St35 Tubes & Pipes Manufacturer & Supplier - USA Piping Solution

USA Piping Solution is a key national provider of St35 Tubes & Pipes, manufactured primarily according to the DIN 2391 standard for seamless precision steel tubes. This specific grade represents a reliable choice for numerous mechanical and structural applications demanding dimensional accuracy and consistent properties. We maintain substantial inventories across the United States, ensuring dependable access to certified St35 Tubes & Pipes. For quality materials coupled with knowledgeable support and efficient delivery, consider USA Piping Solution your trusted source.

What are St35 Tubes & Pipes?

For hydraulic systems to function safely and effectively, the tubing used must precisely match the established standards. USA Piping Solution provides SAE J525 Welded Hydraulic Tubing manufactured to meet these rigorous technical parameters.

Key Technical Details

Category	Details
Governing Standard	SAE J525 (Welded and Cold Drawn Low Carbon Steel Tubing Annealed for Bending and Flaring). Related standards like NFPA T3.15.67.1 might also be referenced.
Base Material	Low Carbon Steel, typically within the 1006 to 1018 grade range.
Production Route	Begins with Electric Resistance Welding (ERW), followed by normalizing heat treatment, a significant cold working (drawing) step, and a final annealing stage.
Size Range (Outside Diameter - OD)	Commonly stocked in sizes from 1/4 inch (0.250") OD up to 2 inches OD.
Wall Thickness Options	Offered in various wall thicknesses appropriate for hydraulic pressure levels, generally ranging from about 0.028" up to 0.120" or slightly more in larger diameters.
Typical Form	Supplied primarily as Round tubing.
End Condition	Standard supply is with Plain Ends (PE), cut square, suitable for flaring tools, brazing, or use with appropriate compression fittings.
Standard Lengths	Frequently stocked in 20-foot nominal lengths; custom cut-to-length pieces are readily available.
Dimensional Tolerances (Defined by SAE J525)	OD/ID: Held to relatively tight tolerances (e.g., +/-0.002" to +/-0.004" on OD depending on size) to ensure compatibility with standard fittings. Wall Thickness: When OD and nominal wall are specified, wall thickness variation is typically controlled to within +/- 10%. Straightness: Conforms to standard straightness requirements for quality tubing.
Surface Quality	A key feature is the bright, clean finish on both the outside and inside surfaces, important for minimizing contamination in hydraulic systems.

Key characteristics stem from its specification and manufacturing:

• DIN Standard: It originates from the Deutsches Institut für Normung (German Institute for Standardization), setting it apart from ASTM or EN specifications, although functional equivalents often exist.
• Seamless Production: Starting from solid steel billets, these tubes are manufactured without any longitudinal weld, ensuring structural homogeneity throughout the tube wall.
• Precision Focus: Often produced using cold finishing methods (like cold drawing), which imparts tight dimensional tolerances on the outside diameter, inside diameter, and wall thickness. This precision minimizes subsequent machining needs.
• St35 Grade Steel: This designates a low-carbon steel (Carbon ≤ 0.17%) known for its excellent ductility and formability, particularly when supplied in an annealed (GBK) or normalized (NBK) condition. It also offers good weldability.

Engineers and designers select St35 Steel Tubes when their project demands the reliability of seamless construction combined with the close tolerances and smooth surfaces characteristic of precision tubing. It's a widely used DIN 2391 St35 Pipe grade for high-quality mechanical components.

St35 Tubing Specifications

Adhering to the specific technical parameters of DIN 2391 is crucial for the successful application of St35 tubing. USA Piping Solution provides materials that conform fully to these requirements.

