EP1444371A1 - In-line process for the recrystallization of solidified coarse strips in carbon steel and in low-alloyed steel and so obtainable strips having a highly checked microstructure - Google Patents
In-line process for the recrystallization of solidified coarse strips in carbon steel and in low-alloyed steel and so obtainable strips having a highly checked microstructureInfo
- Publication number
- EP1444371A1 EP1444371A1 EP02793320A EP02793320A EP1444371A1 EP 1444371 A1 EP1444371 A1 EP 1444371A1 EP 02793320 A EP02793320 A EP 02793320A EP 02793320 A EP02793320 A EP 02793320A EP 1444371 A1 EP1444371 A1 EP 1444371A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- strips
- strip
- low
- carbon steel
- making
- 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 55
- 239000010959 steel Substances 0.000 title claims abstract description 55
- 238000001953 recrystallisation Methods 0.000 title claims abstract description 44
- 238000000034 method Methods 0.000 title claims abstract description 40
- 230000008569 process Effects 0.000 title claims abstract description 38
- 229910000975 Carbon steel Inorganic materials 0.000 title claims abstract description 30
- 239000010962 carbon steel Substances 0.000 title claims abstract description 30
- 238000001816 cooling Methods 0.000 claims abstract description 63
- 238000005096 rolling process Methods 0.000 claims abstract description 45
- 238000010438 heat treatment Methods 0.000 claims abstract description 34
- 238000009749 continuous casting Methods 0.000 claims abstract description 14
- 238000005266 casting Methods 0.000 claims abstract description 11
- 239000000203 mixture Substances 0.000 claims abstract description 9
- 229910001566 austenite Inorganic materials 0.000 claims description 21
- 230000009467 reduction Effects 0.000 claims description 16
- 230000009466 transformation Effects 0.000 claims description 8
- 239000011261 inert gas Substances 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 238000005246 galvanizing Methods 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 230000001590 oxidative effect Effects 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims description 2
- 238000009413 insulation Methods 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- 238000011282 treatment Methods 0.000 abstract description 13
- 238000000137 annealing Methods 0.000 abstract description 11
- 238000007670 refining Methods 0.000 abstract description 8
- 239000000463 material Substances 0.000 abstract description 6
- 230000001939 inductive effect Effects 0.000 abstract 1
- 229910000859 α-Fe Inorganic materials 0.000 description 21
- 238000004458 analytical method Methods 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 9
- 229910001562 pearlite Inorganic materials 0.000 description 8
- 239000000126 substance Substances 0.000 description 6
- 238000007669 thermal treatment Methods 0.000 description 6
- 229910001563 bainite Inorganic materials 0.000 description 5
- 238000005098 hot rolling Methods 0.000 description 5
- 229910000734 martensite Inorganic materials 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 150000001247 metal acetylides Chemical class 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 230000000930 thermomechanical effect Effects 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 229910001568 polygonal ferrite Inorganic materials 0.000 description 2
- 238000010008 shearing Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 229910001208 Crucible steel Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
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- 238000011161 development Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
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- 238000011144 upstream manufacturing Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
- C21D8/0215—Rapid solidification; Thin strip casting
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
Definitions
- the present invention applies to both Carbon and low-alloyed steel strips, made by direct continuous casting with a twin-roll or single-roll and strip machine, all characterized by the generation of large-size grains (from 150 to 1500 ⁇ m) in the solidified coarse product.
- the invention refers to an in-line controlled recrystallization treatment carried out on a solidified coarse strip during its roll path transfer, prior to its wrapping on a coiler.
- a rolling and an annealing rapid heating with holding at preset temperatures for short times
- Both the rolling and the annealing can be carried out under conditions in which the austenite or the ferrite are stable, or in a mixed-phase field, in which both the austenite and the ferrite are stable.
- This invention refers to a process for the making of steel strips and sheets, having a thickness ranging from 4.5 to 0.7 mm, corresponding to common- or special-type hot-rolled or cold-rolled and annealed products, using as starting material continuous casting coarse strips and the present in-line recrystallization process.
- Several processes for improving the mechanical properties of continuously cast strips via the homogenizing and the refining of the primitive austenitic grains by thermomechanical treatments have already been advanced and patented.
- EP 0707908 Al teaches a twin-roll continuous casting apparatus with which a Carbon steel strip is cast under an atmosphere of inert gas, like Ar or N 2 .
