Views: 17 Author: Leapion Publish Time: 08-05-2022 Origin: https://www.leapion.com
A pickling board is an intermediate product with the high-quality hot-rolled sheet as raw material, after removal of the oxide layer, trimming, and finishing by the pickling unit, the surface quality, and usage requirements are between those of a hot-rolled sheet and cold-rolled sheet. Under the premise of quality use requirements, users can effectively reduce procurement costs.
(1) The surface quality is good because the surface iron oxide scale is removed from the hot-rolled pickling plate, which improves the surface quality of the steel and facilitates welding, oiling, and painting.
(2) High dimensional accuracy, after flattening, the plate shape can be changed to a certain extent, thereby reducing the deviation of unevenness.
(3) Improves surface finish and enhances appearance.
Pickling boards have a wide range of applications
It can be said that the pickling board is a high cost-effective product between the cold-rolled sheet and hot-rolled sheet. It is widely used in the automotive industry, machinery industry, light industrial appliances, and stamping parts of various shapes, such as automobile beams, automobile sub-beams, rims, wheel spokes, carriage panels, fans, chemical oil drums, welded pipes, electrical cabinets, Fences, iron ladders, etc. It has broad market prospects.
Below we will introduce the technical process of the pickling process and the alternative advantages of laser cleaning.
It is a surface process that uses an acid solution to remove oxide scale and rust on the surface of the steel usually carried out together with pre-filming. Generally, the workpiece is immersed in a chemical solution such as sulfuric acid to remove the oxide film on the metal surface, which is the pre-treatment or intermediate treatment of electroplating, enamel, rolling, and other processes. Also known as wet cleaning.
The pickling process mainly includes the dipping pickling method, spray pickling method, and acid paste rust removal method.
The acids used are mostly sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, chromic acid, hydrofluoric acid, and mixed acids.
Hanging on metal parts→chemical degreasing (conventional alkaline chemical degreasing or surfactant degreasing)→hot water washing→running water washing→first pickling→running water washing→second pickling→running water washing→transfer to the bottom process (such as chemical coloring→recycling→running water washing→hardening treatment→running water washing→sealing treatment→running water washing→drying→finished product)
Iron oxide scale intrusion: Iron oxide scale intrusion is a surface defect formed during hot rolling. After pickling, it is often pressed in the shape of black dots and strips, the surface is rough, generally has a hand feel, and appears sporadically or intensively. It is often caused by an imperfect heating process, descaling process, and rolling process of pickling.
Oxygen spot (surface landscape painting): refers to the dot-like, linear, or pit-like appearance left after the iron oxide scale on the surface of the hot-rolled steel is washed off. The rolling is pressed into the matrix, which is highlighted after pickling. It has a certain effect on appearance but does not affect performance.
Macular: yellow spots appear on the part or the whole board surface, which cannot be covered after oiling, which affects the quality and appearance of the product. The main reason is that the surface activity of the strip just out of the pickling tank is high, the rinsing water fails to wash the strip normally, and the spray beam and nozzle of the rinse tank are blocked, and the angles are not equal.
Under-pickling: The surface of the strip steel has local iron oxide scales that are not cleanly and insufficiently removed, and the plate surface is gray-black, with fish scales or horizontal water ripples. It is related to the process of the acid solution, mainly due to the insufficient concentration of the acid solution, the low temperature, the running speed of the strip steel is too fast, and the strip steel cannot be immersed in the acid solution.
Over-pickling: The surface of the strip steel is often dark black or brownish-black, showing block, flaky black spots, or macular, and the surface of the plate is generally rough. The reason is the opposite of under pickling.
