Catalytic combustion infrared radiation curing technology in the field of hub powder coating applications

Abstract
paper, in view of the current situation in the field of hub coating, proposes to cure powder coating by catalytic combustion infrared radiation. The temperature change of the coating film during the curing process of infrared radiation was studied, and the curing degree of the coating film was tested to be 1.44 degrees C. The initial adhesion of the coating film, CASS, gravel impact resistance and water resistance tests all meet the requirements of performance indicators and

. After infrared curing, the hub elongation rate is comparable to that of hot air curing, and the pull resistance and yield strength are better than that of hot air curing process. After energy consumption analysis, catalytic combustion infrared radiation curing can save natural gas costs of 760,000 yuan / year, saving 63% of the floor space. Catalytic combustion infrared radiation curing has excellent appearance, good paint film performance, stable substation material performance, low energy consumption, space saving and many other advantages, suitable for the field of hub coating.
1 foreword
hub production process for smelting - die-casting - machining - coating, the existing aluminum alloy hub coating production line mainly uses natural gas heat air cycle curing technology, the technology for indirect heating, high energy consumption, heat from the surface of the work piece slowly transfer to the inside of the coating, thermal efficiency of less than 30%. Heat air curing is heat conduction heating from the table, the gas produced in the curing process can easily remain in the coating to form bubbles, and due to the flow of air, the curing process is easy to cause secondary dust pollution, resulting in a decrease in the quality of the coating.
infrared radiation heating technology was first developed in 1953 by France's Sengis Marte and applied to the coating curing industry. The technology uses precious metals, rare earth oxides, calcium and titanium ore as catalysts, natural gas on the surface of the catalyst flame-free combustion, energy is almost completely released by infrared radiation, specific wavelengths of infrared and organic coating molecular resonance, so that the coating quickly heats up and cures, combustion energy is the most full and effective use. Infrared curing has many advantages compared with traditional hot air curing methods:
(1) energy efficiency is high.
Infrared curing directly actes on the coating in the form of radiation, reducing the loss of heat during transmission, and the resulting infrared wavelength matches the absorption wavelength of the powder coating, while the aluminum substate is barely absorbed, thus achieving the effect of heating only the coating without heating the aluminum substate.
(2) paint film curing quality is high.
infrared curing does not require rapid circulation of wind, which reduces the effect of dust in the air.
(3) covers a small area.
infrared radiation curing heating speed, the required distance is short, the area is much smaller than the hot air cycle oven.
(4) environmental protection.
gas infrared catalytic panel enables combustibles to burn flame-free under the action of catalysts, produced by water and carbon dioxide, without exhaust gases, dust and other pollutants discharged.
(5) curing time is short.
infrared radiation heating heat directly on the coating, heating speed is fast, heat transfer efficiency is high, can shorten the lacquer film curing time, paint film infrared radiation curing time is about 1/2 to 1/10 heating curing time of the hot air cycle.
combined with the many advantages of catalytic combustion infrared radiation curing, it has great potential for development in the field of hub coating.2 Test materials and equipment
materials and equipment used in the test are purchased on the market or homemade.
2.1 Experimental materials
Tab. 1 The materials used in the experiment
2.2 experimental equipment
catalytic combustion infrared radiation curing oven, hot air cycle curing oven, differential heat analyzer (DSC), salt spray test box, water immersion test box, gravel impact test bench, stretch test machine.3 Test Method
3.1 Powder Curing Process
Process 1: Aluminum Wheels→ Pre-treatment→ 110 degrees C after drying.
process 2: aluminum wheels → pre-→ spray transparent powder→ hot air 200 degrees C curing 38min.
process 3: aluminum wheels → pre-→ spray transparent powder → infrared 200 degrees C curing 12min.
3.2 differential heat analyzer test program
The Tg1:20C→10C/min rate heats up to 80C→10C/min rate heats up to 250C
Tg2:250C→10C/min rate cools to 20C→ thermostat 1min to 20C→10C/min rate cools to 150C.
3.3 Paint film performance test
3.3.1 adhesion test
reference GB/T 9286-1998.
conditions: characteristic value ≤1
3.3.2CASS test
refringing GB/T 10125-2012, sodium chloride content: 50 ± 5g /L, PH value: 3.1-3.3, temperature: 50 ± 2 oC, salt spray: 1.0-2.0ml/h, CuCl
2
. H
2
O content: 0.26 ± 0.02g/L;
conditions: the corrosion width at the dash bilateral sum CMax ≤ 3mm.
3.3.3 gravel impact test
refred by SAE J400 (2012-10) test method, temperature: 25±5 degrees C, pebble volume: 0.5L, air pressure: (483±21) KPa, impact angle: 90 degrees, injection time: (10±1) s. The determination condition ≥ 4B
3.3.4 water resistance test
refred GB/T 30648.2-2015, temperature: 40±1 degree c immersion 240h, determination condition: secondary adhesion characteristic value≤1 4 results and discussion
4.1 appearance Fig. 1 Thermal air curing and infrared curing transparent powder wheel appearance comparison
As shown in Fig.1, process 2 hot air curing and process 3 infrared radiation curing made of transparent powder wheel appearance is good, there are no obvious impurity defects.
4.2 Curing degree
The curing degree of transparent powder on the surface of the hub is an important evaluation standard to measure the process of catalytic combustion infrared radiation curing, and the transparent powder is a prerequisite for the complete curing test to ensure the performance of the paint film.
