1. the relationship between the state of nitrate salt and temperature. the common formula for mixing nitrate salt is 55% KNO_3 + 45% NaNO_2, with a melting point of 137 ℃, and is used in the range of ~ 500 ℃. Thermocouples are generally used for the temperature measurement of isothermal salt bath quenching tank . After long-term observation, it is found that the state of nitrate salt changes with temperature. The color of nitrate salt with the increase of temperature from deep to light (from dark brown to gray), according to this, the operator can be observed by the naked eye, roughly determine the temperature of nitrate salt.

2. with the continuous development of heat treatment technology, in addition to the continuous improvement of technology, in recent years many manufacturers have focused on improving quenching medium, for example, nitrate quenching medium is being used more and more widely. Nitrate has a relatively strong cooling capacity, but in the low temperature stage has tended to be flat, with a better cooling performance!

is not significant.

 

what matters should be paid attention to during the use of nitrate salt quenching medium in isothermal quenching tank:

, it will burn violently and even explode after contact. & nbsp;

One thing that should be taken care of is that charcoal and other things should not be mixed in, and water should never enter. & nbsp;

nitrate salt must not run out of temperature, otherwise the use temperature of different formulations is different, generally using double table control. If the instrument fails to run temperature, first cut off the power supply for natural cooling, and never add water for cooling, otherwise an explosion will occur.Due to the ignorance of foreign personnel, several people were injured when the nitrate furnace was running at a temperature and spraying water. I hope my colleagues will pay attention to it., Heat treatment safety first. The medium has been in use for more than a year. It is Milky White to use it for more than 250 degrees at the beginning. Now it turns brown because the oxide skin of the workpiece falls off. The color changes over time will slow down the cooling rate and need to be cleaned frequently.

 

cleaning method: raise the temperature of nitrate salt to 380 & mdash;400 ℃, keep warm for 1h, turn off the power supply, precipitate for 1h, and scoop up impurities at the bottom of the furnace. & nbsp;

physical properties of sodium nitrite: molecular formula: NaNO2, microstrip yellowish white crystal, density 2.17(20 ℃), melting point 217 ℃, ethanol, easily deliquescent in air. Decomposition at 320°C to form oxygen, nitrogen, nitrogen oxide and sodium oxide. Combustion and explosion are easy to occur in contact with organic matter, and toxic nitrogen oxide gas is emitted during combustion. Can absorb oxygen from the air gradually into sodium nitrate.