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Steel research international 2200327 (2022). doi:10.1002/srin.202200327, Published by Wiley-VCH-Verl., Weinheim

This work presents the results obtained from the experimental investigations performed on the production of steel clad strips by vertical twin-roll strip casting with a combination of the austenitic stainless steel 1.4301 and the carbon steel 1.1248. This production method is based on the introduction of a solid strip between the casting rolls, where the joining with a solidifying melt takes place. For the first time this process is used to combine two steel alloys. In comparison to other methods such as cold or hot roll bonding it requires a shorter production route as one of the alloys can be directly cast. Micrographies of the strip cross-section show that the material and layer thickness combination adopted in this work lead to a non-uniform local remelting of the solid strip at the joining interface. The micrographic appearance of the interface differs from the one reported in the literature for other cladding processes. Twenty-three percent of the joining surface is characterized by a wavy interface indicating a local remelting of the introduced solid strip. Seventy-three percent of the joining surface exhibits a flat interface. The remaining four percent of the surface is classified as joining defect. Diffusion takes place between the two alloys and is characterized by electron probe microanalysis. Bending tests are performed on the clad strip and shear tests with an optimized shearing surface are used to measure the mechanical resistance of the joining between the two materials. The average shear resistance of the joining is 218 MPa with a standard deviation of 29 MPa.

The tribological properties of lubricated machine elements can be improved by micro lubrication pockets. Depending on the application's tribological system, the pocket dimension needs to be adjusted to achieve an optimum in friction and wear reduction. With respect to production efficiency, a forming operation would be suited to manufacture these pockets. In this work, finite element models were developed to study the steps of the hot micro-coining process: heating, cutting, and coining of micro lubrication pockets. Experiments have been conducted to validate the models and to investigate the emissivity and heat transfer coefficient between tool and specimen by inverse modeling. It was found that the results of the simulations agree well with the experiments as long as the elastic tool deformation is taken into account, which influences the process time. Thus, suitable process parameters and limits have been determined for the coining of hemispherical lubrication pockets in stainless steel AISI 304. An initial forming temperature above 540 °C is recommended to avoid plastic deformation of the die. Complete form filling was achieved at a normalized pressure of three due to the high specimen temperature of 785 °C.

© 2014 Wiley-VCH Verlag GmbH & Co. KGaA. The industry scale production of heavy steel plates is performed in plate mills using reversing mill stands and roll schedules with 30 or more passes. Ideal pass scheduling is dependent on a precise prediction of the roll force in each pass. To obtain these forces process models based on the slab theory together with semi-empirical material models are most frequently used. The material parameters necessary to calibrate the models for a specific steel grade are conventionally generated on a lab scale via time-consuming and expensive compression tests. This paper will introduce a concept that allows obtaining the material model parameters directly from the rolling process on an industrial scale by an inverse modeling technique. In this context, the parameters of the material model are adjusted according to the current offset between measured and calculated roll forces. The adjustment is enabled by a non-linear optimization that aims for a minimum deviation between measured and calculated roll forces for each pass. Several results gathered in an optimization run with industrial data of about 2650 produced plates are presented. The concurrence between measurement and prediction using the optimal parameters is in detail shown for three different schedules. In summary, inverse modeling seems to allow utilizing data of past rolling processes to determine material model parameters with high accuracy.

By using fast calculation models, the equivalent strain, temperature, and average austenitic grain size in the center of an ingot can be determined. When used in an online process monitor by coupling with a measuring system, these models are fast enough to visualize the current state of an ingot during forging. Based on a model forging process, the use of the program is demonstrated. Comparing results from metallography of the forged billet with the calculated grain size, a good agreement could be achieved (deviation of 6–24%). Even before the forging process, the presented automatic pass schedule optimization can be applied. Through this, a process could be optimized concerning a high homogeneous equivalent strain and a low number of strokes. As result of the optimization, an increasing grain size and temperature could be observed. Thus it could be useful to change other process parameters, like lowering the furnace temperature.