The iron oxide scale is pressed in due to an improper pickling process
(4) Environmental pollution:
The main pollutants in the production process are the cleaning wastewater produced by the water washing process at all levels, the dust produced by the sandblasting process, the hydrogen chloride acid mist produced by the pickling process, and the waste produced by the pickling, rinsing, phosphating, neutralization and rust prevention processes. Tank liquid, waste residue, waste filter element, raw material empty barrels and packaging waste, etc. The main pollutants are hydrogen chloride, pH, SS, COD, BOD, ammonia nitrogen, petroleum, etc.
Using laser energy to penetrate the surface of the object, the electrons in the material absorb the energy vibration for about 100 femtoseconds, and generate plasma on the surface of the material; after 7-10 picoseconds, the electron energy is transferred to the lattice and the lattice starts to vibrate, and after 10 picoseconds The object begins to generate macroscopic temperature, and the local material irradiated by the laser begins to heat up, melt, and vaporize, to achieve the purpose of cleaning.
Principle of laser cleaning
Compared with the pickling method, laser cleaning has a very simple process and does not require pretreatment. Just turn on the device to let out the light, then clean it.
Laser cleaning can reach the highest industrial cleaning level of Sa3; almost no damage to the hardness, hydrophilicity, and hydrophobicity of the material surface. More thorough than pickling.
Laser cleaning parameter record
Compared with the pickling method with more than a dozen processes, laser cleaning has achieved the most simplified process and achieved one step. Greatly shortens cleaning time and material loss.
The pickling method has strict requirements for the operation process: the workpiece must be completely degreased to ensure the quality of rust removal; the concentration of pickling solution is controlled to prevent the workpiece from being corroded due to excessive acid concentration; the temperature is controlled according to the process specifications to avoid damage to the workpiece and The equipment causes corrosion; the pickling tank gradually deposits sludge, which blocks the heating pipe and other control devices, and needs to be removed regularly; in addition, it is necessary to pay attention to the pickling time, injection pressure, operation sputtering, exhaust equipment, etc.
Laser cleaning can realize fool-like operation or even automatic unmanned operation after setting parameters in the early stage.
(2) Cleaning effect and environmental pollution:
In addition to the stronger cleaning effect, laser cleaning has the advantage of greater fault tolerance:
Oxygen macular, redness, and blackening often occur due to mistakes in the operation of the pickling method, and the rejection rate is high.
Experiments have shown that even if the laser cleaning is supersaturated, it still has a strong metallic luster, and does not produce hydroxide and other pollutants, which will not affect the next processing methods such as welding.
There will be no environmental pollution such as waste liquid and slag in the whole process of laser cleaning, which is the most environmentally friendly cleaning method.
The effect of the laser cleaning experiment
The pickling method requires chemicals as consumables, so the unit cost consists of equipment depreciation + consumables cost;
Laser cleaning requires no consumables other than purchasing equipment. The unit cost is the depreciation of the equipment;
Therefore, the larger the cleaning scale and the longer the years, the lower the unit cost of laser cleaning.
The composition of the pickling production line requires complex processes, and the ratio of pickling agents for different metal materials is not the same. Therefore, the conversion production line requires a large conversion cost, and the metal materials to be cleaned in a short period are single and cannot be flexibly changed.
There is no conversion cost for laser cleaning: after switching the software parameters of the same cleaning machine, the effect of cleaning the steel plate one minute and the aluminum alloy the next minute can be achieved. It is convenient for enterprises to implement JIT flexible production.
With the emphasis on environmental protection by governments around the world in the past two years, the requirements for structural transformation and upgrading of the manufacturing industry have become more and more stringent. Environmental rating reports for pickling production lines are also becoming increasingly stringent, and the profit margins of related companies are getting thinner and thinner. In turn, support for high-tech has increased. The overall environment is more favorable for laser cleaning.
The pickling board has a wide range and in-depth applications in manufacturing production and plays a positive role in industrial support. However, with the upgrading of the manufacturing industry, capacity optimization and structural adjustment are also being carried out slowly. Laser cleaning has a considerable possibility to replace pickling in the future and become a more environmentally friendly cleaning method.