- the strip is then subjected in-line to hot rolling(from 850 to 1350 °C) with a thickness reduction ranging from 5 to 50% and cooled.
- the thin flat product thus obtained has good strength and ductility properties by virtue of the grain size reduction attained by hot rolling.
- JP 61689846 and JP 63115654 refer to in-line thermal treatments, without hot rolling, comprising at least a double phase transition prior to the final cooling and wrapping. Said phase transition is effected subjecting the strip to single or multiple heat cycles of the type: cooling, heating, cooling.
- WO 95/13155 teaches an in-line thermal treatment of cast Carbon steel strip aimed at checking the microstructure of the as- cast strip.
- the cast strip after an optional single-pass thickness reduction (20-50%) at 900-1100 °C, is cooled below the temperature at which the transformation of austenite into ferrite takes place, and subsequently heated in- furnace at ⁇ 1200°C temperatures until reaustenizing the material (in-line normalization).
- the austenitic grains are thus refined, and, by checking the strip final cooling and wrapping, sufficiently refined structures providing adequate strength and ductility can be developed.
- EP 0776984 reports a method and the related equipment for continuously manufacturing metal coils, from a continuous casting system of strips, comprising also the steps of: hot deformation, with a >30% thickness reduction; in- furnace heating thermal treatment under non-oxidizing atmosphere at temperatures of 800-1250 °C (preferably of 1100-1250 °C); cooling, at a 20-40 °C/s rate and down to 100 °C; pickling; and strip wrapping/shearing.
- the main object of this invention is the connection between the main casting line and the strip pickling-edge trimming- end thermal treatment line, so as to carry out a single continuous step according to which the pickling, the edge trimming, the strip wrapping/shearing lines may independently be connected to the strip casting-rolling-thermal treatment line.
- the sole example reported relates to a stainless steel, although the metals usable in the invention comprise common and special steels.
- EP 0760397 (Nippon Steel) discloses an apparatus for stainless steelmaking realizing a process comprising the steps of: casting, cooling, hot deformation (rolling) at various temperatures, complete recrystallization by heating and cooling.
- Some of the above processes and other alike ones require the introduction of one or more optional cooling systems and of a rolling stand, as well as of a intermediate reheat furnace, located upstream or downstream of the rolling stand onto the roll path transferring the strip to the coiler.
- Most of the preceding experiences with Carbon steel and low-alloyed steel relate to in-line thermal or thermomechanical treatments exploiting sequential phase transformations of the austenite-ferrite-austenite type to attain, prior to the cooling preceding the strip wrapping, a homogenizing and a refining of the austenitic structure, so as to make it as similar as possible to that of a conventionally hot-rolled strip.
- the state of the art provides no teachings about the attainment of a Carbon steel or low-alloyed steel product that, from a continuously cast solidified coarse strip, develop the desired mechanical and technological properties, related to hot-rolled or cold-rolled and annealed strips and sheets, exploiting a controlled in-line recrystallization treatment, by rolling in a ferritic, austenitic or mixed-phase field, and direct annealing, also in a subcritical field ( ⁇ Ac 3 in-furnace treatment temperature).
- in-line recrystallization refers to high-alloyed (stainless) steels that always recrystallize at a very slow rate, as much so as to systematically require treatment temperatures of well above 1050 °C in order to attain a significant recrystallization over short times.
- An object of the present invention is that of providing an in-line process for the making of strips in Carbon steel and in low-alloyed steel by a controlled recrystallization treatment performed on a solidified coarse strip during the roll path transfer, prior to the wrapping on the coiler.
- a rolling there are carried out in-line and in rapid succession a rolling, an annealing (rapid heating with holding at preset temperatures for short times in order to attain a near-complete recrystallization of the austenite and/or of the ferrite work hardened during the deformation), and a controlled cooling (optional direct galvanizing included) prior to the wrapping on the coiler.
