High-strength fatigue-resistant stainless steel chassis support for automobile and preparation method of high-strength fatigue-resistant stainless steel chassis support

Abstract

The invention relates to the technical field of coatings, and discloses a high-strength fatigue-resistant stainless steel chassis support for an automobile and a preparation method of the high-strength fatigue-resistant stainless steel chassis support. Comprising the following operation steps: uniformly mixing an isocyanate-terminated prepolymer, siloxane modified polyaspartic acid ester, epoxy resin, a modified glass flake composite material, a curing agent and a solvent to obtain a functional coating; and the surface of the prefabricated stainless steel chassis support is coated with the functional coating, temperature programming curing is conducted, and the high-strength fatigue-resistant stainless steel chassis support is obtained. In the scheme, the isocyanate-terminated prepolymer and the siloxane-modified polyaspartic ester form a polyurea / polyurethane structure, so that the performance of the coating is improved; the glass flakes are modified to improve the compatibility with the coating and cooperate with the coating matrix, so that the performance of the stainless steel chassis bracket is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating technology, and in particular to a high-strength fatigue-resistant stainless steel chassis support for automobiles and a preparation method thereof. BACKGROUND

[0002] The chassis support of an automobile is a key load-bearing component connecting the vehicle body and the suspension system, and its performance is directly related to the safety, handling stability and durability of the whole vehicle. Currently, stainless steel materials are widely used to prepare chassis supports, which can meet the basic strength requirements, but are prone to corrosion fatigue failure under the combined action of long-term bearing of complex alternating stress and harsh corrosion environment, resulting in a decrease in strength or even rupture, which poses a safety hazard.

[0003] In the prior art, in order to improve the corrosion resistance of stainless steel, surface treatment technologies such as electroplating are often used. However, the bonding force of the traditional plating layer with the substrate is limited, and the single metal plating layer is insufficient in improving the impact resistance and fatigue resistance. In addition, some studies use organic coatings for protection, but ordinary coatings have poor adhesion and other problems, and are prone to cracking and peeling under dynamic load, ultimately losing the protection ability.

[0004] In view of the above, it is of great significance to prepare a high-strength fatigue-resistant stainless steel chassis support for automobiles. SUMMARY

[0005] The present application aims to provide a high-strength fatigue-resistant stainless steel chassis support for automobiles and a preparation method thereof to solve the problems in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A preparation method of a high-strength fatigue-resistant stainless steel chassis support for automobiles, comprising the following operation steps: Step 1: uniformly mix isocyanate-terminated prepolymer, siloxane-modified polyaspartic ester, epoxy resin, modified glass flake composite material, curing agent and solvent to obtain a functional coating; Step 2: (1) acid pickling, water washing, electroplating zinc and annealing of the stainless steel chassis support to obtain a pre-prepared stainless steel chassis support; (2) coating the functional coating on the surface of the pre-prepared stainless steel chassis support and curing by programmed temperature rise to obtain a high-strength fatigue-resistant stainless steel chassis support.

[0007] In the scheme, the material of the stainless steel chassis support is high-nitrogen austenitic stainless steel.

[0008] More preferably, the raw materials of the functional coating include the following components: 30-40 parts of isocyanate-terminated prepolymer, 15-25 parts of siloxane-modified polyaspartic ester, 8-14 parts of epoxy resin, 10-20 parts of modified glass flake composite, 1-3 parts of curing agent, and 15-20 parts of solvent.

[0009] More preferably, the process conditions of the programmed temperature curing are as follows: 1-2 hours of heat preservation at 50-60℃, 2-4 hours of heat preservation at 80-90℃, and 1-2 hours of heat preservation at 120-130℃.

[0010] More preferably, in the process of electro-galvanizing, the raw materials of the zinc plating solution include the following components: 40-60 g / L of zinc chloride, 70-90 g / L of potassium chloride, 10-15 g / L of boric acid, and 30-50 mL / L of brightener. The electroplating process parameters are as follows: temperature of 20-25℃, electroplating density of 20-30 A / dm 2 , and time of 2-4 minutes. The process conditions of the annealing are as follows: annealing temperature of 120-150℃ and annealing time of 30-60 minutes.

