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S550QL High Strength Steel Plate

Q: What are the weldability characteristics of high-strength low-alloy steel plates?

High-strength low-alloy steel plates offer excellent weldability. As their carbon content is typically low (below 0.2%), they present a lower risk of cracking during welding compared to standard high-strength steel plates and generally do not require complex preheating treatments.

Q: Why are high-strength low-alloy steels the preferred choice in construction and automotive manufacturing?

The key advantage of high-strength low-alloy steels is weight reduction. As they offer greater strength, thinner sheets can be used to withstand the same loads, thereby reducing the overall weight of the structure; in the automotive sector, this leads to improved fuel efficiency.

Q: What is high-strength low-alloy steel (HSLA)?

High-strength low-alloy steel (HSLA) is a type of steel in which small amounts of alloying elements (such as niobium, vanadium, titanium or copper) are added to enhance its mechanical properties. Compared to traditional carbon steel, it offers higher yield strength and better corrosion resistance whilst maintaining good weldability and formability.

Home-Products-High-Strength Low-Alloy Steel Plate-EN 10025-6

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EN10025-6 S550QL is a premium, high-strength, quenched and tempered structural steel plate designed for demanding applications where maximum safety, light weight, and performance under extreme conditions are required.

Standard :
EN 10025-6
Grade :
S550QL
Thickness :
3 - 100 mm
Width :
1500 - 2500 mm
Length :
3000 - 12000 mm

Special thickness, width, and length can be negotiated separately.
We also provide customized processing services.If you have any questions, please contact us.

Overview

EN10025-6 S550QL High Strength Steel Plate is a high-quality, high-strength, quenched and tempered structural steel plate primarily used in structural engineering applications that require high steel strength, low-temperature toughness, and workability.

Grade	S550QL
Standard	EN 10025-6: Hot-rolled structural steels - Part 6: Technical delivery conditions for flat products of high yield strength structural steels in the quenched and tempered condition
Classification	Hot-rolled Structural Steel
Delivery Conditions	Quenched and Tempered(Q&T)
Approval By Third Party	ABS, DNV, GL, CCS, LR , RINA, KR, TUV, CE
Weldability	Good weldability, but strict process procedures (Pre-heating, Low Hydrogen Welding Materials, Post-Weld Heat Treatment, etc.) must still be followed during welding. The core risks are cold cracking (hydrogen-induced cracking) and toughness degradation in the heat-affected zone (HAZ).
Machinability	Cutting can be performed using laser, plasma, or flame cutting, but heat input must be controlled to avoid embrittlement in the heat-affected zone. The bending radius should be ≥3 times the plate thickness, and stress relief treatment is required after cold forming.
Surface Quality	Default is "As-Rolled" surface. Special requirements (such as coating pretreatment) must be specified in the order.
Inspection Requirements	Non-destructive testing (e.g., UT ultrasonic testing) and re-inspection of mechanical properties can be added as needed.

Chemical Composition

Grade	S550QL
Element	C	Si	Mn	P	S	N	B	Cr	Cu	Mo	Nb	Ni	Ti	V	Zr
Content (max, %)	0.200	0.800	1.700	0.025	0.015	0.015	0.005	1.500	0.500	0.700	0.060	2.000	0.050	0.120	0.150

* The chemical composition of EN 10025-6 S550QL High Strength Steel Plate is adjusted within a certain range depending on the thickness.

Carbon Equivalent of S550QL High Strength Steel Plate

Grade	Thickness (t) [mm]	CEV [max, %]
S550QL	t ≤ 30	0.47
	30 < t ≤ 40	0.48
	40 < t ≤ 50	0.49
	50 < t ≤ 60	0.50
	60 < t ≤ 100	0.51

* The carbon equivalent value varies depending on the thickness.For detailed information, please contact us for inquiries.

* Carbon equivalent (CEV) is calculated using the International Institute of Welding (IIW) formula: CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

Mechanical Properties

Grade	Thickness (t) [mm]	Yield Strength (ReH) [min, MPa]	Tensile Strength (Rm) [MPa]	Elongation (A) [min, %]	Impact Energy (KV) [min]
S550QL	3 ≤ t ≤ 50	550	640 - 820	16	30J (at -40°C, Longitudinal) 27J (at -40°C, Transverse)
	50 < t ≤ 100	530	640 - 820	16	30J (at -40°C, Longitudinal) 27J (at -40°C, Transverse)
	100 < t ≤ 150	490	590 - 770	16	30J (at -40°C, Longitudinal) 27J (at -40°C, Transverse)

* The mechanical properties of S550QL high-strength structural steel plate vary with thickness.

Applications

EN10025-6 S550QL high-strength steel plate is widely used in structural components subjected to heavy loads, impact, or low-temperature environments due to its combined advantages of "high strength, high toughness, and good weldability." Typical applications include:

Heavy machinery: Crane jibs, excavator chassis, and engineering vehicle frames.

Construction and bridges: Load-bearing components of long-span bridges and steel structural supports for high-rise buildings.

Special vehicles: Protective plates or load-bearing structures for mining vehicles and armored vehicles.

Pressure vessels and storage tanks: Large storage tanks designed to withstand high pressure and special pressure vessels (must additionally comply with pressure equipment standards).

Other Information

The Differences Between Grades Within The Same Series

Grade	Yield Strength (ReH) [min, MPa]	Tensile Strength (Rm) [MPa]	Elongation (A) [min, %]	Impact Energy (KV) [min]
S550Q	550	640 - 820	16%	30J (at -20°C)
S550QL	550	640 - 820	16%	30J (at -40°C)
S550QL1	550	640 - 820	16%	30J (at -60°C)

* The differences between S550Q, S550QL, and S550QL1 lie solely in the impact temperature requirements, while other mechanical properties remain consistent.

Equivalent Grades of EN 10025-6 S550QL High-strength Steel Plate

Standard	Grade	Yield Strength (MPa)	Impact Temperature (°C)	Delivery Condition	Equivalence Evaluation
EN 10025-6	S550QL	550	-40	Quenched & Tempered	Reference Grade
GB/T 16270 (China)	Q550E	550	-40	Quenched & Tempered	Fully equivalent, preferred in Chinese market
ASTM (USA)	A514 Grade Q	620–690	Negotiation	Quenched & Tempered	High-strength alternative, impact performance requires verification
JIS G3106 (Japan)	SM570	570	Room Temp. / -20	Hot Rolled / Normalized	Similar strength but fails low-temperature performance

* Grade equivalences are only approximate, actual mechanical properties and chemical composition should be compared.

FAQ

Q1:

What are the weldability characteristics of high-strength low-alloy steel plates?

High-strength low-alloy steel plates offer excellent weldability. As their carbon content is typically low (below 0.2%), they present a lower risk of cracking during welding compared to standard high-strength steel plates and generally do not require complex preheating treatments.

Q2:

Why are high-strength low-alloy steels the preferred choice in construction and automotive manufacturing?

The key advantage of high-strength low-alloy steels is weight reduction. As they offer greater strength, thinner sheets can be used to withstand the same loads, thereby reducing the overall weight of the structure; in the automotive sector, this leads to improved fuel efficiency.

Q3:

What is high-strength low-alloy steel (HSLA)?

High-strength low-alloy steel (HSLA) is a type of steel in which small amounts of alloying elements (such as niobium, vanadium, titanium or copper) are added to enhance its mechanical properties. Compared to traditional carbon steel, it offers higher yield strength and better corrosion resistance whilst maintaining good weldability and formability.