Se você está procurando um versátil, high-performance alloy steel for high-stress parts—like automotive gears or industrial shafts—JIS SCM440 alloy steel é uma escolha superior. Como uma liga de cromo-molibdênio padrão japonês, equilibra força excepcional, resistência, e temperabilidade. Este guia detalha tudo o que você precisa saber, desde sua composição química até histórias de sucesso do mundo real, to help you use it effectively.
1. Material Properties of JIS SCM440 Alloy Steel
JIS SCM440’s performance is rooted in its well-balanced properties, all compliant with Japan’sJIS G4105 padrão. Let’s explore each key aspect clearly.
1.1 Composição Química
The elements in JIS SCM440 work together to boost strength, durabilidade, e resistência ao calor. Below is the standard composition range:
| Elemento | Símbolo | Composition Range (%) | Key Role in the Alloy |
|---|---|---|---|
| Carbono (C) | C | 0.38 – 0.43 | Enhancesresistência à tracção and surface hardness; critical for wear-resistant parts |
| Cromo (Cr) | Cr | 0.90 – 1.20 | Melhoratemperabilidade eresistência à corrosão; prevents oxidation at moderate temperatures |
| Molybdenum (Mo) | Mo | 0.15 – 0.25 | Increasesresistência à fadiga e estabilidade de alta temperatura; reduces brittleness in thick parts |
| Manganês (Mn) | Mn | 0.60 – 0.85 | Impulsosusinabilidade and grain refinement; strengthens the alloy without losing ductility |
| Silício (E) | E | 0.15 – 0.35 | Acts as a deoxidizer during steelmaking; enhances overall strength |
| Níquel (Em) | Em | ≤ 0.25 | Minimizado; small amounts slightly improve toughness without increasing cost |
| Enxofre (S) | S | ≤ 0.030 | Kept low to avoid cracking and brittleness in high-stress applications |
| Fósforo (P) | P | ≤ 0.030 | Limited to prevent cold brittleness (fracture in low-temperature environments) |
| Vanadium (V) | V | ≤ 0.03 | Trace amounts; helps refine grain structure for uniform strength |
1.2 Propriedades Físicas
These traits determine how JIS SCM440 behaves in different working conditions—like temperature changes or magnetic fields:
- Densidade: 7.85 g/cm³ (consistent with most ferrous alloys, easy to integrate into existing designs)
- Ponto de fusão: 1430 – 1450°C (high enough for aplicações de alta temperatura like engine parts or industrial rollers)
- Condutividade térmica: 44 C/(m·K) a 20ºC (retains heat well, suitable for parts that operate continuously)
- Specific heat capacity: 470 J/(kg·K) a 20ºC (absorbs heat steadily, avoiding warping from sudden temperature swings)
- Thermal expansion coefficient: 12.1 μm/(m·K) (low expansion, critical for precision parts like gears or shafts)
- Magnetic properties: Ferromagnético (atrai ímãs, useful for tools like magnetic clamps or sensors)
1.3 Propriedades Mecânicas
JIS SCM440’s full mechanical strength is unlocked aftertêmpera + têmpera (its standard heat treatment). Below are typical values tested to Japanese standards:
| Propriedade | Valor típico | Test Standard (ELE) |
|---|---|---|
| Resistência à tracção | ≥ 1080 MPa | JIS Z2241 |
| Força de rendimento | ≥ 930 MPa | JIS Z2241 |
| Alongamento | ≥ 12% | JIS Z2241 |
| Reduction of area | ≥ 45% | JIS Z2241 |
| Dureza (Brinell) | 217 – 286 HB | JIS Z2243 |
| Dureza (Rockwell C.) | 22 – 30 CDH | JIS Z2245 |
| Dureza (Vickers) | 220 – 290 Alta tensão | JIS Z2244 |
| Resistência ao impacto | ≥ 60 J. | JIS Z2242 |
| Força de fadiga | ~540 MPa | JIS Z2273 |
1.4 Outras propriedades
- Resistência à corrosão: Moderado (resists mild moisture, óleos, and industrial chemicals; use zinc plating or paint for outdoor/humid environments)
- Resistência ao desgaste: Bom (graças a cromo (Cr) e tratamento térmico; suitable for moving parts like bearings or rollers)
- Usinabilidade: Justo (softer in annealed state; use high-speed steel (HSS) or carbide tools with cutting fluid to reduce tool wear)
- Weldability: Acceptable (preheat to 250 – 300°C and post-weld heat treat to avoid cracking; use low-hydrogen electrodes)
- Temperabilidade: Excelente (heat treatment penetrates deeply, ensuring uniform strength in thick parts like heavy machinery shafts)
2. Applications of JIS SCM440 Alloy Steel
JIS SCM440’s mix of strength, resistência, and versatility makes it ideal foraplicações de alto estresse em todos os setores. Aqui estão seus usos mais comuns, com exemplos do mundo real:
2.1 Indústria Automotiva
Cars, trucks, and commercial vehicles rely on its durability for critical parts:
- Eixos: A Japanese automaker uses it for drive shafts—its yield strength (≥930 MPa) handles 25-ton loads without bending.
