EP0378705B1 - PROCEDE DE FABRICATION DE TOLES MINCES EN ACIER INOXYDABLE Cr-Ni, DE QUALITE ET FINITION EXCELLENTES - Google Patents

PROCEDE DE FABRICATION DE TOLES MINCES EN ACIER INOXYDABLE Cr-Ni, DE QUALITE ET FINITION EXCELLENTES Download PDF

Info

Publication number
EP0378705B1
EP0378705B1 EP89908266A EP89908266A EP0378705B1 EP 0378705 B1 EP0378705 B1 EP 0378705B1 EP 89908266 A EP89908266 A EP 89908266A EP 89908266 A EP89908266 A EP 89908266A EP 0378705 B1 EP0378705 B1 EP 0378705B1
Authority
EP
European Patent Office
Prior art keywords
cast strip
cooling
solidification
sec
temperature
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.)
Expired - Lifetime
Application number
EP89908266A
Other languages
German (de)
English (en)
Other versions
EP0378705A4 (en
EP0378705A1 (fr
EP0378705B2 (fr
Inventor
Masanori Nippon Steel Corporation R&D Ueda
Shinichi Nippon Steel Corporation R&D Teraoka
Hidehiko Nippon Steel Corporation Sumitomo
Toshiyuki Nippon Steel Corporation Suehiro
Masayuki Nippon Steel Corporation R&D Abe
Shigeru Nippon Steel Corporation Minamino
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=27528474&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP0378705(B1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Priority claimed from JP63169095A external-priority patent/JPH0730405B2/ja
Priority claimed from JP22147188A external-priority patent/JPH0730406B2/ja
Priority claimed from JP63221472A external-priority patent/JPH0730407B2/ja
Priority claimed from PCT/JP1989/000692 external-priority patent/WO1990000454A1/fr
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Publication of EP0378705A1 publication Critical patent/EP0378705A1/fr
Publication of EP0378705A4 publication Critical patent/EP0378705A4/en
Publication of EP0378705B1 publication Critical patent/EP0378705B1/fr
Publication of EP0378705B2 publication Critical patent/EP0378705B2/fr
Application granted granted Critical
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys

