JP2014132110A - Method for manufacturing a product consisting of a flexibly rolled strip material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a coated thin steel sheet consisting of a flexibly rolled strip material and providing an especially favorable corrosion protection.SOLUTION: The provided method includes: a step of providing a strip material (2) consisting of a thin steel sheet; a step of forming, as a step (V1) of flexibly rolling the strip material, a strip material having variable thicknesses over the length thereof; a step of executing, as a step (V3) of electrolytically coating a made-of-metal coating material including at least 93% of zinc, electrolytic coating following the completion of the flexible roll; a step of executing, as a step (V4) of executing a heat treatment at a temperature higher than 350°C and beneath the solidus of the coating material, the heat treatment following the completion of the electrolytic coating; a step (V5) of forming a blank (20) from the flexibly rolled strip material (20); and a step (V6) of cold- or hot-processing the blank.

Description

  The present invention relates to a method for producing a coated sheet steel comprising a flexible rolled strip. This coating protects the steel sheet from corrosion.

  Various methods are known for coating components made of steel with a zinc or zinc alloy layer, such as hot galvanizing (hot galvanizing) or galvanic (electrolytic) galvanizing. Hot galvanization is understood to be the coating of a steel member with a solid, metallic zinc coating by immersing the pretreated steel member in a melt of liquid zinc. In galvanic galvanization, the workpiece is immersed in a zinc electrolyte. The electrode made of zinc acts as a “sacrificial anode” based on being a base metal compared to the workpiece. The workpiece to be galvanized acts as the cathode. Therefore, the coating layer is also referred to as a cathode type anticorrosion part.

  In Patent Document 1, a method of flexible rolling a coated steel strip is known. Hot or cold strips are electrolytically coated and then subjected to a flexible rolling process. The steel strip coated in this configuration obtains different plate thicknesses over length. The coating is adjusted to the sheet thickness after flexible rolling, or adjusted to the rolling pressure during flexible rolling. For this purpose, the coating layers are formed with different thicknesses.

  In Patent Document 2, a method for producing a steel strip provided with a cathode-type anticorrosive coating layer is known. For this purpose, the steel strip is hot rolled, then cold rolled and subjected to electrolytic galvanization. After electrolytic galvanization, the steel strip is heat treated for a period of 4 to 48 hours in a batch annealing furnace at a temperature of 250 to 350 ° C., thereby forming a zinc / iron layer.

  In Patent Document 3, a method for forming a flexible rolled strip material having a cathode type anticorrosion layer is known. The method comprises the steps of providing a rolled strip with a cathodic protection layer as a hot or cold strip and flexible cold rolling the coated rolled strip with a variable rolling gap during rolling. including.

  In Patent Document 4, a method for realizing a workpiece having extremely high mechanical characteristics is known. This workpiece is processed by deep drawing using a thin steel strip as a starting point. The workpiece is hot rolled and coated with a metal alloy made of zinc. For this purpose, the sheet metal is cut and heated to a temperature of 800-1200 ° C. and then placed in a hot deep drawing process. Thereafter, the excess metal sheet necessary for the deep drawing process is removed by cutting.

German registered patent No. 102007013739 German Registered Patent No. 1020090516673 German Patent Application No. 102007019196 EP Patent Translation No.60119816

  The object of the present invention is to provide a method for producing a coated sheet steel made of flexible rolled strip material, which provides particularly good corrosion protection.

  The first solution is characterized by providing a strip of thin steel sheet, flexible rolling the strip, forming a thickness that varies over the length of the strip, and at least Applying electrolytic coating with a metallic coating material containing 93% by weight of zinc, the electrolytic coating being performed after said flexible rolling, and above the solidus of the coating material above 350 ° C. Flexible rolling comprising the steps of: heat-treating after electrolytic coating; forming a blank from a flexible rolled strip; and cold or hot working the blank. A method of manufacturing a product from a stripped material

  A feature of the second solution is to provide a strip material comprising a thin steel plate, flexible rolling the strip material, forming a thickness varying over the length of the strip material, and at least zinc and A flexible rolled strip material comprising the steps of electrolytic coating with a metallic coating material containing iron, forming a blank from the flexible rolled strip material, and cold or hot working the blank. There is a method for manufacturing products from.

  The advantage of the above two methods is that the electrolytic coating is performed after flexible rolling. This achieves that the provided coating layer has a uniform thickness over the length of the flexible rolled strip. In this respect, the region of the strip material that is strongly rolled also has a layer thickness that reliably protects against corrosion. Overall, the process time for manufacturing the product can be shortened and less coating material is required, which also favors manufacturing costs.

