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Q620MD STRUCTURAL STEEL (TMCP)

TMCP Delivery | Grade Q620MD | Yield 620MPa | Impact -20°C 47J | Cold Climate Ultra-High Strength Steel 🔍 Q620MD Grade Lookup →

Product Overview

Q620MD 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 620MPa (≤16mm), it delivers superior strength for cold climate heavy-duty engineering structures, cranes, mining equipment, and demanding infrastructure projects.

Equivalent grades: Q620MD ↔ Q620D (previous domestic grade), EN 10025-4 S620MC (Europe), ASTM A656 Grade 90 (USA).

International Grade Comparison

Europe (EN 10025-4)

S620MC

Impact: 0°C (40J)

Yield: 620MPa

C: ≤0.16%

Si: ≤0.60%

Mn: ≤2.00%

P: ≤0.025%

S: ≤0.020%

China (GB/T 1591)

Q620MD

Impact: -20°C (47J)

Yield: 620MPa

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.90

Impact: -20°C (optional)

Yield: 620MPa min

C: ≤0.18%

Si: ≤0.60%

Mn: ≤1.80%

P: ≤0.025%

S: ≤0.020%

Note: Q620MD is delivered in TMCP condition, offering refined grain structure and guaranteed impact toughness at -20°C. S620MC offers similar yield strength with 0°C impact (40J); ASTM A656 Grade 90 provides comparable strength (620MPa min) with optional -20°C impact.

China Grade Comparison: Q620D vs Q620MD

Q620D (Previous)

As-rolled / Normalized

Yield: 620MPa (≤16mm)

Impact -20°C: 47J (Longitudinal)

C: ≤0.20%

P: ≤0.025%

S: ≤0.020%

Delivery: As-rolled or normalized

Q620MD (TMCP)

TMCP

Yield: 620MPa (≤16mm)

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

C: ≤0.18% (lower carbon)

Mn: ≤2.00%

Cr: ≤1.00%

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

Key Advantages

Ultra-High Strength

Min yield 620MPa, tensile 710-880MPa (≤40mm).

-20°C Impact Toughness

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

Excellent Weldability

Optimized TMCP process, low carbon equivalent.

Applications

Heavy Machinery

Cranes, mining equipment, excavators, heavy-duty industrial machinery requiring ultra-high strength and -20°C toughness.

Engineering Structures

Bridge girders, transmission towers, offshore platforms, cold-region infrastructure requiring -20°C impact reliability.

Q620MD Chemical Composition

Chemical element composition of Chinese grade Q620MD low alloy high strength structural steel
Current manufacturing execution standard: GB/T 1591-2018

Grade Quality C ≤ Si ≤ Mn ≤ P ≤ S ≤
Q620M 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 1.00 0.80 0.80 0.30 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
620 610 600 580 — —

Tensile strength Rm (MPa)

≤40mm 40-63mm 63-80mm 80-100mm 100-120mm
710-880 690-880 670-860 — —

Elongation A% (min): 15%

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 >80mm, consult technical specifications.

Size & Specification

Product Thickness (mm) Width (mm) Length (mm)
Plate 3-80 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 Q620MD?

TMCP low-alloy high-strength steel per GB/T 1591-2018, min yield 620MPa, grade D guarantees impact 47J at -20°C (longitudinal).

Equivalent to S620MC?

Yes, comparable to EN 10025-4 S620MC and ASTM A656 Grade 90.

Difference Q620MD vs Q620D?

Q620MD features TMCP delivery for refined grain structure, superior weldability, and guaranteed -20°C impact with transverse requirements (27J).

Typical applications?

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