EP2531308A2

EP2531308A2 - Metal strip having a constant thickness and varying mechanical properties

Info

Publication number: EP2531308A2
Application number: EP11702167A
Authority: EP
Inventors: Jens-Ulrik Becker; Harald Hofmann
Original assignee: ThyssenKrupp Steel Europe AG
Current assignee: ThyssenKrupp Steel Europe AG
Priority date: 2010-02-03
Filing date: 2011-01-25
Publication date: 2012-12-12
Also published as: US10155256B2; DE102010000292B4; CN102740987B; WO2011095417A3; WO2011095417A2; US20120328899A1; CN102740987A; DE102010000292A1

Abstract

The invention relates to a metal strip (1) made of steel by generating a hot rolled strip by hot rolling and cold rolling the metal strip (1); the invention further relates to a plate which is made from the metal strip according to the invention and to the use thereof and to a method for producing the metal strip (1). The aim of creating a metal strip (1) from which components having minimal weight and adapted to specific stresses can be produced with little effort is solved by a metal strip (1) of the type in question which has a constant metal strip thickness after cold rolling and regions (2-6) in sections having varying mechanical properties. After cold rolling according to the invention means that immediately after completion of cold rolling, that is, without further treatment, such as temperature treatment, there are regions (2-6) of varying mechanical properties in the metal strip (1).

Description

Metal band with different mechanical properties

The invention relates to a metal strip made of steel by producing a hot strip by hot rolling and

Ka ltwal zen of the metal strip, moreover, the invention relates to a circuit board, which is made of the metal strip according to the invention and its use and a method for producing the metal strip.

In the automotive industry, but also in many others

In applications where minimal weight is required with specific requirements for the mechanical properties of a component, it is often necessary for optimum design of the component to vary the mechanical properties of the circuit board or sheet from which the component is made. In the manufacture of steel components, in particular of

Structural components for motor vehicles, the use of so-called "tailored blanks" is known in which the

Components are made of a circuit board, which in turn consists of two frontally interconnected sheets with different mechanical properties. For example, by varying the thickness at

consistent steel grade higher strength in the range of higher thickness can be provided. Furthermore, it is possible with a constant material thickness, a

Produce sheet metal section from a high-strength steel grade and to weld this with a thick, less solid steel grade. However, the production of "tailored blanks" is complex and requires additional work steps including a laser welding step. In addition, it is known in a hot strip by flexible hot rolling but also by a flexible cold rolling a warm or

Ka ltband produce with sections varying thickness, which due to the varying thickness in the specific areas different mechanical properties

having . The problem with this method is that a band with varying thickness is problematic in handling and thus create problems in the necessary process steps for the production of a component. A corresponding method is for example from the German

Publication DE 100 41 280 AI known.

The present invention is therefore based on the object to provide a metal strip available, adapted from which with little effort to specific loads

Components with minimal weight can be produced. It is also intended to propose a method for producing the metal strip, a board made of the metal strip and their specific use.

According to a first teaching of the present invention, the object is achieved by a metal strip, which after cold rolling a constant metal strip thickness and sections of areas with varying mechanical properties

having . After cold rolling in the sense of the present invention means that immediately after completion of the cold rolling, i. without any further treatment, for example, a temperature treatment, areas

varying mechanical properties are present in the metal strip. Due to the constant thickness of the metal strip after the

Cold rolls can be cut from the metal strip using conventional devices to produce blanks having regions with varying mechanical properties. There are no more difficulties in handling the metal strip. Furthermore, the constant thickness in the design of any required forming tools and also during the forming process as such is advantageous. Thus, it is possible to produce a component by simple means, which has varying mechanical properties in different ways

Having areas despite identical wall thickness. In this respect, from the metal strip according to the invention a board can be produced, which is designed to be load-appropriate, a

has constant thickness and without additional

Welding process, as for example in a "tailored blank" manages a Dickensprung is in the

Metal strip according to the invention is not provided, so that it can be easily wound on a coil and

Processing.