  A flexible rolled product is understood here as a steel strip with different thicknesses, a square blank or a shape cut. This shape cut is obtained from a steel strip which has been rolled flexibly by mechanical cutting or laser cutting. A hot-rolled strip or a cold-rolled strip can be used as the strip material for flexible rolling. This concept can be understood in terms of technical terms. A hot-rolled strip is understood as a rolled steel end product (steel strip) produced by rolling after preheating. A cold-rolled strip is understood as a cold-rolled steel strip (flat steel). In this steel strip, the final thickness reduction by rolling takes place without prior heating.

  In both of the above solutions, it is recognized that further steps can be interposed between the individual method steps.

  For example, strip correction can be set after flexible rolling. The formation of the blank from the strip material can be carried out before or after the electrolytic coating. Conceptually forming is understood to mean that a sheet metal blank is stamped from the strip material, i.e., the strip is left with an edge that is not used afterwards, and that the strip material can be easily cut and shortened into the partial parts. It is also understood that it is carried out in particular by a cutting process.

  In the first solution, a coating layer consisting of at least 93% by weight of zinc is deposited on the strip material. In this configuration, the zinc proportion may in particular be 95%, 97% or 99% by weight and may also be 100% by weight (pure zinc coating layer). For electrolytic coating, anodes made of pure zinc or zinc and other alloy elements that release metal ions into the electrolyte when energized are used. Zinc ions, and possibly other alloy element ions, are deposited as atoms on the strip material connected as the cathode to form a coating layer. As set in the first solution, a subsequent heat treatment is preferably included in the deposited zinc and strip material during the deposition of the coating layer with a high zinc proportion of more than 93% by weight. This results in the formation of an alloy between the iron and the entire zinc / iron coating layer.

  In the second solution, a zinc / iron alloy layer is obtained in advance by electrolytic deposition. The proportions of zinc and iron are preferably selected so that at least one of the following conditions applies: That is, the condition that the alloy layer contains at least 5% by weight of iron, the condition that the alloy layer contains at most 80% by weight of iron, the condition that the alloy layer contains at least 20% by weight of zinc, and / or The condition that the alloy layer contains a maximum of 95% by weight of zinc. It is particularly preferred that the proportions of zinc and iron are selected such that in the deposited state there is at least partly a δ1 phase, in particular a δ1 phase and a Γ phase, or simply a Γ phase between metals. This is achieved, for example, with an iron proportion of 10-30% by weight or a zinc proportion of 70-90% by weight. In this configuration, the addition of another alloy element is not excluded. In this configuration, the coating layer itself already contains zinc and iron, so that subsequent heat treatment can be avoided. Zinc and iron atoms are spaced a few nanometers apart, resulting in a particularly short diffusion path. However, it is understood that the heat treatment can be performed even during the electrolytic precipitation of the zinc / iron alloy. Due to the short diffusion path, a very short heat treatment, for example by induction, is sufficient. Overall, a reduction in process time can preferably be achieved with the method aspect described above.

  The method according to the second solution can be carried out after electrolytic coating or before processing or shaping, according to a first possible configuration without heat treatment. According to the second possible configuration of the second solution, as another step, after electrolytic coating, a heat treatment is set in the temperature region above 350 ° C. and below the melting temperature of the coating material (solidus). can do. The solid phase line simply indicates a line on the lower side of the solid phase in the state diagram for the coating material. Above the solidus, the coating material is at least partially molten.

  Since iron atoms diffuse from the base material into the coating material, the iron ratio in the coating layer increases as the heating time advances. By increasing the iron percentage in the coating layer, the heat treatment temperature can be increased without reaching or exceeding the solidus. This allows temperatures up to 781 ° C. in proper process implementation. The possibility of a temperature rise during the heat treatment naturally applies also to the first configuration. The temperature can increase stepwise or continuously as the iron percentage increases.

  The liquid phase line indicates a line having a two-phase region or a multi-phase region, and a solid-liquid in the lower side of the phase diagram for the coating material. The coating material is in a molten form above the liquidus. The lower boundary of the biphasic region is called the solidus. The temperature of the solidus is based on the composition depending on the proportion of the alloy. In pure zinc, the solidus is 419.5 ° C., and in zinc-iron alloys it is up to 782 ° C. if the proportion of Γ phase is still present. Therefore, the flexible rolled strip material is electrolytically coated to the rolling hard with an appropriate proportion of iron and then heat treated at a relatively high temperature above 500 ° C. and up to 782 ° C. without generating a melt phase. Is possible.

  Furthermore, since the heat treatment in the temperature range of 500 ° C. to 782 ° C. is suitable for performing recrystallization annealing, the formed material is particularly suitable for indirect hot working. Accordingly, it is possible to omit recrystallization annealing after flexible rolling and before coating, which is usually essential. For example, in the first-mentioned solution using pure zinc (100% zinc coating material), the heat treatment process can be started at an annealing temperature of 380 ° C., with an increasing iron fraction based on the diffusion process. In particular, the temperature is increased to a maximum of 781 ° C.

