Surface treatment method of magnesium alloy battery tray

Abstract

The invention discloses a surface treatment method for a magnesium alloy battery tray. The surface treatment method comprises the following steps: S1, carrying out polishing cleaning and plasma cleaning on the surface of the battery tray; s2, carrying out surface energy detection on the battery tray, and shielding an area needing to be protected and shielded; s3, preheating is carried out; s4, an automatic spray gun is used for powder spraying, and then redundant residual powder is blown away; s5, baking and curing are carried out; the baking temperature is 180 to 200 DEG C, and the time is 15 to 25 minutes; and S6, the battery tray is dismounted, and surface inspection is qualified. According to the pretreatment process, plasma cleaning process equipment is simple, chemical reactions such as acid pickling and alkali washing are not needed, resources are saved, the pretreatment process is environmentally friendly and easy to operate, the surface quality of a product subjected to plasma cleaning is good for the adhesive force of a follow-up coating process, the adaptability to a metal welding process is good, and the surface quality of a polished weld joint is good. According to the process, good adhesive force and corrosion resistance can be guaranteed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnesium alloy surface treatment, and particularly relates to a surface treatment method of a magnesium alloy battery tray. BACKGROUND

[0002] The battery tray is one of the core components in the electric vehicle, and has the functions of bearing the power battery and protecting the battery. The existing battery tray is generally made of metal alloy, such as magnesium alloy, aluminum alloy, magnesium-aluminum alloy, etc. Since the magnesium alloy and the aluminum alloy have small density and high specific strength, the weight of the battery tray can be reduced and the cost can be saved.

[0003] However, the magnesium alloy or the magnesium-aluminum alloy has active chemical properties and is prone to corrosion, which affects the service life and structural strength, and thus generally needs to be subjected to surface corrosion prevention treatment. The commonly used surface corrosion prevention treatment process is chemical cleaning including passivation, and the chemical cleaning process is not suitable for the battery tray made of magnesium alloy or magnesium-aluminum alloy.

[0004] Patent document CN104805485A discloses a surface treatment method of die-cast aluminum alloy, which subjects the die-cast aluminum alloy after sand blasting treatment to anodic oxidation treatment to form an oxide film layer on the surface of the die-cast aluminum alloy. However, the method has the disadvantages of poor anodic oxidation scratch resistance and no insulation ability.

[0005] Patent document CN118988691A discloses a surface treatment method of an aluminum alloy battery tray, which includes the following steps: subjecting the aluminum alloy battery tray to degreasing treatment, alkali etching treatment and polishing treatment to obtain an aluminum alloy battery tray with a clean surface; immersing the aluminum alloy battery tray with a clean surface in a treatment liquid prepared in advance, the treatment liquid including nano-sodium silicate, sodium molybdate, tin chloride and ammonium phosphate, and the concentration of the nano-sodium silicate being 5g / L-8g / L, the concentration of the sodium molybdate being 12g / L-20g / L, the concentration of the tin chloride being 9g / L-13g / L, and the concentration of the ammonium phosphate being 7g / L-10g / L; and then drying and coating treatment, the coating material including the following preparation raw materials by weight: epoxy ethylene 30-45 parts, titanium dioxide 7-10 parts, sodium silicate 3-7 parts, N, N-dimethyl acrylamide 7-11 parts, boron nitride particles 1-20 parts, and ethyl cellulose 2-7 parts. However, the pretreatment of the document is chemical treatment, the magnesium alloy has active chemical properties and is prone to reaction, and thus it is difficult to adapt to the magnesium alloy or the product connected by welding or the like. SUMMARY

[0006] In order to enable the automobile battery tray with magnesium alloy as the base material to meet the demand of corrosion resistance, the application provides a surface treatment method of magnesium alloy battery tray, which adopts the process of combining plasma cleaning and powder spraying, and has high plasma cleaning efficiency, simple process and low production cost; the powder spraying has strong corrosion resistance, mature process and high production efficiency.

[0007] In order to achieve the above object, the application is realized by the following technical scheme: The surface treatment method of the magnesium alloy battery tray of the application comprises the following steps: S1, polishing and cleaning the surface of the battery tray, using a plasma robot cleaning device to perform surface plasma cleaning on the battery tray; S2, detecting the surface energy of the battery tray, and after passing the detection, transferring the battery tray to a powder spraying position, and shielding the area needing protection; S3, preheating: the furnace temperature of the heating furnace is 145-190 DEG C, and the product temperature is detected after preheating to be 60-80 DEG C; S4, powder spraying is performed using an automatic spray gun, and a manual spray gun is used to supplement powder to the concave corner of the product, and then the excess residual powder is blown away; S5, baking and curing; the baking temperature is 180-200 DEG C, and the time is 15-25 min; S6, removing the battery tray, removing the surface shielding tape, and passing the surface inspection.

