EP3720648A1

EP3720648A1 - Steel material composite, method for producing a component, and use

Info

Publication number: EP3720648A1
Application number: EP17811278.5A
Authority: EP
Inventors: Thomas Grosserüschkamp; Maik BOGATSCH
Original assignee: ThyssenKrupp Steel Europe AG; ThyssenKrupp AG
Current assignee: ThyssenKrupp Steel Europe AG; ThyssenKrupp AG
Priority date: 2017-12-05
Filing date: 2017-12-05
Publication date: 2020-10-14
Also published as: US20210213708A1; JP2021505761A; WO2019110087A1; US11351754B2; CN111432981A

Abstract

The present invention relates to a steel material composite having at least two layers (1, 2, 3, 4) comprising at least a first layer (1, 3) made of a machinable and/or shearable steel and at least a second layer (2, 4) made of a formable steel, which is integrally bonded to the first layer (1, 3)

Description

Steel material composite, method for producing a component and use

Technical Field

The invention relates to a composite steel material with at least two layers of steel. Furthermore, the invention relates to a method for producing a component and a use of the component.

Technical Background (Background Art)

In vehicle construction, for example in the area of the drive train of a vehicle, components are used which have to be machined on account of precision and / or surface requirements.

In the prior art machinable and / or shear steels are known. These are made for the most part of semi-finished products, which are usually provided in a cylindrical shape and are used in particular for the production of rotationally symmetrical components, whereby they are exposed from a solid material predominantly to a cutting turning operation until the final geometry is generated. This processing is very material and cost intensive.

In order to reduce at least the use of materials, machinable and / or shearable steels can usually be formed from a flat product to a pre-geometry before they are machined or machined to produce the final geometry. Good machinable and / or shearable steels generally have poor forming properties, since the alloying components, such as lead, phosphorus and / or sulfur, which cause good machinability, counteract the formability. Steels are used which are easy to form, but do not show the desired chip pattern during machining, but form so-called flow chips. The disadvantage of the formation of the flow chips is that they can damage the surface of the workpiece to be machined. Furthermore, this can enforce the chip tool, which increases the cleaning effort and thereby in turn can extend the processing time. The service life of the cutting tool can be shortened. Summary of Invention

The invention is therefore based on the object to provide a semifinished product, which combines the above-mentioned opposing properties, whereby the aforementioned disadvantages can be substantially compensated or reduced.

This object is achieved by a steel composite material with the features of patent claim 1.

In order to combine the abovementioned opposing properties in a semifinished product, a steel composite material is proposed with at least two layers, which at least a first layer of a machinable and / or shearable steel and at least one second layer of a malleable steel, which materially with the first layer is connected. The steel composite according to the invention ensures sufficient formability with good machinability and / or shearability.

Machinable and / or shearable steels are in particular free-cutting steels (EN 10087). Also, tempered steels (EN 10083), case hardening steels (EN 10084) or nickel steels (EN 10085), each with a sulfur content of at least 0.01% by weight, can be used.

In particular, steels of the grades DC (DIN EN 10130), DD (DIN EN 10111), DX (DIN EN 10346) or fine grain steels for cold forming (EN 10149) are to be understood as malleable steels. Steels that can be shaped in particular under the influence of temperature in such a way that the required final geometry of the component to be manufactured can be imaged without failure can be used.

According to a first embodiment, the at least first layer of the steel composite material is composed, by way of example, of Fe and, in terms of production, unavoidable impurities in% by weight

C: up to 0.60%,

Si: up to 1.00%,

Mn: up to 2.00%,

P: to 0, 150%,

S: up to 0.50%,

Pb: up to 0.50%, with SP + S + Pb> 0.020 wt%,

wherein the first layer may optionally comprise one or more of the following optional alloying elements:

optional Cr: up to 3.0%,

optional Cu: up to 0.50%,

optional Nb: up to 0.050%,

optional Mo: up to 1.0%,

optional N: up to 0.020%,

optional Ti: up to 0.020%,

optional V: up to 0.40%,

optional Ni: up to 5.0%,

optional B: up to 0.010%,

optional Sn: up to 0.050%,

optional H: up to 0.0010%,

optional As: up to 0.020%,

optional Co: up to 0.020%,

optional 0: to 0.0050%,

optional Ca: up to 0.0150%,

optional AI: up to 1.0%.

