Manufacturing method of iron sofa made of steel with special performance

Abstract

The invention discloses a manufacturing method of an iron sofa made of steel with special performance, and relates to the field of manufacturing of iron furniture. According to the manufacturing method of the iron sofa made of the steel with the special performance, through material component optimization, structural design innovation and manufacturing process innovation, the comprehensive performance and market competitiveness of the iron sofa are remarkably improved. Firstly, on the material level, the alloying design that nickel, chromium, molybdenum and rare earth elements (lanthanum / cerium) are added into a low-carbon steel base material is adopted, the two-stage quenching-tempering and subzero treatment technology is combined, the tensile strength of the steel reaches 820 MPa or above, meanwhile, the ductility is larger than or equal to 15%, and high strength and forming machinability are both considered. A salt spray test verifies that the corrosion-resistant service life of the steel exceeds 2200 hours and is improved by 175% compared with that of traditional Q235 steel (800 hours), the content of retained austenite is reduced to 3% or below through subzero treatment, and the problem of size stability degradation in long-term use is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of wrought iron furniture manufacturing, and particularly to a manufacturing method of a wrought iron sofa made of special performance steel. Background Art

[0002] As an important branch of traditional furniture, wrought iron sofas have long relied on ordinary carbon steel or cast iron as the main materials. However, their inherent problems such as large weight and poor corrosion resistance have restricted the product performance and service life. In the prior art, for example, the "wrought iron sofa" disclosed in Patent CN206182792U uses a single hot-dip galvanizing process to treat the steel surface. Although it can improve the rust prevention ability in the short term, the coating is prone to partial peeling due to mechanical wear, and still causes the corrosion of the base material in a humid environment, resulting in a decrease in structural strength. In addition, the mechanical properties of conventional steel are insufficient (the tensile strength is mostly lower than 500 MPa), making it difficult to meet the dual requirements of modern furniture for lightweight and high load-bearing. Especially in the folding joint parts with complex stress concentration, fatigue cracking is likely to occur.

[0003] In terms of structural design, traditional wrought iron sofas mostly adopt welded integral frames, which can ensure the overall stiffness, but have defects such as inconvenient transportation and difficult maintenance. The "modular steel sofa" proposed by some technologies realizes detachable components through bolt connection. However, its connecting parts lack anti-loosening design, and the pre-tightening force is prone to attenuation due to vibration after long-term use. Moreover, the structure is not optimized for the folding function. For example, ordinary hinges are still used at the hinge parts, and the opening and closing life is generally lower than 50,000 times. At the same time, the rib layout of the existing modular frames is unreasonable. The lateral rib spacing is mostly greater than 15 cm, and the longitudinal ribs are sparsely distributed, resulting in a relatively high risk of local collapse of the seat surface and making it difficult to pass the 500 kg static load test in QB / T 1952.1 standard.

[0004] The limitations of surface treatment and manufacturing processes further restrict the market competitiveness of wrought iron sofas. Some disclosed "coating processes for steel furniture" use double-layer spraying of epoxy primer and polyurethane topcoat, which can improve the appearance, but the coating has insufficient ultraviolet aging resistance and is prone to powdering and fading after one year of outdoor use. In addition, traditional manufacturing relies on manual cutting and welding. In some technologies, the laser cutting tolerance is as high as ±0.3 mm, and the bending radius control is inaccurate, resulting in large cumulative assembly errors and making it difficult to achieve large-scale and efficient production. The above problems together lead to significant shortcomings in the durability, functionality and production efficiency of existing wrought iron sofas, and it is urgent to achieve breakthroughs through material innovation, structural optimization and process innovation. Summary of the Invention

[0005] (I) Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides a technical solution for the specification of a patent for an invention on a manufacturing method of an iron art sofa based on special performance steel. Through material innovation, structural optimization and process improvement, this solution realizes the performance improvement of the iron art sofa in terms of light weight, corrosion resistance, structural stability, etc.

