CN-122006993-A - Method for improving orange peel of aluminum alloy hub through thermal electrostatic spraying

CN122006993ACN 122006993 ACN122006993 ACN 122006993ACN-122006993-A

Abstract

The invention discloses a method for improving orange peel by thermal electrostatic spraying of an aluminum alloy hub, and belongs to the technical field of metal surface treatment. Aims to solve the problems of prominent orange peel defect, contradiction between coating hardness and adhesive force and the like in bright-black aluminum alloy hub coating. The method comprises the steps of raising the dehydration heating temperature to 150 ℃, canceling forced cooling, enabling a workpiece to be subjected to thermal electrostatic spraying of high-leveling orange peel resistant black powder at 65-80 ℃, then sequentially spraying black paint and high-solid-content lacquer, enabling the black paint and the high-solid-content lacquer to be fused at an interface and then be cured together, and enabling surface layer lacquer to be subjected to suspension cup type electrostatic spraying to achieve ultra-thick uniform coating. Meanwhile, the central cap groove part adopts a universal protection plug with a conical head part, and reliable sealing is realized through linear contact. The invention can obviously improve the orange peel problem, ensures that the coating has high hardness and excellent adhesive force, simplifies the process and reduces the cost, and is particularly suitable for the coating production of high-end bright black aluminum alloy hubs.

Inventors

ZHANG WEIZHONG
ZHANG HAIJUN
Liu Zhongshao
XUE FENG
ZHANG LINSHENG
GAO JIEYU
WU MING
ZHU ZUOGAO
GUO SHIHUI

Assignees

无锡锦绣轮毂有限公司

Dates

Publication Date: 20260512
Application Date: 20260123

Claims (10)

1. A method for improving orange peel of an aluminum alloy hub by thermal electrostatic spraying, which is characterized by comprising the following steps: S1, dehydrating and heating the workpiece, namely dehydrating and heating the pretreated aluminum alloy hub, wherein the heating temperature is 150+/-10 ℃ and the time is 5-10 minutes; S2, carrying out thermal electrostatic spraying on black powder, namely naturally cooling the workpiece treated in the step S1 to 65-80 ℃, then carrying out electrostatic spraying on anti-orange peel black powder at the temperature, and then baking and curing for 8-15 minutes at 180 ℃ to form a black powder coating; S3, spraying black paint, namely preheating a workpiece to 32+/-8 ℃, preheating the black paint to 15-30 ℃, carrying out electrostatic spraying on the black powder coating formed in the S2, and carrying out leveling and surface drying according to preset time; s4, spraying high-solid-content lacquer on the electrostatic rotary cup, namely maintaining the preheating temperature of the workpiece to be 30+/-10 ℃, preheating the high-solid-content lacquer to be 15-30 ℃, performing electrostatic rotary cup spraying on the black lacquer coating after the surface drying in S3, and leveling and surface drying according to preset time; And S5, integrally baking and curing, namely baking and curing the whole workpiece for 20-25 minutes at 140 ℃ after the black paint and the high-solid-content lacquer are sprayed.
2. The method for improving orange peel by thermal electrostatic spraying of the aluminum alloy hub according to claim 1, wherein the black powder is formed by thermal electrostatic spraying in the step S2, and the black powder comprises the following components in percentage by mass: 40% of epoxy resin, 40% of polyester resin, 14% of filler, 5% of additive, 1% of pigment and the mass deviation of each component is +/-8%.
3. The method for improving orange peel by thermal electrostatic spraying of the aluminum alloy hub according to claim 1, wherein the technological parameters of the thermal electrostatic spraying of the black powder in the S2 are as follows: the atomization pressure is 4.5-6.5 m 3 /h; the powder discharge amount is 20-35%; The electrostatic current is 5-10 mu A; electrostatic high voltage is 55-65 KV; the air pressure is 0.4-0.7 mpa.
4. The method for improving orange peel by thermal electrostatic spraying of an aluminum alloy hub according to claim 3, wherein a plurality of electrostatic spray guns are adopted for partition spraying, the powder discharge amount is set to be 20-30% for a front plane area of the hub, and the powder discharge amount is set to be 30-35% for a window, an included angle and an edge area of the hub.
5. The method for improving orange peel by thermal electrostatic spraying of the aluminum alloy hub according to claim 1, wherein the S3 spraying black paint comprises the following components in percentage by mass: 30% of inorganic pigment, 2% of n-butyl alcohol, 4% of n-butyl acetate, 12% of dimethylbenzene, 38% of acrylic resin, 12% of amino resin and the mass deviation of each component is +/-10%.
6. The method for improving orange peel by thermal electrostatic spraying of the aluminum alloy hub according to claim 1, wherein the technological parameters of the S3 spray black paint are as follows: turbine air pressure is 0.45-0.6 mpa Electrostatic current of 5-10 mu A And adopting a first spray gun with the flow rate of 400-450 cc/min and a second spray gun with the flow rate of 250-300 cc/min for matched spraying.
7. The method for improving orange peel by thermal electrostatic spraying of the aluminum alloy hub according to claim 1, wherein the S4 electrostatic spinning cup spraying high-solid-content lacquer comprises the following components in percentage by mass: 3% of leveling agent, 2% of n-butanol, 17% of dimethylbenzene, 15% of amino resin, 63% of acrylic resin and the mass deviation of each component is +/-6%.
8. The method for improving orange peel by thermal electrostatic spraying of the aluminum alloy hub according to claim 1, wherein the technological parameters of the S4 electrostatic spinning cup spraying high-solid-content lacquer are as follows: turbine air pressure is 0.45-0.6 mpa Electrostatic current of 5-10 mu A And adopting a first rotary cup spray gun with the flow rate of 380-420 cc/min and a second rotary cup spray gun with the flow rate of 300-350 cc/min for matched spraying.
9. The method for improving orange peel by hot electrostatic spraying of an aluminum alloy hub according to claim 1, wherein, The thickness of the black powder coating formed by the S2 is 110-145 mu m; the thickness of the black paint coating formed in the step S3 is 15-25 mu m; the thickness of the high-solid-content lacquer coating formed by the S4 is more than or equal to 40 mu m.
10. The method for improving orange peel by thermal electrostatic spraying of an aluminum alloy hub according to claim 1, wherein a protective plug is used at a central cap groove part in the spraying process of the workpiece, the protective plug forms linear contact seal with the orifice edge of a hub assembling surface through a conical inclined surface of a head part of the protective plug, and the cone angle of the conical surface ranges from 30 degrees to 70 degrees.

