Manufacturing method for composites of steel and resin

Abstract

To simplify chemical conversion process control on the surface of a steel material by using natural hydrolyzable tannin and improve environment in production, etc.SOLUTION: A method for treating the surface of a steel material comprises: immersing a steel plate piece having a cleaned fat content into a solution including hydrolyzable tannin of 0.5 wt.% for 30 seconds; cleaning the steel plate piece with ion exchange water to dry it by heating; inserting the steel plate piece into an injection molding die; and injecting a PBT, PPS or PP based resin composition by the conventional method to bond it to the steel plate piece. The shear strength of each obtained specimen can obtain a bonding strength of 15-25 MPa.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a steel / resin composite, and more particularly to a method for producing a steel / resin composite in which a naturally occurring hydrolyzable tannin is used for chemical conversion treatment of the surface of the steel when producing a composite in which steel and resin are bonded together. [Background technology]

[0002] Reducing the weight of automobiles significantly contributes to improving fuel efficiency and reducing carbon dioxide emissions. Therefore, in recent years, design techniques have been adopted, such as building car bodies out of composite materials rather than steel. Proposed lightweighting technologies include the use of lightweight materials such as high-tensile steel sheets and resins, as well as metal-resin composites. The present applicant has proposed an integration technology in which steel, such as general structural rolled steel, is joined to polyphenylene sulfide resin (PPS) or polybutylene terephthalate resin (PBT) by injection molding (Patent Document 1). This steel is then chemically treated with an inorganic acid such as sulfuric acid to form a thin, naturally occurring oxide coating with an ultrafine irregularity on its surface. This ultrafine irregularity is then coated with hydrazine or the like, inserted into an injection molding die, and the PPS or PBT is injected to produce a steel-resin composite.

[0003] On the other hand, a method is known in which a non-chromate agent such as tannin or tannic acid, a silane coupling agent, or fine silica is applied to a metal sheet such as an electrogalvanized steel sheet to dechromate the surface, and the dried coating layer is used as a base treatment layer, and then a resin composition containing a polyolefin resin, an acrylic olefin resin, a polyurethane resin, or the like is applied thereon and baked (Patent Document 2).Instead of simply using tannic acid alone, it has also been proposed to mix tannic acid with a resin having a phenol structure containing one or more of tannic acid and acetic acid, thereby improving the adhesion of the film coated thereon (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2009 / 011398 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-206921 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-355921 Summary of the Invention [Problem to be solved by the invention]

[0005] The chemical conversion treatment of steel surfaces described in the aforementioned Prior Art Document 1 uses hydrazine, ammonia, etc., but these chemical conversion treatment agents have pungent odors, are easily decomposed, and are flammable, making process management during the manufacturing process and ensuring a good working environment difficult. The non-chromate surface-treated metal sheet described in Patent Document 2 is prepared by applying and drying a chemical agent containing tannin or tannic acid, a silane coupling agent, and a trace amount of silica to form a base treatment layer, and then forming an upper layer consisting of an organic resin and a trace amount of silica on top of this. This method does not produce a metal-resin composite, but is a surface treatment method for metal sheets. Furthermore, the chemical conversion treatment of steel surfaces described in Prior Art Document 3 involves treating with tannic acid or acetic acid, etc., and then forming a resin coating with a phenolic structure to improve film adhesion, thereby coating the surface of a flat steel sheet with a film-like resin. The use of a film-like resin limits the shape and structure of the final product that can be manufactured.

[0006] The present invention has been made in view of the above background to achieve the following objects. An object of the present invention is to provide a method for producing a steel-resin composite, in which the surface of the steel is treated with a chemical conversion treatment using naturally occurring tannin or tannic acid, and then a resin is bonded to the steel by injection pressing, heat pressing, injection bonding, or the like. Another object of the present invention is to provide a method for producing a steel / resin composite which is free from the pungent odor of the treatment solution and which makes it easy to control the process. [Means for solving the problem]