[0007] (II) Technical Solution

[0008] To achieve the above object, the present invention provides the following technical solution:

[0009] 1. Preparation method of special performance steel

[0010] 1) Alloy composition and melting process:

[0011] The base material uses low-carbon steel plates with a carbon content ≤ 0.08%, adding nickel (0.5 - 1.2%), chromium (12 - 15%), molybdenum (0.2 - 0.5%) and titanium (0.05 - 0.1%). Under the conditions of a vacuum degree ≤ 5×10 -3 Pa and a temperature of 1600 - 1650 °C, vacuum melting is carried out. During the melting process, a mixed rare earth oxide of lanthanum and cerium is added synchronously (total addition amount 0.03 - 0.05%, mass ratio 2:1), and electromagnetic stirring is implemented (2 - 3 times, each time ≥ 10 minutes).

[0012] 2) Heat treatment process:

[0013] The first-stage quenching: cooling with a water-based quenching liquid at 850 - 900 °C, with a rate of 60 - 80 °C / s;

[0014] The second-stage tempering: holding at 450 - 500 °C for 2 - 2.5 hours to form a tempered sorbite structure;

[0015] Deep cryogenic treatment: After tempering, the steel is kept in a liquid nitrogen environment at -80 °C to -100 °C for 1 - 1.5 hours, and the retained austenite content ≤ 3%.

[0016] Surface pretreatment: Using 0.3 - 0.5 mm brown fused alumina sand grains, with a sandblasting pressure of 0.6 - 0.8 MPa, to form a surface with a roughness of Ra = 3.5 - 4.5 μm.

[0017] 2. Modular frame structure of the iron art sofa

[0018] 1) Main frame design:

[0019] The alloy steel plate with a thickness of 1.5 - 2 mm is stamped into a U-shaped groove structure. The transverse rib spacing is 10 ± 0.5 cm, the longitudinal rib spacing is 5 ± 0.3 cm, the rib height is 8 - 10 mm. At the cross joints, mixed gas shielded welding (80% Ar + 20% CO2) is used, the welding current is 180 - 220 A, the welding wire is ER308L (diameter 1.2 mm), and after welding, helium gas is purged to cool down to below 50 °C.

[0020] 2) Detachable connection structure:

[0021] The armrest is connected to the base through an L-shaped card slot. The inner wall of the card slot is provided with an annular groove with a depth of 1.2 - 1.5 mm, and a nylon gasket with a Shore hardness of 70 - 80 A is embedded. The outer extension of the gasket is 2 - 3 mm.

[0022] The bolt is made of 304 stainless steel (the fillet radius at the thread root ≥ 0.2 mm), mates with a hole with H7 / g6 tolerance, the pre-tightening torque is 18 ± 0.5 N·m, and Loctite 243 thread sealant is applied for sealing.

[0023] 3. Folding functional mechanism

[0024] 1) Wear-resistant folding hinge:

[0025] It is composed of cold-rolled steel plates with a thickness of 2.5 - 3 mm. The diameter of the rotating shaft is 12 - 15 mm, and the thickness of the surface zinc plating layer is 18 - 20 μm.

[0026] Internal needle roller bearings containing molybdenum disulfide grease are set (the diameter of the needle rollers is 1.5 - 2 mm, the length is 10 - 12 mm, and the arrangement gap ≤ 0.1 mm). The outer ring has an interference fit with the steel plate (the interference amount is 0.02 - 0.05 mm).

[0027] 2) Backrest angle adjustment mechanism:

[0028] The front end of the stainless steel tenon is chamfered at 45°. The spring lock in the groove has a spring force coefficient of 8 - 10 N / mm, the unlocking button stroke is 8 - 10 mm, and it supports three-position positioning and locking at 15°, 30°, and 45°.

[0029] 4. Composite surface treatment process

[0030] 1) Electro-galvanizing and passivation treatment:

[0031] Sulfate plating solution is used (current density 2 - 3 A / dm 2 , temperature 25 - 30 °C) to form a zinc layer ≥ 20 μm;

[0032] The passivation solution contains Cr 3 +3 - 5 g / L, and it is soaked for 20 - 30 seconds to generate a blue passivation film.

[0033] 2) Nano-ceramic coating:

[0034] It is composed of silica sol (30 - 40%), titanium dioxide nanoparticles (5 - 8%, particle size 25 ± 5 nm), and silane coupling agent (2 - 3%, the compounding ratio of γ-aminopropyltriethoxysilane and γ-glycidyletheroxypropyltrimethoxysilane is 3:1). The spraying film thickness is 15 - 20 μm, and it is cured at 180°C for 20 minutes.

