Q550D QT Carbon Steel Plate GB/T 16270 Supplier

Q550D, also searched as GB/T 16270 Q550D, Q550D QT plate, Q550D carbon steel plate, Q550D steel plate and Q550D quenched and tempered plate, is the 550 MPa quality-grade-D grade in GB/T 16270. That standard covers high-strength structural steel plate delivered quenched and tempered. Q is the yield symbol, 550 is the thin-plate minimum yield in MPa, and D is the quality letter for Charpy impact at −20°C.

Q550D is the middle impact letter in the 550 MPa family. C is 0°C. D is −20°C. E is −40°C. F is −60°C. Equipment builders use it when the frame needs 550 MPa and the site sees sub-zero nights, but the specification does not call for −40°C. It is not a substitute for Q550C, and it is not a substitute for Q550E.

EN 10025-6 does not have a −20°C letter. S550Q is tested at 0°C. S550QL is tested at −40°C and lines up more closely with Q550E. Q550D sits between those two. On the US side, the nearest yield comparison is ASTM A656 Grade 80, which is also 80 ksi / 550 MPa minimum yield. A656 is high-strength low-alloy plate, not this QT book, so it is a strength comparison only. Dual mark only when both books are fully met. See EN 10025-6 steel plate.

SHH STEEL is a global steel mill sourcing partner and steel manufacturer and exporter, mill-direct, China origin. We source Q550D from first-line QT 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 high strength low alloy plates and structural steel plates.

Nearby pages that buyers compare, but must not swap blindly, include S550Q, S550QL and A572 Gr.50.

Heat analysis is the mill ladle table in GB/T 16270. Product analysis, when ordered, follows GB/T 222. Grade D is tighter on phosphorus and sulfur than grade C, because the impact test is colder. Mills add Nb, V, Ti or Al for grain refinement, and may add Cr, Ni, Mo or B by thickness. The certificate shows the elements actually used.

Heat Analysis and Product Analysis — GB/T 16270 Q550D

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 S355JR.

Buyers search Q550D mechanical properties, Q550D yield strength, GB/T 16270 Q550D tensile and Q550D impact −20°C.

Tensile and impact — GB/T 16270 Q550D

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

Yield steps down with thickness. A 550 MPa name on 20 mm plate is not the minimum on a 120 mm flange. ASTM A656 Grade 80 is also 550 MPa / 80 ksi minimum yield, but it does not carry this −20°C QT table. SHH STEEL quotes the thickness band on the offer.

Density is 7.85 g/cm³. Hardness after temper is a mill control, not a design value. Z15, Z25 or Z35 through-thickness tensile is an extra.

There is no official one-to-one substitute for Q550D. What buyers compare is a 550 MPa QT plate tested at −20°C.

In the United States the nearest yield name is ASTM A656/A656M Grade 80. Grade 80 is 80 ksi / 550 MPa minimum yield and 90 ksi / 620 MPa minimum tensile. That matches the Q550D thin-plate yield number. It does not match the GB/T 16270 quench-and-temper route, and it does not match the −20°C quality letter. A572 Gr.65 is only 65 ksi / 450 MPa. A514 Grade Q is 100 ksi / 690 MPa QT plate, closer to Q690 than to Q550D. SHH STEEL will not stamp A656 Grade 80 or A514 on a Q550D certificate unless the purchase order names both books and both tables are met.

EN 10025-6 jumps from 0°C on S550Q to −40°C on S550QL. Q550D sits in the gap. In Japan, SM570 is a welded structural grade, not this plate.

Buyers pick Q550D when a welded frame, boom or chassis wants 550 MPa yield, QT delivery and impact at −20°C. Search phrases such as Q550D steel plate, GB/T 16270 Q550D and Q550D QT plate all point here.

It is the wrong plate for a 0°C-only file that can use Q550C. It is the wrong plate for a −40°C mine site. That work is Q550E. It is the wrong plate for a US file that actually names ASTM A656 Grade 80. That work stays on A656 unless the order also accepts GB/T 16270. It is the wrong plate for a 100 ksi QT flange. That work is A514 Grade Q. 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 16270 and quality grade D at 550 MPa.