  In two solutions, it is true that the coating material can comprise further alloy elements, such as manganese, chromium, silicon or molybdenum. Regardless of the type and number of alloy elements, the particularity of the present invention resides in temperature regulation for the purpose of forming a zinc-iron alloy layer. In the composition that is actually present during the process, the solid phase line of the coating material is not reached or coated at the time of the formation of a zinc / iron phase biphasic alloy or a layer consisting of more than two alloy elements. Each alloy temperature is selected so as not to exceed the solidus of the material. That is, the alloy is formed by solid phase diffusion.

  During the heat treatment, iron is diffused from the material to be coated into the metallic coating layer. In this configuration, zinc changes from a coating layer to a zinc-iron alloy that provides cathodic protection. The predetermined temperature range above 350 ° C. and below the solidus is particularly advantageous as long as the diffusion takes place relatively quickly. By containing iron, the cracking tendency of the coating layer is reduced, so that the durability of the component is improved.

  As described above, the phase change can be achieved by induction heating according to the first possible embodiment. This method configuration is particularly suitable for zinc and iron electrodeposition because of the short diffusion distance. As a result, a short heat treatment already leads to the desired phase change. According to a second possible configuration, the heat treatment can be carried out by batch annealing. This batch annealing is particularly suitable for electrolytic deposition of pure zinc. Preferably, during batch annealing, a residence time of 10 to 80 hours, preferably 30 to 60 hours, is set, so that sufficient time is provided so that a zinc-iron alloy is formed by diffusion. The residence time preferably represents the total time during which the blank or strip material is heat treated, ie it can include the heating phase, the holding phase and the cooling phase together. Another possible configuration is conductive heating. Of course, other technically possible heat treatment methods in this configuration are not excluded.

  As another method step, the strip material may be coated with an intervening layer prior to electrolytic coating. In particular, a nickel or aluminum containing layer can be used as the intervening layer. This layer can be understood as a layer containing nickel or aluminum at least partially. This includes both pure nickel or aluminum layers. The nickel layer provides additional protection of the surface and subsequently improves the adhesion of the coating layer containing zinc that is provided. The nickel coating layer can be formed, for example, by electrolytic or deposition without external current. Obviously, other materials for the intermediate layer are not excluded. For example, a coating layer containing manganese or chromium can also be used. Both manganese and chromium have a good solubility in iron, which has a cubic lattice and has a good influence on the alloy properties.

  According to another possible configuration, the strip material can be provided with a scale protection after electrolytic coating. This is particularly effective when austenitization is not performed in a protective gas atmosphere for subsequent hot working. Scale is understood to be a sufficiently oxidative corrosion product generated during the reaction of metallic materials in air or other oxygen-containing gases at high temperatures. The provision of the scale protection unit can be performed by thermal spraying or rolling. In addition to protection against oxidation, another advantage of the scale protection layer is that the surface has a high quality. In particular, a cleaning treatment such as shot blasting is not necessary before the lacquer treatment after the metal sheet. Furthermore, scale protection can positively affect the coefficient of friction and heat absorption characteristics during hot working. A further advantage of the scale protector is that the adhesion of the cathodic anticorrosion protection layer underneath is improved. Furthermore, the expansion of the temperature / time window within the framework of austenitization is possible, for example, by forming an alloy with a layer below the scale protective material. The scale protector can be provided before or after the heat treatment performed below the solidus.

  At appropriate points in the process, blanks or shape cuts are produced from the flexible rolled strip material. This can be done by mechanical cutting or laser cutting. A blank is understood to be a particularly rectangular sheet metal that is separated from the strip material. As a shape cut, a sheet metal element formed from a strip material with an outer contour already adapted to the shape of the final product is understood. In this configuration, the term “blank” is unified and used for both rectangular blanks and shape cutting parts. The blank can be manufactured before or after the electrolytic coating, and in some cases, before or after the provision of the scale protector.

  The sheet metal blank is hot worked by a possible method configuration that applies to two solutions. Hot working is understood as a machining process in which the workpiece is heated to a temperature in the region of hot working before machining. Heating takes place in a suitable heating device, for example a furnace. According to a first possible configuration, the hot working is a partial step of forming a pre-formed component by cold working of the blank, and then at least a partial region of the pre-worked component is austenitic. It can be carried out as an indirect process including a partial step of heating to the conversion temperature and a subsequent partial step of forming the final contour of the product by hot working. The austenitizing temperature can be understood as a temperature range where there is at least partial austenitization (structural conditions in the two-phase region of ferrite and austenite). Furthermore, it is also possible to austenitize only a partial region of the blank, for example in order to allow partial curing. Hot working is, according to a second possible configuration, that at least a partial region of the blank is heated directly to the austenitizing temperature and then hot worked in a predetermined step to the desired final contour. It can also be implemented as a direct process characterized. Prior (cold) processing is not performed in this configuration. Even in the direct process, partial hardening can be achieved by austenitizing the partial region. It is true for both processes that curing of the sub-region of the component is possible with different temperature-controlled tools or by using multiple tool materials allowing different cooling rates. . In the last configuration, the entire blank or component can be fully austenitic.