According to a first embodiment of the invention

Metal bands indicate the areas with varying

mechanical properties different tensile strengths, yield strengths and / or elongation at break on. By the

Adjustment of these mechanical properties in the

different areas of the metal strip, can

various load situations of the produced from the metal strip board are taken into account. According to a further embodiment of the metal strip according to the invention, the cold-rolled metal strip by flexible hot rolling, by flexible casting or by made flexible cold rolling with subsequent annealing, so that the metal strip prior to cold rolling has areas with varying thicknesses, the areas of varying thickness after cold rolling have varying Abwalzgrade and optionally periodically arranged. This ensures that the metal strip immediately after cold rolling

obtained in sections due to the different rolling degrees during cold rolling varying mechanical properties. In essence, solidifications in the metal strip are produced by the varying degrees of rolling, the extent of which

Material is dependent. Depending on the material is in particular to what extent tensile strength, yield strength and

Relatively change the elongation at break for a given rolling degree. For example, flexible casting can be done by in-line gouging using a ribbon casting process or direct-strip-casting (DSC) with inline hot rolling. However, also by a flexible cold rolling with a subsequent annealing a Metai Iband for the Kaltwal zen be provided to final thickness, which then has areas with varying Abwalzgraden or varying mechanical properties.

Preferably, the regions with varying mechanical properties are arranged periodically on the metal strip, so that there is the possibility of a simple way

Produce a variety of load-balanced designed boards from the metal strip.

An advantageous forming behavior of a component but also a circuit board can be achieved by arranging transition regions between the regions of the metal strip with varying mechanical properties the mechanical properties, in particular tensile strengths, yield strengths and / or elongation at break are at least partially changed continuously, are arranged. By the transition regions, for example, between egg nem area with a high and a region with lower tensile strength, for example, the forming behavior of the board in the manufacture of components can be improved because the board is less prone to the formation of cracks. The cracking tendency of deformed components with corresponding transitional areas of the mechanical properties is also lower under load. The width of the

Transition areas is preferably 50 mm and more. Cold rolling rates, for example after flexible hot rolling, can vary between 0 and 50%. However, it goes without saying that in order to achieve a constant thickness, the areas with greater wall thickness must have a rolling degree of greater than 0% during cold rolling.

The thickness of the metal strip is preferably 0.5 mm to 3 mm. In these areas, for example, can be produced by flexible hot rolling and subsequent cold rolling in a simple way a metal strip with varying mechanical properties in sections. The metal band itself is particularly well suited for this strength

Structural applications in which a load-appropriate

Interpretation is required.

In principle, any steel grade is suitable for the production of a metal strip according to the invention, although the strongly strengthening steel grades are preferred. advantageous

Therefore, embodiments of the metal strip according to the invention consist of high-manganese steels, rust-free stainless steels For example, stainless austenitic stainless steels or.

stainless steels with duplex structure, retained austenitic or dual-phase steels, wherein the metal strip may preferably have an organic and / or inorganic coating. As an inorganic coating is in particular a

Galvanization in question, but also an AlSi coating, if desired. The steels mentioned above show in particular a significant increase in the tensile strength and the yield strength in Berel chen with higher Abwal zgrad compared to other steel grades, without the

Corresponding elongation at break values decrease too much. This is important for subsequent forming processes of the components and when using the later component. This effect is used to provide areas of very high tensile strength and yield strength.

According to a second teaching of the present invention, the previously derived object is also achieved by a circuit board

manufactured from a metal strip according to the invention dissolved, wherein the board has a constant thickness, consists of a single steel material and sections having regions with varying mechanical properties. The board is therefore cut out of the metal strip according to the invention such that areas with varying

mechanical properties in a circuit board from a

single material immediately after cold rolling

can be provided. Through the targeted selection and adjustment of the mechanical properties over the

Cold rolling, the board can be designed to load and optimally adapted to their intended use. The whole thing happens without other additional materials, which in principle the recyclability of the board and from it deteriorated components would deteriorate. This is particularly important in the recycling of high-alloy steels. The board can have several areas which show varying mechanical properties in order to be designed to be load-bearing.