Description

Method for improving orange peel of aluminum alloy hub through thermal electrostatic spraying Technical Field The invention relates to the technical field of metal surface treatment, in particular to a method for improving orange peel by thermal electrostatic spraying of an aluminum alloy hub. Background Aluminum alloy hubs have become the standard configuration of modern automobiles due to their light weight, high strength and good heat dissipation properties. Among them, the bright-black wheel hub has a profound and advanced visual perception, and has long been in the market mainstream. The requirements of the market on the appearance quality of the hub are increasingly improved, particularly the smoothness of the surface, and one of the core evaluation indexes is the orange peel grade after spraying. Orange peel refers to tiny ripple-like defects on the surface of a coating, and the appearance texture and optical mirror effect of a product are seriously affected. In the coating production of aluminum alloy hubs, a composite process of a powder bottom layer and a liquid finish paint is generally adopted. However, in actual production, the orange peel problem of bright black products is significantly higher than other low gloss or gray-based high gloss products. This phenomenon has become a common problem in the industry, mainly due to: First, optically, the bright black color has a "magnifying effect" on surface defects. The bright black color pursues extremely high specular reflectivity, and any microscopic surface relief distorts, blurs, and creates a strong visual contrast in the reflected image. The light-colored or matte surface can effectively cover up tiny unevenness through the scattering effect of light rays. Second, the bright black coating itself has a contradiction of "leveling and curing" in terms of material properties. To achieve high jetness, it is necessary to add large amounts of fine carbon black pigments which can significantly increase the viscosity of the coating system and prevent it from flowing (leveling). In order to be effective, the curing reaction must be carried out rapidly, and the viscosity increases rapidly and the flow stops once crosslinking begins. Thus, the time window left for the coating to level is very short and demanding. Thirdly, from the aspect of process control, the existing flow has the following problems: the energy waste and thermal stress are that the energy consumption is high in the heating-forced cooling mode, and the adhesion of the coating can be affected by the severe temperature change. The leveling power is insufficient, powder is sprayed on a low-temperature workpiece, the melting start is slow, and the effective leveling time is short. The uniformity of the film thickness is difficult to ensure, the electric field distribution is uneven due to the complex hub shape, the film thickness uniformity of all parts is difficult to realize, and the tiny film thickness difference can be directly displayed as orange peel under bright black. Interlayer bonding contradicts hardness by often requiring incomplete cure of the primer to ensure interlayer adhesion, which may compromise the overall hardness of the final coating, and conversely, if the primer is completely cured, the topcoat adhesion is difficult. Fourth, from the frock is assisted, lacks high-efficient general scheme. The protection of wheel hub adopts the special protection of "one type is stifled" more, and the commonality is poor, and the management cost is high, and sealed effect is not good easily to lead to coating pollution assembly face, influences follow-up vehicle assembly. Currently, there is no systematic, effective solution to the orange peel problem of bright-black hubs in the industry. Most enterprises still rely on the traditional process, the appearance is barely controlled through post polishing and reworking, the production efficiency is low, the orange peel problem cannot be effectively improved, in addition, the combination of the black powder, the black paint and the transparent powder at the bottom layer is adopted, the powder is not transported and stored at a constant temperature, the maintenance and storage are troublesome, the unit price of the powder is 2.5-3 times that of the paint, and the cost is high. Therefore, development of a novel coating process capable of fundamentally improving the orange peel defect of the bright-black aluminum alloy hub is needed. Disclosure of Invention The invention provides a method for improving orange peel by thermal electrostatic spraying of an aluminum alloy hub, which aims to solve the problems that bright black coating orange peel has prominent defects and is difficult to control, the traditional heating-forced cooling spraying process has high energy consumption and low efficiency and is unfavorable for leveling, the uniformity of electrostatic spraying film thickness of a complex three-dimensional hub workpiece is difficult to en