St37 Seamless Tubes Manufacturer & Supplier – USA Piping Solution

USA Piping Solution is a recognized national source for St37 Seamless Tubes, commonly produced according to the DIN 2391 standard for precision seamless steel tubes. This grade represents a versatile low-carbon steel option valued for its formability and reliability in various mechanical and structural contexts. We facilitate access to certified St37 Seamless Tubes through our comprehensive inventory network across the United States, ensuring timely material availability. For dependable sourcing, technical assistance, and efficient delivery, consider USA Piping Solution your partner for St37 requirements.

What are St37 Seamless Tubes?

The designation St37 Seamless Tubes primarily identifies seamless precision steel tubes manufactured under the German standard DIN 2391, using Grade St37 steel. This standard specifically targets applications where dimensional accuracy, smooth surface finish, and defined mechanical properties are paramount. Unlike typical pipe standards focused on pressure capacity, DIN 2391 and its St37 grade are oriented towards mechanical engineering components, automotive parts, and precise structural elements.

Several key factors define this tubing:

• DIN Specification: Adherence to DIN 2391 (Deutsches Institut für Normung) ensures specific German industrial standards are met, which may differ from ASTM or other international norms, though often functional equivalents exist.
• Seamless Production: A core requirement is the seamless manufacturing method. Starting from solid steel billets ensures the final tube has no longitudinal weld seam, providing uniform structural integrity.
• Precision Characteristics: These tubes are frequently produced using cold finishing techniques (like cold drawing). This process imparts significantly tighter dimensional tolerances (OD, ID, wall) and a much smoother surface finish compared to hot-finished alternatives.
• St37 Steel Grade: This specifies a low-carbon steel (Carbon ≤ 0.17%) known for its excellent ductility, particularly when supplied in specific heat-treated conditions (annealed or normalized). This makes it suitable for forming operations and ensures good weldability.

Therefore, engineers specify DIN 2391 St37 Tubes when the application requires the reliability inherent in seamless construction coupled with the close tolerances and superior surface quality typical of precision tubing. It's a widely adopted grade for quality St37 Steel Pipes used in mechanical assemblies.

St37 Tubing Specifications

Conformance to the detailed parameters within DIN 2391 is vital for the correct application of St37 seamless precision tubes. USA Piping Solution supplies materials verified against these essential criteria.

Technical Specifications

Specification	Details
Primary Standard	DIN 2391 (Seamless Precision Steel Tubes). Related European standard EN 10305-1 often covers similar tubes and tolerances.
Grade Designation	St37 (related material number often 1.0037 or similar low-carbon designations under EN standards).
Manufacturing Process	Seamless production is mandatory under DIN 2391 Part 1 for designations like St37.
Finishing Method	Typically Cold Finished (Cold Drawn or Cold Rolled) to achieve the "precision" aspect. Delivery condition indicates the final state: BK: Cold Finished (Hard/As-drawn) - Strongest, least ductile. BKW: Cold Finished (Soft) - Lightly worked post-anneal. BKS: Cold Finished (Stress Relieved) - Stresses from cold work reduced. GBK: Annealed - Fully softened after cold finishing for maximum formability. NBK: Normalized - Heat treated for refined grain structure and balanced properties.
Size Availability (OD)	DIN 2391 generally covers outside diameters from approximately 4 mm up to potentially 190 mm, though commonly stocked sizes are typically within the range used for hydraulic and general mechanical parts.
Wall Thickness Range	Offered in various wall thicknesses, from thin walls (e.g., 0.5 mm) up to much heavier walls (e.g., 15 mm or more), varying with the OD.
Available Lengths	Can be procured in standard random lengths (often 4-6 meters) or supplied in precise cut-to-length pieces tailored to component production. Maximum mill lengths often reach 6000mm or longer.
Dimensional Tolerances (Refer to DIN 2391)	Precision is a hallmark. Tolerances on OD (e.g., ±0.08mm for small diameters) and wall thickness (often ±10% or better) are significantly tighter than standard pipe specifications. Straightness criteria also apply.

