I. Petroleum cracking seamless pipe definition:
Petroleum cracking seamless pipe is a long, hollow and seamless steel that is an economical material for the industry due to its efficient cross-sectional design.
With its weldless, continuous structure, this tube excels in compressive strength and durability, and is widely used in the manufacture of critical mechanical components, such as drill rods in oil drilling equipment, automotive drivetrain components, bicycle frames, and structural steel support frames at building construction sites.
II. Petroleum cracking seamless pipe standard:
Chinese National Standard (GB/T9948)
i. Core Specifications
a. Scope of application:
Specially designed for petroleum refining plant, applicable to cracker pipe, heat exchanger pipe, reactor pipe and other high temperature and high pressure scenarios.
b. Material Requirements:
Base material: carbon steel (20G), chrome-molybdenum alloy steel (15CrMoG, 12Cr2MoG, etc.), austenitic stainless steel (1Cr18Ni9).
c. Chemical composition:
C, Si, Mn, Cr, Mo and other elements of the content of strict limits (such as 12Cr2MoG requires Cr content of 2.0-2.5%, Mo content of 0.9-1.1%).
ii. Mechanical properties
a. High-temperature strength:
550 ℃ lasting strength needs to be ≥ 60MPa (12Cr2MoG as an example).
b. Impact toughness:
-20 ℃ low-temperature impact work ≥ 34J. c. Process requirements: must be used in the heat treatment process.
c. Process requirements:
Must be hot-rolled or cold-drawn seamless process, prohibit the use of welded steel pipe. 100% eddy current flaw detection + 20% ultrasonic re-inspection is required.
International mainstream export standards
i. American Standard
a. ASTM A335:
Standard for seamless tubes of ferritic alloy steel for high temperature use, corresponding to the Chinese 12CrMo series.
b. Typical grades:
P11 (1.25Cr-0.5Mo), P22 (2.25Cr-1Mo).
c. Key Differences:
Hardness Gradient Test (HV10 test) is required.
d. ASTM A312:
Standard for Austenitic Stainless Steel Seamless Tubes and Pipes for corrosive media environment.
ii. European Standards
a. EN 10216-2:
Standard for seamless tubes for pressure purposes, covering materials such as P265GH, 15Mo3, etc.
b. Special requirements:
Ultrasonic inspection report for defects below 3.2mm is required.
c. EN 10216-5:
Special standard for seamless stainless steel tubes, requiring intergranular corrosion test (ISO 3651-2).
iii. Japanese Standards
a. JIS G3458:
Standard for alloy steel pipe, STPA series (e.g. STPA23 corresponds to 12Cr1MoVG).
b. Characteristic tests:
Sulfur Print Test (Sulfur Print Test) is mandatory.
Comparison of domestic and foreign standards (12Cr2MoG as an example)
| Parameter | GB/T 9948 | ASTM A335 P22 | EN 10216-2 |
|---|---|---|---|
| Applicable Temperature | ≤600°C | ≤593°C | ≤580°C |
| Yield Strength | ≥275 MPa | ≥310 MPa | ≥280 MPa |
| Hardness Requirement | ≤225 HBW | ≤250 HBW | ≤265 HBW |
| Impact Energy | ≥34 J (-20°C) | ≥41 J (21°C) | ≥40 J (0°C) |
III. Petroleum cracking seamless pipe manufacturing process details
i. Seamless hot-rolled tube process
The hot-rolled seamless pipe process is designed for the mass production of high-strength tubes and consists of 12 key processes:
a. Billet treatment:
Round billets are heated to 1,200-1,280°C to optimise the plasticity of the material.
b. Forming process:
The hollow billet is formed by piercing machine, and wall thickness tolerance ±5% is controlled by three-roll tilting rolling technology.
c. Dimensional finishing:
OD accuracy upgraded to ASTM A530 through sizing/reducing unit.
d. Quality verification:
100% eddy current flaw detection of surface defects, hydrostatic test pressure up to 30MPa.
e. Intelligent Marking:
Laser engraved traceable code containing steel grade, furnace number, and execution standard.
f. Technical Advantage:
Single line capacity up to 50 tonnes/hour, suitable for production of large diameter pipes over Φ114mm.
For the demand of high-precision thin-walled tubes, an 18-step precision control process is adopted:
a. Pre-treatment:
Tube billet beheaded to form the haul-off end, annealed at 850°C to remove residual stress.
b. Surface engineering:
hydrochloric acid pickling to remove oxide skin, phosphate coating to reduce the coefficient of friction in cold drawing.
c. Deformation processing:
wall thickness tolerance of ±0.05mm is achieved through 8-12 cold drawing passes.
d. Performance control:
Protective atmosphere heat treatment to ensure uniformity of hardness (HRC 22±2).
e. Non-destructive testing:
Ultrasonic flaw detection can identify internal defects with a depth of 0.3mm.
f. Core value:
Production of Φ6-89mm precision tubes with surface roughness Ra≤1.6μm
iii. Comparison of key technologies
| Parameter | Hot Rolling Process | Cold Drawing Process |
|---|---|---|
| Production Efficiency | 45-60 tons/hour | 3-5 tons/hour |
| Dimensional Accuracy | ±0.5% | ±0.1% |
| Surface Finish | Oxide scale requires subsequent treatment | Mirror finish achieved directly |
| Application Scenarios | Main pipelines for energy transportation | Precision components in hydraulic systems |
| Energy Consumption per Unit | 280 kWh/ton | 420 kWh/ton |
