (13) (also claiming the head that comes off) is come off by means of the roof pressure of lower push rod (14), and the convection action of liquid core molten steel make trace element promptly be diffused into the liquid of steel ingot/solid phase interface place, and with molten steel in vulcanize and close, generate the chromic sulfide sulfides; There is the sulfide concentration of obvious addition element poor Gu be engraved in steel ingot liquid/two-phase section when then this measures, this is because be engraved in the liquid phase region of steel ingot when measuring, because sulfuration symphysis sulphidisation in the trace element that adds and the molten steel, steel ingot liquid phase region sulfide concentration increases so measure constantly; Measuring constantly, because the trace element that adds diffusion is less than in the solid phase area, so the concentration of sulfide is low in the tested moment steel ingot solid phase area. After treating that tested steel ingot solidifies fully, this steel ingot is carried out vertical profile along its center line, do sufur printing in the vertical section, to carry out several cross sections cross-sectional at the tested position of half steel ingot behind vertical profile again then, then do sufur printing in each cross section of steel ingot, following chemical reaction namely take place:

AgS is deposited in and presents brown impression (Fig. 2) on the sufur printing printing paper, demonstrates liquid/solid phase zone of measuring steel ingot constantly according to dark (occur in and measure the liquid phase region of steel ingot constantly) of brown impression on the sufur printing printing paper, shallow (occur in and measure solid phase area constantly).The thickness that shows on the actual measurement sufur printing printing paper is the concreting thickness on this section of measuring moment steel ingot.With different concreting thickness difference h constantly on the steel ingot section that records _i-h ₁(h wherein _i, h ₁Be respectively the ingot solidification thickness of measuring first and measuring the moment for the i time) and its twice measuring interval time (t _i-t ₁) ratio ((h _i-h ₁)/(t _i-t ₁)) be this steel ingot at the section that records in t _i-t ₁Setting rate in interval time (v).This ingot solidifies constant K, uses general formula D=K $\sqrt{t}$ Calculate, D is concreting thickness h in the formula _i-h ₁(millimeter), t are time t _i-t ₁(branch).To record the area (s in the illustrated differing heights liquid phase of steel ingot each transverse section sufur printing constantly zone again ₁, s ₂... s _i) longitudinal pitch (H of (this area be with the area of differing heights transversal section liquid phase region shown in planimeter or each section sufur printing printing paper of on network of coordinates, describing and measure out) and adjacent transverse section thereof ₀, H ₁, H ₂... H _i) data difference substitution calculating steel ingot cubature formula V commonly used _i=(Hi)/3 (S _I-1+ S _i+ $\sqrt{S{}_{\mathrm{i-1}}\mathrm{\times S}{}_i}$ ) calculate its each several part liquid phase summation again

V _Liquid=v ₀+ v ₁+ v ₂+ ... v _i, be steel ingot and measure liquid phase volume constantly.Again steel ingot cumulative volume (V) is deducted the difference (V-V that measures liquid phase volume (V liquid) constantly _Liquid) with the ratio ((V-V liquid)/(V)) of its steel ingot volume, promptly draw steel ingot and measuring solidification rate (%) constantly.Utilize shape and the distributed areas of measuring liquid/liquid/solid interface constantly shown in the steel ingot section sufur printing figure, the design feature that can determine its freezing interface is wavy honeycomb blister band or level and smooth Quench band, or ingot core band, and the time course of their formation.

Measure continuous casting billet or hang the method that heat-insulating shield (not binding) killed ingot solidifies, before the cast can with fusing point than iron low and in molten steel, give birth to easily trace element at sulfide (as chromium, nickel, sulphur, aluminium or its alloy, or radioactive isotope) puts into the ceramic material cup of soy sauce bucket type, its addition is the 0.0015%-0.0005% of tested continuous casting billet weight, perhaps be placed on the interior (steel ingot that its material cup is measured the length ratio of steel material cup of soy sauce bucket type, the long 300-400mm of the degree of depth at steel billet position), if during with ceramic material cup, this material cup can be placed on the continuous casting mold molten steel surface, or be placed on the steel ingot that do not bind and coagulate on the molten steel surface, a glass interior trace element is melted in advance; Measuring constantly, this is equipped with the pottery or the steel material cup of trace element, do not coagulate the top of the part or the steel ingot that do not bind from the continuous casting billet top and do not coagulate part, the liquid core segment that inserts the tested position of continuous casting billet or band heat-insulating shield (not binding) steel ingot stirs up and down, closes trace element and is diffused into the liquid-solid interface place rapidly; The continuous casting billet after dissection is solidified fully or the tested position of steel ingot, and do sufur printing, according to the depth of brown impression on the sufur printing printing paper, demonstrate liquid/solid phase area of measuring continuous casting billet constantly or band heat-insulating shield killed ingot.Can survey thus and the concreting thickness that calculates continuous casting billet or band heat-insulating shield killed ingot, setting rate, solidification rate, consolidated structure (computing method are identical with the computing method of surveying steel ingot).