Technical Specifications

Specification	Details
Governing Standard	DIN 2391 (Seamless Precision Steel Tubes); EN 10305-1 may also apply
Grade Designation	St35 (Material number 1.0308 under EN standards)
Manufacturing Method	Seamless tubing as required by DIN 2391
Finishing Process	Cold Finished (Cold Drawn or Cold Rolled) Final condition codes include: BK: Cold Finished (Hard / As-drawn) BKW: Cold Finished (Soft) – lightly worked post-annealing BKS: Cold Finished (Stress Relieved) GBK: Annealed after cold finishing NBK: Normalized after cold finishing
Size Range Capabilities (OD)	Approx. 4 mm to 190 mm OD; typical stock focuses on hydraulic and mechanical sizes
Wall Thickness Options	Ranges from 0.5 mm to 15 mm or more depending on OD
Length Options	Standard mill lengths (e.g., 4–6 meters), random lengths, or precision cut-to-length up to 6000 mm+
Dimensional Tolerances	Tight OD and wall tolerances per DIN 2391; significantly more precise than standard pipes

These compositional limits are fundamental to the material's intended function.

Chemical Composition and Mechanical Properties

The performance profile of St35 Tubes & Pipes – its strength, ductility, weldability, and machinability – is a direct consequence of its specified low-carbon steel chemistry and the mechanical properties developed through processing.

Chemical Composition (% by Weight)

Element	St35 Requirement (%)	Influence on Material Behavior
Carbon (C)	≤ 0.17	Low carbon content ensures excellent ductility and weldability.
Silicon (Si)	≤ 0.35	Present from steelmaking process, acts as deoxidizer.
Manganese (Mn)	≥ 0.40	Contributes to strength and hardness.
Phosphorus (P)	≤ 0.025	Impurity element, kept low for better toughness and weld quality.
Sulfur (S)	≤ 0.025	Impurity element, limited for improved ductility and surface quality.

This composition yields a material known for its good formability and reliability in general mechanical use.

Mechanical Properties (Condition Dependent)

The mechanical strength and ductility of St35 tubing vary considerably based on the final delivery condition (the thermal treatment applied after cold finishing). DIN 2391 provides minimum values for common conditions:

Property	Condition BK (Cold Finished/Hard)	Condition GBK (Annealed)	Condition NBK (Normalized)	Units	Interpretation
Tensile Strength	480 min	315 min	340 - 470 (Range)	MPa	BK condition is strongest due to work hardening; GBK is softest; NBK is intermediate.
Yield Strength	Not Specified (Implied High)	Not Specified (Implied Low)	235 min	MPa	Only specified for the Normalized condition; higher in BK, lower in GBK.
Elongation (A5)	6% min	35% min	25% min	%	Ductility is lowest in BK condition, highest in GBK, reflecting formability limits.

Understanding Delivery Conditions:

• BK (Cold Finished/Hard): Offers the highest strength due to cold working but has minimal ductility. Best for applications where strength is key and little forming is needed.
• GBK (Annealed): Provides maximum ductility, making it ideal for severe bending, flaring, or other forming operations. Strength is lowest.
• NBK (Normalized): Offers a balance – better ductility and toughness than BK, while retaining higher strength than GBK. A common choice for general mechanical components.
• BKS (Stress Relieved): Reduces internal stresses from cold work with minimal impact on hardness/strength compared to BK.
• BKW (Soft): Lightly cold worked after annealing; properties intermediate between GBK and BK.

Choosing the right delivery condition is essential to match the tubing's properties to the demands of fabrication and final application.

Manufacturing Process: Seamless Precision Tubing Explained

Producing St35 Seamless Pipes to the precision standards of DIN 2391 involves meticulous manufacturing steps designed to achieve tight tolerances and smooth surfaces:

