GB/T 3094 35# Cold
GB/T 3094 35# SHS/RSH Pipe: Cold Drawn Special-Shaped Carbon Steel Tube for Structural Applications
In-depth technical data of GB/T 3094 35# square and rectangular hollow section pipe, including chemical composition, mechanical and physical properties, international equivalents, and application guidance.
Cold drawing, stress relieving, annealing, normalizing, cutting, machining, welding, bending, and surface treatment
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GB/T 3094 35# Cold Introduction
The GB/T 3094 35# SHS/RSH pipe is a cold-drawn special-shaped steel hollow section manufactured from 35-grade quality carbon structural steel according to Chinese standard GB/T 3094. It is supplied in square (SHS) and rectangular (RSH) cross-sections, offering a combination of moderate strength, good machinability, and weldability. Key features include:
- Consistent cross-sectional dimensions and smooth surface finish through cold drawing
- Multiple delivery conditions (cold drawn, stress relieved, annealed, or normalized) to meet varied service requirements
- Wide application in mechanical parts, structural frameworks, and automotive components
This material is extensively used where precision tolerances and reliable mechanical properties are essential.
GB/T 3094 35# Cold Chemical Composition
The chemical composition of 35# steel is specified in GB/T 699 (Quality Carbon Structural Steels). It is a medium-carbon steel with controlled impurities. The following limits apply for heat analysis; product analysis tolerances are per the relevant standard.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | 0.32 – 0.39 | Key for strength and hardenability |
| Silicon (Si) | 0.17 – 0.37 | Deoxidation element |
| Manganese (Mn) | 0.50 – 0.80 | Strength and toughness |
| Phosphorus (P) | ≤ 0.035 | Impurity, maximum |
| Sulfur (S) | ≤ 0.035 | Impurity, maximum |
| Chromium (Cr) | ≤ 0.25 | Residual element |
| Nickel (Ni) | ≤ 0.30 | Residual element |
| Copper (Cu) | ≤ 0.25 | Residual element |
GB/T 3094 35# Cold Thermal and Electrical Physical Properties
The following physical properties are typical for 35# carbon steel in the range 20–100°C, applicable for engineering design. Values are drawn from general resources for medium‑carbon steels and are not specific to the tube condition unless indicated. Actual values may vary slightly with heat treatment and microstructure.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At room temperature |
| Elastic modulus (E) | 200 – 210 | GPa | At room temperature |
| Shear modulus (G) | 79 – 81 | GPa | Calculated from E and ν |
| Poisson's ratio (ν) | 0.29 – 0.30 | Dimensionless | Elastic range |
| Thermal expansion coefficient (α) | 11.3 – 12.0 | 10⁻⁶/K | 20–100°C |
| Thermal expansion coefficient (α) | 12.5 – 13.1 | 10⁻⁶/K | 20–200°C |
| Thermal expansion coefficient (α) | 13.5 – 14.0 | 10⁻⁶/K | 20–300°C |
| Thermal conductivity (λ) | 49 – 52 | W/(m·K) | At 20°C |
| Thermal conductivity (λ) | 46 – 49 | W/(m·K) | At 100°C |
| Thermal conductivity (λ) | 42 – 45 | W/(m·K) | At 200°C |
| Specific heat capacity | 460 – 480 | J/(kg·K) | 20–100°C |
| Electrical resistivity (ρ_e) | 0.15 – 0.19 | μΩ·m | At 20°C |
GB/T 3094 35# Cold Mechanical Properties
Mechanical properties of 35# steel tubes are defined in GB/T 3094 and depend on delivery condition. The table lists minimum requirements for common delivery states. Testing is conducted at room temperature on longitudinal strip samples.
