Q345A Steel Grade SSAW Pipe
Q345A Steel Grade SSAW Pipe: Comprehensive Material Data & Global Equivalents per GB/T 1591
In-depth analysis of Q345A structural steel for SSAW pipes, including chemical, mechanical, and thermal properties, international equivalents, and applications.
Hot rolling, cold forming, welding (including SSAW), machining, drilling
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Q345A Steel Grade SSAW Pipe Introduction
Q345A is a low-alloy high-strength structural steel specified in the Chinese standard GB/T 1591. It is widely utilized in welded structures, including Spiral Submerged Arc Welded (SSAW) pipes, which are used for transporting fluids and as structural elements.
- Key Features: Offers a minimum yield strength of 345 MPa, provides good weldability, excellent formability, and sufficient toughness for general engineering applications.
- Material characteristics: As a Grade A designation, it has standard impact testing requirements, making it a cost-effective choice for ambient temperature service conditions.
This data sheet provides a detailed overview of its official chemical composition, mechanical properties, and physical performance characteristics according to the official standard.
Q345A Steel Grade SSAW Pipe Chemical Composition per GB/T 1591
The chemical composition of Q345A is strictly controlled to ensure the specified mechanical properties and weldability. The maximum limits for carbon and manganese provide the desired strength, while phosphorus and sulfur are restricted to ensure purity and toughness. The standard allows for the addition of micro-alloying elements like niobium, vanadium, and titanium to achieve fine grain strengthening.
| Element | Standard Value (wt.%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.20 | Max |
| Silicon (Si) | ≤ 0.50 | Max |
| Manganese (Mn) | ≤ 1.70 | Max |
| Phosphorus (P) | ≤ 0.035 | Max |
| Sulfur (S) | ≤ 0.035 | Max |
| Niobium (Nb) | ≤ 0.07 | Optional grain refining element |
| Vanadium (V) | ≤ 0.15 | Optional grain refining element |
| Titanium (Ti) | ≤ 0.20 | Optional grain refining element |
| Chromium (Cr) | ≤ 0.30 | Residual element, max |
| Nickel (Ni) | ≤ 0.50 | Residual element, max |
| Copper (Cu) | ≤ 0.30 | Residual element, max |
| Nitrogen (N) | ≤ 0.012 | Max, if added as alloying element must be reported |
Q345A Steel Grade SSAW Pipe Thermal and Electrical Physical Properties
The physical properties of Q345A steel are fundamental for engineering calculations involving heat transfer, thermal expansion, and stiffness. These values are temperature-dependent and represent typical data for low-alloy carbon steels used in structural and piping applications.
| Property | Typical Value | Unit | Test Condition / Temperature |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20°C |
| Modulus of Elasticity (E) | 206 | GPa | At 20°C |
| Shear Modulus (G) | 79.4 | GPa | At 20°C |
| Poisson's Ratio (ν) | 0.30 | - | At 20°C |
| Thermal Expansion Coefficient (α) | 12.0 | 10⁻⁶ / K | 20°C - 100°C |
| Thermal Expansion Coefficient (α) | 12.9 | 10⁻⁶ / K | 20°C - 200°C |
| Thermal Expansion Coefficient (α) | 13.7 | 10⁻⁶ / K | 20°C - 300°C |
| Thermal Conductivity (λ) | 52.4 | W/(m·K) | At 100°C |
| Thermal Conductivity (λ) | 48.6 | W/(m·K) | At 200°C |
| Thermal Conductivity (λ) | 44.0 | W/(m·K) | At 400°C |
| Specific Heat Capacity | 460 - 480 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρ_e) | 0.22 - 0.25 | µΩ·m | At 20°C |
Q345A Steel Grade SSAW Pipe Mechanical Properties per GB/T 1591
The mechanical properties for Q345A are guaranteed for plates and strips used to fabricate SSAW pipes. Mandatory testing ensures the material meets minimum yield strength, tensile strength, elongation, and impact toughness requirements. The specified values are crucial for structural design and safe operational limits.
- Yield and Tensile Strength are dependent on the material thickness, decreasing slightly for thicker sections.
