Common problems and solutions of heat treatment medium

1. What problems should be paid attention to when using new oil in the tank?

Before pouring new oil, the quenching oil tank and cooling system must be carefully checked and cleaned. The remaining water, oil sludge and other dregs should be cleaned up. When adding new oil to the old oil tank system, the oil stain on the tank wall above the oil level in the quenching oil tank and on various frames should also be removed and cleaned. If the original oil residue and sludge are mixed with the new oil, the cooling characteristics of the oil may be changed. Therefore, the cleaning work should be done more thoroughly than using a new oil sump.

After the new tank is filled with new oil, it should not be used for quenching production immediately. During the production, transportation and dumping of quenching oil, a small amount of air is always brought in. Journal of Metalworking and Hot Working. The presence of gas will reduce the cooling rate of the quenching oil at the high temperature stage and should be removed. The solubility of gas in oil decreases with the increase of oil temperature. Increasing the oil temperature can reduce the viscosity of the oil and help the bubble to float. Therefore, the gas in the new oil can be removed by increasing the oil temperature.

2. Why should the quenching oil be stirred circularly?

A good cooling cycle can avoid excessive local oil temperature and make the oil temperature in all parts of the tank uniform. The oil cooling cycle can increase the relative flow rate between the workpiece and the quenching oil, thus improving the oil cooling capacity and avoiding soft spots on the workpiece surface.

When the oil temperature is too high, the local oil temperature will be higher immediately after the workpiece is oiled, which may cause fire hazard.

3. How to reduce oil pollution?

The pollution sources of quenching oil include external pollution and self pollution.

External pollution: oxide scale brought in during workpiece quenching, water leaked from cooling system and other substances from outside.

Self pollution: oxidation deterioration products that cannot be automatically discharged in use but remain in the oil; In addition, the residual products after the reaction of foreign pollutants with quenching oil and its pollutants. The accumulation of internal and external pollutants will gradually change the color, transparency, viscosity, flash point, carbon residue and acid value of the oil. This change process is the deterioration process of quenching oil. Among the influences caused by the modification, the change of the oil cooling characteristics and the deterioration of the brightness of the workpiece after quenching have the greatest relationship with the heat treatment effect of the workpiece. The change of cooling characteristics often affects the quenching hardness, hardening depth and deformation of the workpiece. From the heat treatment ecosystem.

Prevention and reduction of external pollution, reasonable use and management of quenching oil, and regular cleaning can slow down the deterioration of quenching oil and prolong the service life of quenching oil.

4. What is the oil change index of quenching oil?

The replacement of quenching oil depends on the specific degree of aging, not on how long it takes. Regular sampling and analysis shall be conducted during the use. The aging degree of quenching oil mainly depends on the base oil, additives and on-site service conditions.

General oil change index of quenching oil:

(1) The characteristic temperature drops by more than 40 ℃;

(2) Under normal use, the water content exceeds 0.1% (volume fraction).

(3) The viscosity increases by more than 15%;

(4) Brightness is obviously reduced.

5. What should we do after the water enters the quenching oil?

The water inlet of quenching oil will affect the cooling performance, especially the low temperature cooling rate. The workpiece after quenching may cause excessive deformation or cracking.

The quenching oil after water inlet shall be subject to high-temperature dehydration treatment, and the oil temperature shall be heated to 80-130 ℃ for heat preservation and stirring for a certain time, depending on the amount of water inlet. After dehydration, the cooling performance shall be tested, and it can be used normally only after meeting the factory requirements, otherwise, additives shall be added for adjustment.

6. How to use water-based quenching liquid?

The water-based quenching liquid shall be mixed with water. The proportion of water shall be determined according to the actual workpiece and material. The use temperature shall not exceed 50 ℃. If the temperature is too high, the cooling performance will be seriously reduced, resulting in the workpiece hardness failing to meet the requirements.