CN104236977A - Method for judging crystallization ratio of solid slag film of protection slag of continuous casting crystallizer - Google Patents
Method for judging crystallization ratio of solid slag film of protection slag of continuous casting crystallizer Download PDFInfo
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- CN104236977A CN104236977A CN201410519934.6A CN201410519934A CN104236977A CN 104236977 A CN104236977 A CN 104236977A CN 201410519934 A CN201410519934 A CN 201410519934A CN 104236977 A CN104236977 A CN 104236977A
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Abstract
The invention discloses a method for judging the crystallization ratio of a solid slag film of protection slag of a continuous casting crystallizer. The method comprises the following steps: heating the protection slag of the continuous casting crystallizer in a graphite crucible until the protection slag is completely molten, and forming a uniform molten pool; obtaining the solid slag film of the protection slag by an HF-200 slag film heat flow simulator; quickly performing water quenching on molten slag in the graphite crucible to obtain a corresponding water quenched slag sample; performing thermal analytic test on the solid slag film and the water quenched slag according to a same heating program respectively, recording a DSC (differential scanning calorimetry) curve of the sample in the heating process by a differential scanning calorimeter, and analyzing the slag film and the DSC curve of the water quenched slag to obtain the crystallization ratio of the solid slag film. According to the method provided by the invention, results can be used for representing the heat-transfer characteristics of the solid slag film of the protection slag; the method has a guiding significance on design of the protection slag of the continuous casting crystallizer.
Description
Technical field
The present invention relates to a kind of decision method of the physical property to continuous crystallizer protecting slag Solidified Flux Film, especially by crystal proportion quantitative method in covering slag Solidified Flux Film.
Background technology
Crystallizer protecting residue is the important metallurgical function material used in casting process, plays a part very crucial to the direct motion and good slab quality that ensure cast.The heat that joining the granulated slag dependence molten steel on crystallizer molten steel surface provides is gradually heated by the sonochemical activity, and finally on molten steel face, forms liquid slag layer.Melt cinder flow into after between base shell and crystallizer, near strand side temperature higher formation melt cinder film, the closer to crystallizer, temperature is lower, and along with the reduction of temperature, melt cinder solidifies formation Solidified Flux Film, in close crystallizer side, melt cinder cools fast and forms glassy layer (as Fig. 1).Therefore, the Solidified Flux Film between base shell and crystallizer is in fact containing crystal and glass two-phase (as Fig. 2).On the one hand, the crystal in Solidified Flux Film can effectively hinder heat from base shell to the lateral transport of crystallizer, and this contributes to the Slow cooling realizing base shell, thus is conducive to the generation avoiding surface longitudinal crack of slab; On the other hand, increase crystal proportion in Solidified Flux Film, will be reduced by the heat flow density of slag film, the thickness of initial solidification shell is also thereupon thinning, and too thin base shell is difficult to the situation that bleed-out just likely appears in the friction force of bearing between itself and crystallizer wall.Therefore, only have crystal proportion in Solidified Flux Film, namely crystallization ratio controls in rational scope, just can coordinate the contradiction between lubrication and heat transfer in casting process, and final realization pours into a mould direct motion and the slab quality obtained.
