A method for eliminating wrinkles on the outer wall of ferrite stainless steel in stamping of composite sheet

Abstract

The present invention provides a method for eliminating wrinkles on the outer wall of ferritic stainless steel during stamping of a composite plate. The method of the present invention comprises the following steps: S1: making a composite plate from an austenitic stainless steel plate, an aluminum alloy plate and a ferritic stainless steel plate that has been subjected to multiple rolling and annealing treatments, and cutting the composite plate to obtain a blank; S2: symmetrically setting draw ribs on both sides of the vertical direction of the punch rolling, and adjusting the edge fillet radius of the die to obtain a mold; S3: lubricating the surface of the blank and the mold, placing the blank on the mold for stamping after lubrication, and obtaining a stamped part with a ferritic stainless steel plate as the outer wall. The present invention can solve the quality problem of wrinkles on the outer wall of ferritic stainless steel during the stamping process of the composite plate, and improve the surface quality of the stamped parts.

Description

Technical Field

[0001] The invention relates to the technical field of stamping and forming, in particular to a method for eliminating wrinkles of ferrite stainless steel on the outer wall of a composite plate by stamping and forming. Background Art

[0002] Composite materials have the advantages of both base materials and composite materials, such as three-layer composite plates made of SUS 304, Al1050, and SUS430, where SUS 304 is austenitic stainless steel and SUS 430 is ferritic stainless steel. The composite plate has the high strength, high rigidity, and wear resistance of SUS 304 and the excellent properties of low price, pitting resistance, and crevice corrosion resistance of SUS 430. It also has the advantages of low aluminum density and good thermal conductivity of composite materials. Under the condition of meeting the use requirements, compared with the use of pure stainless steel plates, the use of composite plates can save 70-80% of alloy elements such as Cr and Ni, thereby saving 30-50% of costs, and greatly saving stainless steel materials, significantly reducing the material costs of various equipment, and having strong price and market advantages, which has led to the widespread application of composite materials.

[0003] Stamping is a commonly used production process in modern manufacturing. Composite sheets are stamped after cutting, and composite sheets are the main processed objects of stamping. With the continuous increase in the production volume, usage and demand of various products using composite sheets, ferritic stainless steel represented by SUS430 is also increasingly used in composite sheets. However, in the stamping process of these composite sheets, if the outer wall of the stamped part is SUS430 ferritic stainless steel, the surface of the material is prone to wrinkling. The wrinkling problem has the following effects on the stamped parts after stamping: 1) The surface quality of the stamped parts is poor and does not meet the standards; 2) The stacking of materials during the stamping process will cause wrinkling to cause mold wear and reduce the service life of the mold; 3) An additional grinding process needs to be introduced in production to remove surface wrinkles, which increases labor and production costs. Therefore, the wrinkling problem of ferritic stainless steel on the outer wall of composite sheet stamping needs to be solved urgently.

[0004] At present, there are solutions to the wrinkling problem of single ferritic stainless steel stamping, which is mainly through optimizing and changing the rolling method of ferritic stainless steel plate production, such as using asynchronous rolling to cold roll, controlling the asynchronous rolling speed ratio and rolling reduction, and annealing the steel plate obtained by asynchronous cold rolling. For example, ferritic stainless steel with a specific element content (such as Nb, Ti, Mn, Si, P, Cr, etc.) is selected, and after smelting and casting into billets, the ingots are hot-rolled annealed and pickled, and then multiple passes of non-lubricated cold rolling are adopted, and the recrystallization annealing is carried out at 860-940℃ for 1-4min, and the furnace is air-cooled. The above method has a certain effect on solving the wrinkling problem of pure ferritic stainless steel stamping, but it cannot solve the wrinkling problem of ferritic stainless steel on the outer wall of composite plate stamping.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for eliminating wrinkles on the outer wall of ferritic stainless steel during stamping of composite plates. The method can solve the quality problem of wrinkles generated by ferritic stainless steel along the rolling direction during stamping of composite plates, thereby improving the surface quality of stamped parts.