[0011] More preferably, the preparation method of the modified glass flake composite is as follows: (1) Under nitrogen protection, hydroxypropyl-terminated polydimethylsiloxane is added into toluene, and an acid-binding agent is added. Under ice water bath, 2-bromoisobutyryl bromide-toluene solution is added, and stirring reaction is carried out at room temperature for 6-8 hours to obtain bromo-polydimethylsiloxane. (2) Methyl methacryloyloxy glass flake and vinyl imidazole are added into methanol aqueous solution, and ultrasonic dispersion and degassing treatment are carried out. Under nitrogen protection, bromo-polydimethylsiloxane-toluene solution, 2,2'-dipyridyl, and copper bromide are sequentially added, and stirring reaction is carried out under light shielding for 20-25 hours. After washing and drying, the modified glass flake composite is obtained.

[0012] More preferably, the raw materials of the bromo-polydimethylsiloxane include the following components: 8-10 parts of hydroxypropyl-terminated polydimethylsiloxane, 2-4 parts of 2-bromoisobutyryl bromide, and 3-4 parts of acid-binding agent. The raw materials of the modified glass flake composite include the following components: 7-10 parts of methyl methacryloyloxy glass flake, 2-4 parts of vinyl imidazole, 1-2 parts of bromo-polydimethylsiloxane, 0.5-0.7 parts of 2,2'-dipyridyl, and 0.1-0.15 parts of copper bromide.

[0013] In the scheme, the hydroxypropyl-terminated polydimethylsiloxane is acylated with 2-bromoisobutyryl bromide to obtain a macromolecular initiator monomer that can initiate ATRP reaction, and the bromo-polydimethylsiloxane containing isobutyryl at the end is obtained. Then, the bromo-polydimethylsiloxane is used as an initiator to generate free radicals under the catalysis of copper bromide and 2,2'-bipyridine, and the methacryloyloxy-glass flake and vinyl imidazole are copolymerized to obtain a modified glass flake composite.

[0014] The preparation method of the methacryloyloxy-glass flake is as follows: glass flakes are crushed and sieved, added to a 2M sodium hydroxide solution and stirred for 2 hours, washed with ethanol until neutral, and dried to obtain pre-prepared glass flakes; 16 parts of γ-methacryloyloxypropyltrimethoxysilane are added to an ethanol aqueous solution (the concentration of ethanol in the ethanol aqueous solution is 90 wt%), mixed, the pH is adjusted to 4.5, stirred for 1 hour, 20 parts of pre-prepared glass flakes are added, stirred at 65°C for 3 hours, filtered, washed, and dried to obtain the methacryloyloxy-glass flake; the parts are all mass parts.

[0015] More preferably, the preparation method of the isocyanate-terminated prepolymer is as follows: under nitrogen protection, the hydroxypropyl-terminated polydimethylsiloxane is dehydrated, mixed with diphenylmethane diisocyanate, a catalyst is added, stirred at 40-50°C for 1-2 hours, and then heated to 80-90°C and stirred for 2-4 hours to obtain the isocyanate-terminated prepolymer. The mass ratio of the hydroxypropyl-terminated polydimethylsiloxane to the diphenylmethane diisocyanate is 1:1.2-1.4.

[0016] More preferably, the preparation method of the siloxane-modified polyaspartic acid ester is as follows: (1) diphenylsilanediol, barium hydroxide, and γ-glycidyl ether oxypropyltrimethoxysilane are uniformly mixed, and stirred to react under a nitrogen atmosphere to obtain branched epoxy phenyl siloxane; (2) under nitrogen protection, the branched epoxy phenyl siloxane and polyether amine are uniformly mixed, stirred at 80-90°C for 8-10 hours, cooled to 50-60°C, and then dropwise added with maleic acid diethyl ester, and heated to 80-90°C to continue stirring to obtain the siloxane-modified polyaspartic acid ester.

[0017] More preferably, the raw materials of the branched epoxy phenyl siloxane include the following components: 12-17 parts of diphenylsilanediol, 0.04-0.06 parts of barium hydroxide, and 8-10 parts of γ-glycidyl ether oxypropyltrimethoxysilane by mass fraction. The raw materials of the siloxane-modified polyaspartic acid ester include the following components: 10-13 parts of branched epoxy phenyl siloxane, 3-4.5 parts of polyether amine, and 2.5-3 parts of maleic acid diethyl ester by mass fraction.