Solidified Flux Film crystallization ratio can be used for characterizing slag film heat transfer characteristic, is the physical parameter that researchist very pays close attention to when design protection slag.But for how by crystal proportion quantification in covering slag Solidified Flux Film, existing research method still deposits deficiency both ways.First is the Solidified Flux Film not obtaining being suitable for judging slag membrane crystallization ratio.The experimental results shows, the impact that the cooling condition of melt cinder is larger than having on the crystallization of Solidified Flux Film, and the Solidified Flux Film that is obtained under Different Cooling Conditions, the result of crystallization ratio is not identical.At present; the Solidified Flux Film that covering slag is formed in continuous cast mold directly can obtain in industry spot; but due to field condition unfixing (as pulling rate, liquid steel temperature, sample position and time etc.), make the slag membrane sample obtained there is no representativeness and reappearance.Second is the Solidified Flux Film to getting, and the method for mostly directly being observed by macroscopic view or microcosmic at present qualitatively judges slag membrane crystallization ratio.Even if the pattern of crystal in slag film can be observed under optical microscope or scanning electron microscope, but because the region observed is limited, and the boundary line of crystal and glass is difficult to determine, therefore directly observation slag membrane structure is difficult to obtain slag membrane crystallization more accurately and compares result.X-ray diffraction technology also can be used for studying the crystal in slag film, but needs carry out a large amount of corrections to diffraction data and just can obtain result after complex calculations, and the result difference selecting different parameters to carry out calculating is larger.
Therefore; want the ratio obtained more accurately in Solidified Flux Film shared by crystal; need to obtain suitable Solidified Flux Film; the slag film acquisition methods that this patent adopts utilizes HF-200 slag film heat flux simulation instrument (as Fig. 1) to obtain slag film in laboratory; the copper probe passing into chilled water is immersed in slag and makes liquid covering slag cooled and solidified; melt cinder is attached in copper probe head wall after forming Solidified Flux Film; after a period of time, probe is promoted to original height, and the Solidified Flux Film (as Fig. 2) be attached in probe head wall can be used as the slag membrane sample of crystallization than test.Owing to there being noncrystal existence in Solidified Flux Film, therefore slag film can release heat in heating process, and non-crystal quality is proportional in liberated heat and slag film, replace in slag film with slag water quenching slag noncrystal, differential scanning calorimetry is utilized to measure liberated heat in slag film and Water Quenching Slag (noncrystal) heating process respectively, the thermal discharge of the thermal discharge in slag film heating process and unit mass Water Quenching Slag heating process is compared, just can obtain the quantitative crystallization of slag film and compare result.
Summary of the invention
The object of the invention is for above-mentioned the deficiencies in the prior art; propose a kind of decision method of covering slag Solidified Flux Film crystallization ratio; in the forming process of laboratory simulation industry spot slag film; obtain under given conditions and be suitable for crystallization than the Solidified Flux Film judged, and to obtaining the concrete grammar judging Solidified Flux Film crystallization ratio after being detected the physical property of slag film.
In order to solve the problems of the technologies described above, the technical solution used in the present invention is a kind of decision method of continuous crystallizer protecting slag Solidified Flux Film crystallization ratio, it is characterized in that comprising with the heat enthalpy value in differential scanning calorimeter detection slag and Water Quenching Slag temperature-rise period and to Analysis of test results process;
Detect slag film physical property with differential scanning calorimeter to comprise the steps:
1) take slag film powdered sample 10mg to 15mg with electronic balance, be positioned in corundum crucible;
2) utilize differential scanning calorimeter, the crucible of sample will be housed from room temperature to 900-1300 DEG C with the heating rate of 10-20 DEG C/min, obtain the DSC curve of sample in heating process, horizontal ordinate is temperature T, and unit is DEG C; Ordinate is rate of heat flow, and unit is mw.mg
-1; Whole process passes into blanket gas, and flow is 50mL/min;
3), after test terminates, the thermal analysis software supporting with thermal analyzer is utilized test result to be exported in text document the calculating being used for crystallization ratio;
4) use the same method and obtain the thermal analyses testing result of Water Quenching Slag powdered sample.