[0007] The method for producing a steel and resin composite of the present invention 1 is as follows: A method for manufacturing a steel and resin composite, in which a steel material is reinforced by integrating a resin having a three-dimensional shape with the steel material, comprising: The method for producing the composite includes: Before the integration, a chemical conversion treatment step is performed in which the steel material is immersed in or coated with an aqueous solution of hydrolyzable tannin, After the chemical conversion treatment step, an integration step of integrating a resin having a three-dimensional shape onto the surface of the steel material by one method selected from injection molding, hot press molding, and injection press molding, and reinforcing the steel material with the resin; the law of nature, The hydrolyzable tannin is Plant-derived Tannic acid and / or tannins extracted from chestnut, miraboleum, tara, and oak. the law of nature, The steel material is characterized in that it is one selected from general structural rolled steel material, mechanical structural carbon steel, mechanical structural alloy steel, cold-rolled steel plate, hot-rolled steel plate, structural high-tensile steel plate, and hot-rolled steel plate. The method for producing a steel and resin composite of Invention 2 is Invention 1, 10. A method for producing a steel / resin composite, wherein the aqueous solution of hydrolyzable tannin is an aqueous solution to which an inorganic acid is further added and mixed.

[0008] The method for producing a steel and resin composite of Invention 3 is characterized in that, in Invention 1, a chemical etching step is carried out before the chemical conversion treatment step, in which the steel is immersed in or coated with an aqueous solution of an inorganic acid to chemically etch the surface. The method for manufacturing a composite of steel and resin according to the present invention 4 is 2 The inorganic acid is one selected from hydrochloric acid, hydrohalic acid, sulfurous acid, sulfuric acid, phosphoric acid, and salts thereof, and the concentration of the aqueous solution of the inorganic acid is 1.00 to 10.00 wt %.

[0009] The method for manufacturing a composite of steel and resin according to the present invention 5 is 3 The method is characterized in that after the chemical etching step, a cleaning step is performed in which the steel material is cleaned with water. The method for manufacturing a composite of steel and resin according to the present invention 6 is 3 The present invention is characterized in that, before the chemical conversion treatment step and / or the chemical etching step, one or more selected from holes, through-holes, gaps, and irregularities are formed in the steel material to bond it to the resin by an anchor effect.

[0010] The method for producing a composite of steel and resin according to the seventh invention is the same as that according to the first to fifth inventions. 6 The temperature of the chemical conversion treatment solution, which is an aqueous solution of hydrolyzable tannin, is between room temperature and 80°C as specified by the Japanese Industrial Standards, and the concentration of the aqueous solution of hydrolyzable tannin is between 0.01 and 10.00 wt%. The method for manufacturing a composite of steel and resin according to the present invention 8 is 7 The method is characterized in that the temperature of the chemical conversion treatment solution is 40° C. to 60° C., and the concentration of the aqueous solution of hydrolyzable tannin is 0.05 to 5.00 wt %.

[0011] Steel material of invention 9 and resin composite manufacturing method The present invention 1 to 6 The method is characterized in that it includes a shaping step of shaping the steel material by mechanical processing before the chemical etching step and / or the chemical conversion treatment step. The method for producing a composite of steel and resin according to the present invention 10 is the same as that according to the present invention 1 to 6After chemical conversion treatment of the steel material, the steel material is inserted into an injection molding die, and the resin is one type of resin composition selected from a first resin composition mainly composed of polyphenylene sulfide resin, a second resin composition mainly composed of polybutylene terephthalate resin, a third resin composition which is a resin composition mainly composed of one type of aliphatic polyamide resin or a mixture of different types of aliphatic polyamide resins, or a fourth resin composition mainly composed of polypropylene.

[0015] The above-mentioned configurations of the present invention will be described in detail below. [Steel] The term "steel" as used herein refers to carbon steels such as rolled steels for general structures, low-temperature steels, and steel plate materials for nuclear reactors, including cold-rolled steels (hereinafter referred to as "SPCC"), hot-rolled steels (hereinafter referred to as "SPHC"), hot-rolled steels for automotive structures (hereinafter referred to as "SAPH"), and hot-rolled high-tensile steels for automotive processing (hereinafter referred to as "SPFH"), as well as materials used for machine parts, etc. Many of these can be pressed and cut, allowing for flexible selection of structure and shape when used as the main body of a part, machine, etc. Furthermore, the term "steel" as used herein is not limited to the above-mentioned steels but also includes any steels standardized by, for example, the Japanese Industrial Standards (JIS "SS400"), etc.