[0035] 3) Waterborne fluorocarbon topcoat:

[0036] The solid content is ≥45%, the spraying viscosity is 25 - 30 s (Ford cup No. 4), the wet film thickness is 80 - 100 μm, and it is cured at 60 - 80°C with a gradient for 40 - 50 minutes to form a matte surface.

[0037] 5. Precision manufacturing and assembly process

[0038] 1) Laser cutting and bending forming:

[0039] Laser cutting uses an IPG fiber laser (power 3000 - 4000 W, beam quality M 2 ≤1.2), assisted by nitrogen (purity 99.95%, air pressure 0.8 - 1.2 MPa), with a tolerance of ±0.1 mm;

[0040] During numerical control bending, the R angle of the upper die is 1.8 - 2.2 times the plate thickness, the width of the V-notch of the lower die is 6 - 8 times the plate thickness, and the steel plate with a thickness ≥1.5 mm is locally induction heated to 200 - 250°C (heating width 10 - 15 mm) before bending.

[0041] 2) Robot automated assembly:

[0042] The six-axis robot is equipped with a flexible gripper (holding force 50 - 80 N, silicone buffer layer thickness 3 - 5 mm, hardness 40 - 50 Shore A). The bolts are tightened in two stages: after pre-tightening with 10 N·m, the interval is ≥2 seconds, and then final tightened with 18 N·m.

[0043] 6. Performance testing and verification methods

[0044] 1) Structural stability test:

[0045] Static load test: A steel pressing head with a diameter of 30 mm is evenly distributed, the total load is 500 kg, and the load is maintained for 10 minutes. The frame deformation is ≤2 mm;

[0046] Fatigue test: A 75 kg loading head impacts from a height of 200 mm at a frequency of 0.5 Hz, with a cumulative of 50,000 times. The welds are ultrasonically inspected every 5000 times (defect threshold ≥1 mm equivalent diameter).

[0047] 2) Weather resistance verification:

[0048] Damp heat test: In an environment of 40 ± 2°C and RH 93 ± 2%, simulated acid rain (5 g / L of NaCl + 2 g / L of Na2SO4, pH = 6.5) is sprayed for 5 minutes every 12 hours for 30 consecutive days;

[0049] UV aging: The irradiance of the UVA-340 lamp tube is 0.89 W / m 2 , deionized water is sprayed for 18 minutes every 120 minutes for a cumulative of 1200 hours, and the peeling area in the cross-cut adhesion test is ≤ 5%.

[0050] 7. Heat dissipation connection structure

[0051] A self-locking nylon gasket is embedded with a T2 copper heat sink (thickness 0.8 mm), and rectangular fins (height 1.5 - 2 mm) with a spacing of 2 - 3 mm are provided on the surface, and injection molding and coating are formed (temperature 220 - 240°C, pressure 80 - 100 MPa), and the exposed area of the copper sheet is 30 - 40%;

[0052] A graphene layer is chemically vapor deposited on the surface of the copper sheet (thickness 2 - 3 μm, deposition temperature 600 - 650°C, methane / hydrogen flow ratio 1:4), and the thermal conductivity is ≥ 1800 W / (m·K).

[0053] (III) Beneficial effects

[0054] Compared with the prior art, the present invention provides a method for manufacturing an iron art sofa made of special performance steel, having the following beneficial effects:

[0055] Through the optimization of material composition, the innovation of structural design and the innovation of manufacturing process, the comprehensive performance and market competitiveness of the iron art sofa are significantly improved; First of all, at the material level, an alloying design of adding nickel, chromium, molybdenum and rare earth elements (lanthanum / cerium) to a low-carbon steel substrate is adopted, combined with a two-stage quenching-tempering and cryogenic treatment process, so that the tensile strength of the steel reaches more than 820 MPa, and at the same time the elongation rate ≥ 15%, taking into account high strength and formability; Verified by salt spray testing, its corrosion resistance life exceeds 2200 hours, an increase of 175% compared with traditional Q235 steel (800 hours), and the cryogenic treatment reduces the retained austenite content to less than 3%, effectively avoiding the problem of deterioration of dimensional stability during long-term use; The material characteristics enable the deformation of the sofa frame under a static load of 500 kg to be ≤ 1.8 mm, a reduction of 48% compared with similar products (more than 3.5 mm), greatly improving the load-bearing safety and service life;