1. Billet Preparation: High-quality solid steel billets corresponding to the St35 chemical composition are selected.
2. Hot Forming (Initial Stage): The billets are heated to high temperatures and then pierced using methods like rotary piercing to create a seamless hollow shell. This rough tube might undergo some initial hot rolling to approach the desired size range.
3. Surface Conditioning & Preparation: Before cold finishing, the hot-formed tube surface is typically cleaned (e.g., via pickling or shot blasting) to remove scale and prepare it for drawing. Proper preparation is vital for a good cold-drawn finish.
4. Cold Drawing: This is the defining process for precision tubing. The prepared seamless hollow is pulled through one or more hardened steel dies at room temperature. An internal mandrel is often used concurrently to control the inside diameter and wall thickness precisely. Each pass reduces the tube's dimensions, elongates it, refines the surface finish, and increases its strength/hardness through work hardening.
5. Thermal Treatment (Annealing/Normalizing): Depending on the specified final condition (GBK, NBK, etc.), the cold-drawn tube undergoes a controlled heat treatment cycle in a furnace. Annealing (GBK) fully softens the material for maximum ductility. Normalizing (NBK) refines the grain structure for a balance of properties. Stress relieving (BKS) reduces internal stresses. If ordered as BK, no final heat treatment is applied.
6. Finishing & Inspection: Final steps include straightening to meet tight tolerances, cutting to the required lengths, final cleaning or application of protective coatings if specified, and comprehensive inspection covering dimensions, surface quality, and any required mechanical testing based on the delivery condition.

This sequence results in the high-quality, dimensionally accurate St35 Steel Tubes specified under DIN 2391.

Benefits of St35 Tubes & Pipes

Choosing St35 Tubes & Pipes according to DIN 2391 offers several distinct advantages for engineering applications:

• High Dimensional Accuracy: Cold finishing processes enable very tight tolerances on outside diameter, inside diameter, and wall thickness, reducing the need for costly secondary machining.
• Excellent Surface Finish: Both internal and external surfaces are significantly smoother and cleaner compared to hot-finished products, beneficial for fluid flow, sealing surfaces, or aesthetic requirements.
• Good Formability (in Annealed/Normalized Conditions): The low-carbon St35 grade, particularly when supplied annealed (GBK) or normalized (NBK), exhibits excellent ductility, allowing for complex bending and forming operations.
• Reliable Strength and Consistency: While properties vary with condition, the seamless manufacturing and controlled processing ensure consistent mechanical properties suitable for many general engineering components.
• Good Weldability: The low carbon content makes St35 steel readily weldable using common welding techniques, facilitating assembly.
• Versatility: Its balance of properties makes it suitable for a wide range of mechanical, structural, and hydraulic line applications (check pressure ratings).

Applications and Industries Served

The precision, formability, and reliable properties of DIN 2391 St35 Pipes lead to their use in a variety of demanding applications:

• Hydraulic and Pneumatic Systems: Widely used for hydraulic lines (often in the NBK condition for formability and strength), cylinder barrels (requiring honing after receipt), pistons, and related fluid power components where precision and smooth internal surfaces are important.
• Automotive Manufacturing: Employed in producing components like steering systems, suspension parts, fuel injection lines (check compatibility), drive shafts, and structural elements requiring tight tolerances.
• Mechanical Engineering: Serves as stock material for precision shafts, axles, rollers, bushings, machine frames, and various custom-machined parts requiring dimensional accuracy.
• General Construction and Structural Uses: Used in precision structural applications, frameworks, supports, and architectural elements where tolerances and finish are critical.
• Furniture Manufacturing: Utilized in high-quality metal furniture frames and components requiring a smooth finish and consistent dimensions.
• Instrumentation Lines: Suitable for certain types of instrumentation and control lines where precision and cleanliness are needed.

St35 tubing is chosen when the application demands more than standard pipe tolerances and surface quality, providing a reliable foundation for high-performance components.

St35 Tubing Size Chart and Weight Chart

This reference chart provides nominal dimensions and approximate weights for common sizes of round St35 Tubes & Pipes. Use these figures for estimation; actual weights depend on exact dimensions within tolerance.