Device of the present invention, promptly pre-buried roof pressure determinator.

Pre-buried roof pressure determinator similar one " syringe " is installed in the first half of ingot mould; it is by upper ejector pin (8); middle push rod (11) and lower push rod (14); removable jew support (2); roof pressure sleeve pipe (1), self-locking spring sheet (7), protective casing members such as (4) is formed; be characterized in by a top-pressure mechanism, and pre-buried section of being connected with top-pressure mechanism form.

Top-pressure mechanism is by roof pressure sleeve pipe (1) and isometric with roof pressure sleeve pipe (1), and the upper ejector pin (8) that can in roof pressure sleeve pipe (1), slide, and removable jew support (2) and adapter sleeve members such as (9) composition, before the cast, removable jew support (2) is gone up the middle part by bolted at ingot mould (3), and connect by adapter sleeve (9) screw-type that is connected with roof pressure sleeve pipe (1) lower end, make it to support top-pressure mechanism, indention groove (16) and rectangle groove (17) are arranged on the face of cylinder, lower end of upper ejector pin (8), on the outer wall of roof pressure sleeve pipe (1), the safe self-locking spring leaf (7) of a pair of symmetry is installed, and its nose stretches in the serrate groove (16) that roof pressure sleeve pipe (1) is stuck in upper ejector pin (8); Pre-buried section is by protective casing (4); and middle push rod (11) that can slide and lower push rod (14) composition in protective casing (4) lining; protective casing (4) upper end open; and be connected the lower end of top-pressure mechanism by the filler ring (10) that is connected with adapter sleeve (9); protective casing lower end back cover is the termination (13) (also being called the head that comes off) of cup head shape; at protective casing (4) inner bottom part; the core that is termination (13) has one can hold micro-cylindrical cavity (5); on the pipe outside wall surface of the protective casing (4) of a little higher than cavity (5) upper surface a ring-shaped groove (12) is arranged, its ditch depth is 1/3 of a protective casing wall thickness.

Middle push rod (11); lower push rod (14) is to be made by graphite matter or ceramic material; protective casing (4) is to be made by ceramic material; the adiabatic backing plate (15) that has one deck to be made by general thermal insulation material between middle push rod (11) and lower push rod (14) is transmitted in the top-pressure mechanism in order to the heat that reduces from pre-buried section.

Pre-buried jack unit is like this work: when tested ingot steel casting is intact when binding, the pre-buried segment protect sleeve pipe (4) of this device is embedded under molten steel face (20) solidification layer.Measuring constantly; the upper ejector pin (8) of this device is imposed hammer force or ingot stripper push rod (6) downwards during top power (p); upper ejector pin (8); middle push rod (11) and lower push rod (14) all move down into desired position (19) from push rod initial position (18); and the nose of the safe self-locking spring leaf (7) on the roof pressure sleeve pipe (1); by the groove of the serrate bottom slippage of upper ejector pin (8) in the serrate groove (16) or rectangle groove (17) of corresponding height; upper ejector pin (8) is blocked securely; fixing, prevent that molten steel from upwards passing along the inner chamber of protective casing (4).The middle push rod (11) that moves down, lower push rod (14) will be embedded in the semicircle termination (13) (head also is referred to as to come off) of protective casing (4) lower end of steel ingot core and locate the top disconnection along protective casing (4) outside wall surface ring-shaped groove (12).Termination (13) simultaneously by roof pressure to steel ingot liquid/solid phase interface or sink on liquid-solid interface; the liquid trace element (being in annotating the ingot process, the molten steel heat fused around protected pipe (4) outside) that is fused into of its termination (13) inner chamber (5) dress also is diffused into liquid/solid phase interface thereupon immediately.After steel ingot solidifies fully.Dissect steel ingot and be sufur printing figure, measure and calculate steel ingot according to sufur printing figure and measuring concreting thickness, setting rate, solidification rate and consolidated structure constantly.

