Q355B Steel Plate GB/T 1591 Supplier

Q355B, also searched as GB/T 1591 Q355B, Q355B steel plate, Q355B plate, Q355 B and the older name Q345B, is the 355 MPa quality-grade-B grade in GB/T 1591-2018. That standard covers high-strength low-alloy structural steels. Q is the yield symbol, 355 is the thin-plate minimum yield in MPa, and B is the quality letter for Charpy impact at +20°C.

The 2018 edition replaced Q345 with Q355 and cancelled quality grade A. A drawing that still says Q345B is usually reviewed against Q355B, but the yield name, impact letter and thickness band still have to match the purchase order. Q355B on this page is the hot-rolled grade. It has no N and no M suffix.

Q355NB is normalized or normalizing-rolled. Q355MB is thermomechanical rolled. Those are different delivery conditions, different carbon-equivalent windows and different thickness limits. A hot-rolled Q355B certificate cannot be stamped NB or MB. Grade C is 0°C, D is −20°C, and E is −40°C. F exists on some M grades, not on hot-rolled Q355B.

The closest European comparison is EN 10025-2 S355JR, also tested at +20°C. S355J0 is 0°C and lines up more closely with Q355C. S355J2 is −20°C and lines up more closely with Q355D. On the US side, A572 Gr.50 is 50 ksi / 345 MPa, one step lower, and it is not a B-letter twin. JIS G3106 SM490B is the usual Japanese comparison. Dual mark only when both books are fully met. See EN 10025-2 and high strength low alloy plates.

SHH STEEL is a global steel mill sourcing partner and steel manufacturer and exporter, mill-direct, China origin. We source Q355B from first-line structural mills, print heat analysis and product analysis when ordered, and ship plate to fabricators in the United States, Europe, the Middle East, Southeast Asia, Africa and South America. Related pages include structural steel plates and the products index.

Nearby pages that buyers compare, but must not swap blindly, include S355JR, A572 Gr.50 and ASTM A36.

Heat analysis is the mill ladle table in GB/T 1591-2018 for hot-rolled Q355. Product analysis, when ordered, follows GB/T 222. Q355B is a carbon-manganese HSLA plate. Mills may add Nb, V or Ti for grain refinement. The certificate shows the elements actually used. Grade B allows a wider phosphorus and sulfur window than grade D or E. That is acceptable at +20°C. It is not a reason to use Q355B on a −20°C drawing.

Heat Analysis and Product Analysis — GB/T 1591 Q355B, hot rolled

Carbon equivalent is limited by thickness in the standard. A thick flange can have a lower CEV cap than a 12 mm web. If the purchase order writes product analysis, SHH STEEL prints both columns and the thickness band used for the tensile test. Do not treat this chemistry as weathering plate. Do not treat it as quenched-and-tempered Q460C under GB/T 16270.

Buyers search Q355B mechanical properties, Q355B yield strength, GB/T 1591 Q355B tensile and Q355B impact 20°C.

Tensile and impact — GB/T 1591 Q355B, hot rolled

Impact energy is the average of three longitudinal Charpy V-notch specimens, commonly 34 J minimum at +20°C. One value may fall below the table, but not below 70% of that value. Write a higher energy on the order if the owner requires it.

Yield steps down with thickness. A 355 MPa name on 12 mm plate is not the minimum on a 40 mm flange. 355 MPa is about 51.5 ksi. A572 Gr.50 is 50 ksi and is not this book. SHH STEEL quotes the thickness band on the offer.

Density is 7.85 g/cm³. Hardness is not a design value for this grade. Z15, Z25 or Z35 through-thickness tensile is an extra, not part of the B letter.

There is no official one-to-one substitute for Q355B. What buyers compare is a 355 MPa hot-rolled plate tested at +20°C.

The usual European pair is S355JR. S355J0 is colder and closer to Q355C. S355J2 is closer to Q355D. In the United States, A572 Gr.50 is 50 ksi / 345 MPa. A36 is 36 ksi and is well below this yield. In Japan, SM490B is the usual comparison. Old DIN St52-3 still appears on legacy drawings. SHH STEEL will not stamp S355JR or A572 on a Q355B certificate unless the purchase order names both books and both tables are met.

