Patent Description:
Aluminum wheel hubs are important exterior parts of automobiles, and their external beauty and color match directly attract the attention of consumers. With people's demand for the use of automobiles, the personalization and differentiation of wheel appearance have become the focus of everyone's attention. The fashion and dynamics of wheel hubs have become a mainstream of the times.

However, when edging is performed on other paint of a wheel, the sprayed area of the edged paint is narrow and the condition is complicated, so it is difficult to obtain an edged paint surface with high fastness. The existing shielded color register spraying process has the problems of low production efficiency, low qualification rate, unclear boundary of the color register part, high labor intensity and the like. <CIT> relates to a method for color register spraying of a hub.

Accordingly, the object of the present invention is to provide a uniform color register edging method for an aluminum alloy hub as specified in any one of claims <NUM> to <NUM>.

In a preferred aspect of the present invention, in steps I, III and V, the first, second and third pretreatment and drying steps sequentially include <NUM> processes: washing, pre-degreasing, degreasing, washing, acid pickling, washing, passivation, washing, closing, washing and drying; an electrostatic gun is adopted for spraying body powder in step II, the distance between the electrostatic gun and the surface of a wheel is <NUM>, the throughput of the powder gun is <NUM><NUM>/h, the atomizing pressure is <NUM> bar, the electrostatic pressure is controlled at <NUM> KV, the front spray thickness is <NUM>, the body powder curing temperature is <NUM>, and the holding time is <NUM>; an air gun is adopted for spraying a paint in step II, the distance between the air gun and the surface of the wheel is <NUM>, the throughput of the spray gun is <NUM> cc/min, the atomizing pressure is <NUM> bar, the sector pressure is <NUM> bar, the paint spray thickness is <NUM>, the temperature of the wheel workpiece is <NUM>-<NUM>, the paint curing temperature is <NUM>, and the holding time is <NUM>; in edging color register spraying of step IV, the injection needle has a caliber of <NUM>, the hub is horizontally placed on an automatic rotary table, the needle is fixed on an adjustable bracket, a paint supply system is closed, the distance between the needle and the sprayed surface of the wheel is <NUM>, the flow rate of the injected paint is <NUM> cc/min, the power of the automatic rotary table is <NUM>, and the air pressure of the closed paint supply system is <NUM> bar; electrostatic spraying is adopted in the high-gloss transparent powder spraying process of step VI, the distance between the electrostatic gun and the surface of the wheel is <NUM>, the throughput of the powder gun is <NUM><NUM>/h, the atomizing pressure is <NUM> bar, the electrostatic pressure is <NUM> KV, the front spray thickness is about <NUM>, the transparent powder curing temperature is <NUM>, and the holding time is <NUM>.

In steps I, III and V, the first, second and third pretreatment and drying steps sequentially include <NUM> processes: washing, pre-degreasing, degreasing, washing, acid pickling, washing, passivation, washing, closing, washing and drying; an electrostatic gun is adopted for spraying body powder in step II, the distance between the electrostatic gun and the surface of a wheel is <NUM>, the throughput of the powder gun is <NUM><NUM>/h, the atomizing pressure is <NUM> bar, the electrostatic pressure is controlled at <NUM> KV, the front spray thickness is <NUM>, the body powder curing temperature is <NUM>, and the holding time is <NUM>; an air gun is adopted for spraying a paint in step II, the distance between the air gun and the surface of the wheel is <NUM>, the throughput of the spray gun is <NUM> cc/min, the atomizing pressure is <NUM> bar, the sector pressure is <NUM> bar, the paint spray thickness is <NUM>, the temperature of the wheel workpiece is <NUM>-<NUM>, the paint curing temperature is <NUM>, and the holding time is <NUM>; in edging color register spraying of step IV, the injection needle has a caliber of <NUM>, the hub is horizontally placed on an automatic rotary table, the needle is fixed on an adjustable bracket, a paint supply system is closed, the distance between the needle and the sprayed surface of the wheel is <NUM>, the flow rate of the injected paint is <NUM> cc/min, the power of the automatic rotary table is <NUM>, and the air pressure of the closed paint supply system is <NUM> bar; electrostatic spraying is adopted in the high-gloss transparent powder spraying process of step VI, the distance between the electrostatic gun and the surface of the wheel is <NUM>, the throughput of the powder gun is <NUM><NUM>/h, the atomizing pressure is <NUM> bar, the electrostatic pressure is <NUM> KV, the front spray thickness is about <NUM>, the transparent powder curing temperature is <NUM>, and the holding time is <NUM>.

