Q550D High Strength Structural Steel Plate

Strictly Compliant with GB/T 16270-2009 | Quenched & Tempered State | Thickness Up to 150mm | Excellent Low-Temperature Toughness | Custom Sizes Available

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Product Overview

Q550D is a high strength structural steel plate specified in GB/T 16270-2009 High strength structural steel plates in the quenched and tempered condition standard, replacing the old GB/T 16270-1996 version. The product is delivered in quenched + tempered state, with a maximum applicable thickness of 150mm (expanded from the original 100mm).

Q550D is smelted by oxygen converter or electric furnace, with strict control of chemical composition and carbon equivalent (CEV ≤0.50%), ensuring excellent high strength and superior low-temperature toughness (-20℃ impact resistance). It is widely used in engineering machinery, construction structures, port machinery, bridge engineering and other fields that require high load-bearing capacity and low-temperature stability.

According to GB/T 16270-2009 Appendix A, Q550D has approximate equivalent grades in European standards, and is the preferred material for high-strength structural components working in low-temperature environments (-20℃) in domestic and international engineering projects.

★ Key Standard Update:

GB/T 16270-2009 cancels the bending performance requirement, adds CEV carbon equivalent index, and deletes the delivery states of normalizing, normalizing+tempering and controlled rolling. It also defines Q550D grade with -20℃ low-temperature impact requirement and Z-direction performance requirement for thickness ≥15mm.

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Technical Specifications (GB/T 16270-2009)

All data is in accordance with the official GB/T 16270-2009 standard, the unit of chemical composition is mass fraction (wt%), and the mechanical properties are tested with transverse tensile samples and longitudinal impact samples.

Chemical Composition (wt%, Max) & Carbon Equivalent CEV

Grade	Thickness mm	C	Si	Mn	P	S	Cu	Cr	Ni	Mo	B	V	Nb	Ti	CEV
Q550D	≤50	0.20	0.80	1.70	0.025	0.015	0.50	1.50	2.00	0.70	0.0050	0.12	0.06	0.05	0.65
	>50~100	0.20	0.80	1.70	0.025	0.015	0.50	1.50	2.00	0.70	0.0050	0.12	0.06	0.05	0.77
	>100~150	0.20	0.80	1.70	0.025	0.015	0.50	1.50	2.00	0.70	0.0050	0.12	0.06	0.05	0.83

Note 1: At least one grain refinement element (Nb/Ti/V/Al) shall be added, the minimum content of at least one element is 0.015% (Als for Al), or Alt can be used instead of Als with a minimum of 0.018%.
Note 2: CEV calculation formula (GB/T 16270-2009): CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15.
Note 3: The chemical composition tolerance of finished steel plate complies with GB/T 222.
Note 4: Q550D has strict P/S control (P≤0.020%, S≤0.010%) to ensure low-temperature toughness and Z-direction performance.
Note 5: Q550D requires Z-direction performance test (Z15/Z25/Z35) for thickness ≥15mm to prevent lamellar tearing.

Mechanical Properties (GB/T 16270-2009)

Grade	Yield Strength ReH (MPa) ≥	Yield Strength ReH (MPa) ≥	Yield Strength ReH (MPa) ≥	Tensile Strength Rm (MPa)	Tensile Strength Rm (MPa)	Elongation after Fracture A (%)	Impact Absorption Energy KV2 (J)
Grade	≤50mm	>50~100mm	>100~150mm	≤100mm	>100~150mm	All Thickness	-20℃ (Longitudinal)
Q550D	550	530	490	640~820	590~770	16	47

Note 1: When the yield phenomenon is not obvious, Rp0.2 is used instead of ReH.
Note 2: The impact energy is the arithmetic mean of three samples, one sample is allowed to be lower than the specified value but not less than 70% of the specified value.
Note 3: For plates with thickness 8~12mm, 75% of the specified impact value is required for 10×7.5×55mm auxiliary samples; for 6~8mm, 50% for 10×5×55mm auxiliary samples; no impact test for <6mm.
Note 4: Smelting method: oxygen converter/electric furnace; delivery state: quenched + tempered.
Note 5: Q550D impact test temperature is -20℃ (KV2≥34J), reflecting excellent low-temperature toughness.
Note 6: Q550D requires Z-direction performance test for thickness ≥15mm (Z15/Z25/Z35 grade optional) to ensure resistance to lamellar tearing.

International Standard Approximate Comparison

According to GB/T 16270-2009 Appendix A (informative appendix) and official international standard data, the approximate equivalent grades of Q550D are as follows:

Property	Q550D (GB/T 16270-2009) China \| Quenched & Tempered	S550QL (EN 10025-6:2004) EU \| Quenched & Tempered	ASTM A514 Gr.S (ASTM A514) US \| Quenched & Tempered
Min Yield Strength (MPa)	550 (≤50mm)	550 (≤100mm)	690 (≤100mm)
Tensile Strength (MPa)	630~830	630~830	760~895
Min Elongation (%)	16	16	15
Impact Test Temperature (°C)	-20℃ (KV2≥34J)	-40℃ (KV≥40J)	-40℃ (KV≥27J)
Max Carbon Content (%)	0.20	0.20	0.21
Carbon Equivalent CEV ≤	0.50~0.55 (by thickness)	0.50	0.50
Max Thickness (mm)	150	150	100
Main Applications	Low-temperature engineering machinery, heavy structural components	Low-temperature high-rise structures, heavy cranes	Low-temperature heavy structural components

Note: The above is the approximate comparison of performance indicators, and the specific application shall be subject to the official standard of each country and the technical requirements of the project. CEHE Steel can provide products complying with Chinese, European and American standards according to customer requirements. Q550D is equivalent to S550QL in EN standard in terms of low-temperature performance.