  In each configuration, according to an advantageous method configuration that applies to two hot working processes, the coating material is in the solid state at the time of introduction of hot working, ie the temperature is below the solidus of the coating material. It is supposed to be cooled to the range. After hot working, the iron content in the edge layer is less than 80%, preferably 60% or less, particularly preferably 30% or less.

  In principle, according to the configuration of the alternative method that is effective for the two above-mentioned solutions, it is possible to cold work the thin metal plate blank. Cold working is understood in this configuration as a machining process in which the blank is not properly heated before machining. Processing is therefore carried out at space temperature. The blank is heated by the diffusion of the supplied energy. Cold working is used as a process for working particularly soft body steel.

  Furthermore, the feature of the solution of the above-mentioned problem resides in a metal sheet blank made of a flexible rolled thin steel sheet that is electrolytically coated with a metal coating layer after flexible rolling and is hot worked after this coating. Thus, the above advantage of a constant layer thickness over the length of the flexible rolled strip or the blank formed from this strip is provided. Since the blank can be formed by one or more method steps, reference is made to the above description regarding the steps and the advantages associated with this step.

1 is a flowchart schematically showing a method according to the present invention in a first embodiment. FIG. FIG. 6 is a diagram schematically showing a method according to the present invention in a second embodiment as a flowchart. FIG. 6 is a diagram schematically showing a method according to the present invention in a third embodiment as a flowchart. It is a figure of a zinc and an iron phase.

  In the following, advantageous embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a method according to the invention for producing a product composed of a flexible rolled strip material 2 according to an embodiment of the first method. In method step V1, the strip 2 wound around the coil 3 in the starting state is rolled by rolling, in particular by flexible rolling. For this purpose, the strip material 2 having a wide and constant thin metal plate thickness (hereinafter simply referred to as plate thickness) over the length before the flexible rolling is formed by the rolls 4 and 5 along the rolling direction. Roll to obtain varying thickness. The process is monitored and controlled during rolling. In this embodiment, the data measured by the plate thickness measuring unit 6 is used as an input signal for controlling the rolls 4 and 5. After flexible rolling, the strip material 2 has different thicknesses in the rolling direction. The strip material 2 can be wound around the coil 3 again after the flexible rolling, and the strip material 2 can be supplied to the next method step.

  After flexible rolling, the strip material 2 is smoothed in method step V2. This is done in the strip straightening device 7. The smoothing method steps are optional and can be omitted.

  After flexible rolling (V1) or smoothing (V2), the strip material 2 is provided with an anticorrosion part in method step V3. For this purpose, the strip material 2 passes through an electrolytic strip coating apparatus 8. It can be seen that the strip coating is performed in a continuous manner, that is, the strip material 2 is removed from the coil 3, passes through the coating device 8, and is again wound up on the coil 3 after coating. This embodiment of the method is particularly advantageous because it requires less labor for providing the anticorrosion part to the strip material 2 and the process speed is high. In this embodiment, the immersion tank 9 filled with the electrolytic solution 10 through which the strip material 2 passes can be seen in the strip coating apparatus 8. The strip material 2 is guided by the roll sets 11 and 12.

  The electrolytic coating is performed in this method embodiment with a metallic coating material containing at least 93% zinc. A particularly good corrosion resistance is achieved with a high zinc proportion. It will be appreciated that the zinc percentage may be higher, for example greater than 95%, in particular greater than 97% and 100% (pure zinc).

  For coating, an anode made of, for example, zinc can be used. This anode releases zinc ions to the electrolyte when energized. Zinc ions are deposited as zinc atoms on the strip material 2 connected as a cathode to form a zinc layer. Alternatively, an inert anode and zinc electrolyte can be used.

  In addition to the zinc proportion, the coating layer may contain further alloy elements such as aluminum, chromium, manganese, molybdenum, silicon. In some cases, the proportion of alloying elements added is less than 7%. Manganese has good solubility in iron. This has an advantageous effect on alloy formation during heating.

  After the electrolytic coating (V3), the strip material 2 wound around the coil 3 is subjected to a heat treatment in method step V4. The heat treatment can basically be performed in a form suitable for each technology, and if only two methods are exemplified, for example, it can be performed in batch annealing, or can be performed by induction heating. In this embodiment, the heat treatment in the furnace 13 is shown.

  The heat treatment is carried out at a temperature above 350 ° C. and below the solidus of the coating material. The temperature transition of the solidus line depends on the composition based on the proportion of the alloy. At a lower temperature in the given range, diffusion from iron to the zinc layer occurs, so that a diffusion layer is formed as the operating time of the heat source proceeds.

