Trolley annealing furnace with some new processing good welding performance of high strength steel, such as super martensite, limitation of martensite and ferrite stainless steel adding Cu, Nb element Cr system such as stainless steel, neutral salt electrolytic pickling plus nitric acid electrolytic technology already can not adapt to the new steel pickling process and recent development in a neutral salt electrolytic pickling + nitric acid electrolytic adding alkali electrolysis process on the basis of alone or mix acid such as nitric acid, hydrofluoric acid, sulfuric acid and hydrochloric acid. Nitric acid is an oxidant and can promote passivation of stainless steel, but it does not descalate when used alone. Hydrofluoric acid is highly toxic, which not only corrodes iron scales, but also corrodes base metals, making the surface rough. Therefore, these two acids can not act alone, and the use of their mixture effect is preferred, a short period of time to obtain a good surface, the risk of pitting is small, so no matter what kind of steel, most use this kind of mixed acid.
The pickling mechanism in mixed acid solution is complex, and it is generally believed that HF ACTS as a medium to promote the reaction between HNO3 and oxide layer. Sulfuric acid in higher temperature pickling effect is good, but low temperature is very poor, so generally only used in the following two cases: one is to improve the descaling of chromium steel hot rolling roll, sometimes set up thermal sulfuric acid tank, and nitric acid, hydrofluoric acid mixed acid combination use; Second, in the cold rolling deacidification line, in order to neutralize the alkali from the strip after alkali bath treatment, set up a sulfur trough between the salt bath water bath to improve the effectiveness of the pickling trough behind. When using sulfuric acid pickling, the key is to master the acid temperature. Stainless steel pickling generally does not use hydrochloric acid. Because hydrochloric acid not only erode scale, also erode metal matrix, even if use, also should mix with nitric acid use, but this kind mixes acid metal matrix to still have erosive sex, bring about metal surface to be rough, because this general stainless steel factory is used rarely.
Acid leaching (also known as electropickling)
Electrolytic pickling is a method of accelerating descaling under the condition that it is difficult to remove completely by acid pickling method only. The characteristic of this method is: due to the electrochemical action, the surface uniform gloss is good. Electrolytic pickling is usually used in nitric acid electrolysis and sulfuric acid electrolysis two methods, with nitric acid electrolysis used more. When nitric acid is used alone as acid leaching solution, it does not have the effect of descaling. However, when the current is generated through the electrode (silicon cast iron), the oxidation film can be ionized due to the electrochemical effect, so pickling can be carried out. However, due to low corrosion and small phosphorus removal ability, it is generally not used alone. The descaling ability of sulfuric acid electrolysis is still poor. In addition to the electrolytic device, this method also needs to recover the waste acid, sulfur oxide device in the exhaust gas, so the equipment cost is high. Continuous pickling line is a combination of various pickling methods. Strip pickling is a continuous process in which various pickling methods, including pretreatment, are combined in different ways. The combination mode depends on the steel type, strip surface state and equipment condition.
The pickling equipment of trolley type annealing furnace and the pickling process control pickling equipment can be divided into three types: acid storage equipment, pickling equipment, final washing equipment and waste acid treatment equipment. This paper mainly introduces pickling equipment. Pickling equipment by acid tank, scrubbing machine, dryer and other ancillary equipment. According to the type of acid, acid tank sulfuric acid tank, hydrofluoric acid nitrate mixed acid tank, nitric acid electrolytic cell, etc. Linings vary according to the properties of the acid. The acid tank is generally made of steel plate, lined with acid-resistant board (such as polyethylene resin board), and then built acid-resistant brick (sulfuric acid and nitric acid electrolytic ceramic tile, nitric acid-hydrofluoric acid mixed with carbon brick). The acid is added from the upper part of the tank through a metering tank. There are two ways for acid heating of trolley annealing furnace: one is direct heating of steam into the tank; One is indirect heating with a heat exchanger. Indirect heating can be divided into two ways: one is to heat in the tank, the other is to set a heat exchanger around the tank, so that the acid liquid circulates between the tank and the heat exchanger.
On 2018-08-08 11:45:46
