Q235B + 304 Clad Steel Plate
Q235B + 304 Clad Steel Plate: High-Strength Carbon Steel Core with Superior Corrosion Resistance
Explore the properties of Q235B + 304 clad steel plate: a composite material combining a Q235B carbon steel base for strength and a 304 stainless steel cladding for excellent corrosion resistance, manufactured per GB/T 8165-2008.
Hot rolling bonding, explosive bonding, explosive-rolling bonding; subsequent cutting, forming, welding
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Q235B + 304 Clad Steel Plate Introduction
The Q235B + 304 clad steel plate is a bimetallic composite material produced by hot-rolling, explosive bonding, or explosive-rolling processes, consisting of a base layer of Q235B carbon structural steel (per GB/T 700) and a cladding layer of 304 (06Cr19Ni10) austenitic stainless steel (per GB/T 20878). This combination leverages the high strength and low cost of the carbon steel substrate with the superior corrosion and oxidation resistance of the stainless steel surface. The metallurgical bonding ensures excellent interfacial shear strength (≥210 MPa) and full integrity under thermal and mechanical loads. Key features include:
- Cost-effective alternative to solid stainless steel for large structural components
- Good weldability and formability of the base layer
- Excellent resistance to intergranular corrosion and pitting in mild to moderately aggressive environments
- Wide availability in plates and sheets for pressure vessels, chemical tanks, and structural applications
Q235B + 304 Clad Steel Plate Chemical Composition
The clad steel plate has two distinct chemical compositions. The base metal Q235B is a plain carbon structural steel with controlled carbon and manganese for weldability. The cladding metal 304 is an austenitic stainless steel with chromium and nickel contents that ensure passive film formation and corrosion resistance. Values below are per respective base standards (GB/T 700 for Q235B, GB/T 20878 for 304), as referenced in GB/T 8165-2008. Impurity limits for sulfur and phosphorus are essential for bonding quality.
| Chemical Element | Standard Value | Remarks |
|---|---|---|
| C (Base) | ≤ 0.20 | Q235B base layer, ladle analysis per GB/T 700 |
| C (Clad) | ≤ 0.08 | 304 clad layer, ladle analysis per GB/T 20878 |
| Si (Base) | ≤ 0.35 | Q235B |
| Si (Clad) | ≤ 1.00 | 304 |
| Mn (Base) | ≤ 1.40 | Q235B |
| Mn (Clad) | ≤ 2.00 | 304 |
| P (Base) | ≤ 0.045 | Q235B |
| P (Clad) | ≤ 0.045 | 304 |
| S (Base) | ≤ 0.045 | Q235B |
| S (Clad) | ≤ 0.030 | 304 |
| Cr (Clad) | 18.00 – 20.00 | 304 clad layer |
| Ni (Clad) | 8.00 – 11.00 | 304 clad layer |
| N (Clad) | ≤ 0.10 | 304, optional |
Q235B + 304 Clad Steel Plate Thermal and Electrical Physical Properties
The physical properties of the clad plate are not standardized for the composite; they depend on the thickness ratio of the layers. The table below provides typical values at room temperature for each individual material. For combined properties, a weighted average by volume fraction is often used. Data are taken from reliable engineering references consistent with GB/T 8165-2008 and associated base standards. Electrical resistivity is given for completeness in corrosion/welding applications.
| Property | Typical Value | Unit | Material / Condition |
|---|---|---|---|
| Density (ρ) – Base Q235B | 7.85 | g/cm³ | Q235B, room temperature |
| Density (ρ) – Clad 304 | 7.93 | g/cm³ | 304, room temperature |
| Elastic Modulus (E) – Base | 200 – 210 | GPa | Q235B, RT |
| Elastic Modulus (E) – Clad | 193 – 200 | GPa | 304, RT |
| Shear Modulus (G) – Base | ~ 79.3 | GPa | Q235B, estimated from E and ν=0.3 |
| Shear Modulus (G) – Clad | ~ 77.2 | GPa | 304, ν=0.27–0.3 |
| Poisson's Ratio (ν) – Base | 0.25 – 0.30 | – | Typical for carbon steel |
| Poisson's Ratio (ν) – Clad | 0.27 – 0.30 | – | 304 stainless steel |
| Thermal Expansion (α, 20–100°C) – Base | ~ 12.0 | 10⁻⁶/K | Q235B, linear expansion |
| Thermal Expansion (α, 20–100°C) – Clad | ~ 16.0 – 17.3 | 10⁻⁶/K | 304 stainless steel |
| Thermal Conductivity (λ) – Base | ~ 50 – 60 | W/(m·K) | Q235B, at 100°C |
| Thermal Conductivity (λ) – Clad | ~ 15 – 16 | W/(m·K) | 304, at 100°C |
| Specific Heat Capacity (cp) – Base | ~ 480 | J/(kg·K) | Q235B, RT to 100°C |
| Specific Heat Capacity (cp) – Clad | ~ 500 | J/(kg·K) | 304, RT to 100°C |
| Electrical Resistivity (ρe) – Base | ~ 0.15 – 0.22 | µΩ·m | Q235B, RT |
| Electrical Resistivity (ρe) – Clad | ~ 0.72 – 0.73 | µΩ·m | 304, RT |
Q235B + 304 Clad Steel Plate Mechanical Properties
The mechanical properties of the clad plate are determined by the base and clad layers individually and by the bond integrity. Tension tests are performed on total thickness specimens. The values below are for the as-delivered condition (hot-rolled, heat-treated) according to GB/T 8165-2008. For combined tensile properties, the rule of mixture can be applied using individual layer properties. Interfacial shear strength is a critical quality parameter. Bending tests verify formability and bond soundness.