The condition of each step in this embodiment is substantially the same as that in Embodiment <NUM>, except that step VI further includes the step of ultrasonic treatment, ultrasonic waves are applied to the wheel in a pulsed manner, each pulse lasts for <NUM>, and the energy density is 400W/cm<NUM>.

The condition of each step in this embodiment is substantially the same as that in Embodiment <NUM>, except that step VI further includes the step of ultrasonic treatment, ultrasonic waves are applied to the wheel in a pulsed manner, each pulse lasts for <NUM>, and the energy density is 120W/cm<NUM>.

The condition of each step in this embodiment is substantially the same as that in Embodiment <NUM>, except that step VI further includes the step of ultrasonic treatment, ultrasonic waves are applied to the wheel in a pulsed manner, each pulse lasts for <NUM>, and the energy density is <NUM> W/cm<NUM>.

The condition of each step in this embodiment is substantially the same as that in Embodiment <NUM>, except that a spray gun is used for spraying a paint at a small flow rate and a low angle in step IV, the distance between the spray head and the sprayed surface of the wheel is <NUM>, the flow rate of the injected paint is <NUM> cc/min, the power of the automatic rotary table is <NUM>, and the air pressure of a closed paint supply system is <NUM> bar.

Edged products having bright color and sprayed uniformly are obtained from Embodiments <NUM>-<NUM> and Comparative Example <NUM>.

First, the edge of the edged area of the product of each embodiment or the comparative example is observed with a magnifying glass. The edged area of the product of each embodiment or the comparative example is observed under an 8x magnifying glass, and the numbers of edge splashing points and edge protruding points within <NUM> are calculated. The edge splashing points are calculated as <NUM> scores, and the edge protruding points are calculated as <NUM> score. Five samples of the edged area of each product are counted and averaged. The results are shown in Table <NUM>.

It can be seen from the above statistical results that the edge defects are greatly reduced by replacing the nozzle with a syringe. In addition, the applicant also pleasantly surprised to find that the edge defects were further reduced by ultrasonic treatment.

Fastness test is performed on the edged product of Embodiments <NUM>-<NUM> and Comparative Example <NUM>. The specific method is to scribe <NUM> parallel lines every <NUM> using a paper knife on a sample of each edged product, and then scribe <NUM> lines in the vertical direction to reach a metal layer. Then, a transparent tape is adhered to the drawn area firmly by light pressing. After <NUM>, the transparent tape is torn, and the damaged or peeled part in <NUM>*<NUM> grids is calculated. The test is carried out five times in parallel and the average value is taken, and the test results are shown in Table <NUM>.

It can also be seen from the results of this embodiment that the edge defects are greatly reduced by replacing the nozzle with a syringe. In addition, the applicant also pleasantly surprised to find that the edge defects were further reduced by ultrasonic treatment. holding time is <NUM>; in edging color register spraying of step IV, the injection needle has a caliber of <NUM>, the hub is horizontally placed on an automatic rotary table, the needle is fixed on an adjustable bracket, a paint supply system is closed, the distance between the needle and the sprayed surface of the wheel is <NUM>, the flow rate of the injected paint is <NUM> cc/min, the power of the automatic rotary table is <NUM>, and the air pressure of the closed paint supply system is <NUM> bar; electrostatic spraying is adopted in the high-gloss transparent powder spraying process of step VI, the distance between the electrostatic gun and the surface of the wheel is <NUM>, the throughput of the powder gun is <NUM><NUM>/h, the atomizing pressure is <NUM> bar, the electrostatic pressure is <NUM> KV, the front spray thickness is about <NUM>, the transparent powder curing temperature is <NUM>, and the holding time is <NUM>.

Claim 1:
A color register edging method for an aluminum alloy hub, wherein including the following steps: (I) a first pretreatment and drying step, including washing, degreasing, acid pickling and passivation; (II) a body powder spraying and curing step, and a subsequent paint spraying and curing step; (III) a second pretreatment and drying step, including washing, degreasing, acid pickling and passivation; (IV) an edging color register applying and curing step, wherein a color register paint is squeezed onto a surface that needs color register by using an injection needle; (V) a third pretreatment and drying step, including washing, degreasing, acid pickling and passivation; and (VI) a high-gloss transparent powder spraying and curing step.