Chemical container surface spraying process

Abstract

The invention provides a chemical container surface spraying process which comprises the following steps: cleaning the surface to remove various pollutants on the surface of a sprayed chemical container, especially grease, dirt, oxide skin, rust and corrosives; surface sand blasting is carried out, dry, pure and excellent quartz sand is adopted for construction according to the specified sequence, sand blasting treatment is carried out on the surface of the chemical container, and particularly, oxide skin and attachments hindering combination of a coating are not allowed to exist at the root welding position of the chemical container; impurities need to be cleaned up by blowing sand and dust on the surface of a workpiece layer by layer from top to bottom, the sand and dust on the sprayed surface need to be cleaned up, a coating is sprayed, spraying equipment is adopted for coating spraying, quality acceptance and special quality inspection personnel are adopted for inspection and acceptance, the problem that the surface of a container in the chemical industry is prone to corrosion is solved, and an existing anti-corrosion layer is short in service life and low in cost. The process is sprayed on the surface of the chemical container, the anticorrosive coating is not easy to fall off, the bonding strength is high, the service life of the container is long, and the cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of container anti-corrosion layer spraying, and in particular to a chemical container surface spraying process. Background Art

[0002] Nowadays, the surface of metal containers in the chemical industry is easily corroded by chemical products. Over time, the lifespan of the metal containers is greatly shortened, affecting the service life, and posing a great safety hazard. Currently, most people directly spray anti-corrosion substances on the surface of the containers, but the anti-corrosion effect is poor, resulting in a short service life of the containers. In view of this, overcoming the defects of the above-mentioned prior art is a problem that needs to be urgently solved in this technical field. Summary of the invention

[0003] In order to make up for the above shortcomings, the present invention provides a chemical container surface spraying process, which aims to improve the current chemical container surface anti-corrosion effect is poor, resulting in a short service life of the container.

[0004] The present invention is implemented in this way: The present invention provides a chemical container surface spraying process, which adopts the following process steps: S1. Clean the surface Remove various pollutants from the surface of sprayed chemical containers, especially grease, dirt, scale, rust and corrosion; S2, surface sandblasting Use dry, pure and high-quality quartz sand to sandblast the surface of the chemical container in the prescribed order. Especially at the root welding part of the chemical container, no oxide scale and attachments that hinder the bonding of the coating are allowed to exist; S3. Clean up impurities The sand and dust on the surface of the workpiece should be blown away layer by layer from top to bottom, and the sand and dust on the spraying surface should be cleaned up; S4, coating spraying Use spraying equipment to spray layers. When spraying, use a tic-tac-toe spraying method, layered and zoned. After the local area reaches the process design thickness, move to other areas. When spraying, follow the principle of "spray up and down, move to the right, and complete in pieces", that is, spray from top to bottom at a certain spray gun speed, and then move to the right one position each time from bottom to top. When moving to the right about 1m, return to spray, and do this 8-12 times to avoid leakage, uneven spraying or overheating, and ensure the quality of the coating; S5. Quality Acceptance Specialized quality inspectors conduct inspection and acceptance.

[0005] In one embodiment of the present invention, the surface cleanliness of the chemical container after sandblasting reaches Sa3 level, and the roughness reaches Rz>60~80μm.

[0006] In one embodiment of the present invention, the sandblasting abrasive material is quartz sand with a particle size of 2.0-4.0 mm and an impurity and fine powder content of less than 5%.

[0007] In one embodiment of the present invention, the surface of the chemical container that has passed the inspection after sandblasting is metal sprayed in time to prevent secondary pollution. The interval between the chemical container after sandblasting and the metal spraying operation shall not exceed 6 hours. When the ambient humidity is greater than 85%, the interval between the chemical container after sandblasting and the metal spraying shall not exceed 2 hours and the metal spraying operation must be carried out.

[0008] In one embodiment of the present invention, the spraying equipment is selected from: a supersonic arc spraying machine.