Definitions

  • the present invention relates to a process for the production of a Cr-Ni type stainless steel sheet, by which the thickness of a cast strip is made almost the same as the product thickness by a synchronous continuous casting process in which the relative speed of the cast strip to the inner wall surface of a casting mold is the same.
  • it relates to a process by which the microstructure is made finer from the cast strip stage to form a Cr-Ni type stainless steel sheet having excellent surface properties.
  • JP-A-63-0421 provides an 18/8 CrNi stainless steel material having improved surface properties and material quality.
  • Said stainless steel sheet is produced by synchronous continuous casting to a thickness of ⁇ 10mm, cooled at a cooling rate of 200°C/s, hot rolled at 1030°C with 32% reduction ratio and coiled at 560°C. Subsequently the sheet is descaled and cold rolled.
  • a slab having a thickness of more than 100 mm is formed by casting while vibrating a casting mold in the casting direction, the obtained slab is surface-finished, the slab is heated at a temperature higher than 1000°C in a heating furnace, and the slab is hot-rolled by a hot strip mill comprising rows of rough rolling machines and finish rolling machines, to form a hot strip having a thickness of several mm.
  • an object of the present invention is to provide a continuous casting process for the production of a stainless steel cast strip having a thickness of less than 10 mm, in which an excellent cast strip capable of providing a product having excellent surface properties and quality can be prepared.
  • the object of the present invention is to provide a simple process capable of forming a Cr-Ni type stainless steel sheet which does not have an uneven gloss and a surface defect called a "roping phenomenon" inherently observed in stainless steel sheets prepared by the thin continuous casting apparatus.
  • the inventors succeeded in preventing the occurrence of roping on the surface of a product by making the austenite ( ⁇ ) grain size of a cast strip finer by controlling the cooling of the strip cast in a high temperature zone (zone of temperatures higher than 1100°C) and preventing the occurrence of an uneven gloss by controlling the cooling in a low temperature zone (zone of temperatures of 900 to 550°C).
  • the inventors engaged in further research and found that, if the above-mentioned ⁇ grain size is kept below 50 ⁇ m, a high degree of a prevention of roping can be attained and developed rapid cooling methods for a high-temperature cast strip, cold-rolling methods, and hot rolling methods as the means for the above-mentioned adjustment of the ⁇ grain size.
  • the present invention was completed based on the foregoing findings.
  • a molten steel comprising SUS 304 steel as the main component was cast by a twin-roll (twin-drum) continuous casting machine of the internal water-cooling type to form a cast strip having a thickness of 2 to 4 mm, and the cast strip was cooled and wound.
  • the obtained cast strip (thin band) was subjected to descaling, directly cold-rolled, finally annealed, and pickled to obtain a 2B product.
  • the surface properties of the obtained product were examined and compared with those of a conventional product obtained by heating a slab having a thickness larger than 100 mm, hot-rolling the ingot by a hot strip mill, and cold-rolling the hot-rolled strip.
  • the inventors examined the cause of this problem of the surface properties of the product in detail and, as a result found that, where the ⁇ grain size of the cast strip before cold-rolling is larger or cooling in the Cr carbide-precipitating temperature range is insufficient, the above-mentioned surface defects become prominent.
  • the composition of the molten steel comprises 0.01 to 0.08% of C, 0.25 to 1.50% of Si, 0.15 to 3.0% of Mn, 0.015 to 0.040% of P, 0.001 to 0.008% of S, 16.0 to 28.0% of Cr, 6.0 to 24.0% of Ni, 0.015 to 0.33% of N, 0.001 to 0.050% of Al, 0.01 to 3.0% of Mo, 0.01 to 2.0% of Cu, 0.01 to 0.60% of Ti, and 0.01 to 0.80% of Nb, with the balance being Fe and unavoidable impurities.
  • a molten steel having the above-mentioned composition is cast into a strip, that is, a cast strip having a thickness smaller than 10 mm, at a cooling speed of at least 100°C/sec by a twin-roll or single-roll continuous casting machine. If the thickness of the cast strip exceeds 10 mm, it becomes difficult to make the ⁇ grains finer, and to obtain the product by direct cold-rolling.
  • a method is adopted in which cooling of the cast strip is initiated at a temperature as high as possible just below the casting machine, to prevent reheating of the cast strip at the outlet of the continuous casting machine, and cooling is effected to 1100°C while maintaining the cooling rate in the ⁇ grain-growing temperature range at a level of at least 100°C/sec and as high as possible, whereby the grain growth of ⁇ is inhibited.
  • the ⁇ phase is crystallized at a temperature higher than 1450°C, just below the liquidus, and the ⁇ phase then grows.
  • Creq increases and is 19.5% or higher
  • solidification of the primary crystal is completed in the ⁇ phase, and precipitation of the ⁇ phase begins at about 1370°C as the result of solid phase reaction, and the ⁇ phase then grows.
  • the grain growth of ⁇ is greatly controlled, compared with the above-mentioned case where Creq is small. This can be understood from the fact that the grain growth of ⁇ is influenced by the high temperature range just after solidification.
  • Creq is an intermediate value
  • a peritectic reaction is added and the system becomes complicated, but in this case, a composition causing ⁇ solidification is advantageous to depress the grain growth of ⁇ .
  • the combination of selection of the composition retarding initiation of precipitation of ⁇ grains by utilizing ⁇ solidification and rapid cooling in the high temperature range is especially effective for controlling the grain growth of ⁇ and making ⁇ grains finer.
