The 12CrlMoV steel pipe (wall thickness greater than 40mm) used for power transmission and distribution construction is heated. The phenomenon of cooling, low speed and low hardness of the steel pipe has occurred. For example, the use of air cooling, water spraying or oil immersion cooling has caused technical problems, large equipment investment and environmental pollution. Therefore, the heat treatment test of 12CrlMoV steel pipe in frequency induction heating furnace has been carried out and applied to the production practice, and the practical results have been obtained.
After the 12CrlMoV steel pipe specimen is austenitized by heating, it is cooled in water at about 20 ℃. The heat treatment test of medium frequency induction heating equipment shows that in actual production, the immersion termination temperature can be controlled according to the wall thickness and the corresponding immersion time. The microstructure of 12CrlMoV steel pipe sample after water immersion and air cooling is characterized by a high content of pearlite and granular bainite, which is conducive to improving the high temperature endurance strength. The organization meets the requirements of technical conditions. At the same time, after treatment, the mechanical properties such as hardness meet the technical requirements and have excellent performance.
The effects of immersion cooling time, cooling rate and water temperature on the steel pipe were investigated. The results show that the heat output from the sample per unit time is directly proportional to the temperature difference between the sample and the cooling medium, and the cooling speed of the sample is inversely proportional to the temperature of the cooling medium within a certain range. The heat treatment characteristics of steel pipe medium frequency induction heating equipment are as follows:
1. The heat treatment process of 12CrlMoV steel pipe can improve the cooling speed in the high temperature section (higher than 600 ℃ ± 50 ℃); Increase the content of granular bainite and pearlite to improve their properties.
2. The immersion temperature can be controlled by controlling the immersion time, so as to control the occurrence of martensite and avoid cracking of pipe fittings. After water immersion treatment, no martensite structure and cracks are found, and the metallographic structure and performance indexes fully meet the technical requirements.
3. The low hardness defect of 12CrlMoV steel pipe with wall thickness greater than 40mm has been well solved by using medium frequency induction heating equipment and heat treatment process, and the production application is good.
4. In production, the corresponding immersion time can be determined according to the test curve according to the wall thickness of the steel pipe, and the immersion time can also be adjusted according to the change of the water temperature.
Overseas manager: Tom Wang
Phone: 0086-13303078975(whatsapp, wechat,line)
Specialist of induction heat treatment furnace in China; Glad to be your business partner in induction heating field.
Post time: 09-08-2022