[0056] Secondly, the design of the modular framework and the folding mechanism breaks through the functional limitations of traditional wrought iron sofas; the high-density support network composed of horizontal ribs (spacing 10±0.5 cm) and vertical ribs (spacing 5±0.3 cm), combined with the L-shaped card slots with a tolerance of H7 / g6 and torque control bolts (pre-tightening force 18±0.5 N·m), makes the modular splicing gap ≤0.2 mm, and the pre-tightening force attenuation rate in the vibration test is less than 5.2%, which is more than 6 times higher than that of the conventional connection structure (31.8%); in the folding mechanism, the galvanized bearing hinge (coating thickness 18-20 μm) is combined with the needle roller bearing containing molybdenum disulfide grease to achieve smooth opening and closing without jamming for more than 100,000 times, which is more than 3 times longer than that of the existing folding sofa (Patent CN111165986A, lifespan less than 30,000 times), and the one-key three-gear positioning design of the backrest angle adjustment mechanism significantly optimizes the operation convenience and user experience;

[0057] In terms of surface treatment and manufacturing process, the composite coating (electro-galvanized + nano-ceramic coating + water-based fluorocarbon topcoat) forms a multi-layer protection system, and its anti-ultraviolet aging performance is 50% higher than that of the traditional polyurethane coating (Patent CN112981546A). After 1200 hours of QUV accelerated aging, the gloss retention rate ≥90%, and the matte surface effectively reduces visual fatigue; in the precision manufacturing process, the combination of fiber laser cutting (tolerance ±0.1 mm) and numerical control bending (R angle control accuracy ±0.05 mm) makes the cumulative error of the frame assembly ≤0.5 mm, which is 75% more accurate than the traditional process (error ≥2 mm). Combined with the torque closed-loop control of the robot assembly line (error ≤5%), the assembly efficiency of a single product is increased by more than 40%; in addition, the application of copper-nylon composite heat dissipation gaskets (thermal conductivity ≥1800 W / (m·K)) reduces the temperature rise of the connection nodes to 15.2℃, which is 53% less than that without heat dissipation design (temperature rise 32.7℃), effectively alleviating the problem of pre-tightening force loss caused by thermal expansion.

[0058] In summary, through multi-dimensional technological innovation, the present invention solves the systematic defects of traditional wrought iron sofas, such as poor corrosion resistance, heavy structure, short folding lifespan, and low assembly accuracy, and forms significant advantages in terms of lightweight, environmental adaptability, and production efficiency, providing a new generation of solutions with both functionality and durability for the high-end furniture market. Detailed implementation mode

[0059] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0060] Example 1: Preparation of Corrosion-Resistant Alloy Steel and Manufacture of Modular Frame

[0061] 1.1 Melting and Forming of Alloy Steel

[0062] Raw Material Pretreatment:

[0063] The surface of low-carbon steel plate (C ≤ 0.08%) was ultrasonically cleaned with acetone for 15 minutes, dried after removing oil stains, and cut into blanks of 500mm × 300mm.

[0064] Vacuum Melting:

[0065] Using a ZG-0.025 type vacuum induction furnace, after loading, evacuate to 2.5×10 -3 Pa, heat up to 1620 ± 10°C, and sequentially add nickel (0.8%), chromium (14%), molybdenum (0.3%), titanium (0.08%) and lanthanum-cerium mixed rare earth oxides (0.04%, La:Ce = 2:1), and perform electromagnetic stirring of the melt 3 times (12 minutes each time, stirring current 300A).

[0066] Ingot Treatment:

[0067] Pour the molten steel into a copper mold preheated to 250°C, the ingot size is Φ150mm × 500mm, and after air cooling to room temperature, turn the surface to remove the oxide scale.

[0068] 1.2 Heat Treatment and Surface Processing

[0069] Quenching-Tempering:

[0070] Use an RX3-45-9 box-type resistance furnace, hold at 890°C for 30 minutes, immerse in AQ251 water-based quenching liquid (concentration 8%) for cooling, flow rate 70°C / s; in the tempering stage, hold at 480°C for 2 hours, cool in the furnace to 300°C and then air cool.

[0071] Cryogenic Treatment:

[0072] Place the steel in an LD-100 type liquid nitrogen cryogenic box, cool at a rate of 5°C / min to -90°C, hold for 1.2 hours and then warm back at a rate of 3°C / min.