| Property | Standard Requirement / Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (ReH) – Base Q235B | ≥ 235 (thickness ≤ 16 mm); ≥ 225 (16 < t ≤ 40 mm) | MPa | Per GB/T 700, room temperature |
| Tensile Strength (Rm) – Base Q235B | 370 – 500 | MPa | Per GB/T 700 |
| Elongation (A) – Base Q235B | ≥ 26 (thickness ≤ 40 mm) | % | Gauge length 5.65√S₀ |
| Yield Strength (Rp0.2) – Clad 304 | ≥ 205 | MPa | Per GB/T 20878, annealed condition |
| Tensile Strength (Rm) – Clad 304 | ≥ 520 | MPa | Per GB/T 20878 |
| Elongation (A) – Clad 304 | ≥ 40 | % | Gauge length 50 mm |
| Interfacial Shear Strength (τb) | ≥ 210 | MPa | GB/T 8165-2008, shear test of bond interface |
| Bend Test (D = 2a, 180°) | No cracking or separation | – | Clad side in tension or compression, a = specimen thickness |
| Impact Energy (KV₂) – Base | ≥ 27 (longitudinal, at 20°C) | J | Q235B, Charpy V-notch, per GB/T 700 |
| Hardness – Clad 304 | ≤ 200 HBW | – | Typical for annealed 304; not mandatory for clad certification |
Q235B + 304 Clad Steel Plate Fully Equivalent Materials – Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 8165-2008 | S30408+Q235B | Identical to the specified clad plate; clad 304 (06Cr19Ni10) on Q235B base |
| Japan | JIS G3601:2012 | SUS304+SS400 | Stainless clad steel; SS400 base similar to Q235B, SUS304 clad |
| USA | ASTM A264-12 (withdrawn, but reference) | Type 304 + A36 | Similar composite; A36 base plate mechanicals close to Q235B |
| Europe | EN 10028-7:2016 | X5CrNi18-10 + P265GH | Clad plate for pressure purposes; stainless steel clad on carbon steel |
Q235B + 304 Clad Steel Plate Application Introduction
Q235B + 304 clad steel plate is engineered for environments demanding both structural integrity and surface corrosion protection. Typical application areas include:
- Chemical and petrochemical processing equipment, where the 304 clad resists a wide range of organic and inorganic chemicals at moderate temperatures, while the Q235B base provides pressure containment strength.
- Pressure vessels and storage tanks operating under ASME/PED design codes, reducing material costs compared to solid stainless steel.
- Flue gas desulfurization (FGD) systems in power plants, where sulfurous acid condensation is resisted by the clad.
- Architectural and structural components in corrosive atmospheres, such as coastal bridges and building facades.
- Food processing and dairy equipment requiring hygienic surfaces and structural rigidity.
Product Applications: Reaction vessels and autoclaves, Heat exchangers and condensers, Storage tanks for acids and alkalis, Desulfurization towers and ducts, Clad pipes and fittings, Pressure vessel shells and heads, Modular building panels
Processed into products: Cylindrical vessel shells (rolled and welded), Dished and elliptical heads (pressed or spun), Tube sheets for heat exchangers, Flanges and nozzles (explosion-bonded sections), Ductwork sections for corrosive gases, Structural stiffeners with clad surface, Lining plates for concrete basins
Application industries: Chemical and Petrochemical, Oil & Gas, Power Generation, Water Treatment, Food and Beverage, Architectural and Construction, Shipbuilding
Q235B + 304 Clad Steel Plate Similar/Alternative Clad Materials Recommendation
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 8165-2008 | S31603+Q235B | Clad layer 316L for pitting resistance in chloride environments; base same |
| China | GB/T 8165-2008 | S30408+Q345R | Higher strength base (Q345R) for pressure vessels; similar corrosion resistance |
| Japan | JIS G3601 | SUS316L+SS400 | Improved corrosion resistance over 304 clad; comparable base |
| Europe | EN 10028-7 | X2CrNiMo17-12-2 + P355GH | 316L type clad on higher-strength carbon steel; for high-temperature pressure equipment |
| International | ASTM A264 | Type 316L + A516 Gr70 | Alternative with robust low-temperature toughness base and Mo-alloyed clad |
Notes:
When ordering Q235B + 304 clad plate per GB/T 8165-2008, the designation includes total thickness, clad thickness, and condition. For example: S30408+Q235B, 10+3, No.1 finish. Ultrasonic testing (UT) to assess bond integrity is mandatory per the standard, with minimum 95% continuous bond. Welding requires dissimilar metal transition joints and appropriate filler metals (e.g., E309L for clad restoration, E5015 for structural seams). Post-weld heat treatment (PWHT) must consider sensitization of the clad 304; stress relief of the carbon steel base may be performed with caution. Maximum service temperature for the clad layer is typically limited to about 800°F (425°C) to avoid carbide precipitation and sigma phase embrittlement. For cyclic thermal applications, the thermal expansion difference between the layers must be considered in design.
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