[0018] In the scheme, the isocyanate-terminated prepolymer is reacted with the siloxane-modified polyaspartic ester to build a high-density chemical cross-linking structure through urea bonds and amino-epoxy bonds. The structure has rigidity (strong polar bonds) and flexibility (siloxane segments), which can synergistically resist and relieve cyclic stress. In combination with the high-rigidity skeleton of the epoxy resin, the coating can be prevented from breaking when subjected to tensile and bending loads, thereby improving the corrosion fatigue resistance of the stainless steel chassis support.

[0019] Compared with the prior art, the beneficial effects of the present application are: In the scheme, the surface of the stainless steel chassis support is galvanized to increase the surface area of the stainless steel chassis support. Annealing treatment eliminates the residual stress generated during the processing and galvanizing of the stainless steel chassis support, optimizes the internal crystal structure of the substrate, reduces lattice defects, and improves the mechanical properties of the stainless steel chassis support itself.

[0020] In the scheme, glass flake is added to the functional coating. The flaky structure of the glass flake itself can form a physical barrier layer by layer in the coating, prolonging the penetration path of the corrosion medium to the substrate and further enhancing the corrosion resistance of the stainless steel chassis support.

[0021] However, the interface compatibility of the glass flake with the matrix of the functional coating (isocyanate prepolymer, siloxane-modified polyaspartic ester, and epoxy resin) is poor. To solve this problem, siloxane segments and imidazole-based segments are introduced into the modified glass flake composite in the scheme. The siloxane segments can enhance the compatibility of the glass flake with the coating matrix. The imidazole-based segments not only act as a curing agent for the epoxy resin (through the ring-opening reaction of the active hydrogen of the imidazole ring with the epoxy group), but also complex with the galvanized layer, thereby forming a stable three-dimensional network coating on the surface of the stainless steel chassis support, improving the interfacial adhesion between the functional coating and the stainless steel chassis support, preventing the coating from peeling off under the long-term vibration and corrosion fatigue load of the chassis support during vehicle operation, and ultimately achieving long-term stability of the stainless steel support. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] In the following specific embodiments, "parts" refers to parts by weight. It should be noted that there are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary examples include: diphenylsilanediol (CAS number 947-42-2); γ-glycidyl etheroxypropyltrimethoxysilane (CAS number 2530-83-8); polyetheramine (polyetheramine D2000); diethyl maleate (CAS number 141-05-9); 2-bromoisobutyryl bromide (CAS number 20769-85-1); hydroxypropyl-terminated polydimethylsiloxane... The CAS number for the alkane is 104780-66-7, and the product number is XK9136; the CAS number for the acid binder (triethylamine) is 121-44-8; the CAS number for vinylimidazole is 1072-63-5; the glass flakes are medium-alkali type C glass flakes, with a specification of 60~80 mesh; the CAS number for 2,2'-bipyridine is 366-18-7; the CAS number for copper bromide is 7789-45-9; the CAS number for isocyanate is 75-13-8; the epoxy resin is E51 epoxy resin; and the curing agent is 650 polyamide.

[0024] In the following examples, the preparation method of siloxane-modified polyaspartic acid ester is as follows: (1) 12 parts of diphenylsilanediol, 0.05 parts of barium hydroxide and 9 parts of γ-glycidyl etheroxypropyltrimethoxysilane are uniformly mixed and stirred under a nitrogen atmosphere to obtain branched epoxyphenylsiloxane; (2) under nitrogen protection, 10 parts of branched epoxyphenylsiloxane and 4 parts of polyetheramine are uniformly mixed and stirred at 80°C, cooled to 55°C, 2.7 parts of diethyl maleate are added dropwise, and the temperature is raised to 80°C and stirred continuously to obtain siloxane-modified polyaspartic acid ester.

