{"id":5772,"date":"2026-10-08T15:09:33","date_gmt":"2026-10-08T07:09:33","guid":{"rendered":"https:\/\/jblstainless.com\/?post_type=product&p=5772"},"modified":"2026-10-08T15:16:18","modified_gmt":"2026-10-08T07:16:18","slug":"high-strength-low-alloy-steel-plate-q345-q345a-q345b","status":"publish","type":"product","link":"https:\/\/jblstainless.com\/ar\/high-strength-low-alloy-steel-plate-q345-q345a-q345b\/","title":{"rendered":"High Strength Low Alloy Steel Plate Q345 Q345A Q345B"},"content":{"rendered":"
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High Strength Low Alloy Steel Plate Q345 Q345A Q345B<\/span>—-Q345 can be classified into grades Q345A, Q345B, Q345C, Q345D, and Q345E; the primary difference between them lies in the impact test temperature.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\u0627\u0644\u0635\u0641<\/th>Impact Test<\/th>Typical Applications<\/th><\/tr><\/thead>
Q345A<\/strong><\/td>No impact test<\/td>General structures without low-temperature requirements<\/td><\/tr>
Q345B<\/strong><\/td>Impact test at 20\u00b0C<\/td>Structural components at normal temperatures<\/td><\/tr>
Q345C<\/strong><\/td>Impact test at 0\u00b0C<\/td>Structures in cold regions<\/td><\/tr>
Q345D<\/strong><\/td>Impact test at \u221220\u00b0C<\/td>Low-temperature environments<\/td><\/tr>
Q345E<\/strong><\/td>Impact test at \u221240\u00b0C<\/td>Extremely cold and severe environments<\/td><\/tr><\/tbody><\/table>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Q345 is a type of steel\u2014specifically, a low-alloy steel (with a carbon content of less than 0.2%)\u2014widely used in construction, bridges, vehicles, ships, and pressure vessels. The “Q” denotes the material’s yield strength, while the “345” indicates a yield value of approximately 345 MPa; this yield value decreases as the material thickness increases.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Difference in Chemical Composition\u2014Q345 Steel Plates<\/span><\/h4>
\u00a0<\/div>
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  • \u0627\u0644\u0635\u0641<\/li><\/ul><\/th>
C\u2264<\/th>Mn\u2264<\/th>Si\u2264<\/th>P\u2264<\/th>S\u2264<\/th>V<\/th>Al<\/th><\/tr><\/thead>
Q345A<\/td>0.20<\/td>1.7<\/td>0.55<\/td>0.045<\/td>0.045<\/td>0.02~0.15<\/td>\u2014<\/td><\/tr>
Q345B<\/td>0.20<\/td>1.7<\/td>0.55<\/td>0.040<\/td>0.040<\/td>0.02~0.15<\/td>\u2014<\/td><\/tr>
Q345C<\/td>0.20<\/td>1.7<\/td>0.55<\/td>0.035<\/td>0.035<\/td>0.02~0.15<\/td>\u22650.015<\/td><\/tr>
Q345D<\/td>0.20<\/td>1.7<\/td>0.55<\/td>0.030<\/td>0.030<\/td>0.02~0.15<\/td>\u22650.015<\/td><\/tr>
Q345E<\/td>0.20<\/td>1.7<\/td>0.55<\/td>0.025<\/td>0.025<\/td>0.02~0.15<\/td>\u22650.015<\/td><\/tr><\/tbody><\/table><\/div>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Product Series<\/span><\/strong><\/h4>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Q345A\u3001<\/span><\/p>

Q345B\u3001<\/span><\/p>

Q345C\u3001<\/span><\/p>

Q345D\u3001<\/span><\/p>

Q345E\u3001<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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General-purpose low-alloy high-strength plate; “E” denotes impact testing at -40\u00b0C.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Q345FRB\/C\/D\/E<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Steel plate for fire-resistant structures, complying with GB\/T 28415-2012.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Q345GJB\/GJC, etc.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Steel for high-rise buildings, such as Q345GJB-Z15<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Q345qE (bridge plate).<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Bridge steel (commonly available on the market).<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Q345R<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Steel for boilers and pressure vessels.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\u00a0<\/h3>

What other factors affect the strength of Q345?<\/span><\/h3>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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\u00a0<\/p>