[0008] The polishing and cleaning process is to polish and clean the battery tray using non-woven fabric, scouring pad and the like, and if the product contains a weld, the weld must be polished flat.

[0009] The plasma cleaning conditions are that the nozzle-to-bottom plate distance is 8-15 mm, the plasma machine power gear position is set to 9±0.5, the working current is 10-20 A, and the machine arm cleaning speed is 90-110 mm / s.

[0010] The magnesium alloy is an aluminum-free magnesium alloy or a magnesium-aluminum alloy; since the plasma cleaning is a physical cleaning method, no chemical medicine water is needed, and it is also applicable to dissimilar metal connection or other types of metal materials without special requirements.

[0011] The main component of the powder for powder spraying is 100% solid epoxy powder insulation coating, and the insulation resistance is greater than or equal to 550 MΩ; for example, the HNG49CC powder coating of AkzoNobel.

[0012] The film thickness of the powder coating is 250±50 mu m, and the adhesion is 0 level.

[0013] Compared with the prior art, the application has the following advantages: The pre-treatment process of the present application is a physical method cleaning. Compared with the common chemical pre-treatment such as passivation, the plasma cleaning process has simple equipment, does not need chemical reactions such as pickling and alkaline washing, saves resources, is green and environmentally friendly, is simple to operate, and the surface quality of the product after plasma cleaning shows good adhesion to the subsequent coating process. The plasma cleaning process has good adaptability to the metal welding process. For the polished weld, the process can ensure good adhesion and corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 A schematic diagram of a battery tray to be sprayed. DETAILED DESCRIPTION

[0015] A person of ordinary skill in the art should recognize that the embodiments are only used to illustrate the present application and are not used as a limitation to the present application. As long as the embodiments are changed and modified within the scope of the present application, they can be within the scope of the claims of the present application.

[0016] Embodiment 1 A surface treatment method of a magnesium alloy battery tray, comprising the following steps: (1) According to the process requirements, the magnesium alloy battery tray is polished and cleaned using non-woven fabric and scouring pad. If the product contains a weld, the weld must be polished flat; (2) After the equipment is started, the battery tray is placed on the plasma robot cleaning equipment and positioned according to the tooling; (3) The battery tray is surface plasma cleaned using the plasma robot cleaning equipment. The conditions for plasma cleaning are: nozzle-to-bottom plate distance 10 mm, plasma machine power setting 9±0.5, working current 15 A, and machine arm cleaning speed 105 mm / s. A stable blue arc must appear during the plasma cleaning process; (4) After the plasma cleaning is completed, the surface energy is detected using a Dyne pen at four corners and in the middle of the front and rear of the bottom plate. After the surface energy detection is qualified, the Dyne pen marks are wiped off using alcohol. The plasma processing time is marked at the front end of the box after the plasma processing is completed. After the qualification, the battery tray is transferred to the powder spraying place; After the plasma cleaning is completed, the powder spraying operation must be performed within 4 hours. If the equipment fails and the powder spraying operation cannot be performed in time, resulting in a time exceeding 4 hours, the plasma processing must be performed again; (5) The areas that need to be protected and shielded are shielded using high-temperature adhesive tape. Red adhesive tape is used to protect the hooks and the edges of the contact powder spraying place; (6) Preheating: the furnace temperature of the heating furnace is set to 160±5℃. The furnace temperature is detected and confirmed using a furnace temperature instrument every week. The temperature of the product body is detected using a temperature measuring instrument after preheating. The temperature range is 60-80℃. The product after preheating has stronger bonding force with the powder. (7) using an automatic spray gun to spray the powder coating by electrostatic powder spraying, using a manual spray gun to supplement powder to the concave corner of the product, and blowing off the excess residual powder on the upper end of the hanger after spraying; the powder used for powder spraying is HNG49CC powder coating from AkzoNobel; (8) baking and curing; the baking temperature is 195°C, and the curing time is 10 min; Steps (7) and (8) are repeated to perform automatic powder spraying and baking and curing at least twice.

[0017] (9) removing the battery tray, removing the surface shielding tape, and checking for qualification.

[0018] Example 2 The surface treatment method of the magnesium-aluminum composite battery tray in Example 2 is basically the same as that in Example 1, except that the battery tray to be surface treated is not a single metal product, but a magnesium alloy and an aluminum alloy connected by a welding process; the nozzle-to-bottom plate distance is 12 mm, the plasma machine power gear is set to 9±0.5, the working current is 15 A, and the machine arm cleaning speed is 90 mm / s; the powder coating is sprayed by electrostatic powder spraying, the baking and curing temperature is 185°C, and the curing time is 18 min.