[0007] The present invention provides a method for eliminating wrinkles of ferrite stainless steel on the outer wall of a composite plate formed by stamping, comprising the following steps:

[0008] S1: making a composite plate from an austenitic stainless steel plate, an aluminum alloy plate and a ferritic stainless steel plate that has been subjected to multiple rolling and annealing treatments, and cutting the composite plate to obtain a blank;

[0009] S2: Draw ribs are symmetrically arranged on both sides of the rolling direction perpendicular to the punch (i.e., the rolling direction), and the edge fillet radius of the die is adjusted to obtain a die;

[0010] S3: Lubricate the surfaces of the blank and the mold, and after lubrication, place the blank on the mold for stamping to obtain a stamping part with a ferritic stainless steel plate as an outer wall.

[0011] In the present invention, the material of the austenitic stainless steel plate is SUS 304, the material of the aluminum alloy plate is Al 1050, and the material of the ferritic stainless steel plate is SUS 430; it can be understood that the austenitic stainless steel plate, the aluminum alloy plate and the ferritic stainless steel plate that has been subjected to multiple rolling and annealing treatments can be made into a composite plate by conventional methods such as rolling, and the aluminum alloy plate in the composite plate is located between the austenitic stainless steel plate and the ferritic stainless steel plate.

[0012] The present invention does not impose strict restrictions on the multiple rolling and annealing process of the ferritic stainless steel plate; specifically, the annealing temperature is 855-865°C, such as 860°C, and the annealing time is 1.5-2.5 minutes, such as 2 minutes. Studies have shown that multiple rolling and annealing of the ferritic stainless steel plate before composite is beneficial to make the grain clusters inside the ferritic stainless steel have a relatively similar orientation, which is beneficial to avoid wrinkling of the ferritic stainless steel on the outer wall of the composite plate when stamping.

[0013] In the present invention, there is no strict restriction on the thickness of the austenitic stainless steel plate, the aluminum alloy plate and the ferritic stainless steel plate in the blank, and they can be reasonably set according to actual needs; specifically, the thickness of the austenitic stainless steel plate in the blank can be 0.4-0.6mm, for example, 0.5mm; the thickness of the aluminum alloy plate can be 1.7-1.9mm, for example, 1.8mm; the thickness of the ferritic stainless steel plate can be 0.5-0.7mm, for example, 0.6mm; the shape and size of the blank are determined according to the stamping part, and the shape of the blank can be, for example, circular, and the diameter can be 380-400mm.

[0014] In the present invention, the stamping part can be a hollow cylindrical structure with an outer flange; in this case, the die used for stamping includes a male die and a female die that match the stamping part. It can be understood that the male die has a molding convex part and an outer flange part that match the stamping part. Studies have shown that due to the different layers of the composite sheet and the different properties of the materials, there are problems such as different flow rates during the stamping process, which leads to wrinkling on the surface, especially at a position 90° to the rolling direction (also called a position perpendicular to the rolling direction), where wrinkling is most obvious (such as Figure 1 At this time, by symmetrically setting the draw ribs at the outer flange positions on both sides of the punch in the vertical direction of rolling, that is, symmetrically adding the draw ribs at 90° along the rolling direction of the punch, the problem of uneven flow velocity and thickness variation of the material in all directions of the composite sheet during the stamping process can be overcome, thereby overcoming the undesirable phenomenon of wrinkling of the ferritic stainless steel on the outer wall of the composite sheet during stamping.

[0015] More specifically, the range of the symmetrically arranged draw beads can be 70°-110° and 250°-290° to the direction perpendicular to the rolling, respectively, that is, the starting position and the ending position of the draw beads on one side are located at the position of the outer flange of the punch at 70° and 110° to the direction perpendicular to the rolling, while the starting position and the ending position of the draw beads on the other side are located at the position of the outer flange of the punch at 250° and 290° to the direction perpendicular to the rolling; the shape of the draw beads is an arc, and the arc of the draw beads is concentric with the outer arc of the outer flange of the punch.

[0016] The distance between the draw rib and the protruding part of the punch can be 60-90mm, further 74-76mm, preferably 75mm; the height of the draw rib can be 15-25mm, further 18-22mm, preferably 20mm; the thickness can be 15-22mm, further 14-18mm, preferably 16mm; the transition radius can be 3-6mm, further 3-4mm, preferably 3mm; the edge radius of the die can be 11-13mm, preferably 12mm.

