Abstract
The disclosure is related to a body component or chassis component for a motor vehicle having at least one surface segment composed of a three-layer sheet-metal composite having a central layer and two outer layers, which bound the central layer on the outside and which are integrally joined to the central layer face to face. The outer layers are composed of a stainless steel alloy having a microstructure selected from the group of ferritic, austenitic, or martensitic microstructure and the central layer is composed of a heat-treatable steel alloy, and the body component or chassis component has a bending angle of greater than 80, determined in the plate bending test according to VDA 238-100, having an Rp0.2 yield strength of greater than 900 MPa.
Claims
1. A body component or chassis component for a motor vehicle, comprising at least one surface section consisting of a triple-layer laminated metal sheet having a center layer and two external layers which bound the center layer on the outside and are connected over an extensive area and materially to the center layer, wherein the external layers are composed of a rust-resistant steel alloy with a microstructure selected from the group consisting of ferritic, austentic or martensitic microstructures and the center layer is composed of a heat-treatable steel alloy, and the body component or chassis component has a bending angle greater than 80, determined in the plate bending test according to VDA 238-100:2010, with an Rp0.2 proof stress greater than 900 MPa.
2. (canceled)
3. The body component or chassis component as claimed in claim 1, wherein the bending angle is greater than 95, and the Rp0.2 proof stress is greater than 950 MPa.
4. The body component or chassis component as claimed in claim 1, wherein the bending angle is greater than 90, in particular greater than 100, preferably greater than 110.
5. The body component or chassis component as claimed in claim 1, wherein the product of the bending angle and the Rp0.2 proof stress is between 90 000 MPa and 180 000 MPa.
6. The body component or chassis component as claimed in claim 1, wherein the center layer of a surface section has a microstructure with at least 80 percent martensite, and the tensile strength Rm within the surface section is greater than 1300 MPa.
7. The body component or chassis component as claimed in claim 1, wherein the center layer of a surface section has a microstructure consisting of tempered martensite, which makes up at least 80 percent, or a hybrid microstructure comprising at least 70 percent ferrite and perlite, with the remainder being martensite and/or residual austenite and/or bainite.
8. The body component or chassis component as claimed in claim 1, wherein the body component or chassis has a second surface section is a triple-layer laminated metal sheet, with a second center layer with a microstructure selected from a group consisting of a hybrid microstructure containing at least 80 percent ferrite and perlite or a hybrid microstructure containing at least 70 percent of ferrite and perlite and residual percentages of martensite and/or residual austenite and/or bainite.
9. The body component or chassis component as claimed in claim 1, wherein a surface section with the triple-layer laminated metal sheet has a total thickness, and one of the external layers has a thickness of at least 3 percent (%) and at most 15 percent (%) of the total thickness, preferably 4 percent (%) to 10 percent (%) of the total thickness of said surface section.
10. The body component or chassis component as claimed in claim 8, wherein the second surface section is a triple-layer laminated metal sheet, and the first center layer and the second center layer each have a thickness, and the thickness of the first center layer differs from the thickness of the second center layer.
11. The body component or chassis component as claimed in claim 8, wherein the surface sections (2, 3) are butt welded to one another.
12. The body component or chassis component as claimed in claim 8, wherein the body component or chassis component has a second surface section composed of a stainless steel alloy, and the surface sections are butt welded to one another.
13. The body component or chassis component as claimed in claim 12, wherein that the laminated metal sheet has a total thickness in the first surface section, and the laminated metal sheet has a total thickness in the second surface section, wherein the total thicknesses differ from each other by at least 10 percent, in particular between 20 and 100 percent.
14. The body component or chassis component as claimed in claim 1, wherein the body component or chassis component has a rim, and, at least in some sections, the rim is surrounded at one end, in the surface section with the triple-layer laminated metal sheet, by an external layer, such that the end of the center layer is screened from the environment by the external layer.
15. The body component or chassis component as claimed in claim 1, wherein the body component or chassis component is a door pillar, in particular a center pillar or a roof frame, sill board, bumper crossmember, longitudinal member, floor crossmember, transverse link, longitudinal link, stabilizer, twist beam or axle carrier of the motor vehicle.
16. The body component or chassis component as claimed in claim 1, wherein the body component or chassis component is a door pillar or a roof frame with a respective rim, wherein the second surface section is arranged at least in sections in the rim.