[0016] [Machining] The mechanical processing referred to in the present invention refers to general mechanical processing such as cutting, grinding, pressing, welding, and laser processing. These mechanical processing processes are usually performed before the above-mentioned "chemical conversion treatment process" and "chemical etching process," but may also be performed after the process. However, when performing mechanical processing after the "chemical conversion treatment process" and "chemical etching process," cold processing is preferred, and hot processing, which is a plastic processing performed by heating metal to a temperature above the recrystallization temperature, is not preferred. In order to strengthen the bond between the resin and the steel material by this mechanical processing, it is preferable to form holes, through-holes, gaps, irregularities, etc. on the surface or inside of the steel material, and fill the interior with resin to provide an anchor effect.

[0017] [Surface treatment after machining] Machined steel materials are contaminated with oxides, oil, machining fluids, etc. Therefore, although not essential requirements of the present invention, it is recommended to degrease and wash using a degreasing agent or the like and pickle using conventional methods before the subsequent "chemical conversion treatment step" and "chemical etching step." Impurities such as welding scale, black scale from heat treatment, and rust generally remain on the surface of the steel material. After degreasing and washing, it is preferable to immerse the degreased steel material in a strong acid immersion bath and pickle it to remove these impurities and improve product quality. This pickling is carried out using conventional methods, such as a 5-10 wt% (by weight) sulfuric acid solution at a temperature of 65-88°C for an immersion time of approximately 5-20 minutes. In the case of a hydrochloric acid solution, a 5-10 wt% solution at 20-40°C is used. After this pickling, the steel material is thoroughly washed with clean water and dried. If necessary, the cleaning water may be washed quickly after pickling, and neutralization may be performed by immersing the steel in a 1.5 wt % aqueous solution of caustic soda at 40°C for about 1 minute.

[0018] [Hydrolyzable tannins] The hydrolyzable tannins used in this invention are plant-derived tannins extracted from gallnut, chestnut, miraborum, tara, oak, and other plants. One or a mixture of these is dissolved in water to form a solution. Plant tannins (polyphenols) are a type of polyphenolic compound found in plants and are water-soluble. An aqueous solution containing one or more of these hydrolyzable tannins is prepared, and the steel material is immersed in the solution, or the steel surface is coated or sprayed with the solution to adhere the hydrolyzable tannin to the steel surface. The term "tannic acid" used in this invention refers to CAS registration number 1401-55-4 and is typically extracted and purified from gallnut and other plants. Chestnut is a tannin extracted from Castania sativa, a beech tree found in Italy and France. Miraborum is a tannin extracted from the nut-like flesh of the Terminalia chebula (Miraborum) tree found in India and Sri Lanka. Tara is a tannin extracted from the fruit pods of Caesarvinia trees, which grow abundantly in Peru. Oak is extracted from the bark and wood of European and North American oak trees.

[0019] [Chemical conversion treatment process] The chemical conversion treatment step referred to in the present invention is a step of immersing or coating a steel material in the above-mentioned aqueous solution of hydrolyzable tannin. The temperature is between room temperature (5 to 35°C) and 80°C, preferably between 40°C and 60°C, the immersion time is between a few seconds and 60 minutes, and the concentration of the tannin in the aqueous solution is preferably between 0.01 and 10.00 wt%. This chemical conversion treatment step may also be a method of immersing the steel material in a mixed solution of the above-mentioned aqueous solution of hydrolyzable tannin and an aqueous solution of an inorganic acid such as sulfuric acid. By adding an inorganic acid, this process can also be used as pickling. The immersion temperature for this mixed solution is between 40°C and 60°C, the immersion time is between a few seconds and 60 minutes, and the concentration of the tannin in the aqueous solution is preferably between 0.10 and 5.00 wt%, and the concentration of the inorganic acid in the aqueous solution is preferably between 0 and 10.00 wt%. This chemical conversion treatment step involves immersing the steel material in an immersion tank filled with the above aqueous solution, and the solution is applied to the surface of the steel material by brushing, spraying, or the like.

