CA2117083A1 - A process and an apparatus for the manufacture of billets and blooms from a continuously cast steel showing high or excellent quality - Google Patents
A process and an apparatus for the manufacture of billets and blooms from a continuously cast steel showing high or excellent qualityInfo
- Publication number
- CA2117083A1 CA2117083A1 CA002117083A CA2117083A CA2117083A1 CA 2117083 A1 CA2117083 A1 CA 2117083A1 CA 002117083 A CA002117083 A CA 002117083A CA 2117083 A CA2117083 A CA 2117083A CA 2117083 A1 CA2117083 A1 CA 2117083A1
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- CA
- Canada
- Prior art keywords
- casting
- product
- distortion
- section
- point
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
- Metal Rolling (AREA)
- Heat Treatment Of Steel (AREA)
- Mold Materials And Core Materials (AREA)
Abstract
A process for the manufacture of billets and blooms from continuously cast steel, allowing such long products to be directly conveyed to a finishing rolling mill in a plant supplying high quality steel and/or excellent quality steel. Said process is comprising a liquid core distortion stage, concerning the casting cross section and causing the reduction of the same cross section, the perimeter remaining unchanged (equal). Said distortion occurs in the zone comprised between the point (S), last point on the casting axis (X-X) where superheated liquid is still present, and the point (L) where the casting is completely solidified (end of the metallurgical length). Preferably, said distortion is carried out between the points respectively corresponding to 10 % and 80 % of the concentration of solid grains in the fluid mass. An apparatus is described too, essentially comprising means for bringing at least one of the sectors forming the roller train (along the casting route) near the opposite one, in at least one plane containing the casting axis (X-X), in correspondence of said distortion zone.
Description
W093/~02 PCT/~2/00113 211 7~)83 :
A PR~CESS AND AN APPARATUS FOR TH~ MANl!FACT'~JRE OF BILLETS AND BLOOMS FROM
A CONTINUOUSLY CAST STEEL SHOWING HIGH OR EXCELLENT QUALITY
~*~*~*~*******~**********~
The present invention relates to a process for the di-rect ~anufacture of billets and blooms from a conti-nuously cast steel showing high or excellent quality, as well as an apparatus for the realization of such process.
It is known that the continuous casting is ever more utilized for the manufacture of steel, because of the clear and well known advantages therein involved, with respect to other kinds of casting. It is clear however that the thus obtained product, as it appears at the extracting machine at the end of the curvilinear ca-sting route, shows the features of a typical castingpiece, with all the qualitative drawbacks typical of these semifinished products. It is in fact possible to see, by a metallographic analysis, that the grain size and the structure isotropy are unsatisfactory and that the carbon percentage is not homogeneous but prevailin-gly concentrated in the central zone of the product, with a~(consequent) kish (segregation~l which makes the product, coming from the continuous casting, not direc-tly exploitable for the rolling, when it is desirable to obtain end products consisting of high and excellent quality steel.
In the case of a high quality steel, the continuous ca-sting can be exploited for obtaining blooms, which, a-W093/~802 PCT/~2/00113 211~0~3 2 -fter transit through an oven, are conveyed to a size-breaking rolling mill, in order to be converted into billets, which in their turn, optionally heated in a further oven, are eventually conveyed to a finishing rolling mill. In the case of an excellent quality steel, the casting isieven occurring in the form of an ingot, and not in a continuous way, and in each ingot the cooling is adjusted by means of a predetermined cy-cle; therefore, the ingots, or the big size blooms, are conveyed to the size-breaking and subsequently to the pre-rolling (cogging) and to the finishing rolling, wherein there are usually provided, between two subse-quent operations, intermediate heatings in an oven, thus performing an extremely long and expensive opera-tive cycle.
It is thus a purpose of the instant invention to supllya process allowing the direct manufacture, by means of a continuous casting, of billets or blooms showing such - features as to be easily trasferred, in a subse~uent time and without any further operation, to the fini-shing rolling. Another object of the instant invention is residing in an apparatus for the realization of said process.
An advantage coming from the process according to the invention, described hereinbelow, is residing in that the consequent inner grain of the casting product is showing those features of fineness, homogeneity and i-sotropy, as well as of absolute absence of kish (segre-gation), which are usually obser~ed in a product ready for the finishing rolling, thus omitting the steps con-cerning size-breaking and pre-rolling, including the WOg3/~80~ PCT/~2/00113 3 2117083 ~
respective intermediate heatings, and thus reaching a considerable power saving.
The process according to the instant invention is cha~
racterized by a liquid core distortion of the casting product, obtained by means of a continuous casting, which causes a reduction of the product cross-section, the perimeter of the same cross- section being unchan-ged, in the route between the lowermost geometrical point on the casting axis, where it is still possible to find superheated liquid, and the end point of the metallurgical length, where the product is completely solidified.