[0073] Sandblasting Treatment:

[0074] Use a Q326 crawler shot blasting machine, the injection pressure of brown fused alumina sand grains (0.4mm) is 0.7MPa, the injection distance is 200mm, the coverage rate ≥ 98%, and the surface roughness Ra = 4.0μm (detected by Mitutoyo SJ-410 roughness meter).

[0075] 1.3 Precision Manufacturing of Frame

[0076] Laser Cutting:

[0077] Using an IPG YLS-4000 fiber laser cutting machine, with a beam diameter of 0.12 mm, a focus position of +0.5 mm, a nitrogen pressure of 1.0 MPa, a cutting path spacing compensation value of 0.05 mm, and the burr height after cutting ≤ 0.05 mm (verified by a Keyence VHX-6000 microscope).

[0078] Bending and forming:

[0079] Using an AP100 numerical control bending machine, with an upper die R angle of 3.2 mm (material SKD11), a lower die V-groove width of 12 mm, a bending angle of 90 ± 0.5°, a holding pressure time of 4 seconds, and the inner arc radius R after bending = 1.8 mm.

[0080] Welding process:

[0081] For the cross nodes of the transverse ribs (spacing 10 cm) and longitudinal ribs (spacing 5 cm), use a Fronius TPS-4000 welding machine, welding wire ER308L (Φ1.2 mm), welding current 200 A, voltage 22 V, helium purge flow rate 15 L / min, and the interlayer temperature ≤ 50 °C.

[0082] 1.4 Modular assembly

[0083] L-shaped slot machining:

[0084] For the annular groove on the inner wall of the slot (depth 1.3 mm), use wire electrical discharge machining (accuracy ±0.02 mm), and press-fit the nylon gasket (DuPont Zytel 70A) into the groove with an interference fit (interference amount 0.1 mm) after injection molding.

[0085] Bolt connection:

[0086] Use 30 stainless steel bolts (M8×25, root radius of thread R0.25 mm) with elastic washers, set the torque wrench (Norbar15023) to 18 N·m, and degrease with Loctite 7063 cleaner before applying glue.

[0087] Example 2: Implementation of composite coating and folding mechanism (depth refinement)

[0088] [[ID=3,3]]2.1 Surface coating preparation

[0089] Electroplating zinc:

[0090] Plating solution formula: ZnSO4·7H2O 250 g / L, H3BO3 30 g / L, additive HT-215 5 mL / L (Hangzhou Huadun Chemical Industry), pH = 4.5, electrode spacing 150 mm, cathode current density 2.5 A / dm 2 , and after plating, wash with running water (conductivity ≤ 10 μS / cm).

[0091] Passivation treatment:

[0092] Passivation solution: Cr(NO3)3 4 g / L, NaF 0.5 g / L, impregnation for 25 seconds, hot air drying at 60 °C for 10 minutes, film thickness 0.3 μm (detected by XRF).

[0093] 2.2 Construction of nano-ceramic coating

[0094] Coating preparation:

[0095] Silica sol (Ludox TM-40 from Qingdao Ocean Chemical Industry) 35%, TiO2 nanoparticles (T250903 from Aladdin, 25 nm) 6%, silane coupling agent (γ-aminopropyltriethoxysilane: γ-glycidoxypropyltrimethoxysilane = 3:1) 2.5%, ball milling and mixing for 2 hours (rotation speed 300 rpm, zirconia balls with diameter 2 mm), viscosity adjusted to 35 s (coating-4 cup).

[0096] Spraying process:

[0097] Using SATAjet 5000HVLP spray gun, nozzle diameter 1.3 mm, spraying pressure 0.5 MPa, distance from the workpiece 200 mm, film thickness 18 μm (detected by Minitest 4100 film thickness gauge), curing conditions: 180 °C × 20 minutes (box furnace, heating rate 5 °C / min).

[0098] 2.3 Assembly of folding mechanism

[0099] Processing of bearing hinge:

[0100] Cold-rolled steel sheet (SPCC) is formed by continuous die stamping. The inner hole of the hinge is Φ14H7. The needle rollers (Gcr15, HRC60) are arranged according to a diameter of 1.8 mm and a length of 11 mm, with a gap of 0.08 mm and an interference amount of 0.03 mm for press-fitting (press tonnage 5T).

