What is the main manufacturing process of 15CrMo seamless steel pipe?
Hot rolling or cold drawing process: hot rolling process includes round steel perforation → pipe rolling → sizing → straightening → non-destructive testing; cold drawing improves accuracy through cold deformation, and the process is hot rolling tube billet → pickling → phosphating → cold drawing → heat treatment. The key control points are the perforation temperature (1150℃~1200℃) and the final rolling temperature ≥850℃ to avoid grain coarsening.
What are the heat treatment processes of 15CrMo steel pipe?
Normalizing (900℃~930℃) + tempering (620℃~650℃) must be performed. Normalizing refines the grains, and tempering eliminates stress and improves toughness. When the wall thickness is greater than 30mm, it is necessary to heat in sections to prevent deformation. The post-weld heat treatment (PWHT) temperature is consistent with tempering (620℃~650℃), and the insulation time is calculated as 2.5min/mm.
How to deal with the weld of 15CrMo welded steel pipe?
Submerged arc welding (SAW) or tungsten inert gas welding (GTAW) is used, and the welding material is R307 (E5515-B2). Preheat 250℃~300℃ before welding, the interlayer temperature is ≤300℃, and dehydrogenation treatment is performed immediately after welding (300℃×1h). PWHT must be performed in the end to avoid embrittlement of the weld area. The weld needs 100% radiographic testing (RT) or ultrasonic testing (UT).
What are the surface quality requirements for 15CrMo steel pipes?
The surface must be free of defects such as cracks, folds, and scars, and slight scratches with a depth of ≤0.1mm are allowed. The oxide scale on the inner and outer walls needs to be sandblasted or pickled to remove. High-temperature pipes need to be shot peened on the inner wall to reduce the shedding of oxide scale during operation. The delivery state is generally sandblasted after heat treatment, and anti-rust oil can be applied for special requirements.
How to control the dimensional accuracy of 15CrMo steel pipes?
The outer diameter tolerance is in accordance with GB/T 17395 standard: hot rolled tube ±0.75%~1.25%, cold drawn tube ±0.2mm. Wall thickness tolerance: hot rolled ±10%, cold drawn ±5%. Ovality ≤ 80% of the outer diameter tolerance. Critical applications (such as boiler tubes) require 100% eddy current testing (ET) to ensure wall thickness uniformity.
