EP0054867B1 - Verfahren zum Kühlen von Strängen beim Stranggiessen von Stahl - Google Patents

Verfahren zum Kühlen von Strängen beim Stranggiessen von Stahl Download PDF

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Publication number
EP0054867B1
EP0054867B1 EP81110372A EP81110372A EP0054867B1 EP 0054867 B1 EP0054867 B1 EP 0054867B1 EP 81110372 A EP81110372 A EP 81110372A EP 81110372 A EP81110372 A EP 81110372A EP 0054867 B1 EP0054867 B1 EP 0054867B1
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EP
European Patent Office
Prior art keywords
cooling
weight
stage
heat
steel
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
Application number
EP81110372A
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German (de)
English (en)
French (fr)
Other versions
EP0054867A1 (de
Inventor
Günter Dipl.-Ing. Rudolph
Karl Dr. Stercken
Eckehard Prof. Dr. Ing. Förster
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.)
Neue Hamburger Stahlwerke GmbH
Original Assignee
Neue Hamburger Stahlwerke GmbH
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Publication date
Application filed by Neue Hamburger Stahlwerke GmbH filed Critical Neue Hamburger Stahlwerke GmbH
Publication of EP0054867A1 publication Critical patent/EP0054867A1/de
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    • 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
    • B22D11/124—Accessories for subsequent treating or working cast stock in situ for cooling
    • B22D11/1246—Nozzles; Spray heads

