Cold Rolled High Precision Seamless Steel Tube with High Dimensional Accuracy and Controlled Straightness for Automotive Use
Basic Properties
Place of Origin:
China
Brand Name:
Torich
Certification:
ISO 9001
Model Number:
GB/T 3639, DIN2391, EN10305
Trading Properties
Minimum Order Quantity:
1Tons
Price:
800-1000 USD/Ton
Payment Terms:
L/C,D/A,D/P,T/T,Western Union,
Supply Ability:
60000 Ton/Tons per Year
Product Summary
Cold Rolled Q345 E255 ST52 High Precision Seamless Steel Tube for Automotive Use Cold rolled high precision seamless steel tubes are designed for automotive components requiring controlled dimensions, smooth internal and external surfaces, consistent mechanical properties, and reliable forming or ...
Product Details
Highlight:
High Dimensional Accuracy Precision Steel Tube
,Controlled Straightness Seamless Steel Tube
,Smooth Tube Surface Cold Rolled Steel Tube
Product:
High Precision Seamless Steel Tube
Manufacturing Process:
Seamless Cold Drawn / Cold Rolled
Material:
Carbon Steel / High-strength Structural Steel
Main Grades:
Q345B, E255, E355, ST52, Grade 10, Grade 20
Applicable Standards:
GB/T 3639, EN 10305-1, DIN 2391
Outside Diameter:
Typically 4–76 Mm
Wall Thickness:
Typically 0.5–8.0 Mm
Length:
1–12 M Customized;
Product Description
Cold Rolled Q345 E255 ST52 High Precision Seamless Steel Tube for Automotive Use
Cold rolled high precision seamless steel tubes are designed for automotive components requiring controlled dimensions, smooth internal and external surfaces, consistent mechanical properties, and reliable forming or machining performance. The product can be manufactured under GB/T 3639, EN 10305-1, or legacy DIN 2391 requirements, with steel grades selected according to strength, forming requirements, and final component design.
Q345/Q345B, E255, and ST52 should not be treated as identical designations. E255 is an EN 10305-1 grade with a normalized minimum yield strength of 255 MPa, while the former DIN St52 grade is more closely associated with EN E355 in precision-tube applications. Q345B is commonly found in earlier GB/T 3639 specifications and purchasing documents. For new projects, the applicable standard edition and exact material designation should therefore be clearly stated on the purchase order and inspection certificate.
Specifications
| Item | Specification |
|---|---|
| Product | High Precision Seamless Steel Tube |
| Manufacturing Process | Seamless cold drawn / cold rolled |
| Material | Carbon steel / high-strength structural steel |
| Main Grades | Q345B, E255, E355, ST52, Grade 10, Grade 20 |
| Applicable Standards | GB/T 3639, EN 10305-1, DIN 2391 |
| Outside Diameter | Typically 4-76 mm; other dimensions available by agreement |
| Wall Thickness | Typically 0.5-8.0 mm; customized sizes available |
| Length | 1-12 m customized; GB/T 3639 standard ordinary length generally 3-12 m |
| Wall Thickness Tolerance | GB/T 3639: ±10% of nominal wall thickness or ±0.10 mm, whichever is greater |
| OD / ID Tolerance | According to specified standard, diameter and delivery condition |
| Straightness | GB/T 3639: maximum 1.5 mm/m |
| Cross Section | Round |
| Surface Condition | Bright, oiled, phosphated, galvanized or other agreed protective finish |
| Surface Roughness | EN 10305-1: typically Ra ≤4 μm for applicable tubes with D ≤260 mm |
| Tube Ends | Square cut and deburred |
| Heat Treatment | +C, +LC, +SR, +A or +N depending on standard and application |
| Inspection | Dimensional inspection, tensile test, chemical analysis and optional NDT |
| Documentation | Mill Test Certificate according to agreed inspection requirements |
Main Characteristics
High Dimensional Accuracy
Cold drawing or cold rolling controls tube geometry more precisely than conventional hot-finished tubing. This makes the product suitable for automotive components where the tube must subsequently be cut, bent, machined, expanded or assembled with closely controlled mating parts.