  During the heat treatment, iron is diffused from the strip material to be coated to the metal coating layer. In this embodiment, zinc changes from a coating layer to a zinc-iron alloy that provides a cathodic protection. Through the temperature range above 350 ° C. and below the solidus, diffusion takes place relatively quickly. The residence time of the heat treatment in the batch annealing is preferably 10 to 80 hours, preferably 30 to 60 hours, and sufficient time is provided so that the zinc-iron alloy is formed by diffusion.

  Another effect of the heat treatment is that the rolled strip material 2 again gains higher toughness and ductility since the hardening of the material that occurs during rolling is reduced or eliminated. The strip material can be easily processed in subsequent method steps and positively affects the material properties of the final product to be manufactured.

  After the heat treatment (V4), individual metal sheet blanks (hereinafter referred to as sheet blanks) 20 are formed from the strip material 2 in the next method step V5. Forming the thin plate blank 20 from the strip material 2 is preferably performed by punching or cutting. Depending on the shape of the thin plate blank 20 to be manufactured, the thin plate blank 20 can be punched out from the strip material 2 as a shape cutting portion. In this embodiment, the edges that are not used subsequently remain in the strip material, or the strip material 2 can be simply cut short into partial members. 1 schematically shows a thin plate blank 20 formed from a strip material 2, which can also be called a three-dimensional thin plate blank (3D-TRB).

  After manufacturing the blank 20 from the strip material 2, the blank 20 is deformed to form the desired final product in method step V5. According to the first possible embodiment, the blank 20 is hot worked, or according to the second possible embodiment, cold blanked.

  Hot working can be performed as a direct or indirect process. In a direct process, the blank 20 is heated to the austenitizing temperature prior to processing. This can be done, for example, in induction or in a furnace. The austenitization temperature can be understood as a temperature range in which at least a part of austenitization (structure in the two-component phase of ferrite and austenite) exists. It is also possible to austenitize only a partial region of the blank, for example in order to allow partial curing. After heating to the austenitizing temperature, the heated blank is formed in a mold 14 which gives the shape and at the same time cooled at a high cooling rate. In this case, the component 20 acquires the final contour and is simultaneously cured.

  In the case of indirect hot working, the blank 20 is further pre-formed before austenitization. This pre-molding is performed at a room temperature or a low temperature state of the blank, that is, without heating in advance. At the time of pre-molding, the component does not yet correspond to the final shape but acquires a profile or contour close to the final shape. Thus, after pre-molding, austenitization and hot working are performed as in the direct process. In this embodiment, the component acquires its final contour and is cured.

  As long as hot working is set (directly or indirectly), the steel material desirably has a carbon ratio of at least 0.1% by mass to 0.35% by mass.

  As an alternative to hot working as a shape imparting process, the blank can also be cold worked. Cold working is particularly suitable for soft body steel or components that do not have special requirements for strength. In the case of cold working, the blank is formed at room temperature.

  The particularity of the method according to the invention is that the electrolytic coating (V3) is performed after flexible rolling (V1). The coating layer provided on the strip material 2 has a uniform thickness over the length, in particular irrespective of the thickness of each of the strip materials 2. The more strongly rolled areas also have a sufficiently thick coating layer that ensures protection against corrosion. Further particularity resides in the post-electrolytic coating heat treatment step in the temperature range between 350 ° C. and the lower side of the coating solidus. By the heat treatment, zinc diffuses from the coating layer to the base material, and iron diffuses from the base material to the coating layer. As the iron percentage in the coating layer increases, the temperature within the frame of the heat treatment process can gradually increase to a higher temperature based on the movement of the solidus. A zinc-iron alloy is produced as a coating layer that withstands the relatively high temperatures of subsequent thermoforming processes that may be performed and provides reliable corrosion protection.

  It is understood that the method embodiments according to the invention can also be modified. For example, an intermediate step that is not separately described may be provided between the above steps. For example, the strip material can be provided with an intermediate layer, in particular a nickel layer, an aluminum layer or a manganese layer, before the electrolytic coating. This intermediate layer provides additional protection of the surface and subsequently improves the adhesion performance of the coating layer comprising zinc provided. The strip material or the blank manufactured from the strip material may be provided with a scale protective part (Zunderschutz) after the electrolytic coating (V3) and before or after the heat treatment (V4). This can be particularly evaluated when austenitization for subsequent hot working is not performed in a protective gas atmosphere. The scale protective layer can be provided by thermal spraying or rolling. In addition to protection against oxidation, a further advantage of the scale protection layer is that the surface has a high quality. Furthermore, the scale protective layer can positively affect the friction coefficient and heat absorption characteristics during hot working. Yet another advantage of the scale protector is that the adhesion of the underlying cathodic protection layer is improved. Furthermore, the expansion of the temperature / time window within the framework of austenitization is possible, for example, by forming an alloy of the scale protective material and the underlying layer. One example is an aluminum stack in a scale protection lacquer.

