EP1399598B1 - Method for producing high-strength cold-formed steel products from a hot rolled strip, said products exhibiting good malleability - Google Patents

Method for producing high-strength cold-formed steel products from a hot rolled strip, said products exhibiting good malleability Download PDF

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Publication number
EP1399598B1
EP1399598B1 EP02738172A EP02738172A EP1399598B1 EP 1399598 B1 EP1399598 B1 EP 1399598B1 EP 02738172 A EP02738172 A EP 02738172A EP 02738172 A EP02738172 A EP 02738172A EP 1399598 B1 EP1399598 B1 EP 1399598B1
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EP
European Patent Office
Prior art keywords
cold
hot
product
temperature
strip
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EP02738172A
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German (de)
French (fr)
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EP1399598B2 (en
EP1399598A1 (en
Inventor
Thomas Heller
Bernhard Engl
Günter STICH
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ThyssenKrupp Steel Europe AG
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ThyssenKrupp Stahl AG
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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
    • C21D8/0221—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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold 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
    • 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

Definitions

  • the invention relates to a method for producing a high-strength, cold-formed from a hot strip Steel product with good formability.
  • a method of making high strength having hot strip is from DE 197 10 125 A1 known.
  • This formability can be according to the Process known from DE 197 10 125 A1 be increased that the hot strip after coiling annealing in the temperature range from 500 ° C to 850 ° C is subjected.
  • the advantages for components offers, overall still high strength, before all yield strength, with good formability have to.
  • you can particularly high strengths with extraordinary low yield strength ratios or equivalent high strengthening with good elongation values achieved become.
  • this is suitable annealed hot strip for cold rolling, in which a Degree of deformation of at least 30% is reached.
  • cold-formed strip then at temperatures Continuously annealed from 700 ° C to 900 ° C a cold-formed sheet product of high Strength, further improved yield strength ratio and good hardening behavior.
  • the object of the invention was a method to create a cold formed product, that with increased strength in the cold-formed state high elasticity and accordingly good Formability.
  • the invention is based on the surprising Finding that the strength-increasing Properties of the steels according to the invention microalloying elements contained in the inventive Generation of the hot strip by annealing the from the Hot strip obtained after coiling by cold working Activate the product and get cold formed Products with particularly high strengths and one too Produce good formability in the cold-formed state leave without a procedural costly remuneration would be required.
  • crash-relevant components such as Bumpers, side impact beams, reinforcement elements, available to the full extent in the event of a Collision with other objects on a large scale to be able to convert kinetic energy into forming energy.
  • the method according to the invention is also suitable especially for the production of components, their dimensions and Dimensional requirements are just as high as to their strength in use.
  • a typical example for such an application provide frames for screens that are in picture tubes of televisions or Computer monitors the shadow mask due to the Thermal stress during their assembly and their Operation under uniform tension in a fixed defined level.
  • the required high The so cold-formed component then receives strength in the According to the invention after the cold working performed heat treatment, so the result is a precisely shaped, high-strength component with high Yield strength is available.
  • An additional Remuneration leading to the delay of the component and a The surface can then be impaired not necessary anymore.
  • the operating parameters including the reel temperature can be selected that by the presence of a sufficient amount of microalloying elements possible per se Hardness increase in the course of reeling is not achieved, but that the microalloy elements after reeling are present in the undissolved, dissolved state. Out for this reason the reel temperature is according to the invention always chosen so that they are at a clear distance is below the temperature at which the Elimination maximum of the microalloying elements reached would.
  • the steel alloy used according to the invention comprises Steel compositions that make up depending on the respective composition and production conditions Dual phase steels, bainitic steels or Have complex phase steels manufactured. To be aimed for basically steels with a fine grain multiphase structure in which bainite, ferrite, and martensite Residual austenite depending on the type of steel dependent scope are included.
  • the hot rolling start temperature is like this chosen that the microalloying elements largely stay loosened in the steel so that they can last for the Effected step of the method according to the invention Effects are available.
  • the Rolling temperature for this purpose at least 1050 ° C be.
  • thin slab or Thin strip casting process with which it is due to the Circumstance that the need for reheating of the primary material or a solution of Microalloying elements do not exist and on the other hand the cooling speeds of the strand are high can, particularly safely, is possible Microalloying elements until the beginning of the To keep the hot rolling process largely solved.
  • the hot rolling end temperature should preferably be in the austenite region, that is to say above the Ar 3 temperature, in order to obtain the fine-grained, multi-phase structure sought after according to the invention.
  • composition of the structure of the hot strip obtained is obtained by chemical Properties, the warm-up, rolling and cooling conditions as well as the reel temperatures. It has shown that the effect achieved according to the invention increase in strength and formability Sets dual-phase steels particularly safely when the reel temperature is a maximum of 300 ° C. For steels with a predominantly bainitic structure, this effect safely reached at reel temperatures of up to 350 ° C 450 ° C. Complex phase steels should be preferred can be coiled at temperatures from 450 ° C to 550 ° C.
  • steels of the type used in accordance with the invention have a high strength of at least 550 N / mm 2 .
  • the steels harden very strongly.
  • the elongation decreases significantly, so that a product that is high-strength but difficult to deform is obtained.
  • cold-formed components of this type have only a small forming reserve and a correspondingly reduced energy absorption capacity. As such, for example, they are only suitable to a limited extent for the production of components which are to be used as bumpers in crash-prone areas of an automobile.
  • Typical annealing temperatures during the Cold deformation of the following glow is in the range of 450 ° C to 700 ° C, preferably in the range of 550 ° C to 650 ° C.
  • Annealing time and annealing temperature are in the limited frame interchangeable. That is, at high temperatures are only short holding times required and vice versa. Accordingly, the Heat treatment as carried out separately Treatment step in a hood or in a Continuous annealing.
  • One in a conventional way in conditions leading to a complete Recrystallization would result in annealing treatment would nullify the effect achieved by the invention do.
  • the annealing step in a heat treatment that is from the hot strip cold-formed product in the course of its further processing is subjected anyway.
  • this step it can be for example a galvanizing or another Process for coating or passivation of the Act on the surface of the cold-formed product in the range provided for the annealing treatment Temperatures is carried out.
  • the degrees of deformation achieved in the course of cold forming amount to at least 2% until the limit shape change, whereby yourself through the procedure according to the invention effects achieved especially if the Degree of cold deformation 5% to 20%, in particular 5% to 10%.
  • the cold deformation can be, for example, as Roll profiling, drawing, pressing or Hydroforming can be performed. On Cold rolling at relatively low Degrees of deformation are also suitable for this.
  • the micro-alloying element comes in accordance with the invention Steel at least one of the elements Ti, Nb and / or V for use. Of course, these items can combined in amounts to be triggered that caused at the end of the method according to the invention Elimination process are sufficient. Especially however, the use of Ti, which is preferred through a particularly favorable excretion behavior distinguished. If Ti is preferred Embodiment of the invention as the only one Microalloying element used, so should its content be at least 3.4 times the N content, in order a sufficient solution potential of the Ensure microalloying element. Preferably lies the Ti content of the steel for this purpose in the range 0.07, to 0.15 wt%, while the nitrogen content is preferably less than 0.007% by weight. With Ti contents on this scale the formation of Fine deposits with a hardening effect are optimal supported.
  • the Al content is preferably in the range from 0.015 to 0.08% by weight. or 0.5 to 1.5% by weight.
  • Steel sheets produced according to the invention are suitable preferred for cold forming into components on their Strength with good elongation behavior and accordingly good deformation behavior as well as high high dimensional accuracy are. They are characterized by sheets according to the invention produced components by low weight and high Energy absorption capacity.
  • Steel sheets produced according to the invention is the production of frames for flat screens.
  • Steel sheets manufactured according to the invention for vehicle bodies or attachments produce the one hand particularly firm and on the other hand, for example, in the event of a collision with another vehicle the on impact kinetic energies in deformation energy need to convert.
  • These include Side members, so-called “Crash boxes”, chassis parts, hollow structure parts and Reinforcing parts such as the A, B or C pillar of the Automobile body.
  • Hot strip produced according to the invention is basically for Suitable for galvanizing. However, one is relative low temperature, especially piecewise, hot-dip galvanizing is preferable, Galvanizing at temperatures above 750 ° C are less suitable because the with regard to the effect achieved according to the invention critical temperatures in the processed Workpiece can be exceeded.
  • a steel composed according to Table 1 was cast on a continuous casting plant to a pre-slab, which was then hot-rolled as a starting material at a temperature of 1125 ° C. in a hot strip mill to a hot strip.
  • the hot rolling end temperature was 925 ° C.
  • the reel temperature was 475 ° C.
  • the hot strip is pickled and delivered to a cold rolling mill in the pickled state.
  • the plates of group G1 are closed None for comparison purposes following the cold deformation Annealing has been carried out while the sheets of Group G2 at 500 ° C, the sheets of group G3 at 550 ° C, the plates of group G4 at 600 ° C and the Sheet of group G5 at 650 ° C in a hood furnace for annealed for one hour each and then on Air have been cooled.
  • the strength values obtained are significantly improved in comparison with the only cold-formed and not heat-treated sheets G1.1-G1.5.
  • a uniform expansion A gl is achieved by the heat treatment carried out after the cold working, which corresponds approximately to the uniform expansion A gl of the non-cold-formed and non-heat-treated sheet Gl1.0. Accordingly, the cold-formed and subsequently heat-treated steels produced according to the invention have particularly good formability and an equally good energy absorption capacity.
  • Table 3 shows a second example of a steel composition used according to the invention.
  • a correspondingly alloyed steel was melted and cast into slabs.
  • the slabs were then reheated to a temperature of more than 1150 ° C. and hot-rolled with a hot rolling temperature of at least 850 ° C.
  • the tape sample T3.2 clearly shows that high-strength in the procedure according to the invention let cold-formed sheet metal products are obtained which, like a Comparison of the ductility values shows, regarding their Formability superior to the undeformed tape sample T3.0 are.
  • An example of a particularly advantageous use of a steel produced according to the invention consists in the Manufacture of frames in which the shadow masks of TV tubes are held. To blacken the one Such a tight shadow mask will Frame with the shadow mask for a sufficient time exposed to a temperature that is typically approx. Is 570 ° C.
  • the hot strip is deformable by cold working and then in the course of the blackening of him held shadow mask for a sufficient time the temperature required for blackening the strength of the frame increases to.
  • the process consists in the production of galvanized Side impact beams or other crash-relevant Components for vehicle bodies.
  • This will start with the respective from hot strip produced according to the invention Component, for example, through a deep-drawing operation cold formed.
  • the cold-formed component is then at Temperatures in the range of 470 ° C for galvanizing subjected.
  • Component also kept at a temperature level, in which the increase achieved according to the invention Elasticity and strength sets.
  • the so obtained Side impact beam exhibits due to its good Elasticity and high strength at the same time particularly high energy absorption capacity which it does in the event of a collision with another Vehicle a large part of the free convert kinetic energy into deformation energy and the space necessary for the survival of the occupants can secure.