C is a strength-increasing alloying element and contributes to the increase in hardness to the hardness by either dissolved as an interstitial atom in austenite or forms with Fe or the optionally alloyed alloying elements Cr, Ti, Nb and / or V carbides, on the one hand harder than the surrounding Can be matrix or at least distort it so that the hardness of the matrix increases. C is therefore present at levels of at least 0.020 wt.%, More preferably at least 0.070 wt.%, Preferably at least 0.10 wt.%, To achieve a desired hardness and some mechanical resistance To ensure processing. The C content is limited to a maximum of 0.60 wt .-%, in particular a maximum of 0.55 wt .-%.

Si is an alloying element that can contribute to solid solution hardening and, depending on the content, has a positive effect in increasing the hardness, so that a content of at least 0.020% by weight, in particular at least 0.050% by weight, can be present. At lower levels of effectiveness of Si is not clearly demonstrated. Si, however, does not negatively affect the properties of the steel. If too much silicon is added to the steel, it has a negative influence on the deformability and toughness properties. Therefore, the alloying element is limited to not more than 1.00% by weight, in particular not more than 0.60% by weight, preferably not more than 0.40% by weight, in particular to ensure adequate rolling properties. In addition, Si can be used for deoxidizing the steel, if an optional use of Al, for example, should be avoided in order to avoid undesired setting z. B. of N to avoid.

Mn is an alloying element which can contribute to hardenability and is used in particular for bonding S to MnS so that a content of at least 0.20% by weight, in particular at least 0.40% by weight, is present can. Manganese reduces the critical cooling rate, which can increase the hardenability, especially in a heat treatment process. The alloying element is to a maximum of 2.00 wt .-%, in particular a maximum of 1.50 wt .-%, to ensure a good forming behavior. In addition, Mn has a strong segregation and is therefore preferably limited to a maximum of 1.30 wt .-%.

P is an iron companion, which has a strong toughening effect and is usually one of the unwanted accompanying elements. Due to its low diffusion rate, solidification of the melt can lead to strong segregations. For these reasons, the element is limited to a maximum of 0, 150 wt .-%, in particular at most 0, 110 wt .-%.

S has a strong propensity for segregation in steel and forms undesirable FeS, as a result of which it can be set by alloying Mn. The S content is therefore limited to a maximum of 0.50 wt .-%, in particular at most 0.45 wt .-%.

Pb can be alloyed up to a maximum of 0.50 wt .-%, in particular at most 0.40 wt .-%, preferably at most 0.350 wt .-%, which can lead to a smooth surface of the steel in a mechanical processing. Alloy contents above the stated upper limit would result in exceeding the legal restrictions.

Preferably, at least one of the alloying elements S, P, Pb, due to the positive influence on the machinability by forming brittle inclusions in the steel, at which chips can break during mechanical or machining machining, individually or in total from either S and P or S. and Pb or P and Pb or S and P and Pb having at least 0.020% by weight, in particular at least 0.050% by weight, preferably at least at least 0, 10 wt .-%, particularly preferably at least 0, 150 wt .-% present. Total in sum SP + S + Pb> 0.020 wt .-%.

Depending on the content, Cr may contribute to the adjustment of the strength as an optional alloying element, in particular with a content of at least 0.020% by weight. In addition, Cr can be used alone or in combination with other elements as carbide formers. Because of the positive effect on the toughness of the material, the Cr content can preferably be adjusted to at least 0.15% by weight. For economic reasons, the alloying element can be limited to a maximum of 3.0% by weight, in particular a maximum of 2.50% by weight, preferably a maximum of 2.0% by weight.