[0017] In the present invention, the friction coefficient between the composite plate and the mold after lubrication can be controlled to be 0.19-0.21, such as 0.2; in addition, the blank holding force during stamping can be controlled to be 165-175 kN, such as 170 kN.

[0018] The research shows that by controlling the thickness, height and other parameters of the drawbead within the above-mentioned appropriate range, and controlling the edge radius of the die, the friction coefficient, the blank holder force and other parameters within the above-mentioned appropriate range, the grain orientation in the SUS430 ferritic stainless steel plate can be further made more uniform, and the flow velocity of the composite plate along all directions of rolling during the stamping process can be more uniform, thereby better eliminating the wrinkling problem of the ferritic stainless steel on the outer wall of the composite plate when stamping, improving production efficiency and reducing production costs. It has important practical significance for solving the industry problem of wrinkling of the ferritic stainless steel on the outer wall of the composite plate when stamping. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is the appearance of the wrinkled outer wall of the ferritic stainless steel composite plate;

[0021] Figure 2 It is the main view of the punch;

[0022] Figure 3 for Figure 2 A magnified image of point A;

[0023] Figure 4 is a top view of the punch;

[0024] Figure 5 It is the main view of the stamping part;

[0025] Figure 6 for Figure 5AA section view;

[0026] Figure 7 for Figure 6 The enlarged view of point B;

[0027] Figure 8 It is a schematic diagram of various angles of the blank along the rolling direction;

[0028] Fig. 9 The metallographic structure of the SUS 430 outer wall of the stamping part at 0° along the rolling direction is magnified 500 times;

[0029] Fig.10 The metallographic structure of the outer wall of SUS 430 at 45° along the rolling direction is magnified 500 times;

[0030] Fig.11 The metallographic structure of the SUS 430 outer wall at 90° along the rolling direction is magnified 500 times;

[0031] Fig.12 This is a 100-fold magnified image of the outer wall cross section of Example 1;

[0032] Fig.13 This is a 100-fold magnified image of the outer wall cross section of Comparative Example 1.

[0033] Description of reference numerals:

[0034] 1: Punch; 11: Drawbead; 2: Die; 2: Austenitic stainless steel plate; 3: Aluminum alloy plate; 4: Ferritic stainless steel plate. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0037] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] The method of eliminating wrinkles of ferrite stainless steel on the outer wall of the composite plate formed by stamping in this embodiment comprises the following steps:

[0040] S1: Manufacturing blanks

[0041] The SUS 430 ferritic stainless steel plate was rolled and annealed for multiple times, with the annealing temperature being 860°C and the holding time being 2 min.

[0042] The SUS 304 austenitic stainless steel plate, the Al 1050 aluminum alloy plate and the SUS 430 ferritic stainless steel plate subjected to the above-mentioned multiple rolling and annealing treatments are rolled into composite plates, and the composite plates are cut to obtain blanks with a diameter of 390 mm and a thickness of 2.9 mm. The thicknesses of the SUS 304 austenitic stainless steel plate, the Al 1050 aluminum alloy plate and the SUS 430 ferritic stainless steel plate in the blanks are 0.5 mm, 1.8 mm and 0.6 mm, respectively.

[0043] S2: Preparation of mold

[0044] like Figures 2 to 4 As shown, draw ribs are symmetrically arranged on both sides of the outer flange part of the punch along the vertical direction of rolling, and the ranges of the symmetrically arranged draw ribs are respectively 70°-110° and 250°-290° to the vertical direction of rolling. The distance S between the draw ribs and the protruding part of the punch is 75mm, the height H is 20mm, the thickness B is 16mm, and the transition radius RB is 3mm; at the same time, the edge radius RA of the die is adjusted to 12mm to obtain a mold including a punch and a die.

[0045] S3: Preparation of stamping parts

[0046] The surfaces of the blank and the mold are lubricated, and the friction coefficient between the composite plate and the mold is controlled to be 0.2 after lubrication; then, the blank is placed on the mold for stamping, and the blank holding force is controlled to be 170kN during stamping to obtain a stamping part with a ferritic stainless steel plate as the outer wall, and its structure is as follows Figures 5 to 7 .