[0009] In an embodiment of the present invention, the spraying material is an alloy material, and the alloy material is composed of nickel, chromium and manganese.

[0010] The beneficial effects of the present invention are: Solve the problem that the surface of containers in the chemical industry is easily corroded. The existing anti-corrosion layer has a short service life. This process sprays the anti-corrosion layer on the surface of the chemical container. The anti-corrosion layer is not easy to fall off, has high bonding strength, and has a long service life of the container, saving costs. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0013] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0014] The present invention provides a chemical container surface spraying process, which adopts the following process steps, including: Surface cleaning: remove all kinds of pollutants on the sprayed surface, especially grease, dirt, scale, rust and corrosion. The cleanliness of the working surface reaches Sa3.0 level specified in GB8923-88 "Rust level and rust removal level of steel surface before painting".

[0015] Surface roughness: The combination of thermal spray coating and substrate is mainly mechanical, which requires that the substrate pretreatment should not only remove oil and rust, but also roughen the surface, and the surface should have a certain degree of roughness. The surface roughness should reach Rz>60~80μm as specified in GB11373-89 "General Rules for Surface Pretreatment of Thermal Sprayed Metal Parts", and will not cause any damage to the tower wall thickness.

[0016] The purpose of sandblasting is to increase the contact area between the sprayed layer and the substrate, improve the bonding degree of the coating, increase the mutual embedding and bite between the coating material and the substrate surface, play the role of "anchor hook", and improve the adhesion between the coating and the substrate.

[0017] Activated surface: Sandblasting provides active surface capabilities for spraying: such as lattice defects, plastic deformation, and a certain stress state, which is beneficial to increase the adhesion between the spray particles and the substrate surface and improve the micrometallurgical bonding ability between the spray particles and the substrate.

[0018] Sandblasting causes the surface of the workpiece to form a certain residual compressive stress after repeated impact of sand particles. Although the stress value is extremely small, it is beneficial to improve the bonding strength of the coating for the loose workpiece during the spraying process. It can also improve the fatigue strength of the workpiece. Sandblasting can remove organic pollutants and oxide layers on the surface of the workpiece, increase the plastic deformation of the metal surface grains and cause lattice defects, so that the substrate surface is in a state where chemical reactions are easy to occur, which is conducive to the physical and chemical bonding strength between the sprayed particles and the substrate surface.

[0019] Explanation of damage to tower wall thickness caused by sandblasting: Sandblasting is only to remove dirt on the surface. The thickness of the tower wall removed by sandblasting is ≤15μm, which is the thinnest and will not affect the thickness of the entire tower wall. Secondly, sandblasting will not cause tearing and blowing damage to the tower wall. Thirdly, sandblasting is carried out evenly, and the thickness loss of the entire surface is consistent. In summary, sandblasting is only the most effective way to dry, clean and activate the surface of the furnace tube and improve the bonding strength of the coating, and will not damage the thickness of the tower wall. Therefore, it is extremely necessary to sandblast the workpiece before spraying. Moreover, the workpiece after sandblasting should be sprayed as soon as possible. The shorter the time, the better the surface activation effect (arc spraying must be carried out within 2 to 4 hours after sandblasting) and the higher the coating quality.

[0020] Compressed air quality requirements: Use on-site air source or self-provided air compressor, exhaust flow rate ≥ 6m3 / min, working pressure 0.55~0.8Mpa.

[0021] Operation method: Sandblasting distance is 150-200 mm, and the sandblasting angle is 60-90° to the substrate.

[0022] Operation sequence and inspection requirements: First spray quartz sand twice to completely remove rust, oxide scale, coke, etc. on the surface of the steel and reveal a gray-white metallic luster. The role of spraying quartz sand is only to roughen the surface of the substrate to achieve the surface roughness required for spraying without causing any damage to the thickness of the tower wall. Use a roughness sample block for control inspection. After sandblasting, the tower wall surface should be dry, free of dust, oil, oxide scale, rust and other debris, and the surface of the substrate should have a homogeneous gray-white metallic appearance.

