The key advantage of P22 alloy steel pipes is their 100% recyclability, which aligns with national environmental protection and resource-saving strategies. This makes them a sustainable choice that supports energy efficiency and green development. As a result, government policies actively promote the expansion of high-pressure alloy pipe applications in various industries.
Seamless steel pipes are manufactured using different processes, resulting in two main types: hot-rolled (extruded) and cold-drawn (cold-rolled). Cold-drawn tubes can further be classified into round tubes and special-shaped tubes, depending on their design and application requirements.
**a. Overview of the Manufacturing Process**
- **Hot-rolled (extruded) seamless steel pipe:**
The process starts with a round tube billet, followed by heating, perforation, and then three-roll skew rolling, continuous rolling, or extrusion. After tube removal, sizing or diameter reduction is performed, followed by cooling, straightening, and quality testing such as water pressure tests or flaw detection. Finally, the pipes are marked and stored.
- **Cold-drawn (rolled) seamless steel pipe:**
The process begins with a round tube billet, which is heated, perforated, and headed. It then undergoes annealing, pickling, and oiling or copper plating before being subjected to multiple passes of cold drawing or rolling. After heat treatment and straightening, the pipes are tested hydraulically or inspected for flaws, marked, and stored.
**b. Types of Seamless Steel Pipes Based on Use**
- **GB/T8162-1999 (Structural Seamless Steel Pipe):**
Used mainly for general mechanical and structural purposes. Common materials include carbon steels like 20 and 45, and alloy steels such as Q345, 20Cr, 40Cr, 20CrMo, 30–35CrMo, and 42CrMo.
- **GB/T8163-1999 (Fluid Conveying Seamless Steel Pipe):**
Designed for fluid transportation in engineering and large-scale equipment. Materials include 20 and Q345.
- **GB3087-1999 (Low and Medium Pressure Boiler Seamless Steel Pipe):**
Used in industrial and domestic boiler systems. Typical materials are 10 and 20 steel.
- **GB5310-1995 (High-Pressure Boiler Seamless Steel Pipe):**
Suitable for high-temperature and high-pressure fluid transport in power plants and nuclear facilities. Materials include 20G, 12Cr1MoVG, and 15CrMoG.
- **GB5312-1999 (Ship Boiler Seamless Steel Pipe):**
Applied in marine boilers and superheaters. Common grades are 360, 410, and 460.
- **GB9948-1988 (Petroleum Cracking Seamless Steel Pipe):**
Used in petroleum refining equipment such as boilers and heat exchangers. Materials include 20, 12CrMo, 1Cr5Mo, and 1Cr19Ni11Nb.
- **GB18248-2000 (Gas Cylinder Seamless Steel Pipe):**
Ideal for gas and hydraulic cylinders. Representative materials are 37Mn, 34Mn2V, and 35CrMo.
- **GB/T17396-1998 (Hydraulic Prop Seamless Steel Pipe):**
Used in coal mine hydraulic supports and cylinders. Common materials are 20, 45, and 27SiMn.
- **GB3093-1986 (Diesel Engine High-Pressure Seamless Steel Pipe):**
Typically cold-drawn, used in diesel engine fuel injection systems. Material: 20A.
- **GB/T3639-1983 (Precision Cold-Drawn Seamless Steel Pipe):**
Used where high dimensional accuracy and surface finish are required. Materials include 20 and 45 steel.
- **GB/T3094-1986 (Special-Shaped Cold-Drawn Seamless Steel Pipe):**
Used for structural parts and components. Materials include high-quality carbon and low-alloy steels.
- **GB/T8713-1988 (Precision Inner Diameter Seamless Steel Pipe):**
Used for hydraulic and pneumatic cylinders requiring precise inner diameters. Materials include 20 and 45 steel.
- **GB13296-1991 (Stainless Steel Seamless Pipe for Boilers and Heat Exchangers):**
Used in chemical plants for high-temperature, high-pressure, and corrosion-resistant applications. Materials include 0Cr18Ni9, 1Cr18Ni9Ti, and 0Cr18Ni12Mo2Ti.
- **GB/T14975-2002 (Stainless Steel Structural Seamless Pipe):**
Used in architectural and mechanical structures. Materials include 0-3Cr13, 0Cr18Ni9, and 1Cr18Ni9Ti.
- **GB/T14976-2002 (Stainless Steel Fluid Transport Seamless Pipe):**
Designed for conveying corrosive media. Materials include 0Cr13, 0Cr18Ni9, and 0Cr17Ni12Mo2.
- **YB/T5035-1993 (Automobile Axle Casing Seamless Pipe):**
Used for automobile half-shaft casings. Materials include 45, 45Mn2, and 40Cr.
- **API SPEC5CT-1999 (Casing and Tubing Specification):**
A global standard for oil and gas industry casing and tubing. Materials include J55, N80, P110, and C90. Casing lines the wellbore, while tubing transports oil from the reservoir to the surface.
- **Line Pipe:**
Used to transport oil, gas, or water over long distances. Includes both seamless and welded pipes, with materials like B, X42, X56, X65, and X70.
**Welded Steel Pipe**
Welded steel pipes are made from steel sheets or strips and are categorized based on welding methods: furnace-welded, electric-resistance-welded, and automatic arc-welded. They can also be classified as straight-seam or spiral-welded based on the joint type. These pipes are commonly used for low-pressure fluid transport, including water, gas, air, oil, and steam. A typical material is Q235A grade steel.
- **GB/T3092-1993 (Galvanized Welded Steel Pipe):**
Used for low-pressure fluid transportation, such as water, gas, and steam. Material: Q235A.
- **GB/T14291-1992 (Mine Fluid Transport Welded Steel Pipe):**
Used for mine ventilation and drainage. Materials: Q235A and B.
- **GB/T14980-1994 (Large Diameter Electric Welded Steel Pipe):**
For low-pressure fluid transport, including water, sewage, and gas. Material: Q235A.
- **GB/T12770-1991 (Stainless Steel Welded Pipe for Mechanical Structures):**
Used in machinery, automotive, and furniture components. Materials include 0Cr13, 1Cr17, and 1Cr18Ni9.
- **GB/T12771-1991 (Stainless Steel Welded Pipe for Fluid Transportation):**
Used for transporting low-pressure corrosive media. Materials include 0Cr13, 0Cr19Ni9, and 00Cr17.
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