[0025] Example 1: A method for preparing a high-strength, fatigue-resistant stainless steel chassis bracket for automobiles, comprising the following steps: Pre-preparation: (1) Under nitrogen protection, 9 parts of hydroxypropyl-terminated polydimethylsiloxane were added to 35 parts of toluene, and 4 parts of acid-binding agent were added; under ice-water bath, 2-bromoisobutyryl bromide-toluene solution (3 parts of 2-bromoisobutyryl bromide and 10 parts of toluene were mixed to obtain 2-bromoisobutyryl bromide-toluene solution) were added, and the mixture was stirred at room temperature for 6 hours to obtain bromopolydimethylsiloxane; (2) Add 8 parts of methacryloxy glass flakes and 3 parts of vinylimidazole to 50 parts of methanol aqueous solution (methanol accounts for 60 wt% of methanol aqueous solution), disperse evenly by ultrasonication, degas, and under nitrogen protection, add bromopolydimethylsiloxane-toluene solution (2 parts of bromopolydimethylsiloxane and 10 parts of toluene are mixed to obtain bromopolydimethylsiloxane-toluene solution), 0.5 parts of 2,2'-bipyridine and 0.12 parts of copper bromide in sequence, stir and react for 24 hours in the dark, wash and dry to obtain modified glass flake composite material; Under nitrogen protection, hydroxypropyl-terminated polydimethylsiloxane was heated to 100°C and stirred to remove water for 1 hour. The mixture was then cooled to 50°C, and diphenylmethane diisocyanate was added and stirred. 0.03 parts of catalyst (dibutyltin dilaurate) were added, and the mixture was heated to 80°C and stirred for 3 hours to obtain an isocyanate-terminated prepolymer. The mass ratio of hydroxypropyl-terminated polydimethylsiloxane to diphenylmethane diisocyanate was 1:1.4. The raw materials for the zinc plating solution include the following components: 45 g / L zinc chloride, 70 g / L potassium chloride, 12 g / L boric acid, and 30 mL / L brightener; Step 1: Mix 30 parts of isocyanate-terminated prepolymer, 15 parts of siloxane-modified polyaspartic acid ester, 8 parts of epoxy resin, 10 parts of modified glass flake composite material, 1.3 parts of curing agent (650 polyamide), and 15 parts of solvent (butyl acetate to propylene glycol methyl ether acetate in a mass ratio of 4:1) uniformly to obtain a functional coating. Step 2: (1) Pickle the stainless steel chassis bracket for 3 minutes (20wt% sulfuric acid), rinse with running water for 1 minute, and place it in a 22℃ zinc plating solution, setting the electroplating density to 20A / dm. 2 (1) Electro-galvanize for 3 minutes, clean and dry, and anneal at 130°C for 30 minutes to obtain a prefabricated stainless steel chassis support; (2) Apply functional coating to the surface of the prefabricated stainless steel chassis support, keep it at 50°C for 1.5 hours, at 80°C for 2 hours, and at 120°C for 3 hours to obtain a high-strength fatigue-resistant stainless steel chassis support.

[0026] Example 2: A method for preparing a high-strength, fatigue-resistant stainless steel chassis bracket for automobiles, comprising the following steps: Pre-preparation: (1) Under nitrogen protection, 9 parts of hydroxypropyl-terminated polydimethylsiloxane were added to 35 parts of toluene, and 4 parts of acid-binding agent were added; under ice-water bath, 2-bromoisobutyryl bromide-toluene solution (3 parts of 2-bromoisobutyryl bromide and 10 parts of toluene were mixed to obtain 2-bromoisobutyryl bromide-toluene solution) were added, and the mixture was stirred at room temperature for 6 hours to obtain bromopolydimethylsiloxane; (2) Add 8 parts of methacryloxy glass flakes and 3 parts of vinylimidazole to 50 parts of methanol aqueous solution (methanol accounts for 60 wt% of methanol aqueous solution), disperse evenly by ultrasonication, degas, and under nitrogen protection, add bromopolydimethylsiloxane-toluene solution (2 parts of bromopolydimethylsiloxane and 10 parts of toluene are mixed to obtain bromopolydimethylsiloxane-toluene solution), 0.5 parts of 2,2'-bipyridine and 0.12 parts of copper bromide in sequence, stir and react for 24 hours in the dark, wash and dry to obtain modified glass flake composite material; Under nitrogen protection, hydroxypropyl-terminated polydimethylsiloxane was heated to 100°C and stirred to remove water for 1 hour. The mixture was then cooled to 50°C, and diphenylmethane diisocyanate was added and stirred. 0.03 parts of catalyst (dibutyltin dilaurate) were added, and the mixture was heated to 80°C and stirred for 3 hours to obtain an isocyanate-terminated prepolymer. The mass ratio of hydroxypropyl-terminated polydimethylsiloxane to diphenylmethane diisocyanate was 1:1.4. The raw materials for the zinc plating solution include the following components: 45 g / L zinc chloride, 70 g / L potassium chloride, 12 g / L boric acid, and 30 mL / L brightener; Step 1: Mix 40 parts of isocyanate-terminated prepolymer, 25 parts of siloxane-modified polyaspartic acid ester, 8 parts of epoxy resin, 20 parts of modified glass flake composite material, 1.3 parts of curing agent (650 polyamide), and 20 parts of solvent (butyl acetate to propylene glycol methyl ether acetate in a mass ratio of 4:1) uniformly to obtain a functional coating. Step 2: (1) Pickle the stainless steel chassis bracket for 3 minutes (20wt% sulfuric acid), rinse with running water for 1 minute, and place it in a 22℃ zinc plating solution, setting the electroplating density to 20A / dm. 2 (1) Electro-galvanize for 3 minutes, clean and dry, and anneal at 130°C for 30 minutes to obtain a prefabricated stainless steel chassis support; (2) Apply functional coating to the surface of the prefabricated stainless steel chassis support, keep it at 50°C for 1.5 hours, at 80°C for 2 hours, and at 120°C for 3 hours to obtain a high-strength fatigue-resistant stainless steel chassis support.