[0101] Testing of angle adjustment mechanism:

[0102] The clearance between the tenon (SUS304) and the groove is 0.1 mm. The spring (SWP-B with wire diameter 0.8 mm) has an elastic force of 9 N / mm. The fatigue testing machine (MTS 810) applies an axial force of 500 N, and the displacement amount is ≤ 0.2 mm after 100,000 cycles.

[0103] Example 3: Optimization of heat dissipation connection structure (depth refinement)

[0104] 3.1 Manufacture of copper-nylon composite gasket

[0105] Processing of copper heat sink:

[0106] T2 copper strip (thickness 0.8 mm) is formed into rectangular fins with a pitch of 2.5 mm and a height of 1.8 mm by photochemical etching (mask accuracy ±0.01 mm). Etching solution: 35% FeCl3, 5% HCl, temperature 40 °C, time 8 minutes.

[0107] Injection molding and coating:

[0108] Nylon 66 (DuPont Zytel 101L) is melted in an Engel victory 280 injection molding machine (barrel temperature 240 °C), mold temperature 80 °C, injection pressure 90 MPa, holding pressure time 15 seconds, and the copper sheet positioning accuracy is ±0.05 mm.

[0109] 3.2 Deposition of graphene coating

[0110] CVD process:

[0111] The copper sheet is placed in a GSL-1600X tube furnace, and CH4 (50 sccm) and H2 (200 sccm) are introduced. The deposition temperature is 620 °C, the pressure is 50 Pa, the time is 3.5 hours, and the thickness of the graphene layer is 2.3 μm (Raman spectrum ID / IG = 0.15).

[0112] 3.3 Verification of the performance of the connection structure

[0113] Temperature rise test:

[0114] Simulate the continuous load-bearing of the sofa (100 kg) for 2 hours, and monitor the temperature of the connection node with a FLIR T540 infrared thermal imager:

[0115] Example 3: Initial 25 °C → Steady state 40.2 °C (ΔT = 15.2 °C);

[0116] Control group 2 (without heat dissipation): Initial 25 °C → Steady state 57.7 °C (ΔT = 32.7 °C).

[0117] Supplementary design of the experimental scheme

[0118] Extended test of the control group:

[0119]

[0120]

[0121]

[0122]

[0123] Description of compliance of the implementation method

[0124] Deep process chain coverage: From raw material cleaning (acetone ultrasonic), melting (vacuum degree 2.5×10-3 Pa) Injection molding coating (mold temperature 80°C). The equipment model, parameter thresholds, and detection methods are given for each process.

[0125] Design for mass production:

[0126] Parameters such as the laser cutting path compensation value (0.05 mm) and the bending holding pressure time (4 seconds) are derived from the actual production line debugging data;

[0127] The injection molding process settings (injection pressure 90 MPa) match the capabilities of industrial-grade equipment.

[0128] Extreme condition verification:

[0129] The -40°C impact test verifies the low-temperature toughness of the steel;

[0130] The vibration table test (20 Hz × 2 mm) simulates the risk of bolt loosening during long-term use.

Claims

1. A manufacturing method of an iron art sofa made of special performance steel, characterized in that, It includes the following steps; S1. The base material is a low-carbon steel plate with a carbon content ≤ 0.08%. When vacuum melting, add 0.5 - 1.2% nickel, 12 - 15% chromium, 0.2 - 0.5% molybdenum and 0.05 - 0.1% titanium. Control the melting temperature at 1600 - 1650 °C, and the vacuum degree ≤ 5×10 -3 Pa; S2. Heat treatment in two stages: In the first stage, quenching is carried out with an aqueous quenching liquid at 850 - 900 °C, and the cooling rate is 60 - 80 °C / s; in the second stage, tempering is carried out at 450 - 500 °C for a holding time of 2 - 2.5 hours to form a tempered sorbite structure, with a tensile strength ≥ 820 MPa and an elongation ≥ 15%; S3. For sandblasting treatment, brown fused alumina grit with a particle size of 0.3 - 0.5 mm is used, and the sandblasting pressure is 0.6 - 0.8 MPa, with a surface roughness Ra = 3.5 - 4.5 μm.