According to a preferred embodiment of the instant in-vention, said distortion is made to occur in a zone where the concentration of the solid grains is from 10 to 80%.
The distortion hereinabove, from a practical point of view, can involve the conversion of the shape from round to square (billet) or to rectangular (bloom), or from billet t bloom or also, starting from this latter, to a more flattened cross-section.
The apparatus for carrying out the process according to the invention is essentially comprising at least one of the sectors of the roller train along the curvili-near`route, which is given the possibility of movementwith respect to the opposite sector, and means fit for bringing said mobile sector near the opposite one on at least one plane containing the casting axis.
The purposes, the advantages and the features of the process and of the apparatus according to the instant invention will be clearer from the following detailed description and drawings, which are supplied for illu-strating purposes but do not limit in any way the scope of the same invention.
As to the drawings: ~-FIGURE 1 is showing an extremely schematic view of the sole casting product along the curvilinear route, in order to point out the basic parameters of the process according to the invention;
FIGURE 2 is showing an equally schematic view of a con-tinuous casting apparatus, modified as to realize the process according to the invention; and FIGURE 3 is showing a section view along line III-III
of Fig. 2, in the case of the distortion of a rod.
Referring now to Fig^ 1, there is represented, in an extremely schema~ic way and in a section containing the casting axls X-X, a product made from steel during a continuous casting. By lo there is indicated the free surface of the liquid in the ingot mold (ladle) and by S the lowermost geometrical point, on the casting axis, `
where it is still possible to find superheated liquid~
In other words, below S the temperature reaches the "liquidus" value, typical of each peculiar steel, whe-reas above the two lines s1 and s2 the temperature va-lue is higher and the liquid, in such zone, is super-heated and void of solid grains.
The position of point S can be determined, for each ca-sting mill, depending on the temperature value of the st~ l contained in the ~ above the "li~uidus" va-lue, according to the kind of the steel, and can be ex-pressed by means of time terms (t), corresponding to acertain speed. From the determination of the time t it SUBSl`ITU~ SH~ET
` ~
W093/~02 PCT/~2/00113 ~
2117083 -~
is possible to extrapolate the position of S depending on the different possible casting velocities.
It is usually supposed that point S be lying below the ladle, and precisely in the first leg of the roller train, commonly defined "segment zero" (extractable section). L is representing the point where the casting product is completely solidified and the distance l observed between such point and point S, is commonly defined "metallurgical length".
It is believed that the liquid lying below the two li~
nes sl and s2 and comprised between such lines and the inner walls of the already solidified portion P
`("skin") be already containing solid grains with a con-centration increasing towards the lower zone, until the complete solidification in L. In this viscous or semi-solid mass (M) are in fact in equilibrium either the true actual liquid or the solid suspended grains On the X-X axis, the concentration of the solid grains in the mass (M) is e~ual to zero in s and to l00% in L, linearly increasing along with the metallurgical length.
The progression speed of the solid portion P is clearly equal in every point, whereas the speed of the mass (M~
has to fulfill a different condition, namely to feed the solidification process as to avoid the formation of empty zones before point L, which would involve the presence of cracks in the end product. It has to be furtherly remarked that the metallurgical length lm has to be such as to allow point L to be upstream of the 3o extraction device 20, lying at the end of the curvili-near casting route (see Fig. 2).
W093/~02 ~CT/~2/00113 It was now surprisingly found that by compressing ac-cording to the invention the walls P of the "liquid co-re" casting product, namely before point L, thus redu-cing the volume of the same product by distorting its cross-section, there is obtained a bloom or a billet showing all the desired features hereinabove fit for obtaining a steel product having a high or excellent quality.
The mechanism allowing such a transformation is not lo completely clear, but it is believed that by bringing the solid walls P near each other, there occurs, inside the fluid mass M, which contains already solidified grains and which can be defined semisolid or "viscous", a speed gradient or acceleration, causing the breaking of the dendritic ~ranchings which tend to form inside the same mass. The thus crushed grains get reduced in their size and are oriented in a way as random (casual) as possible, thus acquiring particular isotropy and ho-mogeneity features, while avoiding segregations, namely increasing concentrations of carbon ~kish) towards the inner portion of the product.
An essential condition, in order to make such results to occur, is however residing in that the liquid core distortion, carried out between points S and L, be re-ducing the volume of the casting product, the lengthbeing equal (unchanged), whereas its lateral surface is maintained constant; in this case in fact there are neither stretching nor rolling action, in a true actual sense, involving a creep (slippage) of solid material, until we are in the presence of a viscous mass M inside the product itself, namely along the whole length l W093/~02 PCT'~ d ~ 3 In terms of cross-section (the length in fact doesn't have any impact, as it is kept constant), the area of the cross-section has to be reduced, whereas its peri-meter is approximately kept constant.