4.2.1 furnace temperature curve
Fig. 2 Coating temperature and air temperature during infrared curing
the temperature change curve of wheel heart, spokes and air temperature under normal operation of infrared curing equipment is tested with furnace thermometer. Set the temperature of 200 degrees C, heating time of 12min, test results such as Fig. Shown in 1 (red curve for rim temperature, blue curve for wheel temperature, black curve for air temperature). The results show that during infrared curing, the rim temperature is up to 203 degrees C, the wheel heart temperature is up to 181 degrees C, and the air temperature is up to 167 degrees C. The wheel heart temperature is lower than the rim temperature is due to the large thickness of the base at the center of the wheel and thus absorbs more heat from the coating film, so the center of the wheel needs to be set as a temperature reference point, so that the entire hub surface powder coating can be completely cured. The air temperature is lower than that of the wheel surface coating film of about 35 degrees C, which proves that the infrared radiation energy mainly acts on the coating, and the air absorbs less energy, so as to achieve the goal of saving energy.
4.2.2 DSC test
after the end of the test to remove the sample wheel, scrape the spoke front coating film, DSC test to determine the degree of curing of the paint film, the test results are fig. 3.
Fig. 3 Infrared curing coating DSC result
glass transition temperature (Tg) is an important parameter of amorphous polymer, thermosolytic coating cross-curing reaction before and after Tg changes, if the reaction is complete, the corresponding Tg no longer changes. In engineering, the standard for determining the < is 2 degrees C for determining the complete curing of the coating. As shown in the figure, Tg1 is 71.35 degrees C, Tg2 is 72.79 degrees C, Tg2-Tg1 is 72.79-71.35 is 1.44 degrees C, and DSC results show that the powder coating can be completely cured by catalytic combustion infrared radiation.
4.3 Paint film performance
Initial adhesion initial adhesion, CASS test, gravel impact test and water resistance test on the wheels made of hot air curing and infrared curing, the test results are found in Tab. 2.
Tab. 2 Paint Film Performance Results
As shown by Tab. 2, the wheels obtained by the infrared curing method show the same level of initial adhesion, CASS, gravel impact resistance and water resistance as hot air curing wheels. Initial adhesion level 0, no coating peeling, proving that the curing method obtained by the coating film and substation binding force is good. CASS test bilateral corrosion width of 1.3mm, proving that the curing method obtained excellent corrosion resistance of the coating film. Gravel impact test rating 4B, fragment specifications 1-3mm, the number of 50-74, proved that the curing method obtained a better coating toughness, with excellent resistance to gravel strike. There is no change in the coating surface after the water resistance test, which proves that the coating film anti-water molecule penetration ability obtained by the curing method is strong, and the better protection of the substation can be realized.
4.4 Material Performance Results
Each of the three process hubs took root spokes for pull strength (Rp0.2), yield strength (Rm), elongation (A) testing.
the data is averaged, the results are found in Fig. 3.
Fig. 4 Compared material performance under three processes
As shown in Fig. 4, after the heat wind curing, the pull strength and yield strength of the hub are improved, respectively, 37MPa, 16Mpa. Similar to the trend of hot air curing, the pull strength and yield strength of the infrared cured hub increased by 44Mpa and 18MPa, respectively. After coating baking curing, the substation elongation decreased, the heat air curing process decreased by 2.1% and the infrared curing process decreased by 2.2%. Compared with hot air curing, the infrared curing process has less effect on the performance of hub material, and increases the pull strength and yield strength of aluminum alloy, which proves that the process is suitable for hub coating drying and curing. 5 Energy consumption analysis
5.1 natural gas consumption
based on the actual energy consumption of the powder oven hot air cycle curing provided by a hub production workshop and the energy consumption of the infrared radiation curing oven, the results are shown as Tab. 3 heat.
Tab. 3 Thermal air curing and infrared curing energy consumption comparison
To achieve complete powder curing, hot air curing time is 38min, infrared curing is estimated at 12min, the line length required for thermal wind curing is 106m, infrared curing is 33m long, can be Save about 69% of the floor space, thermal wind-cured natural gas consumption of about 106m
3
/h, infrared cured natural gas consumption of about 84m
3
/h, can save about 21% of natural gas consumption, if Daily by operating 24 hours, 30 days per month, natural gas prices at 4 yuan / m
3
calculation, each year each powder oven due to gas savings can obtain the economic benefits as follows:
gas savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 x 4 x 760320 yuan / year
5.2 floor area analysis
hot air curing oven effective length of about 106m, infrared curing oven effective length of about 33m, can save about 69% The length of the thermal air-cured cooling segment is about 47m, the infrared curing is much lower than the lacquer film temperature, and the infrared cured oven cooling segment can save about 50% of the space and the length is about 24m. The effective total length of the hot air curing oven is about 153m, the effective total length of the infrared curing oven is about 57m, and the infrared radiation curing can save about 63% of the floor space. 6 Conclusion
(1) Catalytic combustion infrared radiation curing can obtain excellent-looking hub products.
(2) catalytic combustion infrared radiation curing method for transparent powder full curing.
(3) catalytic combustion infrared radiation curing obtained by the coating film initial adhesion, CASS, gravel impact resistance, water resistance tests are to meet the performance index requirements.
(4) catalytic combustion infrared radiation curing hub elongation is equivalent to hot air curing, pull strength and yield strength is better than hot air curing process.
(5) Compared to hot air cycle curing, catalytic combustion infrared radiation curing can save natural gas costs of 760,000 yuan / year, saving 63% of the floor space
Du Yunpeng Zhang Shengchao Leiyuan (CITIC Decca Co., Ltd., Hebei, Qinhuangdao, 066011)