Buyers pick Q355B when a building, bridge member, equipment frame or welded fabrication wants about 355 MPa yield, hot-rolled delivery and impact at +20°C. Search phrases such as Q355B steel plate, GB/T 1591 Q355B and Q345B all point here after the 2018 revision is checked.

It is the wrong plate for a 0°C file. That work is Q355C. It is the wrong plate for a −20°C file. That work is Q355D. It is the wrong plate when the drawing says normalized. That work is Q355NB. It is the wrong plate when the drawing says TMCP. That work is Q355MB. It is the wrong plate for a quenched-and-tempered 460 MPa boom. That work is Q460C under GB/T 16270. It is the wrong plate for a pressure vessel. That work sits on ASTM A516 or pressure vessel steel plates.

SHH STEEL supplies this plate when the drawing names GB/T 1591 and quality grade B at 355 MPa, hot rolled.

Q355B is a weldable HSLA structural plate. Carbon is controlled, and many heats use Nb, V or Ti. A procedure written for mild A36 can be a starting point on thin plate, but it is not a finished WPS for thick Q355B. Carbon equivalent rises with thickness, and the standard caps CEV by band.

Typical consumables are matching 50 ksi / 355 MPa low-hydrogen electrodes or wires. E7018-class electrodes are common on shop joints that do not need full plate strength in the weld metal. A procedure written for S355JR is the usual European reference after chemistry is checked. Preheat follows thickness, hydrogen and the approved WPS. Thick plate and restrained joints need more preheat than a 10 mm web.

The fabricator owns the WPS. SHH STEEL can share mill heat data, product analysis and carbon equivalent for that review. Do not use a Q355B procedure on Q355MB without checking the TMCP carbon equivalent.

Usual delivery from SHH STEEL for Q355B is hot rolled. The plate is not normalized and not thermomechanical rolled unless the order changes the grade to Q355NB or Q355MB.

Do not order Q355B as quenched and tempered. That route belongs to GB/T 16270, not to this page. Stress relief after fabrication, if used, should be agreed before cutting, because a high temper can move yield on a controlled-rolled heat.

The certificate lists GB/T 1591 Q355B, heat number, heat analysis, product analysis when ordered, tensile by thickness band, and +20°C impact. Certificates may be EN 10204 3.1 or EN 10204 3.2. Dual marking to S355JR is available only when both books are fully met.

Usual supply range from SHH STEEL for Q355B steel plate:

• Thickness: commonly 6 mm – 100 mm, heavier plate to 150 mm by enquiry, up to 250 mm by mill confirmation
• Width: 1500 mm – 3000 mm, wider by enquiry
• Length: 3000 mm – 12000 mm

Cut-to-size webs, flanges, base plates and gussets are available. Browse more sizes on structural steel plates.

Dimensional limits for Q355B follow GB/T 709 unless the purchase order names EN 10029 or another table.

Typical thickness tolerance idea for Q355B plate

Width on 1500–3000 mm plate is commonly held to about +20 / 0 mm or ±25 mm unless a tighter extra is named. Length on 3000–12000 mm plate is commonly held to about +50 / 0 mm. Flatness follows the agreed class. SHH STEEL will not assume a zero-minus extra on Q355B unless the order says so.

Q355B already defines 355 MPa yield, hot-rolled delivery and +20°C impact. Extra items still have to be written on the purchase order.

Book name. Write GB/T 1591 Q355B. Do not write only Q355, and do not write Q345B if the mill must stamp the 2018 grade.

Impact. Grade B is +20°C. Write a higher energy if the owner requires it. Do not expect a −20°C result unless the grade is changed to D.

Delivery condition. Write hot rolled. Write Q355NB or Q355MB if normalized or TMCP is required.

EN or US comparison. Write S355JR or A572 Gr.50 only if dual mark is required and both tables are met.

Product analysis. Write it if the file needs the second chemistry column.