17. A method for producing a body component or chassis component with the features of claim 1, characterized by supplying a sheet metal blank comprising at least one surface section made of a triple-layer laminated metal sheet having a center layer made of a heat-treatable steel alloy and respective external layers which bound the center layer and are composed of a rust-free steel alloy, heating at least the laminated metal sheet to the austenitization temperature, hot forming the sheet metal blank in a press forming die cooled at least in some regions, and at least partially hardening the formed sheet metal blank in the press forming die or in a subsequent cooling die stage.
18. The method as claimed in claim 17, wherein the hot forming and hardening of the sheet metal blank is carried out in or by means of a single press having a plurality of die stages.
19. The method as claimed in claim 17, wherein the heating and hot forming and optional hardening of the sheet metal blank is carried out in a single press having a plurality of die stages.
20. The method as claimed in claim 17, wherein the heating is carried out within 30 seconds, preferably within 20 seconds, in particular within 10 seconds, and/or the heating is carried out without a protective gas atmosphere.
21. The method as claimed in claim 17, wherein component trimming or piercing is carried out after hot forming and hardening, in particular in a subsequent die stage of the press, and component trimming and/or piercing is preferably carried out after the die quenching.
22. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] For an understanding of embodiments of the disclosure, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:
[0057] FIGS. 1a and 1b illustrate body components and chassis components in accordance with an exemplary embodiment;
[0058] FIG. 2 illustrates an exemplary embodiment of a triple-layer laminated metal sheet for a surface section of the body component or chassis component;
[0059] FIG. 3 illustrates a body component in accordance with an exemplary embodiment;
[0060] FIG. 4 illustartes a second embodiment of a triple-layer laminated metal sheet for a surface section of the body component or chassis component;
[0061] FIG. 5 illustrates a third embodiment of a triple-layer laminated metal sheet for a surface section of the body component or chassis component;
[0062] FIGS. 6a and 6b illustrate body components in accordance with an exemplary embodiment;
[0063] FIG. 7 illustrates a triple-layer laminated metal sheet for a surface section of the body component or chassis component in accordance with an exemplary embodiment;
[0064] FIG. 8 illustrates a triple-layer laminated metal sheet for a surface section of the body component or chassis component in accordance with an exemplary embodiment;
[0065] FIG. 9 illustrates a triple-layer laminated metal sheet for a surface section of the body component or chassis component in accordance with an exemplary embodiment;
[0066] FIG. 10 illustrates a body component or chassis component according to an exemplary embodiment in a rim cutout;
[0067] FIG. 11a illustrates a method sequence for carrying out the production method in accordance with an exemplary embodiment;
[0068] FIG. 11b illustrates a modification of the method sequence of FIG. 11a;
[0069] FIG. 12 illustrates an alternative method sequence for carrying out the production method;
[0070] FIGS. 13a and 13b illustrate top and cross sectional views of a body component in accordance with an exemplary embodiment;
[0071] FIGS. 14a and 14b illustrate the result images of a corrosion test for a) a component sample according to an exemplary embodiment, and b) a comparison sample according to the prior art;
[0072] FIG. 15 is a diagram showing the mechanical characteristics of tensile strength;
[0073] FIG. 16 is a diagram showing the bending angle of a body component;
[0074] FIG. 17 is a diagram showing the results for a component made of steel; and,
[0075] FIG. 18 is a diagram showing the results for a component made of steel.
[0076] In the Figures, the same reference signs are used for identical or similar components, even if a repeated description is omitted for reasons of simplicity.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0077] Some embodiments will be now described with reference to the Figures.
[0078] FIG. 1 shows two advantageous use examples for a body component and chassis component 1 according to the invention, in each case in a top view and cross-sectional illustrations.
[0079] FIG. 1a) shows a center pillar 20 for the side structure of a motor vehicle, which center pillar is insertable between sill board and roof frame and serves above all for the overall stability of the vehicle body and for the dissipation of collision energy and protection against intrusion during a side impact.
[0080] FIG. 1b) illustrates a transverse link 30 of a wheel suspension of a motor vehicle chassis.
