Alloy pipes are a type of seamless steel pipe, known for their superior performance compared to ordinary seamless steel pipes. This is because they contain higher levels of chromium, which significantly enhances their resistance to high and low temperatures, as well as corrosion. These properties make them far superior to seam steel pipes, leading to their widespread use in industries such as petroleum, aerospace, chemical processing, power generation, boiler systems, and military applications.
When it comes to calculating the weight of alloy pipes, the formula used is:
**(Outer diameter - Wall thickness) × Wall thickness × 0.02483 = Weight per meter**.
Common materials used in alloy tubes include: 16-50Mn, 27SiMn, 20-40Cr, 12-42CrMo, 16Mn, 12Cr1MoV, T91, 27SiMn, 30CrMo, 15CrMo, 20G, Cr9Mo, 10CrMo910, 15Mo3, 15CrMoV, 35CrMoV, and 45CrMo. These materials are selected based on their mechanical strength, thermal stability, and corrosion resistance.
Alloy tubes can be classified based on their application. For example, palladium alloy tubes are specifically designed for hydrogen purification. The process involves passing impure hydrogen into one side of the palladium tube at temperatures between 300°C and 500°C. Once inside, hydrogen molecules are adsorbed onto the surface of the tube. Palladium has a unique ability to form unstable bonds with hydrogen due to its incomplete 4d electron layer. This allows hydrogen to be ionized into protons, which then pass through the palladium lattice. On the other side, these protons recombine with electrons to form pure hydrogen gas. Since other gases cannot pass through, this method effectively produces high-purity hydrogen.
However, pure palladium is not suitable for long-term use due to its poor mechanical properties, susceptibility to oxidation at high temperatures, and tendency to deform or embrittle. To overcome these issues, small amounts of elements from Group IB and Group VIII (such as silver) are added to create palladium alloys. These alloys improve mechanical strength and thermal stability. In high-quality carbon structural and alloy structural steel pipes, silver typically makes up 20–30% of the composition, while other elements like gold are present in smaller quantities (<5%).
The hydrogen permeation rate through palladium alloys depends on several factors, including temperature, membrane thickness, and pressure difference across the membrane. Increasing temperature and pressure, or reducing membrane thickness, can enhance permeability. However, higher temperatures may reduce the tensile strength of the membrane, so the operating temperature is usually kept around 450°C. Certain impurities, such as mercury, arsenic, halides, oil vapor, sulfur compounds, ammonia, and dust, can poison the palladium and damage its performance.
In addition to palladium-based alloys, there are also ABS and PC/ABS alloy pipes used in building water supply and air conditioning systems. These materials are favored for their durability, ease of installation, and versatility. They are commonly used in vertical water supply risers and central air conditioning piping. PC/ABS alloys are also widely used in automotive manufacturing for exterior components like wheel covers, mirror housings, and taillight covers, thanks to their excellent molding properties and impact resistance.
As an essential component in steel products, alloy pipes are broadly categorized into two types: seamless steel pipes made from round billets, and welded steel pipes produced from plates or strips. Each type has its own advantages depending on the application requirements, such as pressure resistance, cost-effectiveness, and ease of fabrication.
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