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Q550MD STRUCTURAL STEEL (TMCP)

TMCP Delivery | Grade Q550MD | Yield 550MPa | Impact -20°C 47J | Cold Climate Ultra-High Strength Steel 🔍 Q550MD Grade Lookup →

Product Overview

Q550MD is a Chinese grade low-alloy high-strength structural steel conforming to GB/T 1591-2018 standard. Delivered in thermomechanically rolled (TMCP) condition, it offers refined grain structure, excellent weldability, and guaranteed low-temperature toughness. The quality grade D provides impact properties at -20°C (longitudinal min. 47J, transverse min. 27J). With minimum yield strength of 550MPa (≤16mm), it delivers superior strength for cold climate engineering structures, heavy machinery, mining equipment, and demanding infrastructure projects.

Equivalent grades: Q550MD ↔ Q550D (previous domestic grade), EN 10025-4 S550MC (Europe), ASTM A656 Grade 80 (USA).

International Grade Comparison（EN vs GB vs ASTM）

Europe (EN 10025-4)

S550MC

Impact: 0°C (40J)

Yield: 550MPa

C: ≤0.16%

Si: ≤0.60%

Mn: ≤2.00%

P: ≤0.025%

S: ≤0.020%

China (GB/T 1591)

Q550MD

Impact: -20°C (47J)

Yield: 550MPa

C: ≤0.18%

Si: ≤0.60%

Mn: ≤2.00%

P: ≤0.030%

S: ≤0.025%

TMCP Delivery | Grade D -20°C Impact

USA (ASTM A656)

Gr.80

Impact: -20°C (optional)

Yield: 550MPa min

C: ≤0.18%

Si: ≤0.60%

Mn: ≤1.80%

P: ≤0.025%

S: ≤0.020%

Note: Q550MD is delivered in TMCP condition, offering refined grain structure and guaranteed impact toughness at -20°C. S550MC offers similar yield strength with 0°C impact (40J); ASTM A656 Grade 80 provides comparable strength (550MPa min) with optional -20°C impact.

China Grade Comparison: Q550D vs Q550MD

Q550D (Previous)

As-rolled / Normalized

Yield: 550MPa (≤16mm)

Impact -20°C: 47J (Longitudinal)

C: ≤0.20%

P: ≤0.025%

S: ≤0.020%

Delivery: As-rolled or normalized

Q550MD (TMCP)

TMCP

Yield: 550MPa (≤16mm)

Impact -20°C: 47J (Longitudinal) / 27J (Transverse)

C: ≤0.18% (lower carbon)

Mn: ≤2.00%

Delivery: TMCP, refined grain, superior weldability, guaranteed -20°C toughness

Key Advantages

Ultra-High Strength

Min yield 550MPa, tensile 670-830MPa (≤40mm).

-20°C Impact Toughness

Guaranteed KV2 47J at -20°C (Longitudinal).

Excellent Weldability

Optimized TMCP process, low carbon equivalent.

Applications

Heavy Structures

High-rise buildings, stadiums, industrial plants, cold-region construction requiring -20°C impact reliability.

Engineering & Mining

Bridge girders, cranes, mining equipment, transmission towers, offshore platforms, heavy machinery in cold environments.

Q550MD Chemical Composition

Chemical element composition of Chinese grade Q550MD low alloy high strength structural steel
Current manufacturing execution standard: GB/T 1591-2018

Grade Quality C ≤ Si ≤ Mn ≤ P ≤ S ≤
Q550M D 0.18 0.60 2.00 0.030 0.025
Nb V Ti Cr ≤ Ni ≤ Cu ≤ Mo ≤ N ≤ B ≤ Als ≥
0.01-0.11 0.01-0.12 0.006-0.05 0.8 0.8 0.8 0.3 0.025 0.004 0.015

Notes: The steel shall contain at least one grain-refining element (Al, Nb, V, Ti) with content not less than lower limit. All-aluminum (Alt) min 0.02% if substituted. For structural steel and bars, P/S can increase by 0.005%. Ti can be as high as 0.2%.

Mechanical Properties

Upper yield strength ReH (MPa, min)

≤16mm 16-40mm 40-63mm 63-80mm 80-100mm 100-120mm
550 540 530 510 500 —

Tensile strength Rm (MPa)

≤40mm 40-63mm 63-80mm 80-100mm 100-120mm
670-830 620-810 600-790 590-780 —

Elongation A% (min): 16%

Impact KV2 (J) min – Quality D (-20°C)

Direction -20°C
Longitudinal 47
Transverse 27
Note: Thermomechanically rolled (TMCP) condition includes TMCP + tempered condition. If yield not obvious, use Rp0.2. For thickness >100mm, consult technical specifications.

Size & Specification

Product Thickness (mm) Width (mm) Length (mm)
Plate 3-100 1000-4000 3000-18000
Sheet/Coil 1.5-20 900-2000 Coil or cut length

Custom sizes and cutting available upon request.

Customizable Options

Laser/plasma cutting, edge beveling, shot blasting, priming, third-party inspection, custom marking.

Quality Assurance

Full Testing
Spectral analysis, tensile & impact, ultrasonic
MTC 3.1/3.2
Full traceability & EN10204 docs

Packaging & Logistics

Bundled with steel straps, waterproof wrapping, clear marking. FOB, CIF, CFR from major Chinese ports. Lead time: 25-35 days.

Request a Quote

Direct email: customize@cehesteel.com – reply within 2 hours.

Frequently Asked Questions

What is Q550MD?

TMCP low-alloy high-strength steel per GB/T 1591-2018, min yield 550MPa, grade D guarantees impact 47J at -20°C (longitudinal).

Equivalent to S550MC?

Yes, comparable to EN 10025-4 S550MC and ASTM A656 Grade 80.

Difference Q550MD vs Q550D?

Q550MD features TMCP delivery for refined grain structure, superior weldability, and guaranteed -20°C impact with transverse requirements (27J).

Typical applications?

Heavy engineering structures (cranes, mining equipment, bridges), cold-region infrastructure, high-rise buildings requiring ultra-high strength and -20°C toughness.