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

Abstract

The invention relates to a method for producing a high-strength cold-formed product from a hot-rolled strip, said product exhibiting good malleability. According to said method, a steel comprising (in wt.%): C: 0.01 0.25 %, Si: 0.01 1.50 %, Mn: 0.50 2.00 %, P: <= 0.08 %, S: <= 0.01 %, Al: 0.001 1.50 %, Cr: <= 0.60 %, Mo: <= 0.60 %, N: < 0.02 %, at least one micro-alloy element from the group Ti: <= 0.20 %, Nb: <= 0.06 %, V: <= 0.15 %, the remainder being iron and the usual impurities is cast to form an input stock such as slabs, thin slabs or a cast strip. Starting from an initial hot-roll temperature, at which the micro-alloy elements remain essentially dissolved, the input stock is hot-rolled to form a hot-rolled strip. Said strip is firstly wound at a winding temperature of less than 600 DEG C and then cold formed into a product at a cold formation degree which is not less than 2 % and not greater than the deformation limit. The cold-formed product is annealed at a temperature and for a period which are less those required for complete recrystallization. The inventive method enables a cold formed product to be produced, said product exhibiting high strength, malleability and plasticity in the cold formed state.

Description

Die Erfindung betrifft ein Verfahren zum Herstellen eines hochfesten, aus einem Warmband kaltverformten Stahlprodukts mit guter Umformbarkeit.The invention relates to a method for producing a high-strength, cold-formed from a hot strip Steel product with good formability.

Ein Verfahren zum Herstellen von eine hohe Festigkeit aufweisendem Warmband ist aus der DE 197 10 125 A1 bekannt. Gemäß dem bekannten Verfahren wird ein (in Gew.-%) 0,1 - 0,2 % C, 0,3 bis 0,6 % Si, 1,5 bis 2,0 % Mn, ≤ 0,08 % P, 0,3 bis 0,8 % Cr, ≤ 0,4 % Mo, ≤ 0,2 % Ti, ≤ 0,08 % Nb und als Rest Eisen sowie unvermeidbare Verunreinigungen enthaltender Complexphasenstahl erschmolzen, zu Brammen abgegossen und anschließend zu Warmband ausgewalzt, wobei die Warmwalzendtemperatur oberhalb von 800 °C liegt. Anschließend wird das erhaltene Warmband bei einer Abkühlgeschwindigkeit von mindestens 30 °C/s abgekühlt und dann bei einer Haspeltemperatur von höchstens 600 °C gehaspelt. Bei so erhaltenem Warmband beträgt die Festigkeit aufgrund der relativ niedrigen Haspeltemperatur mindestens 900 MPa. Darüber hinaus besitzt das nach dem bekannten Verfahren erzeugte Warmband eine gute Kaltumformbarkeit.A method of making high strength having hot strip is from DE 197 10 125 A1 known. According to the known method, a (in % By weight) 0.1 - 0.2% C, 0.3 to 0.6% Si, 1.5 to 2.0% Mn, ≤ 0.08% P, 0.3 to 0.8% Cr, ≤ 0.4% Mo, ≤ 0.2% Ti, ≤ 0.08% Nb and the rest iron and unavoidable Complex phase steel containing impurities melted, poured into slabs and then to Rolled hot strip, the final hot rolling temperature is above 800 ° C. Then that will hot strip obtained at a cooling rate of cooled at least 30 ° C / s and then at a Reel temperature of maximum 600 ° C coiled. With so obtained hot strip is the strength due to relatively low reel temperature at least 900 MPa. In addition, it has the known method hot strip produces good cold formability.

Diese Umformbarkeit kann gemäß dem aus der DE 197 10 125 A1 bekannten Verfahren dadurch noch gesteigert werden, dass das Warmband nach dem Haspeln einer Glühung im Temperaturbereich von 500 °C bis 850 °C unterzogen wird. Durch diese Glühung wird ein Werkstoffzustand erreicht, der Vorteile für Bauteile bietet, die insgesamt noch eine hohe Festigkeit, vor allem Streckgrenze, bei guter Umformbarkeit besitzen müssen. Durch die Wahl höherer Glühtemperaturen können dabei besonders hohe Festigkeiten bei außerordentlich niedrigen Streckgrenzenverhältnissen oder gleichbedeutend hoher Verfestigung bei guten Dehnungswerten erreicht werden.This formability can be according to the Process known from DE 197 10 125 A1 be increased that the hot strip after coiling annealing in the temperature range from 500 ° C to 850 ° C is subjected. Through this annealing a Material condition reached, the advantages for components offers, overall still high strength, before all yield strength, with good formability have to. By choosing higher annealing temperatures you can particularly high strengths with extraordinary low yield strength ratios or equivalent high strengthening with good elongation values achieved become.

Gemäß der DE 197 10 125 A1 eignet sich das derart glühbehandelte Warmband zum Kaltwalzen, bei dem ein Umformgrad von mindestens 30 % erreicht wird. Indem das derart kaltverformte Band anschließend bei Temperaturen von 700 °C bis 900 °C rekristallisierend durchlaufgeglüht wird, kann ein kaltverformtes Blechprodukt von hoher Festigkeit, weiter verbessertem Streckgrenzenverhältnis und gutem Verfestigungsverhalten erzeugt werden.According to DE 197 10 125 A1, this is suitable annealed hot strip for cold rolling, in which a Degree of deformation of at least 30% is reached. By doing that such cold-formed strip then at temperatures Continuously annealed from 700 ° C to 900 ° C a cold-formed sheet product of high Strength, further improved yield strength ratio and good hardening behavior.

Allerdings zeigt sich, dass das Dehnungsverhalten der gemäß den bekannten Verfahren durch Kaltverformung erzeugten Produkte für viele Anwendungsfälle nicht ausreicht. So ist es beispielsweise schwer, mit aus einem solchen Stahl hergestellten Bauteilen, die zum Schutz der Insassen eines Fahrzeugs im Fall eines Unfalls eingesetzt werden sollen, die an derartige Teile hinsichtlich der Festigkeit einerseits und des Energieaufnahmevermögens andererseits gestellten Anforderungen zu erfüllen. Die nach dem bekannten Verfahren erzeugten Bauteile besitzen nach der Kaltverformung auch dann nicht die notwendige Verformbarkeit. Wenn sie nach der Kaltverformung einer rekristallisierenden Glühung unterzogen werden, nimmt zwar die Umformbarkeit zu, die Festigkeit ist dann allerdings nicht mehr ausreichend.However, it shows that the elongation behavior of the according to the known methods by cold working produced products for many applications sufficient. For example, it is difficult with one such steel manufactured components that protect the Occupants of a vehicle used in the event of an accident should be to such parts in terms of Strength on the one hand and the energy absorption capacity on the other hand, to meet the requirements. The have components produced by the known method after the cold working even then not the necessary one Deformability. If after the cold forming of a undergo recrystallizing annealing Although the formability is too, the strength is then however no longer sufficient.