Q550D is weldable QT carbon plate. The plate has already been quenched and tempered. A procedure written for S355JR is not a Q550D procedure. A procedure qualified only on Q550C at 0°C may miss the −20°C coupon. A procedure written for ASTM A656 Grade 80 is a useful strength check, not a finished WPS.

Typical consumables are matching 550–620 MPa low-hydrogen electrodes or wires, qualified on a QT 550 MPa family. E7018-class electrodes are under-matched if the joint must develop full plate strength. A procedure written for S550QL is a useful starting point after the −20°C test temperature is checked.

Preheat follows thickness, hydrogen and the approved WPS. Interpass temperature should stay below the mill temper range, or local yield can drop. After heavy cold forming, a stress relief may be required. The fabricator owns the WPS. SHH STEEL can share mill heat data, product analysis and carbon equivalent for that review.

Usual delivery from SHH STEEL for Q550D is quenched and tempered. Austenitize typically in the 880–930°C range, quench, then temper in the window that holds 550 MPa yield and the −20°C impact. Exact temperatures stay on the mill process sheet.

Do not order Q550D as as-rolled or TMCP unless the contract leaves GB/T 16270. ASTM A656 Grade 80 is not a QT delivery instruction for this page. Stress relief after fabrication, if used, must stay below the original temper temperature.

The certificate lists GB/T 16270 Q550D, 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 S550Q, S550QL or A656 Grade 80 is available only when both books are fully met.

Usual supply range from SHH STEEL for Q550D QT carbon steel plate:

• Thickness: commonly 8 mm – 100 mm, heavier plate to 150 mm by enquiry
• Width: 1500 mm – 3800 mm
• Length: 3000 mm – 12000 mm

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

Dimensional limits for Q550D follow GB/T 709 unless the purchase order names another table.

Typical thickness tolerance idea for Q550D QT plate

Width on 1500–3800 mm plate is commonly held to about ±20–25 mm unless a tighter extra is named. Length on 3000–12000 mm plate is commonly held to about +50 / 0 mm or ±25 mm by mill practice. Flatness after QT follows the agreed class. SHH STEEL will not assume a zero-minus extra on Q550D unless the order says so.

Q550D already defines 550 MPa yield, QT delivery and −20°C impact. Extra items still have to be written on the purchase order.

Book name. Write GB/T 16270 Q550D. Do not write only Q550D.

Impact. Grade D is −20°C. Write a higher energy if the owner requires it.

US comparison. Write ASTM A656 Grade 80 only if dual mark is required.

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.

Heat-treatment record. QT temperatures when the inspector asks.

Identification. Heat number, Q550D, thickness and mill logo.

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

Q550D is the plate for a 550 MPa QT file tested at −20°C. It is the wrong plate for a painted warehouse that can use S355JR. It is the wrong plate for a 100 ksi QT member.

SHH STEEL sources Q550D from first-line Chinese QT 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: 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 30 mm, 32 mm, 40 mm, 50 mm, 60 mm, 80 mm, 100 mm.

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 QT rolling about 35–45 days; 3.2 inspection about 45–60 days.

SHH STEEL is a global steel mill sourcing partner and steel manufacturer and exporter, mill-direct, China origin. For Q550D that means mill-direct QT price, not a multi-layer stockist mark-up. We buy from mills that already run the 550 MPa quench-and-temper route, 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 35–45 days, 3.2 inspection about 45–60 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 16270 Q550D, keep the QT route, and do not ship Q550C or ASTM A656 Grade 80 as this plate. We will not change D to C to save a cold test, and we will not treat Q550D as S355 or as A514. If the drawing needs −40°C, we will move the inquiry to Q550E and keep the price on the right grade.

Q550D QT carbon steel plate to GB/T 16270 is 550 MPa quenched-and-tempered structural plate with impact at −20°C. The nearest US yield comparison is ASTM A656 Grade 80. Whether the inquiry says Q550D, GB/T 16270 Q550D, Q550D QT plate or Q550D carbon steel plate, SHH STEEL as a global steel mill sourcing partner supplies plate with Q550D chemistry, heat and product analysis as ordered, GB/T 709 tolerances and EN 10204 3.1 or 3.2 certification.

SHH STEEL supplies Q550D QT Carbon 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, QT route, cutting, UT, 3.2 inspection or a worldwide quotation.

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