[0020] [Resin composition] The resin composition used in the present invention refers to one type of resin composition selected from the group consisting of a first resin composition primarily composed of polyphenylene sulfide resin (PPS), a crystalline resin; a second resin composition primarily composed of polybutylene terephthalate resin (PBT); a third resin composition primarily composed of an aliphatic polyamide resin or a mixture of different aliphatic polyamide resins; or a fourth resin composition primarily composed of polypropylene. The resin component of the first resin composition is a resin composition primarily composed of polyphenylene sulfide resin (PPS) with a polyolefin-based resin as a minor component. The resin component of the second resin composition is a resin composition primarily composed of polybutylene terephthalate resin (PBT) with a polyethylene terephthalate resin and / or a polyolefin-based resin as a minor component.

[0021] The first resin composition may be 70 to 97% by weight of the polyphenylene sulfide resin and 3 to 30% by weight of the polyolefin resin. The second resin composition may be 70 to 97% by weight of the polybutylene terephthalate resin and 3 to 30% by weight of the polyethylene terephthalate resin and / or the polyolefin resin. When different materials are mixed at the molecular level, they are not immediately mixed with the same materials even when the temperature reaches the crystallization temperature, and it is estimated that there is a slight time delay in the formation of microcrystals and the growth of crystals.

[0022] The polyamide resin of the third resin composition used in the present invention is a polyamide primarily composed of an amino acid, a lactam, or a diamine and a dicarboxylic acid. The third resin composition may be a resin composition primarily composed of a single aliphatic polyamide resin or a mixture of different aliphatic polyamide resins, or a resin composition primarily composed of a single aromatic polyamide resin or a mixture of different aromatic polyamide resins. That is, the polyamide resin may be a single aliphatic polyamide, a single aromatic polyamide, or a mixture of these different materials. Specific examples of aliphatic polyamides include PA6, PA11, PA12, PA46, PA66, and PA610. Examples of aromatic polyamides include PA6T, PA6I, PA9T, and Nylon MXD6 (manufactured by Mitsubishi Gas Chemical Company, Inc. (Head office: Tokyo, Japan)). It is practically advantageous to use a single polyamide resin or a mixture of different materials as the primary component, depending on the required properties, such as moldability and compatibility. That is, it is preferable to use these polyamide resins as the main component, and to add fibers such as carbon fibers and glass fibers, fillers, etc., as needed, to improve mechanical properties.

[0023] The fourth resin composition is a resin composition containing polypropylene as a main component. The polypropylene of the fourth resin composition referred to in the present invention is a general-purpose resin, and refers to, for example, a resin containing a crystalline isotactic polymer as a main component and an atactic polymer as a minor component. These first to fourth resin compositions are preferably mixed, as necessary, with one or more fillers selected from glass fiber, carbon fiber, aramid fiber, other reinforcing fibers, calcium carbonate, magnesium carbonate, silica, talc, clay, and glass powder in a conventional manner. This is because the inclusion of these fillers increases the linear expansion coefficient of the resin molded product to 2 to 3 × 10. -5 / K, in order to make it as close as possible to the linear expansion coefficient of the steel material and make it small.

[0024] [Joining of steel and resin composition] The joining of the steel material and the resin composition of the present invention is carried out by an integration step in which the resin composition is integrated onto the surface of the steel material by one method selected from injection molding, hot press molding, and injection press molding. steel The material is inserted into an injection mold, the injection mold is closed, and a resin composition is injected into the cavity. steel material This refers to joining a resin composition with a resin. This is a type of general injection molding method. These injection molding conditions are general injection molding conditions required for the resin composition. The hot press of the present invention refers to a method in which a heated and softened resin composition is joined in a mold by applying pressure with a press. The injection press of the present invention is a molding method that combines injection molding and hot press molding.