A further advantageous embodiment of the circuit board according to the invention is achieved in that the board between the areas with varying mechanical properties

Transition areas in which the mechanical properties change at least partially continuously. The transitions, for example, between areas with

different tensile strength are therefore not abrupt, but change continuously, so that the resulting component in terms of possible load pickups,

For example, during forming but also when used as Strukturbautei 1, vortei Ihafte have Eigenscha ften and, for example, less prone to cracking. Preferably, the areas with varying mechanical properties of the board differ! Ie tensile strength, yield strength and / or elongation at break on. These

Properties can be easily understood by the

Adjust the degree of rolling during cold rolling and the resulting solidification, so that the board can be easily prepared by cutting from the kaltgewaltzen metal strip. Additional process steps are no longer needed for this purpose. Of course, the board may also be coated organically and / or inorganic. Finally, the above object is achieved according to a third teaching of the present invention by a method for producing the metal strip made of steel, in which a slab made of steel by flexible

Hot rolling, by flexible casting or by flexible

Cold rolling is provided with a subsequent annealing a metal strip with areas of varying metal strip thickness and the metal strip is cold rolled to a constant final thickness. As already stated, by the alternative manufacturing process metal strips made of steel with varying metal strip thickness for cold rolling to final thickness

be prepared so that inexpensive circuit boards can be produced with load-adapted designed mechanical properties v / earth.

In this method, for example, according to a

Altered alternative in the last hot roll pass of the roll gap during the rolling process to produce a hot strip with regions of varying hot strip thickness. During the

Cold rolling hardens the areas with higher thickness more severely and thus experiences a stronger solidification than areas with less Abwai zgrad. The solidification leads to a change in the mechanical properties, in particular the tensile strength, the yield strength and / or the elongation at break. As already stated, the changes are this

mechanical properties are material dependent and can vary widely.

It has been shown that, according to another

inventive design of the method of Äbwal zgrad during cold rolling in the areas of the hot strip with a greater thickness preferably a maximum of 50%, or a maximum of 20%. Of course, the areas with larger

Hot strip thickness have a rolling degree of more than 0% to give a constant final thickness of the metal strip. However, it has been found that Abwalzgrade of more than 50%, a more difficult further processing of the metal strip

and are only possible with very soft steel grades.

Preferably, the degree of rolling in the areas with a lower hot strip thickness after quay twal zen 0% to 10%. At a degree of rolling of 0%, these areas of the metal strip remain unrolled and undergo no additional

Solidification. In addition, a moderate increase, for example, the tensile strength can be achieved by the degree of rolling of these areas during Kaltwal zen is set to a maximum of 10%. The desired tensile strength, yield strength and / or elongation at break, depending on the material, can thus be set via the abrading grade.

Finally, the method according to the invention can be further improved by removing from the metal strip after cold rolling and an optional organic and / or

inorganic coating of the finished rolled metal strip blanks are cut. The cutting of the blanks can be done immediately after the cold rolling resp. take place on any scheduled coating operations. However, it is conceivable to wind the metal strip initially on a coil, optionally later to coat it and

then cut boards out of the metal strip. Ultimately, the above task is also by the

Use of a board according to the invention in vehicle construction, motor vehicle construction and rail vehicle construction, preferably as Reshaped structural component, solved. Due to the possibility of designing the board load-bearing, to use a uniform material and yet to provide varying strengths with constant wall thickness available, the board can be adapted particularly well for use in vehicle construction or on the structural component. The use also enables a particularly cost-effective production of load-balanced designed components,

respectively structural components. In addition, that will

Recycling through the use of a board made of a single material significantly improved.

Furthermore, the invention will be explained in more detail with reference to a drawing and the description of exemplary embodiments. In the drawing shows

Fig. 1 in a longitudinal section, the cross-sectional shape of a

Hot strip after flexible hot rolling and schematically the corresponding use

Work rolls during hot rolling,

Fig. 2 in a longitudinal section a first

Embodiment of the invention

Metal strip after cold rolling,

3 is a diagram of the associated tensile strength,

Yield strength and elongation at break of the metal strip of the first embodiment, FIG. 4 in a plan view a printed circuit board produced from the metal strip of the first exemplary embodiment, Fig. 5 in a longitudinal section another hot strip, which for producing a second

Embodiment of the metal strip according to the invention is used,

Fig. 6 in a longitudinal section a second

From exemplary embodiment of an inventive

Metal bands produced from the hot strip of FIG. 5,

Fig. 7 in a diagram the associated tensile strength,

Yield strength and elongation at break of the second embodiment and FIG. 8 shows a top view of a circuit board according to the invention made from the metal strip according to FIG. 6.

In Fig. 1 is. a hot strip 1, which has been hot rolled over the work rolls 7a, 7b by changing the roll gap during rolling, so that areas 2, 3, 4, 5, 6 are produced, which have different thicknesses. In the transition areas 3, 5 between the

Areas 2, 4, 6, the thickness of the metal strip 1 changes continuously. As shown in FIG. 1 can be seen

For example, the thickness change only by changing the position of a Arbeitswal done ze.