The conventional approach to model static recrystallization (SRX) kinetics is to use the well-known Kolmogorov–Johnson–Mehl–Avrami (KJMA) equation. However, the validity of KJMA kinetics depends on whether the real recrystallization process follows the assumptions made in the derivation of the KJMA kinetics, which are a random distribution of nucleation sites, isotropic growth and a constant growth velocity. When these assumptions are violated the KJMA kinetics loose their physical meaning and turn into an empirical formula with limited predictive capability. In such cases, phase field (PF) method can be an alternative to the KJMA model, since it is based on irreversible thermodynamics. An effective strategy to apply the PF method to static recrystallization problems is coupling it to a deformation model though which the prior deformation process is simulated. For that purpose crystal plasticity finite element method (CPFEM) can be employed. In this work, an example of a weak coupling strategy was applied to a steel grade of commercial interest (X60Mn23 TWIP steel) for which KJMA equation is invalid. Deformation of a Voronoi type representative volume element was modeled using a Crystal plasticity finite element formulation after determining the material parameters of a strain hardening model from macroscopic experiments. Afterwards, the deformed structure was transferred on to a finite difference grid with a dedicated mapping scheme, which was then used as input for phase field simulation. Finally, the simulation results were compared with the results of stress relaxation tests. It was found that although the grain morphology of the simulation differed from the experimental results, the coupled simulation strategy was able to mimic the main features of the static recrystallization (SRX) kinetics.

A new process idea to create hierarchical surface structures is based on the combination of micro-coining and laser interference patterning. Micro-coining already proved to be a high precision cold bulk metal forging process which allows for the production of small surface structures in the range of 20–200 µm while fulfilling high requirements related to the geometrical accuracy of those structures. In addition to that, laser interference patterning utilizes interfering laser beams from a pulsed solid state Nd: YAG laser to generate precisely defined surface topographies with a long-range order on the micron-scale. For the first time, initial results of a process combination consisting of micro-coining and laser interference metallurgy to induce hierarchical surface structures will be presented. The results highlight the advantages of the sequence micro-coining prior to laser interference patterning due to smaller defects in contrast to the inverted process cycle. Additionally, process limitations such as shadowing which may result from steep flank angles of the coined structures and surface roughness effects are discussed by the use of finite element simulations within this research work.

Blechumformung ist traditionell ein hochaufwendiger Prozess, der teurer Werkzeuge und Formen wie Gesenke oder Patrizen und zugehoriger Stempel bedarf, die erst bei hohen produzierten Stuckzahlen rentabel werden. Aus diesem Grund beschrankt sich im Bauwesen der Einsatz umgeformter Stahlprodukte bisher auf die Verwendung von Halbzeugen wie z. B. Walzprofilen. Die inkrementelle Blechumformung (IBU), ein neuartiges Umformverfahren, arbeitet auf ganz andere Weise. Statt eines einstufigen Pressvorgangs, bei dem das Blech in Form gebracht wird, fahrt ein Umformwerkzeug die Bauteilkontur in einem sequenziell ablaufenden Prozess mit lokaler Verformung ab, der sich mit einfachen Mitteln an die individuell herzustellenden Blechformen anpassen lasst. Die IBU stellt insofern einen hochflexiblen Prozess dar, der es moglich macht, Serien von geometrisch unterschiedlichen Bauteilen bei hoher Effizienz zu fertigen. Sie verspricht ein ideales produktionstechnisches Mittel fur die Umsetzung des Leichtbauprinzips von Raumfaltwerken und mehrlagigen Faltungen zu sein, auf dessen Basis selbsttragende Hull- und Fassadenkonstruktionen aus Feinblech fur die Architektur und den Ingenieurbau gebaut werden konnen. Die tatsachlichen Eigenschaften und Bedingungen der konstruktiven und praktischen Umsetzung einer mit Hilfe der IBU hergestellten, frei geformten zweilagigen Hullflache wurde im Rahmen eines Forschungsprojekts zwischen dem Lehrstuhl fur Tragkonstruktionen (TRAKO) und dem Institut fur Bildsame Formgebung (IBF) an der RWTH Aachen untersucht. Free-formed, self-supporting folding structure made of metal sheets using the incremental sheet forming (ISF). Sheet forming is traditionally a costly process that requires expensive tools as well as forms such as winds or dies with customized punches, which are only profitable when producing high quantities. However, the incremental sheet forming (ISF), a novel forming technique, works highly differential. In contrast to the common single-stage jacking process, the incremental metal forming is a sequential process in which a forming instrument circumscribes the part contour and warps the sheet repeatedly. This process can easily be adjusted to a variety of individual thin sheet forms. In view of this fact, the ISF is a highly flexible process that allows to craft series of geometrically different components efficiently. ISF appears to be an ideal production-related instrument to realize the principle of lightweight constructions in space folding structures and multilayer folding structures that form the basis of self-supporting building envelopes or facades made of thin sheet. The actual characteristics and conditions of the constructive realization of a free-shaped, two-layered envelope formed with the incremental metal forming procedure has been analyzed during a research project between the Chair of Structures and Structural Design (Lehrstuhl fur Tragkonstruktionen – TRAKO) and the Institute of Metal Forming (Institut fur Bildsame Formgebung – IBF) of the RWTH Aachen University.