- BK (cold drawn/hard): high strength, reduced ductility
- BKS (stress relieved): moderate strength and ductility
- GBK (annealed): lowest strength, best formability
- NBK (normalized): balanced properties
| Property Item | Standard Requirement (min) | Unit | Test Condition |
|---|---|---|---|
| Tensile strength (Rm) | 590 | MPa | Delivery condition: BK (cold drawn/hard) |
| Tensile strength (Rm) | 540 | MPa | Delivery condition: BKS (cold drawn & stress relieved) |
| Tensile strength (Rm) | 490 | MPa | Delivery condition: GBK (annealed) |
| Tensile strength (Rm) | 510 | MPa | Delivery condition: NBK (normalized) |
| Yield strength (ReH) | 470 | MPa | Delivery condition: BK |
| Yield strength (ReH) | 390 | MPa | Delivery condition: BKS |
| Yield strength (ReH) | 265 | MPa | Delivery condition: GBK |
| Yield strength (ReH) | 305 | MPa | Delivery condition: NBK |
| Elongation after fracture (A) | 6 | % | Delivery condition: BK; gauge length L0=5.65√S0 |
| Elongation after fracture (A) | 8 | % | Delivery condition: BKS; gauge length L0=5.65√S0 |
| Elongation after fracture (A) | 20 | % | Delivery condition: GBK; gauge length L0=5.65√S0 |
| Elongation after fracture (A) | 17 | % | Delivery condition: NBK; gauge length L0=5.65√S0 |
GB/T 3094 35# Cold Fully Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10305-1 | C35E | Cold drawn seamless precision steel tube; technical delivery conditions; very close match in composition and intended use. |
| USA | ASTM A519 | 1035 | Seamless carbon and alloy steel mechanical tubing; equivalent carbon-manganese steel for mechanical applications. |
| Japan | JIS G3445 | STKM14A | Carbon steel tubes for machine structural purposes; Mn and C content band similar to 35#, suitable substitute. |
| Germany | DIN 2391-2 (superseded, see EN) | C35E (DIN 17204) | Seamless precision steel tube; old designation Ck35/C35E provides comparable properties. |
GB/T 3094 35# Cold Application Introduction
35# SHS/RSH pipe is a versatile engineering material that can be tailored through heat treatment and delivery condition. The cold drawn surface and dimensional precision make it suitable for components requiring minimal machining allowance. Typical application areas include:
Product Applications: Mechanical structural tubes and hollow sections, Hydraulic cylinder barrels and piston rods, Transmission shafts and axles, Rolls and sleeves for conveyors, Chassis components and roll cages (where regulations permit), Precision machinery frameworks
Processed into products: Bushes and bearing sleeves, Cylinder liners and housings, Rolls, rollers, and sliding guides, Adapter and connector sleeves, Machine tool spindles (light to medium load), Telescopic and adjusting rods, Tension and compression members in trusses
Application industries: Machinery and equipment manufacturing, Automotive and transportation, Construction and structural engineering, Agricultural machinery, Hydraulic and pneumatic systems, Furniture and industrial equipment
GB/T 3094 35# Cold Similar/Comparable Substitute Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 3094 | 20# | Lower carbon content; better weldability and ductility but lower strength. Suitable where moderate strength is acceptable. |
| China | GB/T 3094 | 45# | Higher carbon strength grade; improved wear resistance after heat treatment, but reduced weldability. |
| Europe | EN 10210-1 | S355J2H | Hot finished structural hollow section; higher toughness and weldability, but carbon content different; strength level comparable in some conditions. |
| International | ISO 683-2 | C35E4 (alias 1.1181) | Heat-treatable steel; comparable chemistry and mechanical properties when formed into tube. |
Notes:
- Delivery condition strongly influences mechanical properties: BK offers maximum strength for static applications; GBK or NBK is preferred when subsequent forming or welding is required.
- For welded structures, preheating and post-weld heat treatment may be advisable due to medium carbon content.
- The material can be further hardened by quenching and tempering if local high strength is needed; however, distortion in thin-walled SHS/RSH should be considered.
- Surface finish and straightness comply with GB/T 3094 – supplementary requirements may be agreed upon at the time of order.
- All data provided is based on official published standards and commonly accepted reference values. For specific projects, mill certificates should be consulted.
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