Cu can contribute to hardness increase as an optional alloying element by precipitation hardening and in particular with a content of at least 0.010% by weight. be alloyed. Cu can be limited to a maximum of 0.50 wt .-%.

Ti, Nb, and / or V may be added as optional alloying elements singly or in combination for grain refining. In addition, Ti can be used to set N. Above all, however, these elements can be used as micro-alloying elements to form strengthen keitssteigernde carbides, nitrides and / or carbonitrides. To ensure their effectiveness, Ti, Nb and / or V can be used at levels of in each case or in total at least 0.010% by weight. For complete setting of N, the content of Ti should be at least 3.42 * N. Nb is at most 0.050 wt.%, In particular at most 0.030 wt.%, Ti is at most 0.020 wt.%, In particular at most 0.0150 wt.%, And V is at most 0.40 wt. -%, in particular limited to a maximum of 0.250 wt .-%, since higher contents may adversely affect the material properties, in particular adversely affect the toughness of the first layer.

Mo can optionally be added as a carbide former to increase the yield strength and improve toughness. In order to ensure the effectiveness of these effects, a content of at least 0.010 wt .-% can be alloyed. For reasons of cost, the maximum content is limited to a maximum of 1.0% by weight, preferably a maximum of 0.70% by weight.

N, as an optional alloying element, can exert a similar effect as C because its ability to form nitrides can have a positive effect on strength. If AI is optional, aluminum nitrides can be formed to enhance nucleation and to improve the efficiency of nucleation Hamper grain growth. The content is limited to a maximum of 0.020 wt .-%. Preferably, a maximum level of 0.0150 wt% is adjusted to avoid the undesirable formation of coarse titanium nitrides in the event of an optional presence of Ti which would adversely affect toughness. In addition, when using the optional alloying element Boron this is bound by nitrogen, if the aluminum or titanium content is not high enough or not present.

Ni, which can optionally be alloyed up to a maximum of 5.0% by weight, can positively influence the deformability of the material. For reasons of cost, in particular contents of not more than 4.50% by weight, preferably not more than 4.30% by weight, are set.

B, as an optional alloying element in atomic form, retards the microstructure transformation to ferritin / bainite and improves the strength, in particular if N is bound by optionally strong nitride formers such as Al and / or Nb, and can have a content in particular of at least 0.0005 wt. -% to be available. The alloying element is limited to a maximum of 0.010 wt .-%, in particular to a maximum of 0.0070 wt .-%, since higher contents may adversely affect the material properties, in particular based on the toughness at the grain boundaries.

Sn, As, and / or Co are optional alloying elements that can be counted as contaminants, individually or in combination, unless specifically added to set specific properties. The contents are limited to a maximum of 0.050 wt.% Sn, in particular a maximum of 0.040 wt.% Sn, to a maximum of 0.020 wt.% Co, to a maximum of 0.020 wt.

0 is optional and usually undesirable, but may also be beneficial in the lowest levels in the present invention, since oxide occupancies, particularly on the release layer between the first and second layers, hinder diffusion between the deliberately differently alloyed steels, such as For example, in the German Offenlegungsschrift DE 10 2016 204 567 Al described. The maximum content of oxygen is given as 0.0050 wt%, preferably 0.0020 wt%.

H is optional and as the smallest atom on interstitial sites in steel very flexible and can lead to tears in the core especially when cooling from the hot rolling. The element hydrogen is therefore reduced to a maximum content of 0.0010% by weight, in particular of which at most 0.0006% by weight, preferably at most 0.0004% by weight, more preferably at most 0.0002% by weight are reduced.