The following distortions will therefore be possible:
- from round product to square product (billets) or to rectangular product (blooms); or -from square billets to rectangular blooms; or, at last - from a certain bloom to a more flattened product (bloom or slab), namely a product showing a higher ra-tio between the different sides.
From a theoretical point of view, there would be possi-ble even a distortion involving the conversion of a ca-sting cross-section having n sides to a distorted cross-section having, at the end of the metallurgical length, n-1 sides, even if such hypothesis has poor chances to be reduced to practice.
It has to be underlined that should the distortion oc-cur without the fulfilment of such a condition, the vo-lume would increase or would at the most remain at aconstant leve~; there would therefore fail the presup-position for obtaining the desired features hereinabo-ve, allowing the product to be directly conveyed to the finishing rolling, without any intermediate operative step, as it is already endowed with all the features of the desired semifinished product.
As it was already said, the distortion according to the instant invention can occur all along the metallurgical length, starting from point S, but preferably inside a limited zone thereof; this latter can be defined as the zone corresponding to the 10-80% of the percentage con~
W093/0~02 PCT/~92/00113 '~117083 centration x of solid grains in the mass M, which can be easily determined if we take into account that xs=O
and that xL=lO0. Therefore if lS is the distance of S
from loJ the xl concentration in a whatsoever point far ^
l from lo is:
1 - lS
x = --____ lm It can be useless in fact to carry out the distortion with volume reduction in a too high zone of the ca-sting, where the concentration of the solid grains is least and the grains themselves couldn't be affected, because of their dispersion in the liquid mass, by the mechanical action exerted by the solidified walls P. .
From the other side, it can even be a drawback to perform the distortion in the lowermost zone, in the proximity of point L, where the walls P are already so near as to easily build up a few weldings and conse- ~.
quently a few pockets containing liquid material which, by solidification and consequent volume shrinking, would give rise to cavities inside the product, which drawback has preferably to be avoided.
Referring to Fig. 2, there is represented, in an ex~
tremely schematic way, an apparatus fit for carrying out the process according to the invention, as it is shortly decribed hereinbelow. The product l, contained in the ingot mold lO, descends, through the so called "foot rolls" ll along the roller train 13, defined by pairs of opposed sectors of roller cages 12, 14, 12', 14' and so on. The first sector, immediately after the foot rolls ll, where it is believed sufficient, in cer-~ ~ .
- 21170~3 ;;
tain cases, to limit the volume reducing distortion ac~
cordîng to the present invention, is usually called Se~e~rS
"segment zero". ~e~o~s 12, 12', 12'' and so on are all o~ t~
lying on the ~ of the curvilinear~s, namely Se~
they have a greater bending radius, whereas ~r~ 14, ~e~
14' and so on are defined ~s~ade~ segments. The rolls i~4~r of ,~c~t~r 12 are represented by the re~erence number se~ t 12a and the ones of ~e~ 14 by the reference number 14a and so on.
According to the instant invention and to the hypothe-. sis above, according to which the distortion according d~ ~r to the invention is determined by said first ~ ~r, the t~oJ portion 14 is made to be mobile with re~
spect to the ~L-l~$ 12 in whatsoever known way, there being provided means 16 for drawing cage 14 near the opposite cage 12, which remalns motionless. As it is reported on Fig. 2, the cage or bearing structure 14, comprising rolls 14a, is pivoted in 15 at one of its ends, preferably the superior one, and a hydraulic pi-ston 16 pushes the opposite end of the Z~GQ~ struc-~ ~J~
ture towards the motionless ~etra~eg 12. Of course, there can be provided whatsoever other solution of the problems, known to the skilled in the art; it is thus possible, for instance, to let the 14 slide along a skid device and to provide one or more hydraulic pistons for the thrust along the same skid device. In any case, an apparatus of this kind can be used when a square product or billet has to be conver-ted into a bloom or when an already rectangular pro-duct, like a bloom, has to be converted into an always rectangular however more flattened shape, for instance ~S~ 5~EE~
1 o - 1 7 0 8 3 a (thick) slab.
Should on the contrary a round product be converted, by means of distortion, into a product showing a square or rectangular cross-section, it is no more sufficient to work in the plane of Fig. 2, but a corresponding action has to be contemporaneously carried out in a plane nor-mal to the plane above, always containing the casting axis X-X, as it is recorded on the section view of Fig.
3. In this case the distortion of a round product 1 is contemporaneously caused by two pairs of rolls, lying in diametrically opposed positions of the perimeter of the same round product, namely rolls 12a and l~a of the opposite ~r~ and -~nt~9~ cages 12 and 14, recor-ded on Fig. 2, as well as rolls 22a and 24a, respecti-vely belonging to roll cages not reported in Fig. 2,having the opposite rolls oriented normally to the rolls 12a and 14a of cages 12 and 14.