[0081] Both examples illustrate body components or chassis components 1 made from sheet metal and which have been formed three-dimensionally by means of die forming. Both the center pillar 20 and the transverse link 30 comprise at least one surface section 2 comprising a triple-layer laminated metal sheet 10 with, as FIG. 2 shows in more detail, a center layer 11 and two external layers 12, 13 bounding the center layer 11 on the outside, wherein the external layers 12, 13 are composed of a rust-resistant, in particular ferritic steel alloy and the center layer 11 is composed of a heat-treatable steel alloy. The tensile strength Rm within the surface section 2 with the triple-layer laminated metal sheet 10 is more than 1300 MPa.
[0082] A detail which is shown in enlarged form in FIG. 2 and describes the construction of the triple-layer laminated metal sheet 10 in more detail is indicated in each of sections B and C.
[0083] FIG. 2 shows a first embodiment of the triple-layer laminated metal sheet 10 for a surface section 2 of the body component or chassis component 1 according to the invention, partially in cross section. A center layer 11 of the surface section 2 is bounded on its upper side 7, which is located at the top in the plane of the image, by an external layer 12 and is bounded on its lower side 8, which is located at the bottom in the center of the image, by a further external layer 13. There is a metallurgical connection between the center layer 11 and the external layers 12, 13, and therefore detaching of the external layers 12, 13 from the center layer 11 is prevented, but the weldability, deformability and other mechanical processing capability are possible in a very simple manner. The laminated metal sheet 10 has a total thickness D2 and a thickness of the center layer Dm and a thickness Da of the external layer 12. The external layers 12, 13 are both of identical thickness here.
[0084] FIG. 3 illustrates a body component 1 according to the invention in the form of the center pillar according to FIG. 1 in a modified embodiment. The center pillar 20 here is formed from a first surface section 2 comprising a triple-layer laminated metal sheet 10 in an upper partial region 21 of the center pillar 20 and from a second surface section 3 comprising a triple-layer laminated metal sheet 15 in a second partial region 22 of the center pillar. The second partial region 22 of the center pillar 20 runs approximately to just below a door lock connection for a vehicle door (not shown). A weld seam 40 is formed between the first surface section 2 and the second surface section 3, wherein the two surface sections 2, 3 are joined in a manner abutting against each other, in particular before a three-dimensional die shaping to form the body component 1. In the cross section B-B level with the weld seam 40, the detail of the laminated metal sheet 10, 15, which is considered in more detail in FIGS. 4 and 5, is indicated.
[0085] The construction of the laminated metal sheet according to FIG. 3, which has a center layer 16 composed of a low-alloyed steel alloy and external layers 17, 18 composed of a ferritic, rust-resistant steel alloy, in the second surface section 3 can be seen in FIG. 4. The two surface sections 2, 3 are connected to each other via the weld seam. The external layers 12, 13 of the first surface section 2 correspond in respect of the material to the external layers 17, 18 of the second surface section 3. As in the case of the laminated metal sheet according to FIG. 2, there is also a metallurgical connection between the center layer 11 and the external layers 12, 13 here. In addition, the external layers 17 and 18 are firmly connected to the center layer 16 metallurgically and permanently. This laminated metal sheet has a uniform total thickness D2.
[0086] An alternative embodiment of the surface sections 2, 3 of the center pillar 20 from FIG. 3 can be seen in FIG. 5. The second surface section 3 here has a single homogeneous layer composed of a ferritic rust-resistant steel alloy. The external layers 12, 13 of the first surface section 2 correspond in respect of the material to the steel alloy of the second surface section 3. As in the case of the laminated metal sheet according to FIG. 2, there is also a metallurgical connection here between the center layer 11 and the external layers 12, 13. The two surface sections 2, 3 are already welded to each other before the shaping to form the body component or chassis component 1 and are then formable jointly. The second surface section 3 is arranged in the vehicle in what is referred to as the dry region, and consequently outside regions at risk of corrosion. The second surface section 3 comprising rust-resistant ferritic steel alloy is heated during the heating of the sheet metal blank preferably below 700 C. such that formation of scaling does not occur in this section.
[0087] According to the invention, in addition to a B pillar, another body component or chassis component can have, next to a triple-layer laminated metal sheet in a first surface section, a more ductile, particularly corrosion-loaded second surface section composed of a stainless steel alloy.