Embodiments of the invention

Survey solidification rate and consolidated structure after 7.2 tons of rimmed ingots bind.In advance with 2 pre-buried jack units of the present invention; be installed in the ingot mould first half of tested steel ingot simultaneously; for being convenient in demoulding; before behind notes, shunting; folding support is unloaded ingot mould; (install other parts; with pre-buried section of device solidifying and be fixed on the steel ingot top by steel ingot top solidification layer) respectively in the mould that binds after the cast 42 minutes; after the demoulding 8 minutes; utilize the ingot stripper push rod upper ejector pin (8) of twice roof pressure determinator respectively; make the micro-sulphur in cavity (5) lining; nickel; chromium difference roof pressure is in the liquid core segment of steel ingot; roof pressure for the first time wherein; the sulphur that adds cavity (5) lining is 335 grams; nickel is 40 grams, and the trace element of roof pressure adding for the second time is chromium 40 grams.After steel ingot solidifies fully this steel ingot is pushed up the cross-sectional sufur printing figure that is in 14%, 23%, 32%, 39% place apart from ingot, the A's of Fig. 2), B's), C(32%), D(39%), 1 spike of sufur printing curve goes out the liquid/solid phase boundary line of 42 minutes steel ingots in the mould of cast back among Fig. 2, and 2 spikes of sufur printing figure curve go out the liquid/solid phase boundary line of steel ingot in back 50 minutes of cast (in comprising mould behind 42 minutes, the demoulding 8 minutes time) among Fig. 2.

Push up shown in middle curve 1 of 23% place transverse section sufur printing figure (B) and the curve 2 apart from ingot according to steel ingot, can record this ingot (23%) and locate transversal section 42 fens (t in mould ₁) time curve 1(liquid/solid phase boundary line) and pour into a mould back 50 minutes (t ₂) time curve 2(liquid/solid phase boundary line) respectively apart from the distance of surface of steel ingot, promptly concreting thickness is respectively (h ₁) and (h ₂), then can try to achieve steel ingot and push up the interval time (t of transversal section, 23% place after the demoulding apart from ingot ₂-t ₁) interior setting rate is (h ₂-h ₁)/(t ₂-t ₁)=(202-175)/(50-42)=7.375 millimeter/minute.Solidify constant K= $\frac{\mathrm{<figure-callout\; id="1"\; label="D\; t"\; filenames="88108162\_DRIMG1.png"\; state="\{\{state\}\}">D</figure-callout>}}{t^{}}$ =9.55 millimeters/

${}^{\frac{1}{2}}$

Try to achieve among Fig. 2 steel ingot shown in sufur printing figure A, B, C, the D in the liquid phase region area of back 50 minutes of cast (mould in 42 minutes, mould 8 minutes) outward with planimeter or network of coordinates picture, be s in the transversal section of differing heights ₁=94373.23mm ², s ₂=89567.28mm ², s ₃=51463.379mm ², s ₄=266422.5mm ²Steel ingot centerline section sufur printing longitudinally figure can record position and its spacing of annotating the back 50 minutes vertical liquid phase region highs and lows of steel ingot, and the adjacent transversal section of the vertical differing heights of steel ingot spacing:

H ₀=124mm(steel ingot is vertically annotated back 50 minutes transversal section, liquid phase region peak place to the spacing of pushing up transverse section, 14% place apart from ingot).

H ₁=201.6mm(steel ingot pushes up the spacing of transverse section, place, 14% place to 23% apart from ingot).

H ₂=201.6mm(steel ingot is apart from the spacing of transverse section, 23% and 32% place, ingot top).

H ₃=156.8mm(steel ingot pushes up the spacing of transverse section, place, 32% place to 39% apart from ingot).

H ₄=56mm(steel ingot pushes up the spacing of transverse section, 39% place to transverse section, the vertical liquid phase region minimum point place of steel ingot apart from ingot).

The cubature formula that the data substitution of above-mentioned actual measurement is commonly used:

$V_i\frac{\mathrm{Hi}}{3}{\mathrm{(S}}_{\mathrm{i-1}}\mathrm{+S}{}_i+\sqrt{S{}_{\mathrm{i-1}}\mathrm{\times S}{}_i})$

And ask steel ingot liquid phase each several part volume and

V _Liquid=V ₀+ V ₁+ V ₂+ V ₃+ V ₄=5027473.26mm ³=0.005028m ³

Then steel ingot is at the solidification rate of cast in the time of back 50 minutes:

(V-V _LiquidV is the cumulative volume of actual measurement steel ingot in)/(V)=(1.0135-0.05028)/1.0135=95.03%(formula)

Shape and position according to the liquid/solid phase interface shown in the curve among Fig. 22, bind back in mould 42 minutes of steel ingot as can be known, the transversal section, top of the freezing interface of mould in the time of outer 8 minutes is direct-connected rectangle, the transversal section, bottom of freezing interface is radish shape transversal section, its liquid phase region has the almost spherical bubble of some, the steel ingot liquid phase region is positioned at apart from 8.5%-45.9% place, steel ingot top, the consolidated structure characteristics of Here it is 7.2 tons of steel ingot ingot heart bands.