Prefera~ly the subsequent rolls, downstream of the ones arranged in the sector undergoing distortion, are sup-plied with pistons fit for exerting a thrust towardsthe inside of the casting, no more for distortion pur-poses but for opposing the ferrostatic pressure and the possible consequent swelling, which can occur between the contact with a roll and the subsequent one, thus fitting to the size reached in the preceeding distor-tion phase.
EXAMPLE
From a continuous casting -ladle, having a round cross-section, it was cast, with a progression speed 3o V-2m/min., a round product (rod) having a diameter of 130 mm. Xn a zone between 28% and 76% of the concentra-5 ~ S ~ r~T
W093/~2 PCT/~2/00113 tion of the solid grains and by a metallurgical length equal (in this case) to 8 m, there was caused a distor-tion leading to a substantially square billet having a 100 mm side.
Subsequently the same rod was converted in another bil-let, having a similar size, however increasing the speed up to 3 m/min., and the distortion, according to the description above, was made to occur in a zone bet-ween the concentration values x equal to 14~ and 46%, whereas the metallurgical length was 12 m.
In both the cases there were sampled specimens of the cast product, once solidification was over, thus fin-ding, by macrographic analysis, the following results:
a) fine structure, without dendritic evidence;
b) structure isotropy, without any main orientation of the grains;
c3 absence of (kish) segregations, with homogeneity, in terms of chemical analysis, all along the cross-section; ~
20 d) isotropy of the mechanical features (tensile ;
strength, yield point, break elongation, impact strength);
e) better mechanical features, with respect to the pro-duct coming from a traditional casting, such as to al-low the reaching of the same end features of the end product with lower percentages of reduction in the xol-ling step.
From the above it is clear that the apparatus according to the instant invention allows the product, coming from the continuous casting and handled according to the process above, to be directly conveyed to a fini-W093/~02 PCT/~2/00113 shing rolling mill, by merely interposing a heati~g o-ven, optionally an induction oven, for adjusting the temperature according to the rolling values.
Optional additions and changes can be carried out by the skilled in the art, as to the process according to the instant invention hereinabove, as well as modifi-cations of the described and illustrated apparatus for carrying out such process, without exceeding the scope of the same invention.
`'''''.,:~
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. .:
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A PR~CESS AND AN APPARATUS FOR TH~ MANl!FACT'~JRE OF BILLETS AND BLOOMS FROM
A CONTINUOUSLY CAST STEEL SHOWING HIGH OR EXCELLENT QUALITY
~*~*~*~*******~**********~
The present invention relates to a process for the di-rect ~anufacture of billets and blooms from a conti-nuously cast steel showing high or excellent quality, as well as an apparatus for the realization of such process.
It is known that the continuous casting is ever more utilized for the manufacture of steel, because of the clear and well known advantages therein involved, with respect to other kinds of casting. It is clear however that the thus obtained product, as it appears at the extracting machine at the end of the curvilinear ca-sting route, shows the features of a typical castingpiece, with all the qualitative drawbacks typical of these semifinished products. It is in fact possible to see, by a metallographic analysis, that the grain size and the structure isotropy are unsatisfactory and that the carbon percentage is not homogeneous but prevailin-gly concentrated in the central zone of the product, with a~(consequent) kish (segregation~l which makes the product, coming from the continuous casting, not direc-tly exploitable for the rolling, when it is desirable to obtain end products consisting of high and excellent quality steel.
In the case of a high quality steel, the continuous ca-sting can be exploited for obtaining blooms, which, a-W093/~802 PCT/~2/00113 211~0~3 2 -fter transit through an oven, are conveyed to a size-breaking rolling mill, in order to be converted into billets, which in their turn, optionally heated in a further oven, are eventually conveyed to a finishing rolling mill. In the case of an excellent quality steel, the casting isieven occurring in the form of an ingot, and not in a continuous way, and in each ingot the cooling is adjusted by means of a predetermined cy-cle; therefore, the ingots, or the big size blooms, are conveyed to the size-breaking and subsequently to the pre-rolling (cogging) and to the finishing rolling, wherein there are usually provided, between two subse-quent operations, intermediate heatings in an oven, thus performing an extremely long and expensive opera-tive cycle.
It is thus a purpose of the instant invention to supllya process allowing the direct manufacture, by means of a continuous casting, of billets or blooms showing such - features as to be easily trasferred, in a subse~uent time and without any further operation, to the fini-shing rolling. Another object of the instant invention is residing in an apparatus for the realization of said process.