1.Thickness<\/strong><\/p>

When the plate thickness is 16 mm or less, the yield strength remains at the standard 345 MPa; however, as the thickness increases to the 20\u201340 mm range, the yield strength typically drops to around 325 MPa; if the thickness increases further to 40\u201363 mm, the value may fall to 315 MPa or even lower.<\/p>

\u00a0<\/p>

2.Temperature<\/strong><\/p>

Low-temperature environments also significantly reduce the toughness of Q345. Although its strength values \u200b\u200bremain relatively stable, it is more prone to brittle fracture at sub-zero temperatures.<\/p>

\u00a0<\/p>

Avoiding Pitfalls in Model Selection: Focus on Elongation and Impact Toughness?<\/span><\/h4>

\u00a0<\/p>

When selecting Q345 steel, a comprehensive assessment of other mechanical properties is essential. First, elongation reflects a material’s deformability; while thin plates typically require high elongation to ensure good formability during processing, thick plates may prioritize static strength. Second, if the component is intended for low-temperature environments or subject to dynamic loads, impact toughness is a critical factor; standard Q345 can become brittle at sub-zero temperatures, so grades with superior low-temperature performance\u2014such as Q345D or Q345E\u2014should be selected instead.<\/p>

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What other types of Q345 steel plates are there that you might not be aware of?<\/span><\/h4>

\u00a0<\/p>

1.\u00a0 Hot-rolled flat steel:<\/strong> Features a mill-scale surface; suitable for structural load-bearing beams.<\/p>

2.\u00a0 Cold-rolled coil:<\/strong><\/p>

Mirror-like finish; transformed into protective underbody plating for vehicles.<\/p>

3.\u00a0 Galvanized finish: <\/strong><\/p>

Clad in silver-like armor; withstands 20 years of service in humid environments without rusting.<\/p>

4.\u00a0 Laser cutting: <\/strong><\/p>

Precision down to the width of a human hair; directly processed into excavator bucket teeth.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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A Guide to Avoiding Pitfalls When Buying<\/span>
Watch out for the following issues:<\/span><\/h4>

High-quality Q345 steel features a fine, metallic luster on its cross-section; the outer surface does not wrinkle when bent 90 degrees, and it produces a crisp, bell-like sound when struck.<\/p>

Thickness tolerance exceeding \u00b10.2mm:<\/strong> May result in assembly gaps.<\/p>

Lamination in the cross-section:<\/strong> A structural defect resembling the layers of a flaky pastry.<\/p>

Impact energy <34J at room temperature:<\/strong> Prone to brittle fracture in cold regions.<\/p>

Abnormal manganese content:<\/strong> Affects toughness after welding.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Q345 \u2014 The Subtle Relationship Between Composition and Properties<\/span><\/h4>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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\u00a0<\/p>

Balance of strength and toughness<\/strong><\/p>

\u00a0<\/p>

Increased manganese content will increase strength, but excess will reduce low-temperature toughness<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\u00a0<\/p>

Welding performance<\/strong><\/p>

Only when the carbon equivalent is controlled below 0.40% can good welding performance be ensured.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\u00a0<\/p>

Weather resistance<\/strong><\/p>

Appropriate addition of copper, chromium and other elements can improve resistance to atmospheric corrosion<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\u00a0<\/p>

Processing performance<\/strong><\/p>

Excessive silicon content will increase the difficulty of cold processing<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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High Strength Low Alloy Steel Plate Q345 Q345A Q345B <\/strong><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"

High Strength Low Alloy Steel Plate Q345 Q345A Q345B<\/p>\n

Q345A\u3001<\/span><\/p>\n

Q345B\u3001<\/span><\/p>\n

Q345C\u3001<\/span><\/p>\n

Q345D\u3001<\/span><\/p>\n

Q345E\u3001<\/span><\/p>\n

Q345FRB\u3001Q345FRC\u3001Q345FRD\u3001Q345FRE\u3001<\/span><\/p>\n

Q345GJD\u3001Q345BZ15\uff08Z15\/Z25\/Z35\uff09\u3001Q345R\u3001<\/span><\/p>\n

Contact JBL<\/span> <\/strong>\u2014 Inquire about the latest prices.<\/p>\n

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