Analysis of test results process is comprised the steps:
1) make DSC curve (convex is exothermic peak) according to the detection data of the Solidified Flux Film imported in text document, horizontal ordinate is temperature T (DEG C), and ordinate is rate of heat flow y (mw.mg
-1), determine the starting point (Tm, ym) of exothermic peak and the end point (Tn, yn) of exothermic peak from DSC curve, be connected as the datum line of exothermic peak with straight line between starting point with end point;
2) according to starting point (Tm, ym) and the end point (Tn, yn) of exothermic peak, by
calculate the y value bx of the datum line between Tm and Tn corresponding to arbitrary temp Tx (Tm<Tx<Tn);
3) T
mwith T
nbetween temperature T
m, T
m+1..., T
x..., T
ncorresponding rate of heat flow is y
m, y
m+1..., y
x..., y
n, the datum line y value corresponding to each temperature is b
m, b
m+1..., b
x..., b
n, accordingly by
Calculate the area A of exothermic peak
m;
4) use the same method the DSC curve making shrend slag specimen the area A calculating exothermic peak
n;
5) by
calculate the ratio k in Solidified Flux Film shared by crystal.
Further feature is: the quality of the Solidified Flux Film powdered sample taken or Water Quenching Slag membrane sample powder is 10mg to 15mg.
The first pre-service of Solidified Flux Film, pre-service comprises the steps:
1) get the continuous crystallizer protecting slag of some, to join in graphite crucible in batches and to be positioned in silicon molybdenum stove; Fire box temperature is risen to 1350-1400 DEG C and constant temperature a period of time, make composition and the homogeneous temperature of slag;
2) " location " button on HF-200 slag film heat flux simulation instrument control panel is pressed, positioning system is unlocked, and two backstays start to decline, and when the lower surface of backstay has just touched slag liquid level, backstay stops declining, backstay rises to original height immediately, locates complete; The distance that backstay declines is copper probe and immerses the height that should decline in slag;
3) chilled water is opened, adjustment flowmeter makes cooling water flow stablize, open water heater adjustment cooler-water temperature until water temperature stability is at 35 DEG C ± 3.5 DEG C, press " test " button on HF-200 slag film heat flux simulation instrument control panel, copper probe starts to decline, when copper probe upper surface is concordant with slag liquid level, probe stops declining and tests beginning simultaneously; After test terminates, copper probe is increased to original height, takes off the Solidified Flux Film be attached in copper probe head wall, obtains Solidified Flux Film sample; Get part slag in graphite crucible after shrend, obtain all product of corresponding Water Quenching Slag;
4) grind into powder after Solidified Flux Film and shrend slag specimen being dried, powder obtains the powdered sample of Solidified Flux Film for thermal analyses test and the powdered sample of shrend slag specimen after 200 order dusting covers are sieving through.
The present invention is relative to prior art, and its beneficial effect had is:
The present invention is by the forming process of the HF-200 slag film heat flux simulation instrument slag film in laboratory simulation and under fixing condition, produced the slag membrane sample that can be used for thermal analyses test; propose and by the detection technique of crystal proportion quantification in continuous casting covering slag Solidified Flux Film and analytical approach, foundation can be provided for fully understanding slag membrane structure with the crystallization heat transfer characteristic holding Solidified Flux Film comprehensively.Sample preparation is convenient, and stable equipment operation is reliable, and computing method are clearly feasible, and to the Composition Design of continuous crystallizer protecting slag, laboratory study and performance evaluation all have certain reference value.
Accompanying drawing explanation
Accompanying drawing 1 is the slag membrane structure schematic diagram of crystallizer protecting residue in casting process.
Accompanying drawing 2 is the Temperature Distribution schematic diagram between crystallizer wall and base shell.
Accompanying drawing 3 is HF-200 slag film heat flux simulation instrument schematic diagram.
Accompanying drawing 4 is for being attached to the Solidified Flux Film pictorial diagram in copper probe head wall.
Accompanying drawing 5 is the DSC curve (convex is exothermic peak) in Solidified Flux Film and shrend slag specimen heating process.
Accompanying drawing 6 is the DSC curve (convex is exothermic peak) in low-carbon steel protecting slag Solidified Flux Film temperature-rise period.
Accompanying drawing 7 is the DSC curve (convex is exothermic peak) in low-carbon steel protecting slag shrend slag specimen temperature-rise period.