An advantage coming from the process according to the invention, described hereinbelow, is residing in that the consequent inner grain of the casting product is showing those features of fineness, homogeneity and i-sotropy, as well as of absolute absence of kish (segre-gation), which are usually obser~ed in a product ready for the finishing rolling, thus omitting the steps con-cerning size-breaking and pre-rolling, including the WOg3/~80~ PCT/~2/00113 3 2117083 ~
respective intermediate heatings, and thus reaching a considerable power saving.
The process according to the instant invention is cha~
racterized by a liquid core distortion of the casting product, obtained by means of a continuous casting, which causes a reduction of the product cross-section, the perimeter of the same cross- section being unchan-ged, in the route between the lowermost geometrical point on the casting axis, where it is still possible to find superheated liquid, and the end point of the metallurgical length, where the product is completely solidified.
According to a preferred embodiment of the instant in-vention, said distortion is made to occur in a zone where the concentration of the solid grains is from 10 to 80%.
The distortion hereinabove, from a practical point of view, can involve the conversion of the shape from round to square (billet) or to rectangular (bloom), or from billet t bloom or also, starting from this latter, to a more flattened cross-section.
The apparatus for carrying out the process according to the invention is essentially comprising at least one of the sectors of the roller train along the curvili-near`route, which is given the possibility of movementwith respect to the opposite sector, and means fit for bringing said mobile sector near the opposite one on at least one plane containing the casting axis.
The purposes, the advantages and the features of the process and of the apparatus according to the instant invention will be clearer from the following detailed description and drawings, which are supplied for illu-strating purposes but do not limit in any way the scope of the same invention.
As to the drawings: ~-FIGURE 1 is showing an extremely schematic view of the sole casting product along the curvilinear route, in order to point out the basic parameters of the process according to the invention;
FIGURE 2 is showing an equally schematic view of a con-tinuous casting apparatus, modified as to realize the process according to the invention; and FIGURE 3 is showing a section view along line III-III
of Fig. 2, in the case of the distortion of a rod.
Referring now to Fig^ 1, there is represented, in an extremely schema~ic way and in a section containing the casting axls X-X, a product made from steel during a continuous casting. By lo there is indicated the free surface of the liquid in the ingot mold (ladle) and by S the lowermost geometrical point, on the casting axis, `
where it is still possible to find superheated liquid~
In other words, below S the temperature reaches the "liquidus" value, typical of each peculiar steel, whe-reas above the two lines s1 and s2 the temperature va-lue is higher and the liquid, in such zone, is super-heated and void of solid grains.
The position of point S can be determined, for each ca-sting mill, depending on the temperature value of the st~ l contained in the ~ above the "li~uidus" va-lue, according to the kind of the steel, and can be ex-pressed by means of time terms (t), corresponding to acertain speed. From the determination of the time t it SUBSl`ITU~ SH~ET
` ~
W093/~02 PCT/~2/00113 ~
2117083 -~
is possible to extrapolate the position of S depending on the different possible casting velocities.
It is usually supposed that point S be lying below the ladle, and precisely in the first leg of the roller train, commonly defined "segment zero" (extractable section). L is representing the point where the casting product is completely solidified and the distance l observed between such point and point S, is commonly defined "metallurgical length".
It is believed that the liquid lying below the two li~
nes sl and s2 and comprised between such lines and the inner walls of the already solidified portion P
`("skin") be already containing solid grains with a con-centration increasing towards the lower zone, until the complete solidification in L. In this viscous or semi-solid mass (M) are in fact in equilibrium either the true actual liquid or the solid suspended grains On the X-X axis, the concentration of the solid grains in the mass (M) is e~ual to zero in s and to l00% in L, linearly increasing along with the metallurgical length.
The progression speed of the solid portion P is clearly equal in every point, whereas the speed of the mass (M~
has to fulfill a different condition, namely to feed the solidification process as to avoid the formation of empty zones before point L, which would involve the presence of cracks in the end product. It has to be furtherly remarked that the metallurgical length lm has to be such as to allow point L to be upstream of the 3o extraction device 20, lying at the end of the curvili-near casting route (see Fig. 2).
W093/~02 ~CT/~2/00113 It was now surprisingly found that by compressing ac-cording to the invention the walls P of the "liquid co-re" casting product, namely before point L, thus redu-cing the volume of the same product by distorting its cross-section, there is obtained a bloom or a billet showing all the desired features hereinabove fit for obtaining a steel product having a high or excellent quality.
The mechanism allowing such a transformation is not lo completely clear, but it is believed that by bringing the solid walls P near each other, there occurs, inside the fluid mass M, which contains already solidified grains and which can be defined semisolid or "viscous", a speed gradient or acceleration, causing the breaking of the dendritic ~ranchings which tend to form inside the same mass. The thus crushed grains get reduced in their size and are oriented in a way as random (casual) as possible, thus acquiring particular isotropy and ho-mogeneity features, while avoiding segregations, namely increasing concentrations of carbon ~kish) towards the inner portion of the product.