Ca can optionally be added to the melt as desulphurising agent and for targeted sulphide addition in amounts of up to 0.0150% by weight, preferably up to 0.0050% by weight, which leads to an altered plasticity of the sulphides in the case of Hot rolling leads. In addition, the cold-forming behavior is preferably improved by the Ca addition. The described effects are effective from the level of 0.0005 wt .-%, which is why this limit can be chosen with optional use of Ca as a minimum.

AI can contribute in particular to the deoxidation, which is why optionally a content of at least 0.010 wt .-% can be adjusted. The alloying element is limited to a maximum of 1.0% by weight in order to ensure the best possible castability, preferably a maximum of 0.30% by weight, in order essentially to reduce unwanted precipitations in the material, in particular in the form of non-metallic oxidic inclusions. or to avoid which may adversely affect the material properties. For example, the content is set between 0.020 and 0.30 wt .-%. AI can also be used to tie off the nitrogen that is available in the steel as an option.

According to one embodiment, the at least second layer of the steel composite material consists of a steel having an elongation at break A ₈₀ > 10, in particular an elongation at break A ₈₀ > 15, preferably an elongation at break A ₈₀ > 20, particularly preferably an elongation at break A ₈₀ > 25.

According to one embodiment, the first layer has a material thickness of between 5% and 70%, in particular between 10% and 50%, preferably between 20% and 40%, based on the total material thickness of the steel material composite. The material thickness of the first layer of at least 5% should be ensured that a mechanical processing can be implemented exclusively in the first position. The restriction of the material thickness of the first layer to a maximum of 70% should give the steel composite material a certain malleability. The total material thickness is between 0.5 and 20.0 mm, in particular between 1.0 and 15.0 mm, preferably between 2.0 and 10.0 mm. In its simplest embodiment, the steel composite material has exactly one first layer and one second layer. Depending on the application, the composite steel material can also be designed to have at least three layers, wherein the first layer as a core layer between two cover layers, each formed from the second layer are, can be arranged. Alternatively, the second layer can be arranged as a core layer between two cover layers, which are each formed from the first layer. The cover layers may have either a symmetrical or asymmetrical structure in the at least three-layered design.

According to a further embodiment, the steel-material composite is produced by means of plating, in particular roll-cladding, preferably hot-rolled cladding, as described, for example, in German Patent DE 10 2005 006 606 B3. Reference is made to this patent, the contents of which are hereby incorporated by reference. Composite fabrication is generally known in the art.

According to a second aspect, the invention relates to a method for producing a component, wherein a steel composite material according to the invention is provided, which is shaped into a preform, in particular cold-formed, and the preform for producing a final shape or a further shape, in particular for further process steps at least partially machined in the region of the first layer. Mechanical processing is to be understood as meaning, in particular, a machining operation, for example, turning, milling and / or drilling in sections in the region of the first layer. Depending on the arrangement of the first layer on the component, for example as an accessible position, a substantially complete machining of the surface can take place. If the first layer is only partially accessible, for example if it is arranged as a core layer in the at least three-layered component, the first layer can also be machined only in the region of the front side of the component.

According to an embodiment of the method, the final shape or the further shape may be heat treated. By means of a heat treatment, further properties or improved properties can be set on the component, for example by flash annealing or hardening with optionally subsequent tempering or surface hardening in the course of carburizing or nitriding.

According to a third aspect, the invention relates to a use of a component produced by one of the aforementioned methods as a component in vehicle or metal construction, in particular in the drive train of a vehicle. The powertrain of a vehicle includes all components that transmit the engine power to the wheels. These include, starting with the engine, the assemblies of clutch and gearbox, cardan shaft, drive shafts and differentials. In the hybrid vehicles, full hybrid and plug-in, as well as the pure electric vehicles, the electric motors are added. Exemplary components may be plate carriers, rotor carriers, stator carriers, pressure plates, toothed belt wheels, donor wheels, rotor wheels and shafts.

Preferably, the use relates to all rotationally symmetrical components that still need to be machined at least in sections after a non-cutting shaping.