Die Aufgabe der Erfindung bestand darin, ein Verfahren zum Herstellen eines kaltverformten Produkts zu schaffen, das bei erhöhter Festigkeit im kaltverformten Zustand eine hohe Dehnbarkeit und eine dementsprechend gute Umformbarkeit besitzt.The object of the invention was a method to create a cold formed product, that with increased strength in the cold-formed state high elasticity and accordingly good Formability.

Ausgehend von dem voranstehend erläuterten Stand der Technik wird diese Aufgabe durch ein Verfahren zum Herstellen eines hochfesten, aus einem Warmband kaltverformten Produkts mit guter Dehnbarkeit gelöst, bei dem ein Stahl mit (in Gewichts-%) 0,01 - 0,25 % C, 0,01 - 1,50 % Si, 0,50 - 2,00 % Mn, ≤ 0,08 % P, ≤ 0,01 % S, 0,001 - 1,50 % A1, ≤ 0,60 % Cr, ≤ 0,60 % Mo, < 0,02 % Mo, sowie mindestens einem Mikrolegierungselement aus der Gruppe Ti, Nb, V, wobei der Gehalt an Ti ≤ 0,20 %, der Gehalt an Nb ≤ 0,06 % und der Gehalt an V ≤ 0,15 % ist, Rest Eisen und übliche Verunreinigungen, zu einem Vormaterial, wie Brammen, Dünnbrammen oder gegossenes Band, vergossen wird, bei dem das Vormaterial ausgehend von einer Warmwalzanfangstemperatur, bei der die Mikrolegierungselemente im wesentlichen gelöst bleiben, zu Warmband warmgewalzt wird, bei dem das Warmband bei einer weniger als 600 °C betragenden Haspeltemperatur gehaspelt wird, bei dem das Warmband anschließend bei einem mindestens 2 % betragenden und höchstens der Grenzformänderung entsprechenden Kaltverformungsgrad zu einem Produkt kaltverformt wird, und bei dem das durch Kaltverformung erzeugte Produkt bei Temperaturen und Zeiten, die unterhalb der zur vollständigen Rekristallisation erforderlichen Temperaturen und Zeiten liegen, geglüht wird.Based on the status of the Technology accomplishes this task through a process for Making a high strength, from a hot strip cold deformed product with good elasticity, at a steel with (in% by weight) 0.01 - 0.25% C, 0.01 - 1.50% Si, 0.50 - 2.00% Mn, ≤ 0.08% P, ≤ 0.01% S, 0.001 - 1.50% A1, ≤ 0.60% Cr, ≤ 0.60% Mo, <0.02% Mo, as well at least one microalloying element from the group Ti, Nb, V, where the content of Ti ≤ 0.20%, the content of Nb ≤ 0.06% and the content of V ≤ 0.15%, balance iron and common impurities, to a material such as Slabs, thin slabs or cast tape, cast is, in which the starting material from a Hot rolling start temperature at which the Microalloying elements remain essentially detached, is hot rolled to hot strip, in which the hot strip at a reel temperature of less than 600 ° C is coiled, in which the hot strip is then at a minimum of 2% and a maximum of Limit shape change corresponding to the degree of cold deformation a product is cold worked, and in which the Cold deformation produced product at temperatures and Times below to complete Recrystallization required temperatures and times lie, is annealed.

Die Erfindung basiert auf der überraschenden Feststellung, dass sich die festigkeitssteigernden Eigenschaften der in erfindungsgemäßen Stählen enthaltenen Mikrolegierungselemente bei erfindungsgemäßer Erzeugung des Warmbandes durch eine Glühung des aus dem Warmband nach dem Haspeln durch Kaltverformung erhaltenen Produktes aktivieren und sich dabei kaltverformte Produkte mit besonders hohen Festigkeiten und einem auch im kaltverformten Zustand guten Umformvermögen herstellen lassen, ohne dass dazu eine verfahrenstechnisch aufwendige Vergütung erforderlich wäre.The invention is based on the surprising Finding that the strength-increasing Properties of the steels according to the invention microalloying elements contained in the inventive Generation of the hot strip by annealing the from the Hot strip obtained after coiling by cold working Activate the product and get cold formed Products with particularly high strengths and one too Produce good formability in the cold-formed state leave without a procedural costly remuneration would be required.

Durch die erfindungsgemäß nach der Kaltverformung durchgeführte Wärmebehandlung wird der mit der Kaltverformung regelmäßig einhergehende Verlust an Verformungsfähigkeit ohne Festigkeitseinbußen ausgeglichen. Dies gilt beispielsweise auch für Aufhärtungen im Bereich der Schnittkanten beim Schneiden oder Stanzen sowie die damit einhergehende ansteigende Empfindlichkeit gegen Rissbildung. Statt dessen zeigt sich, dass es im Zuge der nach der Kaltverformung durchgeführten Wärmebehandlung zu einer weiteren Steigerung der Festigkeit kommt, so dass bei einem erfindungsgemäß erzeugten kaltverformten Produkt eine hohe Festigkeit gezielt mit einem hohen Umformvermögen kombiniert ist. Diese Kombination vorteilhafter Eigenschaften ermöglicht es beispielsweise, das kaltverformte und anschließend wärmebehandelte Produkt nochmals kaltzuverformen, um es so in seine Endform zu bringen. Zudem steht das gute Umformvermögen beispielsweise bei crash-relevanten Bauteilen, wie Stoßfänger, Seitenaufprallträger, Verstärkungselemente, im vollen Umfang zur Verfügung, um im Falle eines Zusammenpralls mit anderen Gegenständen im großen Umfang kinetische Energie in Umformenergie umwandeln zu können.Due to the invention after cold working performed heat treatment with the Cold deformation regularly associated loss Deformability without loss of strength balanced. This also applies to, for example Hardening in the area of the cut edges when cutting or punching and the associated increasing Cracking sensitivity. Instead shows themselves that it is in the wake of the cold working performed heat treatment to another Strength comes, so that one Cold-formed product produced according to the invention high strength targeted with high formability is combined. This combination is more advantageous Properties makes it possible, for example, that cold-formed and then heat-treated product cold deform again to get it to its final shape bring. The good formability also stands out for example with crash-relevant components, such as Bumpers, side impact beams, reinforcement elements, available to the full extent in the event of a Collision with other objects on a large scale to be able to convert kinetic energy into forming energy.

Ebenso eignet sich das erfindungsgemäße Verfahren besonders zur Erzeugung von Bauteilen, an deren Maß- und Formhaltigkeit ebenso hohe Anforderungen gestellt werden wie an ihre Festigkeit im Einsatz. Ein typisches Beispiel für eine solche Anwendung stellen Rahmen für Bildschirme dar, die in Bildröhren von Fernsehern oder Computermonitoren die Schattenmaske aufgrund der Wärmebelastung während ihres Zusammenbaus und ihres Betriebes unter gleichmäßiger Spannung in einer fest definierten Ebene halten müssen. Die geforderte hohe Festigkeit erhält das so kaltverformte Bauteil dann im Zuge der nach der Kaltverformung erfindungsgemäß durchgeführten Wärmebehandlung, so dass im Ergebnis ein exakt geformtes, hochfestes Bauelement mit hoher Dehngrenze zur Verfügung steht. Eine zusätzliche Vergütung, die zum Verzug des Bauteils und einer Beeinträchtigung der Oberfläche führen kann, ist dann nicht mehr notwendig.The method according to the invention is also suitable especially for the production of components, their dimensions and Dimensional requirements are just as high as to their strength in use. A typical example for such an application provide frames for screens that are in picture tubes of televisions or Computer monitors the shadow mask due to the Thermal stress during their assembly and their Operation under uniform tension in a fixed defined level. The required high The so cold-formed component then receives strength in the According to the invention after the cold working performed heat treatment, so the result is a precisely shaped, high-strength component with high Yield strength is available. An additional Remuneration leading to the delay of the component and a The surface can then be impaired not necessary anymore.