- Impact Test: The 'A' designation requires an impact energy of ≥34J at +20°C.
| Property | Standard Requirement Value | Unit | Test Condition / Thickness |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 345 | MPa | t ≤ 16 mm |
| Yield Strength (ReH) | ≥ 335 | MPa | 16 mm < t ≤ 40 mm |
| Yield Strength (ReH) | ≥ 325 | MPa | 40 mm < t ≤ 63 mm |
| Yield Strength (ReH) | ≥ 315 | MPa | 63 mm < t ≤ 80 mm |
| Yield Strength (ReH) | ≥ 305 | MPa | 80 mm < t ≤ 100 mm |
| Tensile Strength (Rm) | 470 - 630 | MPa | t ≤ 100 mm |
| Tensile Strength (Rm) | 470 - 630 | MPa | 100 mm < t ≤ 150 mm |
| Elongation after fracture (A) | ≥ 21 | % | t ≤ 16 mm |
| Elongation after fracture (A) | ≥ 20 | % | 16 mm < t ≤ 40 mm |
| Elongation after fracture (A) | ≥ 19 | % | 40 mm < t ≤ 63 mm |
| Elongation after fracture (A) | ≥ 19 | % | 63 mm < t ≤ 100 mm |
| Elongation after fracture (A) | ≥ 18 | % | 100 mm < t ≤ 150 mm |
| Impact Energy (KV2) | ≥ 34 | J | Longitudinal, +20°C |
| Bend Test (d=3a) | No cracking or rupture | - | t ≤ 16 mm, 180° bend |
Q345A Steel Grade SSAW Pipe Recommendations for Fully Equivalent Material Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591 | Q345A | Original specification; A-grade for +20°C impact testing. |
| International | ISO 630-2 | E355C | Equivalent in terms of yield strength and general structural use. |
| European Union | EN 10025-2 | S355JR (1.0045) | Direct equivalent for quality grade JR, with 27J at +20°C impact. |
| USA | ASTM A572/A572M | Grade 50 | Equivalent yield strength (345 MPa), similar chemistry. Type 1 is typical. |
| Japan | JIS G3106 | SM490A | Welded structural steel with equivalent strength and application scope. |
Q345A Steel Grade SSAW Pipe Application Introduction
Q345A is a versatile structural steel, and when formed into SSAW pipes, it becomes a primary material for large-diameter fluid transportation and structural piling. Its good combination of strength, ductility, and weldability allows it to be fabricated into complex engineering components.
- Welding notes: Preheating may be required for thick sections or when using low-hydrogen processes to avoid cold cracking.
- Formability: Excellent for cold forming operations, but flame cutting and edge preparation for welding are standard practices.
Product Applications: Long-distance oil and gas pipelines, Water mains and penstocks, Structural pipe piles and foundation casings, Building and stadium structural columns, Bridge decking and structural frameworks, Offshore platform legs and bracings
Processed into products: Spiral submerged arc welded (SSAW) pipe bodies, Welded junction boxes and fittings, Pipe flanges and reducers, Truss members and welded girders, Cut and formed mounting brackets, Drilled and bolted splice connections
Application industries: Oil & Gas Transportation, Construction and Civil Engineering, Water Supply and Drainage, Shipbuilding and Marine Engineering, Infrastructure (Bridges, Highways)
Q345A Steel Grade SSAW Pipe Recommendations for Similar/Near-Equivalent Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591 | Q345B | Higher quality grade than Q345A, requiring 34J impact energy at +20°C. More commonly available. |
| European Union | EN 10025-2 | S355J0 (1.0553) | Similar strength but with guaranteed impact properties at 0°C, offering enhanced toughness. |
| USA | ASTM A572/A572M | Grade 55 | Slightly higher strength grade (55 ksi yield), suitable for weight reduction in designs. |
| Russia | GOST 19281 | 17G1S | Similar manganese-silicon steel used for welded structures, pipes, and vessels. |
Notes:
Weldability: Q345A has a carbon equivalent value (CEV) generally below 0.45%, ensuring good weldability without special preheating for thinner sections. For SSAW pipe production, the longitudinal and spiral welds are subject to Non-Destructive Testing (NDT), such as ultrasonic or X-ray inspection, as per the purchasing order requirements like GB/T 3091 or API Spec 5L. Corrosion resistance: This is a standard carbon-manganese steel and requires surface coating or cathodic protection for in-ground or submerged service.
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