[0023] Before spraying, the pre-treated surface should be checked: if rust or unqualified parts are found, they should be re-treated. If qualified, the tower wall should be measured for the first time with a thickness gauge δ1. If serious thinning or cracks are found, Party A should be asked to replace the pipe or reinforce it. Spraying must be carried out within 30 minutes after sandblasting is completed.

[0024] Sandblasting and rust removal. Sandblasting shall comply with GB11373-89 standard, requiring the use of dry, pure and high-quality quartz sand in the specified order. The surface cleanliness of the furnace tube after sandblasting shall reach Sa3 level, and the roughness shall reach Rz>60~80μm. In particular, no oxide scale and attachments that hinder the bonding of the coating are allowed to exist at the welding part of the root of the furnace tube. The surface cleanliness shall meet the Sa3 level requirements specified in "Surface Rust Level and Rust Removal Level of Steel Materials Before Coating" GB / T8923-1988; the surface roughness shall reach Rz60~80μm; the sandblasting abrasive shall be quartz sand with a particle size of 2.0-4.0mm and sharp edges, and the sandblasting abrasive must be kept clean and dry; the compressed air used for sandblasting must be clean, dry, oil-free and water-free; the pressure shall be 0.5~0. 6MPa, flow rate 5-6m3 / min; Sandblasting equipment is a pressure vessel and should be inspected regularly, and the air pipe and sandblasting gun head for conveying sand should be replaced regularly; The nozzle of the sandblasting gun is prohibited from being aimed at one part for a long time or at a close distance to avoid damage to the furnace tube; The sandblasting gun and the pipeline are kept at an angle of 60-90° and the distance is 150-200mm; Multiple people are sandblasting at the same time in the same space, and the distance should be no less than 5 meters; The distance between the spray gun and the substrate is 150-200mm; The arc flame flow of the spray gun is adjusted to a stable state with uniform scattering and no broken arc; The spray gun sprays vertically along the axis of the furnace tube at a uniform speed, and the moving speed is 0.3-0.5m / s; Reciprocating spraying is completed 9-10 times to complete a spraying cycle; The substrate temperature is monitored by a thermometer and does not exceed 100℃; After the coating is accepted, the hole is sealed according to the process requirements. The diameter of the quartz sand used for sandblasting is required to be 2.0-4.0mm, the moisture content is less than 1%, and the impurity and fine powder content is less than 5%.

[0025] After sandblasting, the furnace tube surface that has passed the inspection shall be metal sprayed in time to prevent secondary pollution. The interval between the furnace tube after sandblasting and metal spraying shall not exceed 6 hours. The interval between the furnace tube after sandblasting and metal spraying in an environmental humidity greater than 85% shall not exceed 2 hours. Metal spraying must be carried out. After the sandblasting operation is completed, the sand and dust on the surface of the workpiece should be blown away layer by layer from top to bottom, and the sand and dust on the spraying surface should be cleaned.

[0026] When making the coating, the surface temperature of the tower wall should be controlled to be ≤150℃ during the spraying process. The thickness of the spraying layer should be completed in multiple times. The surface of the spraying layer should be flat. After each construction unit is completed, a thickness measurement and other project tests should be carried out. For the spraying layer that does not meet the requirements, it should be repaired or re-sprayed immediately. The quality of the wire used for spraying meets the standards and the wire is required to provide a material report. During the spraying process, the tower wall base material does not undergo any material changes, no stress is generated, and the tower wall does not deform. The alloy coating layer is tightly combined with the tower wall base material, does not layer or fall off at high temperatures, has good heat conduction, a smooth surface, and no dust. After spraying, the tower wall has good wear resistance, high-speed erosion resistance, and extreme cold and heat resistance. The service life is more than 1 year. The temperature of the sprayed alloy layer can reach 300℃-400℃. The coating does not oxidize, resist high temperature corrosion, and does not delaminate, and the material does not change.