To fully exploit the potential of sheet and profiles, various technologies to produce tailored blanks and profiles have been developed [1,2]. In earlier work [3] it has been shown that Strip Profile Rolling (SPR) can be used to produce metal strips with a predefined thickness distribution across the width of the strip. Building upon this knowledge, in two subsequent papers the extended goal of the project is presented. Therein is demonstrated that Strip Profile Rolling can be applied very effectively using a combination of roll forming (part 1) as well as further processing by roll forming (see part 2) to allow for the production of profiles with varying wall thickness in their cross section. To achieve the goal of part 1, a numerical model describing SPR was developed and used to study the influencing process parameters on spread and bulge formation. As a result of this parametric study, an optimized roll design and rolling sequence was developed to produce a demonstrator strip on a 12 stand roll forming mill manufactured by the company Dreistern [4]. Starting with a conventional strip out of DC01 steel (width 170 mm, thickness 2.5 mm), 29 rolling passes were necessary to achieve the desired geometry (width 186 mm, thickness 2.5 mm with a longitudinal groove being 64 mm wide where the thickness is reduced to 1.5 mm). In the second part of the process chain the coils produced by Strip Profile Rolling were successfully roll formed into a circular tube of 60 mm.

In the production of high-manganese TRIP and TWIP steels, significant micro-segregation effects are observed after solidification. Homogenization can be achieved by heat treatment followed by deformation at a significant time and effort (forging, annealing, hot rolling). In an attempt to achieve the best homogeneous microstructure and reduced thermomechanical processing, the cast alloy is treated by electroslag remelting (ESR). After a simple hot rolling procedure with a thickness reduction of 90% and without further heat treatment, micro-segregation of manganese can be reduced to about 5 wt%. There is a potential to achieve even lower values with further optimization of the ESR process and an adapted thermomechanical processing.

Summary and OutlookThe newly designed ternary Fe-Mn-C TWIP steel Fe-Mn23-C0.6 was analyzed using hot compression testing.Both the flow behavior and microstructure evolution wereinvestigated in the temperature range from 900 8Cto12008Cforvariousstrainratesfrom0.1s 1 to10s 1 .Basedon the characteristic form of the temperature compensatedflowcurvesanempirical-phenomenologicalmaterialmodelwas established to model theflow stress taking intoaccountdynamicrecrystallization.Themainresultscanbesummar-ized as follows:1. The flow curves at higher temperatures and lower strainratesexhibitasinglepeaktypedynamicrecrystallization.The characteristic strains e p , e c , e ss can be described asfunctions of Zener-Hollomon-parameter Z. The ratio ofcritical to the peak strain is approximately 0.55.2. Because of the interrelations of the equations in theintroduced model, a two step parameter identificationprocess was developed. At first, the parameters in theindividualmodelequationsaredetermineddirectlyfromexperimentaldata.Then,aninverseanalysisisperformedinwhichthecompressiontestsaresimulatedusingafiniteelement model to which the microstructure model iscoupled.3. Temperature compensation of the flow curves directlyobtainedfromthemeasurementisimportant,especiallyathigherstrainratesandlowerdeformationtemperatures.Itcan change the characteristic form of the flow curvedistinctively.4. Basically, the established model can describe the flowstressintheentirerangeofZvaluesthatwerecoveredbythe compression tests with acceptable tolerance. Incontrast reliable prediction of recrystallized austenitegrain size can only be achieved at higher temperatures.Outlook. Since the softening behavior at high tempera-tures is quite different from that at lower temperatures, it isimpossible to establish a universal model to describe theflow curve in the entire temperature range with the samequality.Foramoreaccuratemodelingitisnecessarytofitthemodel coefficients to the separate temperature ranges orto introduce a temperature dependency in the modelparameters.Further research is necessary to verify the temperaturerangefortheinvestigatedmaterialinwhichtwinningoccurs.This knowledge should be taken into account for theimprovementofthecurrentmodel,toachievemoreaccuracyin the prediction of the austenite grain size at lowertemperatures.Futureworkwillfocusonstaticrecrystallizationandgraingrowth of the Fe-Mn23-C0.6 steel. Besides that, it isforeseentoanalyzedifferentcompositionsintheternaryFe-Mn-CsystemthatshowaTWIPeffectwithrespectstotheirhotdeformationandrecrystallizationbehavior.Theultimategoal is to understand dependence of the hot deformation onthe composition from a more fundamental point of view.AcknowledgementsThe authors gratefully acknowledge the financial supportof the Deutsche Forschungsgemeinschaft (DFG) within theCollaborative Research Center (SFB) 761 ‘‘Stahl – abinitio’’.Fortheircontributiontothisworktheauthorswouldlike to thank the project partners in the Departments ofFerrousMetallurgy(IEHK)andMaterialsChemistry(MCh)of RWTH Aachen University.References

