Method for preventing and controlling rust black spots in curing period of UV spraying steel shell

Abstract

The invention discloses a method for preventing and controlling rust black spots in the curing period of a UV (ultraviolet) sprayed steel shell, which comprises the following steps of: 1, cleaning the surface of the steel shell by using a pulse fiber laser, controlling the power to be 65-80% of the reference power, and controlling the cleaning time to be 8-20 seconds; 2, UV printing ink is sprayed on the surface of the cleaned steel shell, the viscosity of the printing ink is 32-38 Pa.s at the temperature of 25 DEG C, and the printing ink is prepared from acrylate modified epoxy resin serving as main resin, a reaction diluent containing HDDA and a photoinitiator containing TPO; and curing to form the protective film. According to the method, the laser cleaning power of the steel shell is accurately controlled within the range of 78-96 kW, and Ra is made to be within the range of 0.8-1.5 microns; and the resin proportion in the UV ink is adjusted, so that the viscosity of the ink at 25 DEG C is 32-38Pa. S, the rust black spots are thoroughly eliminated, the appearance quality of the battery is improved, and the long-term stable performance of the battery is ensured.

Description

Technical Field

[0001] This invention relates to the field of UV coating inspection technology for steel shells, and in particular to a method for preventing rust spots during the curing period of UV-coated steel shells. Background Technology

[0002] Lithium-ion batteries, as core energy storage devices in modern consumer electronics, industrial equipment, and electric vehicles, directly impact the market competitiveness of end products. Among numerous battery packaging solutions, steel-cased batteries have become the preferred choice for high-end applications due to their superior mechanical strength, reliable sealing performance, and excellent safety characteristics. In the surface treatment processes of steel-cased lithium-ion batteries, UV coating technology holds a crucial position due to its unique advantages. This process forms a dense, high-strength protective film on the outer casing surface through ultraviolet light curing, significantly improving the casing's wear resistance, corrosion resistance, and environmental adaptability. A high-quality UV coating not only buffers the impact of external temperature fluctuations on battery performance but also reduces the risk of localized overheating by improving surface thermal conductivity, preventing performance degradation caused by uneven heat dissipation. Simultaneously, a uniform and dense coating effectively eliminates surface micro-defects, reducing the risk of structural damage caused by stress concentration, thereby improving the battery's operational stability under complex operating conditions.

[0003] However, steel-cased batteries face the following technical drawbacks in UV coating processes: 1) Rust and black spot problems: Black spot defects easily appear on the surface of the steel casing after coating and curing during storage; 2) Performance impact: Black spots lead to poor appearance, reducing product market competitiveness; they also damage the density of the coating, weakening the adhesion between the coating and the steel casing substrate; and may accelerate localized corrosion, affecting the long-term reliability of the battery. Existing technologies have not effectively solved this problem, and an optimized solution for the UV coating process of steel casings is urgently needed to eliminate rust and black spot defects and ensure battery performance and yield. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preventing rust spots during the curing period of UV-coated steel shells.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preventing rust spots on UV-coated steel shells during the curing period is provided, comprising the following steps:

[0007] Step 1, laser cleaning treatment:

[0008] The steel shell surface is cleaned using a pulsed fiber laser, with the power controlled at 65-80% of the reference power, the scanning frequency at 200-300Hz, the cleaning time at 8-20s, and the scanning linear speed at 0.6-1.0m / s.

[0009] Step 2, Ink Coating and Curing:

[0010] A UV ink is sprayed onto the cleaned steel shell surface. The ink has a viscosity of 32-38 Pa·s at 25°C and includes the following components: acrylate-modified epoxy resin as the main resin, a reaction diluent containing 1,6-hexanediol diacrylate (HDDA), and a photoinitiator containing 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO); subsequently, UV curing is performed to form a protective film.

[0011] Furthermore, in step one, the value of the reference power is 120W.

[0012] Furthermore, in step one, the laser wavelength used is 1064nm and the pulse width is 100ns.

[0013] Furthermore, the surface roughness Ra of the steel shell after cleaning is controlled within the range of 0.8-1.5μm.

[0014] Furthermore, the steel shell is made of carbon steel or stainless steel.

[0015] Furthermore, in step one, the laser cleaning treatment ensures that the residual oxygen content on the steel shell surface is ≤5at and the residual carbon content is ≤8at.

[0016] Furthermore, in step two, the curing conditions are: light intensity 1000-1500 mW / cm². 2 Irradiation time: 1-5 seconds.

[0017] Furthermore, the protective film formed in step two has an adhesion level of 0 to 1 and no rust spots are generated after a salt spray test of ≥1200 hours.

[0018] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0019] This invention achieves the complete elimination of rust spots, improves the appearance quality of the battery, and ensures its long-term stable performance by precisely controlling the laser cleaning power of the steel shell within the range of 78-96kW, resulting in a surface roughness Ra within the range of 0.8-1.5μm; and by adjusting the resin ratio in the UV ink so that the ink viscosity is 32-38Pa·s at 25℃. Attached Figure Description

[0020] Figure 1 This is a macroscopic photograph of the UV-coated steel shell in Example 1 after a 1200-hour salt spray test.

[0021] Figure 2 This is a macroscopic photograph of the UV-coated steel shell in Comparative Example 2 after 1200 hours of salt spray testing. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0023] Example 1

[0024] This embodiment provides a method for preventing rust spots on UV-coated steel shells during the curing period, specifically including:

[0025] 1. Test substrate

[0026] Material: SPCC carbon steel housing (Dimensions: 100mm × 50mm × 0.8mm)

[0027] Initial state: The surface has a slight oxide layer and oil stains (simulating a warehouse environment).