Chemical Composition and Mechanical Properties

The behavior of St37 Seamless Tubes during fabrication and in service—its strength, ability to be formed, weldability—originates from its defined low-carbon steel chemistry and the mechanical properties achieved through manufacturing and heat treatment.

Chemical Composition (% by Weight)

DIN 2391 Grade St37 specifies a straightforward low-carbon steel composition suitable for general mechanical purposes.

Element	St37 Requirement (%)	Role in Material Characteristics
Carbon (C)	≤ 0.17	Low level ensures good ductility and weldability.
Silicon (Si)	≤ 0.35	Deoxidizer used during steel production.
Manganese (Mn)	≥ 0.35 (Often higher)	Contributes to strength and toughness. (Range often 0.35-0.80 approx.)
Phosphorus (P)	≤ 0.040 (or 0.025)	Impurity, kept low for better material quality. (Limit varies by source)
Sulfur (S)	≤ 0.040 (or 0.025)	Impurity, limited for ductility and weldability. (Limit varies)

Note: Precise limits, especially for P & S, and Mn range might slightly vary based on the specific sub-grade or referencing standard (e.g., DIN 17100 St 37-2 vs. DIN 2391 St37). Always confirm against material certification.

Mechanical Properties (Condition Dependent)

The strength and ductility of DIN 2391 St37 Tubes are highly influenced by the final delivery condition, primarily the heat treatment applied after cold finishing. DIN 2391 provides minimum values for these common conditions:

Property	BK (Cold Finished /Hard)	GBK (Annealed)	NBK (Normalized)	Units	Interpretation
Tensile Strength	480 min	315 min	350 - 480 (Range)	MPa	Highest strength in the work-hardened BK state; softest in GBK state.
Yield Strength	(Implied High)	(Implied Low)	235 min	MPa	Only specified for NBK; significantly higher in BK, lower in GBK.
Elongation (A5)	6% min	25% min	25% min	%	Ductility is very limited in BK condition; much higher in GBK and NBK states.

Implications of Delivery Condition:

• BK (Hard): Select for maximum strength/hardness as-delivered, suitable if minimal forming is required or if machining is the primary operation.
• GBK (Annealed): Choose when extensive bending, flaring, or forming is necessary. Offers the highest ductility but lowest strength.
• NBK (Normalized): Provides a good combination of moderate strength, improved ductility over BK, and refined grain structure. A versatile condition for many mechanical parts.
• BKS (Stress Relieved): Used to reduce internal stresses from cold drawing with less impact on hardness than annealing or normalizing.
• BKW (Soft): Lightly cold worked after annealing, resulting in properties between GBK and BK.

Matching the delivery condition to the fabrication process and end-use requirements is essential when specifying St37 seamless precision tubes.

Manufacturing Process: Seamless Precision Tubing Explained

The creation of St37 Seamless Pipes to meet DIN 2391 precision standards involves specific steps designed to yield tubes with tight tolerances and superior surfaces:

1. Billet Selection & Heating: Starts with solid round billets of steel conforming to the St37 chemistry, heated uniformly to high temperatures for plasticity.
2. Piercing: A hole is created through the hot billet using specialized piercing mills (e.g., rotary piercer), forming a rough seamless hollow.
3. Hot Rolling (Optional/Initial Sizing): The pierced hollow might undergo some hot rolling passes to reduce the wall and elongate the tube, preparing it for subsequent cold work.
4. Surface Preparation: Before cold drawing, the surface of the hot-formed tube is typically cleaned (often by pickling) to remove scale, which is crucial for achieving a high-quality cold-drawn finish.
5. Cold Drawing: This defining step involves pulling the prepared tube through a precision die at room temperature. An internal mandrel is often used simultaneously to control the inside diameter. This process achieves several key outcomes: significant reduction in dimensions, elongation of the tube, creation of a smooth OD and ID surface, attainment of tight dimensional tolerances, and an increase in strength/hardness due to work hardening. Multiple passes may be needed.
6. Heat Treatment (Conditioning): Following the final cold draw, the tube undergoes a controlled heat treatment if required for the specified delivery condition. Annealing (GBK) fully softens it; Normalizing (NBK) refines the structure; Stress Relieving (BKS) reduces drawing stresses. Tubing ordered as BK bypasses this final heat treatment.
7. Finishing and Verification: The tubes are then straightened to meet precision tolerances, cut to the required final lengths, cleaned if necessary, potentially oiled for protection, and subjected to rigorous final inspections. This includes dimensional checks, surface examination, and any mechanical testing mandated by the specified condition.

