Carbon Steel U-Bolt — Factory Direct Supplier | Huaxia-Steel
Carbon steel U-bolts are U-shaped fasteners with threaded ends, designed to secure pipes, tubes, conduits, cables, and round bars to supporting structures. The name comes from their distinctive U-shape — a curved body with two parallel threaded legs that pass through pre-drilled holes in a mounting plate or channel and are secured with hex nuts. U-bolts are among the most versatile and widely used pipe support components in industrial, commercial, and marine applications.
Huaxia-Steel supplies carbon steel U-bolts manufactured from ASTM A307, A193, A36, and equivalent grades, in diameters from M6 to M36 (1/4″ to 1-1/2″) and pipe sizes from 1/4″ to 24″ (DN8 to DN600). All our U-bolts are produced from certified carbon steel round bar with hot-bend or cold-bend forming, precision threading, and complete dimensional inspection.
Product Overview
U-bolts are specified by three principal dimensions:
- Inside diameter (ID) or pipe size: The inside width of the U-bolt, which should be slightly larger than the outside diameter of the pipe being supported. For standard pipes, U-bolts are sized to fit the pipe’s nominal diameter — e.g., a “2-inch U-bolt” fits 2-inch NPS pipe (actual OD 60.3mm).
- Thread diameter (rod diameter): The diameter of the threaded legs. Standard sizes range from M6 (1/4″) for small tubing to M36 (1-1/2″) for large pipe sizes.
- Leg length (thread length): The length of the threaded portion extending beyond the pipe. Must be long enough to pass through the supporting steel, washers, and allow full nut engagement.
Common U-Bolt Types:
- Round bend U-bolt: Standard type with a semi-circular bend matching the pipe OD. Used for securing round pipe and tube to flat surfaces, beams, or channels.
- Square bend U-bolt: A rectangular shape with 90-degree bends, used to secure square or rectangular hollow sections (SHS/RHS) or bundles of cables.
- Long tangent U-bolt: Extended straight sections between the curved top and the threaded legs, used where the U-bolt must pass through thick insulation or reach across wide flanges.
- Custom bend U-bolt: Non-standard shapes per customer drawings — V-bend, semi-elliptical, multiple bends — for specialized applications.
Standard Dimensions
Round Bend U-Bolts for Standard Pipe (ASTM A53 / A106)
| Pipe Size (NPS) | Pipe OD (mm) | U-Bolt ID (mm) | Thread Dia. | Typical Leg Length (mm) | Approx. Weight (kg) |
|---|---|---|---|---|---|
| 1/4″ (DN8) | 13.7 | 15 | M6 (1/4″) | 50 | 0.04 |
| 1/2″ (DN15) | 21.3 | 23 | M8 (5/16″) | 60 | 0.08 |
| 3/4″ (DN20) | 26.7 | 28 | M8 (5/16″) | 65 | 0.10 |
| 1″ (DN25) | 33.4 | 35 | M10 (3/8″) | 75 | 0.15 |
| 1-1/4″ (DN32) | 42.2 | 44 | M10 (3/8″) | 80 | 0.20 |
| 1-1/2″ (DN40) | 48.3 | 50 | M12 (1/2″) | 90 | 0.28 |
| 2″ (DN50) | 60.3 | 63 | M12 (1/2″) | 100 | 0.35 |
| 2-1/2″ (DN65) | 73.0 | 76 | M12 (1/2″) | 110 | 0.42 |
| 3″ (DN80) | 88.9 | 92 | M16 (5/8″) | 120 | 0.70 |
| 4″ (DN100) | 114.3 | 118 | M16 (5/8″) | 140 | 0.90 |
| 5″ (DN125) | 141.3 | 145 | M20 (3/4″) | 160 | 1.40 |
| 6″ (DN150) | 168.3 | 172 | M20 (3/4″) | 180 | 1.70 |
| 8″ (DN200) | 219.1 | 223 | M22 (7/8″) | 200 | 2.50 |
| 10″ (DN250) | 273.0 | 278 | M24 (1″) | 230 | 3.80 |
| 12″ (DN300) | 323.8 | 329 | M27 (1-1/8″) | 260 | 5.50 |
| 16″ (DN400) | 406.4 | 413 | M30 (1-1/4″) | 300 | 8.00 |
| 20″ (DN500) | 508.0 | 516 | M36 (1-1/2″) | 350 | 13.00 |
| 24″ (DN600) | 610.0 | 618 | M36 (1-1/2″) | 400 | 16.00 |
All dimensions are typical. Custom IDs, thread diameters, and leg lengths are available. Contact us for non-standard pipe sizes (DIN, JIS, or custom OD).
Available Material Grades
| Grade | Standard | Yield (MPa) | Tensile (MPa) | Typical Application |
|---|---|---|---|---|
| ASTM A307 Gr A | A307 | — | 415 min | General pipe support, non-critical |
| ASTM A36 | A36/A36M | 250 | 400-550 | Structural pipe supports |
| Q235B | GB/T 700 | 235 | 370-500 | Utility piping, low-pressure |
| ASTM A193 B7 | A193 | 725 | 860 min | High-temperature, critical service |
| SS400 | JIS G3101 | 245 | 400-510 | General industrial, Japan/Asia standard |
| S235JR | EN 10025-2 | 235 | 360-510 | European standard general use |
For the vast majority of pipe support applications, A307 Gr A or Q235B U-bolts provide sufficient strength at an economical price. A193 B7 is specified when U-bolts are subjected to high temperatures (above 350°C) or when the design requires higher strength materials — such as in steam piping supports or high-pressure pipe restraint systems.
Manufacturing Process
- Material selection: Carbon steel round bar cut to length per the developed length of the U-bolt (straight sections + bend allowance).