In this paper, the capabilities of the thin strip (twin roller) casting method to produce high manganese steel strip are examined. For this purpose a FeMn22C0.6 strip has been cast both using a lab-scale twin roll casting line and a more conventional process chain. The experiments show that the production of high manganese steel strip is feasible with both methods. Differences become apparent in the microstructure and chemical composition. While the strip which was produced by ingot casting and hot forming shows a homogenous grain distribution, the thin-strip-cast one shows a typical casting microstructure, consisting of dendritic and globulitic structures. In addition, the thin-strip-cast steel contains the accurate carbon content, while the hot forming route led to a loss of carbon, which influences the mechanical properties. The good potential of thin-strip casting of high manganese steels, although it still has to be improved, is confirmed.

In this work compression tests were performed to characterize the flow behavior of three different high manganese austenitic steels (HMS) in dependence of temperature (300–1200 °C) and strain rate (0.1-10 s−1). True stress-true strain curves were calculated from the experimental data. Temperature compensation was applied to remove the effects of adiabatic heating. At 300 °C the influence of strain rate is small but rapidly increases with temperature. DRX can be observed above 1100 °C for all HMS with 23 wt% Mn starting from the smaller strain rates. Higher Mn contents seem to promote DRX which occurs first for a 28 wt% Mn steel at 1000°C. While an increasing Mn content decreases the maximum flow stress at smaller temperatures, the opposite is found at temperatures above 700 °C. Carbon influences the stress-strain curves mainly at temperatures below 700 °C as it raises the maximum stress levels. At temperatures above 1100 °C all three investigated HMS show similar flow curves. By increasing the temperature from 300 °C to 1200 °C the initial flow stresses are reduced by a factor of ten. The maximum flow stress levels are decreased by a factor of eight (Fe-Mn28-C0.3), ten (Fe-Mn23C0.3) and eleven (Fe-Mn23C0.6).

The process of hot forging with permanent moulds is a challenge in respect to the very high thermal, mechanical and tribological loads on tools. Ensuring sufficient lifetime application of protective films can be beneficial. Initial screening experiments using PVD coated compression plates show that one of the metastable phases of alumina, the γ-phase, exhibits high strength and toughness and fulfils the requirements for a protective coating. The next important step in the development towards an industrial application is the implementation on complex tool shapes and verification in real forming experiments. After coating deposition using an industrial coating unit, coated dies were tested in forming experiments under industrial conditions. The forming experiments show an improvement of the wear resistance after 1000 forming cycles for the coated dies compared to the uncoated dies.

To characterise the bonding quality of semi-solid joined components, fundamental investigations were carried out by producing composite test specimens. By using steel as a semi-solid base matrix and different steel or copper alloys as inserted materials, an interesting field of material combinations was realised. Two different steel grades, the cold forming tool steel X210CrW12 and the bearing steel 100Cr6, were chosen as the material of the base matrix. Geometry variations were tested along with the variation of materials mentioned. The results supply information about the influence of the inserts shape on an early cooling of the base material during form filling or remelting of the insert caused by overheating. Qualitative and quantitative analyses of the mechanical characteristics of the bonding were carried out using mechanical tests. Metallographic analyses complete the description of the bonding mechanisms at the contact zone between the solidified matrix and the insert. The investigations on basic geometries show a good joining quality, which is mainly based on a strong force and form closure caused by contraction of the solidifying and cooling base matrix. In addition, material closure occurs in areas that are strongly heated during the joining process. These results provide key information for the design of prospective components of a new generation.

