Q550MC TMCP Steel Plate GB/T 1591 Supplier

Q550MC, also searched as GB/T 1591 Q550MC, Q550MC steel plate, Q550MC TMCP plate and Q550 MC, is the 550 MPa quality-grade-C grade delivered by thermomechanical controlled process in GB/T 1591-2018. Q is the yield symbol, 550 is the thin-plate minimum yield in MPa, M is the delivery letter, and C is the quality letter for Charpy impact at 0°C.

The M is the point of this page. A quenched-and-tempered certificate cannot be stamped MC. That route is GB/T 16270 Q550C. The 500 MPa TMCP sister at the same temperature is GB/T 1591 Q500MC. The 460 MPa TMCP sister is GB/T 1591 Q460MC. The full family sits on GB/T 1591. Do not drop a 550 MPa drawing onto a 500 MPa plate, and do not upgrade it to GB/T 16270 Q620C without a price check.

EN 10025-4 stops at S460M and S460ML. There is no S550M. The usual European comparison is EN 10025-6 S550Q, which is quenched and tempered, not TMCP. EN 10025-4 S460M is one yield step lower and tested at −20°C. EN 10025-6 is the QT book. On the US side, ASTM A514 is about 100 ksi / 690 MPa and is quenched and tempered, so it is not an MC twin. ASTM A572 Gr.55 is 55 ksi. Dual mark only when both books are fully met. See 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 Q550MC from first-line structural mills that can actually run the TMCP schedule at 550 MPa, 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 GB/T 1591 Q500MD, GB/T 16270 Q550D and ASTM A572 Gr.55.

Heat analysis is the mill ladle table in GB/T 1591-2018 for TMCP Q550. Product analysis, when ordered, follows GB/T 222. Q550MC is a microalloyed HSLA plate. Grade C is tighter on phosphorus and sulfur than grade B, because the impact test is at 0°C. Mills may add Nb, V or Ti, and some heats use nickel, chromium or molybdenum to hold the 550 MPa window. The certificate shows the elements actually used. TMCP chemistry is often leaner than a QT heat of the same yield, because the rolling schedule does part of the strengthening.

Heat Analysis and Product Analysis — GB/T 1591 Q550MC, TMCP

Carbon equivalent is limited by thickness in the standard. The M route often has a lower CEV window than quenched-and-tempered GB/T 16270 Q550C. If the purchase order writes product analysis, SHH STEEL prints both columns and the thickness band used for the tensile test. A 500 MPa file is GB/T 1591 Q500MC, not this grade.

Buyers search Q550MC mechanical properties, Q550MC yield strength, GB/T 1591 Q550MC tensile and Q550MC impact 0°C.

Tensile and impact — GB/T 1591 Q550MC, TMCP

Impact energy is the average of three longitudinal Charpy V-notch specimens, commonly 34 J minimum at 0°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 550 MPa name on 12 mm plate is not the minimum on a 40 mm flange. 550 MPa is about 80 ksi. ASTM A514 is about 100 ksi and is not this book. SHH STEEL quotes the thickness band and the M 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 C letter.

A colder QT file is GB/T 16270 Q550D. A 460 MPa file is GB/T 1591 Q460MC.

There is no official one-to-one substitute for Q550MC. What buyers compare is a 550 MPa TMCP plate tested at 0°C.

EN 10025-4 has no S550M. EN 10025-6 S550Q is the strength comparison, but it is quenched and tempered and tested at −20°C. EN 10025-4 S460M is the nearest TMCP book grade and is one step lower. EN 10025-2 S355JR is +20°C and only 355 MPa. In the United States, ASTM A514 is about 100 ksi and is quenched and tempered. ASTM A572 Gr.55 is 55 ksi. ASTM A36 is 36 ksi and is well below this yield. SHH STEEL will not stamp EN 10025-6 S550Q or ASTM A514 on a Q550MC certificate unless the purchase order names both books and both tables are met.

Buyers pick Q550MC when a building, bridge member or welded fabrication wants about 550 MPa yield, a TMCP condition, and impact at 0°C. Search phrases such as Q550MC steel plate and GB/T 1591 Q550MC all point here. The family index is GB/T 1591.

It is the wrong plate when the drawing says quenched and tempered.
That work is GB/T 16270 Q550C. It is the wrong plate for a −20°C file. That work is Q550MD, and the QT sister is GB/T 16270 Q550D.
It is the wrong plate for a −40°C file. That work is Q550ME, and the QT sister is GB/T 16270 Q550E. It is the wrong plate for a 500 MPa file.

That work is GB/T 1591 Q500MC or GB/T 1591 Q500ME.
It is the wrong plate for a 620 MPa file. That work is GB/T 16270 Q620C. 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 C, and the M condition at 550 MPa.