Through-thickness. Z15, Z25 or Z35 when the joint is loaded through the thickness.

NDE. UT to GB/T 2970 or the named class.

Identification. Heat number, Q355B, thickness and mill logo.

Third-party witness. EN 10204 3.2 with SGS, TÜV, BV, ABS or the inspector named.

Q355B is the plate for a 355 MPa hot-rolled file tested at +20°C. It is the wrong plate for a painted weathering facade that needs corten. It is the wrong plate for a 690 MPa QT boom.

SHH STEEL sources Q355B from first-line Chinese structural mills and ships it on worldwide terms. Partner mills include Wuyang (Wugang), Angang, Shougang, Hanye, Anyang Iron and Steel, Baosteel, Xinyu, Xingcheng and other qualified mills when the size requires it.

Mill test certificates are issued to EN 10204 3.1 as standard. EN 10204 3.2 is arranged when the order names a third-party hold point.

Usual rolling thickness: 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 30 mm, 40 mm, 50 mm, 60 mm, 80 mm, 100 mm. Heavier plate is confirmed before order.

Processing: CNC or flame cutting, bevel, flattening, shot blast, UT to the named class.

Trade terms: FOB Shanghai main, CIF destination available. Payment: TT, LC, or TT + LC.

Ocean time from Shanghai: US West 14–18 days; US Gulf 28–35 days; Rotterdam / Antwerp 28–35 days; Jebel Ali 18–25 days; Singapore 7–12 days; other ports quoted.

Third-party: SGS, TÜV, BV, ABS, CCS, GL, VL, DNV, RINA, NK, KR, or the inspector named.

SHH STEEL is a global steel mill sourcing partner with mill partnerships in China. We supply GB, ASTM, ASME, EN, DIN and JIS steel to buyers in the United States, Europe, the Middle East, Southeast Asia, Africa and South America. Origin is mill-direct, China origin.

SHH STEEL has supplied steel plates to the USA, Mexico, Argentina, Peru, El Salvador, Spain, Netherlands, Germany, UAE, Saudi Arabia, South Africa, India, Thailand, Singapore, Vietnam, the Philippines, Japan and Korea.

Typical lead time: ex-stock 5–7 days when plate is in yard; standard rolling about 25–40 days; 3.2 inspection about 35–45 days.

SHH STEEL is a global steel mill sourcing partner and steel manufacturer and exporter, mill-direct, China origin. For Q355B that means mill-direct structural price, not a multi-layer stockist mark-up. We buy from mills that already roll GB/T 1591, so the heat carries the +20°C impact without a second upgrade charge.

Delivery is short when the size is in rolling range: ex-stock 5–7 days, standard heat about 25–40 days, 3.2 inspection about 35–45 days. Cutting, bevel and UT can run in the same window. FOB Shanghai is the main term. CIF to US West, US Gulf, Rotterdam, Jebel Ali and Singapore is quoted on the same file.

Experience on this grade is simple: print GB/T 1591 Q355B, keep the hot-rolled route, and do not ship Q355C or Q355MB as B. We will not change B to D on the certificate to win an order, and we will not treat Q355B as A36. If the drawing needs normalized plate, we will move the inquiry to Q355NB and keep the price on the right grade.

Q355B steel plate to GB/T 1591 is 355 MPa hot-rolled structural plate with impact at +20°C. The nearest European comparison is S355JR. A572 Grade 50 is 345 MPa and is not a substitute. Q355NB and Q355MB are different processes. Whether the inquiry says Q355B, GB/T 1591 Q355B, Q355B steel plate or Q345B, SHH STEEL as a global steel mill sourcing partner supplies plate with Q355B chemistry, heat and product analysis as ordered, GB/T 709 tolerances and EN 10204 3.1 or 3.2 certification.

SHH STEEL supplies Q355B Steel Plate to the United States, Europe, the Middle East, Africa, Asia and the Americas for work that actually names this grade.

Contact SHH STEEL for mill rolling, hot-rolled Q355B, cutting, UT, 3.2 inspection or a worldwide quotation.

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