[0019] Example 3 The surface treatment method of the magnesium-aluminum alloy battery tray in Example 3 is basically the same as that in Example 1, except that the nozzle-to-bottom plate distance is 10 mm, the plasma machine power gear is set to 10±0.5, the working current is 18 A, and the machine arm cleaning speed is 100 mm / s; the powder coating is sprayed by electrostatic powder spraying, the baking and curing temperature is 190°C, and the curing time is 15 min.

[0020] Comparative Example 1 The surface treatment method of the magnesium-aluminum composite battery tray in Comparative Example 1 is basically the same as that in Example 2, both of which are magnesium-aluminum composite battery trays connected by a welding process of a magnesium alloy and an aluminum alloy, except that the pretreatment process used in Example 2 is a plasma cleaning process, and the pretreatment process used in Comparative Example 1 is a common chemical pretreatment process used for aluminum alloy products. The electrostatic powder spraying processes used in both are completely the same, the powder coating is sprayed by electrostatic powder spraying, the baking and curing temperature is 185°C, and the curing time is 18 min.

[0021] Detection Experiment Example The insulating property of the powder coating is detected according to GB 38031-2020 Safety requirements for power storage batteries for electric vehicles - Appendix B Test method for insulation resistance of battery pack or system; the average film thickness of the powder coating is detected according to the provisions of GB / T 13452.2-2008 Paints and varnishes Determination of film thickness; and the adhesion is detected according to the provisions of GB / T 9286-2021 Paints and varnishes Cross-hatch test.

[0022] Among them, example 2 and comparative example 1 are both products of magnesium alloy and aluminum alloy connected by welding process, so the average film thickness and adhesion of the powder coating of the magnesium alloy part and the aluminum alloy part of the product need to be detected respectively.

[0023] Table 1 Detection results of examples 1-3 and comparative example 1 As can be seen from table 1, the adaptability of the present application to different metals is high, especially for products connected by different metal combinations (such as welding process), compared with common chemical pretreatment process, the chemical solution used generally only adapts to specific metals, since the pretreatment chemical solution of comparative example 1 mainly adapts to aluminum alloy, so the adhesion is measured at the aluminum alloy part, the adhesion of the two processes of example 2 and comparative example 1 at the aluminum alloy part is 0 level, and the average film thickness of the powder coating meets the requirements, but the adhesion is measured at the magnesium alloy part, the adhesion of the magnesium alloy of comparative example 1 is only 2 level, and the average film thickness of the powder coating does not meet the requirements; at the same time, the plasma cleaning process is used as the pretreatment process before powder spraying, without the need to develop and replace chemical solution, which improves the production efficiency of the spraying production line.

Claims

1. A surface treatment method for a magnesium alloy battery tray, characterized in that: The following steps are involved: S1, grinding and cleaning the surface of the battery tray and plasma cleaning; S2, perform surface energy testing on the battery tray. If qualified, transfer the battery tray to the powder spraying area and mask the area that needs protection; S3, preheating: the temperature of the heating furnace is 145 ~ 190 ℃, and the product temperature after preheating is detected to be 60 ~ 80 ℃; S4, use an automatic spray gun for powder spraying, use a manual spray gun to add powder to the concave corners of the product, and then blow away the excess powder; S5, baking and curing; the baking temperature is 180-200°C, and the time is 15-25 minutes; S6, remove the battery tray, remove the surface masking tape, and check the surface to see if it is qualified.

2. The surface treatment method of a magnesium alloy battery tray according to claim 1, characterized in that: The polishing and cleaning process is to polish and clean the battery tray with non-woven fabric or scouring pad. If the product contains welds, the welds must be polished smooth.

3. The surface treatment method of the magnesium alloy battery tray according to claim 1, characterized in that: The plasma cleaning conditions are as follows: the distance between the nozzle and the base plate is 8 to 15 mm, the power level of the plasma machine is set to 9±0.5, the working current is 10 to 20 A, and the cleaning speed of the robot arm is 90 to 110 mm / s.

4. The surface treatment method of a magnesium alloy battery tray according to claim 1, characterized in that: The main component of the powder sprayed is 100% solid epoxy powder insulating paint, and the insulation resistance is ≥550MΩ.

5. The surface treatment method of a magnesium alloy battery tray according to claim 1, characterized in that: The powder coating has a film thickness of 250±50 μm and an adhesion level of 0.

Images