JIS SM490 Acciaio strutturale: La guida per ingegneri e costruttori

Se sei coinvolto nella costruzione di strutture ad alta resistenza come edifici alti o ponti pesanti, hai bisogno di un materiale di cui ti puoi fidare. L'acciaio strutturale JIS SM490 è la scelta migliore per tali progetti: offre una resistenza eccezionale pur rimanendo facile da lavorare. In questa guida, tratteremo tutto, dalle sue proprietà principali agli usi nel mondo reale, come è fatto, e come si confronta con altri acciai. Our aim is to help you decide if it’s the right fit for your next project.

1. Material Properties of JIS SM490 Structural Steel

To use JIS SM490 effectively, you first need to understand its proprietà del materiale. Let’s break down its composition and key mechanical traits.

Alloy Composition & Carbon Content

JIS SM490 is a low-alloy structural steel, designed for strength without sacrificing workability. Suo composizione della lega includes:

• Carbon Content: 0.18–0.23% (low enough for good weldability, but higher than mild steels like SS400)
• Manganese: 1.00–1.60% (aumenta resistenza meccanica e tenacità)
• Silicio: 0.15–0.35% (improves heat resistance during manufacturing)
• Fosforo: Max 0.035% (kept low to prevent brittleness)
• Zolfo: Max 0.035% (reduces the risk of cracking during welding)
• Rame: 0.20% massimo (adds slight corrosion resistance)

Resistenza meccanica & Key Metrics

What sets JIS SM490 apart is its impressive resistenza meccanica. Below is a table of its critical properties (tested at room temperature):

Other Important Properties

• Proprietà magnetiche: Like most structural steels, JIS SM490 is ferromagnetic. This makes it easy to test for cracks using magnetic particle inspection—a common quality check in construction.
• Toughness: Even at low temperatures (down to -10°C), it maintains good ductility, thanks to its alloy mix. This is crucial for outdoor structures in cooler climates.

2. Applications of JIS SM490 Structural Steel

JIS SM490’s high yield strength E resistenza alla trazione make it ideal for projects that need to handle heavy loads or harsh conditions. Let’s look at its most common applicazioni con esempi reali.

Construction and Infrastructure

Most JIS SM490 is used in demanding construction and infrastructure progetti:

• High-Rise Buildings: The steel’s strength allows for thinner columns and beams, freeing up space inside. Per esempio, the 48-story Lotte City Hotel in Busan, South Korea, used JIS SM490 for its core structural framework—this reduced the building’s overall weight by 15% compared to using mild steel.
• Bridges and Beams: Long-span bridges rely on JIS SM490’s ability to handle heavy traffic and environmental stress. The Incheon Bridge (a 12.3km sea-crossing bridge in South Korea) used over 10,000 tons of JIS SM490 for its main support beams, ensuring it could withstand strong winds and ship impacts.
• Industrial Buildings: Factories with heavy machinery (like automobile plants) use JIS SM490 for columns and girders. A Toyota manufacturing facility in Nagoya, Japan, used this steel to support overhead cranes that lift 50-ton parts—its high strength prevents bending or sagging.

General Engineering Use

Oltre la costruzione, JIS SM490 is used in:

• Heavy equipment frames (per esempio., bulldozers and cranes)
• Pressure vessels (for storing industrial gases)
• Railway bridges and train car frames (thanks to its vibration resistance)

3. Manufacturing Processes for JIS SM490 Structural Steel

JIS SM490’s strength comes from careful processi di produzione that balance performance and cost. Here’s how it’s made:

1. Hot Rolling: The primary process for JIS SM490. Steel billets are heated to 1,250°C (hotter than mild steels) and rolled into shapes like plates, travi, or bars. This process aligns the steel’s grain structure, boosting resistenza meccanica. Nippon Steel, a major producer, uses hot rolling for 90% of its JIS SM490 products.
2. Pickling: After rolling, the steel is dipped in hydrochloric acid to remove rust and scale. This step ensures a clean surface for welding or painting—critical for outdoor projects.
3. Ricottura: Some JIS SM490 products undergo ricottura (heating to 820°C and cooling slowly) per ridurre lo stress interno. This is common for steel used in precision parts, like pressure vessel components.
4. Saldatura: While JIS SM490 has a slightly higher carbon content than mild steel, it’s still weldable. Fabricators use low-hydrogen welding rods (like E8018-B2) per evitare rotture. Per esempio, a Chinese construction company welded 800 tons of JIS SM490 for a bridge project in 3 weeks—no pre-heating was needed for thin plates.
5. Trattamento termico: For extra strength, some JIS SM490 is quenched and tempered (heated, cooled quickly, then reheated). This process can raise its yield strength oltre 400 MPa, but it’s only used for high-demand projects like offshore platforms.

4. Standards and Specifications for JIS SM490 Structural Steel

JIS SM490 is governed by strict standards and specifications to ensure consistency across suppliers. Here’s what you need to know:

• Primary Standard: JIS G 3106 (Japanese Industrial Standard for Weldable Structural Steels). This standard defines the composizione della lega, resistenza meccanica (like minimum yield strength Di 325 MPa), and testing requirements for JIS SM490.
• International Equivalents: JIS SM490 is similar to other global high-strength steels, compreso:
• Grado ASTM A572 50 (NOI. standard)
• IN 10025 S355JR (European standard)
• GB/T 1591 Q345 (Chinese standard)
• Controllo qualità & Conformance Testing: To be certified as JIS SM490, steel must pass:
• Tensile tests (per verificare resistenza alla trazione E yield strength)
• Charpy impact tests (to check toughness at low temperatures)
• Analisi chimica (per confermare carbon content and alloy levels)
• Certificazione dei materiali: Reputable suppliers provide a Material Test Certificate (MTC) with every order. This document includes test results and a stamp from a JIS-accredited lab—always ask for it to ensure you’re getting genuine JIS SM490.

5. Comparison with Other Materials

How does JIS SM490 stack up against other structural steels? Below is a table comparing it to common alternatives:

When to Choose JIS SM490 Over Others

• If your project needs high strength (per esempio., grattacieli, ponti a lunga campata)
• If you’re working in Asia (easy to source locally, reducing shipping costs)
• If you need a balance of strength and weldability (better than ultra-high-strength steels)

Yigu Technology’s View on JIS SM490 Structural Steel

Alla tecnologia Yigu, we’ve supplied JIS SM490 to over 300 infrastructure projects across Asia. We see it as a “workhorse” for high-demand builds—its strength lets clients design slimmer, more efficient structures, while its weldability keeps construction on track. We often recommend it for clients moving from mild steel (like SS400) to stronger materials, as it requires minimal changes to existing fabrication processes. For coastal projects, we pair it with our zinc-rich coatings to boost corrosion resistance, extending service life by up to 20 anni. It’s a cost-effective choice for projects that can’t compromise on strength.

FAQ About JIS SM490 Structural Steel

1. Can JIS SM490 be used in cold climates?

SÌ, but check its grade. JIS SM490 has grades like SM490A (for warm climates) and SM490B (tested for -10°C). For temperatures below -20°C, choose SM490C or SM490D—these are tempered for better low-temperature toughness.

2. Is JIS SM490 more expensive than SS400?

SÌ, typically 15–20% more. But it’s worth it for projects needing higher strength—you’ll use less steel (since it’s stronger), which can offset the higher material cost. Per esempio, a bridge using SM490 may need 20% fewer beams than one using SS400.

3. What’s the maximum thickness for JIS SM490 plates?

Most suppliers offer JIS SM490 plates up to 100mm thick. For thicker plates (100–200 mm), you’ll need to order custom from mills like Nippon Steel or POSCO. Thicker plates may require pre-heating before welding to prevent cracking.