[0027] Example 3: A method for preparing a high-strength, fatigue-resistant stainless steel chassis bracket for automobiles, comprising the following steps: Pre-preparation: (1) Under nitrogen protection, 9 parts of hydroxypropyl-terminated polydimethylsiloxane were added to 35 parts of toluene, and 4 parts of acid-binding agent were added; under ice-water bath, 2-bromoisobutyryl bromide-toluene solution (3 parts of 2-bromoisobutyryl bromide and 10 parts of toluene were mixed to obtain 2-bromoisobutyryl bromide-toluene solution) were added, and the mixture was stirred at room temperature for 6 hours to obtain bromopolydimethylsiloxane; (2) Add 8 parts of methacryloxy glass flakes and 3 parts of vinylimidazole to 50 parts of methanol aqueous solution (methanol accounts for 60 wt% of methanol aqueous solution), disperse evenly by ultrasonication, degas, and under nitrogen protection, add bromopolydimethylsiloxane-toluene solution (2 parts of bromopolydimethylsiloxane and 10 parts of toluene are mixed to obtain bromopolydimethylsiloxane-toluene solution), 0.5 parts of 2,2'-bipyridine and 0.12 parts of copper bromide in sequence, stir and react for 24 hours in the dark, wash and dry to obtain modified glass flake composite material; Under nitrogen protection, hydroxypropyl-terminated polydimethylsiloxane was heated to 100°C and stirred to remove water for 1 hour. The mixture was then cooled to 50°C, and diphenylmethane diisocyanate was added and stirred. 0.03 parts of catalyst (dibutyltin dilaurate) were added, and the mixture was heated to 80°C and stirred for 3 hours to obtain an isocyanate-terminated prepolymer. The mass ratio of hydroxypropyl-terminated polydimethylsiloxane to diphenylmethane diisocyanate was 1:1.4. The raw materials for the zinc plating solution include the following components: 45 g / L zinc chloride, 70 g / L potassium chloride, 12 g / L boric acid, and 30 mL / L brightener; Step 1: Mix 40 parts of isocyanate-terminated prepolymer, 25 parts of siloxane-modified polyaspartic acid ester, 8 parts of epoxy resin, 15 parts of modified glass flake composite material, 1.3 parts of curing agent (650 polyamide), and 20 parts of solvent (butyl acetate to propylene glycol methyl ether acetate in a mass ratio of 4:1) uniformly to obtain a functional coating. Step 2: (1) Pickle the stainless steel chassis bracket for 3 minutes (20wt% sulfuric acid), rinse with running water for 1 minute, and place it in a 22℃ zinc plating solution, setting the electroplating density to 20A / dm. 2 (1) Electro-galvanize for 3 minutes, clean and dry, and anneal at 130°C for 30 minutes to obtain a prefabricated stainless steel chassis support; (2) Apply functional coating to the surface of the prefabricated stainless steel chassis support, keep it at 50°C for 1.5 hours, at 80°C for 2 hours, and at 120°C for 3 hours to obtain a high-strength fatigue-resistant stainless steel chassis support.

