What is Alloy Pipelines?
Alloy Pipelines are made of multiple elements, such as chromium, nickel, molybdenum, etc. The performance of the pipe is improved by controlling the content of different elements. Different components and contents will show different performance.
The role of different alloying elements
- Chromium (Cr): Enhances corrosion resistance and high temperature resistance
- Nickel (Ni): Enhances toughness and corrosion resistance, excels in low temperature environments.
- Molybdenum (Mo): Improves corrosion resistance, excels in chlorides.
- Titanium (Ti): Improves strength and corrosion resistance, especially in high temperature and corrosive environments.
- Manganese (Mn): Improves strength and hardness, enhances wear resistance.
- Copper (Cu): Improves corrosion resistance and machinability.
- Aluminum (Al): Reduces density, and increases strength and corrosion resistance.
- Silicon (Si): Improves castability and oxidation resistance.
Types of Alloy Pipelines
There are only two processes for alloy pipes: seamless pipes and welded pipes. Seamless alloy pipes are formed by cold drawing or hot rolling, have no welds and do not require welding, and have strong pressure resistance. Welded alloy pipes are welded after steel rolling, and have lower costs.
Common grades of alloy pipelines
Stainless steel pipes (304, 316, 321)
Nickel-based alloys (Inconel 600, Incoloy 825)
Carbon steel and alloy steel (A106 B, A333, P91)
Aluminum alloys (6061, 7075)
Copper alloys (C11000, C36000)
Titanium alloys (Ti-6Al-4V)
Element Composition of Common Alloy Pipelines
304 Stainless Steel
| Element content | ||||||||
| Type | Iron (Fe) | Chromium (Cr) | Nickel (Ni) | Carbon (C) | Manganese (Mn) | Silicon (Si) | Phosphorus (P) | Sulfur (S) |
| 304 Stainless Steel | 74.0% -81.0% | 18.0% -20.0% | 8.0% -10.5% | ≤0.08% | ≤2.0% | ≤1.0% | ≤0.045% | ≤0.030% |
316 Stainless Steel
| Element content | ||||||||
| Type | Chromium (Cr) | Sulfur (S) | Nickel (Ni) | Molybdenum (Mo) | Carbon (C) | Manganese (Mn) | Silicon (Si) | Phosphorus (P) |
| 316 Stainless Steel | 16% – 18% | ≤0.030% |
10%-14% |
2% – 3% | ≤0.08% | ≤2% | ≤1.0% | ≤0.045% |
Application of alloy pipelines
- Energy and power: used for high temperature and high pressure fluid and oil and gas transmission, such as P92 alloy used for thermal power plant steam pipeline, P5 alloy steel pipe used for gasoline transportation in the oil extraction industry. HP40 pipeline has strong corrosion resistance and is used for natural gas transportation.
- Chemical and petrochemical: used for conveying corrosive fluids. For example, P22 alloy steel pipe conveys hydrochloric acid and sulfuric acid.
- Aerospace: Titanium alloy seamless pipes are used for fuel transportation sent by rockets.
- Military field: Chromium-molybdenum alloy steel pipes act as power units in the hydraulic system of military armored vehicles.
- Marine field: Duplex steel pipes have strong corrosion resistance and are used in deep sea mining projects.
Maintenance of alloy pipelines
Although alloy pipes have strong performance, daily maintenance is also crucial. Regularly use a neutral cleaning cloth to wipe the surface of the pipe (do not use bleach or chlorine-containing detergents). If there are attachments on the surface, wipe them carefully to avoid scratching the surface of the pipe. The surface moisture should also be wiped dry immediately to avoid electrolyte corrosion. Pay special attention to titanium alloy pipes. Clean the level gauge with clean water or trichloroethylene every month to prevent harmful substances from causing local corrosion and accelerating the aging of the pipe.
The difference between alloy pipe and carbon steel pipe
Different elements: Alloy pipes have more elements than carbon steel pipes, and carbon steel generally does not have a large amount of alloys.
Different chemical properties: The performance of alloy pipes mainly depends on the type and content of alloys, but the performance of carbon steel is mainly the carbon content. Generally, there is no large amount of alloys.
Comparison of the characteristics of alloy pipes and carbon steel pipes
Characteristics of carbon steel pipes: easy processing, low cost and wide application, poor tempering stability, poor permeability, and cannot meet special performance requirements
Characteristics of alloy pipes: difficult processing, high cost, high tempering stability, high hardenability, and can meet special performance requirements