Application Cases

Low-temperature Engineering Machinery

Excavator arms, crane booms, loader buckets and hydraulic support components used in cold regions (-20℃~-40℃). Q550D's high strength-to-weight ratio and excellent low-temperature toughness meet the load requirements of machinery in cold environments.

Cold Region Building Structures

Large-span bridge deck plates, high-rise building structural beams and columns in cold regions, steel structure workshops in low-temperature areas. Q550D's excellent low-temperature toughness and stability adapt to harsh outdoor environments (-20℃).

Cold Port Machinery

Port cranes, container handlers, ship unloaders and hoisting equipment in cold ports. Q550D's high load-bearing capacity, wear resistance and low-temperature toughness meet the long-term heavy-duty operation requirements in low-temperature environments.

Frequently Asked Questions

What are the core mechanical properties of Q550D high-strength steel plate? +

Q550D core mechanical properties (quenched + tempered state): 1. Yield strength (Rp0.2) ≥550MPa (for thickness ≤16mm, slightly decreased with thickness increase: 16-40mm≥530MPa, 40-63mm≥510MPa); 2. Tensile strength (Rm) 670-830MPa; 3. Elongation (A) ≥16%; 4. Low-temperature impact (KV2 at -20℃) ≥34J; 5. Carbon equivalent CEV ≤0.55% (for thickness ≤50mm) to ensure weldability; 6. Hardness ≤260HB to balance strength and machinability.

What are the typical application scenarios of Q550D steel plates? +

Q550D is widely used in high-strength structural fields requiring -20℃ low-temperature toughness: 1. Engineering machinery: crane booms, excavator arms, concrete pump trucks, heavy truck frames; 2. Construction machinery: high-rise building steel structures, bridge bearing structures, wind power tower flanges; 3. Special vehicles: armored vehicles, fire trucks, rescue vehicles, container frames; 4. Marine engineering: offshore platform auxiliary structures, port machinery, ship deck panels (non-main load-bearing); 5. Energy equipment: hydraulic support columns for coal mines, pressure vessel shells (low pressure).

What are the key welding process requirements for Q550D? +

Q550D welding key technical requirements: 1. Preheating temperature: 80~120℃ (thickness ≤30mm) / 120~150℃ (thickness >30mm) to prevent cold cracks; 2. Interpass temperature ≤220℃ to avoid grain coarsening; 3. Recommended welding materials: E9018-G (manual arc welding), ER90S-G (MIG/MAG welding), matching strength and low hydrogen content; 4. Heat input control: 1.5~2.5kJ/mm, low heat input to ensure toughness; 5. Post-weld treatment: stress relief annealing (580~620℃) is recommended for thick plates or complex structures, holding time 1~2h; 6. Welding inspection: 100% UT inspection for important welds to meet GB/T 11345 Level II.

What is the difference between Q550D and Q500D/Q690D high-strength steel plates? +

Core differences between Q550D and Q500D/Q690D: 1. Strength level: Q500D (yield ≥500MPa) < Q550D (yield ≥550MPa) < Q690D (yield ≥690MPa); 2. Chemical composition: Q550D has moderate alloy content (Mn, Si, Nb, V, Ti) between Q500D and Q690D, CEV 0.50~0.55%; 3. Toughness: All three grades require -20℃ impact KV2≥34J, but Q550D has better balance between strength and toughness; 4. Application: Q500D for medium load, Q550D for heavy load (without ultra-high strength), Q690D for extreme heavy load; 5. Weldability: Q550D is easier to weld than Q690D (lower preheating temperature), and has higher strength than Q500D; 6. Cost: Q500D < Q550D < Q690D (about 10-15% difference per grade).

What are the size range and customization services of Q550D steel plates? +

Q550D steel plate size range and customization: 1. Standard size: thickness 6~100mm, width 1500~4000mm, length 3000~18000mm; 2. Custom cutting: flame/plasma cutting to any shape (precision ±1mm), beveling (30~60°) for welding; 3. Performance customization: Z-direction performance (Z15/Z25/Z35) for thickness ≥15mm, impact energy upgrade (KV2≥40J), surface shot blasting (Sa2.5 grade); 4. Processing services: bending, rolling, drilling, anti-rust coating (epoxy primer 80μm); 5. Certification: MTC (EN 10204 3.1/3.2), third-party inspection (SGS/BV), ultrasonic testing (GB/T 2970); 6. Delivery: stock for common sizes (6-20mm thickness, 3-5 days), customized production (12-20 days) for thick plates (>20mm).

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