[0028] Comparative Example 1 is based on Example 2, with glass flakes added directly; the remaining operation steps remain unchanged; Step 1: Mix 40 parts of isocyanate-terminated prepolymer, 25 parts of siloxane-modified polyaspartic acid ester, 8 parts of epoxy resin, 15 parts of glass flakes, 1.3 parts of curing agent (650 polyamide), and 20 parts of solvent (butyl acetate to propylene glycol methyl ether acetate in a mass ratio of 4:1) uniformly to obtain a functional coating. Step 2: (1) Pickle the stainless steel chassis bracket for 3 minutes (20wt% sulfuric acid), rinse with running water for 1 minute, and place it in a 22℃ zinc plating solution, setting the electroplating density to 20A / dm. 2 (1) Electro-galvanize for 3 minutes, clean and dry, and anneal at 130°C for 30 minutes to obtain a prefabricated stainless steel chassis support; (2) Apply functional coating to the surface of the prefabricated stainless steel chassis support, keep it at 50°C for 1.5 hours, at 80°C for 2 hours, and at 120°C for 3 hours to obtain a high-strength fatigue-resistant stainless steel chassis support. The raw materials for the zinc plating solution include the following components: 45g / L zinc chloride, 70g / L potassium chloride, 12g / L boric acid, and 30mL / L brightener.

[0029] Comparative Example 2 is based on Example 2, but without the introduction of vinylimidazole; the remaining operating steps remain unchanged; (1) Under nitrogen protection, 9 parts of hydroxypropyl-terminated polydimethylsiloxane were added to 10 parts of toluene, and 4 parts of acid-binding agent were added; under ice-water bath, 2-bromoisobutyryl bromide-toluene solution (3 parts of 2-bromoisobutyryl bromide and 10 parts of toluene were mixed to obtain 2-bromoisobutyryl bromide-toluene solution) were added, and the mixture was stirred at room temperature for 6 hours to obtain bromopolydimethylsiloxane; (2) Eight parts of methacryloxy glass flakes were added to a methanol aqueous solution, ultrasonically dispersed and degassed. Under nitrogen protection, bromodimethylsiloxane-toluene solution (2 parts of bromodimethylsiloxane and 10 parts of toluene were mixed to obtain bromodimethylsiloxane-toluene solution), 0.5 parts of 2,2'-bipyridine and 0.12 parts of copper bromide were added in sequence. The mixture was stirred and reacted for 24 hours in the dark, washed and dried to obtain the modified glass flake composite material.

[0030] Comparative Example 3 is based on Example 1, but without the zinc coating; the remaining operating steps remain the same. Step 1: Mix 40 parts of isocyanate-terminated prepolymer, 25 parts of siloxane-modified polyaspartic acid ester, 8 parts of epoxy resin, 20 parts of modified glass flake composite material, 1.3 parts of curing agent (650 polyamide), and 20 parts of solvent (butyl acetate to propylene glycol methyl ether acetate in a mass ratio of 4:1) uniformly to obtain a functional coating. Step 2: (1) Pickle the stainless steel chassis bracket for 3 minutes (20wt% sulfuric acid), wash with running water for 1 minute, dry, and anneal at 130℃ for 30 minutes to obtain a prefabricated stainless steel chassis bracket; (2) Apply functional coating to the surface of the prefabricated stainless steel chassis bracket, keep it at 50℃ for 1.5 hours, at 80℃ for 2 hours, and at 120℃ for 3 hours to obtain a high-strength fatigue-resistant stainless steel chassis bracket.

[0031] Comparative Example 4 is based on Example 2, but without the introduction of isocyanate-terminated prepolymer; the remaining operating steps remain unchanged; Step 1: Mix 25 parts of siloxane-modified polyaspartic acid ester, 8 parts of epoxy resin, 20 parts of modified glass flake composite material, 1.3 parts of curing agent (650 polyamide), and 20 parts of solvent (butyl acetate and propylene glycol methyl ether acetate in a mass ratio of 4:1) uniformly to obtain a functional coating. Step 2: (1) Pickle the stainless steel chassis bracket for 3 minutes (20wt% sulfuric acid), rinse with running water for 1 minute, and place it in a 22℃ zinc plating solution, setting the electroplating density to 20A / dm. 2(1) Electro-galvanize for 3 minutes, clean and dry, and anneal at 130°C for 30 minutes to obtain a prefabricated stainless steel chassis support; (2) Apply functional coating to the surface of the prefabricated stainless steel chassis support, keep it at 50°C for 1.5 hours, at 80°C for 2 hours, and at 120°C for 3 hours to obtain a high-strength fatigue-resistant stainless steel chassis support.

