1. What is heat treatment and heat treatment oil?

A: the heat treatment of steel is to heat the steel to a certain temperature, keep it for a period of time, and cool it under the selected process conditions, so as to change the metallographic structure of the steel, so as to obtain the required process properties and mechanical properties.

The medium used to cool steel in heat treatment process is called heat treatment oil.

2. What is the cooling principle of quenching oil?  

A: the cooling process of steel in quenching oil transfers heat in three different ways. The first stage is the steam film stage, with low cooling speed; the second stage is the boiling stage, with the fastest cooling speed; the third stage is the convective heat transfer stage, with slow cooling speed.  

3. How to determine the characteristic temperature and time of quenching oil?

A: the characteristic temperature of quenching oil refers to the temperature at which the steam film breaks, that is, the boiling stage begins, and the corresponding time is the characteristic time. Characteristic temperature and characteristic time are important indexes to evaluate the quality and performance of quenching oil.

4. What is the meaning of the cooling time of quenching oil from 800 ℃ to 400 ℃?

A: the cooling time of quenching oil from 800 ℃ to 400 ℃ directly reflects the cooling ability of quenching oil in austenite unstable zone. The characteristic temperature of quenching oil is high, and the cooling time from 800 ℃ to 400 ℃ is short, which can avoid the transformation of parts to pearlite structure, so as to obtain the required martensite structure and lower bainite structure. Make the parts have high hardness, high fatigue strength and high wear resistance.

5. What are the characteristics of heat treatment oil?

A: as the heat treatment oil works under high temperature for a long time, it should have the following main properties: good cooling property, high flash point and ignition point, good thermal oxidation stability, as low as possible viscosity and moisture content, and certain brightness.

6. What is the specification of heat treatment oil in China? How is it classified?

A: the specification of heat treatment oil in China is sh0546-92. Quenching oil is divided into three categories: cold bath quenching, hot bath quenching and tempering oil. The service temperature of cold bath quenching oil is 20-80 ℃, and the maximum temperature is not more than 100 ℃, such as ordinary quenching oil, rapid quenching oil, bright quenching oil and vacuum quenching oil; the service temperature of hot bath quenching oil is 120-200 ℃, such as isothermal grading quenching oil, which is divided into No. 1 and No. 2; tempering oil is also divided into No. 1 (used for 100-180 ℃) and No. 2 (used for 180-270 ℃).

7. What is quenching oil and tempering oil?

A: the cooling medium used in the quenching process is called quenching oil, which is the main representative of the heat treatment process, and the heat treatment oil used in the tempering process is called tempering oil.

8. What is bright quenching oil?

A: the metal parts heated to a certain temperature can still keep bright surface after cooling by quenching oil, which is called bright quenching oil. Usually bright quenching oil is added with bright additive and quenched in protective atmosphere.

9. What is rapid quenching oil?

A: rapid quenching oil refers to the quenching oil with relatively fast cooling speed. The characteristic temperature of quenching oil is 580-640 ℃, and the characteristic time is less than 4 seconds. The cooling time from 800 ℃ to 400 ℃ is 4-5 seconds, which is collectively referred to as rapid quenching oil. Rapid quenching oil is suitable for quenching and tempering, carburizing and other parts requiring high cooling rate, large forging parts, large gear and quenching press in salt bath furnace, box furnace, Chinese furnace and continuous quenching furnace.

10. What is vacuum quenching oil?

A: the quenching oil used as cooling medium in vacuum quenching process is called vacuum quenching oil. The vacuum quenching oil must have low saturated vapor pressure, small evaporation loss, good thermal stability and cooling capacity. It is suitable for vacuum quenching of bearing steel, die steel, large and medium aviation structural steel, etc.

11. What is austempering oil? How many?

A: isothermal quenching is to first heat the quenching medium to the required isothermal temperature, and then put the heated parts in the quenching medium, so that the transformation of lower bainite structure is completed in the isothermal process. The cooling medium used in this process is called isothermal quenching oil; graded quenching is to put the heated workpiece in the medium slightly higher than the martensite transformation temperature for cooling, and wait for the inside and outside of the workpiece After the temperature is the same, and before the austenite begins to decompose, it is quickly transferred to the oil and cooled to room temperature, so that austenite transforms into martensite. The cooling medium used in this process is called step quenching oil. Austempering is applicable to the quenching of bearing steel, carburized steel bearing inner and outer rings, automobile gears, precision parts, half shafts and other workpieces and easily deformed parts. There are two kinds of Austempering oil No.1 and No.2, of which the service temperature of No.1 austempering oil is about 120 ℃ and that of No.2 austempering oil is about 160 ℃.

12. What are the functions and characteristics of tempering oil?

A: tempering is a process that must be carried out after steel quenching. Its purpose and function is to reduce and eliminate the internal stress caused by steel quenching and reduce brittleness. Tempering oil has good thermal oxidation stability, high flash point and good heat transfer performance. It can be divided into No. 1 and No. 2 grades. The service temperature of No. 1 is about 150 ℃ and that of No. 2 is about 200 ℃.

13. What is multistage (general) quenching oil? What are the characteristics?

Answer: multistage (general) quenching oil refers to the cooling medium used in the universal (multi-purpose) quenching furnace, which can be used to quench a variety of steels, that is, it is suitable for materials with poor hardenability, as well as for materials with good hardenability and easy deformation. The multistage (general) quenching oil has fast cooling speed at low temperature (40-80 ℃), which is equivalent to fast quenching oil. It has good thermal oxidation stability and certain cooling capacity at high temperature (120-200 ℃), and has the characteristics of small deformation after quenching.