An essential condition, in order to make such results to occur, is however residing in that the liquid core distortion, carried out between points S and L, be re-ducing the volume of the casting product, the lengthbeing equal (unchanged), whereas its lateral surface is maintained constant; in this case in fact there are neither stretching nor rolling action, in a true actual sense, involving a creep (slippage) of solid material, until we are in the presence of a viscous mass M inside the product itself, namely along the whole length l W093/~02 PCT'~ d ~ 3 In terms of cross-section (the length in fact doesn't have any impact, as it is kept constant), the area of the cross-section has to be reduced, whereas its peri-meter is approximately kept constant.
The following distortions will therefore be possible:
- from round product to square product (billets) or to rectangular product (blooms); or -from square billets to rectangular blooms; or, at last - from a certain bloom to a more flattened product (bloom or slab), namely a product showing a higher ra-tio between the different sides.
From a theoretical point of view, there would be possi-ble even a distortion involving the conversion of a ca-sting cross-section having n sides to a distorted cross-section having, at the end of the metallurgical length, n-1 sides, even if such hypothesis has poor chances to be reduced to practice.
It has to be underlined that should the distortion oc-cur without the fulfilment of such a condition, the vo-lume would increase or would at the most remain at aconstant leve~; there would therefore fail the presup-position for obtaining the desired features hereinabo-ve, allowing the product to be directly conveyed to the finishing rolling, without any intermediate operative step, as it is already endowed with all the features of the desired semifinished product.
As it was already said, the distortion according to the instant invention can occur all along the metallurgical length, starting from point S, but preferably inside a limited zone thereof; this latter can be defined as the zone corresponding to the 10-80% of the percentage con~
W093/0~02 PCT/~92/00113 '~117083 centration x of solid grains in the mass M, which can be easily determined if we take into account that xs=O
and that xL=lO0. Therefore if lS is the distance of S
from loJ the xl concentration in a whatsoever point far ^
l from lo is:
1 - lS
x = --____ lm It can be useless in fact to carry out the distortion with volume reduction in a too high zone of the ca-sting, where the concentration of the solid grains is least and the grains themselves couldn't be affected, because of their dispersion in the liquid mass, by the mechanical action exerted by the solidified walls P. .
From the other side, it can even be a drawback to perform the distortion in the lowermost zone, in the proximity of point L, where the walls P are already so near as to easily build up a few weldings and conse- ~.
quently a few pockets containing liquid material which, by solidification and consequent volume shrinking, would give rise to cavities inside the product, which drawback has preferably to be avoided.
Referring to Fig. 2, there is represented, in an ex~
tremely schematic way, an apparatus fit for carrying out the process according to the invention, as it is shortly decribed hereinbelow. The product l, contained in the ingot mold lO, descends, through the so called "foot rolls" ll along the roller train 13, defined by pairs of opposed sectors of roller cages 12, 14, 12', 14' and so on. The first sector, immediately after the foot rolls ll, where it is believed sufficient, in cer-~ ~ .
- 21170~3 ;;
tain cases, to limit the volume reducing distortion ac~
cordîng to the present invention, is usually called Se~e~rS
"segment zero". ~e~o~s 12, 12', 12'' and so on are all o~ t~
lying on the ~ of the curvilinear~s, namely Se~
they have a greater bending radius, whereas ~r~ 14, ~e~
14' and so on are defined ~s~ade~ segments. The rolls i~4~r of ,~c~t~r 12 are represented by the re~erence number se~ t 12a and the ones of ~e~ 14 by the reference number 14a and so on.
According to the instant invention and to the hypothe-. sis above, according to which the distortion according d~ ~r to the invention is determined by said first ~ ~r, the t~oJ portion 14 is made to be mobile with re~
spect to the ~L-l~$ 12 in whatsoever known way, there being provided means 16 for drawing cage 14 near the opposite cage 12, which remalns motionless. As it is reported on Fig. 2, the cage or bearing structure 14, comprising rolls 14a, is pivoted in 15 at one of its ends, preferably the superior one, and a hydraulic pi-ston 16 pushes the opposite end of the Z~GQ~ struc-~ ~J~
ture towards the motionless ~etra~eg 12. Of course, there can be provided whatsoever other solution of the problems, known to the skilled in the art; it is thus possible, for instance, to let the 14 slide along a skid device and to provide one or more hydraulic pistons for the thrust along the same skid device. In any case, an apparatus of this kind can be used when a square product or billet has to be conver-ted into a bloom or when an already rectangular pro-duct, like a bloom, has to be converted into an always rectangular however more flattened shape, for instance ~S~ 5~EE~
1 o - 1 7 0 8 3 a (thick) slab.