This meticulous sequence ensures the final product meets the demanding dimensional and surface quality standards of DIN 2391 precision tubing.

Benefits of St37 Seamless Tubes

Choosing St37 Seamless Tubes produced according to DIN 2391 brings several key advantages to engineering designs and manufacturing processes:

• High Dimensional Precision: Cold finishing allows for very tight control over OD, ID, and wall thickness, often reducing or eliminating the need for subsequent machining to achieve final component dimensions.
• Superior Surface Quality: The cold drawing process yields smooth, clean surfaces on both the exterior and interior, which is beneficial for applications involving fluid flow, seals, bearings, or aesthetic considerations.
• Good Formability (GBK/NBK conditions): The inherent ductility of the low-carbon St37 grade, especially when annealed (GBK) or normalized (NBK), permits significant bending, flaring, and other forming operations without fracture.
• Consistent Mechanical Properties: Seamless manufacturing and controlled processing lead to predictable and uniform mechanical properties along the length and around the circumference of the tube (within the specified condition).
• Reliable Weldability: The low carbon content ensures St37 steel can be readily welded using standard techniques, simplifying assembly processes when needed.

Structural Integrity: Being seamless, these tubes lack a weld zone, offering inherent uniformity and eliminating potential issues related to weld integrity under stress or fatigue.

Applications and Industries Served

The combination of precision, good mechanical properties, and formability makes DIN 2391 St37 Tubes suitable for a wide range of applications across various industries:

• Hydraulic & Pneumatic Lines: Particularly in the NBK or GBK condition, St37 tubes are widely used for fluid power lines where reliable bending and flaring for connections are essential. Their dimensional accuracy aids in proper fitting assembly.
• Automotive Components: Utilized in manufacturing various parts such as fuel lines, brake lines (where standards permit), steering system components, seat frames, and other structural elements requiring precision.
• Mechanical Engineering: Serves as high-quality raw material for producing shafts, axles, bushings, spacers, rollers, machine frames, and numerous custom-machined precision components.
• Furniture Industry: Used in the construction of high-end metal furniture frames and decorative elements where a smooth finish and consistent shape are desired.
• General Construction: Employed in architectural features, support structures, and frameworks where dimensional precision and surface quality are important aesthetic or functional requirements.
• Instrumentation & Control Systems: Suitable for certain types of small-diameter lines used for instrumentation and control purposes.

St37 Seamless Pipes are selected when the application demands better tolerances, smoother surfaces, and more predictable formability than standard structural or pressure pipes offer.

St37 Tubing Size Chart and Weight Chart

This chart provides nominal dimensions and estimated weights for typical sizes of round St37 Seamless Tubes. Weights are theoretical calculations based on steel density.