  • Figures 2(a), 2(b), and 2(c) are metallographic microscope photos of microstructures of cast strip obtained by casting compositions differing in ⁇ -Fe.cal (%) into 2-mm cast strip and cooling them.
  • ⁇ -Fe.cal (%) is -2.3%
  • ⁇ solidification is caused and ⁇ grains grow.
  • ⁇ -Fe.cal (%) is -1.1%
  • ⁇ ferrite is left and the size of ⁇ grains is reduced.
  • ⁇ -Fe.cal (%) is 3.0%, ⁇ solidification is apparently caused and the size of ⁇ grains is kept small. If ⁇ -Fe.cal (%) is larger, both of the sizes of ⁇ grains and ⁇ grains are kept small.
  • the combination of the above-mentioned cooling of the cast strip and selection of the composition in the Cr-Ni system has large influences on the reduction of the size of ⁇ grains, and it is very important to control ⁇ -Fe.cal (%) from -2 to 10%. If ⁇ -Fe.cal (%) exceeds 10%, the above-mentioned effect becomes saturated, and the ⁇ phase is left in the product and bad influences are imposed on the product quality.
  • the cast strip must be cooled in the temperature range of 900 to 550°C at an average cooling rate of at least 50°C/sec and wound at a temperature lower than 650°C. If this requirement is not satisfied, carbides are precipitated in the grain boundaries of the cast strip and intergranular corrosion is caused at the process of pickling the cast strip, resulting in degradation of the gloss of the final product.
  • the above-mentioned basic technique is very effective for making ⁇ grain finer, and to reduce the average grain size of ⁇ grains below 50 ⁇ m, and an addition of the following means is especially effective.
  • Figure 2(a), 2(b) and 2(c) are metallographical microscope photographs showing the microstructures of cast strips having a thickness of 2 mm, which are obtained by continuous casting of molten steels differing in ⁇ -Fe.cal (%).
  • Figure 3 is a diagram illustrating the relation between the strain load just below the melting point and occurrence of cracking in SUS 304 steel.
  • Figure 4 is a diagram illustrating the relation between the temperature of the cast strip and the time, observed when a cast strip of Cr-Ni type stainless steel is formed by a twin-roll continuous casting machine (off the water-cooling type).
  • Figure 5 is diagram illustrating influences of the thickness reduction ratio adopted when a cast strip obtained by carrying out casting at ⁇ -Fe.cal (%) of about 1% and then carrying out cooling is hot-rolled at 1100°C and the reduction adopted at the subsequent descaling cold-rolling on the roping height on the surface of the final product.
  • Figure 6 is a diagram illustrating the relation between the reduction adopted when preliminary cold-rolling (cold-working) of a cast strip (thin band) under application of a variable thickness reduction ratio is carried out in the process of the present invention, annealing is carried out at 1080°C for a short time to effect recrystallization, and cold-rolling (main cold-rolling) to the final product thickness is carried out, and the roping height on the surface of the final product.
  • the specific means for adjusting the average grain size of ⁇ of the cast strip below 50 ⁇ m, which are adapted in addition to the above-mentioned basic technique, will now be explained.
  • the cooling in order to reduce the size of ⁇ grains of the cast strip obtained by the twin-roll or single-roll continuous casting, the cooling must be started at a high temperature.
  • a method is advantageously adopted in which a roll of the internal cooling type is used and roll cooling is carried out at a certain reduction for example, a reduction lower than 5%.
  • a pair or a plurality of pairs of rolls for the roll cooling, it is possible to perform the cooling effectively while preventing reheating, and the cooling can be effected to 1200°C at an average cooling speed of at least 200°C/sec.
  • uniform cooling can be effectively accomplished by the combination of this roll cooling with gas cooling under a high pressure with air or nitrogen or mist cooling using a small amount of a liquid incorporated in such as gas.
  • these cooling methods can be adopted singly.
  • the as-cast strip is subjected to hot-processing to advance recrystallization and reduce the size of ⁇ grains.
  • the cast strip is rapidly cooled from the high-temperature range just below the casting machine to depress the grain growth of ⁇ in the cast strip, and then, hot-rolling is carried out to obtain finer ⁇ grains.
  • Figure 4 shows the temperature history of the cast strip formed by continuously casting a molten steel by the twin-roll method and winding the cast strip.
  • the cast strip is cast and is then air-cooled.
  • the cast strip is rapidly cooled by a casting drum in a casting machine, the cast strip is reheated after the outlet of the casing machine, and therefore, cooling is slower than in the case where cooling is started just below the drum and if the cast strip is directly wound, the grain growth of ⁇ is advanced during cooling after winding, with the result that problems concerning the surface properties, such as roping, sensitization by precipitation of Cr carbide, and uneven gloss arise.
  • hot-rolling is carried out after casting to cause recrystallization in the cast strip and make ⁇ grains finer, and after hot-rolling, sensitization by precipitation of Cr carbide is prevented by rapid cooling.
  • Figure 5 illustrates influences of the reduction on the roping height in the cold-rolled sheet, observed when a cooled cast strip having ⁇ -Fe.cal (%) adjusted to about 1% is hot-rolled at 1100°C.
  • the average grain size of the ⁇ grains is reduced below 50 ⁇ m.
  • Hot-rolling is carried out in the region where the surface temperature of the cast strip is higher than 900°C, and recrystallization in the center of the cast strip is promoted by this hot-rolling. Especially, it is sufficient if the cast strip is subjected to hot-rolling at a reduction of up to 60% while the interior of the cast strip is still in the high-temperature region (within 10 seconds after the casting). If the reduction exceeds 60%, the effect is saturated. If hot-rolling is started after the elapse of more than 10 seconds from the point of termination of the casting, the temperature difference between the surface layer portion of the cast strip and the interior of the cast strip becomes small and the effect of making ⁇ grains finer is reduced.