It is also conceivable that both Arbeitswal zen 7 a, 7 b are slidable in position. For the hot strip in the present embodiment, the material "X-IP1000" has been selected, which as

Main alloy components besides iron one Carbon content of 0.6% by weight, a manganese content of 22% by weight and a silicon content of 0.2% by weight. -% having. This steel is one of the high manganese steels. In principle, however, as already stated. , all

Steel grades suitable for hardening by cold rolling varying tensile strengths, yield strengths and / or

To provide elongation at break.

In the first embodiment, the transition regions 3, 5 have been selected with a length of 50 mm, wherein the regions 2, 6 with a reduced hot strip thickness has a length of 200 mm and the region 4 with increased wall thickness has a length of about 800 mm. As wall thicknesses, for example, 1, 8 mm are provided in the areas with reduced wall thickness and 2 mm in the areas with greater wall thickness.

Of course, as well as the second

Embodiment shows other aspect ratios are selected. Fig. 2 shows the hot strip of Fig. 1 after the cold rolling. The thickness of the metal strip 1 after cold rolling in the present embodiment is uniformly 1, 8 mm, so that the region with increased hot strip thickness 4 has a degree of rolling of about 10%. All other areas have one

Rolling degree of less than 10% resp. 0% on. Due to the continuously increasing in the transition regions 3, 5 wall thickness to the area 4 of the metal strip 1, change after Kaltwal zen in these areas continuously the Abwalzgrad and thus the mechanical properties, such as tensile strength, yield strength and / or elongation at break. This can be seen on the diagram in FIG. 3 are read. In the area 2, the tensile strength is initially above 1000 MPa, which is the initial state at a degree of rolling of 0%

corresponds to and grows in the transition region 3 to about 1200 MPa. In area 4 with maximum rolling degree remains the

Tensile strength at more than 1200 MPa and falls only in the range 5 to the original value, which is achieved in the range 6 from. A similar behavior shows the

Yield point, wherein the change in the yield point at a degree of rolling of 10% is even more pronounced, since in the

Area with higher degree of rolling, an increase of

Yield strength of 500 MPa to about more than 800 MPa. The changes caused by the solidification depend strongly on the material, so that the values shown are specific to this material "X-IP1000".

By flexible rolling so transition areas are created in which the mechanical properties, as shown in FIG. 3, the elongation at break, change continuously. The relative changes are dependent on the material which is used for the production of the metal strip 1 according to the invention. In the metal strip 1 according to the invention, therefore, sections with increased tensile strength and yield strength alternate with reduced elongation at break with regions of increased elongation at break and reduced

Tensile strength and reduced yield strength. Preferably, a periodic arrangement of these areas is provided, so that in a simple manner identical boards from the

Metal band can be produced. Such a board is shown by way of example FIG. 4 in a plan view. The board may have, for example, a width of 400 mm and a length of 1300 mm. The areas 2 and 6 with reduced tensile strength and yield strength and increased elongation at break are 200 mm long, whereas the

Transition regions 3, 5, which are arranged between the areas 2 and 4 or 4 and 6 of the board, have a length of only 50 mm. Another embodiment is shown in Figs. 5 to 8 explained. First, in Fig. 5 a flexibly cast hot strip 8 from a stainless steel grade 1.4318 shown, which provides areas 9, 10, 11 with different thicknesses. The thickness of the hot strip 8 is for example in the range 9 1.7 mm and in the area eleventh

1, 9 mm. After cold rolling to a final thickness of 1.62 mm, the area 9 of the metal strip 8 is rolled off with a rolling rate of 5%, as shown in FIG. 6 shows. In the transition region 10, the Abwalzgrad then increases to 15%, as he beispielswei se in area 11 is achieved. Due to these different Abwal degrees, on the one hand 5% and more, the cold strip thus produced on the one hand significantly changed properties compared to the starting material before

Cold rolling step (Rp _0.2 = 340 MPa, R _m = 730 MPa and A ₈₀ = 48%) and on the other hand significantly varying properties between the individual areas with different rolling degrees. This in turn can be seen on the diagram in FIG. 7, in which the yield strength, the tensile strength and the elongation at fracture of the material in the different areas are shown. In Fig. 8, the board is now shown in a plan view. The board 8a has a slightly more than 400 mm long area, in which the rolling degree is relatively low and the lower tensile strengths and yield strengths are achieved with improved elongation at break. The at least

100 mm transition region 10 of the board has a continuously increasing tensile strength or.