Definitions

  • the invention relates to a method for cooling strands in the continuous casting of steel according to the preamble of claim 1.
  • a number of steel products e.g. B. high-carbon steel wires
  • the technological properties are noticeably deteriorated by segregation.
  • These segregations can also lead to the formation of brittle phases at the segregation points - often referred to as "martensite" - in the commonly used patenting of such wires from the rolling heat, which greatly reduce the tensile strength of the wire.
  • a globulitic structure is understood to mean a structure in which the crystals have no preferred direction of growth, but are randomly distributed over the cross section.
  • 1 shows the structure of a continuous casting billet with a large proportion of such a globulitic structure.
  • a dendritic structure is understood to mean a structure in which the predominant direction of growth of the crystals runs into the metal perpendicular to the strand surface.
  • Fig. 2 shows the micrograph of a continuous casting billet with a large proportion of dendritic structure.
  • One direction of development is to prevent the formation of a dendritic structure by stirring the liquid steel in the solidifying strand and thus to reduce segregation (see for example DE-C-1783 060).
  • the stirring effect is generally achieved by electromagnetic stirring devices. In any case, complex devices are required.
  • the cooling is controlled in such a way that the strand skin in the first cooling stage is of sufficient strength to withstand the metallostatic pressure - for this purpose, in the first stage a quantity of heat is generated with a cooling rate of around 82Wh / (Kg - min) of about 27.5 Wh / kg - but then in the second stage the cooling is reduced so much - at a cooling rate of 21 Wh / (kg - min) only a heat quantity of about 3.5 Wh / kg is removed - that the growth of the stem crystals in the transverse direction is impeded and the growth of the crystals with a vertical component is promoted in the core of the strand.
  • the invention has for its object to produce billets with reduced segregation in a continuous steel casting process for steels with a carbon content of 0.4 to 1.0% by weight, from which wire rod with improved mechanical and technological properties can preferably be produced.
  • the conditions for small-format continuous casting i. H. with dimensions up to 140 mm edge length, can be improved. It is also intended to prevent martensite from forming at the points of segregation when the wire rod rolled from a billet is tempered.
  • FIG. 4 schematically shows a continuous steel casting device for carrying out the method according to the invention.
  • Liquid steel is poured from a distributor trough 1 into an oscillating, cooled continuous casting mold 2, in which the outer skin solidifies during the slow downward movement of the metal strand.
  • Two cooling stages 3 and -4 are arranged behind the mold, in which the strand is uniformly sprayed with water over its entire circumference.
  • the liquid sump of the metal strand is denoted by 5, the solidified strand shell by 6.
  • the entire outflowing spray water is collected in a collecting line 7 and fed to a water tank 8.
  • the cooling stages 3 and 4 are supplied with spray water from the collecting container 8 by means of pumps 9 and 10 via lines 11 and 12.
  • the spray water collecting line 7 is a device 13 for detecting the temperature T A and the water volume flow V A of the wastewater and the stages 1 and 2 are devices 14 and 15 for detecting the water temperature, the water volume flow and the water pressure T j , V 1 , P 1 or T 2 , V 2 , P 2 assigned at the input of the relevant stages.
  • the division into the two stages is determined by measuring the water volume flow V A and the temperature T A of the waste water when the two stages 1 and 2 are in operation and once only when the stage 1 is in operation.
  • the strand below the mold is sprayed with water at a water pressure of Usually 3 bar, but a maximum of 8 bar, with a water volume of about 20-30 m 3 / h and strand.
  • the cooling is increased by increasing the heat transfer coefficient by intensifying the water cooling on the surface of the billets. This reduces the segregation.
  • stage 1 about 50 Wh / kg-90 Wh / kg, corresponding to a cooling rate of about 65 Wh / (kg. Min) - 100 Wh / (kg. Min) are withdrawn from the strand.
  • stage 2 - for a continuous caster with curved strand guide under the specified conditions is 20Wh / kg-40 Wh / kg, corresponding to a cooling rate of 30 Wh / (kg - min) -60 Wh / (kg - min).
  • the values for the amount of heat withdrawn are 20 Wh / kg-80 Wh / kg, i.e. slightly higher.
  • the amount of heat withdrawn (Wh) can be determined from the amount of water sprayed on and its temperature increase from the inlet to the outlet, ie V 1 ⁇ C W ⁇ (T 1 - T A ) for stage 1 and V 2 ⁇ C W ⁇ (T 2 - T A ) for level 2 , where C W means the specific heat of the water [1,163 Wh / (° C ⁇ kg water)]. That warmth quantity is to add a quantity of heat that is extracted by the evaporation of cooling water. The calculation is based on the fact that 3.5% of the sprayed water evaporates, 93 Wh / kg of water being required to heat the evaporated water from 20 ° C. to 100 ° C.
  • the heat of vaporization is 627 Wh / kg of water.
  • the strand is further heat quantities by radiation, free convection and heat conduction, for. B. on leadership roles, withdrawn. The last two parts are negligible in a billet caster.
  • the radiation component depends on the strand surface temperature and therefore decreases relatively and absolutely with increasing spray cooling intensity.