- Bending: Cold bending on hydraulic or CNC benders with mandrel support for small diameters (M6-M16). Hot bending for larger diameters (M20 and above) or tight bend radii to avoid cracking. The bend radius is controlled to avoid excessive thinning of the outer surface.
- Thread rolling or cutting: Threads are roll-formed (preferred for diameters up to M20) or cut on CNC lathes. Rolled threads provide superior fatigue resistance and surface finish.
- Trimming and chamfering: Leg ends trimmed to length and chamfered for easy nut starting.
- Surface finishing: As-rolled/machined (self-color), electro-galvanized, hot-dip galvanized (ASTM A153), or painted per customer specification.
- Inspection: Dimensional check (ID, leg spacing, thread length, leg length), thread gauging, visual inspection, coating thickness (for galvanized).
Applications
- Pipe supports and restraints: The primary application — securing pipes to structural steel, pipe racks, equipment skids, and building structures. U-bolts prevent pipe movement from thermal expansion, vibration, wind, and seismic loads when used with appropriate guides and anchors.
- Tube and conduit supports: Electrical conduits, instrument tubing, hydraulic lines, pneumatic tubing — often with a plastic or rubber liner between the U-bolt and the tube to prevent galvanic corrosion and abrasion.
- Cable management: Securing cable trays, ladder racks, and bundled cables in industrial and marine environments.
- Automotive: Leaf spring U-bolts (high-strength, often heat-treated), exhaust system clamps, roll cage mounting.
- Marine and offshore: Pipe supports on vessels, platforms, and FPSOs — typically hot-dip galvanized or stainless steel for corrosion resistance in marine atmospheres.
- Pole and mast mounting: Antenna mounts, lighting poles, traffic signal poles — U-bolts provide a simple, adjustable clamping mechanism to round poles.
- Agricultural and construction equipment: Hydraulic cylinder mounting, axle attachment, frame cross-member connections.
U-Bolt Liners and Accessories
For applications where the U-bolt contacts the pipe or tube directly, we supply compatible accessories:
- U-bolt with plastic liner (PVC or HDPE): Prevents metal-to-metal contact, reduces galvanic corrosion (especially important for dissimilar metal contact — e.g., carbon steel U-bolt on stainless steel pipe), and cushions against vibration.
- Rubber-lined U-bolt (EPDM or Neoprene): For high-temperature applications where plastic liners would soften. EPDM rated to 120°C, Neoprene to 100°C, silicone to 200°C.
- Saddle clamps: A formed steel plate that sits between the U-bolt and the pipe, distributing clamping force over a larger area. Recommended for thin-wall pipe (SCH 10 and below) and insulated pipe.
- U-bolt with roller support: Allows axial pipe movement for thermal expansion while providing vertical support — used in long straight pipe runs.
Surface Finish Options
| Finish | Standard | Coating Thickness | Corrosion Class |
|---|---|---|---|
| Self-color (black) | As-manufactured | N/A | Indoor only (C1) |
| Electro-galvanized | ASTM B633 Fe/Zn 8 | 8-12 μm | Indoor, mild (C1-C2) |
| Hot-dip galvanized | ASTM A153 Class C | 45-55 μm (avg) | Outdoor, industrial (C3-C4) |
| Zinc-rich paint | ISO 12944 | 40-60 μm | Industrial, marine (C4-C5) |
| Sherardizing | ISO 17668 | 30-50 μm | Threaded components, even coating |
Quality Assurance
- Raw material traceability to mill certificate (MTC) per applicable ASTM, EN, or GB standard.
- Dimensional inspection: 100% for critical dimensions — ID, thread diameter, leg length, leg spacing.
- Thread gauging: GO/NO-GO ring gauges per ASME B1.2 (UNC) or ISO 1502 (metric).
- Bend quality: Visual inspection for cracks, necking, excessive thinning, or flattening at the bend.
- Coating inspection: Magnetic thickness gauge per ASTM B499 for galvanized/plated U-bolts.
- Optional tensile testing: Proof load or full-section tensile testing per ASTM A370 for critical applications.
- Optional NDT: Magnetic particle testing of the bent section for surface cracking (recommended for diameters M20 and above with tight bend radii).
Packaging and Shipping
- U-bolts packed in plywood cases or cartons, sorted by size and pipe schedule
- Threads protected with plastic caps or VCI paper
- Nuts and washers supplied as matched sets — typically 2 hex nuts + 2 flat washers per U-bolt
- Hot-dip galvanized U-bolts packed with separators to prevent zinc damage
- Custom labeling and color coding available
- FCL container, LCL consolidation, or air freight for urgent orders
- Loading port: Tianjin, Shanghai, Ningbo
- Standard lead time: 1-2 weeks for stock sizes; 3-5 weeks for custom dimensions
Why Choose Huaxia-Steel?
- Comprehensive size range: From M6 instrument tubing clamps to M36 heavy pipe supports — one supplier for all your U-bolt requirements.
- Precision forming: CNC bending ensures consistent ID, leg spacing, and bend radius across production batches.
- Custom manufacturing: Special IDs, non-standard pipe sizes (DIN, JIS), extended leg lengths, square bend, long tangent — built to your drawings.
- Corrosion protection options: Self-color, electro-galvanized, hot-dip galvanized, painted — we recommend the right finish for your environment.
- Complete sets: U-bolts supplied with matching hex nuts, flat washers, and spring washers where specified.
- Global shipping experience: Regular shipments to the Middle East, Southeast Asia, Africa, Europe, and the Americas.
Send us your U-bolt requirements now. Provide the pipe size, thread diameter, leg length, material grade, surface finish, and quantity — and receive a competitive quotation within one business day. For non-standard dimensions, attach your drawing for a custom quote.
