First, a brief introduction to the material of 35CrMo Seamless Steel Pipe.
35CrMo seamless steel pipe is a medium-carbon alloy structural steel seamless pipe with the following core properties:
1. Chemical Composition of 35CrMo Seamless Steel Pipe:
Carbon: 0.32%-0.40%, providing basic strength;
Chromium: 0.80%-1.10%, improving hardenability and tempering stability;
Molybdenum: 0.15%-0.25%, refining grain size and enhancing high-temperature strength and toughness;
Silicon and manganese: assist in deoxidation and strengthen ferrite;
Phosphorus and sulfur: ≤0.035%, reducing low-temperature brittleness. Mechanical Properties of 2.35CrMo Seamless Steel Pipe:
Tensile Strength: ≥980MPa (GB/T3077 standard), with some processes reaching 1080-1230MPa;
Yield Strength: ≥835MPa;
Elongation: ≥12%, with some processes reaching 18%;
Impact Toughness: Impact Energy ≥34J at -20°C, exceeding 180J in low-temperature applications.
Heat Treatment Characteristics of 35CrMo Seamless Steel Pipe:
Quenching Temperature: 850-880°C, Oil Quenching for 15-40mm Φ, Water Quenching for 28-60mm Φ;
Tempering Temperature: 500-650°C, Tempering Holding Time ≥90 minutes, to achieve a tempered bainite structure, balancing strength and toughness. Applications of 3.35CrMo seamless steel pipe:
Petroleum industry: drill collars, drill pipe, and oil casing, subject to high pressure and complex geological conditions;
Chemical equipment: high-pressure vessels, reactors, and heat exchanger pipes, resistant to corrosive media;
Power industry: boiler tubes and superheater tubes, subject to long-term stable operation in high-temperature, high-pressure steam environments;
Machinery manufacturing: shafts, gears, and connecting rods, subject to alternating loads;
Extreme environments: polar oil and gas pipelines and rail fasteners in cold regions, maintaining ductile fracture characteristics even at -110°C.
Second, 35CrMo Seamless Steel Pipe Processing Details
The processing of 35CrMo seamless steel pipe requires strict control of process parameters to ensure stable performance:
1. 35CrMo Seamless Steel Pipe Production Process:
Raw Material Preparation: Select high-quality 35CrMo alloy steel billets, controlling the content of harmful elements such as P and S;
Hot Rolling:
A. Heating Temperature: 1100-1250°C, homogenization treatment;
B. Piercing and Rolling: Piercing is performed using a three-roll cross-rolling mill, and the initial pipe shape is obtained after sizing.
2. Cold Drawing of 35CrMo Seamless Steel Pipe:
Multi-pass die drawing (elongation coefficient 1.3-1.5), with a grain size meeting ASTM standards. Grade 8 or above;
Inner wall honing: Surface roughness Ra ≤ 0.8μm, reducing turbulent losses in fluid transportation;
Heat treatment of 3.35CrMo seamless steel pipe:
Quenching: Oil quenching at 860-880°C to form a uniform bainite-martensite structure;
Tempering: 500-650°C for ≥ 90 minutes, residual stress ≤ 120 MPa;
Finishing and testing of 4.35CrMo seamless steel pipe:
Eddy current testing: 100% non-destructive testing, flaw detection pass rate ≥ 99.93%;
Dimensional tolerance: Outer diameter tolerance ±0.15mm (for high-precision applications such as rail fasteners), wall thickness tolerance ±5%;
Mechanical property verification: Tensile strength measured by a tensile testing machine, impact energy measured by an impact testing machine. Key process control points for 5.35CrMo seamless steel pipe:
Quenching temperature: Precisely controlled within the range of 860-880°C to avoid structural defects;
Tempering holding time: ≥90 minutes to ensure sufficient stress release;
Cold drawing elongation coefficient: 1.3-1.5, balancing work hardening and ductility;
Inner wall honing: Ra ≤ 0.8μm to improve fluid flow efficiency;
Non-destructive testing: Eddy current testing sensitivity ≥ 0.5mm to eliminate microcracks.
Processing equipment requirements for 6.35CrMo seamless steel pipe:
Hot rolling mill: Three-roll cross-rolling mill equipped with an online temperature gauge and a tension sensor;
Cold drawing mill: Four-pass die stretching system, supporting outer diameter processing from 6 to 120mm;
Heat treatment furnace: Controlled atmosphere furnace with temperature uniformity of ±5°C;
Testing equipment: Rockwell hardness tester (HRC 28-32), direct reading spectrometer (real-time element content monitoring), and coordinate measuring machine (form and position tolerance testing).
Post time: Sep-11-2025