Accompanying drawing 8 is the DSC curve (convex is exothermic peak) in medium carbon steel covering slag Solidified Flux Film temperature-rise period.
Accompanying drawing 9 is the DSC curve (convex is exothermic peak) in medium carbon steel covering slag shrend slag specimen temperature-rise period.
In accompanying drawing, 1-submersed nozzle, 2-slag layer, 3-liquid slag layer, 4-crystallizer, 5-slag circle, 6-initial solidification shell, 7-melt cinder film, 8-crystalline state slag film, 9-glassy state slag film, 10-air gap, 11-crystallizer, 12-air gap, 13-glassy state slag film, 14-crystalline state slag film, 15-melt cinder film, 16-initial solidification shell, 17-cooling water pipe, 18-copper is popped one's head in, 19-Solidified Flux Film, the liquid covering slag of 20-, 21-graphitic steel pot, 22-alumina pedestal, 23-thermopair, 24-fire resistive material, 25-silicon molybdenum stove, 26-corundum furnace tube, 27-is equipped with the corundum sleeve pipe of thermopair, the DSC curve of 28-covering slag Solidified Flux Film in temperature-rise period, the DSC curve of 29-covering slag shrend slag specimen in temperature-rise period.
Embodiment
Describe the specific embodiment of the present invention in detail below in conjunction with embodiment and accompanying drawing thereof, but the specific embodiment of the present invention is not limited to following embodiment.
The decision method of a kind of continuous crystallizer protecting slag Solidified Flux Film of the present invention crystallization ratio, implementation step is as follows: the Water Quenching Slag film obtained after quenching with differential scanning calorimeter detection Solidified Flux Film and high-temperature solid slag film water, heat enthalpy value in temperature-rise period and to Analysis of test results process, obtains the ratio k shared by crystal in Solidified Flux Film and shrend slag specimen;
Described differential scanning calorimeter detects slag film and the heat enthalpy value of Water Quenching Slag in temperature-rise period comprises the steps:
1) take certain mass Solidified Flux Film powdered sample with electronic balance, be positioned in corundum crucible;
2) utilize differential scanning calorimeter, the crucible of sample will be housed from room temperature to 900-1300 DEG C with the heating rate of 10-25 DEG C/min, obtain the DSC curve of sample in heating process, horizontal ordinate is temperature T, and unit is DEG C; Ordinate is rate of heat flow, and unit is mw.mg
-1; In whole process, in crucible, pass into blanket gas;
3), after test terminates, the thermal analysis software supporting with thermal analyzer is utilized test result to be exported in text document the calculating being used for crystallization ratio; The supporting thermal analysis software of thermal analyzer is prior art, or those skilled in the art are according to content disclosed by the invention, can work out this thermal analysis software, by calculating and the process of this software, obtains the related data that the present invention needs.
4) use the same method and obtain the thermal analyses testing result of Water Quenching Slag membrane sample powder;
The calculating of described crystallization ratio comprises the steps:
1) make DSC curve according to the detection data of the Solidified Flux Film imported in text document, convex is exothermic peak, and horizontal ordinate is temperature T (DEG C), and ordinate is rate of heat flow y (mw.mg
-1), determine the starting point (Tm, ym) of exothermic peak and the end point (Tn, yn) of exothermic peak from DSC curve, be connected as the datum line of exothermic peak with straight line between starting point with end point;
2) according to starting point (Tm, ym) and the end point (Tn, yn) of exothermic peak, by
calculate the y value bx of the datum line between Tm and Tn corresponding to arbitrary temp Tx (Tm<Tx<Tn);
3) T
mwith T
nbetween temperature T
m, T
m+1..., T
x..., T
ncorresponding rate of heat flow is y
m, y
m+1..., y
x..., y
n, the datum line y value corresponding to each temperature is b
m, b
m+1..., b
x..., b
n, accordingly by
Calculate the area A of exothermic peak
m;
4) use the same method the DSC curve making shrend slag specimen the area A calculating exothermic peak
n;
5) by
calculate the ratio k in Solidified Flux Film shared by crystal.