[0032] Performance Test 1: Corrosion fatigue testing was conducted according to ASTM E466-15 standard; the high-strength fatigue-resistant stainless steel chassis supports prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to corrosion fatigue testing using Hank's solution at a temperature of 37°C. 7 The stress ratio was 0.1, the test frequency was 20Hz, and the loading waveform was a sine wave. The Hank's solution composition included: 8.0 g / L NaCl, 0.4 g / L KCl, 0.12 g / L Na2HPO4, 0.06 g / L KH2PO4, 0.14 g / L CaCl2, 0.4 g / L MgSO4·7H2O, 0.9 g / L Glucose, and 0.35 g / L NaHCO3.

[0033] Table 1

[0034] Conclusions: Comparative Example 1, based on Example 2, directly added glass flakes; this led to a decrease in the performance of Comparative Example 1 because the polydimethylsiloxane and polyimide chains on the surface improved its compatibility with the coating, resulting in a stronger bond and more effective prevention of corrosive media penetration and crack propagation. Unmodified glass flakes, on the other hand, were prone to interfacial defects with the substrate. Comparative Example 2, based on Example 2, did not introduce vinylimide; this also led to a decrease in performance because imidazole groups can enhance the coordination bonding between the coating and the zinc plating layer, improving adhesion; and it also promotes the curing of epoxy resin, improving the overall coating performance and thus enhancing the coating's resistance to corrosion. The continuous fatigue resistance of stainless steel; Comparative Example 3 is based on Example 2, without the zinc coating; This leads to a decrease in the performance of Comparative Example 3 because the adhesion decreases under cyclic stress in the corrosion fatigue test, and the zinc coating is the basic defense that can effectively improve corrosion fatigue in conjunction with the glass flakes; Comparative Example 4 is based on Example 2, without the introduction of isocyanate-terminated prepolymer; This leads to a decrease in performance because the isocyanate-terminated prepolymer forms a polyurea / polyurethane structure with the siloxane-modified polyaspartic acid ester, giving the coating excellent elasticity, toughness and the ability to absorb shock / vibration energy, thus enhancing the performance of the stainless steel chassis support.

[0035] Performance Test 2: The yield strength and tensile strength of Example 2 were tested according to GB / T228.1-2010; Conclusion: The yield strength of Example 2 was 1356.2 MPa and the tensile strength was 1544.6 MPa. According to Table 1, it can be seen that the high-strength fatigue-resistant stainless steel chassis support prepared in Example 2 has high strength and high fatigue resistance.

[0036] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for manufacturing a high-strength fatigue-resistant stainless steel chassis support for an automobile, characterized by: The method comprises the following steps: ​ Step 1: uniformly mixing isocyanate-terminated prepolymer, siloxane-modified polyaspartic ester, epoxy resin, modified glass flake composite, curing agent and solvent to obtain a functional coating; Step 2: (1) pickling, washing, electroplating and annealing a stainless steel base support to obtain a prefabricated stainless steel base support; (2) coating the functional coating on the surface of the prefabricated stainless steel base support and curing by temperature programming to obtain a high-strength fatigue-resistant stainless steel base support.

2. The method for preparing a high-strength and fatigue-resistant stainless steel chassis support for an automobile according to claim 1, characterized in that: The raw materials of the functional coating comprise the following components: 30-40 parts of isocyanate-terminated prepolymer, 15-25 parts of siloxane-modified polyaspartic ester, 8-14 parts of epoxy resin, 10-20 parts of modified glass flake composite, 1-3 parts of curing agent and 15-20 parts of solvent.

3. The method for preparing a high-strength and fatigue-resistant stainless steel chassis support for an automobile according to claim 1, characterized in that: The process conditions of the temperature programming curing are as follows: 1-2 hours of heat preservation at 50-60 DEG C, 2-4 hours of heat preservation at 80-90 DEG C and 1-2 hours of heat preservation at 120-130 DEG C.