Short description of the drawings (Brief Description of Drawings)

In the following the invention will be explained in more detail with reference to a drawing illustrating several embodiments. Identical parts are always provided with the same reference numerals. It shows

FIG. 1) shows a first exemplary embodiment of a component according to the invention in different representations,

2), a second embodiment of a component according to the invention in different representations and

3), a third embodiment of a component according to the invention in different representations.

Description of the Preferred Embodiments (Best Mode for Carrying Out the Invention)

From commercially available flat steel products, particularly preferably steel composite materials according to the invention can be produced by means of hot-rolled plating, in particular to provide semi-finished products, which can unite opposing properties, such as play a sufficient formability with good machinability and / or shearability. For this purpose, sheet metal blanks and / or slabs from at least two layers (1, 2, 3, 4) with different properties are stacked on one another, which at least partially along their edges cohesively, preferably by means of welding to a pre-bond miteinan- are connected. The pre-bond is brought to a temperature of at least 1000 ° C and hot rolled in several steps to a composite steel material with a total material thickness, for example from 2.0 to 10.0 mm. If required, the steel composite can be further reduced to lower overall material thicknesses, in particular by means of cold rolling. 1 shows a first exemplary embodiment of a component (10) according to the invention in different representations, in a perspective view and in a sectional view according to section II and in an enlarged partial sectional view. The component (10) is formed by a composite steel material, which was produced in the course of the abovementioned hot-rolling plating and comprises a first layer (1) and a second layer (2), which are connected to one another in a material-locking manner. The first layer (1) consists of a readily machinable and / or shearable steel and the second layer (2) consists of a good deformable steel. The first layer (1) can in particular be made of a free-cutting steel according to EN 10087, for example a steel with the designation l lSMn30, or of a tempered steel according to EN 10083 with a sulfur content of at least 0.01% by weight, for example of a steel with the designation 42CrMoS4. The second layer (2) can consist of a steel with an elongation at break A ₈₀ > 10, in particular an elongation at break A ₈₀ > 15, for example from a steel with the designation DC according to DIN EN 10130, with the designation DD according to DIN EN 10111 , with the designation DX according to DIN EN 10346 or with the designation S355MC according to DIN EN 10149-2.

To produce the component (10), a substantially planar steel material composite was provided, which had a first layer (1) with a material thickness of at least 25%, based on the total material thickness of the composite steel material. Due to the percentage higher proportion of good formable steel (second layer, 2), a sufficient and complex shape can be ensured. The composite steel material was cold-formed into a preform by means of suitable forming means, not shown, and the surface of the preform was unilaterally machined by suitable means (20) to its final shape, or brought into another form for further process steps. Alternatively, the steel material composite can also be thermoformed to produce a preform if required. The cutting removal reduced the material thickness of the first layer (1) to less than half of the original material thickness of the first layer before machining. The mechanical processing does not have to take place completely on the entire surface of the first layer (1), but can also be carried out only in sections as required. Mechanical treatment may also be followed by heat treatment on the final mold or on the further mold to improve the properties. FIG. 2 shows a second exemplary embodiment of a component (10 ') according to the invention in different representations, in a perspective view and in a sectional view along section II-II and in an enlarged partial sectional view. The component (10 ') is formed in comparison to the component (10) by a three-layer steel composite material. The steel composite material comprises a second layer (2) arranged as a core layer between two cover layers, which are each formed from the first layer (1, 3).

To produce the component (10 '), a substantially planar steel material composite was provided, which had two first layers (1, 3), each with a material thickness of at least 20%, based on the total material thickness of the composite steel material. The steel composite was cold formed into a preform by means of suitable forming means not shown, and the preform on both sides, more specifically, the two surfaces of the first layer (1, 3) were machined by suitable means (20) to produce a final shape or shape , Alternatively, if required, the steel material composite can also be thermoformed to produce a preform. In order to meet the accuracy and / or surface requirements of the entire component (10 '), a cutting removal took place on both sides, the material thickness being reduced on both sides by approximately 1/4 of the original material thicknesses of the first layers (1, 3). were reduced before mechanical processing. The mechanical processing does not have to be carried out completely on the entire surface of the first layers (1, 3), but can also be carried out in sections only as required. The mechanical processing may also be followed by a heat treatment on the final mold or on the further mold to improve the properties.