[0027] When spraying, the principle of "spraying up and down, moving to the right, and completing in pieces" should be followed, that is, spray from top to bottom at a certain speed, and then from bottom to top, moving one position to the right each time. When it moves to the right about 1m, return to spray, and do this 8-12 times to avoid uneven spraying or overheating and ensure the quality of the coating.

[0028] The supersonic arc spraying system consists of power supply, wire feeder, supersonic arc spray gun, air compressor, gas tank, oil-water separator and other equipment. This spraying technology uses an arc burning at the end of the wire to melt the wire that is evenly fed in. The supersonic airflow accelerated by the Laval nozzle atomizes the melted wire into fine and evenly distributed particles, which are sprayed onto the workpiece to form a coating. The particle speed reaches more than 450m / s, and the coating porosity can be controlled within 0.9%. At the same time, the bonding strength between the coating and the substrate has also been significantly improved. The molten particles are mainly combined with the substrate in mechanical, physical and metallurgical ways, and the bonding strength can reach more than 60MPa. Compared with ordinary arc spraying and flame spraying, supersonic arc spraying has higher particle flight speed, stronger bonding strength, lower porosity, high coating uniformity, good density, and the temperature of the sprayed particles is less than 80℃ when it reaches the surface of the workpiece, so the workpiece will not deform, and a high-quality coating can be obtained.

[0029] Spraying process parameters: Arc voltage: 32~34V Arc current: 160-200A Atomizing air pressure: 0.5-0.6MPa.

[0030] Spraying distance: 150~200mm Metal coating thickness: coating thickness 0.6-0.8mm (partially thickened to 1mm) Spraying method: adopt the tic-tac-toe spraying method, layered and zoned operation, spray the local area to reach the process design thickness before moving to other areas to ensure the uniform thickness and bonding strength of the spray layer to prevent leakage. After spraying, the coating quality inspection should be carried out and the thickness δ2 should be measured. If δ2-δ1 is not less than 0.5mm, it is qualified and can enter the next process. Otherwise, the unqualified parts should be sprayed again.

[0031] When spraying the wear-resistant layer: a tic-tac-toe spraying method is also used, with layered and zoned operations. After the local area is sprayed to reach the process design thickness, it is moved to other areas to ensure the uniform thickness and bonding strength of the spray layer and prevent missed spraying.

[0032] Operation precautions: Work in blocks, spray the local area until it reaches the designed thickness before moving to other areas, and set identification marks at the overlapping parts. During operation, the interlayer temperature shall not be higher than 100℃.

[0033] The wire feeding reel and wire feeding conditions shall be supervised by a dedicated person to ensure smooth wire feeding and prevent the wire from being "knotted". At the same time, absolute insulation between the two wires must be ensured to avoid short circuit. Before spraying, a test spray should be performed on the test plate to adjust the voltage, current, wire feeding speed, and compressed air flow. The flexible joints and hose joints of the air path should be checked for leaks. If special sites such as unstable wire feeding, unstable arc burning, and severe air leakage are found, they should be checked and adjusted in time. The main circuit should be disconnected when adjusting the voltage to avoid damaging the main spray power supply (the conductive nozzle burned during the spraying process should be replaced in time, and the conductive nozzle with excessive processing accuracy is prohibited from use).

[0034] If the wire feeding is unstable, the fuse is blown, or the arc is intermittent during the spraying process, you should first check the use of the conductive nozzle, and then check whether the wire guide tube is firmly installed. If it is loose, tighten it in time.