- Engrenagens: A luxury car brand uses it for transmission gears; o resistência à fadiga (~540 MPa) extends gear life by 40% contra. aço carbono.
- Bolts and fasteners: High-performance sports cars use JIS SCM440 bolts for engine mounts—their resistência à tracção (≥1080 MPa) resist vibration loosening.
2.2 Mecânico & Máquinas Pesadas
Industrial machines need parts that last through continuous use:
- Rolamentos: A manufacturing plant uses it for conveyor belt bearings—its resistência ao desgaste cuts maintenance downtime by 25%.
- Molas: A construction equipment maker uses it for excavator arm springs; its elasticity (from tempering) withstands 10,000+ compression cycles.
- Rollers: Steel mills use it for rolling mill rollers; isso é dureza (217–286 HB) resists deformation from hot metal sheets.
2.3 Structural Components
For infrastructure and heavy-duty structures, it provides reliable strength:
- Crane shafts: Port cranes use it for hoist shafts—its impact toughness (≥60 J) prevents fracture when lifting 40-ton containers.
- Bridge fasteners: Large-span highways in Japan use JIS SCM440 bolts; with anti-rust coating, they stay stable outdoors for 10+ anos.
3. Manufacturing Techniques for JIS SCM440 Alloy Steel
To maximize JIS SCM440’s performance, follow these industry-proven manufacturing steps:
3.1 Steelmaking Processes
It’s typically produced using two methods:
- Forno Elétrico a Arco (EAF): Most common for medium batches. Scrap steel is melted with electrodes, então cromo (Cr) e molibdênio (Mo) are added to reach the target composition. EAF is flexible and reduces waste, ideal for custom parts like large shafts.
- Forno de oxigênio básico (BOF): Used for mass production. Molten iron is mixed with oxygen to remove impurities, then alloy elements are added. BOF is faster and cost-effective for standard parts like bolts.
3.2 Tratamento térmico
Heat treatment is critical to unlock JIS SCM440’s full potential. The standard process for high-stress parts is:
- Recozimento: Aqueça até 830 – 850°C, cool slowly. Softens the alloy for easier machining (cuts tool wear by 30%).
- Têmpera: Aqueça até 840 – 860°C, cool rapidly in oil. Hardens the steel to reach resistência à tracção ≥1080 MPa.
- Temperamento: Aqueça até 550 – 600°C, cool in air. Reduces brittleness while retaining strength—critical for parts like gears or shafts.
- Nitretação (optional): Aqueça até 500 – 550°C in a nitrogen-rich atmosphere. Adds a hard outer layer (0.1–0.3 mm thick) to boost resistência ao desgaste (ideal for bearings).
3.3 Forming Processes
JIS SCM440 is shaped into parts using:
- Forjamento: Hammered or pressed at 1100 – 1200°C. Aligns the metal’s grain structure, increasing resistência à tracção por 15% contra. cast parts. Used for gears, eixos, and crane components.
- Rolando: Passed through rollers to make bars, folhas, or rods. Used for basic shapes like bolt blanks or spring stock.
- Extrusão: Pushed through a die to make complex shapes (por exemplo, hollow shafts). Ideal for precision parts like automotive transmission components.
3.4 Machining Processes
After forming, parts are finished with precision machining:
- Virando: Uses a lathe to make cylindrical parts (por exemplo, eixos). Use cutting fluid (por exemplo, mineral oil) to prevent overheating and tool wear.