The recovery behavior of a commercial aluminum alloy 3103 was investigated by the means of two alternative experimental methods: stress relaxation (SR) and double tension tests (DT). In case of SR, the stress-time evolution after deformation was recorded, and for DT the yield stress after several recovery times were measured. The DT tests were further sub-divided into tests with and without external load during recovery. The results revealed that the recovery kinetics is clearly accelerated by the external stress during the SR. However, the difference between the DT and SR stresses is much larger. It is caused by continued dislocation glide after the deformation, which causes continued plastic elongation of the specimens. This is demonstrated quantitatively by appropriate evaluation models for both experiments. In contrast to DT, the SR evaluation accounts for the elastic SR due to plastic elongation, but the recovery parameters are the same ones as for DT. This makes it possible to replace DT by SR experiments, which are materially less laborious.

The influence of static recovery on the yield stress of AA8079 was investigated in lab-scale cold rolling experiments. The yield stress of AA8079 in the cold rolling process is affected by static recovery, but the softening caused by static recovery is completely compensated in the subsequent cold rolling pass. Thus, the effect of static recovery on the yield stress of the final product is of minor importance. For the TPM, the kinetics of static recovery of the AlFeSi alloy AA8079 were determined for different temperatures and strain rates. The measured softening kinetics were then implemented in the physically based flow stress model 3IVM+. This flow stress model was extended with an empirical approach for static recovery to enable the through-process modeling of cold-rolled aluminum in consideration of static recovery. Future work will focus on physically based modeling of static recovery without using empirical approaches.

In this paper, the stake mark induced failure of a generator rotor forging is analysed using finite element analyses in combination with a Cockroft & Latham failure model. Evidence is found from damage analysis that the rotor failed due to micro cracks and residual stresses induced by a double stake mark, which was located at a position subject to concentrated rotating-bending stress amplitudes and torsional mean stress. The analysis presented here verifies the results of the damage analysis by showing that the stake mark configuration of the failed rotor was the most detrimental among a number of similar configurations. According to the finite element analysis, this stake mark configuration combines a high probability of inducing propagating sub-surface micro-cracks with considerable tensile residual stresses.

The thixoforming of metals is a new forming technology, which combines the advantages of casting and forging and focuses on the production of structural components with complex shapes. Various components made of aluminium and magnesium are already industrially produced. Apart from this, using steels in the thixoforming processes is still a matter of research. This paper summarises the state of the art of steel thixoforming. Besides relevant material and process parameters, different process routes, numerical modelling techniques, and tool requirements are discussed. In addition, thixoformed prototypes of different steel grades are presented and evaluated with defect index cards, which characterise occurring defects and give suggestions how to avoid them. The design of suitable tool materials and tool concepts, the development of heating strategies which provide a homogeneous temperature distribution, and the development of thixoformable steels are main topics of current research. This paper focuses on the technology of steel thixoforming with regard to the material requirements, the production processes, and the accompanying current technical problems.

In this paper the air bending of Tailor Rolled Blanks (TRB) to load optimised profiles is investigated. A new flexible modular tool system has been developed in order to locally adapt the die height to the spring back which is more pronounced in thinner areas in comparison to thicker areas of the TRB. With the new tool system the dies can be modulated according to the thickness distribution of the Tailor Rolled Blank, whereas the amount of die lifting depends on the thickness difference and the corresponding variance of mechanical properties. In bending tests with several specimens having a constant thickness a linear relation between the increasing part angle and a stepwise increased die lifting was observed. With this linear dependency the amount of die lifting can be calculated and thus applied on bending of TRB. Special consideration is required for the die adjustment in the area of the linear thickness transition, therefore three different die arrangements have been investigated. The results of different bending tests are compared and evaluated in order to apply the new technique to form a new car body floor structure in profile intensive construction. By using load optimised profiles in combination with a steel 22MnB5 which has been heat-treated at defined sections the survival space of a car passenger in a side pole impact has been enormously increased by more than 40 %.