The quality of the Solidified Flux Film powdered sample taken or Water Quenching Slag membrane sample powder is 10mg to 15mg.
If Solidified Flux Film requirement according to the invention, then directly choose; If do not meet application claims, need first pre-service, pre-service comprises the steps:
1) get the continuous crystallizer protecting slag of some, to join in graphite crucible in batches and to be positioned in silicon molybdenum stove; Fire box temperature is risen to 1350-1400 DEG C and constant temperature a period of time, make composition and the homogeneous temperature of slag;
2) " location " button on HF-200 slag film heat flux simulation instrument control panel is pressed, positioning system is unlocked, and two backstays start to decline, and when the lower surface of backstay has just touched slag liquid level, backstay stops declining, backstay rises to original height immediately, locates complete; The distance that backstay declines is copper probe and immerses the height that should decline in slag;
3) chilled water is opened, adjustment flowmeter makes cooling water flow stablize, open water heater adjustment cooler-water temperature until water temperature stability is at 35 DEG C ± 3.5 DEG C, press " test " button on HF-200 slag film heat flux simulation instrument control panel, copper probe starts to decline, when copper probe upper surface is concordant with slag liquid level, probe stops declining and tests beginning simultaneously; After test terminates, copper probe is increased to original height, takes off the Solidified Flux Film be attached in copper probe head wall, obtains Solidified Flux Film sample; Get part slag in graphite crucible after shrend, obtain corresponding Water Quenching Slag membrane sample;
4) grind into powder after Solidified Flux Film and shrend slag specimen being dried, powder obtains the powdered sample of Solidified Flux Film for thermal analyses test and the powdered sample of Water Quenching Slag film after 200 order dusting covers are sieving through.
First the present invention obtains Solidified Flux Film and corresponding shrend slag specimen at use for laboratory HF-200 slag film heat flux simulation instrument in laboratory, then Solidified Flux Film and shrend slag specimen are carried out respectively thermal analyses test and obtain DSC curve, horizontal ordinate is temperature T (DEG C), and ordinate is rate of heat flow y (mw.mg
-1), finally calculate the area of exothermic peak in slag tap film and shrend slag specimen heating process respectively, and then go out the ratio in Solidified Flux Film shared by crystal by the exothermic peak areal calculation of DSC curve.
The slag membrane structure of crystallizer protecting residue in casting process shown in Fig. 1, molten steel is injected in crystallizer by submersed nozzle 1, simultaneously for the fusing of the covering slag granulated slag 2 on mold liquid level provides heat; The granulated slag 1 of fusing forms liquid slag layer 3 on molten steel face, and melt cinder 3 flow between initial solidification shell 6 and crystallizer 4, and near meniscus, form slag circle 5; Near initial solidification shell 6 side, temperature higher formation melt cinder film 7; Near crystallizer 4 side, cooling velocity larger formation glassy state slag film 9, be attended by volumetric contraction in slag film cooling procedure simultaneously and form air gap 10; Crystalline state slag film 8 is formed between glassy state slag film 9 and melt cinder film 7.
Crystallizer shown in Fig. 2 and the Temperature Distribution schematic diagram between solidified shell, the temperature between crystallizer 11 and solidified shell 16 increases gradually with the increase of the distance apart from crystallizer 14; The air gap 12 that one deck is very thin is had between crystallizer 11 and glassy state slag film 13; Near solidified shell 16 side is melt cinder 15, forms crystalline state slag film 14 between melt cinder 15 and glassy state slag film 13.