Claims (5)

1, a kind of method of surveying ingot solidification is characterized in that pouring into a mould before the steel ingot, the lower and trace element that in molten steel, be easy to generate sulfide with fusing point (or its alloy, or radioactive isotope) be placed on and give bottom cavity (5) lining of burying jack unit; According to the needs of measuring this is given 1 or the several ingot mould first half that is placed in tested steel ingot that buries jack unit then, make this device inner bottom part cavity (5) place the liquid core position of steel ingot, pour into a mould steel ingot in ingot mould, after steel ingot bound, bottom cavity (5) lining trace element melted; According to the needs of measuring, in ingot mould, outside the ingot mould, in the soaking pit, the several different moment that soaking pit is outer, utilize the upper end of the upper ejector pin (8) of one or several pre-buried jack unit of external force roof pressure, the trace element that has melted that makes bottom cavity (5) lining in difference constantly roof pressure in the liquid core segment of tested steel ingot, make the sinking effect that comes off of termination (13) by means of the roof pressure of lower push rod (14), and the convection action of liquid core molten steel, make trace element promptly be diffused into the liquid/solid phase interface place of steel ingot, and with molten steel in vulcanize and close; After treating that tested steel ingot solidifies fully, this steel ingot is carried out vertical profile along its center line, on the longitudinal profile, do sufur printing, to carry out several transversal section cross-sectional at the tested position of half steel ingot behind vertical profile again then, then on each transverse section of steel ingot, do sufur printing, demonstrate the liquid/solid phase area of the steel ingot of measuring the moment according to the depth of brown impression on the sufur printing printing paper.

2, a kind ofly survey continuous casting billet or hang the method that the killed ingot of heat-insulating shield solidifies, before it is characterized in that pouring into a mould continuous casting billet or hanging the heat-insulating shield killed ingot, with fusing point than iron low and trace element that in molten steel, be easy to generate sulfide (or its alloy, or radioactive isotope) puts into the pottery or the steel material cup of soy sauce bucket type, if during with ceramic material cup, this material cup can be placed on continuous casting mold molten steel surface, or be placed on the steel ingot that do not bind and coagulate on the molten steel surface, a glass interior trace element is melted in advance; Measuring constantly, this is equipped with the pottery or the steel material cup of trace element, do not coagulate the top of the part or the steel ingot that do not bind from the continuous casting billet top and do not coagulate part, the liquid core segment that inserts the tested position of continuous casting billet or band heat-insulating shield steel ingot stirs up and down, makes trace element be diffused into liquid/solid phase interface place rapidly; The continuous casting billet after dissection is solidified fully or the tested position of steel ingot, and do sufur printing, according to the depth of brown impression on the sufur printing printing paper, demonstrate liquid/solid phase area of measuring continuous casting billet constantly or band heat-insulating shield killed ingot.

3, as claim 1,2 described methods is characterized in that described trace element is meant chromium, nickel, sulphur, aluminium or its alloy, or radioactive isotope, and its element addition is 0.0015%～0.0005% of tested steel ingot or a continuous casting billet weight.

4, a kind of device of surveying ingot solidification, it is characterized in that it by top-pressure mechanism and pre-buried section of being connected with top-pressure mechanism form: top-pressure mechanism is by the roof pressure sleeve pipe (1) and the upper ejector pin (8) that can slide in roof pressure sleeve pipe (1), and removable jew support (2) and adapter sleeve members such as (9) composition, removable jew support (2) is before cast, go up the middle part by bolted at ingot mould (3), and connect by adapter sleeve (9) screw-type that links to each other with roof pressure sleeve pipe (1) lower end, make it to support top-pressure mechanism, indention groove (16) and rectangle groove (17) are arranged on garden, the lower end cylinder of upper ejector pin (8), on the outer wall of roof pressure sleeve pipe (1), the safe self-locking spring leaf (7) of a pair of symmetry is installed, and its nose stretches in the serrate groove (16) that roof pressure sleeve pipe (1) is stuck in upper ejector pin (8); Form by protective casing (4) and the middle push rod (11) and the lower push rod (14) that can slide for pre-buried section in protective casing (4) lining; protective casing (4) upper end open; and be connected the lower end of top-pressure mechanism by the filler ring (10) that links to each other with adapter sleeve (9); protective casing lower end back cover is half knob shape termination (13); in protective casing (4), have one can adorn micro-cavity (5); on the pipe outside wall surface of the protective casing (4) of a little higher than cavity (5) upper surface, a ring-shaped groove (12) is arranged; the adiabatic backing plate (15) of one deck is arranged between middle push rod (11) and lower push rod (14), be transmitted in the top-pressure mechanism in order to the heat that reduces from pre-buried section.

5, device as claimed in claim 4 is characterized in that protective casing (4) is to be made by ceramic material, and push rod (11) and lower push rod (14) are made by graphite matter or ceramic material in the middle of it.

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