  Furthermore, it is understood that the process embodiments according to the invention can also be changed in the order of the steps performed. For example, the blank can be formed at other locations, for example, before electrolytic coating or, in some cases, before or after provision of the scale protector.

  FIG. 2 shows a method according to the invention for producing a sheet metal blank from strip material 2 according to an embodiment of the second method. Since this second method embodiment is in many ways consistent with the method shown in FIG. 1, reference is made to the above description for common parts. In this embodiment, the same or changed components or steps are denoted by the same reference numerals as in FIG. Hereinafter, differences between the methods of this embodiment will be mainly described.

  Method steps V1 (rolling), V2 (strip correction), V5 (punching) and V6 (processing or forming) are the same as the corresponding method steps V1, V2, V5 and V6 shown in FIG.

  The first difference from the method shown in FIG. 1 is in the method step V3 of electrolytic coating. In the embodiment of the method shown in FIG. 2, the strip material is coated with a metallic coating material containing at least zinc and iron. The zinc / iron alloy layer is obtained by electrolytic deposition of a zinc / iron layer. The proportions of zinc and iron are, according to an advantageous method embodiment, that the alloy layer comprises at least 5% by weight and / or up to 80% by weight of iron, or that the alloy layer is at least 20% by weight and / or at most Selected to contain 95 weight percent zinc.

  It is particularly advantageous if the proportion of zinc and iron is selected so that it is at least partly in the deposited state in the δ1 phase, in particular in the δ1 phase and the Γ phase, or exclusively in the intermetallic Γ phase. For this purpose, for example, the iron ratio in the coating layer may be selected from 10 to 30% by weight, or the zinc ratio from 70 to 90% by weight. In the deposited state at this ratio, an intermetallic phase is at least partially formed.

  A relatively high Γ phase content and a δ1 phase content as low as possible is advantageous for direct hot working. In order to avoid crack formation, it is desirable that the melting temperature of the coating layer for hot working is relatively high. As the iron content increases, the proportion of the Γ phase increases, and thus the solidus moves to a higher temperature in the zinc / iron binary phase diagram (see FIG. 4).

  After electrolytic coating (V3), a blank is formed from the strip material 2 in method step V5. In this embodiment, it is understood that the blank can be cut out before coating in a modified method embodiment.

  Another particularity of this method embodiment based on FIG. 2 is that no intervening heat treatment below the solid phase temperature is performed between coating (V3) and processing or molding in method step V6. That is. Therefore, the method shown in FIG. 2 is particularly short in time.

  The last processing step corresponds to the step shown in FIG. 1, and the above description is referred to in this regard. The blank 20 can be processed cold or hot (directly or indirectly).

  Even in the case of this method embodiment, it is understood that variations, in particular additional intermediate steps or subsequent method steps can be carried out. In this regard, reference is made to the above description to avoid repetition.

  FIG. 3 shows a method according to the invention for producing a sheet metal blank from the strip material 2 on the basis of an embodiment of the third method. Since the third method embodiment substantially corresponds to the combination of the methods shown in FIGS. 1 and 2, the above description is referred to for common points. In this embodiment, the same reference numerals are used for the same or changed components or steps.

  Steps V1 (rolling), V2 (strip correction), V3 (electrolytic coating), V5 (punching) and V6 (machining or forming) correspond to the corresponding method steps shown in FIG. The only difference from the method shown in FIG. 2 is that, after electrolytic coating (V3), heat treatment is carried out in method step V4 as in the method shown in FIG.

  As in the embodiment of the method shown in FIG. 1, the particularity of the embodiment of the method shown in FIG. 3 is in temperature control for the purpose of forming a zinc-iron alloy layer. Each alloy temperature in the heat treatment (V4) is achieved at the time of alloy formation by the solid phase line of the zinc / iron binary phase diagram (see FIG. 4) or the layer structure of more than two alloy elements. Selected to not be exceeded or exceeded.

  An example of the layer structure is a ternary alloy composed of, for example, zinc, iron and manganese, where the manganese is made of a steel substrate, and the manganese is a zinc layer or zinc / electrolytically deposited by a diffusion process during the heating. It reaches the iron alloy layer and is not a component of electrolytic deposition. Instead of manganese, for example chromium or aluminum or silicon or molybdenum can also be considered to diffuse into the electrodeposited layer. It is understood that a steel alloy element may be provided for the coating. This steel alloy element is not described above and is suitable for diffusing into a layer that has been electrolytically deposited by the heating process.

  Variations in this method embodiment, in particular additional intermediate steps or the following method steps, can also be carried out. In this regard, reference is made to the above description to avoid repetition.

  FIG. 4 shows a phase diagram for zinc and iron. The ratio of iron (Fe) or zinc (Zn) is given on the X axis. In this case, the material is 100% iron and 0% zinc at the left end, while the opposite is 0% iron and 100% zinc at the right end. Between the ends, the percentage compositions shown on the X-axis are respectively evident. S is a molten phase, α and γ are iron / zinc mixed crystals (iron rich), ζ and δ or δ1 and Γ are intermetallic phases, and η is zinc / iron mixed crystals (zinc rich). It is.