  • Annealing of the hot-rolled sheet is carried out at a temperature higher than 950°C to advance recrystallization. Especially, annealing is conducted while controlling the temperature and time so that the average grain size of ⁇ does not exceed 50 ⁇ m.
  • the amount of ⁇ -Fe is reduced as compared with the amount of ⁇ -Fe at the stage of the cast strip, and precipitation of Cr carbide in the ⁇ / ⁇ interface is delayed and hence, it is permissible to adopt a lower cooling rate than the cooling rate adopted for cooling the cast strip or hot-rolled sheet. Accordingly, the cooling rate after annealing is adjusted to at least 10°C/sec in the Cr carbide-precipitating region.
  • cooling of the cast strip obtained by the above-mentioned continuous casting machine of the twin-roll type is started just below the casting machine at a temperature as high as possible, and cooling to 1100°C is conducted at a cooling rate of at least 100°C/sec to inhibit the grain growth of ⁇ . Then, cooling is conducted at a cooling rate of at least 50°C/sec in the temperature range of 900 to 550°C and the cast strip is wound in the region of temperature lower than 650°C.
  • the obtained cast strip is subjected to preliminary cold-working such as cold-rolling, and then subjected to high-temperature short-time annealing to effect recrystallization in the cast strip.
  • Cast strips were subjected to preliminary cold rolling and then to short-time annealing at 1080°C, and cold-rolling (main cold-rolling) to the final sheet thickness was carried out.
  • the relationship between the reduction and the roping height in the product is shown in Fig. 6, relative to the reduction at the preliminary cold-rolling.
  • ⁇ grains of the cast strip are fine, when a cast strip having a thickness of, for example, 2 mm is prepared by continuous casting and cooling of the cast strip just below the casting machine in the temperature region of 1300 to 1100°C is carried out at such a high cooling rate as at least 100°C/sec, recrystallization is sufficiently advanced even if the reduction at the preliminary cold-rolling is at such a low level as at least 10%, and the average grain size of ⁇ can be reduced below 50 ⁇ m and the roping height in the product can be reduced.
  • ⁇ -Fe.cal (%) in the composition of the cast strip is adjusted from -2 to 10%, ⁇ grains can easily be made finer together with cooling in the high-temperature region.
  • the compositions of the stainless steels were as shown in Table 1, and ⁇ -Fe.cal (%) was changed in the range of from -3.6 to 7.8%.
  • cooling means for blowing high-pressure nitrogen gas was disposed, and cooling means including a roll of the internal cooling type was subsequently arranged.
  • the cast strips were cooled while preventing reheating.
  • mist cooling means was arranged after the roll-cooling means.
  • the average cooling rate to 1200°C was adjusted to 400 to 220°C/sec according to the thickness of the cast strip, that is, the casting rate.
  • water cooling was carried out in the temperature region of 900 to 550°C at a cooling rate of at least 50°C/sec, followed by winding.
  • the cast strips were hot-rolled in the temperature region of 1100 to 950°C within 8 seconds from the point of termination of casting.
  • the reduction at this hot-rolling was in the range of from about 10% to about 60% (Table 4).
  • the cast strips were cooled at a cooling rate of at least 60°C/sec in the temperature region of 900 to 550°C and the cast strips were wound at a temperature lower than 600°C.
  • the cast strips were subjected to pickling, descaling, cold-rolling, and ordinary annealing or bright annealing.
  • the compositions of the steels were as shown in Table 5. Air cooling and spray cooling were carried out just below the outlet of the twin-drum casting machine. Cooling to 1100°C was conducted at an average cooling rate of at least 100°C/sec, and water cooling was conducted in the temperature region of 900 to 550°C at an average cooling rate of at least 70°C/sec. Winding was then carried out at temperatures of 650 to 600°C.
  • the cast strips were descaled by mechanical descaling and pickling and were preliminarily rolled by cold-rolling. Both the cast strips having a thickness of 3 mm and the cast strips having a thickness of 4.5 mm were preliminarily cold-rolled at a reduction of 10 to 40%, annealed for less than 20 seconds at a temperature higher than 1000°C, and rapidly cooled. Thus, the cast strips were recrystallized and the grain size of ⁇ was controlled below 50 ⁇ m.
  • the cast strips were subjected to the main rolling at a reduction of 30, 50, 80, or 95% or a reduction higher than 95%, and final annealing was carried out according to customary procedures to obtain 2B and BA products. As shown in Table 6, these products were excellent in surface properties and mechanical properties.
  • molten steels having the same compositions as described above were cast according to the twin-drum method, and cooling to 1100°C was carried out at a cooling rate lower than 100°C/sec and cooling to 550°C was carried out at a cooling rate of 70°C/sec.
  • the cast strips were wound at a temperature of 650 to 600°C, descaled, and cold-rolled to obtain products. If the reduction at the cold-rolling was increased, the surface properties were improved, but fine roping was left on the surface and the effect of preventing roping was insufficient.
  • the present invention has the above-mentioned structure and exerts the above-mentioned functions, a simple process in which a thin band having a thickness close to the product thickness can be directly obtained by continuous casting can be provided, and a Cr-Ni type stainless steel sheet having excellent surface property and material quality can be obtained.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Continuous Casting (AREA)

