Pickling plate is a high-quality hot-rolled sheet as raw material, after the pickling unit to remove the oxide layer, cutting edge, finishing, surface quality and use of requirements (mainly cold-formed or stamping performance) between the hot-rolled plate and cold-rolled plate between the intermediate products, in order to ensure that the surface quality of the use of the requirements of the premise, so that the user to reduce the purchase cost effectively.
The advantages of pickled plate mainly lie in:
1. good surface quality, due to hot rolled pickled plate to remove the surface of iron oxide, improve the surface quality of steel, easy to weld, oil and paint.
2. High dimensional accuracy, after leveling, it can make certain changes in the plate shape, thus reducing the deviation of unevenness.
3. Improved surface finish , enhanced appearance.
It can be said that pickled plate is a cost-effective product between cold rolled plate and hot rolled plate. In the automobile industry, machinery industry, light industry and home appliances and various shapes of stamping parts have a wide range of applications, such as beams, sub beams, rims, spokes, carriage panels, fans, chemical oil drums, welded pipes, electrical cabinets, fences, ladders and so on. It has a broad market prospect.
Below we introduce the technical process of pickling process and the alternative advantages of laser cleaning.
Metal pickling process
1. Pickling principle:
Is the use of acid solution to remove the oxide skin and rust on the surface of steel and iron a surface process, usually with the pre-film. Generally immersed in a chemical agent solution such as sulfuric acid, etc., to remove oxides and other films on the surface of the metal, electroplating, enameling, rolling and other processes of pre-treatment or intermediate treatment. It is also known as wet cleaning.
Acid cleaning process mainly has impregnation pickling method, spray pickling method and acid paste descaling method.
The acids used are mostly sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, chromic acid, hydrofluoric acid and mixed acids.
2. Process flow:
Metal parts hanging → chemical degreasing (conventional alkaline chemical degreasing or surfactant degreasing) → hot water washing → running water washing → the first step of pickling → running water washing → the second step of pickling → running water washing → transfer to the next process (eg: chemical coloring → recycling → running water washing → hardening → running water washing → closure treatment → running water washing → drying → finished products)
3. Common defects:
Iron oxide indentation: iron oxide indentation is a surface defect formed during the hot rolling rolling process. After pickling, it is often black dots, long stripes pressed in, the surface is rough, generally feel, and sporadic or dense appearances. Often because of the pickling of the heating process, scale removal process, rolling process and other imperfections lead to.
Oxygen spot (surface landscape painting): refers to the hot coil surface iron oxide wash off, leaving a point, line or pit-like shape, the essence of the hot rolled strip surface iron oxide is not removed, by the subsequent rolling is pressed into the substrate, in the pickling after highlighting. The appearance has a certain impact, but does not affect the use of performance.
Yellow spot: localized or the whole plate surface appears yellow stains, can not be covered with oil, affecting the appearance of product quality. Mainly because just out of the pickling tank of the strip steel surface activity is high, rinse water can not play a normal role in rinsing the strip steel, rinsing tank jet beam and nozzle clogging, the angle is not right.
Under pickling: strip steel surface has local iron oxide removal is not clean, not enough, the plate surface is gray-black, fish scale or transverse water ripple-like stains. It is related to the process of acid, mainly because the concentration of acid is not enough, the temperature is not high, the strip running speed is too fast, and the strip can not be immersed in the acid.
Over pickling: the strip steel plate surface tends to be dark black or brownish black, presenting a block, flake black spot or yellow spot, the plate surface is generally rough. The reason is the opposite of under pickling.
4. Environmental pollution:
The main pollutants of the production process are the cleaning wastewater generated by the water washing process at all levels, the dust generated by the sand blasting process, the hydrogen chloride acid mist generated by the pickling process, and the waste tank liquid, waste slag, waste cartridges, empty barrels of raw materials and packaging waste generated by the pickling, rinsing and straightening, phosphating, neutralization and rust prevention process. The main pollutants are hydrogen chloride, pH, SS, COD, BOD₅, ammonia nitrogen, petroleum and so on.
Laser cleaning process
1. Cleaning principle:
With laser energy to penetrate the surface of the object, 100 femtoseconds or so in the material of the electronic absorption of energy vibration in the material surface plasma; 7-10 picoseconds after the electronic energy transfer to the lattice so that the lattice began to vibrate in the 10 picoseconds after the object began to produce macroscopic temperatures, the laser irradiation of the local material began to heat up, melting, vaporization, so as to achieve the purpose of cleaning.
2. cleaning process and effect:
Laser cleaning relative to the acid cleaning method for the process is very simple, without pretreatment, you can simultaneously remove oil, remove the oxide layer and rust removal cleaning work. Simply turn on the equipment out of the light, and then cleaning.
Laser cleaning can reach the highest industrial cleaning grade of Sa3; there is almost no damage to the hardness and hydrophilicity of the material surface. It is more thorough than acid cleaning.
The comparative advantages of laser cleaning
1. Process flow and operational requirements:
Compared with the acid cleaning method of up to a dozen process flow, laser cleaning to achieve the most simplified process, basically one step. Greatly shorten the cleaning time and material loss.
Pickling method has strict requirements on the operation process: the workpiece must be thoroughly degreased to ensure the quality of rust removal; control the concentration of pickling solution, so as not to cause corrosion of the workpiece acid concentration is too high; according to process specifications to control the temperature, so as not to cause corrosion of the workpiece and equipment; pickling tank gradually deposited sludge, sludge heating tubes and other control devices need to be periodically removed; in addition to the other things that need to be paid attention to is the acid pickling time, injection pressure In addition, need to pay attention to the pickling time, spray pressure, operation sputtering, exhaust equipment and so on.
Laser cleaning in the pre-set parameters can be realized after the foolproof operation or even automated unmanned operation.
2. Cleaning effect and environmental pollution:
Laser cleaning in addition to stronger cleaning effect, there is an advantage of greater fault tolerance:
Acid cleaning method often occurs due to errors in the operation of the oxygen spot yellow spot, red and black, etc., high scrap rate.
Water drop laser experiments have proved that laser cleaning, even if oversaturated cleaning still has a strong metal luster, and does not produce hydroxide and other pollutants, the next step of welding and other processing methods will not have an impact.
Laser cleaning the whole process will not have waste liquid waste residue and other environmental pollution, is the most green cleaning method.
3. Unit cost and conversion cost
Acid cleaning method requires chemicals as consumables, so the unit cost is composed of equipment depreciation + consumables costs; laser cleaning in addition to the purchase of equipment does not require other consumables. The unit cost is the depreciation of the equipment; therefore, the larger the scale of cleaning, the longer the years, the lower the unit cost of laser cleaning.
The composition of the pickling production line requires a complex process, the ratio of pickling agent for different metal materials is not the same, so the conversion of the production line will require a larger conversion costs, the short-term cleaning of a single metal material, can not be flexible changes.
Laser cleaning there is no conversion costs: the same cleaning machine to switch the software parameters can be achieved one minute cleaning steel, the next minute cleaning aluminum alloy effect. Convenient for enterprises to implement JIT flexible production.
Translated with www.DeepL.com/Translator (free version)
