Q420NB Steel Plate GB/T 1591 Supplier

Q420NB, also searched as GB/T 1591 Q420NB, Q420NB steel plate, Q420NB plate and Q420 NB, is the 420 MPa quality-grade-B grade delivered normalized or normalizing-rolled in GB/T 1591-2018. Q is the yield symbol, 420 is the thin-plate minimum yield in MPa, N is the delivery letter, and B is the quality letter for Charpy impact at +20°C.

The N is the point of this page. Hot-rolled GB/T 1591 Q420B has no N. Thermomechanical Q420MB has an M. A hot-rolled certificate cannot be stamped NB. A TMCP certificate cannot be stamped NB. Grade C is 0°C. D is −20°C. E is −40°C. Q420 sits above GB/T 1591 Q390NB and below GB/T 1591 Q460C. Do not drop a 420 MPa drawing onto a 390 MPa plate.

The closest process comparison is EN 10025-3 S420N, a normalized fine-grain grade, but that letter is tested at −20°C. EN 10025-3 S420NL is colder. EN 10025-4 S420M is TMCP and closer to Q420MB. On the US side, ASTM A572 Gr.60 is 60 ksi / 415 MPa, one step lower, and it is not an NB twin. JIS G3106 SM570 is a higher Japanese comparison. Dual mark only when both books are fully met. See EN 10025-3 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 Q420NB 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 EN 10025-3 S420N, ASTM A572 Gr.60 and GB/T 1591 Q420B.

Heat analysis is the mill ladle table in GB/T 1591-2018 for normalized Q420. Product analysis, when ordered, follows GB/T 222. Q420NB is a microalloyed HSLA plate. 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 Q420NB on a −20°C drawing. Mills may add Nb, V or Ti. The certificate shows the elements actually used.

Heat Analysis and Product Analysis — GB/T 1591 Q420NB, normalized

Carbon equivalent is limited by thickness in the standard. The N route often has a different CEV window from hot-rolled GB/T 1591 Q420B. 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 quenched-and-tempered GB/T 16270 Q460C. A 355 MPa file is GB/T 1591 Q355NB, not this grade.

Buyers search Q420NB mechanical properties, Q420NB yield strength, GB/T 1591 Q420NB tensile and Q420NB impact 20°C.

Tensile and impact — GB/T 1591 Q420NB, normalized

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 420 MPa name on 12 mm plate is not the minimum on a 40 mm flange. 420 MPa is about 61 ksi. ASTM A572 Gr.60 is 60 ksi and is not this book. SHH STEEL quotes the thickness band and the N condition 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.

A colder 420 MPa file is GB/T 1591 Q420E. A 460 MPa file is GB/T 1591 Q460D.

There is no official one-to-one substitute for Q420NB. What buyers compare is a 420 MPa normalized plate tested at +20°C.

EN 10025-3 S420N is the process comparison, but it is tested at −20°C. EN 10025-3 S420NL is colder. EN 10025-4 S420M is TMCP and closer to Q420MB. In the United States, ASTM A572 Gr.60 is 60 ksi / 415 MPa. ASTM A572 Gr.50 is 50 ksi and is well below this yield. ASTM A36 is 36 ksi. In Japan, JIS G3106 SM570 is a higher comparison. SHH STEEL will not stamp EN 10025-3 S420N or ASTM A572 Gr.60 on a Q420NB certificate unless the purchase order names both books and both tables are met.

Buyers pick Q420NB when a building, bridge member or welded fabrication wants about 420 MPa yield, a normalized or normalizing-rolled condition, and impact at +20°C. Search phrases such as Q420NB steel plate and GB/T 1591 Q420NB all point here.

It is the wrong plate when the drawing says hot rolled only. That work is GB/T 1591 Q420B. It is the wrong plate when the drawing says TMCP. That work is Q420MB, and the European file is often EN 10025-4 S420M. It is the wrong plate for a 0°C file. That work is Q420NC. It is the wrong plate for a −20°C file. That work is Q420ND, and the hot-rolled sister is GB/T 1591 Q420D. It is the wrong plate for a 390 MPa file. That work is GB/T 1591 Q390NB. It is the wrong plate for a 460 MPa file. That work is GB/T 1591 Q460E. 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, quality grade B, and the N condition at 420 MPa.

