Q345B+304L Clad Steel Plate
Q345B+304L Clad Steel Plate: High-Strength, Corrosion-Resistant Composite Material (GB/T 8165)
Explore the dual-material advantages of Q345B+304L clad steel plate, combining the mechanical strength of Q345B structural steel with the corrosion resistance of 304L stainless steel, manufactured per GB/T 8165 standard.
Hot rolling, explosive welding, roll bonding, cutting, welding (necessary precautions for dissimilar metal joints), forming, machining
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Q345B+304L Clad Steel Plate Introduction
Q345B+304L clad steel plate is a bimetallic composite material produced by bonding a layer of 304L austenitic stainless steel (cladding) to a Q345B low-alloy structural steel (base) through hot rolling, explosive welding, or roll bonding. The cladding provides excellent resistance to corrosion in oxidizing and mildly reducing environments, while the base delivers high yield strength and good weldability for structural integrity. This combination achieves cost savings by reducing the use of expensive stainless steel without compromising performance. Key properties include: minimum yield strength of 345 MPa (base), tensile strength 470–630 MPa, elongation ≥21%, and shear strength of the interface ≥210 MPa. The material is widely used in pressure vessels, heat exchangers, storage tanks, and chemical processing equipment where both mechanical loading and aggressive media are present. Typical total thickness ranges from 6 mm up to over 100 mm, with the cladding thickness usually 2–4 mm.
Q345B+304L Clad Steel Plate Chemical Composition
The table lists the chemical requirements for both the cladding (304L stainless steel per GB/T 4237 or GB/T 3280) and the base (Q345B low-alloy steel per GB/T 1591). For the clad plate, the cladding layer must meet its own standard; the base metal must meet its standard. Overall composition is not defined; simultaneous conformity of individual layers is guaranteed by design.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| C (cladding) | ≤0.03 | 304L per GB/T 4237 |
| Si (cladding) | ≤1.00 | 304L |
| Mn (cladding) | ≤2.00 | 304L |
| P (cladding) | ≤0.045 | 304L |
| S (cladding) | ≤0.030 | 304L |
| Cr (cladding) | 18.00 – 20.00 | 304L |
| Ni (cladding) | 8.00 – 12.00 | 304L |
| N (cladding) | ≤0.10 | 304L |
| C (base) | ≤0.20 | Q345B per GB/T 1591 |
| Si (base) | ≤0.50 | Q345B |
| Mn (base) | ≤1.70 | Q345B |
| P (base) | ≤0.035 | Q345B |
| S (base) | ≤0.035 | Q345B |
| Nb+V+Ti (base) | ≤0.15 | Q345B; microalloying elements as per standard |
| Al (base) | ≥0.015 (if contained) | Q345B; fine grain practice |
Q345B+304L Clad Steel Plate Thermal, Electrical and Physical Properties
Physical properties of the clad plate depend on the thickness ratio of cladding to base. The table provides typical properties of the individual materials 304L (cladding) and Q345B (base) at room temperature unless otherwise noted. Composite values can be estimated using the rule of mixtures. No single standard covers all physical properties for the composite.
| Property | Typical Value | Unit | Test Condition / Layer |
|---|---|---|---|
| Density (ρ) | 7.93 | g/cm³ | 304L cladding |
| Density (ρ) | 7.85 | g/cm³ | Q345B base |
| Elastic modulus (E) | 193 | GPa | 304L at 20°C |
| Elastic modulus (E) | 206 | GPa | Q345B at 20°C |
| Shear modulus (G) | 74 | GPa | 304L (calculated from E and ν) |
| Shear modulus (G) | 79 | GPa | Q345B (calculated from E and ν) |
| Poisson's ratio (ν) | 0.30 | – | 304L |
| Poisson's ratio (ν) | 0.30 | – | Q345B |
| Thermal expansion (α, 20–100°C) | 16.0 | 10⁻⁶/K | 304L |
| Thermal expansion (α, 20–100°C) | 12.0 | 10⁻⁶/K | Q345B |
| Thermal conductivity (λ, 100°C) | 16.3 | W/(m·K) | 304L |
| Thermal conductivity (λ, 100°C) | 45 | W/(m·K) | Q345B |
| Specific heat capacity (c, 20°C) | 500 | J/(kg·K) | 304L |
| Specific heat capacity (c, 20°C) | 480 | J/(kg·K) | Q345B |
| Electrical resistivity (ρ_e) | 0.73 | μΩ·m | 304L at 20°C |
| Electrical resistivity (ρ_e) | 0.17 | μΩ·m | Q345B at 20°C |
Q345B+304L Clad Steel Plate Mechanical Properties
Mechanical properties are in accordance with GB/T 8165-2008. The tensile test requires that the full-thickness specimen meets the minimum requirements of the base metal Q345B. The cladding interface must exhibit a shear strength not less than 210 MPa. Bend testing is performed with the cladding in tension or compression, depending on the application.