FIG. 3 shows a third exemplary embodiment of a component (10 ") according to the invention in different illustrations, in a perspective view and in a sectional view according to section III-III and in an enlarged partial sectional view. The component (10 ") is like the component (10 ') also formed by a three-layer steel composite material, but with the difference that the first layer (1) as a core layer between two cover layers, each consisting of the second layer (2, 4) are formed, is arranged.

To produce the component (10 "), a substantially planar steel material composite was provided, which had a first layer (1) with a material thickness of at least 50%, based on the total material thickness of the steel material composite. The steel composite material has become a preform by means of suitable and not shown cold molded and the preform for producing a final shape from the front side of a mechanical or machining machining by means of suitable means (20) drove, wherein in the front side a circumferential groove-shaped geometry was machined into the component (10 ") was introduced. Alternatively, the steel material composite can also be thermoformed to produce a preform if required. The mechanical processing can also be followed by a heat treatment on the final shape to improve the properties.

The invention is not limited to the embodiments shown, but the individual features can be combined with each other. Particularly preferably, the component according to the invention or the component which can be produced from the steel material composite according to the invention can be used as a component in vehicle or metal construction, in particular as a component in the drive train of a vehicle, preferably in the form of a rotationally symmetrical component.

Claims

claims

1. steel composite material with at least two layers (1, 2, 3, 4) comprising at least a first layer (1, 3) of a machinable and / or shearable steel and at least a second layer (2, 4) of a moldable steel , which is materially connected to the first layer (1, 3).

2. Steel material composite according to claim 1, characterized in that the at least first layer (1, 3) in addition to Fe and production-related unavoidable impurities in wt .-% of

C: up to 0.60%,

Si: up to 1.00%,

Mn: up to 2.00%,

P: to 0, 150%,

S: up to 0.50%,

Pb: up to 0.50%,

with S P + S + Pb> 0.020% by weight

wherein the first layer (1, 3) may optionally comprise one or more of the following optional alloying elements:

optional Cr: up to 3.0%,

optional Cu: up to 0.50%,

optional Nb: up to 0.050%,

optional Mo: up to 1.0%,

optional N: up to 0.020%,

optional Ti: up to 0.020%,

optional V: up to 0.40%,

optional Ni: up to 5.0%,

optional B: up to 0.010%,

optional Sn: up to 0.050%,

optional H: up to 0.0010%,

optional As: up to 0.020%,

optional Co: up to 0.020%,

optional 0: to 0.0050%,

optional Ca: up to 0.0150%,

optional AI: up to 1.0%.

3. Steel material composite according to one of the preceding claims, characterized in that the at least second layer (2, 4) consists of a steel having a breaking elongation A ₈₀ > 10, in particular an elongation at break A ₈₀ > 15.

4. Steel material composite according to one of the preceding claims, characterized marked, that the first layer (1, 3) has a material thickness between 5% and 70%, in particular between 10% and 50% based on the total material thickness of the Stahlwerkstoffver composite.

5. Steel composite material according to one of the preceding claims, characterized marked, that the steel material composite is produced by means of plating, in particular by means of hot-rolling plating.

6. A method for producing a component (10, 10 ', 10 "), wherein a steel composite material is provided according to one of the preceding claims, the steel composite is formed into a preform and the preform for producing a final shape or another shape at least in sections in the region of the first layer (1, 3) is mechanically processed.

7. The method according to claim 6, characterized in that the final shape or the further form is heat treated.

8. Use of a component produced according to one of claims 6 to 7 as a component in vehicle or metal construction, in particular in the drive train of a vehicle.