Abstract

Procédé de fabrication d'une pièce coulée mince sous forme d'une tôle d'acier inoxydable Cr-Ni ayant sensiblement la même épaisseur que celle d'un produit final, par coulage en continu synchronisé, procédé comprenant: la trempe à haute température de la pièce immédiatement après coulage, la transformation à chaud ou à froid de ladite pièce, le recuit, etc. destinés à réduire la taille des grains gamma et le refroidissement à une température plus basse, égale ou inférieure à 900°C, afin d'empêcher la précipitation de carbure de chrome à la limite des grains. Ce procédé permet de réduire la tendance au vrillage ou l'irrégularité du brillant sur la surface de la tôle en acier inoxydable.

Claims (10)

  1. Procédé de production d'une tôle d'acier inoxydable de type Cr-Ni, présentant d'excellentes caractéristiques superficielles et une excellente qualité de matériau, qui consiste à couler en continu un acier inoxydable de type Cr-Ni, représenté par un acier 18 % Cr - 8 % Ni, pour obtenir une bande ayant une épaisseur inférieure à 10 mm, à une vitesse de refroidissement d'au moins 100°C/s à la solidification, par utilisation d'une machine de coulée continue dans laquelle la surface de paroi d'un moule de coulée se déplace d'une manière synchrone avec la bande coulée, constituée de δ-Fe.cal (%), défini par la formule δ-Fe.cal (%) = 3(Cr + 3/2Si + Mo + Nb + Ti) - 2,8 (Ni + 1/2Mn + 1/2Cu) - 84(C + N) - 19,8 (%)
    Figure imgb0023
    , une régulation étant effectuée de -2 à 10 % pour former un cristal primaire de la phase δ à la solidification, à abaisser la température d'amorçage de la cristallisation ou de précipitation des grains γ, et à ralentir la croissance des grains γ pendant et après la solidification, à déclencher un refroidissement de la bande coulée obtenue à une température aussi élevée que possible, à refroidir la bande coulée à 1100°C à une vitesse de refroidissement d'au moins 100°C/s tout en empêchant une rechauffe de la bande coulée, pour obtenir des grains γ plus fins, puis à refroidir la bande coulée sur un intervalle de température de 900 à 550°C, à une vitesse moyenne de refroidissement d'au moins 50°C/s, pour éviter une précipitation des carbures, et à transformer la bande coulée en une tôle laminée à froid, selon des techniques usuelles.
  2. Procédé selon la revendication 1, dans lequel la bande coulée obtenue est refroidie à 1200°C à une vitesse de refroidissement d'au moins 200°C/s pour affiner les grains γ, de façon que la grosseur moyenne des grains soit inférieure à 50 µm.
  3. Procédé selon la revendication 1 ou 2, dans lequel le refroidissement à 1200°C à une vitesse de refroidissement d'au moins 200°C/s est réalisé par au moins une paire de cylindres du type à refroidissement interne, de façon que la réduction de la bande coulée soit inférieure à 5 %.
  4. Procédé selon la revendication 1, 2 ou 3, dans lequel le refroidissement de la bande coulée, après solidification, est réalisé par utilisation d'un gaz et/ou d'un liquide.
  5. Procédé de production d'une tôle d'acier inoxydable de type Cr-Ni présentant d'excellentes caractéristiques superficielles et une excellente qualité de matériau, qui consiste à couler en continu un acier inoxydable de type Cr-Ni, représenté par un acier 18 % Cr-8 % Ni, pour obtenir une bande ayant une épaisseur inférieure à 10 mm, à une vitesse de refroidissement d'au moins 100°C/s à la solidification, par utilisation d'une machine de coulée continue dans laquelle la surface de paroi d'un moule de coulée se déplace d'une manière synchrone avec la bande coulée, à travailler à chaud la bande coulée sur la plage de température supérieure à 900°C, pour une réduction inférieure à 60 % après la solidification, pour faire progresser la recristallisation à l'intérieur de la bande coulée, et rendre les grains γ plus fins de façon que la grosseur moyenne des grains γ soit inférieure à 50 µm, puis à refroidir la bande coulée sur un intervalle de température de 900 à 550°C, à une vitesse moyenne de refroidissement d'au moins 50°C/s, pour éviter une précipitation des carbures, et à transformer la bande coulée en une tôle laminée à froid, selon des techniques usuelles.
  6. Procédé selon la revendication 5, dans lequel, au moment de la coulée, on ajuste le pourcentage de δ-Fe.cal de la bande coulée définie par la formule δ-Fe.cal (%) = 3(Cr + 3/2Si + Mo + Nb + Ti) - 2,8 (Ni + 1/2Mn + 1/2Cu) - 84(C + N) - 19,8 (%)
    Figure imgb0024
    , entre -2 à 10 %, pour former un cristal primaire de la phase δ à la solidification, on abaisse la température d'amorçage de la cristallisation ou de la transformation des grains γ, et on ralentit la croissance des grains γ pendant et après la solidification.
