Core Cast Steel Components (核心铸钢部件)
Impeller Blades (轴流叶片): The heart of the axial flow pump. They withstand massive dynamic loads and hydraulic thrust, and are highly prone to cavitation and sand erosion. Usually made of high-strength cast stainless steel.
Impeller Hub (叶轮体): The central part that secures the blades, enduring high torque and centrifugal forces.
Guide Vane / Diffuser (导叶体/导叶轮): Located downstream of the impeller, it redirects rotational flow into axial flow and recovers kinetic energy. It experiences high-velocity fluid erosion.
Pump Casing / Pump Bowl (泵体/泵壳): For large-scale or high-head axial flow pumps handling aggressive media, the casing or specific flow segments are made of steel castings to enhance pressure containment.
2. Common Cast Steel Materials & Standards (常用铸钢材质与标准)
| Material Type (材质类型) | GB Standard (国标) | ASTM / AISI Equivalent (美标对照) | Key Characteristics & Applications (特点与应用) |
Carbon Cast Steel (碳素铸钢) | ZG230-450 | ASTM A216 WCB | Moderate strength, excellent weldability. Used for pump casings and guide vanes in clean water or non-corrosive media. |
Martensitic Stainless Steel (马氏体不锈钢) | ZG06Cr13Ni4Mo | ASTM A743 CA6NM | High strength, hardness, and superior cavitation resistance. The premier choice for large-scale pump blades. |
Austenitic Stainless Steel (奥氏体不锈钢) | ZG0Cr18Ni9 ZG0Cr18Ni12Mo2 | ASTM A743 CF8 ASTM A743 CF8M (316) | Excellent corrosion resistance. Ideal for chemical, desalination, or highly corrosive environments. |
Duplex Stainless Steel (双相不锈钢) | ZG03Cr25Ni6Mo3CuN | ASTM A890 CD4MCu / Grade 4A | Combines high strength with exceptional resistance to pitting and stress corrosion. Used in high-sediment, seawater, or severe-duty applications. |
3. Manufacturing & Quality Control Key Points (工艺与质控要点)
3.1 Casting & Geometry (铸造与几何精度)
Precision Patternmaking: Impeller blades require CNC-machined patterns (wooden or plastic) combined with resin-bonded sand molding to ensure precise 3D hydrodynamic blade profiles, minimizing hydraulic losses.
Refining: For stainless steel castings (like CA6NM), secondary refining via AOD (Argon Oxygen Decarburization) or VOD (Vacuum Oxygen Decarburization) is critical to strictly control Carbon, Hydrogen, and Oxygen levels, preventing porosity and hot tearing.
3.2 Heat Treatment (热处理)
Carbon Steel: Typically undergoes Normalizing & Tempering (N+T) or Annealing to relieve stress.
CA6NM (Martensitic): Requires a strict Quality Heat Treatment—Liquid Quenching (or Air Cooling) followed by Double Tempering to achieve a fine tempered martensite structure with retained austenite, ensuring high impact toughness and cavitation fatigue life.
3.3 Non-Destructive Testing (NDT) & Balancing (无损检测与平衡)
⚠️ Quality Redline: Blade failure during operation can lead to catastrophic pump destruction.
Surface Inspection: 100% Magnetic Particle Testing (MT) or Liquid Penetrant Testing (PT) on blade surfaces to detect cracks.
Volumetric Inspection: Ultrasonic Testing (UT) or Radiographic Testing (RT) on critical high-stress areas to detect internal defects.
Dynamic Balancing: The fully machined impeller assembly must undergo strict Static and Dynamic Balancing tests to eliminate vibration.