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HI 350 Steel Plate | High Tensile Steel

Carbon Steel ST52, S355, and ST37 by Riyaarth Overseas

In structural fabrication where strength-to-weight ratio and durability are key, HI 350 steel plate is widely specified as a dependable high tensile material. Known in the market as a ~350 MPa yield strength steel, it is commonly used across infrastructure, heavy engineering, and fabrication industries requiring reliable load-bearing performance.

HI 350 is not a formal international standard but a trade-recognized designation used to indicate high-strength carbon steel plates comparable to SAILMA 350 HI, IS 2062 E350C, and S355J2. These materials offer a balanced combination of strength, weldability, and impact resistance, making them suitable for demanding structural applications.

With improved tensile properties over conventional mild steel, HI 350 plates enable designers to achieve lighter structures without compromising strength, which is especially beneficial in large-scale fabrication and transport-sensitive projects.

Mechanical Properties

PropertyValueUnit
Yield Strength (min.)~350MPa
Tensile Strength470 – 630MPa
Elongation20 – 24%
Hardness140 – 190HB
Density7.85g/cm³
Modulus of Elasticity200GPa

Note: Values may vary depending on the equivalent standard and mill source.

Chemical Composition

ElementTypical Range (%)
Carbon (C)≤ 0.20
Manganese (Mn)1.0 – 1.6
Silicon (Si)0.15 – 0.50
Phosphorus (P)≤ 0.035
Sulfur (S)≤ 0.035

Low carbon content improves weldability, while manganese enhances strength and toughness.

 

Equivalent Grades

HI 350 is generally supplied as an equivalent to the following recognized standards:

  • SAILMA 350 HI
  • IS 2062 E350C
  • S355J2

Material can be offered in SAIL make or equivalent grades from reputed mills based on availability.

Applications

HI 350 steel plates are used in structural and heavy-duty fabrication environments:

  1. Infrastructure Projects — Bridges, flyovers, and large structural frameworks
  2. Material Handling Equipment — Cranes, conveyors, and lifting systems
  3. Heavy Fabrication — Industrial structures, base frames, and support systems
  4. Mining & Construction Equipment — Load-bearing and wear-resistant components
  5. Transport & Railways — Wagons, chassis, and structural assemblies

Weldability & Processing

  • Weldability: HI 350 plates offer good weldability due to controlled carbon levels.
    Thin plates: No preheat typically required
    Medium thickness: 50–100 °C preheat recommended
    Thick sections: Controlled welding procedure required
  • Formability: Suitable for:
    Bending
    Rolling
    Cutting and shaping
    Its ductility allows fabrication into complex geometries without significant risk of cracking.
  • Heat Treatment: Generally supplied in as-rolled or normalized condition depending on application. Normalizing enhances uniformity and impact toughness.

HI 350 vs Mild Steel — Key Differences

Property HI 350 Steel Mild Steel (IS 2062 E250)
Yield Strength ~350 MPa ~250 MPa
Tensile Strength Higher Lower
Weight Efficiency Better Lower
Applications Heavy structures General fabrication
Cost Efficiency Higher performance Lower cost

Quality Assurance

  • Mechanical Testing: Plates are tested for yield strength, tensile strength, and elongation as per applicable standards.
  • Dimensional Tolerances: Supplied as per IS / ASTM tolerances for thickness, flatness, and width.
  • Mill Certification: Material test certificates (MTC) provided with traceability to the supplying mill.

FAQs

What is HI 350 steel plate?

HI 350 steel plate is a high tensile structural carbon steel with a minimum yield strength of approximately 350 MPa. It is widely used in heavy fabrication and structural applications. It is a market-recognized designation rather than a formal standard and is typically supplied as an equivalent to E350 or S355 grades. Buyers should confirm the exact standard in the mill test certificate.

Is HI 350 the same as SAILMA 350 HI?

HI 350 is often used as a generic term for steels equivalent to SAILMA 350 HI, but they are not identical by definition. SAILMA is a proprietary grade manufactured by SAIL. Equivalent materials from other mills may match mechanical properties but may differ slightly in chemistry and certification. Always verify origin if project specifications require SAIL make material.

What are the applications of HI 350 plates?

HI 350 plates are used in infrastructure, heavy engineering, mining equipment, and fabrication industries. They are ideal for load-bearing structures requiring higher strength. Their improved strength-to-weight ratio makes them suitable for large-scale projects where reducing structural weight is important without compromising durability.

Is HI 350 steel plate weldable?

Yes, HI 350 steel plates have good weldability due to controlled carbon content and balanced composition. Standard welding processes can be applied. For thicker sections, preheating and controlled welding parameters are recommended to avoid cracking and ensure joint integrity.

Is HI 350 suitable for export or international projects?

Yes, HI 350 equivalent plates can be supplied in internationally recognized grades like S355J2 or E350C for export purposes. Export documentation typically includes mill test certificates and compliance with EN or ASTM standards as required by the project specifications.

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