Quenching is to heat the metal parts above the transformation temperature and cool them rapidly in the quenching medium after heat preservation, so as to improve or adjust the hardness and wear resistance of the parts. In this process, the quenching medium (quenching liquid) is required to have a series of performance requirements, such as good low deformation, low burning cracking, heat resistance, cleaning, degreasing, rust prevention, cooling, brightness, etc. generally, the quenching liquid is divided into oil-based type and water-based type according to its composition.
The earliest used oil is animal and vegetable oil, which has weak cooling capacity, but still has enough cooling capacity, and when the oil temperature rises, it has little effect on the quenching capacity, so it is an ideal quenching medium. Due to the limitation of price and raw material source, mineral oil is widely used in industry, such as 0 × diesel oil, 15 ~ 32 × viscosity grade mechanical oil, etc. With different viscosity and flash point, the cooling capacity and service temperature of mineral oil are different. Because of its slow cooling rate, it is not easy to harden the carbon steel and low alloy steel with large section, and the surface of the material is easy to stain, so the use of oil is limited. In order to improve the cooling capacity of the oil, the methods of properly increasing the oil temperature (usually within the range of 80 ℃), strongly stirring circulation and adding additives can be adopted. Additives such as sodium sulfonate, barium sulfonate, calcium sulfonate and calcium naphthenate are added into the oil. During quenching and cooling, the additives stick to the surface of the workpiece and become the mass point of the second-class domestic product Zeng steam bubble, which makes the stable steam film difficult to form and improves the cooling capacity in the high temperature area. This oil is called "fast quenching oil".
In addition, adding heat stabilizer, ash free surfactant and 1% sodium mizoline oleate and 0.3% T501 to light oil and quench oil extracted by solvent refining method can make the surface of workpiece quickly covered by oil film after quenching without carbon black deposition on the surface, thus making the surface of workpiece bright and clean after quenching. This kind of oil is called "bright quench oil". In addition, the addition of surfactant in mineral oil can make the metal quenching uniform, and is conducive to the cleaning of mineral oil after quenching. For example, add 2% ~ 5% non-ionic emulsifier such as nonylphenol polyoxyethylene (6) ether to the quenching mineral oil, and wash the metal products with water after quenching to remove the mineral oil.
The main reasons for the blockage of quenching furnace
(1) The air preheater is corroded at low temperature, the surface of the heating surface becomes wet and rough, which makes the ash accumulation and ash blocking worse.
(2) The economizer leaks water, and the boiler is not shut down in time for treatment, so that a layer of water film is formed on the surface of preheater, and the fly ash and water film form a mud paste, blocking the pipe.
(3) During the maintenance, the ash accumulated in the economizer or air preheater is flushed with water. Before it is completely dried, it is started to operate. As a result, the ash accumulated is intensified, forming a blockage.
(4) The heat preservation materials or other sundries of quenching furnace fall into the air preheater, the flow of flue gas is not smooth, and the ash accumulation is intensified and blocked.
(5) For horizontal air preheater, the pipe pitch of low temperature section is small, which makes the ash "bridge" and form blockage.
On 2018-08-08 11:45:46