- annealing rapid heating with holding at preset temperatures for short times in order to attain a near-complete recrystallization of the austenite and/or of the ferrite work hardened during the deformation
- a controlled cooling optionally direct galvanizing included
- this novel process comprises the following steps:
- Ar 3 being the transformation start temperature of the continuously cooled austenite
- ⁇ holding the strip at a controlled temperature in an insulated system (F) comprised between an outlet of the rolling system (E) and an inlet in a heating system (G);
- Another object of the present invention is to provide strips of Carbon steel and of low-alloyed steel, manufactured with the hereto detailed process, having an end thickness ranging from 4.5 to 0.7 mm and preset microstructure characteristics, capable of developing the following properties, suitable for various application fields:
- ⁇ Structural employ (e.g., guard-rail, car components, containers, etc.).
- FIG. 1 is a simplified scheme of the continuous casting machine for thin strips and of the devices for the in-line recrystallization and the highly controlled cooling of the strips, used for the present invention
- FIG. 2 is a scheme of the in-line recrystallization and of the cooling cycles applied to cast coarse strips;
- FIGGS. 3 and 4 show strip microstructures, as detectable by optical microscope.
- the process of the present invention provides the use of a continuous casting machine having a twin-roll or a single-roll/belt ingot mold (A), all characterized by the formation of large-size grains (150 to 1500 ⁇ m) in the solidified coarse product.
- cooling devices (B and D) for cooling in a controlled manner the strip continuously crossing them, guided by the pinch rolls (C) of a per se already known construction.
- the strip is subjected to an adequate force, e.g. acting on the twin rolls, so as to limit the generation of shrinkage cavities.
- the cast strip is subjected on both faces thereof to cooling in order to slow down the growth both of the austenitic grains and of the surface oxide layer.
- the cooling cycles of the as-cast steel strips are set acting on the casting rate, the flow rates and the number of active cooling areas (modules).
- the pair of said cooling systems B and D has modules, individually actuable, variable in the individual sections and capable of effecting onto the strip cooling rates ofup to 200 °C/s.
- cooling is attained with cooling modes selected from the group comprising: natural air, forced air, inert gas jets in an inertized chamber, air-water, water and combinations thereof.
- a rolling system consisting of one or more stands (E), capable, in one or more passes, of effecting a 15-80% total thickness reduction in order to reduce to acceptable sizes the residual porosities due to the solid contraction and to induce a work hardening of the structure extant at the instant of deformation.
- the stands are located as close as possible, so as to attain quite short interpass times (shorter than the time required to attain the 50% b/v recrystallization) and to allow deformation accumulation in the material (the greater the accumulated deformation, the more rapid the material recrystallization and the softening kinetics).
- the hot deformation of the cast strip can take place by means of two consecutive stands, each providing a 15-40%) thickness reduction.
- a rapid heating system (R) aimed at controlling the temperature of the strip inletted in the rolling system (E), according to the steel composition and to the thermomechanical cycle to be carried out.
- the rapid heating system (R) is located downstream of the controlled cooling system (D).
- a further system comprising a tunnel insulated under natural air, or inert gas, or combinations thereof, and aimed at holding the temperature of the strip which is about to enter the furnace (G) located nearby E.
- the insulated section prevents temperature from dropping below Ar 3 and to start a phase transformation before the austenite recrystallization.
- the furnace (G), of an induction-, gas- or the like type, is capable of operating under a reducing or a non-oxidizing atmosphere, and of rapidly (in less than 12 s) bringing the strip temperature to temperature values ranging from 670 to 1150 °C, apt to attain a near-complete recrystallization of the material (>95 % b/v) with temperature holding times of 5-40 s.
- the annealing temperature is selected so as to fall within a completely austenitic field (austenitic field rolling) or a ferritic field (ferritic field rolling) , or within a mixed-phase field in which ferrite and austenite coexist (ferritic or mixed-phase field rolling), as it is indicated in FIG. 2.
- the cleaning system (H) which removes oxides or oxide residues partially or totally reduced by the furnace atmosphere from the strip surface.
- a set of at least three controlled cooling modules (I, L, M). These modules are capable of effecting on the strip cooling rates variable in the individual sections and ranging from 800 °C/s (ultrarapid cooling) to 0.01 °C/s (insulation), and.
- the strip cooling cycle Upon detecting the strip temperature at the furnace outlet by metering with a suitable device, the strip cooling cycle is defined according to the steel phase transformation characteristics, which mainly depend on the actual size of the austenitic grains and on the chemical analysis of the steel, so as to develop the desired structures.
- the various modules Onto the roll path, among the various modules, there are located other temperature meters (e.g., pyrometers), enabling monitoring of the thermal cycle.