HF-200 slag film heat flux simulation instrument schematic diagram as shown in Figure 3, the graphite crucible 21 that covering slag granulated slag is housed is positioned on the alumina pedestal 22 in corundum furnace tube 26; By silicon molybdenum stove 25 by the granulated slag heat fused in graphite crucible 21, measure fire box temperature by the thermopair 27 of crucible bottom, silicon molybdenum stove outside is fire resistive material 24 simultaneously; After forming uniform molten bath 20 in graphite crucible 21, chilled water is flow in copper probe 18 by cooling water pipe 17, forms Solidified Flux Film 19 after melt cinder 20 is cooled in probe head wall 18; The Inlet and outlet water temperature difference can be recorded by the thermopair 23 in cooling water pipe 17.
DSC curve in Solidified Flux Film as shown in Figure 5 and Water Quenching Slag film heating process, there is an exothermic peak in the DSC curve 28 in Solidified Flux Film heating process; An exothermic peak appears in the DSC curve 29 in Water Quenching Slag film heating process, and exothermic peak area ratio slag film heat transfer peak area wants large.
Embodiment
Judge in the present embodiment that the material of continuous crystallizer protecting slag Solidified Flux Film crystallization ratio is as the covering slag at industry spot cast medium carbon steel and mild carbon steel.Calculated results is analyzed in conjunction with the feature showed in different steel grade casting process, the feasibility of crystallization than decision method and the consistance of calculated value and Solidified Flux Film structure can be further illustrated.
The concrete steps of the present embodiment are:
Solidified Flux Film is anticipated: get 350g remove charcoal after to join in graphite crucible for the slab continuous casting crystallizer protection slag pouring into a mould mild carbon steel in batches and be positioned in silicon molybdenum stove, fire box temperature is risen to 1400 DEG C and constant temperature makes composition and the homogeneous temperature of slag for 15 minutes;
Press " location " button on HF-200 slag film heat flux simulation instrument control panel, positioning system is unlocked, and two backstays start to decline, and when the lower surface of backstay has just touched slag liquid level, backstay stops declining, backstay rises to original height immediately, locates complete; The distance that backstay declines is probe and immerses the height that should decline in slag;
Open chilled water, adjustment flowmeter makes cooling water flow be stabilized in 200L/h, open water heater adjustment cooler-water temperature until water temperature stability is at 35 DEG C ± 0.5 DEG C, press " test " button on HF-200 slag film heat flux simulation instrument control panel, copper probe starts to decline, when copper probe upper surface is concordant with slag liquid level, probe stops declining and starts timing simultaneously; Test end after 45 seconds, probe is increased to original height, and take off the Solidified Flux Film be attached in copper probe head wall, obtain Solidified Flux Film sample, the part slag (about 50g) in graphite crucible, after rapid shrend, obtains corresponding Water Quenching Slag membrane sample;
Grind into powder after Solidified Flux Film and Water Quenching Slag film are dried, powder obtains the powdered sample of Solidified Flux Film and the powdered sample of Water Quenching Slag film that can be used for thermal analyses test after 200 order dusting covers are sieving through;
Take slag film powdered sample 10mg ± 2mg with electronic balance, be positioned in corundum crucible;
Utilize German NETSCHSTA449F3Jupiter synchronous solving, the crucible of sample will be housed from room temperature to 900 DEG C with the heating rate of 20 DEG C/min, obtain the DSC curve of sample in heating process, horizontal ordinate is temperature T, and unit is DEG C; Ordinate is rate of heat flow, and unit is mw.mg