Voraussetzung für den durch die Erfindung erzielten Erfolg ist, dass während der Warmverarbeitung des erfindungsgemäß verwendeten Stahls die Betriebsparameter einschließlich der Haspeltemperatur so gewählt werden, dass die durch die Anwesenheit einer ausreichenden Menge von Mikrolegierungselementen an sich mögliche Härtesteigerung im Zuge des Haspelns nicht erreicht wird, sondern dass die Mikrolegierungselemente nach dem Haspeln im nicht ausgeschiedenen, gelösten Zustand vorliegen. Aus diesem Grund wird die Haspeltemperatur erfindungsgemäß stets so gewählt, dass sie mit einem deutlichen Abstand unterhalb der Temperatur liegt, bei der das Ausscheidungsmaximum der Mikrolegierungselemente erreicht würde.Prerequisite for that achieved by the invention Success is that during the hot processing of the Steel used according to the invention the operating parameters including the reel temperature can be selected that by the presence of a sufficient amount of microalloying elements possible per se Hardness increase in the course of reeling is not achieved, but that the microalloy elements after reeling are present in the undissolved, dissolved state. Out for this reason the reel temperature is according to the invention always chosen so that they are at a clear distance is below the temperature at which the Elimination maximum of the microalloying elements reached would.

Die gemäß der Erfindung verwendete Stahllegierung umfasst Stahlzusammensetzungen, aus denen sich abhängig von der jeweiligen Zusammensetzung und den Produktionsbedingungen Dualphasenstähle, bainitische Stähle oder Complexphasenstähle herstellen lassen. Angestrebt werden dabei grundsätzlich Stähle mit einem feinkörnigen mehrphasigen Gefüge, in dem Bainit, Ferrit, Martensit und Restaustenit in abhängig vom jeweiligen Typ des Stahles abhängigen Umfang enthalten sind.The steel alloy used according to the invention comprises Steel compositions that make up depending on the respective composition and production conditions Dual phase steels, bainitic steels or Have complex phase steels manufactured. To be aimed for basically steels with a fine grain multiphase structure in which bainite, ferrite, and martensite Residual austenite depending on the type of steel dependent scope are included.

Nachdem aus einem Stahl mit einer erfindungsgemäß verwendeten Zusammensetzung ein Vormaterial erzeugt worden ist, wird dieses Vormaterial zu Warmband warmgewalzt. Die Warmwalzanfangstemperatur wird dabei so gewählt, dass die Mikrolegierungselemente weitestgehend in dem Stahl gelöst bleiben, damit sie für die im letzten Schritt des erfindungsgemäßen Verfahrens bewirkten Effekte zur Verfügung stehen.After made from a steel with an inventive used composition produces a primary material this raw material becomes hot strip hot rolled. The hot rolling start temperature is like this chosen that the microalloying elements largely stay loosened in the steel so that they can last for the Effected step of the method according to the invention Effects are available.

Bei konventionell vergossenen Brammen sollte die Walzanfangstemperatur zu diesem Zweck mindestens 1050 °C betragen. Besonders eignen sich zur Herstellung des Vormaterials allerdings Dünnbrammen- oder Dünnbandgießverfahren, mit denen es aufgrund des Umstandes, dass die Notwendigkeit einer Wiedererwärmung des Vormaterials bzw. einer Lösung der Mikrolegierungselemente nicht besteht und andererseits die Abkühlgeschwindigkeiten des Stranges hoch sein können, besonders sicher möglich ist, die Mikrolegierungselemente bis zum Beginn des Warmwalzprozesses weitgehend gelöst zu halten.With conventionally cast slabs, the Rolling temperature for this purpose at least 1050 ° C be. Are particularly suitable for the production of Primary material, however, thin slab or Thin strip casting process with which it is due to the Circumstance that the need for reheating of the primary material or a solution of Microalloying elements do not exist and on the other hand the cooling speeds of the strand are high can, particularly safely, is possible Microalloying elements until the beginning of the To keep the hot rolling process largely solved.

Die Warmwalzendtemperatur sollte bevorzugt im Austenitgebiet, also oberhalb der Ar3-Temperatur liegen, um die erfindungsgemäß angestrebte feinkörnige, mehrphasige Gefügestruktur zu erhalten.The hot rolling end temperature should preferably be in the austenite region, that is to say above the Ar 3 temperature, in order to obtain the fine-grained, multi-phase structure sought after according to the invention.

Die genaue Zusammensetzung der Gefügestruktur des erhaltenen Warmbands wird durch die chemischen Eigenschaften, die Aufwärm-, Walz- und Abkühlbedingungen sowie die Haspeltemperaturen bestimmt. Es hat sich gezeigt, dass sich die erfindungsgemäß erzielte Wirkung der Steigerung von Festigkeit und Umformbarkeit bei Dualphasenstählen besonders sicher dann einstellt, wenn die Haspeltemperatur maximal 300 °C beträgt. Bei Stählen mit überwiegend bainitischem Gefüge wird diese Wirkung bei Haspeltemperaturen sicher erreicht, die 350 °C bis 450 °C betragen. Complexphasenstähle sollten bevorzugt bei Temperaturen von 450 °C bis 550 °C gehaspelt werden.The exact composition of the structure of the hot strip obtained is obtained by chemical Properties, the warm-up, rolling and cooling conditions as well as the reel temperatures. It has shown that the effect achieved according to the invention increase in strength and formability Sets dual-phase steels particularly safely when the reel temperature is a maximum of 300 ° C. For steels with a predominantly bainitic structure, this effect safely reached at reel temperatures of up to 350 ° C 450 ° C. Complex phase steels should be preferred can be coiled at temperatures from 450 ° C to 550 ° C.

Schon im warmverformten Zustand besitzen Stähle der gemäß der Erfindung eingesetzten Art eine hohe Festigkeit von mindestens 550 N/mm2. Im Zuge der anschließenden Kaltverformung verfestigen die Stähle sehr stark. Gleichzeitig nimmt die Dehnung stark ab, so dass ein zwar hochfestes, jedoch nur schwer verformbares Produkt erhalten wird. Derart beschaffene kaltgeformte Bauteile besitzen aufgrund ihrer verminderten Umformbarkeit nur eine geringe Umformreserve und ein dementsprechend vermindertes Energieaufnahmevermögen. Sie sind als solche beispielsweise nur eingeschränkt für die Herstellung von Bauelementen geeignet, die als Stoßfänger in crashgefährdeten Bereichen eines Automobils eingesetzt werden sollen.Even in the hot-formed state, steels of the type used in accordance with the invention have a high strength of at least 550 N / mm 2 . In the course of the subsequent cold forming, the steels harden very strongly. At the same time, the elongation decreases significantly, so that a product that is high-strength but difficult to deform is obtained. Because of their reduced formability, cold-formed components of this type have only a small forming reserve and a correspondingly reduced energy absorption capacity. As such, for example, they are only suitable to a limited extent for the production of components which are to be used as bumpers in crash-prone areas of an automobile.

Indem erfindungsgemäß nach der Kaltverformung eine Glühung des erhaltenen Produkts bei Temperaturen und für Zeiten durchgeführt wird, durch welche die vollständige Rekristallisation sicher vermieden wird, , wird einerseits die Streckgrenze des verwendeten Stahls weiter angehoben. Andererseits werden durch die Glühung dessen Dehnungswerte wieder annähernd bis auf das Niveau angehoben, auf dem sich die Dehnbarkeit des Warmbandes vor der Kaltverformung befand. Auf diese Weise lassen sich die unmittelbar nach der Kaltverformung ursprünglich nur schwer umformbaren Produkte zu Bauteilen machen, die nicht nur hochfest sind, sondern aufgrund ihrer guten Dehnungseigenschaften auch ein hohes Umformvermögen besitzen. Sie eignen sich als solche für diejenigen Anwendungen, für die sie vor der Glühbehandlung gerade nicht geeignet gewesen sind.By according to the invention after the cold working Annealing the product obtained at temperatures and for Times is carried out by which the complete Recrystallization is safely avoided on the one hand, the yield strength of the steel used raised. On the other hand, through the annealing of it Elongation values again almost up to the level raised on which the stretchability of the hot strip before cold working. Leave this way immediately after the cold deformation make products that are difficult to form into components that are not only high strength, but because of their good Elongation properties also high formability have. As such, they are suitable for those Applications for which they are just prior to the annealing treatment were not suitable.

Typische Glühtemperaturen während des auf die Kaltverformung folgenden Glühens liegen im Bereich von 450 °C bis 700 °C, vorzugsweise im Bereich von 550 °C bis 650 °C. Glühzeit und Glühtemperatur sind dabei im begrenzten Rahmen gegeneinander austauschbar. D.h., bei hohen Temperaturen sind nur geringe Haltezeiten erforderlich und umgekehrt. Dementsprechend kann die Wärmebehandlung als separat durchgeführter Behandlungsschritt in einer Haube oder in einer Durchlaufglühe erfolgen. Eine in konventioneller Weise bei Bedingungen, die zu einer vollständigen Rekristallisation führen würde, erfolgende Glühbehandlung würde die durch die Erfindung erreichte Wirkung zunichte machen. Typical annealing temperatures during the Cold deformation of the following glow is in the range of 450 ° C to 700 ° C, preferably in the range of 550 ° C to 650 ° C. Annealing time and annealing temperature are in the limited frame interchangeable. That is, at high temperatures are only short holding times required and vice versa. Accordingly, the Heat treatment as carried out separately Treatment step in a hood or in a Continuous annealing. One in a conventional way in conditions leading to a complete Recrystallization would result in annealing treatment would nullify the effect achieved by the invention do.