  7. Procédé de production d'une tôle d'acier inoxydable de type Cr-Ni présentant d'excellentes caractéristiques superficielles et une excellente qualité de matériau, qui consiste à couler en continu un acier inoxydable de type Cr-Ni, représenté par un acier 18 % Cr-8 % Ni, pour obtenir une bande ayant une épaisseur inférieure à 10 mm, à une vitesse de refroidissement d'au moins 100°C/s à la solidification, par utilisation d'une machine de coulée continue, dans laquelle la surface de paroi d'un moule de coulée se déplace d'une manière synchrone avec la bande coulée dans laquelle le pourcentage δ-Fe.cal (%), défini par la formule δ-Fe.cal (%) = 3(Cr + 3/2Si + Mo + Nb + Ti) - 2,8 (Ni + 1/2Mn + 1/2Cu) - 84(C + N) - 19,8 (%)
    Figure imgb0025
    , est ajusté entre -2 et 10 %, pour former un cristal primaire de la phase δ à la solidification, à abaisser la température d'amorçage de la cristallisation ou de la transformation des grains γ, et à ralentir la croissance des grains γ à partir du point intermédiaire de la solidification, à lancer le refroidissement de la bande coulée ainsi obtenue à une température aussi élevée que possible, tout en empêchant une rechauffe de la bande coulée après la solidification, à ajuster la vitesse moyenne de refroidissement à 1100°C à au moins 100°C/s telle que mesurée par rapport à la température superficielle de la bande coulée, pour ralentir la croissance des grains γ, à travailler à chaud la bande coulée à des températures supérieures à 900°C, pour une réduction inférieure à 60 %, dans les dix secondes qui suivent la fin de la coulée, instant où on est en présence d'une différence de température entre la portion superficielle de la bande coulée et le centre de la bande coulée, pour faire progresser la recristallisation au centre de la bande coulée et rendre les grains γ de la bande coulée plus fins de façon que la grosseur moyenne des grains γ soit inférieure à 50 µm, puis à refroidir la bande coulée sur un intervalle de température de 900 à 550°C, à une vitesse moyenne de refroidissement d'au moins 50°C/s, pour éviter une précipitation des carbures, et à transformer la bande coulée en une tôle laminée à froid, selon les techniques usuelles.
  8. Procédé selon la revendication 5, 6 ou 7, dans lequel, après que la bande coulée a été enroulée à des températures inférieures à 650°C, la tôle laminée à chaud est recuite à une température supérieure à 950°C pendant un laps de temps régulé, puis est refroidie à une vitesse de refroidissement d'au moins 10°C/s.
  9. Procédé de production d'une tôle d'acier inoxydable de type Cr-Ni présentant d'excellentes caractéristiques superficielles et une excellente qualité de matériau, qui consiste à couler en continu un acier inoxydable de type Cr-Ni, représenté par un acier 18 % Cr-8 % Ni, pour obtenir une bande ayant une épaisseur inférieure à 100 mm, à une vitesse de refroidissement d'au moins 100°C/s à la solidification, par utilisation d'une machine de coulée continue dans laquelle la surface de paroi d'un moule de coulée se déplace d'une manière synchrone avec la bande coulée, à amorcer le refroidissement de la bande coulée obtenue à une température aussi élevée que possible, à refroidir la bande coulée à 1100°C à une vitesse de refroidissement d'au moins 100°C/s tout en empêchant une rechauffe de la bande coulée, à ralentir la croissance des grains γ, puis à refroidir la bande coulée à une température de 900°C à 550°C à une vitesse de refroidissement d'au moins 50°C/s, à enrouler la bande coulée à une température inférieure à 650°C, à décaper la bande coulée sans recuit, à soumettre la bande coulée à un laminage à froid préliminaire, pour une réduction inférieure à 60 %, puis à recuire la bande coulée à une température supérieure à 850°C pour faire progresser la recristallisation et ajuster la grosseur moyenne des grains γ en dessous de 50 µm, à décaper la bande coulée, à laminer à froid la bande coulée jusqu'à l'épaisseur finale de la tôle produite, et à soumettre la tôle laminée à froid ainsi obtenue à un recuit final, et à un décapage ou à un recuit blanc.
  10. Procédé selon la revendication 9, dans lequel, au moment de la coulée, le pourcentage δ-Fe.cal (%) de la bande coulée, définie par la formule δ-Fe.cal (%) = 3(Cr + 3/2Si + Mo + Nb + Ti) - 2,8 (Ni + 1/2Mn + 1/2Cu) - 84(C + N) - 19,8 (%
    Figure imgb0026
    ), est ajusté entre -2 et 10 %, pour former un cristal primaire de la phase δ à la solidification, à abaisser la température d'amorçage de la cristallisation ou de la transformation des grains γ, et à ralentir la croissance des grains γ pendant et après la solidification.
EP89908266A 1988-07-08 1989-07-10 PROCEDE DE FABRICATION DE TOLES MINCES EN ACIER INOXYDABLE Cr-Ni, DE QUALITE ET FINITION EXCELLENTES Expired - Lifetime EP0378705B2 (fr)