[0028] 2. Laser cleaning treatment

[0029] Equipment: Pulsed fiber laser (wavelength 1064nm, pulse width 100ns)

[0030] Parameters: Base power: 120W → Actual power: 84W (120W × 70%)

[0031] Scan frequency: 240Hz

[0032] Scan line speed: 0.69 m / s

[0033] Cleaning time: 12.5s

[0034] Post-cleaning inspection: Roughness Ra = 1.2 μm (measured with a white light interferometer)

[0035] Surface elemental analysis (EDS): Oxygen residue 4.2 at%, Carbon residue 6.5 at%.

[0036] 3. UV ink coating and curing

[0037] Ink formulation: Acrylic modified epoxy resin (70.9 wt%) + reactive diluent HDDA (14.3 wt%) + photoinitiator TPO (7.6 wt%) + anti-settling agent (4 wt%) + leveling agent (3.2 wt%)

[0038] Viscosity at 25℃: 35 Pa·s (rotational viscometer)

[0039] Coating method: Electrostatic spraying (film thickness 25±2μm)

[0040] UV curing parameters: light intensity 1200mW / cm 2 Irradiation time 2s

[0041] Atmosphere: Air environment

[0042] 4. Performance test results (see Table 1 below)

[0043] Table 1

[0044]

[0045]

[0046] Example 2

[0047] This embodiment provides a method for preventing rust spots on UV-coated steel shells during the curing period, specifically including:

[0048] 1. Test substrate

[0049] Material: SUS304 stainless steel casing (dimensions same as in Example 1)

[0050] Initial state: The surface has welding oxide spots and fingerprint contamination.

[0051] 2. Laser cleaning treatment

[0052] Equipment: Same as in Example 1

[0053] Parameters: Base power: 120W → Actual power: 90W (120W × 75%)

[0054] Scan frequency: 280Hz

[0055] Scan line speed: 0.8 m / s

[0056] Cleaning time: 8 seconds

[0057] Post-cleaning inspection: Roughness Ra = 1.5 μm (measured with a white light interferometer)

[0058] Surface elemental analysis (EDS): Oxygen residue 3.8 at%, Carbon residue 5.1 at%.

[0059] 3. UV ink coating and curing

[0060] Ink formulation: Acrylic modified epoxy resin (76wt%) + reactive diluent HDDA (8.8wt%) + photoinitiator TPO (8wt%) + anti-settling agent (4wt%) + leveling agent (3.2wt%)

[0061] Viscosity at 25℃: 38 Pa·s (rotational viscometer)

[0062] Coating method: Electrostatic spraying (film thickness 25±2μm)

[0063] UV curing parameters: light intensity 1200mW / cm2 Irradiation time 2s

[0064] Atmosphere: Air environment

[0065] 4. Performance test results (see Table 2 below)

[0066] Table 2

[0067]

[0068] Comparative Example 1 (no laser cleaning, solvent wiping only)

[0069] 1. Substrate treatment

[0070] Same as Example 1, carbon steel casing, but wiped with acetone and then dried (no laser cleaning). 2. UV ink coating and curing.

[0071] Ink formulation and curing parameters: Same as in Example 1

[0072] 3. Performance test results (see Table 3 below)

[0073] Table 3

[0074]

[0075] Comparative Example 2 (Low Ink Viscosity)

[0076] 1. Substrate treatment

[0077] Same laser cleaning parameters as in Example 1

[0078] 2. UV ink coating and curing

[0079] Ink formulation: Acrylic modified epoxy resin (60wt%) + reactive diluent HDDA (27wt%) + photoinitiator TPO (5wt%) + anti-settling agent (3wt%) + leveling agent (5wt%)

[0080] Viscosity at 25℃: 25 Pa·s (rotational viscometer)

[0081] Curing parameters: Same as in Example 1

[0082] 3. Performance test results (see Table 4 below)

[0083] Table 4

[0084]

[0085] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preventing rust spots during the curing period of UV-coated steel shells, characterized in that, Includes the following steps: Step 1, laser cleaning treatment: The steel shell surface is cleaned using a pulsed fiber laser, with the power controlled at 65-80% of the reference power, the scanning frequency at 200-300Hz, the cleaning time at 8-20s, and the scanning linear speed at 0.6-1.0m / s. Step 2, Ink Coating and Curing: A UV ink is sprayed onto the cleaned steel shell surface. The ink has a viscosity of 32-38 Pa·s at 25°C and includes the following components: acrylate-modified epoxy resin as the main resin, a reaction diluent containing 1,6-hexanediol diacrylate (HDDA), and a photoinitiator containing 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO); subsequently, UV curing is performed to form a protective film.

2. The method according to claim 1, characterized in that, In step one, the reference power value is 120W.

3. The method according to claim 1, characterized in that, In step one, the laser wavelength used is 1064nm and the pulse width is 100ns.

4. The method according to claim 1, characterized in that, After cleaning, the surface roughness Ra of the steel shell is controlled within the range of 0.8-1.5μm.

5. The method according to claim 1, characterized in that, The steel shell is made of carbon steel or stainless steel.

6. The method according to claim 1, characterized in that, In step one, the laser cleaning process ensures that the residual oxygen content on the steel shell surface is ≤5at and the residual carbon content is ≤8at.

7. The method according to claim 1, characterized in that, In step two, the curing conditions are: light intensity 1000-1500 mW / cm². 2 Irradiation time: 1-5 seconds.

8. The method according to claim 1, characterized in that, The protective film formed in step two has an adhesion level of 0 to 1 and no rust spots are generated after a salt spray test of ≥1200 hours.

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