-1; Whole process passes into blanket gas, as inert gases such as argon gas, or nitrogen, as blanket gas, argon flow amount is 50mL/min;
After test terminates, utilize the thermal analysis software NETZSCH supporting with thermal analyzer
test data is exported in text document the calculating being used for crystallization ratio by Thermal Analysis;
Make DSC curve (convex is exothermic peak) according to the detection data of the Solidified Flux Film imported in text document, if Fig. 6 horizontal ordinate is temperature T (DEG C), ordinate is rate of heat flow y (mw.mg
-1), from DSC curve determine exothermic peak starting point (485 DEG C, 0.1438mw.mg
-1) and exothermic peak end point (700 DEG C, 0.3918mw.mg
-1), be connected as the datum line of exothermic peak with straight line between starting point with end point;
According to starting point and the end point of exothermic peak, by b
x=0.1438+0.0012 × (T
x-485) the y value bx of the datum line between Tm and Tn corresponding to arbitrary temp Tx (485<Tx<700) is calculated;
Temperature T between 485 DEG C and 700 DEG C
m, T
m+1..., T
x..., T
ncorresponding rate of heat flow is 0.1438, y
m+1..., y
x..., 0.3918, the datum line y value corresponding to each temperature is 0.1438, b
m+1..., b
x..., 0.3918, accordingly by
Calculate the area A of exothermic peak
m, A
mresult of calculation is 12.78;
Use the same method the DSC curve (as Fig. 7) the area A calculating mild carbon steel shrend slag specimen exothermic peak of making low-carbon steel protecting slag shrend slag specimen
n, A
nresult of calculation is 28.24;
By
calculate the ratio k in Solidified Flux Film shared by crystal; The result of calculation of low-carbon steel protecting slag Solidified Flux Film crystallization ratio is k=1-12.78/28.24=0.547.
Same method of testing is used for Solidified Flux Film and the shrend slag specimen of producing Mold Flux for Slab Casting of Medium-Carbon Steel covering slag, Solidified Flux Film and shrend slag specimen are carried out thermal analyses detection respectively; The starting point drawing exothermic peak by the DSC curve of medium carbon steel covering slag Solidified Flux Film for (498 DEG C, 0.1677mw.mg
-1), end point be (582 DEG C, 0.2617mw.mg
-1), as shown in Figure 8; The area that can calculate the exothermic peak occurred in Solidified Flux Film heating process is thus 2.45; The starting point drawing exothermic peak by the DSC curve of shrend slag specimen for (486 DEG C, 0.09825mw.mg
-1), end point be (596 DEG C, 0.2629mw.mg
-1), as shown in Figure 9; Calculating shrend slag specimen exothermic peak area is thus 25.06; The ratio calculated in medium carbon steel covering slag Solidified Flux Film shared by crystal is k=1-2.45/25.06=0.902.
Be analyzed as follows result of calculation, the crystallization ratio of the Solidified Flux Film of the mild carbon steel plate blank protecting slag calculated is 0.547, lower than the crystallization ratio of Mold Flux for Slab Casting of Medium-Carbon Steel covering slag Solidified Flux Film.In conjunction with the steel grade that two kinds of carbon contents are different, in mild carbon steel casting process, casting billet surface is not easy to form longitudinal crack, the Solidified Flux Film crystallization calculated is than on the low side, and the heat transmitted to crystallizer by strand is comparatively large, and the base shell that can form adequate thickness reduces the generation of sticker type breakout accident; And medium carbon steel in process of setting due to peritectic reaction, very easily produce surface longitudinal crack of slab along with volumetric contraction, the medium carbon steel slag membrane crystallization calculated is higher than relatively, and this is conducive to controlling the transmission of heat to crystallizer, realize base shell Slow cooling, avoid the generation of longitudinal crack.Visible, the feature of pouring of two kinds of steel grades in the realistic production run of calculated results, calculated value is consistent with the practical structures of Solidified Flux Film.