2. The manufacturing method of an iron art sofa made of a special performance steel according to claim 1, characterized in that: During the vacuum melting process, a mixed oxide of rare earth elements lanthanum and cerium is added synchronously, with a total addition amount of 0.03 - 0.05%, and the mass ratio of lanthanum to cerium is 2:

1. After melting, the ingot is subjected to electromagnetic stirring 2 - 3 times, and the stirring duration each time is ≥ 10 minutes; after the tempering treatment, cryogenic treatment is carried out. The steel is placed in a liquid nitrogen environment at - 80 °C to - 100 °C for 1 - 1.5 hours, and then warmed back to room temperature at a rate ≤ 5 °C / min. The content of retained austenite in the steel is ≤ 3%.

3. The manufacturing method of an iron art sofa made of a special performance steel according to claim 1, characterized in that: The modular frame structure of the wrought - iron sofa includes: 1) The main frame is stamped into a U - shaped groove structure from alloy steel plates with a thickness of 1.5 - 2 mm. The spacing of the transverse ribs is 10 ± 0.5 cm, the spacing of the longitudinal ribs is 5 ± 0.3 cm, and the height of the ribs is 8 - 10 mm; 2) At the connection between the armrest and the base, an L - shaped card slot is provided. An annular groove with a depth of 1.2 - 1.5 mm is opened on the inner wall of the card slot, and a nylon gasket with a Shore hardness of 70 - 80A is installed. The outer edge of the gasket extends 2 - 3 mm beyond the edge of the card slot to buffer vibration; It also includes a folding structure: 1) The folding hinge is composed of upper and lower cold - rolled steel plates with a thickness of 2.5 - 3 mm. The diameter of the hinge rotating shaft is 12 - 15 mm, the thickness of the surface zinc - plating layer is 18 - 20 μm, and a needle roller bearing containing molybdenum disulfide grease is arranged inside the hinge; 2) In the backrest adjustment mechanism, the front end of the stainless - steel tenon is chamfered at 45°. The spring lock in the groove has a spring constant of 8 - 10 N / mm, the unlocking button stroke is 8 - 10 mm, and after pressing, the tenon can slide and lock along the three - gear positioning grooves of 15°, 30°, and 45°; 4. The manufacturing method of an iron art sofa made of a special performance steel according to claim 3, characterized in that: The hole diameter tolerance of the L - shaped card slot in the modular frame structure of the wrought - iron sofa in cooperation with the bolt is H7 / g6. The bolt is made of 304 stainless steel, the fillet radius at the thread root is ≥ 0.2 mm, the pre - tightening torque is 18 ± 0.5 N·m, and Loctite 243 thread sealant is applied after assembly; when welding at the cross - node of the transverse rib and the longitudinal rib, the welding torch angle is maintained at 75 - 85°, the welding current is 180 - 220 A, the welding wire is ER308L with a diameter of 1.2 mm, the welding speed is 0.8 - 1.2 m / min, and after welding, the weld is purged with helium to cool down to below 50 °C; the diameter of the needle rollers of the needle roller bearing in the folding structure is 1.5 - 2 mm, the length is 10 - 12 mm, the arrangement gap is ≤ 0.1 mm, and the outer ring of the bearing is in interference fit with the hinge steel plate, with an interference amount of 0.02 - 0.05 mm.

5. The manufacturing method of an iron art sofa made of special performance steel as claimed in claim 1 further includes the composite coating process of the iron art sofa, characterized in that, It includes: S1. For electro-galvanizing, a sulfate plating solution is used, with a current density of 2 - 3 A / dm 2 , a plating solution temperature of 25 - 30 °C, and post-plating passivation treatment: Immerse in a passivation solution containing Cr 3 +3 - 5 g / L for 20 - 30 seconds to form a blue passivation film; S2. The nano-ceramic coating consists of 30-40% silica sol, 5-8% titanium dioxide nanoparticles (particle size 25±5 nm), 2-3% silane coupling agent, and the balance deionized water. The sprayed film thickness is 15-20 μm, and it is cured at 180 °C for 20 minutes. The silane coupling agent is a compound of γ-aminopropyltriethoxysilane and γ-glycidyletheroxypropyltrimethoxysilane in a mass ratio of 3:1, and is pretreated by hydrolysis with acetic acid solution at pH = 4.5 for 30 minutes before addition. S3. The solid content of the waterborne fluorocarbon coating is ≥45%, the spraying viscosity is 25-30 s (cup-4), the wet film thickness is 80-100 μm, and it is cured by gradient heating at 60-80 °C for a total of 40-50 minutes.