[0035] The selection of spraying materials and the use of alloy materials for wires are the key to ensuring the life of the coating. The main components of the materials are nickel, chromium, manganese and other trace elements. The wire with a diameter of 2mm is made by special technology (for large-area supersonic arc spraying). Ni, Cr, and Mn have good ductility and acid and alkali resistance, and are used as carriers of hard points. The hard points are embedded in the carrier and evenly distributed. Acid and alkali resistance requirements, the coating works in high-temperature furnace gas containing caustic soda, alloy materials, and the coating has good acid and alkali resistance. Use austenitic stainless steel spray wire 304 as the base and austenitic stainless steel spray wire 316L as the cover spray working layer. The coating surface is required to be flat, smooth, dense, uniform, and well combined with the substrate, without defects such as peeling, cracking, pockmarks, and falling off. The transition zone has a smooth transition with the parent material without steps, the substrate does not deform, and the porosity is less than 0.9%. The coating is acid and alkali resistant, as proven by inspection and has been identified as qualified by the quality and technical supervision departments at or above the autonomous region level.

[0036] From the clean air path: dry and clean compressed air can be obtained through the oil-water separator. Spraying equipment selection: YB500 supersonic arc spraying machine, special spraying power supply and matching wire feeding device are selected. Spray gun selection: supersonic arc spray gun is selected, and its particle speed reaches more than 450m / s, the coating porosity can be controlled within 0.9%, and the bonding strength between the coating and the substrate is also significantly improved.

[0037] Quality acceptance, the coating has the following required performance; the furnace tube surface is clean: visual inspection of the workpiece surface in the spraying area completely reveals the metallic luster; after sandblasting, use a thickness gauge to measure the thickness of the spraying area at point ∮1; after spraying, use a thickness gauge to measure the thickness of the spray tower wall at point ∮2, and the difference between the sampling points ∮2 and ∮1 is 0.6-0.8mm.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A chemical container surface spraying process, characterized in that The following process steps are used: S1. Clean the surface Remove various pollutants from the surface of sprayed chemical containers, especially grease, dirt, scale, rust and corrosion; S2, surface sandblasting Use dry, pure and high-quality quartz sand to sandblast the surface of the chemical container in the prescribed order. Especially at the root welding part of the chemical container, no oxide scale and attachments that hinder the bonding of the coating are allowed to exist; S3. Clean up impurities The sand and dust on the surface of the workpiece should be blown away layer by layer from top to bottom, and the sand and dust on the spraying surface should be cleaned up; S4, coating spraying Use spraying equipment to spray layers. When spraying, use a tic-tac-toe spraying method, layered and zoned. After the local area reaches the process design thickness, move to other areas. When spraying, follow the principle of "spray up and down, move to the right, and complete in pieces", that is, spray from top to bottom at a certain spray gun speed, and then move to the right one position each time from bottom to top. When moving to the right about 1m, return to spray, and do this 8-12 times to avoid leakage, uneven spraying or overheating, and ensure the quality of the coating; S5. Quality Acceptance Specialized quality inspectors conduct inspection and acceptance.

2. A chemical container surface spraying process according to claim 1, characterized in that: The surface cleanliness of the chemical container after sandblasting reaches Sa3 level, and the roughness reaches Rz>60~80μm.

3. A chemical container surface spraying process according to claim 1, characterized in that: The sand blasting material is quartz sand with a particle size of 2.0-4.0 mm and an impurity and fine powder content of less than 5%.

4. A chemical container surface spraying process according to claim 1, characterized in that: The surface of the chemical container that has passed the inspection after sandblasting shall be metal sprayed in time to prevent secondary pollution. The interval between the chemical container after sandblasting and the metal spraying operation shall not exceed 6 hours. When the ambient humidity is greater than 85%, the interval between the chemical container after sandblasting and the metal spraying shall not exceed 2 hours and metal spraying operation must be carried out.

5. A chemical container surface spraying process according to claim 1, characterized in that: The spraying equipment is selected: a supersonic arc spraying machine.

6. A chemical container surface spraying process according to claim 1, characterized in that: The spraying material is an alloy material, which is composed of nickel, chromium and manganese.