In the production process of seamless steel pipe, pickling and passivation process is one of the key links. It can not only improve the surface quality of steel pipe, but also enhance the corrosion resistance of steel pipe and extend its service life. As an important material in industrial production, precision seamless steel pipe is widely used in petroleum, chemical, boiler, power station, machinery and other industries due to its high precision, high strength and good corrosion resistance. In these fields, the surface quality of seamless steel pipe directly affects its subsequent service life and performance. Therefore, it is particularly important to pickle and passivate the surface of steel pipe during the production process.
Process flow of pickling and passivation of seamless steel pipe
The second cold drawing of seamless steel pipe pickling and passivation is raw material (bill or finished pipe) → heading → pickling → phosphorus saponification (ie lubrication) → cold drawing. If there is a second cold drawing, whether annealing is required depends on what kind of steel.
Generally, low
carbon steel does not need annealing. After the second
cold drawing → lubrication → cold drawing → annealing → straightening → cutting → finished product inspection → packaging and storage. The pickling and passivation treatment is performed for those with high quality requirements.
Conventional process of pickling and passivation treatment of seamless pipes To ensure the quality of pickling and passivation, pickling and passivation should first consider the method of immersion in pickling and passivation liquid. When it is inconvenient to use liquid immersion, consider the method of brushing pickling and passivation paste, but it is not suitable to use the method of brushing pickling and passivation liquid. When the pickling and passivation liquid immersion method is adopted, the immersion liquid needs to be tested and tested regularly. The conventional process of pickling and passivation of steel pipes is as follows: → Pickling → Flushing → Passivation (Pool Washing) → Pretreatment → → Pickling and passivation (two-in-one) liquid (Pool Washing) → Flushing → Post-treatment → Pickling and passivation (two-in-one) paste (Pool Washing) → 5.1 Pretreatment 5.1.1 Remove splashes, flux, dust, etc. from the surface of welds and parent materials.
The role of pickling of precision seamless steel pipes:
Degrease and rust the surface of precision seamless steel pipes (ASTM A106 seamless steel pipes) to prepare for the next process. In the production process, the pickling process is to remove the surface oxide scale, then lubricate (carbon steel-phosphorus saponification, stainless steel-butter lime, copper and aluminum tubes-oiling), using the old process-copper plating), and then wire drawing and deep processing. If the steel pipe is not pickled, there may be oxides and oil stains on the surface, the nuclear energy of the phosphating solution cannot be removed, and the phosphating quality will decrease.
During the prefabrication, welding, testing and heat treatment process, iron oxide, welding slag, oil stains and other dirt will accumulate on the surface of the pipe (carbon copper pipe, stainless steel pipe), which will change the corrosion resistance of the pipe.
The pipe can be cleaned with pickling liquid to remove the dirt on the surface of the pipe; after passivation treatment, a layer of anti-oxidation protective film can be formed on the surface of the steel pipe, thereby improving the corrosion resistance of the steel pipe and ensuring the normal operation of the production process of seamless steel pipe.
The importance of pickling process
In the production process of precision seamless steel pipes, the pickling process is mainly used to remove the oxide scale and rust on the surface of the steel pipe. If these oxide scales and rust are not removed in time, they will have an adverse effect on the subsequent processing. Pickling can not only improve the surface quality of the steel pipe, but also provide a good foundation for subsequent lubrication treatment and deep processing.
Remove surface impurities: During the rolling process of seamless steel pipes, a layer of oxide scale and rust often occurs on the surface. These impurities not only affect the appearance of the steel pipe, but also reduce its corrosion resistance. Through pickling, these impurities can be effectively removed, the surface of the steel pipe can be restored to brightness, and ideal surface conditions can be provided for subsequent processes.
Improve lubrication effect: The surface of the steel pipe after pickling is relatively clean and can better absorb lubricants, such as phosphorus saponification, stainless steel butter lime, etc., thereby reducing friction in the subsequent drawing process, improving processing efficiency and finished product quality.
Enhance corrosion resistance: The pickling process can not only remove surface impurities, but also passivate the metal surface to form a dense oxide film, further improving the corrosion resistance of the steel pipe.
In general, the pickling and rust prevention of
seamless steel pipes is a delicate process that needs to be operated strictly according to the specified temperature and time to ensure the pickling effect and steel pipe quality. By optimizing these parameters, production efficiency can be effectively improved and the service life of the steel pipe can be extended.