Q550MC is a weldable TMCP 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 Q550MC. Carbon equivalent on the M route is often lower than quenched-and-tempered GB/T 16270 Q550C, which helps the root pass, but the TMCP microstructure still needs a qualified procedure. A procedure qualified only at +20°C may miss the 0°C coupon.

Typical consumables are matching 80–90 ksi 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.55 does not cover 550 MPa. Preheat follows thickness, hydrogen and the approved WPS. Heat input should stay inside the mill window. A very high heat input can soften the TMCP zone next to the weld.

The fabricator owns the WPS. SHH STEEL can share mill heat data, product analysis and carbon equivalent for that review. Do not use a Q550MC procedure on GB/T 1591 Q420MB without checking the lower-yield carbon equivalent. Do not use it on GB/T 1591 Q500MC either if the joint must develop 550 MPa.

Usual delivery from SHH STEEL for Q550MC is thermomechanical controlled process. The plate is not quenched and tempered as GB/T 16270 Q550C.

TMCP combines controlled rolling and accelerated cooling. Finish rolling is held in the non-recrystallization range, then the plate is cooled on the run-out table to a finish temperature the mill records. Do not order Q550MC as quenched and tempered. That route belongs to GB/T 16270. Stress relief after fabrication, if used, should be agreed before cutting, because a high temper can move the TMCP properties.

The certificate lists GB/T 1591 Q550MC, heat number, delivery condition, heat analysis, product analysis when ordered, tensile by thickness band, and 0°C impact. Certificates may be EN 10204 3.1 or EN 10204 3.2. Dual marking to EN 10025-6 S550Q is available only when both books are fully met. S550Q is not a TMCP grade.

Usual supply range from SHH STEEL for Q550MC steel plate:

• Thickness: commonly 8 mm – 40 mm, heavier plate to 50 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 Q550MC follow GB/T 709 unless the purchase order names EN 10029 or another table.

Typical thickness tolerance idea for Q550MC 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 Q550MC unless the order says so.

Q550MC already defines 550 MPa yield, TMCP delivery and 0°C impact. Extra items still have to be written on the purchase order.

Book name. Write GB/T 1591 Q550MC. Do not write only Q550, and do not write GB/T 16270 if the mill must stamp M. The family page is GB/T 1591.

Impact. Grade C is 0°C. Write a higher energy if the owner requires it. Do not expect a −20°C result unless the grade is changed.

Delivery condition. Write thermomechanical controlled process. Write GB/T 16270 Q550C if quenched and tempered is required.

EN or US comparison. Write EN 10025-6 S550Q or ASTM A514 only if dual mark is required and both tables are met. S550Q is QT, not TMCP.

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, Q550MC, thickness and mill logo.

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

Q550MC is the plate for a 550 MPa TMCP file tested at 0°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. A colder QT file is GB/T 16270 Q550E.

SHH STEEL sources Q550MC 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. 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 M heat is in yard; standard TMCP about 35–50 days; 3.2 inspection about 45–55 days

SHH STEEL is a global steel mill sourcing partner and steel manufacturer and exporter, mill-direct, China origin. For Q550MC that means mill-direct structural price, not a multi-layer stockist mark-up. We buy from mills that can actually run the TMCP schedule at 550 MPa, so the M 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 M heat about 35–50 days, 3.2 inspection about 45–55 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 Q550MC, keep the TMCP route, and do not ship GB/T 16270 Q550C as MC. We will not drop the M to save a cooling cycle, and we will not change C to B to save a cold test. If the drawing needs quenched and tempered plate, we will move the inquiry to Q550C under GB/T 16270. If the drawing needs 500 MPa, we will move it to GB/T 1591 Q500MD or GB/T 1591 Q500ME.

Q550MC steel plate to GB/T 1591 is 550 MPa TMCP structural plate with impact at 0°C. It is not quenched-and-tempered GB/T 16270 Q550C. EN 10025-4 has no S550M. EN 10025-6 S550Q is the strength comparison and is QT. ASTM A514 is about 690 MPa and is not a substitute. Whether the inquiry says Q550MC, GB/T 1591 Q550MC or Q550MC TMCP plate, SHH STEEL as a global steel mill sourcing partner supplies plate with Q550MC chemistry, heat and product analysis as ordered, GB/T 709 tolerances and EN 10204 3.1 or 3.2 certification.

SHH STEEL supplies Q550MC Steel Plate to the United States, Europe, the Middle East, Africa, Asia and the Americas for work that actually names the M condition. The grade family is listed on GB/T 1591.

Contact SHH STEEL for mill rolling, TMCP Q550MC, cutting, UT, 3.2 inspection or a worldwide quotation.

Q550MC, Q550MC steel plate, GB/T 1591 Q550MC, Q550MC TMCP, Q550MC supplier, SHH STEEL