- the latter can be quite complex (e.g., accelerated cooling, in-air cooling, wrapping) in case multiphase microstructures, made of various constituents like polygonal ferrite, bainite, martensite and/or residual austenite, are to be developed.
- One of the cooling modules is also capable of galvanizing the strip.
- the strip is wrapped at a temperature of from 900 to 150°C.
- Various laboratory and full-scale plant tests were conducted, employing steels whose composition in percentage by mass was defined in the following field: 0.02-0.20 C; 0.1-1.6 Mn; 0.02-2.00 Si; ⁇ 0.05 Al; ⁇ 0.03 S; ⁇ 0.1 P; 0.01-1.5 Cr; 0.01- 0.5 Ni; ⁇ 0.5 Mo; 0.003-0.012 N; and, optionally, ⁇ 0.03 Ti; ⁇ 0.10 V; O.035 Nb; O.005 B, with substantially Fe q.s. to 100.
- the end result is a certain, yet nonhomogeneous, refining of the structure.
- e) The grains located near the surfaces of the cast and rolled coarse strip are often thinner than those at midthickness, due to the dishomogeneity of thickness deformation and of temperature gradients in the in-line rolling.
- the austenitic grains are equiaxic and uniform, with mean sizes ranging from 50 to 120 ⁇ m, according to the deformation accumulated in rolling and at the annealing temperatures adopted. These austenitic grains, after the checked cooling, generate ferritic grains having 15-30 ⁇ m sizes, in case of >10 °C/s cooling rates and of wrappings at >700 °C temperatures. In the latter case, also pearlite islands are observable whose volume fraction relates to the Carbon content in the steel.
- the in-line recrystallization allows, by homogenizing the austenitic structure and the strip temperatures lengthwise as well as widthwise, to reduce the variety of structures, polygonal, acicular and otherwise unavoidable, entailing advantages of reproducibility of the mechanical characteristics, in particular for the direct- employ products, replacing the traditional cold-annealed strips.
- the rolling of the cast coarse strip in the case of low-Carbon strips (C ⁇ 0.06 %), may be carried out without the problem of excessive rolling forces even in the ferritic field, i.e. at temperatures ranging from Ari to Ari - 100 °C.
- the present innovative in-line recrystallization treatment of cast coarse strips enables, by selecting the chemical analysis of the steel, to check the rolling and annealing temperatures and the in-line cooling cycles, to develop suitable end microstructures, having definite volume fractions of equiaxic (polygonal) ferrite, pearlite or carbides, of acicular and/or bainitic ferrite and of high-Carbon martensite/residual austenite islands.
- the different distribution of the microstructural components so obtained, highly checkable through the thermal and microstructural homogenization taking place during the in-furnace recrystallization treatment provides the strips with different combinations of strength, ductility and cold formability.
- the latter are characterized by having, at the ferrite interface, a high dislocation density with respect to the traditional polygonal ferrite/pearlite structures.
- the end material yielded has a continuous-type stress-deformation curve, provided with a good mix of strength and ductility. Exploiting a subcritical recrystallization treatment in continuously cast strips, microstructures exhibiting significant quantities of residual austenite (5-20 %) were made.
- EXAMPLE 1 An 1.6 mm thickness strip was made according to the process of the present invention and using steel A, the analysis of the latter being reported in Table 1.
- the molten steel was cast in a vertical continuous casting machine (Fig. 1) having a twin-roll ingot mold and a 6 t/m mean separation force.
- the strips were cooled at the ingot mold outlet until reaching a 1080-1100 °C temperature at the rolling system inlet. A 35% total thickness reduction was effected.
- the subsequent cooling and heating steps were carried out as it is schematically shown in FIG 2, so as to attain a > 850 °C minimum temperature Tm, a 10 °C/s heating rate, a 1050 °C maximum temperature of the in-furnace strip, with 10 s holding times thereat. 15 °C/s cooling rates were detected at the furnace outlet and up to the wrapping. The latter was carried out at >750 °C temperatures.
- microstructural characteristics and the mechanical properties of the end strip in terms of mean size (d) of the ferrite grains, pearlite (P) %, lowest yield value (RerJ, failure strength (Rm), Re L /R ratio, ultimate elongation (A), are reported in Table 2.