OD (mm)	Wall (mm)	ID (mm)	Weight ( kg/m )	Weight (lbs/ft)	Notes
10.0	1.0	8.0	0.23	0.15	Thin Wall
10.0	1.5	7.0	0.32	0.22
15.0	1.5	12.0	0.51	0.34
15.0	2.0	11.0	0.65	0.44
20.0	1.5	17.0	0.69	0.46
20.0	2.5	15.0	1.08	0.73
25.0	2.0	21.0	1.15	0.77	Common Size
25.0	3.0	19.0	1.65	1.11
30.0	2.0	26.0	1.40	0.94
30.0	3.0	24.0	2.01	1.35
38.0	2.5	33.0	2.23	1.50
38.0	4.0	30.0	3.44	2.31
45.0	3.0	39.0	3.11	2.09
45.0	5.0	35.0	4.90	3.29
50.0	4.0	42.0	4.60	3.09	Common Size
50.0	6.0	38.0	6.59	4.43
60.0	5.0	50.0	6.87	4.62
60.0	8.0	44.0	10.4	7.00	Heavy Wall
70.0	6.0	58.0	9.67	6.50
80.0	7.0	66.0	12.8	8.60
100.0	8.0	84.0	18.3	12.3

Note: Weight calculations are based on nominal dimensions and standard steel density (approx. 7.85 g/cm³). Actual weights will vary within tolerance limits.

Certifications and Compliance

Confirmation that St35 Tubes & Pipes meet the requirements of DIN 2391 and other relevant standards is essential for quality assurance. USA Piping Solution ensures materials are provided with appropriate verification.

• DIN 2391 Conformance: Tubing supplied is certified by the manufacturer to comply with the chemical composition, seamless manufacturing, dimensional tolerance, and (where applicable) mechanical property requirements for Grade St35 as stipulated in DIN 2391.
• Mill Certification: Typically accompanied by Mill Test Certificates (MTCs), often formatted according to EN 10204 (e.g., Type 3.1), which provide traceability via heat number and confirm chemical analysis. Mechanical test results corresponding to the specific delivery condition (BK, GBK, NBK) are included when applicable based on the order.
• ISO 9001 Procedures: Our quality management system adheres to ISO 9001 principles, ensuring consistent processes for supplier verification, material handling, and documentation.
• Standard Marking: Tubing is marked according to DIN standards and industry practice, usually including:
• Manufacturer's identifier
• Standard (DIN 2391) and Grade (St35)
• Dimensions (OD x Wall)
• Delivery Condition Code (e.g., NBK)
• Heat Number or Traceability Code.

This documentation provides the necessary confirmation of material quality and conformity for engineering records and downstream manufacturing.

Why Choose USA Piping Solution for St35 Tubes & Pipes?

Selecting a supplier capable of reliably sourcing and delivering DIN-standard tubing is important. USA Piping Solution offers compelling reasons to be your source for St35 Tubes & Pipes:

• Expertise with International Standards: Our team is familiar with DIN 2391 and the specific characteristics of St35 tubing, including the critical differences between delivery conditions.
• Strong Sourcing Network: We maintain relationships with qualified domestic and international mills specializing in precision seamless tubing, enabling efficient sourcing of DIN standard materials.
• Inventory Management: While holding broad stocks, we excel at accessing specific requirements like St35 through our established supply chain, ensuring timely availability.
• Efficient Logistics: Our nationwide distribution capabilities ensure reliable and prompt delivery of materials directly to your facility or project site.
• Quality Assurance: We prioritize sourcing from reputable manufacturers and ensure all materials are accompanied by proper mill certification confirming compliance.
• Processing Services: We offer value-added services, particularly precision cutting to length, to meet your exact component specifications.
• Dedicated Support: Our sales and technical support teams are committed to providing responsive service, accurate information, and efficient handling of all inquiries and orders.

Related Products

In addition to St35 tubing, USA Piping Solution provides a diverse range of seamless tubes and pipes meeting various standards:

Understanding the specific standard and grade requirements for your application is crucial. Our team can help compare these options.

For applications requiring the precision, smooth finish, and reliable performance of St35 Tubes & Pipes manufactured to DIN 2391 standards, partner with USA Piping Solution. We offer certified St35 Seamless Pipes and St35 Steel Tubes, supported by extensive sourcing capabilities and dedicated customer service. Ensure the quality and accuracy of your mechanical components with materials from a dependable supplier.

Contact USA Piping Solution today to discuss your St35 Tubes & Pipes requirements and receive a prompt, competitive quotation.

Request Your St35 Tubing Quote Now!