1. What is heat treatment and heat treatment oil? Answer: Heat treatment of steel involves heating the steel to a certain temperature, maintaining it for a period of time, and cooling it under selected process conditions to change the metallographic structure of the steel, thereby obtaining the required process and mechanical properties. The medium used to cool steel during the heat treatment process is called heat treatment oil. 2. What is the cooling principle of quenching oil? Answer: The cooling process of steel in quenching oil involves heat transfer in three different ways. The first stage is the steam film stage, with a low cooling rate; The second stage is the boiling stage, at which the cooling rate is the fastest; The third stage is the convective heat transfer stage, where the cooling rate is relatively slow. 3. How are the characteristic temperatures and time of quenching oil determined? Answer: The characteristic temperature of quenching oil refers to the temperature at which the steam film ruptures, i.e. the boiling stage begins, and the corresponding time is the characteristic time. Characteristic temperature and characteristic time are important indicators for evaluating the quality and performance of quenching oil.
4. What is the meaning of the time for quenching oil to cool from 800 ℃ to 400 ℃? Answer: The cooling time of quenching oil from 800 ℃ to 400 ℃ directly reflects the cooling capacity of quenching oil in the unstable zone of austenite. 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, thus obtaining the required Martensite structure and lower Bainite structure. Make the parts have high hardness, high fatigue strength, and high wear resistance. 5. What characteristics should heat treated oil possess? Answer: Due to long-term operation at high temperatures, heat treated oil should have the following main properties: good cooling performance, high flash and ignition points, good thermal oxidation stability, as low as possible viscosity and moisture content, and have a certain degree of brightness. 6. What are the specifications and standards for heat treatment oil in China? How is it classified? Answer: The specification of heat treatment oil in China is SH0546-92, and quenching oil is divided into three categories: cold bath quenching, hot bath quenching, and tempering oil. The use temperature of cold bath quenching oil should not exceed 100 ℃ at a maximum of 20-80 ℃, such as ordinary quenching oil, rapid quenching oil, bright quenching oil, and vacuum quenching oil; The use temperature of hot bath quenching oil is 120-200 ℃, such as isothermal graded quenching oil, which is divided into two types: No.1 and No.2; Tempering oil is also divided into two types: No. 1 (used at 100-180 ℃) and No. 2 (used at 180-270 ℃). 7. What is quenching oil and tempering oil? Answer: The cooling medium used in the quenching process is called quenching oil, which is the main representative of the heat treatment process. The heat treatment oil used in the tempering process is called tempering oil. 8. What is Bright Quenching Oil? Answer: Metal parts heated to a certain temperature can still maintain a bright surface after being cooled by quenching oil, which is called bright quenching oil. Usually, bright quenching oil is added with bright additives and quenched in a protective atmosphere.
9. What is rapid quenching oil?
Answer: Quick quenching oil refers to quenching oil with a relatively fast cooling rate. The characteristic temperature of quenching oil is between 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 fast quenching oil. Quick quenching oil is suitable for quenching salt bath furnaces, box furnaces, Chinese furnaces, and continuous quenching furnaces for parts requiring high cooling rates such as quenching and tempering, carburizing, and large forged parts, large gears, and quenching presses.
10. What is vacuum quenching oil?
Answer: Quenching oil used as a cooling medium in vacuum quenching process is called vacuum quenching oil. Vacuum quenching oil must have low saturated vapor pressure and small evaporation loss, as well as good thermal stability and cooling ability. Suitable for vacuum quenching of materials such as bearing steel, tooling steel, large and medium-sized aviation structural steel, etc.
11. What is isothermal graded quenching oil? How many are there?
Answer: Isothermal quenching is to first heat the quenching medium to the required isothermal temperature, and then place 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; Stepped quenching is to put the heated workpiece in the medium slightly higher than the Martensite transformation temperature for cooling. After the internal and external temperatures of the workpiece are consistent, the workpiece is quickly transferred to the oil for cooling to room temperature before the austenite begins to decompose, so that the austenite can be transformed into Martensite structure. The cooling medium used in this process is called stepped quenching oil. Isothermal graded quenching is suitable for quenching inner and outer rings of bearings made of bearing steel and carburized steel, automotive gears, precision parts, half shafts, and easily deformed parts. There are two types of isothermal graded quenching oil: No. 1 and No. 2, with the temperature of No. 1 isothermal graded quenching oil being around 120 ℃ and No. 2 oil being around 160 ℃.
12. What are the functions and characteristics of tempering oil? Answer: Tempering is a necessary process after steel quenching, which aims 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 is divided into two grades: grade 1 and grade 2, with grade 1 operating at around 150 ℃ and grade 2 operating at around 200 ℃. 13. What is multi-level (universal) quenching oil? What are the characteristics? Answer: Multi grade (universal) quenching oil refers to the cooling medium used in a universal (multi-purpose) quenching furnace, which can quench various steels. It is suitable for materials with poor hardenability, as well as for materials with good hardenability and easy deformation. Multi stage (universal) quenching oil has a fast cooling rate when used at low temperatures (40-80 ℃), which is equivalent to fast quenching oil. When used at high temperatures (120-200 ℃), it has good thermal oxidation stability and certain cooling ability, and has the characteristic of small deformation of parts after quenching.