[0025] [Chemical etching of steel using inorganic acids] Chemical etching of steel materials, as used herein, refers to a process using inorganic acids to create a surface roughness of the order of several microns to several tens of microns. Chemical etching is performed as a pretreatment for chemical conversion coating. Steel materials can be subject to various types of corrosion, including general corrosion, pitting corrosion, and fatigue corrosion. An appropriate etching agent can be selected through trial and error by selecting the type of chemical that causes general corrosion. Generally, steel materials are subjected to general corrosion in aqueous solutions of hydrohalic acids such as hydrochloric acid, sulfurous acid, sulfuric acid, and their salts. While the corrosion rate and corrosion pattern vary depending on the amount of carbon, chromium, vanadium, molybdenum, and other small additives, the aforementioned aqueous solutions generally cause general corrosion. Therefore, the immersion conditions can be adjusted depending on the type of steel material. The concentration of the inorganic acid aqueous solution used for steel materials is 1.00 to 2.00 wt %, and the treatment is performed at room temperature.

[0026] A specific treatment method will be described. First, for commonly used commercially available steel materials such as the aforementioned SPCC, SPHC, SAPH, SPFH, and SS, a degreaser for ferrous materials, a degreaser for stainless steel, a degreaser for aluminum alloys, or even a commercially available neutral detergent for general use is obtained, and the aqueous solution is prepared according to the concentration indicated in the degreaser manufacturer's instructions, or at a concentration of several percent, at a temperature of 40 to 70°C, and the material is immersed for 5 to 10 minutes and rinsed with water. After this degreasing and cleaning, the above-mentioned chemical etching is carried out.

[0027] Surface treatment of steel: Water washing and forced drying method After chemical etching, the steel is washed with water, dried, and observed under an electron microscope at 10,000x or 100,000x magnification. A shape resembling an infinite series of steps, each 50-500 nm high and deep, and several hundred to several thousand nm wide, is obtained. Depending on the type of steel material, the surface is covered with a shape that resembles an infinite series of steps, each 80-200 nm high and deep, and several hundred to several thousand nm wide, or a shape that resembles an infinite series of steps, each 50-100 nm high and deep, and several hundred to several thousand nm wide. Chemical etching of general steel often results in a unique, step-like micro-irregularity, completely different from the micro-surface structures the inventors have experienced after chemical etching of other metal alloys, such as aluminum alloys, titanium alloys, copper alloys, and stainless steel.

[0028] Furthermore, as mentioned above, the step height and step width (depth) of the steps varied depending on the type of steel, i.e., its chemical composition and tempering (heat treatment and rolling methods). In any case, overall, chemical etching using a sulfuric acid solution alone was sufficient to simultaneously achieve a roughness on the order of microns to tens of microns and to form a fine irregularity (a fine irregularity with an infinite series of steps with heights and depths of 50-500 nm and widths of several hundred to several thousand nm). To implement this process specifically, it is necessary to add an appropriate second component to the sulfuric acid solution to impart a special etching effect, or to use the solution under appropriate conditions, such as varying the temperature and immersion time. [Effects of the Invention]

[0029] The method for producing a steel and resin composite of the present invention involves treating the surface of the steel with a chemical conversion treatment using naturally occurring tannin or tannic acid, and then joining the resin to the steel by injection molding, which is free from the irritating odor of the treatment solution and makes process management easy. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 shows an external view of an injection-bonded product for measuring the shear bond strength between the metal part and the resin part in a metal-resin bonded integrated product specified in ISO19095. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, an embodiment of the present invention will be described as an experimental example of a working example. [Example]

[0032] [Experimental Example 1] A 1.6 mm thick high-tensile cold-rolled steel sheet (JFE-CA1180Y2, manufactured by JFE Steel Corporation, headquartered in Tokyo, Japan) was cut to prepare rectangular steel sheet pieces measuring 18.0 × 45.0 × 1.6 mm. Next, an aqueous solution containing 7.5% aluminum alloy degreaser (NE-6, manufactured by Meltex Inc., headquartered in Tokyo, Japan) was placed in an immersion bath at 60°C, and the steel sheet pieces were immersed for 5 minutes, after which they were rinsed with public tap water (Ota City, Gunma Prefecture).