Should on the contrary a round product be converted, by means of distortion, into a product showing a square or rectangular cross-section, it is no more sufficient to work in the plane of Fig. 2, but a corresponding action has to be contemporaneously carried out in a plane nor-mal to the plane above, always containing the casting axis X-X, as it is recorded on the section view of Fig.
3. In this case the distortion of a round product 1 is contemporaneously caused by two pairs of rolls, lying in diametrically opposed positions of the perimeter of the same round product, namely rolls 12a and l~a of the opposite ~r~ and -~nt~9~ cages 12 and 14, recor-ded on Fig. 2, as well as rolls 22a and 24a, respecti-vely belonging to roll cages not reported in Fig. 2,having the opposite rolls oriented normally to the rolls 12a and 14a of cages 12 and 14.
Prefera~ly the subsequent rolls, downstream of the ones arranged in the sector undergoing distortion, are sup-plied with pistons fit for exerting a thrust towardsthe inside of the casting, no more for distortion pur-poses but for opposing the ferrostatic pressure and the possible consequent swelling, which can occur between the contact with a roll and the subsequent one, thus fitting to the size reached in the preceeding distor-tion phase.
EXAMPLE
From a continuous casting -ladle, having a round cross-section, it was cast, with a progression speed 3o V-2m/min., a round product (rod) having a diameter of 130 mm. Xn a zone between 28% and 76% of the concentra-5 ~ S ~ r~T
W093/~2 PCT/~2/00113 tion of the solid grains and by a metallurgical length equal (in this case) to 8 m, there was caused a distor-tion leading to a substantially square billet having a 100 mm side.
Subsequently the same rod was converted in another bil-let, having a similar size, however increasing the speed up to 3 m/min., and the distortion, according to the description above, was made to occur in a zone bet-ween the concentration values x equal to 14~ and 46%, whereas the metallurgical length was 12 m.
In both the cases there were sampled specimens of the cast product, once solidification was over, thus fin-ding, by macrographic analysis, the following results:
a) fine structure, without dendritic evidence;
b) structure isotropy, without any main orientation of the grains;
c3 absence of (kish) segregations, with homogeneity, in terms of chemical analysis, all along the cross-section; ~
20 d) isotropy of the mechanical features (tensile ;
strength, yield point, break elongation, impact strength);
e) better mechanical features, with respect to the pro-duct coming from a traditional casting, such as to al-low the reaching of the same end features of the end product with lower percentages of reduction in the xol-ling step.
From the above it is clear that the apparatus according to the instant invention allows the product, coming from the continuous casting and handled according to the process above, to be directly conveyed to a fini-W093/~02 PCT/~2/00113 shing rolling mill, by merely interposing a heati~g o-ven, optionally an induction oven, for adjusting the temperature according to the rolling values.
Optional additions and changes can be carried out by the skilled in the art, as to the process according to the instant invention hereinabove, as well as modifi-cations of the described and illustrated apparatus for carrying out such process, without exceeding the scope of the same invention.
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Claims (10)
1. A process for the manufacture of billets and blooms from a continuously cast steel showing high or excel-lent quality, comprising a liquid core distortion step for the casting product(s) characterized by, causing a reduction of the cross-section of the product(s), the Perimeter of said section being equal, in the route between the lowermost point in the casting axis (X-X) where superheated liquid is still present and the end (L) of the metallurgical length (lm) where the pro-duct(s) is completely solidified.
2. A process according to claim 1, wherein said liquid core distortion step is occurring in a zone of the con-tinuous casting route comprised between points corre-sponding to a concentration of the solid grains, insl-de the liquid core (M) respectively equal to 10% and to 80%.
3. A process according to claim 1 or 2, comprising the distortion of a round casting product (rod) to a square or rectangular product.
4. A process according to claim 1 or 2, comprising the distortion of a square casting product to a rectangular product.
5. A process according to claim 1 or 2, comprising the distortion of a rectangular casting product to another rectangular section having a ratio between the different sides farther from 1.
6. An apparatus for the continuous casting of steels, comprising a mould (10), foot rolls (11) and opposite segments of a curvilinear roller train (13) having a c???ing axis (x-x), respective-ly outer (12, 12'...) and inner (14, 14'...) segments, characterized in that at least one of said inner segments (16,16'...) between the lowermost point(s) on the casting axis (X-X) when superheated liquid is still present, and the end (-) of the metallurgical length (lm) where the steel product(s) is completely solidified, there being provided means (16) for bringing said at least one segment toward the opposite one.
7. An apparatus according to claim 6, wherein said mo-bile segment is the first inner segment (14) after the mould (10), pivoted in (15) at its uppermost end and connected, at its lowermost end, to the working piston of a hydraulic cylinder (16) which can be operated from outside.