  • the strong cooling according to the invention it is approximately 6% of the total heat dissipation in the first stage and approximately 10% in the second stage, while it is 15 to 35% of the total heat dissipation in the case of conventional cooling.
  • the spray cooling is preferably carried out in a closed chamber.
  • the radiation portion of the heat dissipation is ultimately dissipated via the cooling water and is therefore included in the values determined from the amount of water and the increase in water temperature.
  • all that needs to be taken into account for the values determined via the removed cooling water is only the amount of heat removed by evaporation of the cooling water, which is generally between 3.0 and 4.0% of the amount of water sprayed on.
  • the cooling must be adapted so that the cooling rate in Wh / (kg - min) and the heat quantities dissipated in the two cooling stages remain approximately constant.
  • stage 2 can be extended and the amount of heat extracted in this stage can be increased.
  • the high amounts of heat withdrawn in the first stage of the secondary cooling zone are achieved by increasing the pressure and / or the amount of cooling water compared to the usual way of working.
  • a pre-pressure P 1 of the cooling water of 15-30 bar appears to be economically advantageous.
  • the structure of the continuous casting material produced in this way has a high proportion of dendritic structure, roughly corresponding to FIG. 2.
  • the edge zone of the billets produced in this way has - as Fig. 3 shows - an extremely fine-grained "globulitic" structure.
  • the thickness of the edge zone is at least 4 mm compared to usually 1 mm. This ensures that the billets are much more resistant to the formation of cracks under high stresses during rolling, since the dendritic structure, which is sensitive to tears at the grain boundary, does not reach as far to the surface.
  • the segregations in the wire rod are usually assessed according to a reference number from Bekaert.
  • the average value of the guide number for 5.5 mm wire in the named carbon range can be reduced from about 1.1 to 0.6 by the described procedure.
  • a wire rod can be produced from small-format continuous casting with low segregation, which can be deformed at high drawing speeds and which after drawing has high values in the so-called bending test and in the so-called torsion test, i.e. H. has good plastic and elastic behavior.
  • This wire rod can be tempered at high cooling rates from the rolling heat without the brittle phase called "martensite" forming at the segregation points.
  • the material is also less prone to cracking on the surface than normal continuous casting material due to the reinforced globulitic edge zone under high stresses during rolling.
  • a steel with 0.65% C, 0.27% Si, 0.68% Mn, 0.012% P, 0.013% S, 0.05% Cu, 0.02% Cr and 0.01% Mo was cast in a continuous casting .
  • the casting temperature in distributor 1 of the continuous casting installation was 1,530 ° C. and was thus 50 ° C. above the liquidus point.
  • the steel was cast in a continuous caster with a curved strand guide to form square strands with an edge length of 120 mm.
  • One strand of this plant was cooled in a secondary cooling zone with two stages 3 and 4.
  • the casting speed was 2.5 m / min.
  • the first stage 3 of increased cooling extended from the mold 2 in the casting direction of the strand over a length of 1.9 m, corresponding to a residence time of the strand of 46 seconds.
  • the strand was at a pre-pressure P 1 of 22 bar in front of the spray nozzles a water volume of 31 m 3 / h cooled.
  • P 1 pre-pressure
  • the admission pressure P 2 was 7 bar in front of the nozzle and the water quantity was 12 m 3 / h.
  • the heat transfer coefficient here was 800 W / (m 2 ⁇ K) to 900 W / (m 2. K), the cooling rate was 47 Wh / (kg. Min) and the amount of heat removed was 30 Wh / kg, with a radiation component of 2.8 Wh / kg, that is 9.4%.
  • the parallel runs in a first stage were cooled in a conventional manner with a water pressure of 3 bar and a water quantity of 14 m 3 / h per line.
  • This amount of water was applied in a secondary cooling zone with a residence time of also 46 seconds. This corresponds to a cooling rate of 50 Wh / (kg - min) or a dissipated amount of heat of 38 Wh / kg, with a radiation component of 9.7 Wh / kg, i.e. 25.5%.
  • the heat transfer coefficient was approx. 500 W / (m 2 ⁇ K) to 700 W / (m 2 ⁇ K).
  • the material was rolled out in a two-wire wire mill to 5.5 mm wire rod.
  • An examination of the wire rod in the micrograph and evaluation of the polish according to the standard series from Bekaert showed a value of 0.6 for the material cooled more according to the invention and an average of 1.4 for the material cooled in the usual way. While the wire from intensely cooled billets was free of "martensite", "martensite” was found on 12% of the wires from normally cooled billets.
  • the material produced according to the invention had a tensile strength of 1,050 N / mm 2 and was drawn to a diameter of 2.3 mm in a wire drawing plant using a 6-stage tractor.
  • the method according to the invention is particularly applicable to a steel having the composition mentioned in claims 9 and 10.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Heat Treatment Of Steel (AREA)
  • Metal Rolling (AREA)
EP81110372A 1980-12-23 1981-12-11 Verfahren zum Kühlen von Strängen beim Stranggiessen von Stahl Expired EP0054867B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3048711 1980-12-23
DE3048711A DE3048711C2 (de) 1980-12-23 1980-12-23 Verfahren zum Kühlen von Strängen beim Stranggießen von Stahlknüppeln