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
12.0	1.5	9.0	0.40	0.27
16.0	1.5	13.0	0.55	0.37
18.0	2.0	14.0	0.81	0.54
20.0	2.0	16.0	0.90	0.61
22.0	2.5	17.0	1.25	0.84
25.0	2.0	21.0	1.15	0.77	Common Size
28.0	3.0	22.0	1.86	1.25
30.0	2.5	25.0	1.74	1.17
35.0	3.0	29.0	2.43	1.63
38.0	4.0	30.0	3.44	2.31
42.0	3.0	36.0	2.92	1.96
50.0	4.0	42.0	4.60	3.09	Common Size
55.0	5.0	45.0	6.27	4.21
60.0	4.0	52.0	5.61	3.77
70.0	5.0	60.0	8.13	5.47
80.0	6.0	68.0	11.1	7.47
90.0	7.0	76.0	14.6	9.81	Heavy Wall
100.0	8.0	84.0	18.3	12.3

Note: These are representative sizes. Weights are calculated from nominal dimensions and density (approx. 7.85 g/cm³). Actual weights will reflect manufacturing tolerances.

Certifications and Compliance

Confirming that St37 Seamless Tubes meet DIN 2391 and related quality standards is standard practice for ensuring material suitability. USA Piping Solution provides materials with appropriate validation.

• DIN 2391 Compliance: Tubing supplied is certified by the originating mill to meet the requirements of DIN 2391 for Grade St37. This includes verification of chemical composition, seamless manufacturing, precision dimensional tolerances, and the mechanical properties associated with the specified delivery condition (BK, GBK, NBK, etc.).
• Mill Certification: Shipments are typically accompanied by Mill Test Certificates (MTCs), often in accordance with EN 10204 (e.g., Type 3.1). These documents provide essential traceability through heat numbers and confirm the results of chemical analysis and relevant mechanical tests for the batch.
• ISO 9001 Procedures: Our quality management system operates under ISO 9001 certification, ensuring consistent processes for supplier verification, material inspection, and documentation control.
• Standard Markings: Tubes are marked according to DIN standards and common industry practice, generally including:
• Manufacturer's mark
• Standard reference (DIN 2391) and Grade (St37)
• Dimensions (OD x Wall)
• Delivery Condition code (e.g., NBK)
• Heat number or traceability identifier.

This documentation ensures material traceability and confirms conformity with the specified standard for engineering and manufacturing needs.

Why Choose USA Piping Solution for St37 Seamless Tubes?

Partnering with a supplier experienced in sourcing DIN standard materials can be advantageous. USA Piping Solution offers compelling reasons to source your St37 Seamless Tubes through us:

• Familiarity with DIN Standards: Our team understands the specifics of DIN 2391 and Grade St37, including the critical role of delivery conditions (BK/GBK/NBK) in determining final properties and suitability.
• Global Sourcing Network: We have established channels to reliably source high-quality seamless precision tubing manufactured to DIN standards from qualified international mills.
• Inventory Access & Logistics: While maintaining broad domestic stocks, we can efficiently access and deliver specific DIN standard requirements like St37 tubing throughout the United States.
• Commitment to Quality: We prioritize sourcing from reputable manufacturers and ensure comprehensive mill certification accompanies every order to verify compliance.
• Value-Added Processing: We provide precision saw cutting services to deliver tubes according to your exact length specifications, ready for use.
• Responsive Customer Support: Our sales and technical teams are dedicated to providing prompt, accurate responses to inquiries, detailed quotations, and efficient order processing.

Related Products

USA Piping Solution offers a variety of seamless tubes and pipes manufactured to different standards for diverse applications:

Selecting the correct standard and grade depends entirely on the specific requirements of your application regarding precision, strength, formability, temperature, and pressure. Our team can assist in navigating these choices.

Final Call to Action

For mechanical and engineering projects requiring the dimensional accuracy, smooth surface, and reliable performance of St37 Seamless Tubes manufactured to DIN 2391, choose USA Piping Solution. We provide certified DIN 2391 St37 Tubes and St37 Seamless Pipes, backed by our sourcing expertise and commitment to efficient delivery across the US. Ensure the quality of your components with materials from a dependable supplier.

Contact USA Piping Solution today to discuss your St37 Seamless Tubes needs and receive a detailed, competitive quotation.

Request Your St37 Tubing Quote Now!