Q420D Steel Plate GB/T 1591 Supplier

Q420D, also searched as GB/T 1591 Q420D, Q420D steel plate, Q420D plate and Q420 D, is the 420 MPa quality-grade-D grade in GB/T 1591-2018. That standard covers high-strength low-alloy structural steels. Q is the yield symbol, 420 is the thin-plate minimum yield in MPa, and D is the quality letter for Charpy impact at −20°C.

Q420D on this page is the hot-rolled grade. It has no N and no M suffix. Q420ND is normalized or normalizing-rolled. Q420MD is thermomechanical rolled. Those are different delivery conditions, different carbon-equivalent windows and different thickness limits. A hot-rolled Q420D certificate cannot be stamped ND or MD. Grade B is +20°C. C is 0°C. E is −40°C. F exists on some M grades, not on hot-rolled Q420D.

The closest European comparison is EN 10025-3 S420N, a normalized fine-grain grade tested at −20°C, not a hot-rolled twin. EN 10025-3 S420NL is colder. EN 10025-4 S420M is the TMCP comparison and lines up more closely with Q420MD. On the US side, ASTM A572 Gr.60 is 60 ksi / 415 MPa, one step lower, and it is not a D-letter twin. JIS G3106 SM570 is higher yield and is not a swap. 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 Q420D 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 ASTM A36.

Heat analysis is the mill ladle table in GB/T 1591-2018 for hot-rolled Q420. Product analysis, when ordered, follows GB/T 222. Q420D is a microalloyed HSLA plate. Grade D is tighter on phosphorus and sulfur than grade B or C, because the impact test is at −20°C. Mills may add Nb, V or Ti. The certificate shows the elements actually used.

Heat Analysis and Product Analysis — GB/T 1591 Q420D, 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 GB/T 16270 Q460D.

Buyers search Q420D mechanical properties, Q420D yield strength, GB/T 1591 Q420D tensile and Q420D impact −20°C.

Tensile and impact — GB/T 1591 Q420D, 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 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 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 D letter.

There is no official one-to-one substitute for Q420D. What buyers compare is a 420 MPa plate tested at −20°C.

EN 10025-3 S420N is normalized and also tested at −20°C. EN 10025-3 S420NL is colder. EN 10025-4 S420M is TMCP and closer to Q420MD than to this hot-rolled page. EN 10025-4 S420ML is the colder TMCP letter. In the United States, ASTM A572 Gr.60 is 60 ksi / 415 MPa. ASTM A572 Gr.65 is 65 ksi / 450 MPa and is one step higher. ASTM A36 is 36 ksi and is well below this yield. In Japan, JIS G3106 SM570 is higher. SHH STEEL will not stamp EN 10025-3 S420N or ASTM A572 Gr.60 on a Q420D certificate unless the purchase order names both books and both tables are met.

Buyers pick Q420D when a bridge, building member, equipment frame or welded fabrication wants about 420 MPa yield, hot-rolled delivery and impact at −20°C. Search phrases such as Q420D steel plate and GB/T 1591 Q420D all point here.

It is the wrong plate for a +20°C file that can use Q420B. It is the wrong plate for a 0°C file that can use Q420C. It is the wrong plate for a −40°C file. That work is Q420E. It is the wrong plate when the drawing says normalized. That work is Q420ND, and the European file is often EN 10025-3 S420N. It is the wrong plate when the drawing says TMCP. That work is Q420MD, and the European file is often EN 10025-4 S420M. It is the wrong plate for a quenched-and-tempered 460 MPa boom. That work is GB/T 16270 Q460D. 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 D at 420 MPa, hot rolled.

Q420D is a weldable 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 Q420D. Carbon equivalent rises with thickness, and the standard caps CEV by band. A procedure qualified only at +20°C may miss the −20°C coupon.

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 and the −20°C coupon are 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 Q420D procedure on Q420MD without checking the TMCP carbon equivalent.

Usual delivery from SHH STEEL for Q420D is hot rolled. The plate is not normalized and not thermomechanical rolled unless the order changes the grade to Q420ND or Q420MD.

Do not order Q420D 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 Q420D, 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 EN 10025-3 S420N is available only when both books are fully met.

Usual supply range from SHH STEEL for Q420D steel plate:

• Thickness: commonly 8 mm – 80 mm, heavier plate to 100 mm by enquiry
• 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 Q420D follow GB/T 709 unless the purchase order names EN 10029 or another table.

Typical thickness tolerance idea for Q420D 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 Q420D unless the order says so.

Q420D already defines 420 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 Q420D. Do not write only Q420.

Impact. Grade D is −20°C. Write a higher energy if the owner requires it. Do not expect a −40°C result unless the grade is changed to E.

Delivery condition. Write hot rolled. Write Q420ND or Q420MD if normalized or 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, Q420D, thickness and mill logo.

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

Q420D is the plate for a 420 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 under GB/T 16270.

SHH STEEL sources Q420D 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 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 Q420D 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 Q420D, keep the hot-rolled route, and do not ship Q420C or Q420MD as D. We will not change D to C on the certificate to save a cold test, and we will not treat Q420D as ASTM A36. If the drawing needs normalized plate, we will move the inquiry to Q420ND and keep the price on the right grade.

Q420D steel plate to GB/T 1591 is 420 MPa hot-rolled structural plate with impact at −20°C. The nearest European comparison is EN 10025-3 S420N, and that grade is normalized. ASTM A572 Grade 60 is 415 MPa and is not a substitute. Q420ND and Q420MD are different processes. Whether the inquiry says Q420D, GB/T 1591 Q420D or Q420D steel plate, SHH STEEL as a global steel mill sourcing partner supplies plate with Q420D chemistry, heat and product analysis as ordered, GB/T 709 tolerances and EN 10204 3.1 or 3.2 certification.

SHH STEEL supplies Q420D 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 Q420D, cutting, UT, 3.2 inspection or a worldwide quotation.

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