Q420NB is a weldable normalized HSLA structural plate. Carbon is controlled, and many heats use Nb, V or Ti. A procedure written for ASTM A36 is not a finished WPS for thick Q420NB. Carbon equivalent on the N route is not the same window as hot-rolled GB/T 1591 Q420B.

Typical consumables are matching 60 ksi / 420 MPa low-hydrogen electrodes or wires. E7018-class electrodes are under-matched if the joint must develop full plate strength. A procedure written for ASTM A572 Gr.60 is a useful strength 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 Q420NB procedure on Q420MB without checking the TMCP carbon equivalent.

Usual delivery from SHH STEEL for Q420NB is normalized or normalizing rolled. The plate is not hot rolled as GB/T 1591 Q420B and not thermomechanical rolled as Q420MB.

Normalizing is typically about 880–920°C, followed by air cooling, unless the mill uses a normalizing-rolling route that the standard accepts for the N letter. Do not order Q420NB as quenched and tempered. That route belongs to GB/T 16270. Stress relief after fabrication, if used, should be agreed before cutting.

The certificate lists GB/T 1591 Q420NB, heat number, delivery condition, 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 EN 10025-3 S420N is available only when both books are fully met.

Usual supply range from SHH STEEL for Q420NB steel plate:

• Thickness: commonly 8 mm – 80 mm, heavier plate to 100 mm by enquiry
• Width: 1500 mm – 2800 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 Q420NB follow GB/T 709 unless the purchase order names EN 10029 or another table.

Typical thickness tolerance idea for Q420NB plate

Width on 1500–2800 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 Q420NB unless the order says so.

Q420NB already defines 420 MPa yield, normalized delivery and +20°C impact. Extra items still have to be written on the purchase order.

Book name. Write GB/T 1591 Q420NB. Do not write only Q420, and do not write Q420B if the mill must stamp N.

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 Q420ND.

Delivery condition. Write normalized or normalizing rolled. Write GB/T 1591 Q420B if hot rolled is enough. Write Q420MB if TMCP is required.

EN or US comparison. Write EN 10025-3 S420N or ASTM A572 Gr.60 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, Q420NB, thickness and mill logo.

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

Q420NB is the plate for a 420 MPa normalized 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 under GB/T 16270.

SHH STEEL sources Q420NB 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. 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 an N heat is in yard; standard normalizing about 30–45 days; 3.2 inspection about 40–50 days.

SHH STEEL is a global steel mill sourcing partner and steel manufacturer and exporter, mill-direct, China origin. For Q420NB that means mill-direct structural price, not a multi-layer stockist mark-up. We buy from mills that can actually normalize or normalizing-roll the heat, so the N is on the certificate and not only in the enquiry.

Delivery is short when the size is in rolling range: ex-stock 5–7 days, standard N heat about 30–45 days, 3.2 inspection about 40–50 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 Q420NB, keep the normalized route, and do not ship GB/T 1591 Q420B or Q420MB as NB. We will not drop the N to save a furnace cycle, and we will not treat Q420NB as GB/T 1591 Q355B. If the drawing only needs hot-rolled plate, we will move the inquiry to Q420B and keep the price on the right condition.

Q420NB steel plate to GB/T 1591 is 420 MPa normalized structural plate with impact at +20°C. It is not hot-rolled GB/T 1591 Q420B and not TMCP Q420MB. The nearest European process comparison is EN 10025-3 S420N, and that grade is tested at −20°C. ASTM A572 Grade 60 is 415 MPa and is not a substitute. Whether the inquiry says Q420NB, GB/T 1591 Q420NB or Q420NB steel plate, SHH STEEL as a global steel mill sourcing partner supplies plate with Q420NB chemistry, heat and product analysis as ordered, GB/T 709 tolerances and EN 10204 3.1 or 3.2 certification.

SHH STEEL supplies Q420NB Steel Plate to the United States, Europe, the Middle East, Africa, Asia and the Americas for work that actually names the N condition.

Contact SHH STEEL for mill rolling, normalized Q420NB, cutting, UT, 3.2 inspection or a worldwide quotation.

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