[0088] FIG. 6a shows a body component 1 according to the invention in the form of the center pillar according to FIGS. 1 and 3 in a modified embodiment. The center pillar 20 here is formed from a first surface section 2 comprising a triple-layer laminated metal sheet 10 in an upper partial region 21 of the center pillar 20 and from a second surface section 3 comprising a triple-layer laminated metal sheet 15 in a second partial region 22 of the center pillar. The second partial region 22 of the center pillar 20 runs approximately as far as just below a door lock connection for a vehicle door (not shown). A transition region 41 is formed between the first surface section and the second surface section 3, wherein the two surface sections 2, 3 are in each case made in one piece and with a unitary material in the individual layers, or, analogously to the embodiment according to FIGS. 3 and 4, are welded. In the latter case, the transition region 41 can correspond to the weld seam in respect of the layer thereof.
[0089] The second surface section 3 has greater ductility and a lower tensile strength in its center layer 16, illustrated in FIGS. 7 to 9, then in the first surface section 2, which counters a delayed formation of cracks and associated problems in the event of a side impact and permits a targeted deformation, in the case of the center pillar 20, in a vehicle seat region which is not hazardous for the occupant.
[0090] In contrast to FIG. 6a, FIG. 6b shows a center pillar 20 with a second surface section 3 which, in addition to the second partial region 22, also extends over part of the rims 42 of the first partial region (at the top in the plane of the image) of the center pillar 20. Furthermore, the center pillar 20 has a plurality of connection points 43 for fastening to a vehicle sill board. A further surface section 4 which in turn has greater strength and lower ductility in comparison to the second surface section 3 extends below the second surface section 3 in the second partial region 22. A further transition region 41 is formed between the two surface sections 2, 3.
[0091] The detail which is considered in more detail in FIGS. 7 and 9 is indicated in the cross section B-B.
[0092] A layer build-up of the alternative embodiments as per the center pillar 20 and 20 from FIG. 6 can be seen in FIG. 7. The first surface section 2 has the center layer 11 which is bounded upward and downward by two external layers 12 and 13. The first surface section 2 has a first center layer 11 of an ultra-high-strength microstructure with at least 80 percent martensite, which has been achieved by hot forming and die quenching of a heat-treatable steel alloy, wherein the tensile strength within the first surface section comprising a triple-layer laminated metal sheet is greater than 1300 MPa. The body component or chassis component 1 in the form of the center pillar 20 or 20 has a second surface section 3 composed of a triple-layer laminated metal sheet 15, wherein the second surface section has a second center layer 16 with a microstructure selected from a group consisting of tempered martensite, which makes up at least 80 percent, or a hybrid microstructure comprising at least 70 percent ferrite and perlite, with the remainder being martensite and/or residual austenite and/or bainite. With regard to the material, the surface sections 2, 3 correspond to each other in the individual layers, wherein the external layers 12, 13, 17, 18 are each composed of a ferritic rust-resistant steel alloy.
[0093] A transition region 41 in the center layer between the first and the second center layers has a width B1 which is between 10 mm and 150 mm, but preferably below 50 mm since a state which is mechanically difficult to determine and is inhomogeneous is present in the transition region 41. Of course, said layer build-up of the described center pillar 20, 20 is also transferrable to other body components and chassis components, as present in claim 15, wherein a targeted design of the component appropriate to the load is expedient.
[0094] A layer build-up of an alternative embodiment of the invention is apparent in FIG. 8. As before, this involves a detail in cross section for illustrating the relevant component properties.
[0095] A first surface section 2 has the center layer 11 which is bounded upward and downward by two external layers 12 and 13. The first surface section 2 has a first center layer 11 of an ultra-high-strength microstructure, with at least 80 percent martensite, wherein the tensile strength within the first surface section 2 comprising a triple-layer laminated metal sheet 10 is greater than 1300 MPa. The body component or chassis component 1 has a second surface section 3 of the same triple-layer laminated metal sheet 15 in terms of material, wherein the second surface section 3 has a second center layer 16 with approximately the same metallic microstructure. With regard to the material, the surface sections correspond to one another in the individual layers, wherein the external layers 12, 13, 17, 18 are each composed of a ferritic rust-resistant steel alloy. It is also possible here for the jump in thickness to be formed only on one side, for example on the upper side, whereas the opposite lower side is flat. This facilitates subsequent heat forming since better die contact is produced. In addition, it results in a sheet-like welding plane.