Besonders günstig ist es, den Glühschritt einzubinden in eine Wärmebehandlung, der das aus dem Warmband kaltverformte Produkt im Zuge seiner Weiterverarbeitung ohnehin unterzogen wird. Bei diesem Schritt kann es sich beispielsweise um eine Verzinkung oder ein anderes Verfahren zur Beschichtung oder Passivierung der Oberfläche des kaltverformten Produktes handeln, das bei im Bereich der für die Glühbehandlung vorgesehenen Temperaturen durchgeführt wird.It is particularly favorable to incorporate the annealing step in a heat treatment that is from the hot strip cold-formed product in the course of its further processing is subjected anyway. At this step it can be for example a galvanizing or another Process for coating or passivation of the Act on the surface of the cold-formed product in the range provided for the annealing treatment Temperatures is carried out.

Die im Zuge der Kaltverformung erzielten Verformungsgrade betragen mindestens 2 % bis zur Grenzformänderung, wobei sich die durch die erfindungsgemäße Vorgehensweise erzielten Effekte insbesondere dann auswirken, wenn der Kaltverformungsgrad 5 % bis 20 %, insbesondere 5 % bis 10 %, beträgt. Die Kaltverformung kann beispielsweise als Rollprofilieren, Ziehen, Pressen oder Innenhochdruckumformen durchgeführt werden. Ein Kaltwalzen bei verhältnismäßig niedrigen Verformungsgraden ist dazu ebenfalls geeignet.The degrees of deformation achieved in the course of cold forming amount to at least 2% until the limit shape change, whereby yourself through the procedure according to the invention effects achieved especially if the Degree of cold deformation 5% to 20%, in particular 5% to 10%. The cold deformation can be, for example, as Roll profiling, drawing, pressing or Hydroforming can be performed. On Cold rolling at relatively low Degrees of deformation are also suitable for this.

Als Mirkolegierungselement kommt in erfindungsgemäßem Stahl mindestens eines der Elemente Ti, Nb und / oder V zum Einsatz. Selbstverständlich können diese Elemente kombiniert in Mengen zugegeben werden, die zur Auslösung der am Ende des erfindungsgemäßen Verfahrens bewirkten Ausscheidungsvorganges ausreichend sind. Besonders bevorzugt ist allerdings die Verwendung von Ti, das sich durch ein besonders günstiges Ausscheidungsverhalten auszeichnet. Wird Ti gemäß einer bevorzugten Ausgestaltung der Erfindung als einziges Mikrolegierungselement verwendet, so sollte sein Gehalt mindestens das 3,4-fache des Gehalts an N betragen, um ein ausreichendes Lösungspotential des Mikrolegierungselementes sicherzustellen. Bevorzugt liegt der Ti-Gehalt des Stahls zu diesem Zweck im Bereich 0,07, bis 0,15 Gew.-%, während der Stickstoffgehalt vorzugsweise weniger als 0,007 Gew.-% beträgt. Bei Ti-Gehalten in dieser Größenordnung wird die Bildung von Feinstauscheidungen mit aushärtender Wirkung optimal unterstützt.The micro-alloying element comes in accordance with the invention Steel at least one of the elements Ti, Nb and / or V for use. Of course, these items can combined in amounts to be triggered that caused at the end of the method according to the invention Elimination process are sufficient. Especially however, the use of Ti, which is preferred through a particularly favorable excretion behavior distinguished. If Ti is preferred Embodiment of the invention as the only one Microalloying element used, so should its content be at least 3.4 times the N content, in order a sufficient solution potential of the Ensure microalloying element. Preferably lies the Ti content of the steel for this purpose in the range 0.07, to 0.15 wt%, while the nitrogen content is preferably less than 0.007% by weight. With Ti contents on this scale the formation of Fine deposits with a hardening effect are optimal supported.

Abhängig vom Typ des jeweils verarbeiteten Stahls liegt der Al-Gehalt bevorzugt im Bereich von 0,015 bis 0,08 Gew.-%. bzw. 0,5 bis 1,5 Gew.-%.Depending on the type of steel processed the Al content is preferably in the range from 0.015 to 0.08% by weight. or 0.5 to 1.5% by weight.

Erfindungsgemäß erzeugte Stahlbleche eignen sich bevorzugt für die Kaltverformung zu Bauteilen, an deren Festigkeit bei gleichzeitig gutem Dehnungsverhalten und dementsprechend gutem Verformungsverhalten sowie hoher geometrischer Maßhaltigkeit hohe Anforderungen gestellt sind. Dabei zeichnen sich aus erfindungsgemäßen Blechen erzeugte Bauelemente durch geringes Gewicht und hohes Energieaufnahmevermögen aus.Steel sheets produced according to the invention are suitable preferred for cold forming into components on their Strength with good elongation behavior and accordingly good deformation behavior as well as high high dimensional accuracy are. They are characterized by sheets according to the invention produced components by low weight and high Energy absorption capacity.

Ein Beispiel für eine vorteilhafte Verwendung erfindungsgemäß erzeugter Stahlbleche ist die Herstellung von Rahmen für Flachbildschirme. Ebenso lassen sich aus erfindungsgemäß hergestellten Stahlblechen Bauelemente für Karosserien von Kraftfahrzeugen oder Anbauteile herstellen, die einerseits besonders fest und andererseits beispielsweise im Fall eines Zusammenstoßes mit einem anderen Fahrzeug die beim Aufprall frei werdenden kinetischen Energien in Verformungsenergie umwandeln müssen. Dies sind u.a. Längsträger, sog. "Crashboxen", Fahrwerksteile, Hohlstrukturteile und Verstärkungsteile, wie die A-, B- oder C-Säule der Automobilkarosserie. An example of an advantageous use Steel sheets produced according to the invention is the production of frames for flat screens. Likewise, Steel sheets manufactured according to the invention for vehicle bodies or attachments produce the one hand particularly firm and on the other hand, for example, in the event of a collision with another vehicle the on impact kinetic energies in deformation energy need to convert. These include Side members, so-called "Crash boxes", chassis parts, hollow structure parts and Reinforcing parts such as the A, B or C pillar of the Automobile body.

Erfindungsgemäß erzeugtes Warmband ist grundsätzlich zur Verzinkung geeignet. Dabei ist jedoch eine bei relativ niedrigen Temperaturen stattfindende, insbesondere stückweise erfolgende, Feuerverzinkung vorzuziehen, Verzinkungen, bei denen Temperaturen über 750 °C anfallen, sind dazu weniger geeignet, da dabei die hinsichtlich des erfindungsgemäß erzielten Effekts kritischen Temperaturen im jeweils verarbeiteten Werkstück überschritten werden können.Hot strip produced according to the invention is basically for Suitable for galvanizing. However, one is relative low temperature, especially piecewise, hot-dip galvanizing is preferable, Galvanizing at temperatures above 750 ° C are less suitable because the with regard to the effect achieved according to the invention critical temperatures in the processed Workpiece can be exceeded.

Nachfolgend wird die Erfindung anhand von Ausführungsbeispielen näher erläutert.The invention is described below with reference to Embodiments explained in more detail.

Ein gemäß Tabelle 1 zusammengesetzter Stahl ist auf einer Stranggießanlage zu einer Vorbramme vergossen worden, welches anschließend als Vormaterial mit einer Temperatur von 1125 °C in einer Warmbandstraße zu einem Warmband warmgewalzt worden ist. Die Warmwalzendtemperatur betrug 925 °C. Die Haspeltemperatur lag bei 475 °C. Nach dem Haspeln ist das Warmband gebeizt und im gebeizten Zustand an ein Kaltwalzwerk geliefert worden. C Si Mn P S Al N Cr 0,12 0,46 1,93 0,014 0,001 0,048 0,0061 0,29 Cu Mo Ni Nb Ti Ti s.l. V CE 0,056 0,008 0,034 0,001 0,190 0,0081 0,008 0,51 A steel composed according to Table 1 was cast on a continuous casting plant to a pre-slab, which was then hot-rolled as a starting material at a temperature of 1125 ° C. in a hot strip mill to a hot strip. The hot rolling end temperature was 925 ° C. The reel temperature was 475 ° C. After coiling, the hot strip is pickled and delivered to a cold rolling mill in the pickled state. C Si Mn P S al N Cr 0.12 0.46 1.93 0,014 0.001 0.048 0.0061 0.29 Cu Mo Ni Nb Ti Ti sl V CE 0.056 0,008 0.034 0.001 0,190 0.0081 0,008 0.51