[0033] Bonding immersion treatment (chemical treatment) The steel sheet pieces that had undergone the above treatment were immersed in another immersion tank for 30 seconds in an aqueous solution containing 0.5 wt% tannic acid (aqueous, manufactured by Kishida Chemical Co., Ltd., headquartered in Osaka, Japan), and then washed with ion-exchanged water. They were then heated and dried for 15 minutes in an air-blowing dryer set at a temperature of 80°C. Note that treating the surface with ion-exchanged water after treatment with tannic acid allows removal of surface deposits, impurities, and the like.

[0034] injection joining The heat-dried steel sheet was inserted into an injection molding die, and a polyphenylene sulfide resin (hereinafter referred to as "PPS")-based composition (e.g., GF-containing "SGX120" (Tosoh Corporation, head office: Tokyo, Japan)) (hereinafter referred to as "SGX120") was injected into it using a standard method to bond the steel sheet and produce an injection-bonded product (type B test piece) with the shape shown in Figure 1.

[0035] Shear Break Test The bond strength of these test pieces was measured using the "Test Method for Evaluating Resin-Metal Bonding Characteristics" (ISO19095-2) (see Figure 1). The shear breaking strength of each test piece was 15 to 25 MPa, and a consistent bond strength was obtained.

[0036] [Comparative Example 1] (Tannic acid not used) The steel sheet pieces of Comparative Example 1 were not subjected to the immersion treatment in tannic acid, which is the "bonding immersion treatment" (chemical conversion treatment) of Experimental Example 1 above. All other steel sheet pieces, resins, etc. were made from the same materials and were subjected to the same chemical conversion treatment to produce test pieces. The shear rupture strength of these test pieces was 0 to 8 MPa. This result revealed that without the immersion treatment in tannic acid, bonding would not occur or the shear rupture strength would be weak.

[0037] [Experimental Examples 2-4] (using hydrolyzed tannins) The steel sheet pieces in Experimental Examples 2 to 4 were treated with the hydrolyzable tannins chestnut, miraboleum, and tara shown in Table 1 below, instead of the tannic acid used in the bonding immersion treatment in Experimental Example 1. The treatment concentration and immersion time were the same as those in Experimental Example 1. Chestnut, miraboleum, and tara tannins are known as hydrolyzable or hydrolyzable / condensed tannins. Tara, which has properties of both hydrolyzable and condensed tannins, has a shear breaking strength similar to that of tannic acid. [Table 1]

[0038] [Comparative Examples 2 to 4] (Condensed tannins used) For Comparative Examples 2 to 4, test pieces were prepared in the same manner as in Example 1. The treatments different from those in Example 1 were that instead of tannic acid, which was used in the immersion bonding treatment (chemical conversion treatment), treatments were performed with Gambia, Mimosa, and Kepracho, which are known as condensed tannins, as shown in Table 2 below. The treatment concentrations, immersion times, and resins used for injection bonding were the same as those in Experimental Example 1. The shear breaking strength of these test pieces was 0 to 8 MPa. These results revealed that immersion treatments using condensed tannins either did not result in bonding or had significantly weaker shear breaking strength. The experimental results for shear breaking strength are shown in Table 2 below. [Table 2]

[0039] [Comparative Example 5] (using only mineral acid) In the above-mentioned Experimental Example 1, tannic acid was used in the "dip-bonding treatment." In Comparative Example 5, instead of using tannic acid, an aqueous solution containing 5 wt% of 98% sulfuric acid at a temperature of 60°C was prepared in an immersion bath, and the steel sheet pieces were immersed in this for 10 minutes, and then washed with ion-exchanged water. This was then heated and dried for 15 minutes in an air-blowing dryer set to a temperature of 67°C. The results of Comparative Example 5 revealed that even without using tannic acid in the "dip-bonding treatment," a certain level of shear breaking strength (20 to 30 MPa) could be obtained even for steel sheets whose surfaces had been chemically treated with an inorganic acid (mineral acid) such as sulfuric acid or hydrochloric acid to form a finely textured surface.