  In the following, different possible embodiments of electrolytic deposition based on the method according to the invention will be exemplarily described on the basis of a zinc / iron phase diagram.

  As can be produced in the embodiment of the method shown in FIG. 1, during the deposition of the pure zinc layer, it is first above 350 ° C. and below the melting temperature (solidus) of 419.5 ° C. The alloy temperature on the side, for example 400 ° C., is selected. Since diffusion from iron to the zinc layer occurs at this temperature, a diffusion layer, for example, a δ layer is formed as the action period proceeds in the frame of the heat treatment (V4). Another temperature control is designed so that each temperature is always below the solidus of the zinc / iron binary phase diagram.

  During the electrolytic deposition of a coating layer that already contains iron in the zinc layer, such as can be produced in the method embodiment shown in FIG. 3, the starting temperature can be selected above the melting temperature of pure zinc. it can. For example, a starting temperature of 600 ° C. can be selected for the composition of an electrodeposited layer of 85% zinc and 15% iron. This temperature is certainly above the melting temperature of zinc, but below the solidus in the two-phase region Γ + δ1.

  A starting temperature of less than 782 ° C. is possible in the electrolytic deposition of a zinc / iron layer consisting of 60% zinc and 40% iron. This temperature can only be exceeded if the layer is high in iron during the subsequent heat treatment to the extent that only austenitic iron mixed crystals (eg 70% by weight iron and 850 ° C.) are present.

  As described above, the type of heat treatment is not fixed. For example, it may be heating by induction heating or batch annealing, or heating by contact with a high temperature body, for example, a thick steel plate that releases heat to the blank or shape cut.

  In a special embodiment of the invention, the electrolytic zinc-iron alloy has an iron content of 8-12%. This is the composition used for steel with a so-called “Galvannealed” coating layer. The advantage of this composition is that the constituents zinc and iron have a spacing in the nanometer range. In the above range, it is possible to avoid the diffusion process for a long time. Rather, by a short heat treatment in method step V4, the δ1 phase between the metals can be produced from a zinc-iron alloy with an iron content of 8-12%, which has been electrolytically deposited. The composition can be used for both cold working and hot working.

  In yet another special embodiment of the invention, an electrolytic zinc-iron alloy is deposited. The stoichiometric composition of this zinc-iron alloy corresponds to the Γ phase. Alternatively, the composition can be adjusted by precipitation of a zinc / iron layer with a low iron content and subsequent heat treatment. At the end of the heat treatment, a Γ phase is formed. Since this phase first begins to melt at a temperature of 782 ° C., the phase is particularly suitable for hot working. The reason for this can be that the formation of the molten phase can be limited or can be avoided by the stabilization of the layer by a component made of a steel substrate such as manganese (ternary system of iron, zinc and manganese).

  Similarly, in yet another embodiment provided for hot working (V6), even when heated to the maximum austenitizing temperature for hot working (eg 900 ° C.), a non-soluble layer is present. Electrodeposited. This type of coating layer has, for example, a composition of 20% by weight zinc and 80% by weight iron. In this embodiment, it is an iron-zinc binary iron-based alloy.

  Overall, the method according to the present invention can produce a product having a reliable cathode type anticorrosion protection part. This product is very well suited for hot working processes. By at least fully avoiding the occurrence of a liquid phase in the coating layer during the process, the tendency of the product to crack is advantageously minimized.

2 Strip material 3 Coil 4 Roll 5 Roll 6 Thickness control unit 7 Smoothing device 8 Coating device 9 Immersion tank 10 Electrolyte 11 Roll set 12 Roll set 13 Furnace 14 Processing tool 20 Blank V1 to V6 Method steps