[0047] The metallographic structure of the outer wall of the stamping at various angles along the rolling direction is shown in Figures 8 to 11 , see the enlarged cross-section of the outer wall of the stamping part Fig.12 The wrinkling conditions are shown in Table 1.

[0048] Example 2

[0049] The method of eliminating wrinkles of ferrite stainless steel on the outer wall of the composite plate formed by stamping in this embodiment comprises the following steps:

[0050] S1: Manufacturing blanks

[0051] The SUS 304 austenitic stainless steel plate, the Al 1050 aluminum alloy plate and the SUS 430 ferritic stainless steel plate subjected to multiple rolling and annealing treatments in Example 1 were rolled into composite plates, and the composite plates were cut to obtain blanks with a diameter of 380 mm and a thickness of 2.8 mm. The thicknesses of the SUS 304 austenitic stainless steel plate, the Al 1050 aluminum alloy plate and the SUS 430 ferritic stainless steel plate in the blanks were 0.4 mm, 1.9 mm and 0.5 mm, respectively.

[0052] S2: Preparation of mold

[0053] Draw ribs are symmetrically arranged on both sides of the outer flange of the punch along the vertical direction of rolling. The ranges of the symmetrically arranged draw ribs are respectively 70°-110° and 250°-290° to the vertical direction of rolling. The distance S between the draw ribs and the protruding part of the punch is 74mm, the height H is 18mm, the thickness B is 14mm, and the transition radius RB is 4mm; at the same time, the edge radius RA of the die is adjusted to 11mm to obtain a mold including a punch and a die.

[0054] S3: Preparation of stamping parts

[0055] The surfaces of the blank and the mold are lubricated, and the friction coefficient between the composite plate and the mold is controlled to be 0.19 after lubrication; then, the blank is placed on the mold for stamping, and the blank holding force is controlled to be 175 kN during stamping to produce a stamped part with a ferritic stainless steel plate as the outer wall.

[0056] Example 3

[0057] The method of eliminating wrinkles of ferrite stainless steel on the outer wall of the composite plate formed by stamping in this embodiment comprises the following steps:

[0058] S1: Manufacturing blanks

[0059] The SUS 304 austenitic stainless steel plate, the Al 1050 aluminum alloy plate and the SUS 430 ferritic stainless steel plate subjected to multiple rolling and annealing treatments in Example 1 were rolled into composite plates, and the composite plates were cut to obtain blanks with a diameter of 400 mm and a thickness of 3.0 mm. The thicknesses of the SUS 304 austenitic stainless steel plate, the Al 1050 aluminum alloy plate and the SUS 430 ferritic stainless steel plate in the blanks were 0.6 mm, 1.7 mm and 0.7 mm, respectively.

[0060] S2: Preparation of mold

[0061] Draw ribs are symmetrically arranged on both sides of the outer flange of the punch along the vertical direction of rolling. The ranges of the symmetrically arranged draw ribs are respectively 70°-110° and 250°-290° to the vertical direction of rolling. The distance S between the draw ribs and the protruding part of the punch is 76mm, the height H is 22mm, the thickness B is 18mm, and the transition radius RB is 3mm; at the same time, the edge radius RA of the die is adjusted to 13mm to obtain a mold including a punch and a die.

[0062] S3: Preparation of stamping parts

[0063] The surfaces of the blank and the mold are lubricated, and the friction coefficient between the composite plate and the mold is controlled to be 0.21 after lubrication; then, the blank is placed on the mold for stamping, and the blank holding force is controlled to be 165kN during stamping to produce a stamped part with a ferritic stainless steel plate as the outer wall.

[0064] Comparative Example 1

[0065] Except that no draw ribs are provided on the punch, the rest is the same as in Example 1; the enlarged cross-section of the outer wall of the stamping part of this comparative example is shown in Fig.13 .

[0066] Comparative Example 2

[0067] Except that the fillet radius RA of the die edge is 10 mm, the blanking force F is 150 kN, and no draw ribs are provided on the punch, the rest is the same as Example 1.