Under GB/T 3639-2021, wall thickness tolerance is generally ±10% of the nominal wall thickness or ±0.10 mm, whichever is greater. Out-of-roundness is controlled relative to the permitted diameter tolerance.
Controlled Straightness
For GB/T 3639 precision seamless tubes, curvature per meter is limited to 1.5 mm/m. Controlled straightness is particularly important for tubes entering automatic cutting equipment, CNC machining systems, bending machines and welded automotive subassemblies.
Defined Mechanical Delivery Conditions
Precision seamless tubing can be supplied in different conditions instead of specifying only a steel grade.
- +C: Cold worked / hard
- +LC: Cold worked / soft
- +SR: Cold worked and stress relieved
- +A: Annealed
- +N: Normalized
The delivery condition directly influences tensile strength, yield strength, elongation, dimensional stability and subsequent forming behavior.
Smooth Tube Surface
EN 10305-1 specifies controlled surface quality for precision tubing. For applicable tubes with an outside diameter not exceeding 260 mm, maximum roughness values of Ra 4 μm are specified for defined surfaces and delivery conditions.
This provides a more suitable starting surface for automotive machining, coating, plating and precision assembly than conventional structural tubing.
Our Advantages
Dimensional Requirements Are Defined Before Production
A common purchasing problem with precision tubing is specifying only nominal OD × wall thickness while leaving the delivery condition and tolerance class undefined.
Cold-working and subsequent heat treatment can change final dimensions. For this reason, production requirements can be confirmed using:
- Nominal OD
- Nominal ID where required
- Wall thickness
- Delivery condition
- Fixed-length tolerance
- Straightness requirement
- Surface roughness
- Out-of-roundness requirement
This reduces the risk of receiving technically compliant tubing that does not fit the customer's final machining or assembly process.
Grade Equivalence Is Reviewed Instead of Directly Substituted
ST52, E355, E255 and Q345 are frequently placed together in commercial equivalence tables, but their specified chemical and mechanical requirements are not identical.
For automotive projects, material substitution should therefore be based on:
- Applicable product standard
- Required yield strength
- Required tensile strength
- Elongation requirement
- Delivery condition
- Chemical composition
- Subsequent welding or forming process
For example, former DIN St52 is generally associated more closely with E355 than with E255. Material certificates can therefore be supplied according to the actual ordered grade rather than relying only on commercial equivalent-grade terminology.
Surface, Straightness and Heat Treatment Can Be Controlled Together
Automotive buyers frequently encounter tubes that meet basic chemistry requirements but create problems during machining because of scale, excessive curvature, dimensional movement after stress relieving, or inconsistent surface condition.
Precision tubes can be supplied with defined delivery conditions such as +SR or +N, controlled straightness, specified surface roughness and protective treatment. These parameters can be included in the purchase specification and verified during final inspection.
Execution Standards
| Standard System | Standard | Typical Grade | Description |
|---|---|---|---|
| EN | EN 10305-1 | E235, E255, E355 | Seamless cold drawn steel tubes for precision applications |
| DIN | DIN 2391 | St35, St45, St52 | Former German precision seamless steel tube specification; modern projects commonly use EN 10305-1 |
| GB | GB/T 3639 | Grade 10, Grade 20, Q345B legacy applications | Seamless cold-drawn or cold-rolled steel tubes for precision applications |
| ASTM | ASTM A519 | 1010, 1020 and other carbon/alloy grades | Seamless carbon and alloy steel mechanical tubing |
| JIS | JIS G 3445 | STKM grades | Carbon steel tubes for machine structural purposes |
| GOST | Applicable precision/mechanical tube standards | Steel 10, Steel 20 and related grades | Selection should be based on the required mechanical-tube specification and project documentation |
The specific standard and grade should be stated together. A material designation alone should not be used as a substitute for a complete technical specification.