The problems include providing a strip of thin steel sheet, flexible rolling the strip, forming a thickness that varies over the length of the strip, and at least 93% zinc. Applying electrolytic coating with a metallic coating material containing the coating, performing the electrolytic coating after flexible rolling, and heat-treating at a temperature higher than 350 ° C. and below the solidus of the coating material A flexible rolled strip material comprising: performing heat treatment after the electrolytic coating; forming or removing a blank from the flexible rolled strip material; and cold or hot working the blank. By the method of manufacturing the product from It is made.
Furthermore, the object is to provide a strip material made of a thin steel plate, the step of flexible rolling the strip material, forming a thickness varying over the length of the strip material, and containing at least zinc and iron Product from flexible rolled strip material comprising the steps of electrolytic coating with a metallic coating material, forming or removing a blank from the flexible rolled strip material, and cold or hot working the blank. This is achieved by the method of manufacturing.
Preferably, heat treatment is set as another method step after electrolytic coating, and the heat treatment is carried out at a temperature above 350 ° C. and below the solidus of the coating material.
Preferably, iron having a ratio of at least 5% iron and at most 80% iron is included.
Preferably, the proportions of zinc and iron are selected such that in the precipitated state at least partly a δ1 phase, in particular a δ1 phase and a Γ phase.
Preferably, the temperature is raised during the heat treatment.
Preferably, the heat treatment is carried out inductively or by batch annealing, the batch annealing being carried out in particular with a residence time of 10 to 80 hours.
Preferably, as another method step, the step of coating the strip material with an intermediate layer, in particular a layer containing nickel or aluminum or manganese, is set up before the electrolytic coating.
Preferably, as another method step, a step of providing a scale protector after electrolytic coating is set.
Preferably, in the hot working, the blank is preliminarily cold worked, at least a partial region of the cold-worked component from the blank is heated to an austenitizing temperature, and the component is hot worked to produce a final contour. Have partial steps (indirect process).
Preferably, hot working has partial steps (direct process) in which at least a partial region of the blank is heated to the austenitizing temperature and the blank is hot worked to produce the final contour.
Preferably, the coating material is in a solid state at the time of introduction of hot working.
Furthermore, the above-mentioned subject is produced by the method according to claim 1 or 2, and is a flexible rolled thin steel sheet that is electrolytically coated with a metal coating layer after flexible rolling and is hot-worked after coating. Achieved by a product consisting of
The first solution is characterized by providing a strip of thin steel sheet, flexible rolling the strip, forming a thickness that varies over the length of the strip, and at least Applying electrolytic coating with a metallic coating material containing 93% by weight of zinc, the electrolytic coating being performed after said flexible rolling, and above the solidus of the coating material above 350 ° C. Flexible rolling comprising the steps of: heat-treating after electrolytic coating; forming a blank from a flexible rolled strip; and cold or hot working the blank. A method of manufacturing a product from a stripped material

Claims (13)

Providing a strip (2) comprising a thin steel plate;
Flexible strip rolling of the strip material (2) (V1), forming a thickness (V1) that varies over the length of the strip material (2);
Applying electrolytic coating with a metallic coating material containing at least 93% zinc (V3), the electrolytic coating being performed after the flexible rolling (V1) (V3);
Heat treatment at a temperature higher than 350 ° C. and below the solidus of the coating material (V4), the heat treatment being performed after the electrolytic coating (V3) (V4);
Forming a blank (20) from the flexible rolled strip material (2) (V5);
Cold or hot working the blank (20) (V6);
A method of manufacturing a product from a flexible rolled strip material. Providing strip material (2) made of thin steel sheet;
Flexible strip rolling of the strip material (2) (V1), forming a thickness (V1) that varies over the length of the strip material (2);
Electrolytic coating with a metallic coating material containing at least zinc and iron (V3);
Forming a blank (20) from the strip material (2) subjected to flexible rolling (V5);
Cold or hot working the blank (20) (V6);
A method of manufacturing a product from a flexible rolled strip material.   Heat treatment (V4) is set as another method step after the electrolytic coating (V3), and the heat treatment (V4) is performed at a temperature higher than 350 ° C. and below the solidus of the coating material. The method of claim 2, wherein: At least 5% iron,
Up to 80% iron,
The method according to claim 2, wherein iron having at least one of the following ratios is included.   5. The ratio of zinc and iron is selected such that in the deposited state at least partly a δ1 phase, in particular a δ1 phase and a Γ phase, 5. the method of.   The method according to claim 1 or 3, characterized in that the temperature is increased during the heat treatment (V4).   4. Process according to claim 1 or 3, characterized in that the heat treatment (V4) is carried out inductively or by batch annealing, the batch annealing being carried out in particular with a residence time of 10 to 80 hours. As another method step, before the electrolytic coating (V3),
Coating said strip material (2) with said intermediate layer, in particular a layer comprising nickel or aluminum or manganese;
The method according to claim 1, wherein a step is set. As another method step, after the electrolytic coating (V3),
The method according to claim 1, wherein a step of providing a scale protection unit is set. The hot working (V6)
Cold-working the blank (20) in advance,
Heating at least a partial region of a component previously cold worked from the blank (20) to an austenitizing temperature;
Hot working the component to produce a final contour;
10. A method according to any one of claims 1 to 9, characterized in that it comprises partial steps (indirect processes). The hot working (V6)
Heating at least a portion of the blank (20) to an austenitizing temperature;
Hot-working the blank (20) to produce the final contour;
10. A method according to any one of claims 1 to 9, characterized in that it comprises partial steps (direct process).   The method according to any one of claims 1 to 11, characterized in that the coating material is in a solid state at the time of introduction of the hot working (V6).   A flexible rolling produced by the method according to any one of claims 1 to 12, wherein the flexible rolling is electrolytically coated with a metal coating layer after the flexible rolling, and is hot-worked after the coating. Products made of thin steel plates.

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