1. Surface treatment of steel structure: the rust removal and roughening of thermal spraying metal ladder coating anti-corrosion process is the same as that of zinc spraying and stainless steel coating. The air compressor first provides sandblasting power. Under the action of compressed air, the screened quartz sand with edges and corners is mixed with sand and gas in sand bucket and rubber hose, and then the workpiece surface is impacted at high speed to remove rust and other oxides on the substrate surface, so as to make the substrate surface uneven.
2. Thermal spraying zinc: main equipment includes: compressed air system, oxygen and acetylene system, metal gas spray gun, rubber hose and other equipment. Its principle is: with the compressed air in the spray gun as the driving force, driven by the driving device, the zinc wire passes through the nozzle and is heated by the oxygen acetylene flame to become a molten body, which is atomized into particles by the compressed air and sprayed onto the workpiece to form a thermal spraying zinc protective layer. Due to the unevenness of the substrate surface after sand blasting, the metal coating after heat dissipation and contraction can be firmly attached to the workpiece surface.
3. Spraying stainless steel: the main equipment is the same as zinc spraying, but the metal gas spray gun should be medium speed gun, which is generally improved on the basis of high-speed gun, and can be used after replacing some parts. The working principle is the same as above, but the melting points of zinc and stainless steel are different, so the dosage of aerobic acetylene flame should be adjusted.
4. Apply epoxy micaceous iron oxide, sealing primer and AC-5 chlorinated rubber aluminum powder finish. Coating method: manual brushing combined with air spraying. It is required to be free of brush marks, blisters, sagging and missed spraying, and its appearance is silver gray, neat, symmetrical and consistent.
Spraying effect of thermal spraying metal ladder coating
The bottom layer of ladder coating - the zinc layer has fine particles, uniform coating, small pores, good compactness, and the thickness of the zinc layer meets the design requirements. Since the thickness of the zinc layer is only half of the original, the adhesion is strong, and the stainless steel coating is covered on it, which is grayish black, coarse particles, large pores, but hard and wear-resistant. Since the thickness of the superimposed coating is only half of the original, the adhesion is also good, It has a good protective effect on the zinc layer, and then it is sealed with epoxy micaceous iron paint, and the chlorinated rubber aluminum powder paint is used as the finish paint, which has good waterproof and anti-seepage properties. After the inspection of each process by Shanghai Survey and Design Institute of the Ministry of Water Resources and Jiangsu Quality Inspection Center, the thermal spraying metal ladder coating is of good quality and meets the design requirements.
Special processing methods of thermal spraying (welding) materials
1、 Electrolytic grinding method: grinding of high hardness thermal spraying (welding) materials can achieve good results only when diamond or cubic boron nitride grinding wheels are used, but its productivity is not high. The productivity can be greatly improved by electrolytic grinding, especially for inner hole grinding. Electrolytic grinding is to apply direct current between the workpiece and the grinding wheel. Under the action of electrolyte, the metal surface to be machined will produce electrolytic action (electrochemical action). With the alternating action of electrolytic action and mechanical grinding of the grinding wheel, the required dimensional accuracy and surface roughness will be achieved. The grinding wheel used for electrolytic grinding is diamond bronze bond conductive grinding wheel, and the thermal spraying (welding) material must be conductive.
Electrolyte is an important factor affecting productivity and machining quality in electrolytic grinding process. Electrolyte with good effect for electrolytic grinding of thermal spraying (welding) materials: disodium hydrogen phosphate 3%~5%, sodium nitrite 2%, potassium nitrate 2%, water 91%~93%, pH 8~9, non rusting machine tool. The sodium nitrite and potassium nitrate of this electrolyte play the role of conduction and oxidation. After the disodium hydrogen phosphate is ionized in the aqueous solution, the solution becomes weakly alkaline (pH8-9), which is conducive to the dissolution of oxides and accelerates the electrolysis process, thus obtaining large current efficiency and improving the processing efficiency.
The current and voltage parameters of electrolytic grinding thermal spraying (welding) materials are: during rough machining, the voltage is 10-15V, and the current density is 20-30A/c ㎡; During finishing, the voltage is 6~8V and the current density is 10~15A/c ㎡. Electrolytic grinding thermal spraying (welding) materials have the following characteristics: 1. The machined surface quality is good. The dimensional accuracy of the inner hole can reach IT7, the surface roughness Ra=1.25 μ m, and the machined surface is not easy to produce cracks and burns.
2. High productivity. Large grinding amount can be used, especially the grinding depth (radial feed) can be much larger than the general grinding, and the productivity can be 3~5 times higher than the general grinding.
3. Good economy. The abrasion of the grinding wheel is small, and the abrasion ratio when grinding the inner hole is about 400.
4. Wide processing range and strong adaptability. It can grind all kinds of conductive high hardness thermal spraying (welding) materials, and it is also easy to achieve for various profiles (such as gears).
2、 Ultrasonic vibration turning method: ultrasonic vibration turning is a processing method that enables the tool to generate ultrasonic vibration along the cutting speed direction (general vibration frequency 20kHz, amplitude a=10~30 μ m) for turning. The ultrasonic vibration turning tool edge and the workpiece form a separate cutting, that is, the tool only completes a cutting and separation in a very short time in each vibration, so its cutting force and cutting heat are very small, which can obtain high dimensional accuracy and surface quality. Ultrasonic vibration turning is a new technology that is easy to obtain high precision and high surface quality. The tool amplitude has a great impact on the surface roughness. When the amplitude increases, the surface roughness Rz value decreases, but when the amplitude increases to a certain value, the reduction of Rz value tends to ease.
The Rz of Ni60 spray welding layer can reach 2.3 μ m by ultrasonic vibration turning with YD05 tool, the Ra of Al2O3 ceramic coating can reach 2.0 ～ 1.5 μ m by cubic boron nitride turning, and the turning amount is ν c=4.8m/min, f=0.1mm/r，ap=0.05mm， The vibration frequency is 20kHz, and the amplitude is a=15 μ m. Ultrasonic vibration turning of high hardness thermal spraying (welding) materials can obtain relatively high dimensional accuracy and surface quality, which is more productive and economical than grinding, but not as productive as electrolytic grinding. Ultrasonic vibration turning is especially suitable for machining non conductive electro thermal spraying (welding) materials (such as ceramic coatings) that cannot be machined by electrolytic grinding.
Guangzhou Tuoshen Surface Treatment Co., Ltd., the spraying manufacturer, is preferred for purchasing spraying, Spray processing Factory, trustworthy