Dort sind verschiedene Bandproben des Warmbands bei Kaltwalzgraden von 5 %, 10 %, 20 %, 30 %, 40 % kaltgewalzt worden. Aus den so erhaltenen Kaltbändern sind anschließend Gruppen G1 bis G5 zusammengestellt worden, wobei jeder Gruppe G1 bis G5 jeweils ein nicht kaltverformtes (Kaltverformungsgrad = 0 %), ein mit 5 %, ein mit 10 %, ein mit 20 %, ein mit 30 % und ein mit 40 % Kaltverformungsgrad kaltverformtes Kaltband zugeordnet worden ist. Die Bleche der Gruppe G1 sind zu Vergleichszwecken keiner auf die Kaltverformung folgenden Anlassglühung unterzogen worden, während die Bleche der Gruppe G2 bei 500 °C, die Bleche der Gruppe G3 bei 550 °C, die Bleche der Gruppe G4 bei 600 °C und die Bleche der Gruppe G5 bei 650 °C in einem Haubenofen für jeweils eine Stunde anlassgeglüht und anschließend an Luft abgekühlt worden sind.There are various samples of the hot strip at Cold rolling grades of 5%, 10%, 20%, 30%, 40% been cold rolled. From the cold strips thus obtained groups G1 to G5 are then put together been, with each group G1 to G5 each not one cold-formed (degree of cold deformation = 0%), one with 5%, one with 10%, one with 20%, one with 30% and one with 40% Degree of cold deformation assigned to cold-formed cold strip has been. The plates of group G1 are closed None for comparison purposes following the cold deformation Annealing has been carried out while the sheets of Group G2 at 500 ° C, the sheets of group G3 at 550 ° C, the plates of group G4 at 600 ° C and the Sheet of group G5 at 650 ° C in a hood furnace for annealed for one hour each and then on Air have been cooled.

In Tabelle 2 sind für jedes der Bleche der Gruppen G1 - G5 die im Zugversuch ermittelten Werkstoffeigenschaften eingetragen. Gruppe Lfd. Nr. Kaltwalzgrad
[%] Anlasstemp.
[°C] ReL
[N/mm2] Rp0,2
[N/mm2] Rm
[N/mm2] ReL/Rm
[N/mm2] A80
[%] Agl
[%] G1 G1.0 0 - 804 937 0,86 14,4 8,0 G1.1 5 - 845 995 0,85 13,4 6,3 G1.2 10 - 957 1046 0,91 7,4 2,3 G1.3 20 - 1090 1121 0,97 4,9E 1,2 G1.4 30 - 1148 1177 0,98 4,4E 1,1 G1.5 40 - 1147 1180 0,97 4,2E 1,3 G2 G2.1 5 500 947 967 0,98 12,0 7,0 G2.2 10 500 986 981 1,01 8,7 5,1 G2.3 20 500 1067 1069 1,00 7,1E 0,6 G2.4 30 500 1122 1122 1,00 5,5E 0,8 G2.5 40 500 1155 1159 1,00 5.1E 0,7 G3 G3.1 5 550 968 986 0,98 13,7 8,7 G3.2 10 550 1026 1031 1,00 12,6 8,1 G3.3 20 550 1087 1094 0,99 7,0 0,6 G3.4 30 550 1129 1132 1,00 5,8E 0,7 G3.5 40 550 1222 1224 1,00 4,9E 0,6 G4 G4.1 5 600 987 1004 0,98 13,4 7,6 G4.2 10 600 1017 1028 0,99 12,5 7,2 G4.3 20 600 1081 1085 1,00 7,3E 0,6 G4.4 30 600 1075 1075 1,00 6,9E 0,6 G4.5 40 600 1170 1173 1,00 5.1E 0,6 G5 G5.1 5 650 940 959 0,98 15,1 8,3 G5.2 10 650 951 966 0,98 15,3 8,0 G5.3 20 650 1004 1006 1,00 8,5E 0,6 G5.4 30 650 969 987 0,98 12,9 8,5 G5.5 40 650 966 974 0,98 14,2 7,9 *) Bei den in der Spalte A80 mit "E" gekennzeichneten Beispielen kam es zum Endbruch. The material properties determined in the tensile test are entered in Table 2 for each of the sheets in groups G1 - G5. group Ser. No. Cold rolling reduction
[%] Anlasstemp.
[° C] R eL
[N / mm 2 ] R p0.2
[N / mm 2 ] R m
[N / mm 2 ] R eL / R m
[N / mm 2 ] A 80
[%] A gl
[%] G1 G1.0 0 - 804 937 0.86 14.4 8.0 G1.1 5 - 845 995 0.85 13.4 6.3 G1.2 10 - 957 1046 0.91 7.4 2.3 G1.3 20 - 1090 1121 0.97 4,9E 1.2 G1.4 30 - 1148 1177 0.98 4,4E 1.1 G1.5 40 - 1147 1180 0.97 4,2E 1.3 G2 G2.1 5 500 947 967 0.98 12.0 7.0 G2.2 10 500 986 981 1.01 8.7 5.1 G2.3 20 500 1067 1069 1.00 7,1E 0.6 G2.4 30 500 1122 1122 1.00 5.5E 0.8 G2.5 40 500 1155 1159 1.00 5.1E 0.7 G3 G3.1 5 550 968 986 0.98 13.7 8.7 G3.2 10 550 1026 1031 1.00 12.6 8.1 G3.3 20 550 1087 1094 0.99 7.0 0.6 G3.4 30 550 1129 1132 1.00 5,8E 0.7 G3.5 40 550 1222 1224 1.00 4,9E 0.6 G4 G4.1 5 600 987 1004 0.98 13.4 7.6 G4.2 10 600 1017 1028 0.99 12.5 7.2 G4.3 20 600 1081 1085 1.00 7,3E 0.6 G4.4 30 600 1075 1075 1.00 6,9E 0.6 G4.5 40 600 1170 1173 1.00 5.1E 0.6 G5 G5.1 5 650 940 959 0.98 15.1 8.3 G5.2 10 650 951 966 0.98 15.3 8.0 G5.3 20 650 1004 1006 1.00 8,5E 0.6 G5.4 30 650 969 987 0.98 12.9 8.5 G5.5 40 650 966 974 0.98 14.2 7.9 *) The examples marked in column A 80 with "E" resulted in a final break.

Es zeigt sich, dass sich bei den in erfindungsgemäßer Weise verarbeiteten Blechen in Folge der nach der Kaltverformung durchgeführten Wärmebehandlung gegenüber den nur kaltverformten und nicht wärmebehandelten Blechen G1.1 - G1.5 jeweils deutlich verbesserte Festigkeitswerte einstellen. Gleichzeitig wird durch die nach der Kaltverformung durchgeführte Wärmebehandlung eine Gleichmaßdehnung Agl erreicht, die jeweils annähernd der Gleichmaßdehnung Agl des nicht kaltverformten und nicht wärmebehandelten Blechs Gl1.0 entspricht. Dementsprechend weisen die erfindungsgemäß erzeugten kaltverformten und anschließend wärmebehandelten Stähle eine besonders gute Umformbarkeit und ein ebenso gutes Energieaufnahmevermögen auf.It can be seen that in the sheets processed in the manner according to the invention, as a result of the heat treatment carried out after the cold working, the strength values obtained are significantly improved in comparison with the only cold-formed and not heat-treated sheets G1.1-G1.5. At the same time, a uniform expansion A gl is achieved by the heat treatment carried out after the cold working, which corresponds approximately to the uniform expansion A gl of the non-cold-formed and non-heat-treated sheet Gl1.0. Accordingly, the cold-formed and subsequently heat-treated steels produced according to the invention have particularly good formability and an equally good energy absorption capacity.

In Tabelle 3 ist ein zweites Beispiel einer erfindungsgemäß verwendeten Stahlzusammensetzung angegeben. C Si Mn P S Al N Cr 0,126 0,69 1,79 0,013 <0,001 0,050 0,0060 0,33 Cu Mo Ni Nb Ti B V CE 0,020 0,010 0,040 0,0040 0,1470 0,0002 - - Table 3 shows a second example of a steel composition used according to the invention. C Si Mn P S al N Cr 0.126 0.69 1.79 0,013 <0.001 0,050 0.0060 0.33 Cu Mo Ni Nb Ti B V CE 0,020 0,010 0,040 0.0040 .1470 0.0002 - -