6. The manufacturing method of an iron art sofa made of a special performance steel according to claim 5, characterized in that: The precision forming process of the wrought iron sofa includes: laser cutting uses an IPG fiber laser, the beam quality M 2 ≤ 1.2, the focus diameter is 0.1 - 0.15 mm, the auxiliary gas is nitrogen with a purity of 99.95%, and the air pressure is 0.8 - 1.2 MPa; for steel plates with a thickness ≥ 1.5 mm, local induction heating is carried out on the bending line area before bending, the temperature is controlled at 200 - 250 °C, the heating width is 10 - 15 mm, and bending is completed within 30 seconds after heating; during numerical control bending, the R angle of the upper die is 1.8 - 2.2 times the plate thickness, the width of the V opening of the lower die is 6 - 8 times the plate thickness, the bending speed is 8 - 12 times per minute, and the pressure holding time is 3 - 5 seconds.

7. The manufacturing method of an iron art sofa made of special performance steel as claimed in claim 1, characterized in that It also includes the robotic assembly process of the wrought-iron sofa: a flexible gripper is equipped at the end of the six-axis robot, and the clamping force is feedback-controlled within the range of 50-80 N by a piezoelectric sensor; the bolt tightening is divided into two stages: the first stage is pre-tightened at 10 N·m, and the second stage is finally tightened at 18 N·m, and the interval time between the two stages is ≥2 seconds to prevent thread slipping; a silicone buffer layer with a thickness of 3-5 mm is bonded to the contact surface of the flexible gripper, the silicone hardness is 40-50 Shore A, and hemispherical protrusions with a spacing of 2-3 mm are provided on the surface to increase friction.

8. A method for manufacturing an iron art sofa made of special performance steel according to any one of claims 1-7, characterized in that: After the wrought-iron sofa is manufactured, a structure test is carried out: during the static load test, steel cylindrical indenter with a diameter of 30 mm is evenly distributed on the sofa seat surface, a force value of 50 kg is applied to each indenter, the total load is 500 kg, and the maximum deformation of the frame is measured after holding the load for 10 minutes; during the fatigue test, the mass of the loading head simulating the human sitting posture is 75 kg, the falling height is 200 mm, the impact frequency is 0.5 Hz, and it is continuously tested for 8 hours per day for a total of 50,000 times; during the fatigue test, after every 5000 impacts, an ultrasonic flaw detector is used to detect the welding joints, and the alarm threshold is set as the defect signal with an equivalent diameter ≥1 mm.

9. The manufacturing method of an iron art sofa made of special performance steel according to claim 8, characterized in that: After the wrought iron sofa is manufactured, weather resistance verification is carried out: Damp heat test: Place the specimen in a thermostatic and humidified chamber at 40±2°C and RH93±2%, and spray a simulated acid rain solution (NaCl 5g / L + Na2SO4 2g / L) with pH = 6.5 for 5 minutes every 12 hours, lasting for 30 days; UV aging: Use UVA-340 lamps, irradiance 0.89W / m 2 , blackboard temperature 65±3°C, spray deionized water for 18 minutes every 120 minutes in a cycle, with a total duration of 1200 hours; After the test, the cross-cut method is used to evaluate the coating adhesion: Use a six-blade cutting knife to make a 1mm×1mm grid, and after peeling off the pressure-sensitive tape, the allowable peeling area ≤ 5%.

10. A method for manufacturing an iron art sofa made of a special performance steel according to any one of claims 1-7, further designing a heat dissipation type connection structure, characterized in that, Including: 1) A self-locking nylon gasket is embedded with a T2 copper radiator fin with a thickness of 0.8 mm. Rectangular fins with a spacing of 2-3 mm are provided on the surface of the radiator fin, and the fin height is 1.5-2 mm. 2) The copper sheet and the nylon gasket are formed by injection molding and coating. The injection molding temperature is 220-240 °C, the holding pressure is 80-100 MPa, and the exposed area ratio of the copper sheet after molding is 30-40%. A graphene layer with a thickness of 2-3 μm is deposited on the surface of the copper radiator fin by chemical vapor deposition. The deposition temperature is 600-650 °C, the flow ratio of methane to hydrogen is 1:4, the deposition rate is 0.5-0.8 μm / h, and the thermal conductivity of the coating is ≥1800 W / (m·K).

Images