- the ratio between the standard deviation and the mean value for the failure strength and for the elongation is of the 2.5% and of the 3%, respectively.
- FIG. 3 shows the typical microstructure of the strip, as observable at the optical microscope.
- the molten steel was cast in a vertical continuous casting machine having a twin-roll ingot mold and a 5.5 t/m mean separation force.
- the strips were cooled at the ingot mold outlet until reaching a 1080-1100 °C temperature at the rolling system inlet. A 35% total thickness reduction was effected.
- the subsequent cooling and heating steps were carried out as it is schematically shown in FIG. 2, so as to attain a >850 °C minimum temperature Tm, an 8 °C/s heating rate, a 1050 °C maximum temperature of the in-furnace strip, with 12 s holding times thereat. 15 °C/s cooling rates were detected at the furnace outlet and up to the wrapping. The latter was carried out at >750 °C temperatures.
- microstructural characteristics and the mechanical properties of the end strip in terms of mean size (d) of the ferrite grains, pearlite % (P) lowest yield value (Re L ), failure strength (Rm), ReiTRm ratio, ultimate elongation (A), are reported in Table 4.
- the ratio between the standard deviation and the mean value for the failure strength is of the 3% and of the 3.5%, respectively.
- FIG. 4 shows the typical microstructure of the strip, as observable at the optical microscope.
- EXAMPLE 3 An 1.6 mm thickness strip was made, according to the process of the present invention and using steel B. The analysis of the latter is reported in Table 1.
- the molten steel was cast in a vertical continuous casting machine having a twin-roll ingot mold and a 6 t/m mean separation force. The strips were cooled at the ingot mold outlet until reaching a 690 °C temperature at the rolling system inlet. A 37% total thickness reduction was effected.
- the subsequent cooling and heating steps were carried out as it is schematically shown in FIG. 2, so as to attain a >670 °C minimum temperature Tm 670 °C, a 5 °C/s heating rate, a 720 °C maximum temperature of the in-furnace strip, with 15 s holding times thereat.
- the molten steel was cast in a vertical continuous casting machine having a twin-roll ingot mold and a 6.5 t/m mean separation force.
- the strips were cooled at the ingot mold outlet and then heated until reaching an 840-860 °C temperature at the rolling system inlet. A 40% total thickness reduction was effected.
- the subsequent cooling and heating steps were carried out as it is schematically shown in FIG. 2, so as to attain a >880 °C minimum temperature Tm, an 8 °C/s heating rate, a 1050 °C maximum temperature of the in-furnace strip, with 12 s holding times thereat. Downstream of the furnace the cooling rates were of from 50 °C/s to 700-680 °C/s, 5 s natural air cooling, ⁇ 400 °C forced cooling (40-80 °C/s). Wrapping at 400-380 °C temperatures
- the elevated yield value (Rpo .2 ) and failure strength value Rm are anyhow accompanied by a low yield/failure ratio, a good ductility (>22% elongation), and a particularly high (> 16000 MPa%) product of the elongation X failure strength (A X Rm) parameter.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Metal Rolling (AREA)
- Continuous Casting (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IT2001RM000678A ITRM20010678A1 (en) | 2001-11-15 | 2001-11-15 | PROCEDURE FOR THE ONLINE RECRYSTALLIZATION OF RAW SOLIDIFICATION TAPES IN CARBON STEEL AND IN ALLOY AND BONDED STEEL |
ITRM20010678 | 2001-11-15 | ||
PCT/IT2002/000728 WO2003062476A1 (en) | 2001-11-15 | 2002-11-15 | In-line process for the recrystallization of solidified coarse strips in carbon steel and in low-alloyed steel and so obtainable strips having a highly checked microstructure |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1444371A1 true EP1444371A1 (en) | 2004-08-11 |
EP1444371B1 EP1444371B1 (en) | 2005-04-13 |
Family
ID=11455880