Claims (3)
1. the decision method of a continuous crystallizer protecting slag Solidified Flux Film crystallization ratio, it is characterized in that, the Water Quenching Slag film obtained after quenching with differential scanning calorimeter detection Solidified Flux Film and high-temperature solid slag film water, heat enthalpy value in temperature-rise period and to Analysis of test results process, obtains the ratio k shared by crystal in Solidified Flux Film and shrend slag specimen;
Described differential scanning calorimeter detects slag film and the heat enthalpy value of Water Quenching Slag in temperature-rise period comprises the steps:
1) take certain mass Solidified Flux Film powdered sample with electronic balance, be positioned in corundum crucible;
2) utilize differential scanning calorimeter, the crucible of sample will be housed from room temperature to 900-1300 DEG C with the heating rate of 10-25 DEG C/min, obtain the DSC curve of sample in heating process, horizontal ordinate is temperature T, and unit is DEG C; Ordinate is rate of heat flow, and unit is mw.mg
-1; In whole process, in crucible, pass into blanket gas;
3), after test terminates, the thermal analysis software supporting with thermal analyzer is utilized test result to be exported in text document the calculating being used for crystallization ratio;
4) use the same method and obtain the thermal analyses testing result of Water Quenching Slag membrane sample powder;
The calculating of described crystallization ratio comprises the steps:
1) make DSC curve according to the detection data of the Solidified Flux Film imported in text document, convex is exothermic peak, and horizontal ordinate is temperature T (DEG C), and ordinate is rate of heat flow y (mw.mg
-1), determine the starting point (Tm, ym) of exothermic peak and the end point (Tn, yn) of exothermic peak from DSC curve, be connected as the datum line of exothermic peak with straight line between starting point with end point;
2) according to starting point (Tm, ym) and the end point (Tn, yn) of exothermic peak, by
calculate the y value bx of the datum line between Tm and Tn corresponding to arbitrary temp Tx (Tm<Tx<Tn);
3) T
mwith T
nbetween temperature T
m, T
m+1..., T
x..., T
ncorresponding rate of heat flow is y
m, y
m+1..., y
x..., y
n, the datum line y value corresponding to each temperature is b
m, b
m+1..., b
x..., b
n, accordingly by
Calculate the area A of exothermic peak
m;
4) use the same method the DSC curve making shrend slag specimen the area A calculating exothermic peak
n;
5) by
calculate the ratio k in Solidified Flux Film shared by crystal.
2. the decision method of continuous crystallizer protecting slag Solidified Flux Film crystallization ratio according to claim 1, it is characterized in that, the quality of the Solidified Flux Film powdered sample taken or Water Quenching Slag membrane sample powder is 10mg to 15mg.
3. the decision method of continuous crystallizer protecting slag Solidified Flux Film crystallization ratio according to claim 1, is characterized in that, the first pre-service of Solidified Flux Film, pre-service comprises the steps:
1) get the continuous crystallizer protecting slag of some, to join in graphite crucible in batches and to be positioned in silicon molybdenum stove; Fire box temperature is risen to 1350-1400 DEG C and constant temperature a period of time, make composition and the homogeneous temperature of slag;
2) " location " button on HF-200 slag film heat flux simulation instrument control panel is pressed, positioning system is unlocked, and two backstays start to decline, and when the lower surface of backstay has just touched slag liquid level, backstay stops declining, backstay rises to original height immediately, locates complete; The distance that backstay declines is copper probe and immerses the height that should decline in slag;
3) chilled water is opened, adjustment flowmeter makes cooling water flow stablize, open water heater adjustment cooler-water temperature until water temperature stability is at 35 DEG C ± 3.5 DEG C, press " test " button on HF-200 slag film heat flux simulation instrument control panel, copper probe starts to decline, when copper probe upper surface is concordant with slag liquid level, probe stops declining and tests beginning simultaneously; After test terminates, copper probe is increased to original height, takes off the Solidified Flux Film be attached in copper probe head wall, obtains Solidified Flux Film sample; Get part slag in graphite crucible after shrend, obtain corresponding Water Quenching Slag membrane sample;
4) grind into powder after Solidified Flux Film and shrend slag specimen being dried, powder obtains the powdered sample of Solidified Flux Film for thermal analyses test and the powdered sample of Water Quenching Slag film after 200 order dusting covers are sieving through.
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