Characteristics of metal heat treatment salt bath

Characteristics of metal heat treatment salt bath

        An industrial furnace that uses molten salt as a heating medium and immerses the workpiece in the salt to heat. According to the working temperature of the furnace, sodium chloride, potassium chloride, barium chloride, sodium cyanide, potassium cyanide, sodium nitrate, potassium nitrate and other salts are usually used as the heating medium. The heating speed of the salt bath furnace is fast and the temperature is uniform. The workpiece is always heated in the salt solution, and a salt film is attached to the surface of the workpiece when it is out of the furnace, so it can prevent the surface of the workpiece from oxidation and decarburization. The salt bath furnace can be used for heat treatment and heating of carbon steel, alloy steel, tool steel, die steel, aluminum alloy, etc., such as quenching, annealing, tempering, cyanidation, and aging. It can also be used for low-oxidation heating during precision forging of steel. The maximum working temperature of nitrate does not exceed 570℃. The maximum working temperature of BaCl2 can reach 1350℃.

Advantages of salt bath quenching:

1. The quenching heating time is short, the crystal grains will not be coarsened, and the toughness is strong, which is conducive to strain.

2. The furnace temperature is well distributed and the strain becomes less.

3. Fast cooling in high temperature area, slow cooling in low temperature area, easy quenching, and reduced strain.

4. It can correspond to a wide range of heat treatment conditions (intermittent quenching, austempering, partial heat treatment, short-time heating, cooling, complex temperature changes, etc.).

5. Less oxidative decarburization.

6. The adjustment of heat treatment temperature and time can be completed in a short time, and can correspond to multiple varieties and small batches.

7. The equipment cost is relatively cheap.

        Salt bath heating methods include direct heating (electrode) and external heating. The high temperature adopts the electrode type heated by direct current in the salt bath. The medium temperature and low temperature adopt external heating type. The external heating type is to add salt to a steel tank and then heat the tank. Temperature control is a bit difficult, but the advantage is that in addition to electricity, you can also use steam, oil, etc., and use diversified energy.