Applications Claiming Priority (12)

Application Number Priority Date Filing Date Title
JP63169095A JPH0730405B2 (ja) 1988-07-08 1988-07-08 表面品質が優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JP16909688 1988-07-08
JP169095/88 1988-07-08
JP16909588 1988-07-08
JP16909488 1988-07-08
JP221472/88 1988-09-06
JP22147188 1988-09-06
JP221471/88 1988-09-06
JP22147288 1988-09-06
JP63221472A JPH0730407B2 (ja) 1988-07-08 1988-09-06 表面品質が優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JP22147188A JPH0730406B2 (ja) 1988-07-08 1988-09-06 表面品質と材質が優れたＣｒ−Ｎｉ系ステンレス薄鋼板の製造法
PCT/JP1989/000692 WO1990000454A1 (fr) 1988-07-08 1989-07-10 PROCEDE DE FABRICATION DE TOLES MINCES EN ACIER INOXYDABLE Cr-Ni, DE QUALITE ET FINITION EXCELLENTES

Publications (4)

Publication Number Publication Date
EP0378705A1 EP0378705A1 (fr) 1990-07-25
EP0378705A4 EP0378705A4 (en) 1991-09-04
EP0378705B1 true EP0378705B1 (fr) 1996-01-31
EP0378705B2 EP0378705B2 (fr) 1999-09-15

Family

ID=27528474

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89908266A Expired - Lifetime EP0378705B2 (fr) 1988-07-08 1989-07-10 PROCEDE DE FABRICATION DE TOLES MINCES EN ACIER INOXYDABLE Cr-Ni, DE QUALITE ET FINITION EXCELLENTES

Country Status (1)

Country Link
EP (1) EP0378705B2 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0463182A1 (fr) * 1990-01-17 1992-01-02 Nippon Steel Corporation PROCEDE POUR FABRIQUER DE LA TOLE EN ACIER INOXYDABLE Cr-Ni PRESENTANT UNE EXCELLENTE QUALITE DE SURFACE, ET MATERIAU AINSI OBTENU
EP0481481A1 (fr) * 1990-10-19 1992-04-22 Nippon Steel Corporation Procédé de production d'une bande mince coulée en acier inoxydable austénitique et bande ainsi obtenue
EP0530675A2 (fr) * 1991-08-28 1993-03-10 Nippon Steel Corporation Procédé pour la fabrication de tôles minces d'acier inoxydable à base de chrome-nickel ayant une qualité de surface et une aptitude au formage excellente
EP0679114A1 (fr) † 1993-11-18 1995-11-02 BHP STEEL (JLA) PTY. Ltd. Coulee d'une bande d'acier inoxydable sur une surface a rugosite predeterminee
WO1999006602A1 (fr) * 1997-08-01 1999-02-11 Acciai Speciali Terni S.P.A. Bandes d'acier inoxydable austenitique presentant une bonne soudabilite lors de leur moulage

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6026807B2 (ja) * 1981-03-18 1985-06-26 新日本製鐵株式会社 オ−ステナイト系ステンレス鋼の連続鋳造鋳片の処理法
JPS62124220A (ja) * 1985-07-17 1987-06-05 Nippon Steel Corp ステンレス厚鋼板の製造方法

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0463182A1 (fr) * 1990-01-17 1992-01-02 Nippon Steel Corporation PROCEDE POUR FABRIQUER DE LA TOLE EN ACIER INOXYDABLE Cr-Ni PRESENTANT UNE EXCELLENTE QUALITE DE SURFACE, ET MATERIAU AINSI OBTENU
EP0463182A4 (en) * 1990-01-17 1992-10-21 Nippon Steel Corporation Method of manufacturing cr-ni stainless steel sheet excellent in surface quality and material thereof
US5188681A (en) * 1990-01-17 1993-02-23 Nippon Steel Corporation Process for manufacturing thin strip or sheet of cr-ni-base stainless steel having excellent surface quality and material quality
EP0481481A1 (fr) * 1990-10-19 1992-04-22 Nippon Steel Corporation Procédé de production d'une bande mince coulée en acier inoxydable austénitique et bande ainsi obtenue
EP0530675A2 (fr) * 1991-08-28 1993-03-10 Nippon Steel Corporation Procédé pour la fabrication de tôles minces d'acier inoxydable à base de chrome-nickel ayant une qualité de surface et une aptitude au formage excellente
EP0679114A1 (fr) † 1993-11-18 1995-11-02 BHP STEEL (JLA) PTY. Ltd. Coulee d'une bande d'acier inoxydable sur une surface a rugosite predeterminee
WO1999006602A1 (fr) * 1997-08-01 1999-02-11 Acciai Speciali Terni S.P.A. Bandes d'acier inoxydable austenitique presentant une bonne soudabilite lors de leur moulage
AU724431B2 (en) * 1997-08-01 2000-09-21 Acciai Speciali Terni S.P.A. Austenitic stainless steel strips having good weldability as cast
US6568462B1 (en) 1997-08-01 2003-05-27 Acciai Speciali Terni S.P.A. Austenitic stainless steel strips having good weldability as cast

Also Published As

Publication number Publication date
EP0378705A4 (en) 1991-09-04
EP0378705A1 (fr) 1990-07-25
EP0378705B2 (fr) 1999-09-15

