High-Strength Carbon Steel Double Internal Thread Hollow Pipe for Machinery

I. Product Structure and Material Properties

1. Structural Design

   Made of Q235 carbon steel as the base material, both ends are precision-turned to form internal threads (such as Rc3/8, M4, etc.), forming a straight-through hollow pipe body. Some products adopt double crimping connection technology, with internal and external plastic coatings to enhance sealing and corrosion resistance. For example, plastic-coated carbon steel double crimping pipe fittings feature a composite structure of internal and external plastic protective layers + welded steel pipes, integrating the rigidity of steel pipes and the corrosion resistance of plastics, overcoming the defects of traditional carbon steel (easy to rust) and plastic pipes (low strength).

2. Material Performance

   • High Strength: The carbon steel material has a tensile strength of 375-500MPa, capable of withstanding high pressure up to 20MPa (e.g., oil circuit switches in hydraulic systems).
   • Corrosion Resistance: Through plastic coating (polyethylene/epoxy resin), galvanizing, chrome plating, or phosphating treatment, it can resist erosion from acids, alkalis, salt spray, and humid environments. For instance, plastic-coated pipe fittings show no obvious corrosion after 50 days in a neutral salt spray test, far exceeding the 12-day tolerance limit of galvanized pipes.
   • Machinability: Carbon steel is easy to cut and weld, suitable for customized processing. For example, M4*10mm internal threaded pipes used in lighting accessories have an outer diameter of 5.3mm and lengths ranging from 10mm to 250mm.

II. Core Advantages

1. Connection Reliability

   The internal thread design ensures high-precision sealing, and the double crimping structure achieves dual locking through metal and rubber sealing rings, realizing "one-time installation, long-term leak prevention"—especially suitable for scenarios with strict sealing requirements such as fire protection and chemical industries.

2. Easy Installation

   • Weld-free: Double crimping connection eliminates the need for fire, avoiding safety hazards and skill dependence of traditional welding, and improving installation efficiency by over 30%.
   • Strong Compatibility: Compatible with various connectors (e.g., ferrule-type, threaded), enabling quick integration into existing pipeline systems.

3. Environmental Adaptability

   • Wide Temperature Range: Plastic-coated pipe fittings can withstand temperature differences from -30℃ to 100℃, while galvanized pipe fittings are suitable for normal temperature environments.
   • Environmental Friendliness: The plastic coating uses food-grade materials, meeting drinking water transportation standards and avoiding "red/yellow water" pollution problems of traditional carbon steel pipes.

III. Application Fields

1. Pipeline Systems

   • Building water supply and drainage, fire sprinkler systems (DN20-DN50 specifications).
   • Hydraulic oil circuit control (e.g., 20MPa high-pressure oil circuit switches in mining machinery and engineering machinery).

2. Hardware and Lighting Accessories

   • Lighting bracket connections (e.g., M4*10mm internal threaded pipes with outer diameters of 4.7-5.3mm), with hollow structures facilitating wiring and joint fixing.
   • Detachable components of furniture and sports equipment (e.g., connecting shafts of strollers and bicycles).

3. Industrial Equipment

   • Hydraulic hard pipes for automobiles and ships (DIN2391 standard precision steel pipes with outer diameters of Φ4-76mm).
   • Corrosion-resistant pipelines for chemical equipment (plastic-coated pipe fittings can resist strong acids and alkalis).

IV. Specifications and Technical Parameters

V. Manufacturing Process and Quality Control

1. Production Process

   Raw materials (carbon steel coils/pipes) → cold drawing/hot rolling forming → turning internal threads → surface treatment (plastic coating/galvanizing, etc.) → non-destructive testing (pressure testing, salt spray testing) → packaging and delivery. For example, precision hydraulic steel pipes undergo 12 processes such as pickling, cold rolling, and phosphating to ensure no oxide layers on inner and outer walls, with precision reaching ±0.05mm.

2. Quality Assurance

   • Adopts ISO 9001 quality management system, with key processes (e.g., plastic coating curing temperature control) monitored throughout.
   • Hydraulic pipe fittings must pass 20MPa pressure resistance testing and 500-hour salt spray testing to ensure long-term reliability.