Low-temperature steel pipes are medium-carbon structural steels that have good thermal and cold performance, good mechanical properties, low prices and wide sources, so they are widely used. Its biggest weakness is its low hardenability, and it is not suitable for workpieces with large cross-section sizes and high requirements.
Seamless steel pipe for cryogenic pipelines
Spot specifications: 8-1240×1-200mm<1/8"-48"×SCH5S-SCH160, STD, XS, XXS>
Product material:, 10MnDG, 09DG, 09Mn2VDG, 06Ni3MoDG,
ASTM A333-Grade1, Grade3, Grade4, Grade6, Grade7, Grade8, Grade9,
Grade10,Grade11
Product application: Suitable for -45℃～-195℃ low-temperature pressure vessel pipes and seamless steel pipes for low-temperature heat exchanger pipes
Production process: cold drawing and hot rolling
Weight calculation formula: (outer diameter-wall thickness)*wall thickness*0.02466/1000=meter/ton
The hardness of low-temperature steel pipe quenched and tempered parts after quenching should reach HRC56~59. The possibility of larger cross-sections is lower, but it cannot be lower than HRC48. Otherwise, it means that the workpiece has not been completely quenched, and sorbite or even ferrite may appear in the structure. The structure remains in the matrix after tempering and cannot achieve the purpose of tempering.
For high-temperature tempering after quenching of low-temperature steel pipes, the heating temperature is usually 560~600℃, and the hardness requirement is HRC22~34. Because the purpose of tempering is to obtain comprehensive mechanical properties, the hardness range is relatively wide. However, if the drawing has hardness requirements, the tempering temperature must be adjusted according to the drawing requirements to ensure the hardness. For example, some shaft-type low-temperature steel pipes require high strength and high hardness requirements; while some gears and shaft parts with keyways need to be milled and inserted after tempering, so the hardness requirements are lower. Regarding the tempering and holding time, it depends on the hardness requirements and the size of the workpiece. We believe that the hardness after tempering depends on the tempering temperature and has little to do with the tempering time, but it must be tempered. Generally, the tempering and holding time of the workpiece is always More than an hour.