Application
Automotive Shock Absorber Cylinder Tube
A specific application is the cylindrical steel tube used as the precision body component of an automotive hydraulic shock absorber.
The tube requires controlled ID and OD because the internal piston and sealing components operate within a restricted dimensional range. Straightness, inner-surface quality and wall uniformity also affect assembly accuracy and subsequent machining.
For this application, cold drawn or cold rolled seamless precision tubing in a suitable normalized or stress-relieved condition provides a controlled semi-finished product for cutting, machining, end forming and final shock absorber assembly.
Chemical Composition
| Grade | Standard / Reference | C % | Si % | Mn % | P % | S % |
|---|---|---|---|---|---|---|
| Grade 10 | GB/T 3639 / GB carbon steel requirements | 0.07-0.14 | 0.17-0.37 | 0.35-0.65 | ≤0.035 | ≤0.035 |
| Grade 20 | GB/T 3639 | 0.17-0.23 | 0.17-0.37 | 0.35-0.65 | ≤0.025 | ≤0.025 |
| Q345B | Earlier GB/T 3639 practice / GB/T 1591 reference | ≤0.20 | ≤0.50 | ≤1.70 | ≤0.030 for precision-tube application | ≤0.030 for precision-tube application |
| E255 / 1.0408 | EN 10305-1 | ≤0.21 | ≤0.35 | 0.40-1.10 | ≤0.025 | ≤0.025 |
| E355 / 1.0580 | EN 10305-1 | ≤0.22 | ≤0.55 | ≤1.60 | ≤0.025 | ≤0.025 |
Mechanical Properties
| Grade | Delivery Condition | Tensile Strength Rm | Yield Strength ReH | Elongation A |
|---|---|---|---|---|
| Grade 10 | +N | 320-450 MPa | ≥215 MPa | ≥27% |
| Grade 20 | +N | 440-570 MPa | ≥255 MPa | ≥21% |
| Q345B | +N / corresponding precision-tube condition | 490-630 MPa | ≥355 MPa | ≥22% |
| E255 / 1.0408 | +N | 440-570 MPa | ≥255 MPa | ≥21% |
| E355 / 1.0580 | +N | 490-630 MPa | ≥355 MPa | ≥22% |
E255 Mechanical Properties by Delivery Condition
| Delivery Condition | Tensile Strength Rm | Yield Strength ReH | Elongation |
|---|---|---|---|
| +C | ≥580 MPa | Not separately specified | ≥5% |
| +LC | ≥520 MPa | Not separately specified | ≥8% |
| +SR | ≥520 MPa | ≥375 MPa | ≥12% |
| +A | ≥390 MPa | Not separately specified | ≥21% |
| +N | 440-570 MPa | ≥255 MPa | ≥21% |
E355 Mechanical Properties by Delivery Condition
| Delivery Condition | Tensile Strength Rm | Yield Strength ReH | Elongation |
|---|---|---|---|
| +C | ≥640 MPa | Dependent on cold-work condition | ≥4% |
| +LC | ≥580 MPa | Dependent on cold-work condition | ≥7% |
| +SR | ≥580 MPa | ≥450 MPa | ≥10% |
| +A | ≥450 MPa | Not separately specified | ≥22% |
| +N | 490-630 MPa | ≥355 MPa | ≥22% |
Frequently Asked Questions
Q: Are you trading company or manufacturer?
A: Manufacturer, also can do trading.
Q: How long is your delivery time?
A: Generally speaking, it is 10-15 days if the goods are in stock, or it is 30-40 days if the goods are not in stock, it is according to quantity.
Q: Do you provide samples? Is it free or extra?
A: Yes, we could offer the sample for free charge but need pay the cost of freight.
Q: What is your terms of payment?
A: Payment ≤ 2000 USD, 100% in advance. Payment ≥ 2000 USD, 30% T/T in advance, balance before shipment. If you have another question, please feel free to contact with me.
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