[0040] [Experimental Examples 5-7] (using a mixture of tannins and sulfuric acid, and PPS resin) In the aforementioned Experimental Example 1, only tannic acid was used in the "bonding immersion treatment," but Experimental Examples 5 to 7 are experimental examples in which treatment was performed with a mixed solution of tannins and sulfuric acid. In Experimental Example 5, a steel sheet was immersed for 10 minutes in a mixed solution of an aqueous solution containing 0.5 wt% tannic acid and 5 wt% 98% sulfuric acid, which was set to a temperature of 60°C in an immersion bath, and then washed with ion-exchanged water. It was found that the aforementioned "bonding immersion treatment," which was chemically treated with an inorganic acid such as sulfuric acid and hydrolyzed tannin, could achieve a shear breaking strength (38 to 42 MPa).

[0041] [Experimental Example 8] (using a mixture of tannins and sulfuric acid, polyamide resin) Experimental Example 8 involved the same immersion treatment as Experimental Example 5, using a mixture of tannin and sulfuric acid for joining, and the same method of preparing the test specimens. However, instead of the resin "SGX120" used for injection joining in Experimental Example 5, a carbon fiber-containing polyamide resin composition "Plastron (registered trademarks: PA6-CF40 (nylon 6), PA66-CF40 (nylon 66), and PA9T-CF-40 (nylon 9T) manufactured by Daicel Corporation (headquarters: Osaka, Japan))" was used. The shear strength was 45 to 55 MPa. The resin using the carbon fiber-containing polyamide resin composition had a higher shear strength than that of Experimental Example 5 due to the effect of the carbon fiber.

[0042] [Experimental Example 9] (Use of a mixture of tannins and sulfuric acid, and polypyrron (PP) resin) Experimental Example 9 was a dipping treatment using a mixture of tannin and sulfuric acid, similar to Experimental Example 5, and the test specimens were also prepared in the same manner. However, instead of the resin "SGX120" used for injection joining in Experimental Example 5, a carbon fiber-containing polypropylene resin composition "Plastron (registered trademark: PP-CF40-11(L9), manufactured by Daicel Corporation (head office: Osaka, Japan))" was used. The shear strength was 18 to 25 MPa.

[0043] [Experimental Example 10] (Surface treatment with inorganic acid before chemical conversion treatment) In Experimental Example 10, the steel surface was treated with tannic acid as in Experimental Example 1, and the resin (PPS-based resin) was also the same. However, the difference was that the steel sheet was treated with an inorganic acid (chemical etching) before the tannic acid immersion treatment. Specifically, the steel sheet was immersed in an aqueous solution containing 5 wt% of 98% sulfuric acid at 60°C in an immersion bath for 10 minutes, followed by rinsing with ion-exchanged water. Next, the steel sheet was immersed in a room-temperature aqueous solution containing 0.5 wt% hydrolyzed tannic acid in another immersion bath for 30 seconds, followed by rinsing with ion-exchanged water. The steel sheet was then heated and dried in an air-blowing dryer at 67°C for 15 minutes. The resin and other materials used for injection joining were the same as in Experimental Example 1. A shear strength of 38-42 MPa, approximately the same as in Experimental Example 5, was obtained, and the fracture surface was characterized by cohesive failure of the resin.

[0044] [Experimental Example 11] (Tannic acid unwashed) In Experimental Example 11, the steel surface was treated with tannic acid in the same chemical conversion treatment as in Experimental Example 1, and the resin used (PPS-based resin) was also the same. However, after the tannic acid treatment, the steel was not washed with ion-exchanged water. In other words, the steel was dried with the tannic acid still remaining. Specifically, the steel was immersed in an aqueous solution containing 0.5 wt% hydrolyzed tannic acid at room temperature in an immersion bath for 30 seconds, and then, without washing, was heated and dried for 15 minutes in an air-blowing dryer set to a temperature of 80°C. The resin and other materials used in injection joining were the same as in Experimental Example 1. A shear strength of 15 to 25 MPa, almost the same as in Experimental Example 5, was obtained, and the fracture surface was due to cohesive failure of the resin. [Industrial Applicability]

[0045] The composite of steel and resin of the present invention can be used as a component for automobile bodies, various industrial equipment, civil engineering machine bodies, parts, etc., and has the advantage of being mainly lightweight. In addition, since it is a composite material, it can be expected to have effects such as vibration damping.