Publications (2)

Publication Number Publication Date
EP0054867A1 EP0054867A1 (de) 1982-06-30
EP0054867B1 true EP0054867B1 (de) 1985-03-13

Family

ID=6120096

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81110372A Expired EP0054867B1 (de) 1980-12-23 1981-12-11 Verfahren zum Kühlen von Strängen beim Stranggiessen von Stahl

Country Status (8)

Country Link
US (1) US4624298A (enrdf_load_stackoverflow)
EP (1) EP0054867B1 (enrdf_load_stackoverflow)
DE (1) DE3048711C2 (enrdf_load_stackoverflow)
FI (1) FI70161C (enrdf_load_stackoverflow)
IN (1) IN154905B (enrdf_load_stackoverflow)
MX (1) MX161280A (enrdf_load_stackoverflow)
WO (1) WO1982002160A1 (enrdf_load_stackoverflow)
ZA (1) ZA818652B (enrdf_load_stackoverflow)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU588650B2 (en) * 1985-12-09 1989-09-21 Alusuisse-Lonza Holding Ltd. Process and device for controlling the rate of cooling a continuously cast ingot
FR2631263B1 (fr) * 1988-05-13 1990-07-20 Siderurgie Fse Inst Rech Procede de refroidissement d'un produit metallique coule en continu
BE1003164A6 (fr) * 1989-04-13 1991-12-17 Centre Rech Metallurgique Procede et dispositif de refroidissement d'un produit metallique coule en continu.
LU87722A1 (fr) * 1990-04-11 1990-07-24 Centre Rech Metallurgique Procede et installation pour la coulee continue d'un metal
FR2677565B1 (fr) * 1991-06-14 1995-12-08 Vallourec Ind Procede d'augmentation de la production d'une ligne de coulee continue d'acier.
FR2767273B1 (fr) * 1997-08-14 1999-10-15 Vallourec Ind Procede de fabrication par coulee continue de produits en acier
WO2007013127A1 (ja) * 2005-07-25 2007-02-01 Mitsubishi Rayon Co., Ltd. ベルト式連続製板装置およびベルト式連続製板方法
US9745499B2 (en) * 2013-09-06 2017-08-29 Korea Advanced Institute Of Science And Technology Hexagonal boron nitride nanosheet/ceramic nanocomposite powder and producing method of the same, and hexagonal boron nitride nanosheet/ceramic nanocomposite materials and producing method of the same
CN106541098B (zh) * 2015-09-17 2018-08-03 鞍钢股份有限公司 一种减轻连铸坯中心缺陷的方法及装置

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE806376C (de) * 1949-06-11 1955-06-06 Ver Leichtmetallwerke Gmbh Verfahren zum Stranggiessen von Metallen, insbesondere von Stahl
US3512574A (en) * 1966-12-02 1970-05-19 Inland Steel Co Continuous casting process and apparatus
US3612151A (en) * 1969-02-14 1971-10-12 Kaiser Aluminium Chem Corp Control of continuous casting
US3693352A (en) * 1970-09-22 1972-09-26 Demag Ag Method and apparatus for cooling wide continuous metal castings, particularly steel castings
US3771584A (en) * 1971-01-08 1973-11-13 Roblin Industries Method for continuously casting steel billet strands to minimize the porosity and chemical segregation along the center line of the strand
DE2165944B1 (de) * 1971-12-30 1972-08-31 Mannesmann AG, 4000 Düsseldorf Verfahren und Vorrichtung zum Entfernen von Zunderansätzen in Stranggießanlagen
US3918467A (en) * 1972-01-21 1975-11-11 Siderurgie Fse Inst Rech Apparatus for the cooling of a continuously cast product
JPS5326730A (en) * 1976-08-25 1978-03-13 Nisshin Steel Co Ltd Method of continuously casting stainless steel slab

Also Published As

Publication number Publication date
US4624298A (en) 1986-11-25
FI70161C (fi) 1986-09-15
DE3048711C2 (de) 1991-08-01
FI70161B (fi) 1986-02-28
FI822821A0 (fi) 1982-08-13
DE3048711A1 (de) 1982-07-22
ZA818652B (en) 1982-11-24
MX161280A (es) 1990-08-28
WO1982002160A1 (en) 1982-07-08
FI822821L (fi) 1982-08-13
EP0054867A1 (de) 1982-06-30
IN154905B (enrdf_load_stackoverflow) 1984-12-22

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