Seamless alloy steel pipe vs. Seamless carbon steel pipe

Seamless alloy steel pipe and seamless carbon steel pipe have significant differences in material composition, performance characteristics, manufacturing process, application field, cost and procurement. The following is a detailed comparison of the two:

1. Material composition

Seamless alloy steel pipe: A small amount of alloying elements such as chromium, nickel, tungsten, molybdenum, etc. are added to carbon steel to improve its performance. The content and proportion of these alloying elements can be adjusted according to specific uses and requirements. The total content of alloying elements is ≥5%, and typical materials are: 15CrMo, 12Cr1MoV, P91/P92, 304/316 stainless steel, ASTM A333 Gr.6, etc.

Seamless carbon steel pipe: Mainly composed of carbon and iron, its carbon content will affect its mechanical properties and processing properties. According to the different carbon content, carbon steel seamless steel pipes can be divided into low carbon steel, medium carbon steel and high carbon steel. Alloying elements contain only trace amounts of Mn and Si (alloying elements <5%), and typical materials are: 20#, 45#, Q235, ASTM A106, ASTM A53, etc.

2. Mechanical properties

Seamless alloy steel pipe:
It has good corrosion resistance, high temperature resistance, impact toughness and strength, because the addition of alloy elements can improve the performance of steel pipes. The yield strength of seamless alloy steel pipes is ≥300 MPa, the tensile strength is 550~1000 MPa (or even higher), and the hardness is higher.

a. The corrosion resistance is significantly better than carbon steel (especially stainless steel and chrome-molybdenum steel), and the thin and strong oxide film on the surface makes its corrosion control level exceed a certain standard under all water qualities.
b. High mechanical strength, tensile strength is more than double that of ordinary low-carbon seamless pipes.
c. High high temperature resistance, chrome-molybdenum steel can withstand temperatures above 600℃, and carbon steel can withstand temperatures of ≤350℃ for a long time.
d. Long service life, good wear resistance, and extremely high gloss after internal and external polishing.
e. Good welding performance, products of different sizes and specifications can be customized according to customer requirements.

Seamless carbon steel pipe:
It has the advantages of good strength, compressive resistance, and high hardness. The yield strength of seamless carbon steel pipe is 235~355MPa, and the tensile strength is 370~600MPa.

a. Low carbon steel has good toughness and weldability, and is suitable for manufacturing general structures and fluid delivery pipelines.
b. Medium carbon steel has high strength and wear resistance, and is often used to manufacture mechanical parts and bearings.
c. High carbon steel is often used to manufacture knives and cutting tools due to its high hardness and wear resistance.
d. Carbon steel pipes have poor corrosion resistance and require surface galvanizing, plastic coating and other anti-corrosion measures.

3. Manufacturing process

Seamless alloy steel pipe: The manufacturing process involves hot rolling (extruded seamless steel pipe) and cold drawing (rolling) seamless steel pipe. The required performance is obtained by adding alloy elements and corresponding heat treatment processes. The heat treatment process is complex, such as quenching + tempering, solution treatment, etc. During smelting, the alloy composition needs to be precisely controlled (such as vacuum degassing).

Seamless carbon steel pipe: Mainly manufactured by perforated hot rolling method, sometimes the hot-processed pipe needs to be further cold-processed (cold-rolled/cold-drawn) to obtain the corresponding shape and size. The heat treatment process is simple, such as normalizing, annealing, etc. During smelting, ordinary converter/electric furnace smelting is sufficient.

4. Application

Seamless alloy steel pipe:
Mainly used in petroleum, chemical, aviation, aerospace, electricity, coal, ships, railways and other fields, especially in high pressure, high temperature and high corrosion environment.

Typical application:
- High temperature and high pressure environment: boiler tube (such as 15CrMoG)
- Corrosion-resistant scene: chemical equipment (316L stainless steel)
- Extreme temperature: LNG cryogenic pipeline (9% Ni steel)
- High strength parts: aviation hydraulic pipe, gun barrel

Seamless carbon steel pipe:
Mainly used in the manufacture of mechanical parts, building structural parts, general structure and fluid delivery pipelines and other fields.

Typical applications:
- General fluid transportation: water, oil, gas pipelines
- Structural support: building scaffolding, mechanical frame
- Low pressure system: HVAC pipeline
- General machining: shafts, sleeves

5. Cost and procurement factors

Seamless alloy steel pipe:
Raw material cost is high, and alloy elements such as nickel and molybdenum are expensive. Processing cost is also high, requiring special heat treatment and testing. The market price is about 8,000~30,000 yuan/ton (depending on alloy composition).

Seamless carbon steel pipe:
Carbon steel is a bulk commodity with a stable market price. The processing cost is low, the process is mature, and the production efficiency is high. The market price is about 4,000~8,000 yuan/ton.

Seamless alloy steel pipe vs. Seamless carbon steel pipe: How to choose?

Choose seamless alloy steel pipe:
High temperature, high pressure, corrosive or extreme temperature environment (such as petrochemical, electric power, aerospace).
Scenarios with demanding requirements on material strength and life.

Choose seamless carbon steel pipe:
Projects with normal pressure and temperature conditions and limited budget (such as construction and general machinery).
Scenarios that do not require long-term corrosion resistance or can accept surface anti-corrosion treatment.

Conclusion:

Seamless alloy steel pipes have obvious advantages in performance and adaptability to special environments, but the cost is relatively high; seamless carbon steel pipes are economical and practical and suitable for normal needs. When choosing, it is necessary to comprehensively evaluate the working conditions, life requirements and budget.

Read more: ASTM A335/A335M Seamless Alloy Steel Pipe or Seamless Stainless Steel Pipe vs Seamless Carbon Steel Pipe