| Property | Required Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield strength (ReH) | ≥345 | MPa | Base Q345B, thickness ≤16 mm; for larger thickness, reduction may apply per GB/T 1591 |
| Tensile strength (Rm) | 470 – 630 | MPa | Full thickness specimen |
| Elongation after fracture (A) | ≥21 | % | Gauge length 5.65√S₀, full thickness |
| Shear strength of bond interface | ≥210 | MPa | Clad plate interface; test according to GB/T 6396 or equivalent |
| Bend test (cladding in tension) | 180° bending, no crack at interface | ° | Bend diameter 2a for Grade I, 3a for Grade II (a = plate thickness); for pressure vessel applications usually Grade I |
| Bend test (cladding in compression) | 180° bending, no crack | ° | Bend diameter same as above |
| Impact energy (KV₂) – base only | ≥34 (longitudinal) | J | At 20°C (Q345B); optional testing for base |
Q345B+304L Clad Steel Plate Equivalent Clad Plate Standards and Directly Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 8165 | Q345B+304L (or Q345B+S30403) | Base Q345B; cladding 304L (UNS S30403) |
| USA | ASTM A264 | 304L + Grade A | Base carbon steel Grade A (min YS 240 MPa); 304L cladding. Strength level lower than Q345B |
| USA | ASME SA-264 | SA-240 304L + SA-516 Gr.70 | Base SA-516 Gr.70 (min YS 260 MPa); similar corrosion resistance, base strength slightly lower |
| Japan | JIS G3601 | SUS304L + SPV235 | SPV235 boiler steel has YS ≥235 MPa; 304L cladding. Many desalination plants use JIS grades |
| Europe | EN 10351 | 1.4307 + S355J2+N | Base S355J2 (min YS 355 MPa) matches Q345B; cladding 1.4307 (304L analog) |
Q345B+304L Clad Steel Plate Application Introduction
Q345B+304L clad plate is engineered for applications where a structural steel component faces corrosive media. The 304L layer resists intergranular corrosion due to its low carbon content, and the Q345B base carries mechanical loads. It eliminates the need for solid stainless steel, reducing material cost by 30–50%. Typical fabrication includes cold or hot forming, welding with appropriate filler metals (E309L or ER309L for transition joints), and post-weld heat treatment when required. The product can be supplied as plates up to 4000 mm width and 12000 mm length, with total thickness from 6 mm. Cladding thickness usually 2–4 mm, but can be specified as 10–15% of total thickness.
Product Applications: Pressure vessels (reactors, columns, separators), Shell-and-tube heat exchangers, Storage tanks for corrosive liquids (sulfuric acid, caustic soda), Digesters and bleaching towers for pulp and paper, Flue gas desulfurization (FGD) absorbers, Process piping and clad fittings, Chemical tankers (shipbuilding)
Processed into products: Vessel shells and heads (explosion-bonded dished heads), Tube sheets for heat exchangers, Clad flanges and nozzles, Transition joints between clad and solid stainless steel, Clad wear plates and baffles, Expansion bellows (where thermal cycling occurs), Bridges and building panels with aesthetic stainless steel exterior
Application industries: Petrochemical and chemical processing, Oil and gas (onshore and offshore), Power generation (flue gas desulfurization, nuclear heat exchangers), Desalination and water treatment, Food and beverage processing, Pharmaceutical equipment, Civil and marine engineering (piers, bridges in corrosive atmosphere)
Q345B+304L Clad Steel Plate Similar or Substitute Clad Materials
| Country/Region | Standard | Suggested Grade | Remarks |
|---|---|---|---|
| China | GB/T 8165 | Q245R+304L | Lower base strength (YS ≥245 MPa) but excellent for pressure vessels at moderate pressure. Corrosion resistance identical. |
| China | GB/T 8165 | Q345B+316L | Enhanced pitting resistance from Mo-bearing 316L cladding; used where chlorides are present. Mechanical base same. |
| USA | ASTM A264 | 316L + Grade B | Similar strength to Q345B (Grade B YS ≥275 MPa) plus better corrosion resistance than 304L |
| Europe | EN 10351 | 1.4404 + P355GH | P355GH (YS ≥295 MPa) slightly lower than Q345B; cladding 1.4404 (316L) for aggressive environments |
Notes:
All data are based on GB/T 8165-2008 and applicable base/cladding standards (GB/T 1591, GB/T 4237). Actual product may be ordered with supplementary requirements such as ultrasonic testing (UT) for bond integrity per NB/T 47013.3, ferrite content measurement for cladding, intergranular corrosion test (GB/T 4334 method E), and impact test at lower temperatures for the base. The combination of Q345B + 304L can be supplied in as-rolled, normalised, or stress-relieved condition. Welding procedures must be qualified according to NB/T 47014 or equivalent, and weld overlay shall be on the Q345B side when necessary. For explosive welding, shear strength requirement remains the same. The cladding surface finish can be pickled and passivated upon request.
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