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High Precision Seamless Automotive Steel Pipe with Controlled Inside Diameter

China High Precision Seamless Automotive Steel Pipe with Controlled Inside Diameter

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High Precision Seamless Automotive Steel Pipe with Controlled Inside Diameter

MOQ： 5 Tons
Price： 800-1000 USD/Tons
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Length	1–12 m, customizable
Manufacturing Method	Seamless cold drawing
Material	Carbon steel or low-alloy mechanical steel
Typical Grades	E235, E355, SAE 1020, SAE 1026, STKM11A, STKM12C, STKM13C, 20, 45
Wall Thickness	0.5–20 mm
Outside Diameter	6–200 mm
Product	High Precision Seamless Automotive Steel Pipe
Payment Terms	L/C,D/A,D/P,T/T,Western Union,MoneyGram
Supply Ability	2000Tons per Year
Delivery Time	30-45 work days
Packaging Details	Tubes are packed in wooden boxes or hexagonal bundles.
Main Standards	EN 10305-1, ASTM A519/A519M, JIS G 3445, GB/T 3639, DIN 2391
Brand Name	TORICH
Model Number	BS6323-6
Certification	ISO9001, ISO14001, TS16949
Place of Origin	ZHEJIANG, CHINA

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Product Specification


Length	1–12 m, customizable	Manufacturing Method	Seamless cold drawing
Material	Carbon steel or low-alloy mechanical steel	Typical Grades	E235, E355, SAE 1020, SAE 1026, STKM11A, STKM12C, STKM13C, 20, 45
Wall Thickness	0.5–20 mm	Outside Diameter	6–200 mm
Product	High Precision Seamless Automotive Steel Pipe	Payment Terms	L/C,D/A,D/P,T/T,Western Union,MoneyGram
Supply Ability	2000Tons per Year	Delivery Time	30-45 work days
Packaging Details	Tubes are packed in wooden boxes or hexagonal bundles.	Main Standards	EN 10305-1, ASTM A519/A519M, JIS G 3445, GB/T 3639, DIN 2391
Brand Name	TORICH	Model Number	BS6323-6
Certification	ISO9001, ISO14001, TS16949	Place of Origin	ZHEJIANG, CHINA
High Light	low carbon steel pipe ，steel mechanical tubing

High Precision Automotive Steel Pipe Seamless Steel Pipe For Car ISO9001

Product Overview

High precision automotive steel pipe is a cold-drawn seamless mechanical tube designed for components requiring accurate inside and outside diameters, controlled wall thickness, low surface roughness, and stable mechanical properties. It is primarily used for manufacturing automotive shock absorber cylinder barrels where dimensional consistency directly affects piston movement, sealing performance, oil retention, and service life.

The tubes can be supplied in cold-drawn, stress-relieved, annealed, or normalized conditions. Precision cutting, internal honing, external polishing, phosphating, and customized tolerance control are available according to the final machining and assembly requirements.

ISO 9001 refers to the manufacturer's quality management system rather than a steel tube material standard. Product conformity should therefore be specified separately according to EN 10305-1, ASTM A519, JIS G 3445, GB/T 3639, or another agreed technical standard.

Technical Specifications

Item	Specification
Product	High Precision Seamless Automotive Steel Pipe
Manufacturing Method	Seamless cold drawing
Material	Carbon steel or low-alloy mechanical steel
Main Standards	EN 10305-1, ASTM A519/A519M, JIS G 3445, GB/T 3639, DIN 2391
Typical Grades	E235, E355, SAE 1020, SAE 1026, STKM11A, STKM12C, STKM13C, 20, 45
Outside Diameter	6-200 mm
Wall Thickness	0.5-20 mm
Length	1-12 m, customizable
Standard OD Tolerance	According to the selected product standard
Precision OD Tolerance	Up to ±0.05 mm for suitable size ranges
Precision ID Tolerance	H8 or customized dimensional tolerance
Wall Thickness Tolerance	Normally ±10%; precision control up to ±5% by agreement
Straightness	≤0.5 mm/m; ≤0.3 mm/m available for selected dimensions
Internal Surface Roughness	As-drawn Ra ≤3.2 μm; honed Ra ≤0.4 μm
Surface Condition	Cold drawn, bright, phosphated, oiled, polished, honed, or customized
Heat Treatment	+C, +LC, +SR, +A, or +N
Inspection	Dimensional inspection, tensile test, hardness test, flattening test, flaring test, eddy-current test, or ultrasonic test
Quality Management	ISO 9001 quality management system
Documentation	EN 10204 3.1 inspection certificate available