4. The method for preparing a high-strength and fatigue-resistant stainless steel chassis support for an automobile according to claim 1, characterized in that: In the electroplating process, the raw materials of the zinc plating solution comprise the following components: 40-60 g / L of zinc chloride, 70-90 g / L of potassium chloride, 10-15 g / L of boric acid and 30-50 mL / L of brightener. The electroplating process parameters are: temperature 20-25°C, electroplating density 20-30 A / dm 2 , time 2-4 minutes; The process conditions of the annealing are as follows: an annealing temperature of 120-150 DEG C and an annealing time of 30-60 minutes.

5. The method of claim 1, wherein the high-strength fatigue-resistant stainless steel chassis bracket for an automobile is prepared by the steps of: The preparation method of the modified glass flake composite is as follows: ​ (1) under nitrogen protection, adding hydroxypropyl-terminated polydimethylsiloxane into toluene and adding an acid binding agent; under ice water bath, adding 2-bromoisobutyryl bromide-toluene solution and stirring at room temperature for 6-8 hours to obtain bromo-polydimethylsiloxane; (2) adding methacryloxy glass flake and vinyl imidazole into methanol aqueous solution, uniformly dispersing and degassing, adding bromo-polydimethylsiloxane-toluene solution, 2,2'-dipyridyl and copper bromide in sequence under nitrogen protection, stirring for 20-25 hours in dark, and washing and drying to obtain the modified glass flake composite.

6. The method of claim 5, wherein the high-strength fatigue-resistant stainless steel chassis bracket for an automobile is prepared by the steps of: The raw materials of the bromo-polydimethylsiloxane comprise the following components: 8-10 parts of hydroxypropyl-terminated polydimethylsiloxane, 2-4 parts of 2-bromoisobutyryl bromide and 3-4 parts of acid binding agent. ​ The raw materials of the modified glass flake composite comprise the following components: 7-10 parts of methacryloxy glass flake, 2-4 parts of vinyl imidazole, 1-2 parts of bromo-polydimethylsiloxane, 0.5-0.7 parts of 2,2'-dipyridyl and 0.1-0.15 parts of copper bromide.

7. The method of claim 1, wherein the high-strength fatigue-resistant stainless steel chassis bracket for an automobile is prepared by the steps of: The preparation method of the isocyanate-terminated prepolymer is as follows: under nitrogen protection, mixing hydroxypropyl-terminated polydimethylsiloxane with diphenylmethane diisocyanate after water removal, adding a catalyst, stirring at 40-50 DEG C for 1-2 hours, and stirring at 80-90 DEG C for 2-4 hours to obtain the isocyanate-terminated prepolymer. ​ The mass ratio of hydroxypropyl-terminated polydimethylsiloxane to diphenylmethane diisocyanate is 1:1.2-1.

4.

8. The method of claim 1, wherein the high-strength fatigue-resistant stainless steel chassis bracket for an automobile is prepared by the steps of: The preparation method of the siloxane modified polyaspartic ester comprises the following steps: (1) uniformly mixing diphenylsilanediol, barium hydroxide and gamma-glycidoxypropyltrimethoxysilane, stirring and reacting under a nitrogen atmosphere to obtain branched epoxy phenylsiloxane; (2) uniformly mixing the branched epoxy phenylsiloxane and polyether amine under nitrogen protection, stirring at 80-90 DEG C for 8-10 hours, cooling to 50-60 DEG C, adding dropwise diethyl maleate, and continuing to stir at 80-90 DEG C to obtain the siloxane modified polyaspartic ester. ​ 9. The method of claim 8, wherein the high-strength fatigue-resistant stainless steel chassis bracket for an automobile is prepared by the steps of: The raw materials of the branched epoxy phenylsiloxane comprise the following components: 12-17 parts of diphenylsilanediol, 0.04-0.06 parts of barium hydroxide and 8-10 parts of gamma-glycidoxypropyltrimethoxysilane by mass fraction; ​ The raw materials of the siloxane modified polyaspartic ester comprise the following components: 10-13 parts of branched epoxy phenylsiloxane, 3-4.5 parts of polyether amine and 2.5-3 parts of diethyl maleate by mass fraction.

10. A high-strength fatigue-resistant stainless steel chassis support for a vehicle is prepared by the method according to any one of claims 1-9.

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