Yield limit, which ultimately lead to the values for the more heavily rolled portion 11 of the board. Of the

Area with the highest possible Abwalzgrad, for example, be about 900 mm long.

The boards according to the invention from FIG. 4 and FIG. 8 can be used to components for vehicle construction, in particular to

Structural components (not shown) are processed, whereby they are optimally adapted to the specific loads. For example, for reasons of corrosion protection, the boards before or after the conversion to a component nor with an organic and / or inorganic coating (not shown), for example a

Galvanization, be provided.

Claims

claims

1. metal strip (1, 8) made of steel by producing a hot strip (1, 8) by hot rolling and cold rolling of the metal strip (1, 8),

The metal strip (1, 8) after cold rolling has a constant metal strip thickness and sections (2, 3, 4, 5, 6, 9, 10, 11) with varying mechanical properties.

2. Metal strip according to claim 1,

In other words, the regions (2, 3, 4, 5, 6, 9, 10, 11) with varying mechanical properties have different tensile strengths, yield strengths and / or elongations at break.

3. Metal strip according to claim 1 or 2,

The metal strip (1, 8), which can be cold-rolled, is flexible due to the fact that it can be cold-rolled metal strip (1, 8)

Hot rolling, by flexible casting or by flexible cold rolling followed by annealing, so that the metal strip has areas (2, 3, 4, 5, 6, 9, 10, 11) of varying thickness before cold rolling, the areas (2, 3, 4, 5, 6, 9, 10, 11) of varying thickness after cold rolling have varying degrees of rolling and are optionally arranged periodically.

4. Metal strip according to one of claims 1 to 3,

d a d u r c h e k e n e i n e, between the areas (2, 4, 6, 9, 11) of the metal strip with varying mechanical properties

Transition regions (3, 5, 10) are arranged, in which the mechanical properties, in particular

Tensile strengths, yield strengths and / or elongations at least partially continuously change. 5. Metal strip according to one of claims 1 to 4,

d a d u r c h e k e n e c i n e t, d a s s is the thickness of the metal strip (1, 8) 0,

5 mm to 3 mm

is.

6. Metal strip according to one of claims 1 to 5,

The metal strip (1, 8) made of high-manganese steels, stainless steels, retained austenitic or .alpha

Dual phase steels exists and optionally has an organic and / or inorganic coating.

7. A board made of a metal strip according to one of claims 1 to 6,

That is, the board (1a, 8a) has a constant thickness, consists of a single steel material, and has sections (2, 3, 4, 5, 6, 9, 10, 11) with varying mechanical properties in sections. 8. Plat ine according to claim 7,

characterized in that the board between the areas (2, 4, 6, 11) with varying mechanical properties transition regions (3, 5, 10), in which the mechanical properties change at least partially continuously.

Board according to claim 7 or 8,

By way of example, the ranges (2, 3, 4, 5, 6, 9, 10, 11) with varying mechanical properties are different

Tensile strengths, yield strengths and / or elongations at break have.

A method of producing a steel strip of steel according to any one of claims 1 to 6, wherein from a slab of steel by flexible hot rolling, by flexible casting or by flexible cold rolling with a subsequent annealing a metal strip is provided with areas mitvari ing metal strip thickness and the metal strip on a constant final thickness is cold rolled.

Method according to claim 10,

d a d u r c h e c e n e, e s the degree of rolling during cold rolling in the areas of the metal strip with greater metal strip thickness is up to 50%, preferably up to 20%.

Method according to claim 10 or 11,

characterized in that the degree of rolling of the metal strip in the areas with a lower metal strip thickness during cold rolling is 0% to 10%.

13. The method according to any one of claims 10 to 12,

d a d u r c h e s e n c i n e t, d a s s from the metal strip after cold rolling and a

optional organic and / or inorganic

Coating the finished rolled metal strip blanks are cut out of the metal strip.

14. Use of a circuit board according to one of claims 7 to 9 in vehicle construction, motor vehicle construction and rail vehicle construction, preferably as a reshaped structural component.