Similar Documents

Publication Publication Date Title
JP2011068997A (ja) 鉄−炭素−マンガン合金からなるストリップ
CN101148741A (zh) 一种薄带连铸奥氏体不锈钢带及其制造方法
EP0387785B1 (fr) Procédé de fabrication de tÔles et de rubans d'acier inoxydable austénitique laminés à froid
US5030296A (en) Process for production of Cr-Ni type stainless steel sheet having excellent surface properties and material quality
EP0378705B1 (fr) PROCEDE DE FABRICATION DE TOLES MINCES EN ACIER INOXYDABLE Cr-Ni, DE QUALITE ET FINITION EXCELLENTES
JPH03100124A (ja) 表面品質の優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JPH0730406B2 (ja) 表面品質と材質が優れたＣｒ−Ｎｉ系ステンレス薄鋼板の製造法
KR950005320B1 (ko) 표면품질과 가공성이 우수한 크롬-니켈계 스텐레스강 박판의 제조방법
EP0463182B1 (fr) PROCEDE POUR FABRIQUER DE LA TOLE EN ACIER INOXYDABLE Cr-Ni PRESENTANT UNE EXCELLENTE QUALITE DE SURFACE, ET MATERIAU AINSI OBTENU
JPH0565263B2 (fr)
KR930000089B1 (ko) 표면품질과 재질이 우수한 Cr-Ni계 스테인레스강 시이트의 제조방법
JPH0788534B2 (ja) 表面品質が優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JPH02133529A (ja) 表面品質が優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JP3222057B2 (ja) 表面品質と加工性の優れたＣｒ−Ｎｉ系ステンレス熱延鋼板および冷延鋼板の製造方法
JPH0730405B2 (ja) 表面品質が優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JPH0670253B2 (ja) 表面品質と材質が優れたＣｒ−Ｎｉ系ステンレス鋼薄板の製造方法
JP2768527B2 (ja) 加工性が優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JPH08176676A (ja) 表面品質の優れたＣｒ−Ｎｉ系ステンレス鋼薄板の製造方法
JP2607187B2 (ja) 表面品質と加工性の優れたＣｒ−Ｎｉ系ステンレス鋼薄板の製造方法
JPH0735551B2 (ja) 表面品質が優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JPH0796684B2 (ja) 表面品質が優れたＣｒ―Ｎｉ系ステンレス鋼薄板の製造方法
JPH0559446A (ja) 表面品質と加工性の優れたＣｒ−Ｎｉ系ステンレス鋼薄板の製造方法
JP2000256748A (ja) 耐リジング性に優れたフェライト系ステンレス鋼板の製造方法
JP2730802B2 (ja) 加工性の優れたＣｒ−Ｎｉ系ステンレス鋼薄板の製造方法
JPH04333347A (ja) 耐食性と加工性に優れるステンレス鋼薄鋳片の製造方法

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19900405

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE FR GB IT SE

A4 Supplementary search report drawn up and despatched

Effective date: 19910712

AK Designated contracting states

Kind code of ref document: A4

Designated state(s): DE FR GB IT SE

17Q First examination report despatched

Effective date: 19930618

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR GB IT SE

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: NIPPON STEEL CORPORATION

ITF It: translation for a ep patent filed

Owner name: JACOBACCI & PERANI S.P.A.

REF Corresponds to:

Ref document number: 68925578

Country of ref document: DE

Date of ref document: 19960314

ET Fr: translation filed
RAP2 Party data changed (patent owner data changed or rights of a patent transferred)

Owner name: NIPPON STEEL CORPORATION

PLBI Opposition filed

Free format text: ORIGINAL CODE: 0009260

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

26 Opposition filed

Opponent name: USINOR SACILOR DIRECTION DE LA PROPRIETE INDUSTRIE

Effective date: 19961031

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

PLAB Opposition data, opponent's data or that of the opponent's representative modified

Free format text: ORIGINAL CODE: 0009299OPPO

PLBF Reply of patent proprietor to notice(s) of opposition

Free format text: ORIGINAL CODE: EPIDOS OBSO

R26 Opposition filed (corrected)

Opponent name: USINOR SACILOR S.A.(92800 PUTEAUX) ATTN. DANIEL NE

Effective date: 19961031

PLAB Opposition data, opponent's data or that of the opponent's representative modified

Free format text: ORIGINAL CODE: 0009299OPPO

R26 Opposition filed (corrected)

Opponent name: USINOR S.A.

Effective date: 19961031

PLAW Interlocutory decision in opposition

Free format text: ORIGINAL CODE: EPIDOS IDOP

PLAW Interlocutory decision in opposition

Free format text: ORIGINAL CODE: EPIDOS IDOP

PUAH Patent maintained in amended form

Free format text: ORIGINAL CODE: 0009272

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: PATENT MAINTAINED AS AMENDED

27A Patent maintained in amended form

Effective date: 19990915

AK Designated contracting states

Kind code of ref document: B2

Designated state(s): DE FR GB IT SE

ITF It: translation for a ep patent filed

Owner name: JACOBACCI & PERANI S.P.A.

ET3 Fr: translation filed ** decision concerning opposition
REG Reference to a national code

Ref country code: GB

Ref legal event code: IF02

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20080717

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20080718

Year of fee payment: 20

Ref country code: IT

Payment date: 20080730

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20080716

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 20080709

Year of fee payment: 20

REG Reference to a national code

Ref country code: GB

Ref legal event code: PE20

Expiry date: 20090709

EUG Se: european patent has lapsed
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 20090709