Ein entsprechend legierter Stahl wurde erschmolzen und zu Brammen vergossen. Anschließend sind die Brammen auf eine Temperatur von mehr als 1150 °C wiedererwärmt und mit einer mindestens 850 °C betragenden Warmwalztemperatur warmgewalzt worden. Nach dem Haspeln bei einer Temperatur von weniger als 600 °C sind für eine erste unbehandelte Bandprobe T2.0 des Bandes, für eine 30 Minuten bei 580 °C geglühte und anschließend an Luft abgekühlte Bandprobe T2.1, für eine bei einem Kaltverformungsgrad von 10 % nur kaltgewalzte Bandprobe T2.2 und für eine in erfindungsgemäßer Weise bei einem Kaltverformungsgrad von 10 % kaltgewalzte, anschließend für 30 Minuten bei 580 °C geglühte und dann an Luft abgekühlte Bandprobe T2.3 die mechanischen Eigenschaften Rp0,2, Rm, Re/Rm A5, A50 bzw. A80 ermittelt worden. Die festgestellten Werte der mechanischen Eigenschaften sind in Tabelle 4 angegeben. Bandprobe Kaltwalzgrad ReL Rp0,2 Rm ReL/Rm A5 A50 A80 [%] [N/mm2] [%] T2.0 0 693 908 0,76 20,9 - 15,8 T2.1 0 892 929 0,96 22,3 17,4 - T2.2 10 974 1050 0,93 14,4 8,2 - T2.3 10 1037 - 1005 1,03 22,0 15,7 - A correspondingly alloyed steel was melted and cast into slabs. The slabs were then reheated to a temperature of more than 1150 ° C. and hot-rolled with a hot rolling temperature of at least 850 ° C. After coiling at a temperature of less than 600 ° C, for a first untreated strip sample T2.0 of the strip, for a strip sample annealed at 580 ° C for 30 minutes and then cooled in air, there is T2.1 for one with a degree of cold deformation of 10 % only cold-rolled strip sample T2.2 and for a strip sample T2.3 cold-rolled in the manner according to the invention with a degree of cold deformation of 10%, then annealed for 30 minutes at 580 ° C. and then cooled in air, the mechanical properties R p0.2 , R m , R e / R m A 5 , A 50 and A 80 have been determined. The determined values of the mechanical properties are given in Table 4. band practice Cold rolling reduction R eL R p0.2 R m R eL / R m A 5 A 50 A 80 [%] [N / mm 2 ] [%] T2.0 0 693 908 0.76 20.9 - 15.8 T2.1 0 892 929 0.96 22.3 17.4 - T2.2 10 974 1050 0.93 14.4 8.2 - T2.3 10 1037 - 1005 1.03 22.0 15.7 -

Auch diese Beispiele belegen, dass durch die erfindungsgemäße Kombination von Kaltverformung und anschließender Wärme hochfeste Stähle erzeugt werden, die aufgrund ihrer guten Dehnbarkeit ein besonders hohes Umformvermögen besitzen. So ist die Festigkeit der erfindungsgemäß erzeugten Bandprobe T2.3 der Festigkeit der unbehandelten Bandprobe T2.0 weit überlegen, während seine Dehnungswerte denen der unverformten Bandprobe T2.0 entsprechen. Ebenso weist die nur kaltverformte Bandprobe T2.2 gegenüber der erfindungsgemäß erzeugten Bandprobe T2.3 nicht nur eine weit unterlegene Dehnbarkeit, sondern auch eine geringere Festigkeit auf. Bei der nur wärmebehandelten Bandprobe T2.1 liegt zwar die Dehnbarkeit auf einem mit der erfindungsgemäß erzeugten Bandprobe T2.3 vergleichbaren Niveau. Gleichzeitig ist aber die Festigkeit der Bandprobe T2.1 der Festigkeit der erfindungsgemäß erzeugten Bandprobe weit unterlegen.These examples also demonstrate that the combination of cold forming and subsequent heat, high-strength steels are generated a particularly high one due to its good elasticity Have formability. So is the firmness of the Band sample T2.3 of the strength produced according to the invention far superior to the untreated tape sample T2.0, while its elongation values are those of the undeformed tape sample T2.0 correspond. Likewise, the only cold-formed tape sample shows T2.2 compared to the tape sample produced according to the invention T2.3 not only a far inferior extensibility, but also lower strength. With the only heat-treated tape sample T2.1 is the Stretchability on one with that produced according to the invention Band sample T2.3 comparable level. At the same time but the strength of the tape sample T2.1 the strength of the Inferior to the tape sample produced according to the invention.

Der entsprechend der in Tabelle 5 angegebenen Legierung zusammengesetzte Stahl ist ebenfalls erschmolzen und zu Brammen vergossen worden. C Si Mn P S Al N Cr 0,097 0,59 1,70 0,010 <0,001 0,035 0,0052 0,31 Cu Mo Ni Nb Ti B V CE 0,081 0,0057 0,0052 <0,0005 0,099 <0,0004 0,0033 - The steel composed according to the alloy specified in Table 5 was also melted and cast into slabs. C Si Mn P S al N Cr 0.097 0.59 1.70 0,010 <0.001 0,035 0.0052 0.31 Cu Mo Ni Nb Ti B V CE 0.081 0.0057 0.0052 <0.0005 0,099 <0.0004 0.0033 -

Anschließend sind diese Brammen wie beim im Zusammenhang mit dem in den Tabellen 3/4 angegebenen Beispiel auf eine Temperatur von mehr als 1150 °C wiedererwärmt, mit einer mindestens 850 °C betragenden Warmwalztemperatur und bei einer Temperatur von weniger als 600 °C gehaspelt worden. Anschließend sind dann sechs Bandproben T3.0 bis T3.5 genommen worden.Then these slabs are connected as with the with the example given in Tables 3/4 to a Temperature of more than 1150 ° C reheated, with a hot rolling temperature of at least 850 ° C and at at a temperature of less than 600 ° C. Then there are six tape samples T3.0 to T3.5 been taken.

Die mit den betreffenden Bandproben T3.0 bis T3.2 durchgeführten weiteren Verarbeitungsschritte sind ebenso wie die zugehörigen Werte der mechanischen Eigenschaften für eine der Bandmitte entnommene Probe in Tabelle 6 angegeben. Bandprobe Verarbeitung ReL Rp0,2 Rm ReL/Rm A5 A80 N/mm2] [%] T3.0 Unbehandelt - 771 884 0,87 11,8E 8,9E T3.1 10% kaltgewalzt - 957 1010 0,95 9,2E 7,6E T3.2 10% kaltgewalzt geglüht bei 580°C 946 - 960 0,99 16,8 15,4 The further processing steps carried out with the relevant tape samples T3.0 to T3.2 as well as the associated values of the mechanical properties for a sample taken from the tape center are given in Table 6. band practice processing R eL R p0.2 R m R eL / R m A 5 A 80 N / mm 2 ] [%] T3.0 untreated - 771 884 0.87 11,8E 8,9E T3.1 10% cold rolled - 957 1010 0.95 9.2E 7,6E T3.2 10% cold rolled annealed at 580 ° C 946 - 960 0.99 16.8 15.4

Auch in diesem Fall belegt die Bandprobe T3.2 deutlich, dass sich bei erfindungsgemäßer Vorgehensweise hochfeste kaltverformte Blechprodukte erhalten lassen, die, wie ein Vergleich der Dehnbarkeitswerte zeigt, hinsichtlich ihrer Umformbarkeit der unverformten Bandprobe T3.0 überlegen sind. Ebenso werden erfindungsgemäße Eigenschaftsverbesserungen erzielt, wenn kaltgewalztes Band über sehr viel längeren Zeiten bei vergleichsweise niedrigen Temperaturen, z.B. 450 °C bis 550 °C, in einer Haube geglüht werden.In this case too, the tape sample T3.2 clearly shows that high-strength in the procedure according to the invention let cold-formed sheet metal products are obtained which, like a Comparison of the ductility values shows, regarding their Formability superior to the undeformed tape sample T3.0 are. Likewise, according to the invention Property improvements achieved when cold rolled Band over much longer times at comparatively low temperatures, e.g. 450 ° C to 550 ° C, in one Hood to be annealed.

Ein Beispiel für eine besonders vorteilhafte Verwendung eines erfindungsgemäß erzeugten Stahls besteht in der Herstellung von Rahmen, in denen die Schattenmasken von Fernsehröhren gehalten werden. Zum Schwärzen der in einem derartigen Rahmen gespannten Schattenmaske wird der Rahmen mit der Schattenmaske über eine ausreichende Zeit einer Temperatur ausgesetzt, die typischerweise ca. 570 °C beträgt. Indem der Rahmen aus einem in erfindungsgemäßer Weise erzeugten Warmband unter Ausnutzung der in diesem Zustand hervorragenden Verformbarkeit des Warmbands durch Kaltverformung erzeugt und anschließend im Zuge des Schwärzens der von ihm gehaltenen Schattenmaske über eine ausreichende Zeit bei der zum Schwärzen erforderlichen Temperatur gehalten wird, erhöht sich die Festigkeit des Rahmens auf ein. Niveau, bei welchem der Rahmen sicher und formstabil die während der Herstellung und des Betriebs der Fernsehröhre auf ihn ausgeübte Wärmebelastung ertragen und Verzugsfreiheit der Schattenmaske gewährleisten kann.An example of a particularly advantageous use of a steel produced according to the invention consists in the Manufacture of frames in which the shadow masks of TV tubes are held. To blacken the one Such a tight shadow mask will Frame with the shadow mask for a sufficient time exposed to a temperature that is typically approx. Is 570 ° C. By making the frame out of one in hot strip produced according to the invention under Exploitation of the excellent in this state The hot strip is deformable by cold working and then in the course of the blackening of him held shadow mask for a sufficient time the temperature required for blackening the strength of the frame increases to. Level at which the frame is secure and dimensionally stable during the manufacture and operation of the television tube endure heat load applied to it and The shadow mask can guarantee freedom from distortion.