8. An apparatus according to claim 6 or 7, also comprising roll cages (22, 24) fit for defining, bet-ween each other the same roller train (13) with rolls (22a, 24a) normal to the rolls (12a, 14a) of the seg-ments (12, 12', 14, 14'), wherein the cages correspon-ding to said mobile inner segments (14) are too ar-ranged in a mobile way, wherein there are provided means fit for pushing said cages (22, 24) and for brin-ging the same cages near to each other, normally to the movement direction of said mobile segment (14).
9. An apparatus according to claims 6-8, wherein the rolls (12'a, 12''a...; 14'a, 14''a...) of the segments of the roller train downstream of the mobile segment are each supplied with pistons fit for exerting a thrust towards the inside of the casting (1), for opposing the ferrostatic pressure of the same casting and thus for fitting to the size reached in the preceeding distor-tion step.
10. An apparatus according to whatsoever of the claims 6-9, directly connected to a a finishing rolling mill, there being merely interposed an oven optionally an in-duction oven, for bringing the temperature back to the values fit for the rolling step.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ITMI912414A IT1251308B (en) | 1991-09-12 | 1991-09-12 | Method and apparatus for production of continuous casting billets and blooms for high and very high-grade steels |
| IT91A002414 | 1991-09-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2117083A1 true CA2117083A1 (en) | 1993-03-18 |
Family
ID=11360649
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002117083A Abandoned CA2117083A1 (en) | 1991-09-12 | 1992-09-14 | A process and an apparatus for the manufacture of billets and blooms from a continuously cast steel showing high or excellent quality |
Country Status (5)
| Country | Link |
|---|---|
| AT (1) | ATE136240T1 (en) |
| CA (1) | CA2117083A1 (en) |
| ES (1) | ES2085648T3 (en) |
| HU (1) | HUT66806A (en) |
| WO (1) | WO1993004802A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5472041A (en) * | 1989-12-01 | 1995-12-05 | Cf&I Steel, L.P. | Railroad rail and method and system of rolling the same by conventional or continuous rolling process |
| DE4139242C3 (en) * | 1991-11-26 | 1999-08-19 | Mannesmann Ag | Process for the production of long steel products |
| DE19639299C2 (en) * | 1996-09-25 | 2001-02-22 | Sms Demag Ag | Device for producing a polygonal or profile format in a continuous caster |
| US8216985B2 (en) | 2007-04-27 | 2012-07-10 | Ntn Corporation | Grease composition and grease-enclosed bearing |
| RU2511130C2 (en) * | 2012-07-24 | 2014-04-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Липецкий государственный технический университет" (ЛГТУ) | Reduction of continuously cast shape billet in liquid-solid state |
| RU2694443C2 (en) * | 2017-12-20 | 2019-07-15 | Федеральное государственное автономное образовательное учреждение высшего образования "Уральский федеральный университет имени первого Президента России Б.Н. Ельцина" (УрФУ) | Method for production of thick sheet from continuously-cast slab |
| RU2681232C1 (en) * | 2018-05-24 | 2019-03-05 | Общество с ограниченной ответственностью "Инновационные металлургические технологии" (ООО "ИНМЕТ") | Method for continuous casting of a varietal billets and unit for its implementation |
| CN112191813A (en) * | 2020-10-13 | 2021-01-08 | 江苏省沙钢钢铁研究院有限公司 | Prediction method of bloom solidification end point |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT251213B (en) * | 1964-07-03 | 1966-12-27 | Boehler & Co Ag Geb | Process for the production of square or round strands |
| US5348075A (en) * | 1988-06-16 | 1994-09-20 | Davy (Distington) Limited | The manufacture of thin metal slab |
| FR2647377B1 (en) * | 1989-04-06 | 1993-04-30 | Techmetal Promotion | PROCESS AND INSTALLATION FOR CASTING THIN METAL PRODUCTS WITH REDUCTION OF THICKNESS UNDER THE LINGOTIERE |
-
1992
- 1992-09-14 CA CA002117083A patent/CA2117083A1/en not_active Abandoned
- 1992-09-14 ES ES92920674T patent/ES2085648T3/en not_active Expired - Lifetime
- 1992-09-14 HU HU9400680A patent/HUT66806A/en unknown
- 1992-09-14 WO PCT/IT1992/000113 patent/WO1993004802A1/en active IP Right Grant
- 1992-09-14 AT AT92920674T patent/ATE136240T1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| WO1993004802A1 (en) | 1993-03-18 |
| HU9400680D0 (en) | 1994-06-28 |
| ATE136240T1 (en) | 1996-04-15 |
| ES2085648T3 (en) | 1996-06-01 |
| HUT66806A (en) | 1995-01-30 |
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| Date | Code | Title | Description |
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| FZDE | Discontinued |