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP02793320A Expired - Lifetime EP1444371B1 (en) | 2001-11-15 | 2002-11-15 | In-line process for the recrystallization of solidified coarse strips in carbon steel and in low-alloyed steel |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP1444371B1 (en) |
CN (1) | CN1296498C (en) |
AT (1) | ATE293174T1 (en) |
DE (1) | DE60203733T2 (en) |
IT (1) | ITRM20010678A1 (en) |
WO (1) | WO2003062476A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3234497A4 (en) * | 2014-12-16 | 2018-08-29 | Greer Steel Company | Steel compositions, methods of manufacture and uses in producing rimfire cartridges |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102005063058B3 (en) * | 2005-12-29 | 2007-05-24 | Thyssenkrupp Nirosta Gmbh | Producing cold rolled strip of ferritic stainless steel comprises controlled cooling before cold rolling |
CN103305770B (en) * | 2012-03-14 | 2015-12-09 | 宝山钢铁股份有限公司 | A kind of manufacture method of thin strap continuous casting 550MPa level high-strength air corrosion-resistant steel band |
CN103305754B (en) * | 2012-03-14 | 2015-09-23 | 宝山钢铁股份有限公司 | A kind of age hardening thin strap continuous casting low-carbon microalloy steel band manufacture method |
CN103305759B (en) * | 2012-03-14 | 2014-10-29 | 宝山钢铁股份有限公司 | Thin strip continuous casting 700MPa grade high-strength weather-resistant steel manufacturing method |
CN103302255B (en) * | 2012-03-14 | 2015-10-28 | 宝山钢铁股份有限公司 | A kind of thin strap continuous casting 700MPa level high-strength air corrosion-resistant steel manufacture method |
ES2851199T3 (en) * | 2013-07-03 | 2021-09-03 | Outokumpu Nirosta Gmbh | Procedure for coating flat steel products with a metallic protective layer |
JP6452037B2 (en) * | 2014-02-04 | 2019-01-16 | 日立金属株式会社 | Casting method and casting apparatus |
CN112517863A (en) * | 2019-09-19 | 2021-03-19 | 宝山钢铁股份有限公司 | High-strength thin-specification patterned steel plate/belt and manufacturing method thereof |
CN114669613B (en) * | 2022-04-19 | 2023-06-20 | 安徽工业大学 | Flexible roller contact type Bao Daizu cooling method |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
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JP3276151B2 (en) * | 1994-04-04 | 2002-04-22 | 新日本製鐵株式会社 | Twin roll continuous casting method |
JP2750096B2 (en) * | 1995-05-08 | 1998-05-13 | 新日本製鐵株式会社 | Strip continuous casting hot rolling heat treatment pickling equipment and method for producing pickling coil |
JP3709003B2 (en) * | 1996-01-26 | 2005-10-19 | 新日本製鐵株式会社 | Thin plate continuous casting method |
DZ2531A1 (en) * | 1997-12-19 | 2003-02-08 | Exxon Production Research Co | Process for the preparation of a double phase steel sheet, this sheet and process for strengthening the resistance to crack propagation. |
-
2001
- 2001-11-15 IT IT2001RM000678A patent/ITRM20010678A1/en unknown
-
2002
- 2002-11-15 EP EP02793320A patent/EP1444371B1/en not_active Expired - Lifetime
- 2002-11-15 WO PCT/IT2002/000728 patent/WO2003062476A1/en not_active Application Discontinuation
- 2002-11-15 DE DE60203733T patent/DE60203733T2/en not_active Expired - Fee Related
- 2002-11-15 CN CNB02825466XA patent/CN1296498C/en not_active Expired - Fee Related
- 2002-11-15 AT AT02793320T patent/ATE293174T1/en not_active IP Right Cessation
Non-Patent Citations (1)
Title |
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See references of WO03062476A1 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3234497A4 (en) * | 2014-12-16 | 2018-08-29 | Greer Steel Company | Steel compositions, methods of manufacture and uses in producing rimfire cartridges |
US11905569B2 (en) | 2014-12-16 | 2024-02-20 | Greer Steel Company | Steel compositions, methods of manufacture and uses in producing rimfire cartridges |
Also Published As
Publication number | Publication date |
---|---|
CN1296498C (en) | 2007-01-24 |
ITRM20010678A1 (en) | 2003-05-15 |
ATE293174T1 (en) | 2005-04-15 |
DE60203733D1 (en) | 2005-05-19 |
CN1606629A (en) | 2005-04-13 |
EP1444371B1 (en) | 2005-04-13 |
ITRM20010678A0 (en) | 2001-11-15 |
DE60203733T2 (en) | 2006-02-09 |
WO2003062476A1 (en) | 2003-07-31 |
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