High Strength Steel Pipe Making Machine
High Strength Steel Pipe Making Machine is made of high strength steel as raw material, through rolling, high frequency welding process made of steel pipe, its yield strength (usually ≥ 355 MPa) and tensile strength is significantly higher than ordinary carbon steel.
High-strength steel is usually used in energy transportation, construction engineering, transportation and some special fields, is one of the core materials of modern industry.
Core Properties of High Strength Steel Pipes
- High strength: High strength is achieved by adding alloying elements (e.g. Mn, Cr, Ni, Mo, V) and heat treatment (e.g. quenching + tempering), with some grades up to X120 (yield strength ≥ 827 MPa).
- Lightweight: thinner wall thickness under the same load, reducing structural weight (e.g. 10%-20% weight reduction for automotive chassis applications).
- Corrosion resistance: some models contain Cu, P and other elements or galvanized / epoxy coating, adapt to marine, chemical and other corrosive environments.
- Low Temperature Toughness: By controlling the sulfur and phosphorus content and grain refinement process, the toughness can be maintained below -40℃ (e.g. Arctic pipeline steel).
How Strength Steel Pipe Making Machine Work?
Pre-treatment of steel strip
- Acid washing: remove the oxide skin (hydrochloric acid concentration 15%-20%, temperature 70-80 ℃).
- Cold Rolling: Thickness tolerance control ± 0.1mm to ensure molding stability.
- Edge milling: Processing bevel (V or I type) to ensure welding fusion.
Roll forming
- Multi-pass progressive molding: the steel strip is gradually bent into tube shape by 8-10 sets of rollers.
- Rebound control: For the characteristics of high strength steel with high modulus of elasticity, overbending compensation design is adopted (e.g. the molding angle is increased by 0.5°-1°).
- Forming precision: Ellipticity ≤ 0.6% D (pipe diameter), ensure welding gap ≤ 0.3mm.
High Frequency Welding (HFW)
High frequency induction heating
- Frequency selection: 100-400 kHz (the greater the plate thickness the lower the frequency).
- Current density: 200-500 A/mm², rapid heating of the strip edge to 1250-1400°C (90% region of the melting point) by skin effect.
Welding parameters
- Extrusion pressure: 20-50 MPa (the larger the pipe diameter or wall thickness, the higher the pressure), extrusion 1.5-3 mm.
- Welding speed: 20-80 m/min (inversely proportional to the wall thickness, such as wall thickness of 6mm speed of about 40 m/min).
- Power matching: adjust the power according to the thickness of the plate, such as 6mm thick steel strip needs 500-600 kW.
Welded seam post-treatment
- Weld seam strengthening technology (seamless weld treatment):
Weld channel shaping and grinding: Scrape off the inner & outer burrs through the system of burr scraping device + roll grinding weld seam, eliminate inner & outer burrs and improve the surface quality Ra≤12.5μm, reduce stress concentration.
- On-line heat treatment: after welding, after air-cooling and then water spray cooling, to reduce the hard and brittle phase of martensite or bainite organization, the formation of ferrite and pearlite organization, so as to ensure the toughness of the pipe, weldability and corrosion resistance.
- Normalizing treatment: The weld is heated 900-950℃ and then air-cooled (by adjusting the cooling rate of the weld in the range of 10℃/s-30℃/s) to eliminate welding residual stresses and improve toughness (e.g., the impact work of X80 steel is ≥200J@-20℃).
- Tempering treatment (Q&T): for ultra-high-strength steel pipe (e.g. X120), quenching (water cooling) + tempering (600-650℃), balancing strength and plasticity.
Finishing and sizing
Cold sizing rolling:
- Sizing: Improve dimensional accuracy (e.g. API standard requires diameter tolerance ±0.75%).
- On-line straightening: Rough straightening of tubes, straightness ≤ 1mm/m
- Off-line straightening: multi-roll straightening machine to eliminate tube bending, straightness ≤ 0.5mm/m.
Quality inspection and control
- Eddy current testing (ECT): There are on-line localized testing of weld seams, as well as off-line coverage of crack detection on the surface of the whole pipe body (frequency 50-200 kHz).
- Ultrasonic Testing (UT): Detects defects such as weld inclusions and unfused welds (sensitivity Φ1.6mm flat-bottomed holes).
- Hydrostatic test: for the final determination of the test, to verify the pressure-bearing capacity (test pressure = 2 times the working pressure, holding pressure 10s without leakage).
Mechanical performance test
- Tensile test: sampling weld and base material, verification of yield strength, tensile strength (such as X70 requirements yield ≥ 485 MPa).
- Charpy impact test: -20 ℃ weld impact work ≥ 40J (API 5L standard).
- Hardness test: HV10≤280 in weld area to avoid brittle fracture.
Surface treatment and packaging
Anti-corrosion coating:
- On-line oiled anti-corrosion
- Off-line galvanized: hot dip galvanized layer thickness ≥65μm (ASTM A53).
- Off-line epoxy spraying: 3PE coating (bottom epoxy + intermediate adhesive + outer polyethylene), adapted to the corrosive environment of buried pipelines.
End protection
- Plastic capping: prevent port damage during transportation.
- Bundle packing: hexagonal bundle, each bundle weight ≤ 5 tons.
Applications for High Strength Steel Pipes
High-strength steel pipes are widely used in core fields such as energy, construction and transportation by virtue of their high-strength, lightweight and corrosion-resistant characteristics.
In energy transportation, X80/X100 grade steel pipe is used in long-distance pipelines such as West-East Natural Gas Pipeline, with wall thickness reduced by more than 10%, which significantly reduces the laying cost; X65 pressure-resistant steel pipe is used in deep-sea oil and gas development, which is resistant to the pressure of 2,000 meters water depth.
In construction engineering, ultra-high-rise buildings (such as the Burj Khalifa) use high-strength square tube concrete columns to reduce weight by 30%, and large-span bridges use HSLA-80 weathering steel to reduce maintenance costs.
In the transportation field, DP1000 duplex steel pipe helps to reduce the weight of new energy vehicles by 40%, and the fatigue life of high-speed rail hollow shafts is improved to ten million times.
Construction machinery, such as crane booms using 1100MPa grade steel to extend the operating radius, wind turbine towers using S460ML steel to support the height of 100 meters.
The future trend focuses on material innovation (medium manganese steel strength of 1.2GPa) and green manufacturing (hydrogen metallurgy carbon reduction of 90%), promoting its breakthroughs in hydrogen energy storage and transportation, deep-sea development and other cutting-edge scenarios, and becoming a core support material for industrial upgrading.
Video Showing Strength Steel Pipe Making Machine
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