[0096] A transition region 44 between the first and the second surface section 2, 3 has a width B2 which is between 50 millimeters (mm) and 250 mm, but preferably below 200 mm since the coupling to further components is made difficult in uneven sections. It can be seen that the total thickness D3 of the laminated metal sheet 15 in the second surface section 3 is greater than the total thickness D2 of the laminated metal sheet 10 in the first surface section 2, wherein the ratios of the thickness of the layers with respect to one another within a laminated metal sheet do not change.
[0097] Of course, it is possible for the body component or chassis component 1 to comprise further surface sections which adjoin the second surface section and permit a further increase in the overall thickness and therefore a strengthening of the design appropriate to the load. It should also be noted that the different thickness is preferably already present before the press forming into the three-dimensional component geometry.
[0098] FIG. 9 finally illustrates an alternative embodiment and a combination of the embodiments of FIGS. 7 and 8. A first surface section 2 of the total thickness D2 of a center layer 11 and two external layers 12 and 13 merges via a transition region 44 of width B2 into a second surface section 3 of the total thickness D3, wherein the second surface section 3 in turn has a center layer 16 with a thickness Dm3 and two external layers 17 and 18, and the center layer 16 has an ultra-high-strength microstructure with at least 80 percent martensite. By contrast, the center layer 11 of the first surface section 2 has a more ductile microstructure selected from a group consisting of tempered martensite, which makes up at least 80 percent, and a hybrid microstructure comprising at least 70 percent ferrite and perlite, with the remainder being martensite and/or residual austenite and/or bainite. A transition region 41 of the width B1, which is formed only over part of the width B2 of the transition region 44, can also be seen. The transition region 41 which is undefined in respect of its mechanical properties and its microstructure composition is accordingly smaller than the transition region 44 which is marked by its thickness inconsistency. The result is a body component or chassis component 1 having very good load-appropriate design potential in respect of a targeted deformation profile, energy absorption capability and good couplability to the vehicle body or to other add-on parts by welding, adhesive bonding, riveting and/or screwing.
[0099] FIG. 10 illustrates part of the cross section of a body component or chassis component 1 according to the invention comprising a triple-layer laminated metal sheet 10 with a rim 42. At least in some sections, the rim 42 is surrounded at its end 9, in the surface section 2 with the triple-layer laminated metal sheet 10, by an external layer 12, such that the end 9 of the center layer 11 of the rim 42 is screened from the environment U by the external layer 12 and by the external layer 13. As in the preceding embodiments, the external layers bound the center layer 11 on the upper side 7, which is located at the top in the plane of the image, and on the lower side 8, which is located at the bottom in the center of the image. This can be brought about, for example, in such a manner that, when the laminated metal sheet 10 is trimmed before or after the press forming, cutting with combined or subsequent rolling of the external layer 12 of the rim 42 takes place in the direction of the other external layer 13, by pushing material from the upper side 7 over the end 9 of the rim 42.
[0100] FIG. 11a shows a press 50 for carrying out the methodological part of the invention for producing body components or chassis components 1. First of all, one or more sheet metal blanks 5 are supplied comprising at least one surface section made of a triple-layer laminated metal sheet having a center layer made of a heat-treatable steel alloy and two external layers bounding the center layer on the outside. Subsequently, the laminated metal sheet is heated at least in sections to the austenitization temperature in the press 50 by means of contact heating 51 by means of at least one heatable contact plate 56. During the heating, the contact plate 56 touches the external layers of the laminated metal sheet of the sheet metal blank, wherein at least one surface section of the sheet metal blank is heated within a very short time to the austenitization temperature. This involves the recrystallization temperature of the center layer of the laminated metal sheet with a heat-treatable steel alloy in order to permit the subsequent hardening. Subsequently, the hot sheet metal blank is transferred into a press forming die 52, which is cooled at least in regions, and the hot forming of the sheet metal blank 5 is carried out therein. The sheet metal blank 5 is also already cooled somewhat here. If a previously homogeneously austenitized sheet metal blank 5 is formed in a press forming die 52 which is heated in some regions, a reduced cooling speed can optionally be brought about in a second surface section, and therefore the critical cooling rate for converting the martensite of the microstructure in said second surface section is eliminated.
[0101] Subsequently, the press-formed sheet metal blank is transferred into a subsequent cooling die stage 53 where the formed sheet metal blank is at least partially hardened. After a further transfer into a third die stage 54, final cooling to approximately ambient temperature takes place, but so does at least complete hardening of at least the first surface section.