Eine andere vorteilhafte Anwendung des erfindungsgemäßen Verfahrens besteht in der Herstellung von verzinkten Seitenaufprallträgern oder anderen crashrelevanten Bauelementen für Fahrzeugkarosserien. Dabei wird zunächst aus erfindungsgemäß erzeugtem Warmband das jeweilige Bauteil beispielsweise durch eine Tiefziehoperation kaltgeformt. Das kaltgeformte Bauteil wird dann bei Temperaturen im Bereich von 470 °C einer Stückverzinkung unterzogen. Im Zuge dieses Verzinkungsvorgangs wird das Bauteil ebenfalls auf einem Temperaturniveau gehalten, bei dem sich die erfindungsgemäß erreichte Steigerung der Dehnbarkeit und Festigkeit einstellt. Der so erhaltene Seitenaufprallträger weist aufgrund seiner guten Dehnbarkeit und gleichzeitig hohen Festigkeit ein besonders hohes Energieaufnahmevermögen auf, durch welches er im Fall eines Zusammenstoßes mit einem anderen Fahrzeug einen großen Teil der dabei frei werdenden kinetischen Energie in Verformungsenergie umwandeln und den für das Überleben der Insassen erforderlichen Raum absichern kann.Another advantageous application of the invention The process consists in the production of galvanized Side impact beams or other crash-relevant Components for vehicle bodies. This will start with the respective from hot strip produced according to the invention Component, for example, through a deep-drawing operation cold formed. The cold-formed component is then at Temperatures in the range of 470 ° C for galvanizing subjected. In the course of this galvanizing process, Component also kept at a temperature level, in which the increase achieved according to the invention Elasticity and strength sets. The so obtained Side impact beam exhibits due to its good Elasticity and high strength at the same time particularly high energy absorption capacity which it does in the event of a collision with another Vehicle a large part of the free convert kinetic energy into deformation energy and the space necessary for the survival of the occupants can secure.

Claims (17)

  1. A method for manufacturing a high-strength product having good deformation capability, which is cold formed from a hot-rolled strip, wherein
    a steel having (in weight-percent): C 0.01 - 0.25%, Si 0.01 - 1.50%, Mn 0.50 - 2.00%, P ≤ 0.08%, S ≤ 0.01%, Al 0.001 - 1.50%, Cr ≤ 0.60%, Mo ≤ 0.60%, N ≤ 0.02%,
    and at least one microalloying element from the group Ti ≤ 0.20%, Nb ≤ 0.06%, V ≤ 0.15%,
    with the remainder iron and typical impurities, is cast into a precursor material, such as slabs, thin slabs, or cast strip,
    the precursor material is hot rolled into hot-rolled strip starting from a hot-rolling starting temperature at which the microalloying elements remain essentially dissolved,
    the hot-rolled strip is coiled at a coiling temperature of less than 600°C,
    the hot-rolled strip is subsequently cold formed into a product at a degree of cold forming of at least 2% and at most corresponding to the forming limit, and
    the product produced through cold forming is annealed at temperatures and for times which are below the temperatures and times required for complete recrystallization.
  2. The method according to Claim 1,
    characterized in that
    the steel contains Ti as the single microalloying element and that the ratio of the content of Ti to the content of N is at least 3.4.
  3. The method according to one of the preceding claims,
    characterized in that
    the hot rolling final temperature is at least equal to the Ar3 temperature.
  4. The method according to one of the preceding claims,
    characterized in that
    the coiling temperature is less than 300°C.
  5. The method according to one of Claims 1 through 3,
    characterized in that
    the coiling temperature is 350°C - 450°C.
  6. The method according to one of Claims 1 through 3,
    characterized in that
    the coiling temperature is 450°C - 550°C.
  7. The method according to one of the preceding claims,
    characterized in that
    the degree of cold forming is 5% - 20%, particularly 5% to 10%.
  8. The method according to one of the preceding claims,
    characterized in that
    the annealing temperature is 550 °C - 600 °C.
  9. The method according to one of the preceding claims,
    characterized in that
    the annealing is performed continuously.
  10. The method according to one of Claims 1 through 8,
    characterized in that
    the annealing is performed in a hood-type furnace.
  11. The method according to one of the preceding claims,
    characterized in that
    the precursor material is produced as a cast strip on a casting and rolling facility.
  12. The method according to one of the preceding claims,
    characterized in that
    the product produced through cold forming is a frame for flat display screens.
  13. The method according to one of Claims 1 through 11,
    characterized in that
    the product produced through cold forming is a component for the manufacture of vehicle bodies or an add-on part.
  14. The method according to one of the preceding claims,
    characterized in that
    the product is produced through hydroforming which is performed cold.
  15. The method according to one of the preceding claims,
    characterized in that
    the cold-formed product is subjected to galvanization.
  16. The method according to Claim 15,
    characterized in that
    the galvanization is performed as hot-dip galvanization.
  17. The method according to Claim 15 or 16,
    characterized in that
    the galvanization is performed at temperatures around 460 °C.
EP02738172A 2001-06-26 2002-06-21 Method for producing high-strength cold-formed steel products from a hot rolled strip, said products exhibiting good malleability Expired - Lifetime EP1399598B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10130774A DE10130774C1 (en) 2001-06-26 2001-06-26 Production of a high strength cold-formed product comprises pre-casting a steel to a pre-material, hot rolling into a hot strip so that the micro-alloying elements remain dissolved, coiling, cold-forming to a product, and annealing
DE10130774 2001-06-26
PCT/EP2002/006870 WO2003002772A1 (en) 2001-06-26 2002-06-21 Method for producing high-strength cold-formed steel products from a hot rolled strip, said products exhibiting good malleability

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EP1399598B1 true EP1399598B1 (en) 2004-10-13
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FR2855184B1 (en) * 2003-05-19 2006-05-19 Usinor COLD LAMINATED, ALUMINATED, HIGH STRENGTH, DUAL PHASE STEEL FOR TELEVISION ANTI-IMPLOSION BELT, AND METHOD FOR MANUFACTURING THE SAME
US10071416B2 (en) 2005-10-20 2018-09-11 Nucor Corporation High strength thin cast strip product and method for making the same
US9149868B2 (en) 2005-10-20 2015-10-06 Nucor Corporation Thin cast strip product with microalloy additions, and method for making the same
US9999918B2 (en) 2005-10-20 2018-06-19 Nucor Corporation Thin cast strip product with microalloy additions, and method for making the same
DE112006003169B4 (en) * 2005-12-01 2013-03-21 Posco Steel sheets for hot press forming with excellent heat treatment and impact properties, hot pressed parts produced therefrom and process for their production
US20110277886A1 (en) 2010-02-20 2011-11-17 Nucor Corporation Nitriding of niobium steel and product made thereby
US20180209011A1 (en) 2015-07-17 2018-07-26 Salzgitter Flachstahl Gmbh Method of producing a hot strip of a bainitic multi-phase steel having a zn-mg-al coating, and a corresponding hot strip
DE102016005532A1 (en) * 2016-05-02 2017-11-02 Vladimir Volchkov stole
CN109023105B (en) * 2018-09-25 2020-11-13 首钢集团有限公司 Hot-rolled strip steel for automobile structure and manufacturing method thereof
CN110684932B (en) * 2019-10-12 2021-06-08 唐山钢铁集团有限责任公司 1500 MPa-grade cold-formed strip steel and production method thereof

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US3950190A (en) † 1974-11-18 1976-04-13 Youngstown Sheet And Tube Company Recovery-annealed cold-reduced plain carbon steels and methods of producing
US3963531A (en) † 1975-02-28 1976-06-15 Armco Steel Corporation Cold rolled, ductile, high strength steel strip and sheet and method therefor
US4082576A (en) † 1976-10-04 1978-04-04 Youngstown Sheet And Tube Company Ultra-high strength low alloy titanium bearing flat rolled steel and process for making
DE19710125A1 (en) * 1997-03-13 1998-09-17 Krupp Ag Hoesch Krupp Process for the production of a steel strip with high strength and good formability
FR2796083B1 (en) † 1999-07-07 2001-08-31 Usinor PROCESS FOR MANUFACTURING IRON-CARBON-MANGANESE ALLOY STRIPS, AND STRIPS THUS PRODUCED

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EP1399598B2 (en) 2011-02-23
EP1399598A1 (en) 2004-03-24

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