In an effort to investigate thixo-joining of aluminium alloy AlSi7Mg with bolts of different metals, a series of experiments was carried out. An aluminium master part of high geometric complexity was thixo-forged. Then thixo-joining experiments were conducted. While the thixo-forging of the aluminium master part being completed, bolts of brass, copper, plain carbon steel and stainless steel were integrated into the thixo-forged part in one step. Evaluations of the produced parts were performed with X-ray inspection, microstructure and segregation analyses. The experimental results confirm that the aluminium alloy A356 has good formability in semi-solid state and that the thixo-joining of the metal bolts with the aluminium part in one step is feasible.

The work detailed in this paper focuses on a new forming strategy for the CNC incremental sheet forming (ISF) process that is appropriate to form steep flanges, e.g. for parts designed for deep-drawing. When parts are designed for deep-drawing, they usually contain steep or rectangular side walls that cannot be manufactured using the standard ISF strategies. Unlike prior approaches to obtain steep flanges through ISF, the present method achieves a rough approximation to the final part already in the preforming stage. This can be accomplished without excessive sheet thinning due to sheet bending and stretching at this stage. As a consequence, additional material can be used for the finishing stages, thus yielding a final part with largely reduced thinning. After basic studies on a simple benchmark problem, the new bending/stretching strategy is tested with an industrially applied part that is usually produced by deep-drawing. Finally, the ISF workpiece is evaluated against the deep-drawn component with respect to sheet thickness and geometric accuracy.

Recording Stribeck-like curves is an efficient way to evaluate the frictional performance and efficiency of patterned surfaces. Elliptical patterns with varying area density and structural depth are fabricated by micro-coining on steel substrates (AISI 304). A ball-on-disc tribometer is used to perform unidirectional sliding experiments for the polished reference and the elliptical patterns dependent on the sliding velocity. In this study, a clear connection between structural parameters such as length of long and short axis, aspect ratio, and pitch with the frictional behavior can be found. Comparing patterns with comparable depth and area density underlines that elliptical patterns having larger individual features (increased length of both axes) separated by a larger pitch reduce the COF more significantly. The number of tribologically active individual elliptical structures, recirculation effects of the lubricant, as well as the pattern geometry that may lead to undesired edge effects and stress concentrations need to be taken into consideration to explain those findings. The sample with the smallest structural depth, the smallest area density, and the lowest aspect ratio (A1) leads to the maximum friction reduction (4-fold) for all velocities which underlines the enormous potential of elliptical structures in terms of friction reduction.

In nature, many examples of multi-scale surfaces with outstanding tribological properties such as reduced friction and wear under dry friction and lubricated conditions can be found. To determine whether multi-scale surfaces positively affect the frictional and wear performance, tests are performed on a ball-on-disk tribometer under lubricated conditions using an additive-free poly-alpha-olefine oil under a contact pressure of around 1.29 GPa. For this purpose, stainless steel specimens (AISI 304) are modified by micro-coining (hemispherical structures with a structural depth of either 50 or 95 μm) and subsequently by direct laser interference patterning (cross-like pattern with 9 μm periodicity) to create a multi-scale pattern. The comparison of different sample states (polished reference, laser-patterned, micro-coined, and multi-scale) shows a clear influence of the fabrication technique. In terms of the multi-scale structures, the structural depth of the coarser micro-coining plays an important role. In case of lower coining depths (50 μm), the multi-scale specimens show an increased coefficient of friction compared to the purely micro-coined surfaces, whereas larger coining depths (95 μm) result in stable and lower friction values for the multi-scale patterns.

Increasing popularity of clad metals leads to a higher demand.[1] To increase productivity and reduce production costs in comparison to established production routes, the production of clad steel strips by means of twin-roll casting is investigated. After first successful trials,[2] the influence of downstream treatment on the bond within clad steel strips consisting of a stainless steel (X5CrNi18-10) cladding strip and a high manganese (Fe–17Mn–0.6C–1.5Al) cast strip produced by twin-roll casting is investigated in the present study. After hot rolling of the strips with a reduction of 20% and annealing for 1 h at 1150 °C, the bonding interface for three different conditions − rolled, annealed, as well as rolled and annealed − is examined and the bonding strength is determined qualitatively and quantitatively. The obtained results are then compared to previously obtained results with as-clad strips. The highest bonding strength is found in the hot rolled strips. It rises from an average of 250 MPa for as-clad strips to over 400 MPa. For the additionally annealed strips bonding strength decreases by approximately 40 MPa, while the lowest bonding strength has been measured for strips that have been annealed and not rolled.