[0102] Instead of three cooled die stages 52, 53, 54, as in FIG. 11a), dispensing with the final cooling die stage 54 and already finishing the hardening of a surface section in the first cooling die stage 53 can also be envisaged. However, at greater total thicknesses of the sheet metal blank 5 or at a particularly high cycle time of the press 50, this is possible only to a limited extent. This is illustrated with reference to the press 50 in FIG. 11b).
[0103] Trimming and piercing of the formed, but still unhardened component (not illustrated) can also take place by means of the press forming die 52 or the first cooling die stage 53. A decisive advantage of the methods according to the invention is that, by means of the external layers of ferritic or austenitic or martensitic rust-resistant steel alloy, scaling or oxidation during the heating and during hot forming are prevented and therefore a complicated coating, final cleaning of the surface, surface errors and a protective gas housing of the press or contact heating is avoided.
[0104] FIG. 12 shows a press 50 for an alternative realization of the methodological part of the invention for producing body components or chassis components 1. First of all, one or more sheet metal blanks 5 are supplied which comprise at least one first surface section made of a triple-layer laminated metal sheet having a center layer made of a heat-treatable steel alloy and two external layers bounding the center layer. Subsequently, the laminated metal sheet is heated in sections to the austenitization temperature in the press 50 by means of contact heating 51 between at least one heatable contact plate 56. The two contact plates 56 shown here touch the external layers of the laminated metal sheet of the sheet metal blank (not illustrated) during the heating, wherein one or all of the surface sections of the sheet metal blank are heated within a very short time. Subsequently, the sheet metal blank heated in this manner is transferred to a tempering stage 55 such that either the homogeneously heated sheet metal blank 5 is cooled down in a second surface section from an austenitization temperature to less than 700 C., or a surface section is heated from less than 700 C. to at least the austenitization temperature. The tempering stage can in turn have contact plates for heating and/or cooling, which are adjusted to the required temperature by burners, inductors or resistance heating. The sheet metal blank which is thus tempered differently in sections is placed into a cooled press forming die stage 52 and heat forming of the sheet metal blank is carried out therein. The sheet metal blank 5 is also already somewhat cooled here. Subsequently, the press-formed sheet metal blank is transferred into a subsequent cooling die stage 53 where the formed sheet metal blank is at least partially hardened while a second surface section is not hardened here. Trimming and the piercing of the formed but still unhardened component (not illustrated) can also take place by means of the press forming die 52.
[0105] FIG. 13a) shows a further embodiment of the invention in the form of a body component 1 which is round in cross section and is composed of a sheet metal blank or a sheet metal strip, in a top view. This is an A pillar 25 with a lower partial region 22 which is curved in the plane of the image and with a rectilinear upper partial region 21 which is wider in cross section. Various cross-sectional geometries which can be used for the A pillar of FIG. 13a) can be seen in FIGS. 13b) to 13d). A respective weld seam 23 which runs in the axial direction of the component 1 adjoins the component 1, which is designed as a hollow profile, at a rim 42, 42.
[0106] In FIG. 13b), the component 1 has two rims 42 which are in contact opposite each other in parallel and are coupled materially by means of the weld seam 23. The rim here is a two-walled flange.
[0107] It can be seen in FIG. 13c) that a rim 42 is formed so as to be in contact with its end 9 against a side surface of a second rim 42 and is joined materially by a weld seam 23. The rim 42 here is a single-walled flange.
[0108] As can be seen in FIG. 13d), two rims 42 butt with their respective ends 9 against each other, thus resulting in a flangeless component. The forming takes place here by means of roll forming or U-O forming and subsequent hydroforming and quench hardening. The cross-sectional configuration according to FIG. 13d) can also be transferred to many chassis components, such as twist beam axles, transverse links.
[0109] FIG. 14a) shows the result of a corrosion test after 48 hours by salt spray testing for a die-quenched steel sheet made from Usibor material. Progression of corrosion over an extensive area over the component surface and in the rims can be seen.
[0110] By contrast, FIG. 14b) shows the result of a corrosion test after 1000 hours for a steel sheet die-quenched according to the invention. Pronounced progress of the corrosion can be seen only in the rims.
[0111] The foregoing description of some embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The specifically described embodiments explain the principles and practical applications to enable one ordinarily skilled in the art to utilize various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. Further, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as described by the appended claims.