Key Characteristics

Controlled Inside Diameter: Cold drawing through a die and over a mandrel provides closer control of the inside diameter than conventional hot-finished seamless tubing.
Low Internal Surface Roughness: Honed bore with Ra ≤0.4 μm reduces friction between the piston seal and cylinder wall, supporting stable hydraulic oil distribution.
Tight Wall Thickness Consistency: Precision cold drawing improves wall thickness uniformity and reduces eccentricity to ≤10% of nominal wall thickness.
High Straightness: Standard straightness controlled to ≤0.5 mm per metre, with selected dimensions available to ≤0.3 mm per metre.
Stable Mechanical Properties: Delivery condition can be selected according to subsequent manufacturing process requirements.
Clean Seamless Structure: Seamless production route eliminates longitudinal weld seam, providing uniform circumferential structure.

Production Process

Billet Inspection → Heating and Piercing → Hot Rolling or Elongation → Pickling → Lubrication → Cold Drawing → Intermediate Heat Treatment → Final Cold Drawing → Straightening → Cutting → Honing or Polishing → Non-Destructive Testing → Dimensional Inspection → Surface Protection → Packing

Quality Advantages

Bore Tolerance and Surface Roughness Control: We control the tube according to final component requirements rather than checking only nominal outside diameter.
Matched Delivery Conditions: Delivery condition can be selected according to the next manufacturing operation for optimal performance.
Component-Based Inspection: Inspection requirements can be converted directly from customer's component drawing into a tube control plan.

Execution Standards

Standard System	Applicable Standard	Brief Description
ASTM	ASTM A519/A519M	Seamless carbon and alloy steel mechanical tubing in hot-finished or cold-finished conditions
EN	EN 10305-1	Seamless cold-drawn steel tubes for precision applications
JIS	JIS G 3445	Carbon steel tubes for machine structures, including automotive components
GB	GB/T 3639	Cold-drawn or cold-rolled precision seamless steel tubes
DIN	DIN 2391	Traditional German specification for precision seamless steel tubes

Primary Application

Automotive Shock Absorber Cylinder Barrel: The tube is used as the hydraulic cylinder barrel of an automotive shock absorber. After precision cutting and internal honing, the bore guides the piston and sealing system while containing hydraulic oil under repeated compression and rebound cycles.

Chemical Composition

Grade	C	Si	Mn	P	S
STKM11A	≤0.12	≤0.35	≤0.60	≤0.040	≤0.040
STKM12A	≤0.20	≤0.35	≤0.60	≤0.040	≤0.040
STKM12C	≤0.20	≤0.35	≤0.60	≤0.040	≤0.040
STKM13A	≤0.25	≤0.35	0.30-0.90	≤0.040	≤0.040
STKM13C	≤0.25	≤0.35	0.30-0.90	≤0.040	≤0.040

Mechanical Properties

Grade	Tensile Strength Rm, MPa Min.	Yield Strength or Proof Stress, MPa Min.	Elongation, % Min.
STKM11A	290	Not specified	35
STKM12A	340	175	35
STKM12C	470	355	20
STKM13A	370	215	30
STKM13C	510	380	15

Surface and Heat-Treatment Options

Code	Delivery Condition	Processing Description	Recommended Use
+C	Cold Drawn / Hard	No heat treatment after final cold drawing	High strength and subsequent machining
+LC	Cold Drawn / Soft	Light final cold drawing after heat treatment	Moderate forming and machining
+SR	Stress Relieved	Heat treated below transformation temperature after cold drawing	Improved dimensional stability
+A	Annealed	Fully annealed after final cold drawing	Flaring, expansion, and extensive forming
+N	Normalized	Normalized in a controlled atmosphere	Uniform structure and improved formability

Frequently Asked Questions

Are you a trading company or manufacturer?

We are a manufacturer, but we can also handle trading operations.

How long is your delivery time?

Generally speaking, it is 10-15 days if the goods are in stock, or 30-40 days if the goods are not in stock, depending on quantity.

Do you provide samples? Is it free or extra?

Yes, we could offer the sample for free but need payment for the cost of freight.

What are your terms of payment?

Payment ≤2000USD: 100% in advance. Payment ≥2000USD: 30% T/T in advance, balance before shipment.

Company Details

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from Quality China Factory

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Business Type:

Manufacturer,Distributor/Wholesaler,Importer,Exporter,Trading Company,Seller 
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Year Established:

1997 
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Total Annual:

25000000-30000000
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Employee Number:

100~200 
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Ecer Certification：

Verified Supplier 

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TORICH INTERNATIONAL LIMITED
Suite 1604-3, Hongan Plaza, #258 Die Yuan Road, Yinzhou District, Ningbo City, China
https://www.precision-steeltube.com/

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