Claims

1. A method for manufacturing a steel and resin composite, in which a steel material is reinforced by integrating a resin having a three-dimensional shape with the steel material, comprising: The method for producing the composite includes: Before the integration, a chemical conversion treatment step is performed in which the steel material is immersed in or coated with an aqueous solution of hydrolyzable tannin, an integration step of integrating a resin having a three-dimensional shape onto the surface of the steel material by one method selected from injection molding, hot press molding, and injection press molding after the chemical conversion treatment step, and reinforcing the steel material with the resin; The hydrolyzable tannin is one selected from plant-derived tannic acid and / or tannins extracted from chestnut, miraboleum, tara, and oak; The steel material is one selected from general structural rolled steel material, mechanical structural carbon steel, mechanical structural alloy steel, cold-rolled steel plate, hot-rolled steel plate, structural high-tensile steel plate, and hot-rolled steel plate. A method for manufacturing a composite of steel and resin.

2. In the method for manufacturing a steel and resin composite according to claim 1, The aqueous solution of hydrolyzable tannin is an aqueous solution to which an inorganic acid is further added and mixed. A method for manufacturing a composite of steel and resin.

3. In the method for manufacturing a steel and resin composite according to claim 1, Before the chemical conversion treatment step, a chemical etching step is performed in which the steel material is immersed in or coated with an aqueous solution of an inorganic acid to chemically etch the surface. A method for manufacturing a composite of steel and resin.

4. In the method for manufacturing a steel and resin composite according to claim 2, The inorganic acid is one selected from hydrochloric acid, hydrohalic acid, sulfurous acid, sulfuric acid, phosphoric acid, and salts thereof; The concentration of the aqueous solution of the inorganic acid is 1.00 to 10.00 wt %. A method for manufacturing a composite of steel and resin.

5. In the method for manufacturing a steel and resin composite according to claim 3, After the chemical etching step, a cleaning step is performed in which the steel material is washed with water. A method for manufacturing a composite of steel and resin.

6. In the method for manufacturing a steel and resin composite according to claim 3, Before the chemical conversion treatment step and / or the chemical etching step, one or more selected from holes, through-holes, gaps, and irregularities are formed in the steel material to bond it to the resin by an anchor effect. A method for manufacturing a composite of steel and resin.

7. A method for producing a composite of steel and resin according to any one of claims 1 to 6, The temperature of the chemical conversion treatment solution, which is an aqueous solution of hydrolyzable tannin, is between room temperature and 80°C as specified by the Japanese Industrial Standards, The concentration of the hydrolyzable tannin in the aqueous solution is 0.01 to 10.00 wt %. A method for manufacturing a composite of steel and resin.

8. 8. The method for manufacturing a steel and resin composite according to claim 7, the temperature of the chemical conversion treatment solution is 40°C to 60°C, The concentration of the aqueous solution of hydrolyzable tannin is 0.05 to 5.00 wt %. A method for manufacturing a composite of steel and resin.

9. 7. The method for producing a steel and resin composite according to claim 1, A shaping step of shaping the steel material by mechanical processing is included before the chemical etching step and / or the chemical conversion treatment step. A method for manufacturing a composite of steel and resin.

10. 7. The method for producing a steel and resin composite according to claim 1, After the chemical conversion treatment of the steel material, the steel material is inserted into an injection molding die; The resin is one type of resin composition selected from a first resin composition mainly composed of polyphenylene sulfide resin, a second resin composition mainly composed of polybutylene terephthalate resin, a third resin composition which is a resin composition mainly composed of one type of aliphatic polyamide resin or a mixture of different types of aliphatic polyamide resins, or a resin composition mainly composed of one type of aromatic polyamide resin or a mixture of different types of aromatic polyamide resins, and a fourth resin composition mainly composed of polypropylene. A method for manufacturing a composite of steel and resin.

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