Q420MB Structural Steel

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Q420MB STRUCTURAL STEEL (TMCP)

TMCP Delivery | Grade Q420MB | Yield 420MPa | Impact 20°C 34J | High-Strength Structural Steel 🔍 Q420MB Grade Lookup →

Product Overview

Q420MB 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 toughness. The quality grade B provides impact properties at 20°C (longitudinal min. 34J). With minimum yield strength of 420MPa (≤16mm), it provides higher strength than Q355 and Q390 series and is widely used in bridges, high-rise buildings, and engineering structures requiring enhanced load-bearing capacity.

Equivalent grades: Q420MB ↔ Q420B (previous domestic grade), EN 10025-4 S420M (Europe), ASTM A572 Grade 60 (USA).

International Grade Comparison (TMCP / Thermomechanical Rolling)

Europe (EN 10025-4)

S420M

Impact: -20°C (40J)

Yield: 420MPa (≤16mm)

C: ≤0.14%

Si: ≤0.50%

Mn: ≤1.60%

P: ≤0.025%

S: ≤0.020%

Nb+V+Ti: ≤0.22%

Delivery: TMCP

China (GB/T 1591)

Q420MB

Impact: 20°C (34J)

Yield: 420MPa

C: ≤0.16%

Si: ≤0.50%

Mn: ≤1.70%

P: ≤0.035%

S: ≤0.035%

Nb: 0.01-0.05%

V: 0.01-0.12%

Ti: 0.006-0.05%

Delivery: TMCP, grade B 20°C impact

USA (ASTM A572)

Gr.60

Impact: Not specified

Yield: 415MPa min

C: ≤0.26%

Si: ≤0.40%

Mn: ≤1.35%

P: ≤0.025%

S: ≤0.025%

Nb+V: ≤0.15%

Cu: ≤0.60%

Note: Q420MB is delivered in TMCP condition, offering refined grain structure and consistent mechanical properties. S420M offers similar yield strength (420MPa) with -20°C impact; ASTM A572 Gr.60 provides comparable strength (415MPa) with optional impact requirements.

China Grade Comparison: Q420B vs Q420MB (TMCP)

Q420B (Previous)

As-rolled / Normalized

Yield: 420MPa (≤16mm)

Impact 20°C: 34J

C: ≤0.20%

Delivery: As-rolled or normalized

Q420MB (TMCP)

TMCP (Thermomechanical Rolling)

Yield: 420MPa (≤16mm)

Impact 20°C: 34J

C: ≤0.16% (lower carbon)

Delivery: TMCP, refined grain, superior weldability

Key Advantages (TMCP Technology)

High Strength

Min yield 420MPa (≤16mm), tensile 520-680MPa.

TMCP Grain Refinement

Controlled rolling & accelerated cooling ensures fine grain structure.

Excellent Weldability

Low carbon equivalent due to optimized TMCP process.

Applications

Building Structures

High-rise buildings, stadiums, industrial plants, pre-engineered steel buildings requiring higher strength.

Engineering Structures

Bridge girders, transmission towers, heavy machinery foundations, infrastructure projects.

Q420MB Chemical Composition (GB/T 1591-2018, TMCP)

Chemical element composition of Chinese grade Q420MB low alloy high strength structural steel

Current manufacturing execution standard: GB/T 1591-2018
Q420MB Approximate Grade Lookup Table

Grade Quality C ≤ Si ≤ Mn ≤ P ≤ S ≤
Q420M B 0.16ᵈ 0.50 1.70 0.035 0.035
Nb V Ti Cr ≤ Ni ≤ Cu ≤ Mo ≤ N ≤ B Als ≥
0.01-0.05 0.01-0.12 0.006-0.05 0.3 0.8 0.4 0.2 0.015 — 0.015

Notes: a. For structural steel and bars, P/S can increase by 0.005%. b. Ti can be as high as 0.2%. c. All-aluminum (Alt) min 0.02% if substituted; grain-refining elements rule applies. d. For structural steel and bars, max carbon content can be increased by 0.02%.

The steel shall contain at least one grain-refining element (Al, Nb, V, Ti) with content not less than lower limit.

Q420MB Mechanical Properties (TMCP, GB/T 1591-2018)

Upper yield strength ReH (MPa, min)

≤16mm 16-40mm 40-63mm 63-80mm 80-100mm 100-120mm
420 400 390 380 370 365

Tensile strength Rm (MPa)

≤40mm 40-63mm 63-80mm 80-100mm 100-120mm
520-680 500-660 480-640 470-630 460-620

Elongation A% (min): 19% (across all thickness ranges)

Impact KV2 (J) min – Quality B (20°C)

Direction 20°C
Longitudinal 34
Transverse 27
Note: Thermomechanically rolled (TMCP) condition includes TMCP + tempered condition. If yield not obvious, use Rp0.2. For thickness >120mm, consult technical specifications.

Size & Specification

Product Thickness (mm) Width (mm) Length (mm)
Plate 3-120 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 Q420MB?

Thermomechanically rolled (TMCP) low-alloy high-strength steel per GB/T 1591-2018, min yield 420MPa, grade B guarantees impact 34J at 20°C.

Equivalent to S420M?

Yes, Q420MB is comparable to EN 10025-4 S420M and ASTM A572 Grade 60. S420M offers similar yield with -20°C impact.

Difference Q420MB vs Q420B?

Q420MB features lower carbon content (≤0.16% vs ≤0.20%), TMCP delivery ensures refined grain structure, better weldability, and consistent properties.

Typical applications?

Engineering structures (bridges, towers) and building structures (high-rise, industrial buildings) requiring higher strength.