- Fresagem: Uses a rotating cutter to shape gear teeth or bearing races. Carbide tools work best for high precision (por exemplo, gear tooth tolerance ±0.02 mm).
- Perfuração: Creates holes for bolts or fasteners. High-speed drills (1000–1500 RPM) avoid cracking.
- Moagem: Smooths surfaces to tight tolerances (por exemplo, ±0.01 mm for bearing inner rings). Melhora resistência ao desgaste by reducing surface friction.
4. Estudo de caso: JIS SCM440 in Automotive Transmission Gears
A Japanese automotive factory faced a problem: their carbon steel transmission gears failed after 180,000 quilômetros, leading to costly recalls. They switched to JIS SCM440—and solved the issue.
4.1 Desafio
The factory’s compact cars were used in urban areas with frequent start-stop cycles. Carbon steel gears had lowresistência ao desgaste eresistência à fadiga (400 MPa), leading to tooth wear and transmission slippage. The failure rate was 6% per year, hurting brand reputation.
4.2 Solução
They switched to JIS SCM440 gears, usando:
- Forjamento (1150°C) to align grain structure and boost strength.
- Têmpera (850°C) + têmpera (580°C) to reach 950 MPa yield strength e 65 J. impact toughness.
- Precision grinding to smooth gear teeth, reduzindo o atrito e o desgaste.
4.3 Resultados
- Service life: Gears now last 360,000 km—double the previous lifespan.
- Economia de custos: Reduced recall costs by ¥300,000 per year.
- Desempenho: Transmission efficiency improved by 5%, reduzindo o consumo de combustível.
5. Comparative Analysis: JIS SCM440 vs. Outros materiais
How does JIS SCM440 stack up against common alternatives? Below is a side-by-side comparison of key traits:
| Material | Resistência à tracção | Resistência ao Impacto | Resistência à corrosão | Custo (contra. JIS SCM440) | Melhor para |
|---|---|---|---|---|---|
| JIS SCM440 | ≥1080 MPa | ≥60 J | Moderado | 100% (base) | Peças de alto estresse (engrenagens, eixos) |
| Aço inoxidável (SUS304) | 515 MPa | 60 J. | Excelente | 180% | Food/chemical equipment |
| Aço carbono (S45C) | 600 MPa | 35 J. | Baixo | 50% | Peças de baixo estresse (colchetes) |
| Liga de aço (SCM415) | 800 MPa | 50 J. | Moderado | 70% | General machinery parts |
| Titânio (Ti-6Al-4V) | 1100 MPa | 110 J. | Excelente | 800% | Peças aeroespaciais leves |
Key takeaway: JIS SCM440 has far betterresistência à tracção than carbon steel or SCM415, making it ideal for high-stress parts. It’s cheaper than stainless steel and titanium, making it the best value foralto desempenho, cost-sensitive applications.
Yigu Technology’s Perspective on JIS SCM440 Alloy Steel
Na tecnologia Yigu, JIS SCM440 is a staple for clients needing reliable, high-strength parts—especially in automotive and machinery sectors. We’ve supplied it for 12+ anos, and itstemperabilidade emolybdenum-enhanced fatigue strength consistently meet strict standards. We often recommend tempering at 550–600°C for optimal balance of strength and toughness, and anti-rust coatings for outdoor use. For manufacturers seeking a globally recognized alloy (compatible with AISI 4140) that balances performance and cost, JIS SCM440 is unmatched.
FAQ About JIS SCM440 Alloy Steel
1. Is JIS SCM440 the same as AISI 4140?
Yes—JIS SCM440 is nearly identical to AISI 4140 (American standard) in chemical composition and mechanical properties. They can be used interchangeably for most applications, making JIS SCM440 a great choice for global supply chains.
2. Can JIS SCM440 be used in high-temperature environments?
Yes—itsponto de fusão (1430–1450°C) emolibdênio (Mo) content let it perform reliably at temperatures up to 300°C. For higher temps (300–400ºC), adjust the tempering process (lower to 500–550°C) to boost heat stability.
3. How to improve JIS SCM440’s machinability?
Anneal the alloy first (heat to 830–850°C, cool slowly)—this softens it to 217–250 HB, making machining easier. Use carbide tools with cutting fluid (por exemplo, water-miscible coolant) and set cutting speed to 80–100 m/min to minimize tool wear.