[0068] Comparative Example 3

[0069] The above process is the same as Example 1 except that the SUS 430 ferritic stainless steel plate is not subjected to multiple rolling and annealing, the fillet radius RA of the die edge is 10 mm, the blank holding force F is 150 kN, and no drawbead is provided on the punch.

[0070] Test Example 1

[0071] The stamping parts of Example 1 and Comparative Examples 1-3 were processed. The materials and other processing parameters used in the processing were the same. After the processing was completed, the samples were cut at 90° along the rolling direction of each sample to prepare test specimens. The cross-section of the outer wall of SUS430 ferritic stainless steel at 90° along the rolling direction was observed under an electron microscope to determine whether the wrinkling was improved. The results are shown in Table 1.

[0072] Table 1 Comparison of experimental results between examples and comparative examples

[0073]

[0074] The results in Table 1 show that:

[0075] 1. Comparative Example 1 does not have draw ribs, and the material flow rate in all directions is uneven during the stamping process, so it can be observed that the outer wall of the SUS430 ferrite stainless steel still has obvious undulations;

[0076] 2. Comparative Example 2 does not set draw ribs and adopts other stamping parameters. During the stamping process, the flow velocity and thickness of the material in all directions change unevenly, causing serious wrinkling on the surface;

[0077] 3. Comparative Example 3 does not set draw ribs and adopts other stamping parameters. During the stamping process, the material flow velocity and thickness change unevenly in all directions; in addition, Comparative Document 3 does not perform multiple rolling and annealing on SUS430 ferritic stainless steel. There are grain clusters with different orientations inside SUS430 ferritic stainless steel, which aggravates the surface wrinkling phenomenon;

[0078] 4. The SUS430 ferritic stainless steel of Example 1 of the present invention is formed by multiple rolling and annealing before being compounded, so that the grain orientation in the SUS430 ferritic stainless steel is relatively uniform; by selecting appropriate stamping process parameters: die edge radius, friction coefficient, and clamping force, the uneven thickness variation of the material during the stamping process is reduced; by adding draw ribs at positions on the mold corresponding to fast material flow rates, and selecting appropriate thickness, height and other parameters for the draw ribs, the material at different locations along the rolling directions flows evenly during the stamping process, thereby achieving the purpose of eliminating wrinkling of the ferritic stainless steel on the outer wall of the composite plate during stamping.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for eliminating wrinkles on the outer wall of ferritic stainless steel formed by stamping a composite plate, characterized in that: The steps include: S1: making a composite plate from an austenitic stainless steel plate, an aluminum alloy plate and a ferritic stainless steel plate that has been subjected to multiple rolling and annealing treatments, and cutting the composite plate to obtain a blank; S2: Draw ribs are symmetrically arranged on both sides of the punch in the vertical rolling direction, and the edge fillet radius of the die is adjusted to obtain a die; S3: Lubricate the surfaces of the blank and the mold, and after lubrication, place the blank on the mold for stamping to obtain a stamping part with a ferritic stainless steel plate as an outer wall; The annealing temperature is 855-865℃, and the annealing time is 1.5-2.5min; the symmetrically arranged drawbeads are respectively at 70°-110° and 250°-290° positions perpendicular to the rolling direction, the drawbeads are in the shape of an arc, the cross-section of the drawbeads is rectangular, the arc of the drawbeads is concentric with the outer arc of the outer flange of the punch, the distance between the drawbeads and the protruding part of the punch is 74-76mm, the height of the drawbeads is 18-22mm, the thickness is 14-18mm, and the transition fillet is 3-4mm; the edge fillet radius of the die is 11-13mm; the blank holding force is controlled to be 165-175kN during stamping; the material of the austenitic stainless steel plate is SUS 304, the material of the aluminum alloy plate is Al 1050, and the material of the ferritic stainless steel plate is SUS 430; the thickness of the austenitic stainless steel plate in the blank is 0.4-0.6mm, the thickness of the aluminum alloy plate is 1.7-1.9mm, and the thickness of the ferritic stainless steel plate is 0.5-0.7mm; the diameter of the blank is 380-400mm; the friction coefficient between the blank and the mold after controlled lubrication is 0.19-0.21.

Images